Merge branch 'develop' into shay/batch_state_groups

author: H. Shay <hillerys@element.io> 2022-10-20 14:22:21 -0700
committer: H. Shay <hillerys@element.io> 2022-10-20 14:22:21 -0700
commit: 63f8ee4007e736be8f9c8666f534cc3e867bbf2f (patch)
tree: e2aa4481f7a331bbdd26f4bbebee97dfc5feb35f
parent: add version of eventcontext without state group (diff)
parent: Use servlets for /key/ endpoints. (#14229) (diff)
download: synapse-63f8ee4007e736be8f9c8666f534cc3e867bbf2f.tar.xz
176 files changed, 3097 insertions, 1423 deletions
diff --git a/.ci/scripts/calculate_jobs.py b/.ci/scripts/calculate_jobs.py
index b1f604eeb0..c2198e0dd4 100755
--- a/.ci/scripts/calculate_jobs.py
+++ b/.ci/scripts/calculate_jobs.py
@@ -18,6 +18,13 @@
 import json
 import os
 
+
+def set_output(key: str, value: str):
+    # See https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#setting-an-output-parameter
+    with open(os.environ["GITHUB_OUTPUT"], "at") as f:
+        print(f"{key}={value}", file=f)
+
+
 IS_PR = os.environ["GITHUB_REF"].startswith("refs/pull/")
 
 # First calculate the various trial jobs.
@@ -81,7 +88,7 @@ print("::endgroup::")
 test_matrix = json.dumps(
     trial_sqlite_tests + trial_postgres_tests + trial_no_extra_tests
 )
-print(f"::set-output name=trial_test_matrix::{test_matrix}")
+set_output("trial_test_matrix", test_matrix)
 
 
 # First calculate the various sytest jobs.
@@ -125,4 +132,4 @@ print(json.dumps(sytest_tests, indent=4))
 print("::endgroup::")
 
 test_matrix = json.dumps(sytest_tests)
-print(f"::set-output name=sytest_test_matrix::{test_matrix}")
+set_output("sytest_test_matrix", test_matrix)
diff --git a/.ci/scripts/setup_complement_prerequisites.sh b/.ci/scripts/setup_complement_prerequisites.sh
index 4848901cbf..42ef654167 100755
--- a/.ci/scripts/setup_complement_prerequisites.sh
+++ b/.ci/scripts/setup_complement_prerequisites.sh
@@ -21,7 +21,7 @@ endblock
 
 block Install Complement Dependencies
   sudo apt-get -qq update && sudo apt-get install -qqy libolm3 libolm-dev
-  go get -v github.com/haveyoudebuggedit/gotestfmt/v2/cmd/gotestfmt@latest
+  go get -v github.com/gotesttools/gotestfmt/v2/cmd/gotestfmt@latest
 endblock
 
 block Install custom gotestfmt template
diff --git a/.dockerignore b/.dockerignore
index 1c6905b1bb..0b51345cbd 100644
--- a/.dockerignore
+++ b/.dockerignore
@@ -9,6 +9,7 @@
 !pyproject.toml
 !poetry.lock
 !Cargo.lock
+!Cargo.toml
 !build_rust.py
 
 rust/target
diff --git a/.flake8 b/.flake8
index acb118c86e..4c6a4d5843 100644
--- a/.flake8
+++ b/.flake8
@@ -8,4 +8,11 @@
 #  E203: whitespace before ':' (which is contrary to pep8?)
 #  E731: do not assign a lambda expression, use a def
 #  E501: Line too long (black enforces this for us)
-ignore=W503,W504,E203,E731,E501
+#
+# flake8-bugbear runs extra checks. Its error codes are described at
+# https://github.com/PyCQA/flake8-bugbear#list-of-warnings
+#  B019: Use of functools.lru_cache or functools.cache on methods can lead to memory leaks
+#  B023: Functions defined inside a loop must not use variables redefined in the loop
+#  B024: Abstract base class with no abstract method.
+
+ignore=W503,W504,E203,E731,E501,B019,B023,B024
diff --git a/.github/dependabot.yml b/.github/dependabot.yml
index 9c7db1fc86..9ee62bf539 100644
--- a/.github/dependabot.yml
+++ b/.github/dependabot.yml
@@ -15,3 +15,8 @@ updates:
     directory: "/"
     schedule:
       interval: "weekly"
+
+  - package-ecosystem: "cargo"
+    directory: "/"
+    schedule:
+      interval: "weekly"
diff --git a/.github/workflows/docker.yml b/.github/workflows/docker.yml
index b3793e5c1f..49427ab50d 100644
--- a/.github/workflows/docker.yml
+++ b/.github/workflows/docker.yml
@@ -27,7 +27,7 @@ jobs:
 
       - name: Inspect builder
         run: docker buildx inspect
-          
+
       - name: Log in to DockerHub
         uses: docker/login-action@v2
         with:
@@ -55,3 +55,8 @@ jobs:
           tags: "${{ steps.set-tag.outputs.tags }}"
           file: "docker/Dockerfile"
           platforms: linux/amd64,linux/arm64
+
+          # arm64 builds OOM without the git fetch setting. c.f.
+          # https://github.com/rust-lang/cargo/issues/10583
+          build-args: |
+            CARGO_NET_GIT_FETCH_WITH_CLI=true
diff --git a/.github/workflows/docs.yaml b/.github/workflows/docs.yaml
index 17b9df601c..798e308f20 100644
--- a/.github/workflows/docs.yaml
+++ b/.github/workflows/docs.yaml
@@ -54,7 +54,7 @@ jobs:
           esac
 
           # finally, set the 'branch-version' var.
-          echo "::set-output name=branch-version::$branch"
+          echo "branch-version=$branch" >> "$GITHUB_OUTPUT"
           
       # Deploy to the target directory.
       - name: Deploy to gh pages
diff --git a/.github/workflows/release-artifacts.yml b/.github/workflows/release-artifacts.yml
index 1c004fbc11..60db6ad7f0 100644
--- a/.github/workflows/release-artifacts.yml
+++ b/.github/workflows/release-artifacts.yml
@@ -27,6 +27,8 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - uses: actions/setup-python@v4
+        with:
+          python-version: '3.x'
       - id: set-distros
         run: |
           # if we're running from a tag, get the full list of distros; otherwise just use debian:sid
@@ -34,7 +36,7 @@ jobs:
           if [[ $GITHUB_REF == refs/tags/* ]]; then
               dists=$(scripts-dev/build_debian_packages.py --show-dists-json)
           fi
-          echo "::set-output name=distros::$dists"
+          echo "distros=$dists" >> "$GITHUB_OUTPUT"
     # map the step outputs to job outputs
     outputs:
       distros: ${{ steps.set-distros.outputs.distros }}
@@ -70,6 +72,8 @@ jobs:
 
       - name: Set up python
         uses: actions/setup-python@v4
+        with:
+          python-version: '3.x'
 
       - name: Build the packages
         # see https://github.com/docker/build-push-action/issues/252
@@ -91,11 +95,14 @@ jobs:
           path: debs/*
 
   build-wheels:
-    name: Build wheels on ${{ matrix.os }}
+    name: Build wheels on ${{ matrix.os }} for ${{ matrix.arch }}
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
         os: [ubuntu-20.04, macos-10.15]
+        arch: [x86_64, aarch64]
+        # is_pr is a flag used to exclude certain jobs from the matrix on PRs.
+        # It is not read by the rest of the workflow.
         is_pr:
           - ${{ startsWith(github.ref, 'refs/pull/') }}
 
@@ -103,6 +110,12 @@ jobs:
           # Don't build macos wheels on PR CI.
           - is_pr: true
             os: "macos-10.15"
+          # Don't build aarch64 wheels on mac.
+          - os: "macos-10.15"
+            arch: aarch64
+          # Don't build aarch64 wheels on PR CI.
+          - is_pr: true
+            arch: aarch64
 
     steps:
       - uses: actions/checkout@v3
@@ -116,11 +129,19 @@ jobs:
       - name: Install cibuildwheel
         run: python -m pip install cibuildwheel==2.9.0 poetry==1.2.0
 
-      # Only build a single wheel in CI.
-      - name: Set env vars.
-        run: |
-          echo "CIBW_BUILD="cp37-manylinux_x86_64"" >> $GITHUB_ENV
+      - name: Set up QEMU to emulate aarch64
+        if: matrix.arch == 'aarch64'
+        uses: docker/setup-qemu-action@v2
+        with:
+          platforms: arm64
+
+      - name: Build aarch64 wheels
+        if: matrix.arch == 'aarch64'
+        run: echo 'CIBW_ARCHS_LINUX=aarch64' >> $GITHUB_ENV
+
+      - name: Only build a single wheel on PR
         if: startsWith(github.ref, 'refs/pull/')
+        run: echo "CIBW_BUILD="cp37-manylinux_${{ matrix.arch }}"" >> $GITHUB_ENV
 
       - name: Build wheels
         run: python -m cibuildwheel --output-dir wheelhouse
@@ -128,6 +149,9 @@ jobs:
           # Skip testing for platforms which various libraries don't have wheels
           # for, and so need extra build deps.
           CIBW_TEST_SKIP: pp39-* *i686* *musl* pp37-macosx*
+          # Fix Rust OOM errors on emulated aarch64: https://github.com/rust-lang/cargo/issues/10583
+          CARGO_NET_GIT_FETCH_WITH_CLI: true
+          CIBW_ENVIRONMENT_PASS_LINUX: CARGO_NET_GIT_FETCH_WITH_CLI
 
       - uses: actions/upload-artifact@v3
         with:
diff --git a/.github/workflows/triage-incoming.yml b/.github/workflows/triage-incoming.yml
index f926bcb759..0f0397cf5b 100644
--- a/.github/workflows/triage-incoming.yml
+++ b/.github/workflows/triage-incoming.yml
@@ -5,24 +5,11 @@ on:
     types: [ opened ]
 
 jobs:
-  add_new_issues:
-    name: Add new issues to the triage board
-    runs-on: ubuntu-latest
-    steps:
-      - uses: octokit/graphql-action@v2.x
-        id: add_to_project
-        with:
-          headers: '{"GraphQL-Features": "projects_next_graphql"}'
-          query: |
-              mutation add_to_project($projectid:ID!,$contentid:ID!) {
-                addProjectV2ItemById(input: {projectId: $projectid contentId: $contentid}) {
-                item {
-                  id
-                  }
-                }
-              }
-          projectid: ${{ env.PROJECT_ID }}
-          contentid: ${{ github.event.issue.node_id }}
-        env:
-          PROJECT_ID: "PVT_kwDOAIB0Bs4AFDdZ"
-          GITHUB_TOKEN: ${{ secrets.ELEMENT_BOT_TOKEN }}
+  triage:
+    uses: matrix-org/backend-meta/.github/workflows/triage-incoming.yml@v1
+    with: 
+      project_id: 'PVT_kwDOAIB0Bs4AFDdZ'
+      content_id: ${{ github.event.issue.node_id }}
+    secrets: 
+      github_access_token: ${{ secrets.ELEMENT_BOT_TOKEN }}
+          
diff --git a/CHANGES.md b/CHANGES.md
index 862524f208..da7213cb68 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,11 +1,145 @@
-Synapse 1.69.0rc2 (2022-10-06)
+Synapse 1.70.0rc1 (2022-10-19)
 ==============================
 
+Features
+--------
+
+- Support for [MSC3856](https://github.com/matrix-org/matrix-spec-proposals/pull/3856): threads list API. ([\#13394](https://github.com/matrix-org/synapse/issues/13394), [\#14171](https://github.com/matrix-org/synapse/issues/14171), [\#14175](https://github.com/matrix-org/synapse/issues/14175))
+- Support for thread-specific notifications & receipts ([MSC3771](https://github.com/matrix-org/matrix-spec-proposals/pull/3771) and [MSC3773](https://github.com/matrix-org/matrix-spec-proposals/pull/3773)). ([\#13776](https://github.com/matrix-org/synapse/issues/13776), [\#13824](https://github.com/matrix-org/synapse/issues/13824), [\#13877](https://github.com/matrix-org/synapse/issues/13877), [\#13878](https://github.com/matrix-org/synapse/issues/13878), [\#14050](https://github.com/matrix-org/synapse/issues/14050), [\#14140](https://github.com/matrix-org/synapse/issues/14140), [\#14159](https://github.com/matrix-org/synapse/issues/14159), [\#14163](https://github.com/matrix-org/synapse/issues/14163), [\#14174](https://github.com/matrix-org/synapse/issues/14174), [\#14222](https://github.com/matrix-org/synapse/issues/14222))
+- Stop fetching missing `prev_events` after we already know their signature is invalid. ([\#13816](https://github.com/matrix-org/synapse/issues/13816))
+- Send application service access tokens as a header (and query parameter). Implements [MSC2832](https://github.com/matrix-org/matrix-spec-proposals/pull/2832). ([\#13996](https://github.com/matrix-org/synapse/issues/13996))
+- Ignore server ACL changes when generating pushes. Implements [MSC3786](https://github.com/matrix-org/matrix-spec-proposals/pull/3786). ([\#13997](https://github.com/matrix-org/synapse/issues/13997))
+- Experimental support for redirecting to an implementation of a [MSC3886](https://github.com/matrix-org/matrix-spec-proposals/pull/3886) HTTP rendezvous service. ([\#14018](https://github.com/matrix-org/synapse/issues/14018))
+- The `/relations` endpoint can now be used on workers. ([\#14028](https://github.com/matrix-org/synapse/issues/14028))
+- Advertise support for Matrix 1.3 and 1.4 on `/_matrix/client/versions`. ([\#14032](https://github.com/matrix-org/synapse/issues/14032), [\#14184](https://github.com/matrix-org/synapse/issues/14184))
+- Improve validation of request bodies for the [Device Management](https://spec.matrix.org/v1.4/client-server-api/#device-management) and [MSC2697 Device Dehyrdation](https://github.com/matrix-org/matrix-spec-proposals/pull/2697) client-server API endpoints. ([\#14054](https://github.com/matrix-org/synapse/issues/14054))
+- Experimental support for [MSC3874](https://github.com/matrix-org/matrix-spec-proposals/pull/3874). ([\#14148](https://github.com/matrix-org/synapse/issues/14148))
+- Improve the validation of the following PUT endpoints: [`/directory/room/{roomAlias}`](https://spec.matrix.org/v1.4/client-server-api/#put_matrixclientv3directoryroomroomalias), [`/directory/list/room/{roomId}`](https://spec.matrix.org/v1.4/client-server-api/#put_matrixclientv3directorylistroomroomid) and [`/directory/list/appservice/{networkId}/{roomId}`](https://spec.matrix.org/v1.4/application-service-api/#put_matrixclientv3directorylistappservicenetworkidroomid). ([\#14179](https://github.com/matrix-org/synapse/issues/14179))
+- Build and publish binary wheels for `aarch64` platforms. ([\#14212](https://github.com/matrix-org/synapse/issues/14212))
+
+
+Bugfixes
+--------
+
+- Prevent device names from appearing in device list updates when `allow_device_name_lookup_over_federation` is `false`. ([\#10015](https://github.com/matrix-org/synapse/issues/10015))
+- Fix a long-standing bug where redactions were not being sent over federation if we did not have the original event. ([\#13813](https://github.com/matrix-org/synapse/issues/13813))
+- Fix a long-standing bug where edits of non-`m.room.message` events would not be correctly bundled or have their new content applied. ([\#14034](https://github.com/matrix-org/synapse/issues/14034))
+- Fix a bug introduced in Synapse 1.53.0 when querying `/publicRooms` with both a `room_type` filter and a `third_party_instance_id`. ([\#14053](https://github.com/matrix-org/synapse/issues/14053))
+- Fix a bug introduced in Synapse 1.35.0 where errors parsing a `/send_join` or `/state` response would produce excessive, low-quality Sentry events. ([\#14065](https://github.com/matrix-org/synapse/issues/14065))
+- Fix a long-standing bug where Synapse would error on the optional 'invite_room_state' field not being provided to [`PUT /_matrix/federation/v2/invite/{roomId}/{eventId}`](https://spec.matrix.org/v1.4/server-server-api/#put_matrixfederationv2inviteroomideventid). ([\#14083](https://github.com/matrix-org/synapse/issues/14083))
+- Fix a bug where invalid oEmbed fields would cause the entire response to be discarded. Introduced in Synapse 1.18.0. ([\#14089](https://github.com/matrix-org/synapse/issues/14089))
+- Fix a bug introduced in Synapse 1.37.0 in which an incorrect key name was used for sending and receiving room metadata when knocking on a room. ([\#14102](https://github.com/matrix-org/synapse/issues/14102))
+- Fix a bug introduced in v1.69.0rc1 where the joined hosts for a given event were not being properly cached. ([\#14125](https://github.com/matrix-org/synapse/issues/14125))
+- Fix a bug introduced in Synapse 1.30.0 where purging and rejoining a room without restarting in-between would result in a broken room. ([\#14161](https://github.com/matrix-org/synapse/issues/14161), [\#14164](https://github.com/matrix-org/synapse/issues/14164))
+- Fix [MSC3030](https://github.com/matrix-org/matrix-spec-proposals/pull/3030) `/timestamp_to_event` endpoint returning potentially inaccurate closest events with `outliers` present. ([\#14215](https://github.com/matrix-org/synapse/issues/14215))
+
+
+Updates to the Docker image
+---------------------------
+
+- Update the version of frozendict in Docker images and Debian packages from 2.3.3 to 2.3.4, which may fix memory leak problems. ([\#13955](https://github.com/matrix-org/synapse/issues/13955))
+- Use the `minimal` Rust profile when building Synapse. ([\#14141](https://github.com/matrix-org/synapse/issues/14141))
+- Prevent a class of database sharding errors when using `Dockerfile-workers` to spawn multiple instances of the same worker. Contributed by Jason Little. ([\#14165](https://github.com/matrix-org/synapse/issues/14165))
+- Set `LD_PRELOAD` to use jemalloc memory allocator in Dockerfile-workers. ([\#14182](https://github.com/matrix-org/synapse/issues/14182))
+- Fix pre-startup logging being lost when using the `Dockerfile-workers` image. ([\#14195](https://github.com/matrix-org/synapse/issues/14195))
+
+
+Improved Documentation
+----------------------
+
+- Add sample worker files for `pusher` and `federation_sender`. ([\#14077](https://github.com/matrix-org/synapse/issues/14077))
+- Improve the listener example on the metrics documentation. ([\#14078](https://github.com/matrix-org/synapse/issues/14078))
+- Expand Google OpenID Connect example config to map email attribute. Contributed by @ptman. ([\#14081](https://github.com/matrix-org/synapse/issues/14081))
+- The changelog entry ending in a full stop or exclamation mark is not optional. ([\#14087](https://github.com/matrix-org/synapse/issues/14087))
+- Fix links to jemalloc documentation, which were broken in [#13491](https://github.com/matrix-org/synapse/pull/14124). ([\#14093](https://github.com/matrix-org/synapse/issues/14093))
+- Remove not needed `replication` listener in docker compose example. ([\#14107](https://github.com/matrix-org/synapse/issues/14107))
+- Fix name of `alias_creation_rules` option in the config manual documentation. ([\#14124](https://github.com/matrix-org/synapse/issues/14124))
+- Clarify comment on event contexts. ([\#14145](https://github.com/matrix-org/synapse/issues/14145))
+- Fix dead link to the [Admin Registration API](https://matrix-org.github.io/synapse/latest/admin_api/register_api.html). ([\#14189](https://github.com/matrix-org/synapse/issues/14189))
+
+
+Deprecations and Removals
+-------------------------
+
+- Remove the experimental implementation of [MSC3772](https://github.com/matrix-org/matrix-spec-proposals/pull/3772). ([\#14094](https://github.com/matrix-org/synapse/issues/14094))
+- Remove the unstable identifier for [MSC3715](https://github.com/matrix-org/matrix-doc/pull/3715). ([\#14106](https://github.com/matrix-org/synapse/issues/14106), [\#14146](https://github.com/matrix-org/synapse/issues/14146))
+
+
+Internal Changes
+----------------
+
+- Optimise queries used to get a users rooms during sync. Contributed by Nick @ Beeper (@fizzadar). ([\#13991](https://github.com/matrix-org/synapse/issues/13991))
+- Update authlib from 0.15.5 to 1.1.0. ([\#14006](https://github.com/matrix-org/synapse/issues/14006))
+- Make `parse_server_name` consistent in handling invalid server names. ([\#14007](https://github.com/matrix-org/synapse/issues/14007))
+- Don't repeatedly wake up the same users for batched events. ([\#14033](https://github.com/matrix-org/synapse/issues/14033))
+- Complement test image: capture logs from nginx. ([\#14063](https://github.com/matrix-org/synapse/issues/14063))
+- Don't create noisy Sentry events when a requester drops connection to the metrics server mid-request. ([\#14072](https://github.com/matrix-org/synapse/issues/14072))
+- Run the integration test suites with the asyncio reactor enabled in CI. ([\#14092](https://github.com/matrix-org/synapse/issues/14092))
+- Add debug logs to figure out why an event was filtered out of the client response. ([\#14095](https://github.com/matrix-org/synapse/issues/14095))
+- Indicate what endpoint came back with a JSON response we were unable to parse. ([\#14097](https://github.com/matrix-org/synapse/issues/14097))
+- Break up calls to fetch rooms for many users. Contributed by Nick @ Beeper (@fizzadar). ([\#14109](https://github.com/matrix-org/synapse/issues/14109))
+- Faster joins: prioritise the server we joined by when restarting a partial join resync. ([\#14126](https://github.com/matrix-org/synapse/issues/14126))
+- Cache Rust build cache when building docker images. ([\#14130](https://github.com/matrix-org/synapse/issues/14130))
+- Enable dependabot for Rust dependencies. ([\#14132](https://github.com/matrix-org/synapse/issues/14132))
+- Bump typing-extensions from 4.1.1 to 4.4.0. ([\#14134](https://github.com/matrix-org/synapse/issues/14134))
+- Use the `minimal` Rust profile when building Synapse. ([\#14141](https://github.com/matrix-org/synapse/issues/14141))
+- Remove unused configuration code. ([\#14142](https://github.com/matrix-org/synapse/issues/14142))
+- Prepare for the [`gotestfmt` repository move](https://github.com/GoTestTools/gotestfmt/discussions/46). ([\#14144](https://github.com/matrix-org/synapse/issues/14144))
+- Invalidate rooms for user caches on replicated event, fix sync cache race in synapse workers. Contributed by Nick @ Beeper (@fizzadar). ([\#14155](https://github.com/matrix-org/synapse/issues/14155))
+- Enable url previews when testing with complement. ([\#14198](https://github.com/matrix-org/synapse/issues/14198))
+- When authenticating batched events, check for auth events in batch as well as DB. ([\#14214](https://github.com/matrix-org/synapse/issues/14214))
+- Update CI config to avoid GitHub Actions deprecation warnings. ([\#14216](https://github.com/matrix-org/synapse/issues/14216), [\#14224](https://github.com/matrix-org/synapse/issues/14224))
+- Update dependency requirements to allow building with poetry-core 1.3.2. ([\#14217](https://github.com/matrix-org/synapse/issues/14217))
+- Rename the `cache_memory` extra to `cache-memory`, for compatability with poetry-core 1.3.0 and [PEP 685](https://peps.python.org/pep-0685/). From-source installations using this extra will need to install using the new name. ([\#14221](https://github.com/matrix-org/synapse/issues/14221))
+- Specify dev-dependencies using lower bounds, to reduce the likelihood of a dependabot merge conflict. The lockfile continues to pin to specific versions. ([\#14227](https://github.com/matrix-org/synapse/issues/14227))
+
+
+Synapse 1.69.0 (2022-10-17)
+===========================
+
 Please note that legacy Prometheus metric names are now deprecated and will be removed in Synapse 1.73.0.
 Server administrators should update their dashboards and alerting rules to avoid using the deprecated metric names.
 See the [upgrade notes](https://matrix-org.github.io/synapse/v1.69/upgrade.html#upgrading-to-v1690) for more details.
 
 
+No significant changes since 1.69.0rc4.
+
+
+Synapse 1.69.0rc4 (2022-10-14)
+==============================
+
+Bugfixes
+--------
+
+- Fix poor performance of the `event_push_backfill_thread_id` background update, which was introduced in Synapse 1.68.0rc1. ([\#14172](https://github.com/matrix-org/synapse/issues/14172), [\#14181](https://github.com/matrix-org/synapse/issues/14181))
+
+
+Updates to the Docker image
+---------------------------
+
+- Fix docker build OOMing in CI for arm64 builds. ([\#14173](https://github.com/matrix-org/synapse/issues/14173))
+
+
+Synapse 1.69.0rc3 (2022-10-12)
+==============================
+
+Bugfixes
+--------
+
+- Fix an issue with Docker images causing the Rust dependencies to not be pinned correctly. Introduced in v1.68.0 ([\#14129](https://github.com/matrix-org/synapse/issues/14129))
+- Fix a bug introduced in Synapse 1.69.0rc1 which would cause registration replication requests to fail if the worker sending the request is not running Synapse 1.69. ([\#14135](https://github.com/matrix-org/synapse/issues/14135))
+- Fix error in background update when rotating existing notifications. Introduced in v1.69.0rc2. ([\#14138](https://github.com/matrix-org/synapse/issues/14138))
+
+
+Internal Changes
+----------------
+
+- Rename the `url_preview` extra to `url-preview`, for compatability with poetry-core 1.3.0 and [PEP 685](https://peps.python.org/pep-0685/). From-source installations using this extra will need to install using the new name. ([\#14085](https://github.com/matrix-org/synapse/issues/14085))
+
+
+Synapse 1.69.0rc2 (2022-10-06)
+==============================
+
 Deprecations and Removals
 -------------------------
 
diff --git a/Cargo.lock b/Cargo.lock
index b952b6b4c0..b3090ad726 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -104,9 +104,9 @@ checksum = "adab1eaa3408fb7f0c777a73e7465fd5656136fc93b670eb6df3c88c2c1344e3"
 
 [[package]]
 name = "itoa"
-version = "1.0.3"
+version = "1.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6c8af84674fe1f223a982c933a0ee1086ac4d4052aa0fb8060c12c6ad838e754"
+checksum = "4217ad341ebadf8d8e724e264f13e593e0648f5b3e94b3896a5df283be015ecc"
 
 [[package]]
 name = "lazy_static"
@@ -116,15 +116,15 @@ checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
 
 [[package]]
 name = "libc"
-version = "0.2.132"
+version = "0.2.135"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8371e4e5341c3a96db127eb2465ac681ced4c433e01dd0e938adbef26ba93ba5"
+checksum = "68783febc7782c6c5cb401fbda4de5a9898be1762314da0bb2c10ced61f18b0c"
 
 [[package]]
 name = "lock_api"
-version = "0.4.7"
+version = "0.4.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "327fa5b6a6940e4699ec49a9beae1ea4845c6bab9314e4f84ac68742139d8c53"
+checksum = "435011366fe56583b16cf956f9df0095b405b82d76425bc8981c0e22e60ec4df"
 dependencies = [
  "autocfg",
  "scopeguard",
@@ -156,9 +156,9 @@ dependencies = [
 
 [[package]]
 name = "once_cell"
-version = "1.13.1"
+version = "1.15.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "074864da206b4973b84eb91683020dbefd6a8c3f0f38e054d93954e891935e4e"
+checksum = "e82dad04139b71a90c080c8463fe0dc7902db5192d939bd0950f074d014339e1"
 
 [[package]]
 name = "parking_lot"
@@ -185,18 +185,18 @@ dependencies = [
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.43"
+version = "1.0.46"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0a2ca2c61bc9f3d74d2886294ab7b9853abd9c1ad903a3ac7815c58989bb7bab"
+checksum = "94e2ef8dbfc347b10c094890f778ee2e36ca9bb4262e86dc99cd217e35f3470b"
 dependencies = [
  "unicode-ident",
 ]
 
 [[package]]
 name = "pyo3"
-version = "0.17.1"
+version = "0.17.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "12f72538a0230791398a0986a6518ebd88abc3fded89007b506ed072acc831e1"
+checksum = "201b6887e5576bf2f945fe65172c1fcbf3fcf285b23e4d71eb171d9736e38d32"
 dependencies = [
  "anyhow",
  "cfg-if",
@@ -212,9 +212,9 @@ dependencies = [
 
 [[package]]
 name = "pyo3-build-config"
-version = "0.17.1"
+version = "0.17.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fc4cf18c20f4f09995f3554e6bcf9b09bd5e4d6b67c562fdfaafa644526ba479"
+checksum = "bf0708c9ed01692635cbf056e286008e5a2927ab1a5e48cdd3aeb1ba5a6fef47"
 dependencies = [
  "once_cell",
  "target-lexicon",
@@ -222,9 +222,9 @@ dependencies = [
 
 [[package]]
 name = "pyo3-ffi"
-version = "0.17.1"
+version = "0.17.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a41877f28d8ebd600b6aa21a17b40c3b0fc4dfe73a27b6e81ab3d895e401b0e9"
+checksum = "90352dea4f486932b72ddf776264d293f85b79a1d214de1d023927b41461132d"
 dependencies = [
  "libc",
  "pyo3-build-config",
@@ -243,9 +243,9 @@ dependencies = [
 
 [[package]]
 name = "pyo3-macros"
-version = "0.17.1"
+version = "0.17.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2e81c8d4bcc2f216dc1b665412df35e46d12ee8d3d046b381aad05f1fcf30547"
+checksum = "7eb24b804a2d9e88bfcc480a5a6dd76f006c1e3edaf064e8250423336e2cd79d"
 dependencies = [
  "proc-macro2",
  "pyo3-macros-backend",
@@ -255,9 +255,9 @@ dependencies = [
 
 [[package]]
 name = "pyo3-macros-backend"
-version = "0.17.1"
+version = "0.17.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "85752a767ee19399a78272cc2ab625cd7d373b2e112b4b13db28de71fa892784"
+checksum = "f22bb49f6a7348c253d7ac67a6875f2dc65f36c2ae64a82c381d528972bea6d6"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -343,9 +343,9 @@ dependencies = [
 
 [[package]]
 name = "serde_json"
-version = "1.0.85"
+version = "1.0.86"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e55a28e3aaef9d5ce0506d0a14dbba8054ddc7e499ef522dd8b26859ec9d4a44"
+checksum = "41feea4228a6f1cd09ec7a3593a682276702cd67b5273544757dae23c096f074"
 dependencies = [
  "itoa",
  "ryu",
@@ -354,9 +354,9 @@ dependencies = [
 
 [[package]]
 name = "smallvec"
-version = "1.9.0"
+version = "1.10.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2fd0db749597d91ff862fd1d55ea87f7855a744a8425a64695b6fca237d1dad1"
+checksum = "a507befe795404456341dfab10cef66ead4c041f62b8b11bbb92bffe5d0953e0"
 
 [[package]]
 name = "subtle"
@@ -366,9 +366,9 @@ checksum = "6bdef32e8150c2a081110b42772ffe7d7c9032b606bc226c8260fd97e0976601"
 
 [[package]]
 name = "syn"
-version = "1.0.99"
+version = "1.0.102"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "58dbef6ec655055e20b86b15a8cc6d439cca19b667537ac6a1369572d151ab13"
+checksum = "3fcd952facd492f9be3ef0d0b7032a6e442ee9b361d4acc2b1d0c4aaa5f613a1"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -406,9 +406,9 @@ checksum = "dcf81ac59edc17cc8697ff311e8f5ef2d99fcbd9817b34cec66f90b6c3dfd987"
 
 [[package]]
 name = "unicode-ident"
-version = "1.0.3"
+version = "1.0.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c4f5b37a154999a8f3f98cc23a628d850e154479cd94decf3414696e12e31aaf"
+checksum = "6ceab39d59e4c9499d4e5a8ee0e2735b891bb7308ac83dfb4e80cad195c9f6f3"
 
 [[package]]
 name = "unindent"
diff --git a/changelog.d/13422.bugfix b/changelog.d/13422.bugfix
new file mode 100644
index 0000000000..3a099acbe6
--- /dev/null
+++ b/changelog.d/13422.bugfix
@@ -0,0 +1 @@
+Fix a long-standing bug where the `update_synapse_database` script could not be run with multiple databases. Contributed by @thefinn93 @ Beeper.
\ No newline at end of file
diff --git a/changelog.d/13776.feature b/changelog.d/13776.feature
deleted file mode 100644
index 5d0ae16e13..0000000000
--- a/changelog.d/13776.feature
+++ /dev/null
@@ -1 +0,0 @@
-Support for thread-specific notifications & receipts ([MSC3771](https://github.com/matrix-org/matrix-spec-proposals/pull/3771) and [MSC3773](https://github.com/matrix-org/matrix-spec-proposals/pull/3773)).
diff --git a/changelog.d/13824.feature b/changelog.d/13824.feature
deleted file mode 100644
index 5d0ae16e13..0000000000
--- a/changelog.d/13824.feature
+++ /dev/null
@@ -1 +0,0 @@
-Support for thread-specific notifications & receipts ([MSC3771](https://github.com/matrix-org/matrix-spec-proposals/pull/3771) and [MSC3773](https://github.com/matrix-org/matrix-spec-proposals/pull/3773)).
diff --git a/changelog.d/13877.feature b/changelog.d/13877.feature
deleted file mode 100644
index 5d0ae16e13..0000000000
--- a/changelog.d/13877.feature
+++ /dev/null
@@ -1 +0,0 @@
-Support for thread-specific notifications & receipts ([MSC3771](https://github.com/matrix-org/matrix-spec-proposals/pull/3771) and [MSC3773](https://github.com/matrix-org/matrix-spec-proposals/pull/3773)).
diff --git a/changelog.d/13878.feature b/changelog.d/13878.feature
deleted file mode 100644
index 5d0ae16e13..0000000000
--- a/changelog.d/13878.feature
+++ /dev/null
@@ -1 +0,0 @@
-Support for thread-specific notifications & receipts ([MSC3771](https://github.com/matrix-org/matrix-spec-proposals/pull/3771) and [MSC3773](https://github.com/matrix-org/matrix-spec-proposals/pull/3773)).
diff --git a/changelog.d/13955.docker b/changelog.d/13955.docker
deleted file mode 100644
index 043b5690a3..0000000000
--- a/changelog.d/13955.docker
+++ /dev/null
@@ -1 +0,0 @@
-Update the version of frozendict in Docker images and Debian packages from 2.3.3 to 2.3.4, which may fix memory leak problems.
diff --git a/changelog.d/13983.misc b/changelog.d/13983.misc
deleted file mode 100644
index 69ed75be90..0000000000
--- a/changelog.d/13983.misc
+++ /dev/null
@@ -1 +0,0 @@
-Bump actions/setup-python from 2 to 4.
diff --git a/changelog.d/13984.misc b/changelog.d/13984.misc
deleted file mode 100644
index 120d042fad..0000000000
--- a/changelog.d/13984.misc
+++ /dev/null
@@ -1 +0,0 @@
-Bump types-pyopenssl from 22.0.0 to 22.0.10.
diff --git a/changelog.d/13985.misc b/changelog.d/13985.misc
deleted file mode 100644
index 48e8960720..0000000000
--- a/changelog.d/13985.misc
+++ /dev/null
@@ -1 +0,0 @@
-Bump jsonschema from 4.4.0 to 4.16.0.
diff --git a/changelog.d/13986.misc b/changelog.d/13986.misc
deleted file mode 100644
index f71aed474b..0000000000
--- a/changelog.d/13986.misc
+++ /dev/null
@@ -1 +0,0 @@
-Bump types-setuptools from 57.4.9 to 65.4.0.0.
diff --git a/changelog.d/13987.misc b/changelog.d/13987.misc
deleted file mode 100644
index b1164201be..0000000000
--- a/changelog.d/13987.misc
+++ /dev/null
@@ -1 +0,0 @@
-Bump types-requests from 2.27.11 to 2.28.11.
diff --git a/changelog.d/13988.misc b/changelog.d/13988.misc
deleted file mode 100644
index e8c6b4e9b1..0000000000
--- a/changelog.d/13988.misc
+++ /dev/null
@@ -1 +0,0 @@
-Bump isort from 5.7.0 to 5.10.1.
diff --git a/changelog.d/13991.misc b/changelog.d/13991.misc
deleted file mode 100644
index f425fb17b2..0000000000
--- a/changelog.d/13991.misc
+++ /dev/null
@@ -1 +0,0 @@
-Optimise queries used to get a users rooms during sync. Contributed by Nick @ Beeper (@fizzadar).
diff --git a/changelog.d/13996.feature b/changelog.d/13996.feature
deleted file mode 100644
index 771f1c97a3..0000000000
--- a/changelog.d/13996.feature
+++ /dev/null
@@ -1 +0,0 @@
-Send application service access tokens as a header (and query parameter). Implement [MSC2832](https://github.com/matrix-org/matrix-spec-proposals/pull/2832).
diff --git a/changelog.d/13997.feature b/changelog.d/13997.feature
deleted file mode 100644
index 23f7ed106f..0000000000
--- a/changelog.d/13997.feature
+++ /dev/null
@@ -1 +0,0 @@
-Ignore server ACL changes when generating pushes. Implement [MSC3786](https://github.com/matrix-org/matrix-spec-proposals/pull/3786).
diff --git a/changelog.d/14006.misc b/changelog.d/14006.misc
deleted file mode 100644
index c06dcadf02..0000000000
--- a/changelog.d/14006.misc
+++ /dev/null
@@ -1 +0,0 @@
-Update authlib from 0.15.5 to 1.1.0.
diff --git a/changelog.d/14032.feature b/changelog.d/14032.feature
deleted file mode 100644
index bb221d3ca6..0000000000
--- a/changelog.d/14032.feature
+++ /dev/null
@@ -1 +0,0 @@
-Advertise Matrix 1.3 support on `/_matrix/client/versions`.
diff --git a/changelog.d/14033.misc b/changelog.d/14033.misc
deleted file mode 100644
index fe42852aa5..0000000000
--- a/changelog.d/14033.misc
+++ /dev/null
@@ -1 +0,0 @@
-Don't repeatedly wake up the same users for batched events.
\ No newline at end of file
diff --git a/changelog.d/14034.bugfix b/changelog.d/14034.bugfix
deleted file mode 100644
index e437ef3a01..0000000000
--- a/changelog.d/14034.bugfix
+++ /dev/null
@@ -1 +0,0 @@
-Fix a long-standing bug where edits of non-`m.room.message` events would not be correctly bundled or have their new content applied.
diff --git a/changelog.d/14040.misc b/changelog.d/14040.misc
deleted file mode 100644
index 1a4d3146b5..0000000000
--- a/changelog.d/14040.misc
+++ /dev/null
@@ -1 +0,0 @@
-Bump msgpack from 1.0.3 to 1.0.4.
diff --git a/changelog.d/14041.misc b/changelog.d/14041.misc
deleted file mode 100644
index a2119627f8..0000000000
--- a/changelog.d/14041.misc
+++ /dev/null
@@ -1 +0,0 @@
-Bump types-pyyaml from 6.0.4 to 6.0.12.
diff --git a/changelog.d/14042.misc b/changelog.d/14042.misc
new file mode 100644
index 0000000000..868d55e76a
--- /dev/null
+++ b/changelog.d/14042.misc
@@ -0,0 +1 @@
+Bump flake8-bugbear from 21.3.2 to 22.9.23.
diff --git a/changelog.d/14043.misc b/changelog.d/14043.misc
deleted file mode 100644
index 102dc5c773..0000000000
--- a/changelog.d/14043.misc
+++ /dev/null
@@ -1 +0,0 @@
-Bump phonenumbers from 8.12.44 to 8.12.56.
diff --git a/changelog.d/14044.misc b/changelog.d/14044.misc
deleted file mode 100644
index 0909739a25..0000000000
--- a/changelog.d/14044.misc
+++ /dev/null
@@ -1 +0,0 @@
-Bump pydantic from 1.9.1 to 1.10.2.
diff --git a/changelog.d/14046.misc b/changelog.d/14046.misc
deleted file mode 100644
index 69ed75be90..0000000000
--- a/changelog.d/14046.misc
+++ /dev/null
@@ -1 +0,0 @@
-Bump actions/setup-python from 2 to 4.
diff --git a/changelog.d/14050.feature b/changelog.d/14050.feature
deleted file mode 100644
index 5d0ae16e13..0000000000
--- a/changelog.d/14050.feature
+++ /dev/null
@@ -1 +0,0 @@
-Support for thread-specific notifications & receipts ([MSC3771](https://github.com/matrix-org/matrix-spec-proposals/pull/3771) and [MSC3773](https://github.com/matrix-org/matrix-spec-proposals/pull/3773)).
diff --git a/changelog.d/14053.bugfix b/changelog.d/14053.bugfix
deleted file mode 100644
index 07769f51d0..0000000000
--- a/changelog.d/14053.bugfix
+++ /dev/null
@@ -1 +0,0 @@
-Fix a bug introduced in Synapse 1.53.0 when querying `/publicRooms` with both a `room_type` filter and a `third_party_instance_id`.
diff --git a/changelog.d/14054.feature b/changelog.d/14054.feature
deleted file mode 100644
index 9cf3f7a557..0000000000
--- a/changelog.d/14054.feature
+++ /dev/null
@@ -1 +0,0 @@
-Improve validation of request bodies for the [Device Management](https://spec.matrix.org/v1.4/client-server-api/#device-management) and [MSC2697 Device Dehyrdation](https://github.com/matrix-org/matrix-spec-proposals/pull/2697) client-server API endpoints.
diff --git a/changelog.d/14063.misc b/changelog.d/14063.misc
deleted file mode 100644
index f0d1e47f1a..0000000000
--- a/changelog.d/14063.misc
+++ /dev/null
@@ -1 +0,0 @@
-Complement test image: capture logs from nginx.
diff --git a/changelog.d/14064.bugfix b/changelog.d/14064.bugfix
new file mode 100644
index 0000000000..cce6ef3b71
--- /dev/null
+++ b/changelog.d/14064.bugfix
@@ -0,0 +1 @@
+ Fix a long-standing bug where Synapse would accidentally include extra information in the response to [`PUT /_matrix/federation/v2/invite/{roomId}/{eventId}`](https://spec.matrix.org/v1.4/server-server-api/#put_matrixfederationv2inviteroomideventid).
\ No newline at end of file
diff --git a/changelog.d/14065.misc b/changelog.d/14065.misc
deleted file mode 100644
index 98998b0015..0000000000
--- a/changelog.d/14065.misc
+++ /dev/null
@@ -1 +0,0 @@
-Fix a bug introduced in Synapse 1.35.0 where errors parsing a `/send_join` or `/state` response would produce excessive, low-quality Sentry events.
diff --git a/changelog.d/14072.misc b/changelog.d/14072.misc
deleted file mode 100644
index 3070c756d5..0000000000
--- a/changelog.d/14072.misc
+++ /dev/null
@@ -1 +0,0 @@
-Don't create noisy Sentry events when a requester drops connection to the metrics server mid-request.
diff --git a/changelog.d/14077.doc b/changelog.d/14077.doc
deleted file mode 100644
index 7853e7cd5e..0000000000
--- a/changelog.d/14077.doc
+++ /dev/null
@@ -1 +0,0 @@
-Add sample worker files for `pusher` and `federation_sender`.
diff --git a/changelog.d/14078.doc b/changelog.d/14078.doc
deleted file mode 100644
index cbe3c8b381..0000000000
--- a/changelog.d/14078.doc
+++ /dev/null
@@ -1 +0,0 @@
-Improve the listener example on the metrics documentation.
diff --git a/changelog.d/14081.doc b/changelog.d/14081.doc
deleted file mode 100644
index 0a6925b3bf..0000000000
--- a/changelog.d/14081.doc
+++ /dev/null
@@ -1 +0,0 @@
-Expand Google OpenID Connect example config to map email attribute. Contributed by @ptman.
diff --git a/changelog.d/14087.doc b/changelog.d/14087.doc
deleted file mode 100644
index 28d1ce67c5..0000000000
--- a/changelog.d/14087.doc
+++ /dev/null
@@ -1 +0,0 @@
-The changelog entry ending in a full stop or exclamation mark is not optional.
diff --git a/changelog.d/14089.bugfix b/changelog.d/14089.bugfix
deleted file mode 100644
index 4a398921bb..0000000000
--- a/changelog.d/14089.bugfix
+++ /dev/null
@@ -1 +0,0 @@
-Fix a bug where invalid oEmbed fields would cause the entire response to be discarded. Introduced in Synapse 1.18.0.
diff --git a/changelog.d/14092.misc b/changelog.d/14092.misc
deleted file mode 100644
index c48f40cd38..0000000000
--- a/changelog.d/14092.misc
+++ /dev/null
@@ -1 +0,0 @@
-Run the integration test suites with the asyncio reactor enabled in CI.
diff --git a/changelog.d/14093.doc b/changelog.d/14093.doc
deleted file mode 100644
index cb1ff9490e..0000000000
--- a/changelog.d/14093.doc
+++ /dev/null
@@ -1 +0,0 @@
-Fix links to jemalloc documentation, which were broken in #13491.
diff --git a/changelog.d/14097.misc b/changelog.d/14097.misc
deleted file mode 100644
index 8392448c4d..0000000000
--- a/changelog.d/14097.misc
+++ /dev/null
@@ -1 +0,0 @@
-Indicate what endpoint came back with a JSON response we were unable to parse.
diff --git a/changelog.d/14106.removal b/changelog.d/14106.removal
deleted file mode 100644
index 08fa752897..0000000000
--- a/changelog.d/14106.removal
+++ /dev/null
@@ -1 +0,0 @@
-Remove the unstable identifier for [MSC3715](https://github.com/matrix-org/matrix-doc/pull/3715).
diff --git a/changelog.d/14110.doc b/changelog.d/14110.doc
new file mode 100644
index 0000000000..0927e31e4f
--- /dev/null
+++ b/changelog.d/14110.doc
@@ -0,0 +1 @@
+Correct the name of the config option [`encryption_enabled_by_default_for_room_type`](https://matrix-org.github.io/synapse/latest/usage/configuration/config_documentation.html#encryption_enabled_by_default_for_room_type).
diff --git a/changelog.d/14113.misc b/changelog.d/14113.misc
deleted file mode 100644
index 11aafc63ed..0000000000
--- a/changelog.d/14113.misc
+++ /dev/null
@@ -1 +0,0 @@
-Bump types-pillow from 9.0.15 to 9.2.2.
diff --git a/changelog.d/14114.misc b/changelog.d/14114.misc
deleted file mode 100644
index 273f82c382..0000000000
--- a/changelog.d/14114.misc
+++ /dev/null
@@ -1 +0,0 @@
-Bump types-psycopg2 from 2.9.9 to 2.9.21.1.
diff --git a/changelog.d/14133.misc b/changelog.d/14133.misc
new file mode 100644
index 0000000000..5180019c68
--- /dev/null
+++ b/changelog.d/14133.misc
@@ -0,0 +1 @@
+Bump types-opentracing from 2.4.7 to 2.4.10.
diff --git a/changelog.d/14191.doc b/changelog.d/14191.doc
new file mode 100644
index 0000000000..6b0eeb1ae1
--- /dev/null
+++ b/changelog.d/14191.doc
@@ -0,0 +1 @@
+Update docstrings of `SynapseError` and `FederationError` to bettter describe what they are used for and the effects of using them are.
diff --git a/changelog.d/14229.misc b/changelog.d/14229.misc
new file mode 100644
index 0000000000..b9cd9a34d5
--- /dev/null
+++ b/changelog.d/14229.misc
@@ -0,0 +1 @@
+Refactor `/key/` endpoints to use `RestServlet` classes.
diff --git a/changelog.d/14230.misc b/changelog.d/14230.misc
new file mode 100644
index 0000000000..c9b4b112cb
--- /dev/null
+++ b/changelog.d/14230.misc
@@ -0,0 +1 @@
+Switch to using the `matrix-org/backend-meta` version of `triage-incoming` for new issues in CI.
diff --git a/contrib/docker_compose_workers/README.md b/contrib/docker_compose_workers/README.md
index 4dbfee2853..bdd3dd32e0 100644
--- a/contrib/docker_compose_workers/README.md
+++ b/contrib/docker_compose_workers/README.md
@@ -94,20 +94,6 @@ worker_replication_host: synapse
 worker_replication_http_port: 9093
 ```
 
-### Add Workers to `instance_map`
-
-Locate the `instance_map` section of your `homeserver.yaml` and populate it with your workers:
-
-```yaml
-instance_map:
-  synapse-generic-worker-1:        # The worker_name setting in your worker configuration file
-    host: synapse-generic-worker-1 # The name of the worker service in your Docker Compose file
-    port: 8034                     # The port assigned to the replication listener in your worker config file
-  synapse-federation-sender-1:
-    host: synapse-federation-sender-1
-    port: 8034
-```
-
 ### Configure Federation Senders
 
 This section is applicable if you are using Federation senders (synapse.app.federation_sender). Locate the `send_federation` and `federation_sender_instances` settings in your `homeserver.yaml` and configure them:
@@ -122,4 +108,4 @@ federation_sender_instances:
 
 ## Other Worker types
 
-Using the concepts shown here it is possible to create other worker types in Docker Compose. See the [Workers](https://matrix-org.github.io/synapse/latest/workers.html#available-worker-applications) documentation for a list of available workers.
\ No newline at end of file
+Using the concepts shown here it is possible to create other worker types in Docker Compose. See the [Workers](https://matrix-org.github.io/synapse/latest/workers.html#available-worker-applications) documentation for a list of available workers.
diff --git a/contrib/docker_compose_workers/workers/synapse-federation-sender-1.yaml b/contrib/docker_compose_workers/workers/synapse-federation-sender-1.yaml
index 5ba42a92d2..5b40664d67 100644
--- a/contrib/docker_compose_workers/workers/synapse-federation-sender-1.yaml
+++ b/contrib/docker_compose_workers/workers/synapse-federation-sender-1.yaml
@@ -5,10 +5,4 @@ worker_name: synapse-federation-sender-1
 worker_replication_host: synapse
 worker_replication_http_port: 9093
 
-worker_listeners:
-  - type: http
-    port: 8034
-    resources:
-      - names: [replication]
-
 worker_log_config: /data/federation_sender.log.config
diff --git a/contrib/docker_compose_workers/workers/synapse-generic-worker-1.yaml b/contrib/docker_compose_workers/workers/synapse-generic-worker-1.yaml
index 694584105a..09e55df9f3 100644
--- a/contrib/docker_compose_workers/workers/synapse-generic-worker-1.yaml
+++ b/contrib/docker_compose_workers/workers/synapse-generic-worker-1.yaml
@@ -7,10 +7,6 @@ worker_replication_http_port: 9093
 
 worker_listeners:
   - type: http
-    port: 8034
-    resources:
-      - names: [replication]
-  - type: http
     port: 8081
     x_forwarded: true
     resources:
diff --git a/debian/changelog b/debian/changelog
index b228ef35fc..60ec92b47d 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,27 @@
+matrix-synapse-py3 (1.70.0~rc1) stable; urgency=medium
+
+  * New Synapse release 1.70.0rc1.
+
+ -- Synapse Packaging team <packages@matrix.org>  Wed, 19 Oct 2022 14:11:57 +0100
+
+matrix-synapse-py3 (1.69.0) stable; urgency=medium
+
+  * New Synapse release 1.69.0.
+
+ -- Synapse Packaging team <packages@matrix.org>  Mon, 17 Oct 2022 11:31:03 +0100
+
+matrix-synapse-py3 (1.69.0~rc4) stable; urgency=medium
+
+  * New Synapse release 1.69.0rc4.
+
+ -- Synapse Packaging team <packages@matrix.org>  Fri, 14 Oct 2022 15:04:47 +0100
+
+matrix-synapse-py3 (1.69.0~rc3) stable; urgency=medium
+
+  * New Synapse release 1.69.0rc3.
+
+ -- Synapse Packaging team <packages@matrix.org>  Wed, 12 Oct 2022 13:24:04 +0100
+
 matrix-synapse-py3 (1.69.0~rc2) stable; urgency=medium
 
   * New Synapse release 1.69.0rc2.
diff --git a/docker/Dockerfile b/docker/Dockerfile
index b20951d4cf..7f8756e8a4 100644
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -106,7 +106,13 @@ ENV CARGO_HOME=/cargo
 ENV PATH=/cargo/bin:/rust/bin:$PATH
 RUN mkdir /rust /cargo
 
-RUN curl -sSf https://sh.rustup.rs | sh -s -- -y --no-modify-path --default-toolchain stable
+RUN curl -sSf https://sh.rustup.rs | sh -s -- -y --no-modify-path --default-toolchain stable --profile minimal
+
+
+# arm64 builds consume a lot of memory if `CARGO_NET_GIT_FETCH_WITH_CLI` is not
+# set to true, so we expose it as a build-arg.
+ARG CARGO_NET_GIT_FETCH_WITH_CLI=false
+ENV CARGO_NET_GIT_FETCH_WITH_CLI=$CARGO_NET_GIT_FETCH_WITH_CLI
 
 # To speed up rebuilds, install all of the dependencies before we copy over
 # the whole synapse project, so that this layer in the Docker cache can be
@@ -121,7 +127,7 @@ RUN --mount=type=cache,target=/root/.cache/pip \
 COPY synapse /synapse/synapse/
 COPY rust /synapse/rust/
 # ... and what we need to `pip install`.
-COPY pyproject.toml README.rst build_rust.py /synapse/
+COPY pyproject.toml README.rst build_rust.py Cargo.toml Cargo.lock /synapse/
 
 # Repeat of earlier build argument declaration, as this is a new build stage.
 ARG TEST_ONLY_IGNORE_POETRY_LOCKFILE
@@ -129,7 +135,9 @@ ARG TEST_ONLY_IGNORE_POETRY_LOCKFILE
 # Install the synapse package itself.
 # If we have populated requirements.txt, we don't install any dependencies
 # as we should already have those from the previous `pip install` step.
-RUN if [ -z "$TEST_ONLY_IGNORE_POETRY_LOCKFILE" ]; then \
+RUN --mount=type=cache,target=/synapse/target,sharing=locked \
+  --mount=type=cache,target=${CARGO_HOME}/registry,sharing=locked \
+  if [ -z "$TEST_ONLY_IGNORE_POETRY_LOCKFILE" ]; then \
     pip install --prefix="/install" --no-deps --no-warn-script-location /synapse[all]; \
   else \
     pip install --prefix="/install" --no-warn-script-location /synapse[all]; \
diff --git a/docker/Dockerfile-dhvirtualenv b/docker/Dockerfile-dhvirtualenv
index ca3a259081..73165f6f85 100644
--- a/docker/Dockerfile-dhvirtualenv
+++ b/docker/Dockerfile-dhvirtualenv
@@ -92,7 +92,7 @@ ENV CARGO_HOME=/cargo
 ENV PATH=/cargo/bin:/rust/bin:$PATH
 RUN mkdir /rust /cargo
 
-RUN curl -sSf https://sh.rustup.rs | sh -s -- -y --no-modify-path --default-toolchain stable
+RUN curl -sSf https://sh.rustup.rs | sh -s -- -y --no-modify-path --default-toolchain stable --profile minimal
 
 
 COPY --from=builder /dh-virtualenv_1.2.2-1_all.deb /
diff --git a/docker/complement/conf/start_for_complement.sh b/docker/complement/conf/start_for_complement.sh
index cc6482f763..bb85d9fed7 100755
--- a/docker/complement/conf/start_for_complement.sh
+++ b/docker/complement/conf/start_for_complement.sh
@@ -57,6 +57,7 @@ if [[ -n "$SYNAPSE_COMPLEMENT_USE_WORKERS" ]]; then
       federation_reader, \
       federation_sender, \
       synchrotron, \
+      client_reader, \
       appservice, \
       pusher"
 
diff --git a/docker/complement/conf/workers-shared-extra.yaml.j2 b/docker/complement/conf/workers-shared-extra.yaml.j2
index 9e554a865e..c651645115 100644
--- a/docker/complement/conf/workers-shared-extra.yaml.j2
+++ b/docker/complement/conf/workers-shared-extra.yaml.j2
@@ -12,6 +12,8 @@ trusted_key_servers: []
 enable_registration: true
 enable_registration_without_verification: true
 bcrypt_rounds: 4
+url_preview_enabled: true
+url_preview_ip_range_blacklist: []
 
 ## Registration ##
 
diff --git a/docker/configure_workers_and_start.py b/docker/configure_workers_and_start.py
index 51583dc13d..1ea456b2f8 100755
--- a/docker/configure_workers_and_start.py
+++ b/docker/configure_workers_and_start.py
@@ -39,6 +39,7 @@
 # continue to work if so.
 
 import os
+import platform
 import subprocess
 import sys
 from pathlib import Path
@@ -107,6 +108,34 @@ WORKERS_CONFIG: Dict[str, Dict[str, Any]] = {
         "shared_extra_conf": {},
         "worker_extra_conf": "",
     },
+    "client_reader": {
+        "app": "synapse.app.generic_worker",
+        "listener_resources": ["client"],
+        "endpoint_patterns": [
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/publicRooms$",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/joined_members$",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/context/.*$",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/members$",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/state$",
+            "^/_matrix/client/v1/rooms/.*/hierarchy$",
+            "^/_matrix/client/(v1|unstable)/rooms/.*/relations/",
+            "^/_matrix/client/v1/rooms/.*/threads$",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/login$",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/account/3pid$",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/account/whoami$",
+            "^/_matrix/client/versions$",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/voip/turnServer$",
+            "^/_matrix/client/(r0|v3|unstable)/register$",
+            "^/_matrix/client/(r0|v3|unstable)/auth/.*/fallback/web$",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/messages$",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/event",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/joined_rooms",
+            "^/_matrix/client/(api/v1|r0|v3|unstable/.*)/rooms/.*/aliases",
+            "^/_matrix/client/(api/v1|r0|v3|unstable)/search",
+        ],
+        "shared_extra_conf": {},
+        "worker_extra_conf": "",
+    },
     "federation_reader": {
         "app": "synapse.app.generic_worker",
         "listener_resources": ["federation"],
@@ -201,24 +230,19 @@ upstream {upstream_worker_type} {{
 
 # Utility functions
 def log(txt: str) -> None:
-    """Log something to the stdout.
-
-    Args:
-        txt: The text to log.
-    """
     print(txt)
 
 
 def error(txt: str) -> NoReturn:
-    """Log something and exit with an error code.
-
-    Args:
-        txt: The text to log in error.
-    """
-    log(txt)
+    print(txt, file=sys.stderr)
     sys.exit(2)
 
 
+def flush_buffers() -> None:
+    sys.stdout.flush()
+    sys.stderr.flush()
+
+
 def convert(src: str, dst: str, **template_vars: object) -> None:
     """Generate a file from a template
 
@@ -299,7 +323,7 @@ def generate_base_homeserver_config() -> None:
     # start.py already does this for us, so just call that.
     # note that this script is copied in in the official, monolith dockerfile
     os.environ["SYNAPSE_HTTP_PORT"] = str(MAIN_PROCESS_HTTP_LISTENER_PORT)
-    subprocess.check_output(["/usr/local/bin/python", "/start.py", "migrate_config"])
+    subprocess.run(["/usr/local/bin/python", "/start.py", "migrate_config"], check=True)
 
 
 def generate_worker_files(
@@ -373,8 +397,8 @@ def generate_worker_files(
         # No workers, just the main process
         worker_types = []
     else:
-        # Split type names by comma
-        worker_types = worker_types_env.split(",")
+        # Split type names by comma, ignoring whitespace.
+        worker_types = [x.strip() for x in worker_types_env.split(",")]
 
     # Create the worker configuration directory if it doesn't already exist
     os.makedirs("/conf/workers", exist_ok=True)
@@ -393,8 +417,6 @@ def generate_worker_files(
 
     # For each worker type specified by the user, create config values
     for worker_type in worker_types:
-        worker_type = worker_type.strip()
-
         worker_config = WORKERS_CONFIG.get(worker_type)
         if worker_config:
             worker_config = worker_config.copy()
@@ -604,14 +626,24 @@ def main(args: List[str], environ: MutableMapping[str, str]) -> None:
         with open(mark_filepath, "w") as f:
             f.write("")
 
+    # Lifted right out of start.py
+    jemallocpath = "/usr/lib/%s-linux-gnu/libjemalloc.so.2" % (platform.machine(),)
+
+    if os.path.isfile(jemallocpath):
+        environ["LD_PRELOAD"] = jemallocpath
+    else:
+        log("Could not find %s, will not use" % (jemallocpath,))
+
     # Start supervisord, which will start Synapse, all of the configured worker
     # processes, redis, nginx etc. according to the config we created above.
     log("Starting supervisord")
-    os.execl(
+    flush_buffers()
+    os.execle(
         "/usr/local/bin/supervisord",
         "supervisord",
         "-c",
         "/etc/supervisor/supervisord.conf",
+        environ,
     )
 
 
diff --git a/docker/start.py b/docker/start.py
index 5a98dce551..ebcc599f04 100755
--- a/docker/start.py
+++ b/docker/start.py
@@ -13,14 +13,19 @@ import jinja2
 
 # Utility functions
 def log(txt: str) -> None:
-    print(txt, file=sys.stderr)
+    print(txt)
 
 
 def error(txt: str) -> NoReturn:
-    log(txt)
+    print(txt, file=sys.stderr)
     sys.exit(2)
 
 
+def flush_buffers() -> None:
+    sys.stdout.flush()
+    sys.stderr.flush()
+
+
 def convert(src: str, dst: str, environ: Mapping[str, object]) -> None:
     """Generate a file from a template
 
@@ -131,10 +136,10 @@ def generate_config_from_template(
 
     if ownership is not None:
         log(f"Setting ownership on /data to {ownership}")
-        subprocess.check_output(["chown", "-R", ownership, "/data"])
+        subprocess.run(["chown", "-R", ownership, "/data"], check=True)
         args = ["gosu", ownership] + args
 
-    subprocess.check_output(args)
+    subprocess.run(args, check=True)
 
 
 def run_generate_config(environ: Mapping[str, str], ownership: Optional[str]) -> None:
@@ -158,7 +163,7 @@ def run_generate_config(environ: Mapping[str, str], ownership: Optional[str]) ->
     if ownership is not None:
         # make sure that synapse has perms to write to the data dir.
         log(f"Setting ownership on {data_dir} to {ownership}")
-        subprocess.check_output(["chown", ownership, data_dir])
+        subprocess.run(["chown", ownership, data_dir], check=True)
 
     # create a suitable log config from our template
     log_config_file = "%s/%s.log.config" % (config_dir, server_name)
@@ -185,6 +190,7 @@ def run_generate_config(environ: Mapping[str, str], ownership: Optional[str]) ->
         "--open-private-ports",
     ]
     # log("running %s" % (args, ))
+    flush_buffers()
     os.execv(sys.executable, args)
 
 
@@ -267,8 +273,10 @@ running with 'migrate_config'. See the README for more details.
     args = [sys.executable] + args
     if ownership is not None:
         args = ["gosu", ownership] + args
+        flush_buffers()
         os.execve("/usr/sbin/gosu", args, environ)
     else:
+        flush_buffers()
         os.execve(sys.executable, args, environ)
 
 
diff --git a/docs/development/contributing_guide.md b/docs/development/contributing_guide.md
index 7f99220a3b..1e52f9808c 100644
--- a/docs/development/contributing_guide.md
+++ b/docs/development/contributing_guide.md
@@ -333,7 +333,7 @@ SYNAPSE_TEST_LOG_LEVEL=DEBUG COMPLEMENT_DIR=../complement ./scripts-dev/compleme
 ### Prettier formatting with `gotestfmt`
 
 If you want to format the output of the tests the same way as it looks in CI,
-install [gotestfmt](https://github.com/haveyoudebuggedit/gotestfmt).
+install [gotestfmt](https://github.com/GoTestTools/gotestfmt).
 
 You can then use this incantation to format the tests appropriately:
 
diff --git a/docs/usage/configuration/config_documentation.md b/docs/usage/configuration/config_documentation.md
index df3a62b27e..d81eda52c1 100644
--- a/docs/usage/configuration/config_documentation.md
+++ b/docs/usage/configuration/config_documentation.md
@@ -2088,7 +2088,7 @@ set.
 
 This is primarily intended for use with the `register_new_matrix_user` script
 (see [Registering a user](../../setup/installation.md#registering-a-user));
-however, the interface is [documented](../admin_api/register_api.html).
+however, the interface is [documented](../../admin_api/register_api.html).
 
 See also [`registration_shared_secret_path`](#registration_shared_secret_path).
 
@@ -3385,7 +3385,7 @@ push:
 Config options relating to rooms.
 
 ---
-### `encryption_enabled_by_default`
+### `encryption_enabled_by_default_for_room_type`
 
 Controls whether locally-created rooms should be end-to-end encrypted by
 default.
@@ -3541,9 +3541,9 @@ Example configuration:
 enable_room_list_search: false
 ```
 ---
-### `alias_creation`
+### `alias_creation_rules`
 
-The `alias_creation` option controls who is allowed to create aliases
+The `alias_creation_rules` option controls who is allowed to create aliases
 on this server.
 
 The format of this option is a list of rules that contain globs that
diff --git a/docs/workers.md b/docs/workers.md
index 27041ea57c..c27b3f8bd5 100644
--- a/docs/workers.md
+++ b/docs/workers.md
@@ -203,6 +203,8 @@ information.
     ^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/members$
     ^/_matrix/client/(api/v1|r0|v3|unstable)/rooms/.*/state$
     ^/_matrix/client/v1/rooms/.*/hierarchy$
+    ^/_matrix/client/(v1|unstable)/rooms/.*/relations/
+    ^/_matrix/client/v1/rooms/.*/threads$
     ^/_matrix/client/unstable/org.matrix.msc2716/rooms/.*/batch_send$
     ^/_matrix/client/unstable/im.nheko.summary/rooms/.*/summary$
     ^/_matrix/client/(r0|v3|unstable)/account/3pid$
diff --git a/poetry.lock b/poetry.lock
index e9cb095d86..2713cf2d69 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -10,7 +10,7 @@ python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*"
 dev = ["cloudpickle", "coverage[toml] (>=5.0.2)", "furo", "hypothesis", "mypy", "pre-commit", "pympler", "pytest (>=4.3.0)", "pytest-mypy-plugins", "six", "sphinx", "sphinx-notfound-page", "zope.interface"]
 docs = ["furo", "sphinx", "sphinx-notfound-page", "zope.interface"]
 tests = ["cloudpickle", "coverage[toml] (>=5.0.2)", "hypothesis", "mypy", "pympler", "pytest (>=4.3.0)", "pytest-mypy-plugins", "six", "zope.interface"]
-tests_no_zope = ["cloudpickle", "coverage[toml] (>=5.0.2)", "hypothesis", "mypy", "pympler", "pytest (>=4.3.0)", "pytest-mypy-plugins", "six"]
+tests-no-zope = ["cloudpickle", "coverage[toml] (>=5.0.2)", "hypothesis", "mypy", "pympler", "pytest (>=4.3.0)", "pytest-mypy-plugins", "six"]
 
 [[package]]
 name = "Authlib"
@@ -40,16 +40,12 @@ visualize = ["Twisted (>=16.1.1)", "graphviz (>0.5.1)"]
 
 [[package]]
 name = "bcrypt"
-version = "3.2.0"
+version = "4.0.1"
 description = "Modern password hashing for your software and your servers"
 category = "main"
 optional = false
 python-versions = ">=3.6"
 
-[package.dependencies]
-cffi = ">=1.1"
-six = ">=1.4.1"
-
 [package.extras]
 tests = ["pytest (>=3.2.1,!=3.3.0)"]
 typecheck = ["mypy"]
@@ -79,17 +75,20 @@ uvloop = ["uvloop (>=0.15.2)"]
 
 [[package]]
 name = "bleach"
-version = "4.1.0"
+version = "5.0.1"
 description = "An easy safelist-based HTML-sanitizing tool."
 category = "main"
 optional = false
-python-versions = ">=3.6"
+python-versions = ">=3.7"
 
 [package.dependencies]
-packaging = "*"
 six = ">=1.9.0"
 webencodings = "*"
 
+[package.extras]
+css = ["tinycss2 (>=1.1.0,<1.2)"]
+dev = ["Sphinx (==4.3.2)", "black (==22.3.0)", "build (==0.8.0)", "flake8 (==4.0.1)", "hashin (==0.17.0)", "mypy (==0.961)", "pip-tools (==6.6.2)", "pytest (==7.1.2)", "tox (==3.25.0)", "twine (==4.0.1)", "wheel (==0.37.1)"]
+
 [[package]]
 name = "canonicaljson"
 version = "1.6.3"
@@ -133,11 +132,11 @@ optional = false
 python-versions = ">=3.5.0"
 
 [package.extras]
-unicode_backport = ["unicodedata2"]
+unicode-backport = ["unicodedata2"]
 
 [[package]]
 name = "click"
-version = "8.1.1"
+version = "8.1.3"
 description = "Composable command line interface toolkit"
 category = "dev"
 optional = false
@@ -261,7 +260,7 @@ pyflakes = ">=2.4.0,<2.5.0"
 
 [[package]]
 name = "flake8-bugbear"
-version = "21.3.2"
+version = "22.9.23"
 description = "A plugin for flake8 finding likely bugs and design problems in your program. Contains warnings that don't belong in pyflakes and pycodestyle."
 category = "dev"
 optional = false
@@ -272,7 +271,7 @@ attrs = ">=19.2.0"
 flake8 = ">=3.0.0"
 
 [package.extras]
-dev = ["black", "coverage", "hypothesis", "hypothesmith"]
+dev = ["coverage", "hypothesis", "hypothesmith (>=0.2)", "pre-commit"]
 
 [[package]]
 name = "flake8-comprehensions"
@@ -338,7 +337,7 @@ idna = ">=2.5"
 
 [[package]]
 name = "idna"
-version = "3.3"
+version = "3.4"
 description = "Internationalized Domain Names in Applications (IDNA)"
 category = "main"
 optional = false
@@ -404,9 +403,9 @@ python-versions = ">=3.6.1,<4.0"
 
 [package.extras]
 colors = ["colorama (>=0.4.3,<0.5.0)"]
-pipfile_deprecated_finder = ["pipreqs", "requirementslib"]
+pipfile-deprecated-finder = ["pipreqs", "requirementslib"]
 plugins = ["setuptools"]
-requirements_deprecated_finder = ["pip-api", "pipreqs"]
+requirements-deprecated-finder = ["pip-api", "pipreqs"]
 
 [[package]]
 name = "jaeger-client"
@@ -722,7 +721,7 @@ twisted = ["twisted"]
 
 [[package]]
 name = "psycopg2"
-version = "2.9.3"
+version = "2.9.4"
 description = "psycopg2 - Python-PostgreSQL Database Adapter"
 category = "main"
 optional = true
@@ -811,7 +810,7 @@ python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
 
 [[package]]
 name = "pygithub"
-version = "1.55"
+version = "1.56"
 description = "Use the full Github API v3"
 category = "dev"
 optional = false
@@ -1007,7 +1006,7 @@ urllib3 = ">=1.21.1,<1.27"
 
 [package.extras]
 socks = ["PySocks (>=1.5.6,!=1.5.7)", "win-inet-pton"]
-use_chardet_on_py3 = ["chardet (>=3.0.2,<5)"]
+use-chardet-on-py3 = ["chardet (>=3.0.2,<5)"]
 
 [[package]]
 name = "requests-toolbelt"
@@ -1077,7 +1076,7 @@ django = ["django (>=1.8)"]
 falcon = ["falcon (>=1.4)"]
 flask = ["blinker (>=1.1)", "flask (>=0.11)"]
 httpx = ["httpx (>=0.16.0)"]
-pure_eval = ["asttokens", "executing", "pure-eval"]
+pure-eval = ["asttokens", "executing", "pure-eval"]
 pyspark = ["pyspark (>=2.4.4)"]
 quart = ["blinker (>=1.1)", "quart (>=0.16.1)"]
 rq = ["rq (>=0.6)"]
@@ -1309,11 +1308,11 @@ urllib3 = ">=1.26.0"
 
 [[package]]
 name = "twisted"
-version = "22.4.0"
+version = "22.8.0"
 description = "An asynchronous networking framework written in Python"
 category = "main"
 optional = false
-python-versions = ">=3.6.7"
+python-versions = ">=3.7.1"
 
 [package.dependencies]
 attrs = ">=19.2.0"
@@ -1322,27 +1321,28 @@ constantly = ">=15.1"
 hyperlink = ">=17.1.1"
 idna = {version = ">=2.4", optional = true, markers = "extra == \"tls\""}
 incremental = ">=21.3.0"
-pyopenssl = {version = ">=16.0.0", optional = true, markers = "extra == \"tls\""}
+pyopenssl = {version = ">=21.0.0", optional = true, markers = "extra == \"tls\""}
 service-identity = {version = ">=18.1.0", optional = true, markers = "extra == \"tls\""}
 twisted-iocpsupport = {version = ">=1.0.2,<2", markers = "platform_system == \"Windows\""}
 typing-extensions = ">=3.6.5"
 "zope.interface" = ">=4.4.2"
 
 [package.extras]
-all_non_platform = ["PyHamcrest (>=1.9.0)", "appdirs (>=1.4.0)", "bcrypt (>=3.0.0)", "contextvars (>=2.4,<3)", "cryptography (>=2.6)", "cython-test-exception-raiser (>=1.0.2,<2)", "h2 (>=3.0,<5.0)", "idna (>=2.4)", "priority (>=1.1.0,<2.0)", "pyasn1", "pyopenssl (>=16.0.0)", "pyserial (>=3.0)", "pywin32 (!=226)", "service-identity (>=18.1.0)"]
+all-non-platform = ["PyHamcrest (>=1.9.0)", "appdirs (>=1.4.0)", "bcrypt (>=3.0.0)", "contextvars (>=2.4,<3)", "cryptography (>=2.6)", "cython-test-exception-raiser (>=1.0.2,<2)", "h2 (>=3.0,<5.0)", "idna (>=2.4)", "priority (>=1.1.0,<2.0)", "pyasn1", "pyopenssl (>=21.0.0)", "pyserial (>=3.0)", "pywin32 (!=226)", "service-identity (>=18.1.0)"]
 conch = ["appdirs (>=1.4.0)", "bcrypt (>=3.0.0)", "cryptography (>=2.6)", "pyasn1"]
-conch_nacl = ["PyNaCl", "appdirs (>=1.4.0)", "bcrypt (>=3.0.0)", "cryptography (>=2.6)", "pyasn1"]
+conch-nacl = ["PyNaCl", "appdirs (>=1.4.0)", "bcrypt (>=3.0.0)", "cryptography (>=2.6)", "pyasn1"]
 contextvars = ["contextvars (>=2.4,<3)"]
-dev = ["coverage (>=6b1,<7)", "pydoctor (>=21.9.0,<21.10.0)", "pyflakes (>=2.2,<3.0)", "python-subunit (>=1.4,<2.0)", "readthedocs-sphinx-ext (>=2.1,<3.0)", "sphinx (>=4.1.2,<6)", "sphinx-rtd-theme (>=0.5,<1.0)", "towncrier (>=19.2,<20.0)", "twistedchecker (>=0.7,<1.0)"]
-dev_release = ["pydoctor (>=21.9.0,<21.10.0)", "readthedocs-sphinx-ext (>=2.1,<3.0)", "sphinx (>=4.1.2,<6)", "sphinx-rtd-theme (>=0.5,<1.0)", "towncrier (>=19.2,<20.0)"]
+dev = ["coverage (>=6b1,<7)", "pydoctor (>=22.7.0,<22.8.0)", "pyflakes (>=2.2,<3.0)", "python-subunit (>=1.4,<2.0)", "readthedocs-sphinx-ext (>=2.1,<3.0)", "sphinx (>=4.1.2,<6)", "sphinx-rtd-theme (>=0.5,<1.0)", "towncrier (>=19.2,<20.0)", "twistedchecker (>=0.7,<1.0)"]
+dev-release = ["pydoctor (>=22.7.0,<22.8.0)", "readthedocs-sphinx-ext (>=2.1,<3.0)", "sphinx (>=4.1.2,<6)", "sphinx-rtd-theme (>=0.5,<1.0)", "towncrier (>=19.2,<20.0)"]
+gtk-platform = ["PyHamcrest (>=1.9.0)", "appdirs (>=1.4.0)", "bcrypt (>=3.0.0)", "contextvars (>=2.4,<3)", "cryptography (>=2.6)", "cython-test-exception-raiser (>=1.0.2,<2)", "h2 (>=3.0,<5.0)", "idna (>=2.4)", "priority (>=1.1.0,<2.0)", "pyasn1", "pygobject", "pyopenssl (>=21.0.0)", "pyserial (>=3.0)", "pywin32 (!=226)", "service-identity (>=18.1.0)"]
 http2 = ["h2 (>=3.0,<5.0)", "priority (>=1.1.0,<2.0)"]
-macos_platform = ["PyHamcrest (>=1.9.0)", "appdirs (>=1.4.0)", "bcrypt (>=3.0.0)", "contextvars (>=2.4,<3)", "cryptography (>=2.6)", "cython-test-exception-raiser (>=1.0.2,<2)", "h2 (>=3.0,<5.0)", "idna (>=2.4)", "priority (>=1.1.0,<2.0)", "pyasn1", "pyobjc-core", "pyobjc-framework-CFNetwork", "pyobjc-framework-Cocoa", "pyopenssl (>=16.0.0)", "pyserial (>=3.0)", "pywin32 (!=226)", "service-identity (>=18.1.0)"]
-mypy = ["PyHamcrest (>=1.9.0)", "PyNaCl", "appdirs (>=1.4.0)", "bcrypt (>=3.0.0)", "contextvars (>=2.4,<3)", "coverage (>=6b1,<7)", "cryptography (>=2.6)", "cython-test-exception-raiser (>=1.0.2,<2)", "h2 (>=3.0,<5.0)", "idna (>=2.4)", "mypy (==0.930)", "mypy-zope (==0.3.4)", "priority (>=1.1.0,<2.0)", "pyasn1", "pydoctor (>=21.9.0,<21.10.0)", "pyflakes (>=2.2,<3.0)", "pyopenssl (>=16.0.0)", "pyserial (>=3.0)", "python-subunit (>=1.4,<2.0)", "pywin32 (!=226)", "readthedocs-sphinx-ext (>=2.1,<3.0)", "service-identity (>=18.1.0)", "sphinx (>=4.1.2,<6)", "sphinx-rtd-theme (>=0.5,<1.0)", "towncrier (>=19.2,<20.0)", "twistedchecker (>=0.7,<1.0)", "types-pyOpenSSL", "types-setuptools"]
-osx_platform = ["PyHamcrest (>=1.9.0)", "appdirs (>=1.4.0)", "bcrypt (>=3.0.0)", "contextvars (>=2.4,<3)", "cryptography (>=2.6)", "cython-test-exception-raiser (>=1.0.2,<2)", "h2 (>=3.0,<5.0)", "idna (>=2.4)", "priority (>=1.1.0,<2.0)", "pyasn1", "pyobjc-core", "pyobjc-framework-CFNetwork", "pyobjc-framework-Cocoa", "pyopenssl (>=16.0.0)", "pyserial (>=3.0)", "pywin32 (!=226)", "service-identity (>=18.1.0)"]
+macos-platform = ["PyHamcrest (>=1.9.0)", "appdirs (>=1.4.0)", "bcrypt (>=3.0.0)", "contextvars (>=2.4,<3)", "cryptography (>=2.6)", "cython-test-exception-raiser (>=1.0.2,<2)", "h2 (>=3.0,<5.0)", "idna (>=2.4)", "priority (>=1.1.0,<2.0)", "pyasn1", "pyobjc-core", "pyobjc-framework-CFNetwork", "pyobjc-framework-Cocoa", "pyopenssl (>=21.0.0)", "pyserial (>=3.0)", "pywin32 (!=226)", "service-identity (>=18.1.0)"]
+mypy = ["PyHamcrest (>=1.9.0)", "PyNaCl", "appdirs (>=1.4.0)", "bcrypt (>=3.0.0)", "contextvars (>=2.4,<3)", "coverage (>=6b1,<7)", "cryptography (>=2.6)", "cython-test-exception-raiser (>=1.0.2,<2)", "h2 (>=3.0,<5.0)", "idna (>=2.4)", "mypy (==0.930)", "mypy-zope (==0.3.4)", "priority (>=1.1.0,<2.0)", "pyasn1", "pydoctor (>=22.7.0,<22.8.0)", "pyflakes (>=2.2,<3.0)", "pyopenssl (>=21.0.0)", "pyserial (>=3.0)", "python-subunit (>=1.4,<2.0)", "pywin32 (!=226)", "readthedocs-sphinx-ext (>=2.1,<3.0)", "service-identity (>=18.1.0)", "sphinx (>=4.1.2,<6)", "sphinx-rtd-theme (>=0.5,<1.0)", "towncrier (>=19.2,<20.0)", "twistedchecker (>=0.7,<1.0)", "types-pyOpenSSL", "types-setuptools"]
+osx-platform = ["PyHamcrest (>=1.9.0)", "appdirs (>=1.4.0)", "bcrypt (>=3.0.0)", "contextvars (>=2.4,<3)", "cryptography (>=2.6)", "cython-test-exception-raiser (>=1.0.2,<2)", "h2 (>=3.0,<5.0)", "idna (>=2.4)", "priority (>=1.1.0,<2.0)", "pyasn1", "pyobjc-core", "pyobjc-framework-CFNetwork", "pyobjc-framework-Cocoa", "pyopenssl (>=21.0.0)", "pyserial (>=3.0)", "pywin32 (!=226)", "service-identity (>=18.1.0)"]
 serial = ["pyserial (>=3.0)", "pywin32 (!=226)"]
 test = ["PyHamcrest (>=1.9.0)", "cython-test-exception-raiser (>=1.0.2,<2)"]
-tls = ["idna (>=2.4)", "pyopenssl (>=16.0.0)", "service-identity (>=18.1.0)"]
-windows_platform = ["PyHamcrest (>=1.9.0)", "appdirs (>=1.4.0)", "bcrypt (>=3.0.0)", "contextvars (>=2.4,<3)", "cryptography (>=2.6)", "cython-test-exception-raiser (>=1.0.2,<2)", "h2 (>=3.0,<5.0)", "idna (>=2.4)", "priority (>=1.1.0,<2.0)", "pyasn1", "pyopenssl (>=16.0.0)", "pyserial (>=3.0)", "pywin32 (!=226)", "pywin32 (!=226)", "service-identity (>=18.1.0)"]
+tls = ["idna (>=2.4)", "pyopenssl (>=21.0.0)", "service-identity (>=18.1.0)"]
+windows-platform = ["PyHamcrest (>=1.9.0)", "appdirs (>=1.4.0)", "bcrypt (>=3.0.0)", "contextvars (>=2.4,<3)", "cryptography (>=2.6)", "cython-test-exception-raiser (>=1.0.2,<2)", "h2 (>=3.0,<5.0)", "idna (>=2.4)", "priority (>=1.1.0,<2.0)", "pyasn1", "pyopenssl (>=21.0.0)", "pyserial (>=3.0)", "pywin32 (!=226)", "pywin32 (!=226)", "service-identity (>=18.1.0)"]
 
 [[package]]
 name = "twisted-iocpsupport"
@@ -1374,7 +1374,7 @@ python-versions = ">=3.6"
 
 [[package]]
 name = "types-bleach"
-version = "4.1.4"
+version = "5.0.3"
 description = "Typing stubs for bleach"
 category = "dev"
 optional = false
@@ -1426,15 +1426,15 @@ python-versions = "*"
 
 [[package]]
 name = "types-opentracing"
-version = "2.4.7"
+version = "2.4.10"
 description = "Typing stubs for opentracing"
 category = "dev"
 optional = false
 python-versions = "*"
 
 [[package]]
-name = "types-Pillow"
-version = "9.2.2"
+name = "types-pillow"
+version = "9.2.2.1"
 description = "Typing stubs for Pillow"
 category = "dev"
 optional = false
@@ -1480,7 +1480,7 @@ types-urllib3 = "<1.27"
 
 [[package]]
 name = "types-setuptools"
-version = "65.4.0.0"
+version = "65.5.0.1"
 description = "Typing stubs for setuptools"
 category = "dev"
 optional = false
@@ -1496,11 +1496,11 @@ python-versions = "*"
 
 [[package]]
 name = "typing-extensions"
-version = "4.1.1"
-description = "Backported and Experimental Type Hints for Python 3.6+"
+version = "4.4.0"
+description = "Backported and Experimental Type Hints for Python 3.7+"
 category = "main"
 optional = false
-python-versions = ">=3.6"
+python-versions = ">=3.7"
 
 [[package]]
 name = "unpaddedbase64"
@@ -1617,7 +1617,7 @@ test = ["zope.i18nmessageid", "zope.testing", "zope.testrunner"]
 
 [extras]
 all = ["matrix-synapse-ldap3", "psycopg2", "psycopg2cffi", "psycopg2cffi-compat", "pysaml2", "authlib", "lxml", "sentry-sdk", "jaeger-client", "opentracing", "txredisapi", "hiredis", "Pympler"]
-cache_memory = ["Pympler"]
+cache-memory = ["Pympler"]
 jwt = ["authlib"]
 matrix-synapse-ldap3 = ["matrix-synapse-ldap3"]
 oidc = ["authlib"]
@@ -1628,12 +1628,12 @@ saml2 = ["pysaml2"]
 sentry = ["sentry-sdk"]
 systemd = ["systemd-python"]
 test = ["parameterized", "idna"]
-url_preview = ["lxml"]
+url-preview = ["lxml"]
 
 [metadata]
 lock-version = "1.1"
 python-versions = "^3.7.1"
-content-hash = "9d74da808739e4c3d15a2d3473f01ad419f62aec8bf28613b03bd69136c4745b"
+content-hash = "9400cb5c92bb4648238f652f5e7f81df51cdcf9b7c69d645f35beaa4acb2f420"
 
 [metadata.files]
 attrs = [
@@ -1649,16 +1649,27 @@ automat = [
     {file = "Automat-20.2.0.tar.gz", hash = "sha256:7979803c74610e11ef0c0d68a2942b152df52da55336e0c9d58daf1831cbdf33"},
 ]
 bcrypt = [
-    {file = "bcrypt-3.2.0-cp36-abi3-macosx_10_10_universal2.whl", hash = "sha256:b589229207630484aefe5899122fb938a5b017b0f4349f769b8c13e78d99a8fd"},
-    {file = "bcrypt-3.2.0-cp36-abi3-macosx_10_9_x86_64.whl", hash = "sha256:c95d4cbebffafcdd28bd28bb4e25b31c50f6da605c81ffd9ad8a3d1b2ab7b1b6"},
-    {file = "bcrypt-3.2.0-cp36-abi3-manylinux1_x86_64.whl", hash = "sha256:63d4e3ff96188e5898779b6057878fecf3f11cfe6ec3b313ea09955d587ec7a7"},
-    {file = "bcrypt-3.2.0-cp36-abi3-manylinux2010_x86_64.whl", hash = "sha256:cd1ea2ff3038509ea95f687256c46b79f5fc382ad0aa3664d200047546d511d1"},
-    {file = "bcrypt-3.2.0-cp36-abi3-manylinux2014_aarch64.whl", hash = "sha256:cdcdcb3972027f83fe24a48b1e90ea4b584d35f1cc279d76de6fc4b13376239d"},
-    {file = "bcrypt-3.2.0-cp36-abi3-manylinux_2_17_x86_64.manylinux2014_x86_64.manylinux_2_24_x86_64.whl", hash = "sha256:a0584a92329210fcd75eb8a3250c5a941633f8bfaf2a18f81009b097732839b7"},
-    {file = "bcrypt-3.2.0-cp36-abi3-musllinux_1_1_x86_64.whl", hash = "sha256:56e5da069a76470679f312a7d3d23deb3ac4519991a0361abc11da837087b61d"},
-    {file = "bcrypt-3.2.0-cp36-abi3-win32.whl", hash = "sha256:a67fb841b35c28a59cebed05fbd3e80eea26e6d75851f0574a9273c80f3e9b55"},
-    {file = "bcrypt-3.2.0-cp36-abi3-win_amd64.whl", hash = "sha256:81fec756feff5b6818ea7ab031205e1d323d8943d237303baca2c5f9c7846f34"},
-    {file = "bcrypt-3.2.0.tar.gz", hash = "sha256:5b93c1726e50a93a033c36e5ca7fdcd29a5c7395af50a6892f5d9e7c6cfbfb29"},
+    {file = "bcrypt-4.0.1-cp36-abi3-macosx_10_10_universal2.whl", hash = "sha256:b1023030aec778185a6c16cf70f359cbb6e0c289fd564a7cfa29e727a1c38f8f"},
+    {file = "bcrypt-4.0.1-cp36-abi3-manylinux_2_17_aarch64.manylinux2014_aarch64.manylinux_2_24_aarch64.whl", hash = "sha256:08d2947c490093a11416df18043c27abe3921558d2c03e2076ccb28a116cb6d0"},
+    {file = "bcrypt-4.0.1-cp36-abi3-manylinux_2_17_aarch64.manylinux2014_aarch64.whl", hash = "sha256:0eaa47d4661c326bfc9d08d16debbc4edf78778e6aaba29c1bc7ce67214d4410"},
+    {file = "bcrypt-4.0.1-cp36-abi3-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:ae88eca3024bb34bb3430f964beab71226e761f51b912de5133470b649d82344"},
+    {file = "bcrypt-4.0.1-cp36-abi3-manylinux_2_24_x86_64.whl", hash = "sha256:a522427293d77e1c29e303fc282e2d71864579527a04ddcfda6d4f8396c6c36a"},
+    {file = "bcrypt-4.0.1-cp36-abi3-manylinux_2_28_aarch64.whl", hash = "sha256:fbdaec13c5105f0c4e5c52614d04f0bca5f5af007910daa8b6b12095edaa67b3"},
+    {file = "bcrypt-4.0.1-cp36-abi3-manylinux_2_28_x86_64.whl", hash = "sha256:ca3204d00d3cb2dfed07f2d74a25f12fc12f73e606fcaa6975d1f7ae69cacbb2"},
+    {file = "bcrypt-4.0.1-cp36-abi3-musllinux_1_1_aarch64.whl", hash = "sha256:089098effa1bc35dc055366740a067a2fc76987e8ec75349eb9484061c54f535"},
+    {file = "bcrypt-4.0.1-cp36-abi3-musllinux_1_1_x86_64.whl", hash = "sha256:e9a51bbfe7e9802b5f3508687758b564069ba937748ad7b9e890086290d2f79e"},
+    {file = "bcrypt-4.0.1-cp36-abi3-win32.whl", hash = "sha256:2caffdae059e06ac23fce178d31b4a702f2a3264c20bfb5ff541b338194d8fab"},
+    {file = "bcrypt-4.0.1-cp36-abi3-win_amd64.whl", hash = "sha256:8a68f4341daf7522fe8d73874de8906f3a339048ba406be6ddc1b3ccb16fc0d9"},
+    {file = "bcrypt-4.0.1-pp37-pypy37_pp73-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:bf4fa8b2ca74381bb5442c089350f09a3f17797829d958fad058d6e44d9eb83c"},
+    {file = "bcrypt-4.0.1-pp37-pypy37_pp73-manylinux_2_24_x86_64.whl", hash = "sha256:67a97e1c405b24f19d08890e7ae0c4f7ce1e56a712a016746c8b2d7732d65d4b"},
+    {file = "bcrypt-4.0.1-pp37-pypy37_pp73-manylinux_2_28_x86_64.whl", hash = "sha256:b3b85202d95dd568efcb35b53936c5e3b3600c7cdcc6115ba461df3a8e89f38d"},
+    {file = "bcrypt-4.0.1-pp38-pypy38_pp73-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:cbb03eec97496166b704ed663a53680ab57c5084b2fc98ef23291987b525cb7d"},
+    {file = "bcrypt-4.0.1-pp38-pypy38_pp73-manylinux_2_24_x86_64.whl", hash = "sha256:5ad4d32a28b80c5fa6671ccfb43676e8c1cc232887759d1cd7b6f56ea4355215"},
+    {file = "bcrypt-4.0.1-pp38-pypy38_pp73-manylinux_2_28_x86_64.whl", hash = "sha256:b57adba8a1444faf784394de3436233728a1ecaeb6e07e8c22c8848f179b893c"},
+    {file = "bcrypt-4.0.1-pp39-pypy39_pp73-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:705b2cea8a9ed3d55b4491887ceadb0106acf7c6387699fca771af56b1cdeeda"},
+    {file = "bcrypt-4.0.1-pp39-pypy39_pp73-manylinux_2_24_x86_64.whl", hash = "sha256:2b3ac11cf45161628f1f3733263e63194f22664bf4d0c0f3ab34099c02134665"},
+    {file = "bcrypt-4.0.1-pp39-pypy39_pp73-manylinux_2_28_x86_64.whl", hash = "sha256:3100851841186c25f127731b9fa11909ab7b1df6fc4b9f8353f4f1fd952fbf71"},
+    {file = "bcrypt-4.0.1.tar.gz", hash = "sha256:27d375903ac8261cfe4047f6709d16f7d18d39b1ec92aaf72af989552a650ebd"},
 ]
 black = [
     {file = "black-22.3.0-cp310-cp310-macosx_10_9_universal2.whl", hash = "sha256:2497f9c2386572e28921fa8bec7be3e51de6801f7459dffd6e62492531c47e09"},
@@ -1686,8 +1697,8 @@ black = [
     {file = "black-22.3.0.tar.gz", hash = "sha256:35020b8886c022ced9282b51b5a875b6d1ab0c387b31a065b84db7c33085ca79"},
 ]
 bleach = [
-    {file = "bleach-4.1.0-py2.py3-none-any.whl", hash = "sha256:4d2651ab93271d1129ac9cbc679f524565cc8a1b791909c4a51eac4446a15994"},
-    {file = "bleach-4.1.0.tar.gz", hash = "sha256:0900d8b37eba61a802ee40ac0061f8c2b5dee29c1927dd1d233e075ebf5a71da"},
+    {file = "bleach-5.0.1-py3-none-any.whl", hash = "sha256:085f7f33c15bd408dd9b17a4ad77c577db66d76203e5984b1bd59baeee948b2a"},
+    {file = "bleach-5.0.1.tar.gz", hash = "sha256:0d03255c47eb9bd2f26aa9bb7f2107732e7e8fe195ca2f64709fcf3b0a4a085c"},
 ]
 canonicaljson = [
     {file = "canonicaljson-1.6.3-py3-none-any.whl", hash = "sha256:6ba3cf1702fa3d209b3e915a4e9a3e4ef194f1e8fca189c1f0b7a2a7686a27e6"},
@@ -1754,8 +1765,8 @@ charset-normalizer = [
     {file = "charset_normalizer-2.0.12-py3-none-any.whl", hash = "sha256:6881edbebdb17b39b4eaaa821b438bf6eddffb4468cf344f09f89def34a8b1df"},
 ]
 click = [
-    {file = "click-8.1.1-py3-none-any.whl", hash = "sha256:5e0d195c2067da3136efb897449ec1e9e6c98282fbf30d7f9e164af9be901a6b"},
-    {file = "click-8.1.1.tar.gz", hash = "sha256:7ab900e38149c9872376e8f9b5986ddcaf68c0f413cf73678a0bca5547e6f976"},
+    {file = "click-8.1.3-py3-none-any.whl", hash = "sha256:bb4d8133cb15a609f44e8213d9b391b0809795062913b383c62be0ee95b1db48"},
+    {file = "click-8.1.3.tar.gz", hash = "sha256:7682dc8afb30297001674575ea00d1814d808d6a36af415a82bd481d37ba7b8e"},
 ]
 click-default-group = [
     {file = "click-default-group-1.2.2.tar.gz", hash = "sha256:d9560e8e8dfa44b3562fbc9425042a0fd6d21956fcc2db0077f63f34253ab904"},
@@ -1815,8 +1826,8 @@ flake8 = [
     {file = "flake8-4.0.1.tar.gz", hash = "sha256:806e034dda44114815e23c16ef92f95c91e4c71100ff52813adf7132a6ad870d"},
 ]
 flake8-bugbear = [
-    {file = "flake8-bugbear-21.3.2.tar.gz", hash = "sha256:cadce434ceef96463b45a7c3000f23527c04ea4b531d16c7ac8886051f516ca0"},
-    {file = "flake8_bugbear-21.3.2-py36.py37.py38-none-any.whl", hash = "sha256:5d6ccb0c0676c738a6e066b4d50589c408dcc1c5bf1d73b464b18b73cd6c05c2"},
+    {file = "flake8-bugbear-22.9.23.tar.gz", hash = "sha256:17b9623325e6e0dcdcc80ed9e4aa811287fcc81d7e03313b8736ea5733759937"},
+    {file = "flake8_bugbear-22.9.23-py3-none-any.whl", hash = "sha256:cd2779b2b7ada212d7a322814a1e5651f1868ab0d3f24cc9da66169ab8fda474"},
 ]
 flake8-comprehensions = [
     {file = "flake8-comprehensions-3.8.0.tar.gz", hash = "sha256:8e108707637b1d13734f38e03435984f6b7854fa6b5a4e34f93e69534be8e521"},
@@ -1897,8 +1908,8 @@ hyperlink = [
     {file = "hyperlink-21.0.0.tar.gz", hash = "sha256:427af957daa58bc909471c6c40f74c5450fa123dd093fc53efd2e91d2705a56b"},
 ]
 idna = [
-    {file = "idna-3.3-py3-none-any.whl", hash = "sha256:84d9dd047ffa80596e0f246e2eab0b391788b0503584e8945f2368256d2735ff"},
-    {file = "idna-3.3.tar.gz", hash = "sha256:9d643ff0a55b762d5cdb124b8eaa99c66322e2157b69160bc32796e824360e6d"},
+    {file = "idna-3.4-py3-none-any.whl", hash = "sha256:90b77e79eaa3eba6de819a0c442c0b4ceefc341a7a2ab77d7562bf49f425c5c2"},
+    {file = "idna-3.4.tar.gz", hash = "sha256:814f528e8dead7d329833b91c5faa87d60bf71824cd12a7530b5526063d02cb4"},
 ]
 ijson = [
     {file = "ijson-3.1.4-cp27-cp27m-macosx_10_9_x86_64.whl", hash = "sha256:6c1a777096be5f75ffebb335c6d2ebc0e489b231496b7f2ca903aa061fe7d381"},
@@ -2294,17 +2305,17 @@ prometheus-client = [
     {file = "prometheus_client-0.14.0.tar.gz", hash = "sha256:8f7a922dd5455ad524b6ba212ce8eb2b4b05e073f4ec7218287f88b1cac34750"},
 ]
 psycopg2 = [
-    {file = "psycopg2-2.9.3-cp310-cp310-win32.whl", hash = "sha256:083707a696e5e1c330af2508d8fab36f9700b26621ccbcb538abe22e15485362"},
-    {file = "psycopg2-2.9.3-cp310-cp310-win_amd64.whl", hash = "sha256:d3ca6421b942f60c008f81a3541e8faf6865a28d5a9b48544b0ee4f40cac7fca"},
-    {file = "psycopg2-2.9.3-cp36-cp36m-win32.whl", hash = "sha256:9572e08b50aed176ef6d66f15a21d823bb6f6d23152d35e8451d7d2d18fdac56"},
-    {file = "psycopg2-2.9.3-cp36-cp36m-win_amd64.whl", hash = "sha256:a81e3866f99382dfe8c15a151f1ca5fde5815fde879348fe5a9884a7c092a305"},
-    {file = "psycopg2-2.9.3-cp37-cp37m-win32.whl", hash = "sha256:cb10d44e6694d763fa1078a26f7f6137d69f555a78ec85dc2ef716c37447e4b2"},
-    {file = "psycopg2-2.9.3-cp37-cp37m-win_amd64.whl", hash = "sha256:4295093a6ae3434d33ec6baab4ca5512a5082cc43c0505293087b8a46d108461"},
-    {file = "psycopg2-2.9.3-cp38-cp38-win32.whl", hash = "sha256:34b33e0162cfcaad151f249c2649fd1030010c16f4bbc40a604c1cb77173dcf7"},
-    {file = "psycopg2-2.9.3-cp38-cp38-win_amd64.whl", hash = "sha256:0762c27d018edbcb2d34d51596e4346c983bd27c330218c56c4dc25ef7e819bf"},
-    {file = "psycopg2-2.9.3-cp39-cp39-win32.whl", hash = "sha256:8cf3878353cc04b053822896bc4922b194792df9df2f1ad8da01fb3043602126"},
-    {file = "psycopg2-2.9.3-cp39-cp39-win_amd64.whl", hash = "sha256:06f32425949bd5fe8f625c49f17ebb9784e1e4fe928b7cce72edc36fb68e4c0c"},
-    {file = "psycopg2-2.9.3.tar.gz", hash = "sha256:8e841d1bf3434da985cc5ef13e6f75c8981ced601fd70cc6bf33351b91562981"},
+    {file = "psycopg2-2.9.4-cp310-cp310-win32.whl", hash = "sha256:8de6a9fc5f42fa52f559e65120dcd7502394692490c98fed1221acf0819d7797"},
+    {file = "psycopg2-2.9.4-cp310-cp310-win_amd64.whl", hash = "sha256:1da77c061bdaab450581458932ae5e469cc6e36e0d62f988376e9f513f11cb5c"},
+    {file = "psycopg2-2.9.4-cp36-cp36m-win32.whl", hash = "sha256:a11946bad3557ca254f17357d5a4ed63bdca45163e7a7d2bfb8e695df069cc3a"},
+    {file = "psycopg2-2.9.4-cp36-cp36m-win_amd64.whl", hash = "sha256:46361c054df612c3cc813fdb343733d56543fb93565cff0f8ace422e4da06acb"},
+    {file = "psycopg2-2.9.4-cp37-cp37m-win32.whl", hash = "sha256:aafa96f2da0071d6dd0cbb7633406d99f414b40ab0f918c9d9af7df928a1accb"},
+    {file = "psycopg2-2.9.4-cp37-cp37m-win_amd64.whl", hash = "sha256:aa184d551a767ad25df3b8d22a0a62ef2962e0e374c04f6cbd1204947f540d61"},
+    {file = "psycopg2-2.9.4-cp38-cp38-win32.whl", hash = "sha256:839f9ea8f6098e39966d97fcb8d08548fbc57c523a1e27a1f0609addf40f777c"},
+    {file = "psycopg2-2.9.4-cp38-cp38-win_amd64.whl", hash = "sha256:c7fa041b4acb913f6968fce10169105af5200f296028251d817ab37847c30184"},
+    {file = "psycopg2-2.9.4-cp39-cp39-win32.whl", hash = "sha256:07b90a24d5056687781ddaef0ea172fd951f2f7293f6ffdd03d4f5077801f426"},
+    {file = "psycopg2-2.9.4-cp39-cp39-win_amd64.whl", hash = "sha256:849bd868ae3369932127f0771c08d1109b254f08d48dc42493c3d1b87cb2d308"},
+    {file = "psycopg2-2.9.4.tar.gz", hash = "sha256:d529926254e093a1b669f692a3aa50069bc71faf5b0ecd91686a78f62767d52f"},
 ]
 psycopg2cffi = [
     {file = "psycopg2cffi-2.9.0.tar.gz", hash = "sha256:7e272edcd837de3a1d12b62185eb85c45a19feda9e62fa1b120c54f9e8d35c52"},
@@ -2371,8 +2382,8 @@ pyflakes = [
     {file = "pyflakes-2.4.0.tar.gz", hash = "sha256:05a85c2872edf37a4ed30b0cce2f6093e1d0581f8c19d7393122da7e25b2b24c"},
 ]
 pygithub = [
-    {file = "PyGithub-1.55-py3-none-any.whl", hash = "sha256:2caf0054ea079b71e539741ae56c5a95e073b81fa472ce222e81667381b9601b"},
-    {file = "PyGithub-1.55.tar.gz", hash = "sha256:1bbfff9372047ff3f21d5cd8e07720f3dbfdaf6462fcaed9d815f528f1ba7283"},
+    {file = "PyGithub-1.56-py3-none-any.whl", hash = "sha256:d15f13d82165306da8a68aefc0f848a6f6432d5febbff13b60a94758ce3ef8b5"},
+    {file = "PyGithub-1.56.tar.gz", hash = "sha256:80c6d85cf0f9418ffeb840fd105840af694c4f17e102970badbaf678251f2a01"},
 ]
 pygments = [
     {file = "Pygments-2.11.2-py3-none-any.whl", hash = "sha256:44238f1b60a76d78fc8ca0528ee429702aae011c265fe6a8dd8b63049ae41c65"},
@@ -2684,8 +2695,8 @@ twine = [
     {file = "twine-3.8.0.tar.gz", hash = "sha256:8efa52658e0ae770686a13b675569328f1fba9837e5de1867bfe5f46a9aefe19"},
 ]
 twisted = [
-    {file = "Twisted-22.4.0-py3-none-any.whl", hash = "sha256:f9f7a91f94932477a9fc3b169d57f54f96c6e74a23d78d9ce54039a7f48928a2"},
-    {file = "Twisted-22.4.0.tar.gz", hash = "sha256:a047990f57dfae1e0bd2b7df2526d4f16dcdc843774dc108b78c52f2a5f13680"},
+    {file = "Twisted-22.8.0-py3-none-any.whl", hash = "sha256:8d4718d1e48dcc28933f8beb48dc71cfe77a125e37ad1eb7a3d0acc49baf6c99"},
+    {file = "Twisted-22.8.0.tar.gz", hash = "sha256:e5b60de39f2d1da153fbe1874d885fe3fcbdb21fcc446fa759a53e8fc3513bed"},
 ]
 twisted-iocpsupport = [
     {file = "twisted-iocpsupport-1.0.2.tar.gz", hash = "sha256:72068b206ee809c9c596b57b5287259ea41ddb4774d86725b19f35bf56aa32a9"},
@@ -2732,8 +2743,8 @@ typed-ast = [
     {file = "typed_ast-1.5.2.tar.gz", hash = "sha256:525a2d4088e70a9f75b08b3f87a51acc9cde640e19cc523c7e41aa355564ae27"},
 ]
 types-bleach = [
-    {file = "types-bleach-4.1.4.tar.gz", hash = "sha256:2d30c2c4fb6854088ac636471352c9a51bf6c089289800d2a8060820a01cd43a"},
-    {file = "types_bleach-4.1.4-py3-none-any.whl", hash = "sha256:edffe173ed6d7b6f3543036a96204a9319c3bf6c3645917b14274e43f000cc9b"},
+    {file = "types-bleach-5.0.3.tar.gz", hash = "sha256:f7b3df8278efe176d9670d0f063a66c866c77577f71f54b9c7a320e31b1a7bbd"},
+    {file = "types_bleach-5.0.3-py3-none-any.whl", hash = "sha256:5931525d03571f36b2bb40210c34b662c4d26c8fd6f2b1e1e83fe4d2d2fd63c7"},
 ]
 types-commonmark = [
     {file = "types-commonmark-0.9.2.tar.gz", hash = "sha256:b894b67750c52fd5abc9a40a9ceb9da4652a391d75c1b480bba9cef90f19fc86"},
@@ -2756,12 +2767,12 @@ types-jsonschema = [
     {file = "types_jsonschema-4.4.6-py3-none-any.whl", hash = "sha256:1db9031ca49a8444d01bd2ce8cf2f89318382b04610953b108321e6f8fb03390"},
 ]
 types-opentracing = [
-    {file = "types-opentracing-2.4.7.tar.gz", hash = "sha256:be60e9618355aa892571ace002e6b353702538b1c0dc4fbc1c921219d6658830"},
-    {file = "types_opentracing-2.4.7-py3-none-any.whl", hash = "sha256:861fb8103b07cf717f501dd400cb274ca9992552314d4d6c7a824b11a215e512"},
+    {file = "types-opentracing-2.4.10.tar.gz", hash = "sha256:6101414f3b6d3b9c10f1c510a261e8439b6c8d67c723d5c2872084697b4580a7"},
+    {file = "types_opentracing-2.4.10-py3-none-any.whl", hash = "sha256:66d9cfbbdc4a6f8ca8189a15ad26f0fe41cee84c07057759c5d194e2505b84c2"},
 ]
-types-Pillow = [
-    {file = "types-Pillow-9.2.2.tar.gz", hash = "sha256:6b525b0951ada076f3aefe2347e0bff6231283ce959ad8577a4416604acc673c"},
-    {file = "types_Pillow-9.2.2-py3-none-any.whl", hash = "sha256:bfe14afa1e9047a52b3dc326c93b4f57db72641794e194f11b511f68b0061814"},
+types-pillow = [
+    {file = "types-Pillow-9.2.2.1.tar.gz", hash = "sha256:85c139e06e1c46ec5f9c634d5c54a156b0958d5d0e8be024ed353db0c804b426"},
+    {file = "types_Pillow-9.2.2.1-py3-none-any.whl", hash = "sha256:3a6a871cade8428433a21ef459bb0a65532b87d05f9e836a0664431ce445bdcf"},
 ]
 types-psycopg2 = [
     {file = "types-psycopg2-2.9.21.1.tar.gz", hash = "sha256:f5532cf15afdc6b5ebb1e59b7d896617217321f488fd1fbd74e7efb94decfab6"},
@@ -2780,16 +2791,16 @@ types-requests = [
     {file = "types_requests-2.28.11-py3-none-any.whl", hash = "sha256:af5f55e803cabcfb836dad752bd6d8a0fc8ef1cd84243061c0e27dee04ccf4fd"},
 ]
 types-setuptools = [
-    {file = "types-setuptools-65.4.0.0.tar.gz", hash = "sha256:d9021d6a70690b34e7bd2947e7ab10167c646fbf062508cb56581be2e2a1615e"},
-    {file = "types_setuptools-65.4.0.0-py3-none-any.whl", hash = "sha256:ce178b3f7dbd6c0e67f8eee7ae29c1be280ade7e5188bdd9e620843de4060d85"},
+    {file = "types-setuptools-65.5.0.1.tar.gz", hash = "sha256:5b297081c8f1fbd992cd8b305a97ed96ee6ffc765e9115124029597dd10b8a71"},
+    {file = "types_setuptools-65.5.0.1-py3-none-any.whl", hash = "sha256:601d45b5e9979d2b931de5403aa11153626a1eadd1ce9727b21f24673ced5ceb"},
 ]
 types-urllib3 = [
     {file = "types-urllib3-1.26.10.tar.gz", hash = "sha256:a26898f530e6c3f43f25b907f2b884486868ffd56a9faa94cbf9b3eb6e165d6a"},
     {file = "types_urllib3-1.26.10-py3-none-any.whl", hash = "sha256:d755278d5ecd7a7a6479a190e54230f241f1a99c19b81518b756b19dc69e518c"},
 ]
 typing-extensions = [
-    {file = "typing_extensions-4.1.1-py3-none-any.whl", hash = "sha256:21c85e0fe4b9a155d0799430b0ad741cdce7e359660ccbd8b530613e8df88ce2"},
-    {file = "typing_extensions-4.1.1.tar.gz", hash = "sha256:1a9462dcc3347a79b1f1c0271fbe79e844580bb598bafa1ed208b94da3cdcd42"},
+    {file = "typing_extensions-4.4.0-py3-none-any.whl", hash = "sha256:16fa4864408f655d35ec496218b85f79b3437c829e93320c7c9215ccfd92489e"},
+    {file = "typing_extensions-4.4.0.tar.gz", hash = "sha256:1511434bb92bf8dd198c12b1cc812e800d4181cfcb867674e0f8279cc93087aa"},
 ]
 unpaddedbase64 = [
     {file = "unpaddedbase64-2.1.0-py3-none-any.whl", hash = "sha256:485eff129c30175d2cd6f0cd8d2310dff51e666f7f36175f738d75dfdbd0b1c6"},
diff --git a/pyproject.toml b/pyproject.toml
index 5e36baf40d..6ebac41ed1 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -57,7 +57,7 @@ manifest-path = "rust/Cargo.toml"
 
 [tool.poetry]
 name = "matrix-synapse"
-version = "1.69.0rc2"
+version = "1.70.0rc1"
 description = "Homeserver for the Matrix decentralised comms protocol"
 authors = ["Matrix.org Team and Contributors <packages@matrix.org>"]
 license = "Apache-2.0"
@@ -219,7 +219,7 @@ oidc = ["authlib"]
 # `systemd.journal.JournalHandler`, as is documented in
 # `contrib/systemd/log_config.yaml`.
 systemd = ["systemd-python"]
-url_preview = ["lxml"]
+url-preview = ["lxml"]
 sentry = ["sentry-sdk"]
 opentracing = ["jaeger-client", "opentracing"]
 jwt = ["authlib"]
@@ -227,7 +227,7 @@ jwt = ["authlib"]
 # (if it is not installed, we fall back to slow code.)
 redis = ["txredisapi", "hiredis"]
 # Required to use experimental `caches.track_memory_usage` config option.
-cache_memory = ["pympler"]
+cache-memory = ["pympler"]
 test = ["parameterized", "idna"]
 
 # The duplication here is awful. I hate hate hate hate hate it. However, for now I want
@@ -250,7 +250,7 @@ all = [
     "pysaml2",
     # oidc and jwt
     "authlib",
-    # url_preview
+    # url-preview
     "lxml",
     # sentry
     "sentry-sdk",
@@ -258,7 +258,7 @@ all = [
     "jaeger-client", "opentracing",
     # redis
     "txredisapi", "hiredis",
-    # cache_memory
+    # cache-memory
     "pympler",
     # omitted:
     #   - test: it's useful to have this separate from dev deps in the olddeps job
@@ -267,10 +267,10 @@ all = [
 
 [tool.poetry.dev-dependencies]
 ## We pin black so that our tests don't start failing on new releases.
-isort = "==5.10.1"
-black = "==22.3.0"
+isort = ">=5.10.1"
+black = ">=22.3.0"
 flake8-comprehensions = "*"
-flake8-bugbear = "==21.3.2"
+flake8-bugbear = ">=21.3.2"
 flake8 = "*"
 
 # Typechecking
@@ -296,18 +296,23 @@ parameterized = ">=0.7.4"
 idna = ">=2.5"
 
 # The following are used by the release script
-click = "==8.1.1"
+click = ">=8.1.3"
 # GitPython was == 3.1.14; bumped to 3.1.20, the first release with type hints.
 GitPython = ">=3.1.20"
-commonmark = "==0.9.1"
-pygithub = "==1.55"
+commonmark = ">=0.9.1"
+pygithub = ">=1.55"
 # The following are executed as commands by the release script.
 twine = "*"
 # Towncrier min version comes from #3425. Rationale unclear.
 towncrier = ">=18.6.0rc1"
 
 [build-system]
-requires = ["poetry-core==1.2.0", "setuptools_rust==1.5.2"]
+# The upper bounds here are defensive, intended to prevent situations like
+# #13849 and #14079 where we see buildtime or runtime errors caused by build
+# system changes.
+# We are happy to raise these upper bounds upon request,
+# provided we check that it's safe to do so (i.e. that CI passes).
+requires = ["poetry-core>=1.0.0,<=1.3.2", "setuptools_rust>=1.3,<=1.5.2"]
 build-backend = "poetry.core.masonry.api"
 
 
@@ -316,7 +321,7 @@ build-backend = "poetry.core.masonry.api"
 skip = "cp36* *-musllinux_i686"
 
 # We need a rust compiler
-before-all =  "curl https://sh.rustup.rs -sSf | sh -s -- --default-toolchain stable -y"
+before-all =  "curl https://sh.rustup.rs -sSf | sh -s -- --default-toolchain stable -y --profile minimal"
 environment= { PATH = "$PATH:$HOME/.cargo/bin" }
 
 # For some reason if we don't manually clean the build directory we
diff --git a/rust/src/push/base_rules.rs b/rust/src/push/base_rules.rs
index 2a09cf99ae..63240cacfc 100644
--- a/rust/src/push/base_rules.rs
+++ b/rust/src/push/base_rules.rs
@@ -258,19 +258,6 @@ pub const BASE_APPEND_UNDERRIDE_RULES: &[PushRule] = &[
         default_enabled: true,
     },
     PushRule {
-        rule_id: Cow::Borrowed("global/underride/.org.matrix.msc3772.thread_reply"),
-        priority_class: 1,
-        conditions: Cow::Borrowed(&[Condition::Known(KnownCondition::RelationMatch {
-            rel_type: Cow::Borrowed("m.thread"),
-            event_type_pattern: None,
-            sender: None,
-            sender_type: Some(Cow::Borrowed("user_id")),
-        })]),
-        actions: Cow::Borrowed(&[Action::Notify, HIGHLIGHT_FALSE_ACTION]),
-        default: true,
-        default_enabled: true,
-    },
-    PushRule {
         rule_id: Cow::Borrowed("global/underride/.m.rule.message"),
         priority_class: 1,
         conditions: Cow::Borrowed(&[Condition::Known(KnownCondition::EventMatch(
diff --git a/rust/src/push/evaluator.rs b/rust/src/push/evaluator.rs
index efe88ec76e..0365dd01dc 100644
--- a/rust/src/push/evaluator.rs
+++ b/rust/src/push/evaluator.rs
@@ -12,10 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use std::{
-    borrow::Cow,
-    collections::{BTreeMap, BTreeSet},
-};
+use std::collections::BTreeMap;
 
 use anyhow::{Context, Error};
 use lazy_static::lazy_static;
@@ -49,13 +46,6 @@ pub struct PushRuleEvaluator {
     /// The `notifications` section of the current power levels in the room.
     notification_power_levels: BTreeMap<String, i64>,
 
-    /// The relations related to the event as a mapping from relation type to
-    /// set of sender/event type 2-tuples.
-    relations: BTreeMap<String, BTreeSet<(String, String)>>,
-
-    /// Is running "relation" conditions enabled?
-    relation_match_enabled: bool,
-
     /// The power level of the sender of the event, or None if event is an
     /// outlier.
     sender_power_level: Option<i64>,
@@ -70,8 +60,6 @@ impl PushRuleEvaluator {
         room_member_count: u64,
         sender_power_level: Option<i64>,
         notification_power_levels: BTreeMap<String, i64>,
-        relations: BTreeMap<String, BTreeSet<(String, String)>>,
-        relation_match_enabled: bool,
     ) -> Result<Self, Error> {
         let body = flattened_keys
             .get("content.body")
@@ -83,8 +71,6 @@ impl PushRuleEvaluator {
             body,
             room_member_count,
             notification_power_levels,
-            relations,
-            relation_match_enabled,
             sender_power_level,
         })
     }
@@ -203,89 +189,11 @@ impl PushRuleEvaluator {
                     false
                 }
             }
-            KnownCondition::RelationMatch {
-                rel_type,
-                event_type_pattern,
-                sender,
-                sender_type,
-            } => {
-                self.match_relations(rel_type, sender, sender_type, user_id, event_type_pattern)?
-            }
         };
 
         Ok(result)
     }
 
-    /// Evaluates a relation condition.
-    fn match_relations(
-        &self,
-        rel_type: &str,
-        sender: &Option<Cow<str>>,
-        sender_type: &Option<Cow<str>>,
-        user_id: Option<&str>,
-        event_type_pattern: &Option<Cow<str>>,
-    ) -> Result<bool, Error> {
-        // First check if relation matching is enabled...
-        if !self.relation_match_enabled {
-            return Ok(false);
-        }
-
-        // ... and if there are any relations to match against.
-        let relations = if let Some(relations) = self.relations.get(rel_type) {
-            relations
-        } else {
-            return Ok(false);
-        };
-
-        // Extract the sender pattern from the condition
-        let sender_pattern = if let Some(sender) = sender {
-            Some(sender.as_ref())
-        } else if let Some(sender_type) = sender_type {
-            if sender_type == "user_id" {
-                if let Some(user_id) = user_id {
-                    Some(user_id)
-                } else {
-                    return Ok(false);
-                }
-            } else {
-                warn!("Unrecognized sender_type: {sender_type}");
-                return Ok(false);
-            }
-        } else {
-            None
-        };
-
-        let mut sender_compiled_pattern = if let Some(pattern) = sender_pattern {
-            Some(get_glob_matcher(pattern, GlobMatchType::Whole)?)
-        } else {
-            None
-        };
-
-        let mut type_compiled_pattern = if let Some(pattern) = event_type_pattern {
-            Some(get_glob_matcher(pattern, GlobMatchType::Whole)?)
-        } else {
-            None
-        };
-
-        for (relation_sender, event_type) in relations {
-            if let Some(pattern) = &mut sender_compiled_pattern {
-                if !pattern.is_match(relation_sender)? {
-                    continue;
-                }
-            }
-
-            if let Some(pattern) = &mut type_compiled_pattern {
-                if !pattern.is_match(event_type)? {
-                    continue;
-                }
-            }
-
-            return Ok(true);
-        }
-
-        Ok(false)
-    }
-
     /// Evaluates a `event_match` condition.
     fn match_event_match(
         &self,
@@ -359,15 +267,8 @@ impl PushRuleEvaluator {
 fn push_rule_evaluator() {
     let mut flattened_keys = BTreeMap::new();
     flattened_keys.insert("content.body".to_string(), "foo bar bob hello".to_string());
-    let evaluator = PushRuleEvaluator::py_new(
-        flattened_keys,
-        10,
-        Some(0),
-        BTreeMap::new(),
-        BTreeMap::new(),
-        true,
-    )
-    .unwrap();
+    let evaluator =
+        PushRuleEvaluator::py_new(flattened_keys, 10, Some(0), BTreeMap::new()).unwrap();
 
     let result = evaluator.run(&FilteredPushRules::default(), None, Some("bob"));
     assert_eq!(result.len(), 3);
diff --git a/rust/src/push/mod.rs b/rust/src/push/mod.rs
index 208b9c0d73..0dabfab8b8 100644
--- a/rust/src/push/mod.rs
+++ b/rust/src/push/mod.rs
@@ -275,16 +275,6 @@ pub enum KnownCondition {
     SenderNotificationPermission {
         key: Cow<'static, str>,
     },
-    #[serde(rename = "org.matrix.msc3772.relation_match")]
-    RelationMatch {
-        rel_type: Cow<'static, str>,
-        #[serde(skip_serializing_if = "Option::is_none", rename = "type")]
-        event_type_pattern: Option<Cow<'static, str>>,
-        #[serde(skip_serializing_if = "Option::is_none")]
-        sender: Option<Cow<'static, str>>,
-        #[serde(skip_serializing_if = "Option::is_none")]
-        sender_type: Option<Cow<'static, str>>,
-    },
 }
 
 impl IntoPy<PyObject> for Condition {
@@ -401,21 +391,15 @@ impl PushRules {
 pub struct FilteredPushRules {
     push_rules: PushRules,
     enabled_map: BTreeMap<String, bool>,
-    msc3772_enabled: bool,
 }
 
 #[pymethods]
 impl FilteredPushRules {
     #[new]
-    pub fn py_new(
-        push_rules: PushRules,
-        enabled_map: BTreeMap<String, bool>,
-        msc3772_enabled: bool,
-    ) -> Self {
+    pub fn py_new(push_rules: PushRules, enabled_map: BTreeMap<String, bool>) -> Self {
         Self {
             push_rules,
             enabled_map,
-            msc3772_enabled,
         }
     }
 
@@ -430,25 +414,13 @@ impl FilteredPushRules {
     /// Iterates over all the rules and their enabled state, including base
     /// rules, in the order they should be executed in.
     fn iter(&self) -> impl Iterator<Item = (&PushRule, bool)> {
-        self.push_rules
-            .iter()
-            .filter(|rule| {
-                // Ignore disabled experimental push rules
-                if !self.msc3772_enabled
-                    && rule.rule_id == "global/underride/.org.matrix.msc3772.thread_reply"
-                {
-                    return false;
-                }
-
-                true
-            })
-            .map(|r| {
-                let enabled = *self
-                    .enabled_map
-                    .get(&*r.rule_id)
-                    .unwrap_or(&r.default_enabled);
-                (r, enabled)
-            })
+        self.push_rules.iter().map(|r| {
+            let enabled = *self
+                .enabled_map
+                .get(&*r.rule_id)
+                .unwrap_or(&r.default_enabled);
+            (r, enabled)
+        })
     }
 }
 
diff --git a/scripts-dev/complement.sh b/scripts-dev/complement.sh
index eab23f18f1..a7b1e1e3a8 100755
--- a/scripts-dev/complement.sh
+++ b/scripts-dev/complement.sh
@@ -126,7 +126,7 @@ export COMPLEMENT_BASE_IMAGE=complement-synapse
 
 extra_test_args=()
 
-test_tags="synapse_blacklist,msc2716,msc3030,msc3787"
+test_tags="synapse_blacklist,msc3787"
 
 # All environment variables starting with PASS_ will be shared.
 # (The prefix is stripped off before reaching the container.)
@@ -158,7 +158,10 @@ else
 
   # We only test faster room joins on monoliths, because they are purposefully
   # being developed without worker support to start with.
-  test_tags="$test_tags,faster_joins"
+  #
+  # The tests for importing historical messages (MSC2716) and jump to date (MSC3030)
+  # also only pass with monoliths, currently.
+  test_tags="$test_tags,faster_joins,msc2716,msc3030"
 fi
 
 
diff --git a/stubs/synapse/synapse_rust/push.pyi b/stubs/synapse/synapse_rust/push.pyi
index 5900e61450..f2a61df660 100644
--- a/stubs/synapse/synapse_rust/push.pyi
+++ b/stubs/synapse/synapse_rust/push.pyi
@@ -25,9 +25,7 @@ class PushRules:
     def rules(self) -> Collection[PushRule]: ...
 
 class FilteredPushRules:
-    def __init__(
-        self, push_rules: PushRules, enabled_map: Dict[str, bool], msc3772_enabled: bool
-    ): ...
+    def __init__(self, push_rules: PushRules, enabled_map: Dict[str, bool]): ...
     def rules(self) -> Collection[Tuple[PushRule, bool]]: ...
 
 def get_base_rule_ids() -> Collection[str]: ...
@@ -39,8 +37,6 @@ class PushRuleEvaluator:
         room_member_count: int,
         sender_power_level: Optional[int],
         notification_power_levels: Mapping[str, int],
-        relations: Mapping[str, Set[Tuple[str, str]]],
-        relation_match_enabled: bool,
     ): ...
     def run(
         self,
diff --git a/synapse/_scripts/synapse_port_db.py b/synapse/_scripts/synapse_port_db.py
index 5fa599e70e..d850e54e17 100755
--- a/synapse/_scripts/synapse_port_db.py
+++ b/synapse/_scripts/synapse_port_db.py
@@ -72,6 +72,7 @@ from synapse.storage.databases.main.registration import (
     RegistrationBackgroundUpdateStore,
     find_max_generated_user_id_localpart,
 )
+from synapse.storage.databases.main.relations import RelationsWorkerStore
 from synapse.storage.databases.main.room import RoomBackgroundUpdateStore
 from synapse.storage.databases.main.roommember import RoomMemberBackgroundUpdateStore
 from synapse.storage.databases.main.search import SearchBackgroundUpdateStore
@@ -206,6 +207,7 @@ class Store(
     PusherWorkerStore,
     PresenceBackgroundUpdateStore,
     ReceiptsBackgroundUpdateStore,
+    RelationsWorkerStore,
 ):
     def execute(self, f: Callable[..., R], *args: Any, **kwargs: Any) -> Awaitable[R]:
         return self.db_pool.runInteraction(f.__name__, f, *args, **kwargs)
diff --git a/synapse/_scripts/update_synapse_database.py b/synapse/_scripts/update_synapse_database.py
index fb1fb83f50..0adf94bba6 100755..100644
--- a/synapse/_scripts/update_synapse_database.py
+++ b/synapse/_scripts/update_synapse_database.py
@@ -15,7 +15,6 @@
 
 import argparse
 import logging
-import sys
 from typing import cast
 
 import yaml
@@ -100,13 +99,6 @@ def main() -> None:
     # Load, process and sanity-check the config.
     hs_config = yaml.safe_load(args.database_config)
 
-    if "database" not in hs_config and "databases" not in hs_config:
-        sys.stderr.write(
-            "The configuration file must have a 'database' or 'databases' section. "
-            "See https://matrix-org.github.io/synapse/latest/usage/configuration/config_documentation.html#database"
-        )
-        sys.exit(4)
-
     config = HomeServerConfig()
     config.parse_config_dict(hs_config, "", "")
 
diff --git a/synapse/api/errors.py b/synapse/api/errors.py
index c606207569..400dd12aba 100644
--- a/synapse/api/errors.py
+++ b/synapse/api/errors.py
@@ -155,7 +155,13 @@ class RedirectException(CodeMessageException):
 
 class SynapseError(CodeMessageException):
     """A base exception type for matrix errors which have an errcode and error
-    message (as well as an HTTP status code).
+    message (as well as an HTTP status code). These often bubble all the way up to the
+    client API response so the error code and status often reach the client directly as
+    defined here. If the error doesn't make sense to present to a client, then it
+    probably shouldn't be a `SynapseError`. For example, if we contact another
+    homeserver over federation, we shouldn't automatically ferry response errors back to
+    the client on our end (a 500 from a remote server does not make sense to a client
+    when our server did not experience a 500).
 
     Attributes:
         errcode: Matrix error code e.g 'M_FORBIDDEN'
@@ -600,8 +606,20 @@ def cs_error(msg: str, code: str = Codes.UNKNOWN, **kwargs: Any) -> "JsonDict":
 
 
 class FederationError(RuntimeError):
-    """This class is used to inform remote homeservers about erroneous
-    PDUs they sent us.
+    """
+    Raised when we process an erroneous PDU.
+
+    There are two kinds of scenarios where this exception can be raised:
+
+    1. We may pull an invalid PDU from a remote homeserver (e.g. during backfill). We
+       raise this exception to signal an error to the rest of the application.
+    2. We may be pushed an invalid PDU as part of a `/send` transaction from a remote
+       homeserver. We raise so that we can respond to the transaction and include the
+       error string in the "PDU Processing Result". The message which will likely be
+       ignored by the remote homeserver and is not machine parse-able since it's just a
+       string.
+
+    TODO: In the future, we should split these usage scenarios into their own error types.
 
     FATAL: The remote server could not interpret the source event.
         (e.g., it was missing a required field)
@@ -640,6 +658,27 @@ class FederationError(RuntimeError):
         }
 
 
+class FederationPullAttemptBackoffError(RuntimeError):
+    """
+    Raised to indicate that we are are deliberately not attempting to pull the given
+    event over federation because we've already done so recently and are backing off.
+
+    Attributes:
+        event_id: The event_id which we are refusing to pull
+        message: A custom error message that gives more context
+    """
+
+    def __init__(self, event_ids: List[str], message: Optional[str]):
+        self.event_ids = event_ids
+
+        if message:
+            error_message = message
+        else:
+            error_message = f"Not attempting to pull event_ids={self.event_ids} because we already tried to pull them recently (backing off)."
+
+        super().__init__(error_message)
+
+
 class HttpResponseException(CodeMessageException):
     """
     Represents an HTTP-level failure of an outbound request
diff --git a/synapse/api/filtering.py b/synapse/api/filtering.py
index cc31cf8cc7..26be377d03 100644
--- a/synapse/api/filtering.py
+++ b/synapse/api/filtering.py
@@ -36,7 +36,7 @@ from jsonschema import FormatChecker
 from synapse.api.constants import EduTypes, EventContentFields
 from synapse.api.errors import SynapseError
 from synapse.api.presence import UserPresenceState
-from synapse.events import EventBase
+from synapse.events import EventBase, relation_from_event
 from synapse.types import JsonDict, RoomID, UserID
 
 if TYPE_CHECKING:
@@ -53,6 +53,12 @@ FILTER_SCHEMA = {
         # check types are valid event types
         "types": {"type": "array", "items": {"type": "string"}},
         "not_types": {"type": "array", "items": {"type": "string"}},
+        # MSC3874, filtering /messages.
+        "org.matrix.msc3874.rel_types": {"type": "array", "items": {"type": "string"}},
+        "org.matrix.msc3874.not_rel_types": {
+            "type": "array",
+            "items": {"type": "string"},
+        },
     },
 }
 
@@ -334,8 +340,15 @@ class Filter:
         self.labels = filter_json.get("org.matrix.labels", None)
         self.not_labels = filter_json.get("org.matrix.not_labels", [])
 
-        self.related_by_senders = self.filter_json.get("related_by_senders", None)
-        self.related_by_rel_types = self.filter_json.get("related_by_rel_types", None)
+        self.related_by_senders = filter_json.get("related_by_senders", None)
+        self.related_by_rel_types = filter_json.get("related_by_rel_types", None)
+
+        # For compatibility with _check_fields.
+        self.rel_types = None
+        self.not_rel_types = []
+        if hs.config.experimental.msc3874_enabled:
+            self.rel_types = filter_json.get("org.matrix.msc3874.rel_types", None)
+            self.not_rel_types = filter_json.get("org.matrix.msc3874.not_rel_types", [])
 
     def filters_all_types(self) -> bool:
         return "*" in self.not_types
@@ -386,11 +399,19 @@ class Filter:
             # check if there is a string url field in the content for filtering purposes
             labels = content.get(EventContentFields.LABELS, [])
 
+            # Check if the event has a relation.
+            rel_type = None
+            if isinstance(event, EventBase):
+                relation = relation_from_event(event)
+                if relation:
+                    rel_type = relation.rel_type
+
             field_matchers = {
                 "rooms": lambda v: room_id == v,
                 "senders": lambda v: sender == v,
                 "types": lambda v: _matches_wildcard(ev_type, v),
                 "labels": lambda v: v in labels,
+                "rel_types": lambda v: rel_type == v,
             }
 
             result = self._check_fields(field_matchers)
diff --git a/synapse/api/urls.py b/synapse/api/urls.py
index bd49fa6a5f..a918579f50 100644
--- a/synapse/api/urls.py
+++ b/synapse/api/urls.py
@@ -28,7 +28,7 @@ FEDERATION_V1_PREFIX = FEDERATION_PREFIX + "/v1"
 FEDERATION_V2_PREFIX = FEDERATION_PREFIX + "/v2"
 FEDERATION_UNSTABLE_PREFIX = FEDERATION_PREFIX + "/unstable"
 STATIC_PREFIX = "/_matrix/static"
-SERVER_KEY_V2_PREFIX = "/_matrix/key/v2"
+SERVER_KEY_PREFIX = "/_matrix/key"
 MEDIA_R0_PREFIX = "/_matrix/media/r0"
 MEDIA_V3_PREFIX = "/_matrix/media/v3"
 LEGACY_MEDIA_PREFIX = "/_matrix/media/v1"
diff --git a/synapse/app/generic_worker.py b/synapse/app/generic_worker.py
index 5e3825fca6..2a9f039367 100644
--- a/synapse/app/generic_worker.py
+++ b/synapse/app/generic_worker.py
@@ -28,7 +28,7 @@ from synapse.api.urls import (
     LEGACY_MEDIA_PREFIX,
     MEDIA_R0_PREFIX,
     MEDIA_V3_PREFIX,
-    SERVER_KEY_V2_PREFIX,
+    SERVER_KEY_PREFIX,
 )
 from synapse.app import _base
 from synapse.app._base import (
@@ -65,6 +65,7 @@ from synapse.rest.client import (
     push_rule,
     read_marker,
     receipts,
+    relations,
     room,
     room_batch,
     room_keys,
@@ -88,7 +89,7 @@ from synapse.rest.client.register import (
     RegistrationTokenValidityRestServlet,
 )
 from synapse.rest.health import HealthResource
-from synapse.rest.key.v2 import KeyApiV2Resource
+from synapse.rest.key.v2 import KeyResource
 from synapse.rest.synapse.client import build_synapse_client_resource_tree
 from synapse.rest.well_known import well_known_resource
 from synapse.server import HomeServer
@@ -308,6 +309,7 @@ class GenericWorkerServer(HomeServer):
                     sync.register_servlets(self, resource)
                     events.register_servlets(self, resource)
                     room.register_servlets(self, resource, is_worker=True)
+                    relations.register_servlets(self, resource)
                     room.register_deprecated_servlets(self, resource)
                     initial_sync.register_servlets(self, resource)
                     room_batch.register_servlets(self, resource)
@@ -323,13 +325,13 @@ class GenericWorkerServer(HomeServer):
 
                     presence.register_servlets(self, resource)
 
-                    resources.update({CLIENT_API_PREFIX: resource})
+                    resources[CLIENT_API_PREFIX] = resource
 
                     resources.update(build_synapse_client_resource_tree(self))
-                    resources.update({"/.well-known": well_known_resource(self)})
+                    resources["/.well-known"] = well_known_resource(self)
 
                 elif name == "federation":
-                    resources.update({FEDERATION_PREFIX: TransportLayerServer(self)})
+                    resources[FEDERATION_PREFIX] = TransportLayerServer(self)
                 elif name == "media":
                     if self.config.media.can_load_media_repo:
                         media_repo = self.get_media_repository_resource()
@@ -357,16 +359,12 @@ class GenericWorkerServer(HomeServer):
                     # Only load the openid resource separately if federation resource
                     # is not specified since federation resource includes openid
                     # resource.
-                    resources.update(
-                        {
-                            FEDERATION_PREFIX: TransportLayerServer(
-                                self, servlet_groups=["openid"]
-                            )
-                        }
+                    resources[FEDERATION_PREFIX] = TransportLayerServer(
+                        self, servlet_groups=["openid"]
                     )
 
                 if name in ["keys", "federation"]:
-                    resources[SERVER_KEY_V2_PREFIX] = KeyApiV2Resource(self)
+                    resources[SERVER_KEY_PREFIX] = KeyResource(self)
 
                 if name == "replication":
                     resources[REPLICATION_PREFIX] = ReplicationRestResource(self)
diff --git a/synapse/app/homeserver.py b/synapse/app/homeserver.py
index 883f2fd2ec..de3f08876f 100644
--- a/synapse/app/homeserver.py
+++ b/synapse/app/homeserver.py
@@ -31,7 +31,7 @@ from synapse.api.urls import (
     LEGACY_MEDIA_PREFIX,
     MEDIA_R0_PREFIX,
     MEDIA_V3_PREFIX,
-    SERVER_KEY_V2_PREFIX,
+    SERVER_KEY_PREFIX,
     STATIC_PREFIX,
 )
 from synapse.app import _base
@@ -60,7 +60,7 @@ from synapse.replication.http import REPLICATION_PREFIX, ReplicationRestResource
 from synapse.rest import ClientRestResource
 from synapse.rest.admin import AdminRestResource
 from synapse.rest.health import HealthResource
-from synapse.rest.key.v2 import KeyApiV2Resource
+from synapse.rest.key.v2 import KeyResource
 from synapse.rest.synapse.client import build_synapse_client_resource_tree
 from synapse.rest.well_known import well_known_resource
 from synapse.server import HomeServer
@@ -215,30 +215,22 @@ class SynapseHomeServer(HomeServer):
             consent_resource: Resource = ConsentResource(self)
             if compress:
                 consent_resource = gz_wrap(consent_resource)
-            resources.update({"/_matrix/consent": consent_resource})
+            resources["/_matrix/consent"] = consent_resource
 
         if name == "federation":
             federation_resource: Resource = TransportLayerServer(self)
             if compress:
                 federation_resource = gz_wrap(federation_resource)
-            resources.update({FEDERATION_PREFIX: federation_resource})
+            resources[FEDERATION_PREFIX] = federation_resource
 
         if name == "openid":
-            resources.update(
-                {
-                    FEDERATION_PREFIX: TransportLayerServer(
-                        self, servlet_groups=["openid"]
-                    )
-                }
+            resources[FEDERATION_PREFIX] = TransportLayerServer(
+                self, servlet_groups=["openid"]
             )
 
         if name in ["static", "client"]:
-            resources.update(
-                {
-                    STATIC_PREFIX: StaticResource(
-                        os.path.join(os.path.dirname(synapse.__file__), "static")
-                    )
-                }
+            resources[STATIC_PREFIX] = StaticResource(
+                os.path.join(os.path.dirname(synapse.__file__), "static")
             )
 
         if name in ["media", "federation", "client"]:
@@ -257,7 +249,7 @@ class SynapseHomeServer(HomeServer):
                 )
 
         if name in ["keys", "federation"]:
-            resources[SERVER_KEY_V2_PREFIX] = KeyApiV2Resource(self)
+            resources[SERVER_KEY_PREFIX] = KeyResource(self)
 
         if name == "metrics" and self.config.metrics.enable_metrics:
             metrics_resource: Resource = MetricsResource(RegistryProxy)
diff --git a/synapse/config/cache.py b/synapse/config/cache.py
index 2db8cfb005..eb4194a5a9 100644
--- a/synapse/config/cache.py
+++ b/synapse/config/cache.py
@@ -159,7 +159,7 @@ class CacheConfig(Config):
 
         self.track_memory_usage = cache_config.get("track_memory_usage", False)
         if self.track_memory_usage:
-            check_requirements("cache_memory")
+            check_requirements("cache-memory")
 
         expire_caches = cache_config.get("expire_caches", True)
         cache_entry_ttl = cache_config.get("cache_entry_ttl", "30m")
diff --git a/synapse/config/experimental.py b/synapse/config/experimental.py
index e00cb7096c..4009add01d 100644
--- a/synapse/config/experimental.py
+++ b/synapse/config/experimental.py
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import Any
+from typing import Any, Optional
 
 import attr
 
@@ -95,8 +95,6 @@ class ExperimentalConfig(Config):
         # MSC2815 (allow room moderators to view redacted event content)
         self.msc2815_enabled: bool = experimental.get("msc2815_enabled", False)
 
-        # MSC3772: A push rule for mutual relations.
-        self.msc3772_enabled: bool = experimental.get("msc3772_enabled", False)
         # MSC3773: Thread notifications
         self.msc3773_enabled: bool = experimental.get("msc3773_enabled", False)
 
@@ -119,3 +117,11 @@ class ExperimentalConfig(Config):
         self.msc3882_token_timeout = self.parse_duration(
             experimental.get("msc3882_token_timeout", "5m")
         )
+
+        # MSC3874: Filtering /messages with rel_types / not_rel_types.
+        self.msc3874_enabled: bool = experimental.get("msc3874_enabled", False)
+
+        # MSC3886: Simple client rendezvous capability
+        self.msc3886_endpoint: Optional[str] = experimental.get(
+            "msc3886_endpoint", None
+        )
diff --git a/synapse/config/groups.py b/synapse/config/groups.py
deleted file mode 100644
index baa051fdd4..0000000000
--- a/synapse/config/groups.py
+++ /dev/null
@@ -1,27 +0,0 @@
-# Copyright 2017 New Vector Ltd
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-from typing import Any
-
-from synapse.types import JsonDict
-
-from ._base import Config
-
-
-class GroupsConfig(Config):
-    section = "groups"
-
-    def read_config(self, config: JsonDict, **kwargs: Any) -> None:
-        self.enable_group_creation = config.get("enable_group_creation", False)
-        self.group_creation_prefix = config.get("group_creation_prefix", "")
diff --git a/synapse/config/repository.py b/synapse/config/repository.py
index 1033496bb4..e4759711ed 100644
--- a/synapse/config/repository.py
+++ b/synapse/config/repository.py
@@ -205,7 +205,7 @@ class ContentRepositoryConfig(Config):
         )
         self.url_preview_enabled = config.get("url_preview_enabled", False)
         if self.url_preview_enabled:
-            check_requirements("url_preview")
+            check_requirements("url-preview")
 
             proxy_env = getproxies_environment()
             if "url_preview_ip_range_blacklist" not in config:
diff --git a/synapse/config/server.py b/synapse/config/server.py
index f2353ce5fb..ec46ca63ad 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -207,6 +207,9 @@ class HttpListenerConfig:
     additional_resources: Dict[str, dict] = attr.Factory(dict)
     tag: Optional[str] = None
     request_id_header: Optional[str] = None
+    # If true, the listener will return CORS response headers compatible with MSC3886:
+    # https://github.com/matrix-org/matrix-spec-proposals/pull/3886
+    experimental_cors_msc3886: bool = False
 
 
 @attr.s(slots=True, frozen=True, auto_attribs=True)
@@ -935,6 +938,7 @@ def parse_listener_def(num: int, listener: Any) -> ListenerConfig:
             additional_resources=listener.get("additional_resources", {}),
             tag=listener.get("tag"),
             request_id_header=listener.get("request_id_header"),
+            experimental_cors_msc3886=listener.get("experimental_cors_msc3886", False),
         )
 
     return ListenerConfig(port, bind_addresses, listener_type, tls, http_config)
diff --git a/synapse/event_auth.py b/synapse/event_auth.py
index c7d5ef92fc..bab31e33c5 100644
--- a/synapse/event_auth.py
+++ b/synapse/event_auth.py
@@ -15,7 +15,18 @@
 
 import logging
 import typing
-from typing import Any, Collection, Dict, Iterable, List, Optional, Set, Tuple, Union
+from typing import (
+    Any,
+    Collection,
+    Dict,
+    Iterable,
+    List,
+    Mapping,
+    Optional,
+    Set,
+    Tuple,
+    Union,
+)
 
 from canonicaljson import encode_canonical_json
 from signedjson.key import decode_verify_key_bytes
@@ -134,6 +145,7 @@ def validate_event_for_room_version(event: "EventBase") -> None:
 async def check_state_independent_auth_rules(
     store: _EventSourceStore,
     event: "EventBase",
+    batched_auth_events: Optional[Mapping[str, "EventBase"]] = None,
 ) -> None:
     """Check that an event complies with auth rules that are independent of room state
 
@@ -143,6 +155,8 @@ async def check_state_independent_auth_rules(
     Args:
         store: the datastore; used to fetch the auth events for validation
         event: the event being checked.
+        batched_auth_events: if the event being authed is part of a batch, any events
+            from the same batch that may be necessary to auth the current event
 
     Raises:
         AuthError if the checks fail
@@ -162,6 +176,9 @@ async def check_state_independent_auth_rules(
         redact_behaviour=EventRedactBehaviour.as_is,
         allow_rejected=True,
     )
+    if batched_auth_events:
+        auth_events.update(batched_auth_events)
+
     room_id = event.room_id
     auth_dict: MutableStateMap[str] = {}
     expected_auth_types = auth_types_for_event(event.room_version, event)
diff --git a/synapse/events/snapshot.py b/synapse/events/snapshot.py
index 826a84894e..14ac875ce0 100644
--- a/synapse/events/snapshot.py
+++ b/synapse/events/snapshot.py
@@ -65,7 +65,8 @@ class EventContext:
             None does not necessarily mean that ``state_group`` does not have
             a prev_group!
 
-            If the event is a state event, this is normally the same as ``prev_group``.
+            If the event is a state event, this is normally the same as
+            ``state_group_before_event``.
 
             If ``state_group`` is None (ie, the event is an outlier), ``prev_group``
             will always also be ``None``.
diff --git a/synapse/federation/federation_client.py b/synapse/federation/federation_client.py
index 4dca711cd2..b220ab43fc 100644
--- a/synapse/federation/federation_client.py
+++ b/synapse/federation/federation_client.py
@@ -1294,7 +1294,7 @@ class FederationClient(FederationBase):
         return resp[1]
 
     async def send_knock(self, destinations: List[str], pdu: EventBase) -> JsonDict:
-        """Attempts to send a knock event to given a list of servers. Iterates
+        """Attempts to send a knock event to a given list of servers. Iterates
         through the list until one attempt succeeds.
 
         Doing so will cause the remote server to add the event to the graph,
diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index 907940e19e..59e351595b 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -481,6 +481,14 @@ class FederationServer(FederationBase):
                     pdu_results[pdu.event_id] = await process_pdu(pdu)
 
         async def process_pdu(pdu: EventBase) -> JsonDict:
+            """
+            Processes a pushed PDU sent to us via a `/send` transaction
+
+            Returns:
+                JsonDict representing a "PDU Processing Result" that will be bundled up
+                with the other processed PDU's in the `/send` transaction and sent back
+                to remote homeserver.
+            """
             event_id = pdu.event_id
             with nested_logging_context(event_id):
                 try:
@@ -824,7 +832,14 @@ class FederationServer(FederationBase):
                 context, self._room_prejoin_state_types
             )
         )
-        return {"knock_state_events": stripped_room_state}
+        return {
+            "knock_room_state": stripped_room_state,
+            # Since v1.37, Synapse incorrectly used "knock_state_events" for this field.
+            # Thus, we also populate a 'knock_state_events' with the same content to
+            # support old instances.
+            # See https://github.com/matrix-org/synapse/issues/14088.
+            "knock_state_events": stripped_room_state,
+        }
 
     async def _on_send_membership_event(
         self, origin: str, content: JsonDict, membership_type: str, room_id: str
diff --git a/synapse/federation/sender/__init__.py b/synapse/federation/sender/__init__.py
index a6cb3ba58f..774ecd81b6 100644
--- a/synapse/federation/sender/__init__.py
+++ b/synapse/federation/sender/__init__.py
@@ -353,21 +353,25 @@ class FederationSender(AbstractFederationSender):
                 last_token = await self.store.get_federation_out_pos("events")
                 (
                     next_token,
-                    events,
                     event_to_received_ts,
-                ) = await self.store.get_all_new_events_stream(
+                ) = await self.store.get_all_new_event_ids_stream(
                     last_token, self._last_poked_id, limit=100
                 )
 
+                event_ids = event_to_received_ts.keys()
+                event_entries = await self.store.get_unredacted_events_from_cache_or_db(
+                    event_ids
+                )
+
                 logger.debug(
                     "Handling %i -> %i: %i events to send (current id %i)",
                     last_token,
                     next_token,
-                    len(events),
+                    len(event_entries),
                     self._last_poked_id,
                 )
 
-                if not events and next_token >= self._last_poked_id:
+                if not event_entries and next_token >= self._last_poked_id:
                     logger.debug("All events processed")
                     break
 
@@ -508,8 +512,14 @@ class FederationSender(AbstractFederationSender):
                             await handle_event(event)
 
                 events_by_room: Dict[str, List[EventBase]] = {}
-                for event in events:
-                    events_by_room.setdefault(event.room_id, []).append(event)
+
+                for event_id in event_ids:
+                    # `event_entries` is unsorted, so we have to iterate over `event_ids`
+                    # to ensure the events are in the right order
+                    event_cache = event_entries.get(event_id)
+                    if event_cache:
+                        event = event_cache.event
+                        events_by_room.setdefault(event.room_id, []).append(event)
 
                 await make_deferred_yieldable(
                     defer.gatherResults(
@@ -524,9 +534,10 @@ class FederationSender(AbstractFederationSender):
                 logger.debug("Successfully handled up to %i", next_token)
                 await self.store.update_federation_out_pos("events", next_token)
 
-                if events:
+                if event_entries:
                     now = self.clock.time_msec()
-                    ts = event_to_received_ts[events[-1].event_id]
+                    last_id = next(reversed(event_ids))
+                    ts = event_to_received_ts[last_id]
                     assert ts is not None
 
                     synapse.metrics.event_processing_lag.labels(
@@ -536,7 +547,7 @@ class FederationSender(AbstractFederationSender):
                         "federation_sender"
                     ).set(ts)
 
-                    events_processed_counter.inc(len(events))
+                    events_processed_counter.inc(len(event_entries))
 
                     event_processing_loop_room_count.labels("federation_sender").inc(
                         len(events_by_room)
diff --git a/synapse/federation/transport/server/federation.py b/synapse/federation/transport/server/federation.py
index 6bb4659c4c..205fd16daa 100644
--- a/synapse/federation/transport/server/federation.py
+++ b/synapse/federation/transport/server/federation.py
@@ -489,7 +489,7 @@ class FederationV2InviteServlet(BaseFederationServerServlet):
 
         room_version = content["room_version"]
         event = content["event"]
-        invite_room_state = content["invite_room_state"]
+        invite_room_state = content.get("invite_room_state", [])
 
         # Synapse expects invite_room_state to be in unsigned, as it is in v1
         # API
@@ -499,6 +499,11 @@ class FederationV2InviteServlet(BaseFederationServerServlet):
         result = await self.handler.on_invite_request(
             origin, event, room_version_id=room_version
         )
+
+        # We only store invite_room_state for internal use, so remove it before
+        # returning the event to the remote homeserver.
+        result["event"].get("unsigned", {}).pop("invite_room_state", None)
+
         return 200, result
 
 
diff --git a/synapse/handlers/account_data.py b/synapse/handlers/account_data.py
index 0478448b47..fc21d58001 100644
--- a/synapse/handlers/account_data.py
+++ b/synapse/handlers/account_data.py
@@ -225,7 +225,7 @@ class AccountDataEventSource(EventSource[int, JsonDict]):
         self,
         user: UserID,
         from_key: int,
-        limit: Optional[int],
+        limit: int,
         room_ids: Collection[str],
         is_guest: bool,
         explicit_room_id: Optional[str] = None,
diff --git a/synapse/handlers/appservice.py b/synapse/handlers/appservice.py
index 203b62e015..66f5b8d108 100644
--- a/synapse/handlers/appservice.py
+++ b/synapse/handlers/appservice.py
@@ -109,10 +109,13 @@ class ApplicationServicesHandler:
                     last_token = await self.store.get_appservice_last_pos()
                     (
                         upper_bound,
-                        events,
                         event_to_received_ts,
-                    ) = await self.store.get_all_new_events_stream(
-                        last_token, self.current_max, limit=100, get_prev_content=True
+                    ) = await self.store.get_all_new_event_ids_stream(
+                        last_token, self.current_max, limit=100
+                    )
+
+                    events = await self.store.get_events_as_list(
+                        event_to_received_ts.keys(), get_prev_content=True
                     )
 
                     events_by_room: Dict[str, List[EventBase]] = {}
diff --git a/synapse/handlers/device.py b/synapse/handlers/device.py
index f9cc5bddbc..c597639a7f 100644
--- a/synapse/handlers/device.py
+++ b/synapse/handlers/device.py
@@ -937,7 +937,10 @@ class DeviceListUpdater:
         # Check if we are partially joining any rooms. If so we need to store
         # all device list updates so that we can handle them correctly once we
         # know who is in the room.
-        partial_rooms = await self.store.get_partial_state_rooms_and_servers()
+        # TODO(faster joins): this fetches and processes a bunch of data that we don't
+        # use. Could be replaced by a tighter query e.g.
+        #   SELECT EXISTS(SELECT 1 FROM partial_state_rooms)
+        partial_rooms = await self.store.get_partial_state_room_resync_info()
         if partial_rooms:
             await self.store.add_remote_device_list_to_pending(
                 user_id,
diff --git a/synapse/handlers/directory.py b/synapse/handlers/directory.py
index 7127d5aefc..d52ebada6b 100644
--- a/synapse/handlers/directory.py
+++ b/synapse/handlers/directory.py
@@ -16,6 +16,8 @@ import logging
 import string
 from typing import TYPE_CHECKING, Iterable, List, Optional
 
+from typing_extensions import Literal
+
 from synapse.api.constants import MAX_ALIAS_LENGTH, EventTypes
 from synapse.api.errors import (
     AuthError,
@@ -429,7 +431,10 @@ class DirectoryHandler:
         return await self.auth.check_can_change_room_list(room_id, requester)
 
     async def edit_published_room_list(
-        self, requester: Requester, room_id: str, visibility: str
+        self,
+        requester: Requester,
+        room_id: str,
+        visibility: Literal["public", "private"],
     ) -> None:
         """Edit the entry of the room in the published room list.
 
@@ -451,9 +456,6 @@ class DirectoryHandler:
         if requester.is_guest:
             raise AuthError(403, "Guests cannot edit the published room list")
 
-        if visibility not in ["public", "private"]:
-            raise SynapseError(400, "Invalid visibility setting")
-
         if visibility == "public" and not self.enable_room_list_search:
             # The room list has been disabled.
             raise AuthError(
@@ -505,7 +507,11 @@ class DirectoryHandler:
         await self.store.set_room_is_public(room_id, making_public)
 
     async def edit_published_appservice_room_list(
-        self, appservice_id: str, network_id: str, room_id: str, visibility: str
+        self,
+        appservice_id: str,
+        network_id: str,
+        room_id: str,
+        visibility: Literal["public", "private"],
     ) -> None:
         """Add or remove a room from the appservice/network specific public
         room list.
@@ -516,9 +522,6 @@ class DirectoryHandler:
             room_id
             visibility: either "public" or "private"
         """
-        if visibility not in ["public", "private"]:
-            raise SynapseError(400, "Invalid visibility setting")
-
         await self.store.set_room_is_public_appservice(
             room_id, appservice_id, network_id, visibility == "public"
         )
diff --git a/synapse/handlers/event_auth.py b/synapse/handlers/event_auth.py
index 8249ca1ed2..3bbad0271b 100644
--- a/synapse/handlers/event_auth.py
+++ b/synapse/handlers/event_auth.py
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import logging
-from typing import TYPE_CHECKING, Collection, List, Optional, Union
+from typing import TYPE_CHECKING, Collection, List, Mapping, Optional, Union
 
 from synapse import event_auth
 from synapse.api.constants import (
@@ -29,7 +29,6 @@ from synapse.event_auth import (
 )
 from synapse.events import EventBase
 from synapse.events.builder import EventBuilder
-from synapse.events.snapshot import EventContext
 from synapse.types import StateMap, get_domain_from_id
 
 if TYPE_CHECKING:
@@ -51,12 +50,21 @@ class EventAuthHandler:
     async def check_auth_rules_from_context(
         self,
         event: EventBase,
-        context: EventContext,
+        batched_auth_events: Optional[Mapping[str, EventBase]] = None,
     ) -> None:
-        """Check an event passes the auth rules at its own auth events"""
-        await check_state_independent_auth_rules(self._store, event)
+        """Check an event passes the auth rules at its own auth events
+        Args:
+            event: event to be authed
+            batched_auth_events: if the event being authed is part of a batch, any events
+            from the same batch that may be necessary to auth the current event
+        """
+        await check_state_independent_auth_rules(
+            self._store, event, batched_auth_events
+        )
         auth_event_ids = event.auth_event_ids()
         auth_events_by_id = await self._store.get_events(auth_event_ids)
+        if batched_auth_events:
+            auth_events_by_id.update(batched_auth_events)
         check_state_dependent_auth_rules(event, auth_events_by_id.values())
 
     def compute_auth_events(
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 986ffed3d5..275a37a575 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -45,6 +45,7 @@ from synapse.api.errors import (
     Codes,
     FederationDeniedError,
     FederationError,
+    FederationPullAttemptBackoffError,
     HttpResponseException,
     LimitExceededError,
     NotFoundError,
@@ -631,6 +632,7 @@ class FederationHandler:
                     room_id=room_id,
                     servers=ret.servers_in_room,
                     device_lists_stream_id=self.store.get_device_stream_token(),
+                    joined_via=origin,
                 )
 
             try:
@@ -781,15 +783,27 @@ class FederationHandler:
 
         # Send the signed event back to the room, and potentially receive some
         # further information about the room in the form of partial state events
-        stripped_room_state = await self.federation_client.send_knock(
-            target_hosts, event
-        )
+        knock_response = await self.federation_client.send_knock(target_hosts, event)
 
         # Store any stripped room state events in the "unsigned" key of the event.
         # This is a bit of a hack and is cribbing off of invites. Basically we
         # store the room state here and retrieve it again when this event appears
         # in the invitee's sync stream. It is stripped out for all other local users.
-        event.unsigned["knock_room_state"] = stripped_room_state["knock_state_events"]
+        stripped_room_state = (
+            knock_response.get("knock_room_state")
+            # Since v1.37, Synapse incorrectly used "knock_state_events" for this field.
+            # Thus, we also check for a 'knock_state_events' to support old instances.
+            # See https://github.com/matrix-org/synapse/issues/14088.
+            or knock_response.get("knock_state_events")
+        )
+
+        if stripped_room_state is None:
+            raise KeyError(
+                "Missing 'knock_room_state' (or legacy 'knock_state_events') field in "
+                "send_knock response"
+            )
+
+        event.unsigned["knock_room_state"] = stripped_room_state
 
         context = EventContext.for_outlier(self._storage_controllers)
         stream_id = await self._federation_event_handler.persist_events_and_notify(
@@ -928,7 +942,7 @@ class FederationHandler:
 
         # The remote hasn't signed it yet, obviously. We'll do the full checks
         # when we get the event back in `on_send_join_request`
-        await self._event_auth_handler.check_auth_rules_from_context(event, context)
+        await self._event_auth_handler.check_auth_rules_from_context(event)
         return event
 
     async def on_invite_request(
@@ -1109,7 +1123,7 @@ class FederationHandler:
         try:
             # The remote hasn't signed it yet, obviously. We'll do the full checks
             # when we get the event back in `on_send_leave_request`
-            await self._event_auth_handler.check_auth_rules_from_context(event, context)
+            await self._event_auth_handler.check_auth_rules_from_context(event)
         except AuthError as e:
             logger.warning("Failed to create new leave %r because %s", event, e)
             raise e
@@ -1168,7 +1182,7 @@ class FederationHandler:
         try:
             # The remote hasn't signed it yet, obviously. We'll do the full checks
             # when we get the event back in `on_send_knock_request`
-            await self._event_auth_handler.check_auth_rules_from_context(event, context)
+            await self._event_auth_handler.check_auth_rules_from_context(event)
         except AuthError as e:
             logger.warning("Failed to create new knock %r because %s", event, e)
             raise e
@@ -1334,9 +1348,7 @@ class FederationHandler:
 
             try:
                 validate_event_for_room_version(event)
-                await self._event_auth_handler.check_auth_rules_from_context(
-                    event, context
-                )
+                await self._event_auth_handler.check_auth_rules_from_context(event)
             except AuthError as e:
                 logger.warning("Denying new third party invite %r because %s", event, e)
                 raise e
@@ -1386,7 +1398,7 @@ class FederationHandler:
 
         try:
             validate_event_for_room_version(event)
-            await self._event_auth_handler.check_auth_rules_from_context(event, context)
+            await self._event_auth_handler.check_auth_rules_from_context(event)
         except AuthError as e:
             logger.warning("Denying third party invite %r because %s", event, e)
             raise e
@@ -1602,13 +1614,13 @@ class FederationHandler:
         """Resumes resyncing of all partial-state rooms after a restart."""
         assert not self.config.worker.worker_app
 
-        partial_state_rooms = await self.store.get_partial_state_rooms_and_servers()
-        for room_id, servers_in_room in partial_state_rooms.items():
+        partial_state_rooms = await self.store.get_partial_state_room_resync_info()
+        for room_id, resync_info in partial_state_rooms.items():
             run_as_background_process(
                 desc="sync_partial_state_room",
                 func=self._sync_partial_state_room,
-                initial_destination=None,
-                other_destinations=servers_in_room,
+                initial_destination=resync_info.joined_via,
+                other_destinations=resync_info.servers_in_room,
                 room_id=room_id,
             )
 
@@ -1637,28 +1649,12 @@ class FederationHandler:
         #   really leave, that might mean we have difficulty getting the room state over
         #   federation.
         #   https://github.com/matrix-org/synapse/issues/12802
-        #
-        # TODO(faster_joins): we need some way of prioritising which homeservers in
-        #   `other_destinations` to try first, otherwise we'll spend ages trying dead
-        #   homeservers for large rooms.
-        #   https://github.com/matrix-org/synapse/issues/12999
-
-        if initial_destination is None and len(other_destinations) == 0:
-            raise ValueError(
-                f"Cannot resync state of {room_id}: no destinations provided"
-            )
 
         # Make an infinite iterator of destinations to try. Once we find a working
         # destination, we'll stick with it until it flakes.
-        destinations: Collection[str]
-        if initial_destination is not None:
-            # Move `initial_destination` to the front of the list.
-            destinations = list(other_destinations)
-            if initial_destination in destinations:
-                destinations.remove(initial_destination)
-            destinations = [initial_destination] + destinations
-        else:
-            destinations = other_destinations
+        destinations = _prioritise_destinations_for_partial_state_resync(
+            initial_destination, other_destinations, room_id
+        )
         destination_iter = itertools.cycle(destinations)
 
         # `destination` is the current remote homeserver we're pulling from.
@@ -1708,7 +1704,22 @@ class FederationHandler:
                             destination, event
                         )
                         break
+                    except FederationPullAttemptBackoffError as exc:
+                        # Log a warning about why we failed to process the event (the error message
+                        # for `FederationPullAttemptBackoffError` is pretty good)
+                        logger.warning("_sync_partial_state_room: %s", exc)
+                        # We do not record a failed pull attempt when we backoff fetching a missing
+                        # `prev_event` because not being able to fetch the `prev_events` just means
+                        # we won't be able to de-outlier the pulled event. But we can still use an
+                        # `outlier` in the state/auth chain for another event. So we shouldn't stop
+                        # a downstream event from trying to pull it.
+                        #
+                        # This avoids a cascade of backoff for all events in the DAG downstream from
+                        # one event backoff upstream.
                     except FederationError as e:
+                        # TODO: We should `record_event_failed_pull_attempt` here,
+                        #   see https://github.com/matrix-org/synapse/issues/13700
+
                         if attempt == len(destinations) - 1:
                             # We have tried every remote server for this event. Give up.
                             # TODO(faster_joins) giving up isn't the right thing to do
@@ -1741,3 +1752,29 @@ class FederationHandler:
                             room_id,
                             destination,
                         )
+
+
+def _prioritise_destinations_for_partial_state_resync(
+    initial_destination: Optional[str],
+    other_destinations: Collection[str],
+    room_id: str,
+) -> Collection[str]:
+    """Work out the order in which we should ask servers to resync events.
+
+    If an `initial_destination` is given, it takes top priority. Otherwise
+    all servers are treated equally.
+
+    :raises ValueError: if no destination is provided at all.
+    """
+    if initial_destination is None and len(other_destinations) == 0:
+        raise ValueError(f"Cannot resync state of {room_id}: no destinations provided")
+
+    if initial_destination is None:
+        return other_destinations
+
+    # Move `initial_destination` to the front of the list.
+    destinations = list(other_destinations)
+    if initial_destination in destinations:
+        destinations.remove(initial_destination)
+    destinations = [initial_destination] + destinations
+    return destinations
diff --git a/synapse/handlers/federation_event.py b/synapse/handlers/federation_event.py
index da319943cc..06e41b5cc0 100644
--- a/synapse/handlers/federation_event.py
+++ b/synapse/handlers/federation_event.py
@@ -44,6 +44,7 @@ from synapse.api.errors import (
     AuthError,
     Codes,
     FederationError,
+    FederationPullAttemptBackoffError,
     HttpResponseException,
     RequestSendFailed,
     SynapseError,
@@ -414,7 +415,9 @@ class FederationEventHandler:
 
         # First, precalculate the joined hosts so that the federation sender doesn't
         # need to.
-        await self._event_creation_handler.cache_joined_hosts_for_event(event, context)
+        await self._event_creation_handler.cache_joined_hosts_for_events(
+            [(event, context)]
+        )
 
         await self._check_for_soft_fail(event, context=context, origin=origin)
         await self._run_push_actions_and_persist_event(event, context)
@@ -565,6 +568,9 @@ class FederationEventHandler:
             event: partial-state event to be de-partial-stated
 
         Raises:
+            FederationPullAttemptBackoffError if we are are deliberately not attempting
+                to pull the given event over federation because we've already done so
+                recently and are backing off.
             FederationError if we fail to request state from the remote server.
         """
         logger.info("Updating state for %s", event.event_id)
@@ -792,9 +798,42 @@ class FederationEventHandler:
             ],
         )
 
+        # Check if we already any of these have these events.
+        # Note: we currently make a lookup in the database directly here rather than
+        # checking the event cache, due to:
+        # https://github.com/matrix-org/synapse/issues/13476
+        existing_events_map = await self._store._get_events_from_db(
+            [event.event_id for event in events]
+        )
+
+        new_events = []
+        for event in events:
+            event_id = event.event_id
+
+            # If we've already seen this event ID...
+            if event_id in existing_events_map:
+                existing_event = existing_events_map[event_id]
+
+                # ...and the event itself was not previously stored as an outlier...
+                if not existing_event.event.internal_metadata.is_outlier():
+                    # ...then there's no need to persist it. We have it already.
+                    logger.info(
+                        "_process_pulled_event: Ignoring received event %s which we "
+                        "have already seen",
+                        event.event_id,
+                    )
+                    continue
+
+                # While we have seen this event before, it was stored as an outlier.
+                # We'll now persist it as a non-outlier.
+                logger.info("De-outliering event %s", event_id)
+
+            # Continue on with the events that are new to us.
+            new_events.append(event)
+
         # We want to sort these by depth so we process them and
         # tell clients about them in order.
-        sorted_events = sorted(events, key=lambda x: x.depth)
+        sorted_events = sorted(new_events, key=lambda x: x.depth)
         for ev in sorted_events:
             with nested_logging_context(ev.event_id):
                 await self._process_pulled_event(origin, ev, backfilled=backfilled)
@@ -846,18 +885,6 @@ class FederationEventHandler:
 
         event_id = event.event_id
 
-        existing = await self._store.get_event(
-            event_id, allow_none=True, allow_rejected=True
-        )
-        if existing:
-            if not existing.internal_metadata.is_outlier():
-                logger.info(
-                    "_process_pulled_event: Ignoring received event %s which we have already seen",
-                    event_id,
-                )
-                return
-            logger.info("De-outliering event %s", event_id)
-
         try:
             self._sanity_check_event(event)
         except SynapseError as err:
@@ -899,6 +926,18 @@ class FederationEventHandler:
                     context,
                     backfilled=backfilled,
                 )
+        except FederationPullAttemptBackoffError as exc:
+            # Log a warning about why we failed to process the event (the error message
+            # for `FederationPullAttemptBackoffError` is pretty good)
+            logger.warning("_process_pulled_event: %s", exc)
+            # We do not record a failed pull attempt when we backoff fetching a missing
+            # `prev_event` because not being able to fetch the `prev_events` just means
+            # we won't be able to de-outlier the pulled event. But we can still use an
+            # `outlier` in the state/auth chain for another event. So we shouldn't stop
+            # a downstream event from trying to pull it.
+            #
+            # This avoids a cascade of backoff for all events in the DAG downstream from
+            # one event backoff upstream.
         except FederationError as e:
             await self._store.record_event_failed_pull_attempt(
                 event.room_id, event_id, str(e)
@@ -945,6 +984,9 @@ class FederationEventHandler:
             The event context.
 
         Raises:
+            FederationPullAttemptBackoffError if we are are deliberately not attempting
+                to pull the given event over federation because we've already done so
+                recently and are backing off.
             FederationError if we fail to get the state from the remote server after any
                 missing `prev_event`s.
         """
@@ -955,6 +997,18 @@ class FederationEventHandler:
         seen = await self._store.have_events_in_timeline(prevs)
         missing_prevs = prevs - seen
 
+        # If we've already recently attempted to pull this missing event, don't
+        # try it again so soon. Since we have to fetch all of the prev_events, we can
+        # bail early here if we find any to ignore.
+        prevs_to_ignore = await self._store.get_event_ids_to_not_pull_from_backoff(
+            room_id, missing_prevs
+        )
+        if len(prevs_to_ignore) > 0:
+            raise FederationPullAttemptBackoffError(
+                event_ids=prevs_to_ignore,
+                message=f"While computing context for event={event_id}, not attempting to pull missing prev_event={prevs_to_ignore[0]} because we already tried to pull recently (backing off).",
+            )
+
         if not missing_prevs:
             return await self._state_handler.compute_event_context(event)
 
diff --git a/synapse/handlers/initial_sync.py b/synapse/handlers/initial_sync.py
index 860c82c110..9c335e6863 100644
--- a/synapse/handlers/initial_sync.py
+++ b/synapse/handlers/initial_sync.py
@@ -57,13 +57,7 @@ class InitialSyncHandler:
         self.validator = EventValidator()
         self.snapshot_cache: ResponseCache[
             Tuple[
-                str,
-                Optional[StreamToken],
-                Optional[StreamToken],
-                str,
-                Optional[int],
-                bool,
-                bool,
+                str, Optional[StreamToken], Optional[StreamToken], str, int, bool, bool
             ]
         ] = ResponseCache(hs.get_clock(), "initial_sync_cache")
         self._event_serializer = hs.get_event_client_serializer()
@@ -154,11 +148,6 @@ class InitialSyncHandler:
 
         public_room_ids = await self.store.get_public_room_ids()
 
-        if pagin_config.limit is not None:
-            limit = pagin_config.limit
-        else:
-            limit = 10
-
         serializer_options = SerializeEventConfig(as_client_event=as_client_event)
 
         async def handle_room(event: RoomsForUser) -> None:
@@ -210,7 +199,7 @@ class InitialSyncHandler:
                             run_in_background(
                                 self.store.get_recent_events_for_room,
                                 event.room_id,
-                                limit=limit,
+                                limit=pagin_config.limit,
                                 end_token=room_end_token,
                             ),
                             deferred_room_state,
@@ -360,15 +349,11 @@ class InitialSyncHandler:
             member_event_id
         )
 
-        limit = pagin_config.limit if pagin_config else None
-        if limit is None:
-            limit = 10
-
         leave_position = await self.store.get_position_for_event(member_event_id)
         stream_token = leave_position.to_room_stream_token()
 
         messages, token = await self.store.get_recent_events_for_room(
-            room_id, limit=limit, end_token=stream_token
+            room_id, limit=pagin_config.limit, end_token=stream_token
         )
 
         messages = await filter_events_for_client(
@@ -420,10 +405,6 @@ class InitialSyncHandler:
 
         now_token = self.hs.get_event_sources().get_current_token()
 
-        limit = pagin_config.limit if pagin_config else None
-        if limit is None:
-            limit = 10
-
         room_members = [
             m
             for m in current_state.values()
@@ -467,7 +448,7 @@ class InitialSyncHandler:
                     run_in_background(
                         self.store.get_recent_events_for_room,
                         room_id,
-                        limit=limit,
+                        limit=pagin_config.limit,
                         end_token=now_token.room_key,
                     ),
                 ),
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index da1acea275..15b828dd74 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -1360,8 +1360,16 @@ class EventCreationHandler:
             else:
                 try:
                     validate_event_for_room_version(event)
+                    # If we are persisting a batch of events the event(s) needed to auth the
+                    # current event may be part of the batch and will not be in the DB yet
+                    event_id_to_event = {e.event_id: e for e, _ in events_and_context}
+                    batched_auth_events = {}
+                    for event_id in event.auth_event_ids():
+                        auth_event = event_id_to_event.get(event_id)
+                        if auth_event:
+                            batched_auth_events[event_id] = auth_event
                     await self._event_auth_handler.check_auth_rules_from_context(
-                        event, context
+                        event, batched_auth_events
                     )
                 except AuthError as err:
                     logger.warning("Denying new event %r because %s", event, err)
@@ -1390,7 +1398,7 @@ class EventCreationHandler:
                             extra_users=extra_users,
                         ),
                         run_in_background(
-                            self.cache_joined_hosts_for_event, event, context
+                            self.cache_joined_hosts_for_events, events_and_context
                         ).addErrback(
                             log_failure, "cache_joined_hosts_for_event failed"
                         ),
@@ -1491,62 +1499,65 @@ class EventCreationHandler:
                 await self.store.remove_push_actions_from_staging(event.event_id)
             raise
 
-    async def cache_joined_hosts_for_event(
-        self, event: EventBase, context: EventContext
+    async def cache_joined_hosts_for_events(
+        self, events_and_context: List[Tuple[EventBase, EventContext]]
     ) -> None:
-        """Precalculate the joined hosts at the event, when using Redis, so that
+        """Precalculate the joined hosts at each of the given events, when using Redis, so that
         external federation senders don't have to recalculate it themselves.
         """
 
-        if not self._external_cache.is_enabled():
-            return
+        for event, _ in events_and_context:
+            if not self._external_cache.is_enabled():
+                return
 
-        # If external cache is enabled we should always have this.
-        assert self._external_cache_joined_hosts_updates is not None
+            # If external cache is enabled we should always have this.
+            assert self._external_cache_joined_hosts_updates is not None
 
-        # We actually store two mappings, event ID -> prev state group,
-        # state group -> joined hosts, which is much more space efficient
-        # than event ID -> joined hosts.
-        #
-        # Note: We have to cache event ID -> prev state group, as we don't
-        # store that in the DB.
-        #
-        # Note: We set the state group -> joined hosts cache if it hasn't been
-        # set for a while, so that the expiry time is reset.
-
-        state_entry = await self.state.resolve_state_groups_for_events(
-            event.room_id, event_ids=event.prev_event_ids()
-        )
+            # We actually store two mappings, event ID -> prev state group,
+            # state group -> joined hosts, which is much more space efficient
+            # than event ID -> joined hosts.
+            #
+            # Note: We have to cache event ID -> prev state group, as we don't
+            # store that in the DB.
+            #
+            # Note: We set the state group -> joined hosts cache if it hasn't been
+            # set for a while, so that the expiry time is reset.
 
-        if state_entry.state_group:
-            await self._external_cache.set(
-                "event_to_prev_state_group",
-                event.event_id,
-                state_entry.state_group,
-                expiry_ms=60 * 60 * 1000,
+            state_entry = await self.state.resolve_state_groups_for_events(
+                event.room_id, event_ids=event.prev_event_ids()
             )
 
-            if state_entry.state_group in self._external_cache_joined_hosts_updates:
-                return
+            if state_entry.state_group:
+                await self._external_cache.set(
+                    "event_to_prev_state_group",
+                    event.event_id,
+                    state_entry.state_group,
+                    expiry_ms=60 * 60 * 1000,
+                )
 
-            state = await state_entry.get_state(
-                self._storage_controllers.state, StateFilter.all()
-            )
-            with opentracing.start_active_span("get_joined_hosts"):
-                joined_hosts = await self.store.get_joined_hosts(
-                    event.room_id, state, state_entry
+                if state_entry.state_group in self._external_cache_joined_hosts_updates:
+                    return
+
+                state = await state_entry.get_state(
+                    self._storage_controllers.state, StateFilter.all()
                 )
+                with opentracing.start_active_span("get_joined_hosts"):
+                    joined_hosts = await self.store.get_joined_hosts(
+                        event.room_id, state, state_entry
+                    )
 
-            # Note that the expiry times must be larger than the expiry time in
-            # _external_cache_joined_hosts_updates.
-            await self._external_cache.set(
-                "get_joined_hosts",
-                str(state_entry.state_group),
-                list(joined_hosts),
-                expiry_ms=60 * 60 * 1000,
-            )
+                # Note that the expiry times must be larger than the expiry time in
+                # _external_cache_joined_hosts_updates.
+                await self._external_cache.set(
+                    "get_joined_hosts",
+                    str(state_entry.state_group),
+                    list(joined_hosts),
+                    expiry_ms=60 * 60 * 1000,
+                )
 
-            self._external_cache_joined_hosts_updates[state_entry.state_group] = None
+                self._external_cache_joined_hosts_updates[
+                    state_entry.state_group
+                ] = None
 
     async def _validate_canonical_alias(
         self,
diff --git a/synapse/handlers/pagination.py b/synapse/handlers/pagination.py
index 1f83bab836..a4ca9cb8b4 100644
--- a/synapse/handlers/pagination.py
+++ b/synapse/handlers/pagination.py
@@ -458,11 +458,6 @@ class PaginationHandler:
             # `/messages` should still works with live tokens when manually provided.
             assert from_token.room_key.topological is not None
 
-        if pagin_config.limit is None:
-            # This shouldn't happen as we've set a default limit before this
-            # gets called.
-            raise Exception("limit not set")
-
         room_token = from_token.room_key
 
         async with self.pagination_lock.read(room_id):
diff --git a/synapse/handlers/presence.py b/synapse/handlers/presence.py
index 4e575ffbaa..2670e561d7 100644
--- a/synapse/handlers/presence.py
+++ b/synapse/handlers/presence.py
@@ -1596,7 +1596,9 @@ class PresenceEventSource(EventSource[int, UserPresenceState]):
         self,
         user: UserID,
         from_key: Optional[int],
-        limit: Optional[int] = None,
+        # Having a default limit doesn't match the EventSource API, but some
+        # callers do not provide it. It is unused in this class.
+        limit: int = 0,
         room_ids: Optional[Collection[str]] = None,
         is_guest: bool = False,
         explicit_room_id: Optional[str] = None,
diff --git a/synapse/handlers/receipts.py b/synapse/handlers/receipts.py
index 4a7ec9e426..ac01582442 100644
--- a/synapse/handlers/receipts.py
+++ b/synapse/handlers/receipts.py
@@ -257,7 +257,7 @@ class ReceiptEventSource(EventSource[int, JsonDict]):
         self,
         user: UserID,
         from_key: int,
-        limit: Optional[int],
+        limit: int,
         room_ids: Iterable[str],
         is_guest: bool,
         explicit_room_id: Optional[str] = None,
diff --git a/synapse/handlers/relations.py b/synapse/handlers/relations.py
index cc5e45c241..0a0c6d938e 100644
--- a/synapse/handlers/relations.py
+++ b/synapse/handlers/relations.py
@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+import enum
 import logging
 from typing import TYPE_CHECKING, Dict, FrozenSet, Iterable, List, Optional, Tuple
 
@@ -20,7 +21,7 @@ from synapse.api.constants import RelationTypes
 from synapse.api.errors import SynapseError
 from synapse.events import EventBase, relation_from_event
 from synapse.logging.opentracing import trace
-from synapse.storage.databases.main.relations import _RelatedEvent
+from synapse.storage.databases.main.relations import ThreadsNextBatch, _RelatedEvent
 from synapse.streams.config import PaginationConfig
 from synapse.types import JsonDict, Requester, StreamToken, UserID
 from synapse.visibility import filter_events_for_client
@@ -32,6 +33,13 @@ if TYPE_CHECKING:
 logger = logging.getLogger(__name__)
 
 
+class ThreadsListInclude(str, enum.Enum):
+    """Valid values for the 'include' flag of /threads."""
+
+    all = "all"
+    participated = "participated"
+
+
 @attr.s(slots=True, frozen=True, auto_attribs=True)
 class _ThreadAggregation:
     # The latest event in the thread.
@@ -108,9 +116,6 @@ class RelationsHandler:
         if event is None:
             raise SynapseError(404, "Unknown parent event.")
 
-        # TODO Update pagination config to not allow None limits.
-        assert pagin_config.limit is not None
-
         # Note that ignored users are not passed into get_relations_for_event
         # below. Ignored users are handled in filter_events_for_client (and by
         # not passing them in here we should get a better cache hit rate).
@@ -482,3 +487,79 @@ class RelationsHandler:
             results.setdefault(event_id, BundledAggregations()).replace = edit
 
         return results
+
+    async def get_threads(
+        self,
+        requester: Requester,
+        room_id: str,
+        include: ThreadsListInclude,
+        limit: int = 5,
+        from_token: Optional[ThreadsNextBatch] = None,
+    ) -> JsonDict:
+        """Get related events of a event, ordered by topological ordering.
+
+        Args:
+            requester: The user requesting the relations.
+            room_id: The room the event belongs to.
+            include: One of "all" or "participated" to indicate which threads should
+                be returned.
+            limit: Only fetch the most recent `limit` events.
+            from_token: Fetch rows from the given token, or from the start if None.
+
+        Returns:
+            The pagination chunk.
+        """
+
+        user_id = requester.user.to_string()
+
+        # TODO Properly handle a user leaving a room.
+        (_, member_event_id) = await self._auth.check_user_in_room_or_world_readable(
+            room_id, requester, allow_departed_users=True
+        )
+
+        # Note that ignored users are not passed into get_relations_for_event
+        # below. Ignored users are handled in filter_events_for_client (and by
+        # not passing them in here we should get a better cache hit rate).
+        thread_roots, next_batch = await self._main_store.get_threads(
+            room_id=room_id, limit=limit, from_token=from_token
+        )
+
+        events = await self._main_store.get_events_as_list(thread_roots)
+
+        if include == ThreadsListInclude.participated:
+            # Pre-seed thread participation with whether the requester sent the event.
+            participated = {event.event_id: event.sender == user_id for event in events}
+            # For events the requester did not send, check the database for whether
+            # the requester sent a threaded reply.
+            participated.update(
+                await self._main_store.get_threads_participated(
+                    [eid for eid, p in participated.items() if not p],
+                    user_id,
+                )
+            )
+
+            # Limit the returned threads to those the user has participated in.
+            events = [event for event in events if participated[event.event_id]]
+
+        events = await filter_events_for_client(
+            self._storage_controllers,
+            user_id,
+            events,
+            is_peeking=(member_event_id is None),
+        )
+
+        aggregations = await self.get_bundled_aggregations(
+            events, requester.user.to_string()
+        )
+
+        now = self._clock.time_msec()
+        serialized_events = self._event_serializer.serialize_events(
+            events, now, bundle_aggregations=aggregations
+        )
+
+        return_value: JsonDict = {"chunk": serialized_events}
+
+        if next_batch:
+            return_value["next_batch"] = str(next_batch)
+
+        return return_value
diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index 57ab05ad25..638f54051a 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -229,9 +229,7 @@ class RoomCreationHandler:
             },
         )
         validate_event_for_room_version(tombstone_event)
-        await self._event_auth_handler.check_auth_rules_from_context(
-            tombstone_event, tombstone_context
-        )
+        await self._event_auth_handler.check_auth_rules_from_context(tombstone_event)
 
         # Upgrade the room
         #
@@ -1646,7 +1644,7 @@ class RoomEventSource(EventSource[RoomStreamToken, EventBase]):
         self,
         user: UserID,
         from_key: RoomStreamToken,
-        limit: Optional[int],
+        limit: int,
         room_ids: Collection[str],
         is_guest: bool,
         explicit_room_id: Optional[str] = None,
diff --git a/synapse/handlers/sso.py b/synapse/handlers/sso.py
index e035677b8a..5943f08e91 100644
--- a/synapse/handlers/sso.py
+++ b/synapse/handlers/sso.py
@@ -874,7 +874,7 @@ class SsoHandler:
         )
 
     async def handle_terms_accepted(
-        self, request: Request, session_id: str, terms_version: str
+        self, request: SynapseRequest, session_id: str, terms_version: str
     ) -> None:
         """Handle a request to the new-user 'consent' endpoint
 
diff --git a/synapse/handlers/typing.py b/synapse/handlers/typing.py
index f953691669..a0ea719430 100644
--- a/synapse/handlers/typing.py
+++ b/synapse/handlers/typing.py
@@ -513,7 +513,7 @@ class TypingNotificationEventSource(EventSource[int, JsonDict]):
         self,
         user: UserID,
         from_key: int,
-        limit: Optional[int],
+        limit: int,
         room_ids: Iterable[str],
         is_guest: bool,
         explicit_room_id: Optional[str] = None,
diff --git a/synapse/http/server.py b/synapse/http/server.py
index bcbfac2c9f..b26e34bceb 100644
--- a/synapse/http/server.py
+++ b/synapse/http/server.py
@@ -19,6 +19,7 @@ import logging
 import types
 import urllib
 from http import HTTPStatus
+from http.client import FOUND
 from inspect import isawaitable
 from typing import (
     TYPE_CHECKING,
@@ -339,7 +340,7 @@ class _AsyncResource(resource.Resource, metaclass=abc.ABCMeta):
 
             return callback_return
 
-        _unrecognised_request_handler(request)
+        return _unrecognised_request_handler(request)
 
     @abc.abstractmethod
     def _send_response(
@@ -598,7 +599,7 @@ class RootRedirect(resource.Resource):
 class OptionsResource(resource.Resource):
     """Responds to OPTION requests for itself and all children."""
 
-    def render_OPTIONS(self, request: Request) -> bytes:
+    def render_OPTIONS(self, request: SynapseRequest) -> bytes:
         request.setResponseCode(204)
         request.setHeader(b"Content-Length", b"0")
 
@@ -763,7 +764,7 @@ def respond_with_json(
 
 
 def respond_with_json_bytes(
-    request: Request,
+    request: SynapseRequest,
     code: int,
     json_bytes: bytes,
     send_cors: bool = False,
@@ -859,7 +860,7 @@ def _write_bytes_to_request(request: Request, bytes_to_write: bytes) -> None:
     _ByteProducer(request, bytes_generator)
 
 
-def set_cors_headers(request: Request) -> None:
+def set_cors_headers(request: SynapseRequest) -> None:
     """Set the CORS headers so that javascript running in a web browsers can
     use this API
 
@@ -870,10 +871,20 @@ def set_cors_headers(request: Request) -> None:
     request.setHeader(
         b"Access-Control-Allow-Methods", b"GET, HEAD, POST, PUT, DELETE, OPTIONS"
     )
-    request.setHeader(
-        b"Access-Control-Allow-Headers",
-        b"X-Requested-With, Content-Type, Authorization, Date",
-    )
+    if request.experimental_cors_msc3886:
+        request.setHeader(
+            b"Access-Control-Allow-Headers",
+            b"X-Requested-With, Content-Type, Authorization, Date, If-Match, If-None-Match",
+        )
+        request.setHeader(
+            b"Access-Control-Expose-Headers",
+            b"ETag, Location, X-Max-Bytes",
+        )
+    else:
+        request.setHeader(
+            b"Access-Control-Allow-Headers",
+            b"X-Requested-With, Content-Type, Authorization, Date",
+        )
 
 
 def set_corp_headers(request: Request) -> None:
@@ -942,10 +953,25 @@ def set_clickjacking_protection_headers(request: Request) -> None:
     request.setHeader(b"Content-Security-Policy", b"frame-ancestors 'none';")
 
 
-def respond_with_redirect(request: Request, url: bytes) -> None:
-    """Write a 302 response to the request, if it is still alive."""
+def respond_with_redirect(
+    request: SynapseRequest, url: bytes, statusCode: int = FOUND, cors: bool = False
+) -> None:
+    """
+    Write a 302 (or other specified status code) response to the request, if it is still alive.
+
+    Args:
+        request: The http request to respond to.
+        url: The URL to redirect to.
+        statusCode: The HTTP status code to use for the redirect (defaults to 302).
+        cors: Whether to set CORS headers on the response.
+    """
     logger.debug("Redirect to %s", url.decode("utf-8"))
-    request.redirect(url)
+
+    if cors:
+        set_cors_headers(request)
+
+    request.setResponseCode(statusCode)
+    request.setHeader(b"location", url)
     finish_request(request)
 
 
diff --git a/synapse/http/site.py b/synapse/http/site.py
index 55a6afce35..3dbd541fed 100644
--- a/synapse/http/site.py
+++ b/synapse/http/site.py
@@ -82,6 +82,7 @@ class SynapseRequest(Request):
         self.reactor = site.reactor
         self._channel = channel  # this is used by the tests
         self.start_time = 0.0
+        self.experimental_cors_msc3886 = site.experimental_cors_msc3886
 
         # The requester, if authenticated. For federation requests this is the
         # server name, for client requests this is the Requester object.
@@ -622,6 +623,8 @@ class SynapseSite(Site):
 
         request_id_header = config.http_options.request_id_header
 
+        self.experimental_cors_msc3886 = config.http_options.experimental_cors_msc3886
+
         def request_factory(channel: HTTPChannel, queued: bool) -> Request:
             return request_class(
                 channel,
diff --git a/synapse/push/bulk_push_rule_evaluator.py b/synapse/push/bulk_push_rule_evaluator.py
index eced182fd5..a75386f6a0 100644
--- a/synapse/push/bulk_push_rule_evaluator.py
+++ b/synapse/push/bulk_push_rule_evaluator.py
@@ -13,18 +13,15 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import itertools
 import logging
 from typing import (
     TYPE_CHECKING,
     Any,
     Collection,
     Dict,
-    Iterable,
     List,
     Mapping,
     Optional,
-    Set,
     Tuple,
     Union,
 )
@@ -38,7 +35,7 @@ from synapse.events.snapshot import EventContext
 from synapse.state import POWER_KEY
 from synapse.storage.databases.main.roommember import EventIdMembership
 from synapse.storage.state import StateFilter
-from synapse.synapse_rust.push import FilteredPushRules, PushRule, PushRuleEvaluator
+from synapse.synapse_rust.push import FilteredPushRules, PushRuleEvaluator
 from synapse.util.caches import register_cache
 from synapse.util.metrics import measure_func
 from synapse.visibility import filter_event_for_clients_with_state
@@ -117,9 +114,6 @@ class BulkPushRuleEvaluator:
             resizable=False,
         )
 
-        # Whether to support MSC3772 is supported.
-        self._relations_match_enabled = self.hs.config.experimental.msc3772_enabled
-
     async def _get_rules_for_event(
         self,
         event: EventBase,
@@ -200,51 +194,6 @@ class BulkPushRuleEvaluator:
 
         return pl_event.content if pl_event else {}, sender_level
 
-    async def _get_mutual_relations(
-        self, parent_id: str, rules: Iterable[Tuple[PushRule, bool]]
-    ) -> Dict[str, Set[Tuple[str, str]]]:
-        """
-        Fetch event metadata for events which related to the same event as the given event.
-
-        If the given event has no relation information, returns an empty dictionary.
-
-        Args:
-            parent_id: The event ID which is targeted by relations.
-            rules: The push rules which will be processed for this event.
-
-        Returns:
-            A dictionary of relation type to:
-                A set of tuples of:
-                    The sender
-                    The event type
-        """
-
-        # If the experimental feature is not enabled, skip fetching relations.
-        if not self._relations_match_enabled:
-            return {}
-
-        # Pre-filter to figure out which relation types are interesting.
-        rel_types = set()
-        for rule, enabled in rules:
-            if not enabled:
-                continue
-
-            for condition in rule.conditions:
-                if condition["kind"] != "org.matrix.msc3772.relation_match":
-                    continue
-
-                # rel_type is required.
-                rel_type = condition.get("rel_type")
-                if rel_type:
-                    rel_types.add(rel_type)
-
-        # If no valid rules were found, no mutual relations.
-        if not rel_types:
-            return {}
-
-        # If any valid rules were found, fetch the mutual relations.
-        return await self.store.get_mutual_event_relations(parent_id, rel_types)
-
     @measure_func("action_for_event_by_user")
     async def action_for_event_by_user(
         self, event: EventBase, context: EventContext
@@ -276,23 +225,18 @@ class BulkPushRuleEvaluator:
             sender_power_level,
         ) = await self._get_power_levels_and_sender_level(event, context)
 
+        # Find the event's thread ID.
         relation = relation_from_event(event)
-        # If the event does not have a relation, then cannot have any mutual
-        # relations or thread ID.
-        relations = {}
+        # If the event does not have a relation, then it cannot have a thread ID.
         thread_id = MAIN_TIMELINE
         if relation:
-            relations = await self._get_mutual_relations(
-                relation.parent_id,
-                itertools.chain(*(r.rules() for r in rules_by_user.values())),
-            )
             # Recursively attempt to find the thread this event relates to.
             if relation.rel_type == RelationTypes.THREAD:
                 thread_id = relation.parent_id
             else:
                 # Since the event has not yet been persisted we check whether
                 # the parent is part of a thread.
-                thread_id = await self.store.get_thread_id(relation.parent_id) or "main"
+                thread_id = await self.store.get_thread_id(relation.parent_id)
 
         # It's possible that old room versions have non-integer power levels (floats or
         # strings). Workaround this by explicitly converting to int.
@@ -306,8 +250,6 @@ class BulkPushRuleEvaluator:
             room_member_count,
             sender_power_level,
             notification_levels,
-            relations,
-            self._relations_match_enabled,
         )
 
         users = rules_by_user.keys()
diff --git a/synapse/replication/http/register.py b/synapse/replication/http/register.py
index 61abb529c8..976c283360 100644
--- a/synapse/replication/http/register.py
+++ b/synapse/replication/http/register.py
@@ -39,6 +39,16 @@ class ReplicationRegisterServlet(ReplicationEndpoint):
         self.store = hs.get_datastores().main
         self.registration_handler = hs.get_registration_handler()
 
+        # Default value if the worker that sent the replication request did not include
+        # an 'approved' property.
+        if (
+            hs.config.experimental.msc3866.enabled
+            and hs.config.experimental.msc3866.require_approval_for_new_accounts
+        ):
+            self._approval_default = False
+        else:
+            self._approval_default = True
+
     @staticmethod
     async def _serialize_payload(  # type: ignore[override]
         user_id: str,
@@ -92,6 +102,12 @@ class ReplicationRegisterServlet(ReplicationEndpoint):
 
         await self.registration_handler.check_registration_ratelimit(content["address"])
 
+        # Always default admin users to approved (since it means they were created by
+        # an admin).
+        approved_default = self._approval_default
+        if content["admin"]:
+            approved_default = True
+
         await self.registration_handler.register_with_store(
             user_id=user_id,
             password_hash=content["password_hash"],
@@ -103,7 +119,7 @@ class ReplicationRegisterServlet(ReplicationEndpoint):
             user_type=content["user_type"],
             address=content["address"],
             shadow_banned=content["shadow_banned"],
-            approved=content["approved"],
+            approved=content.get("approved", approved_default),
         )
 
         return 200, {}
diff --git a/synapse/rest/__init__.py b/synapse/rest/__init__.py
index 9a2ab99ede..28542cd774 100644
--- a/synapse/rest/__init__.py
+++ b/synapse/rest/__init__.py
@@ -44,6 +44,7 @@ from synapse.rest.client import (
     receipts,
     register,
     relations,
+    rendezvous,
     report_event,
     room,
     room_batch,
@@ -132,3 +133,4 @@ class ClientRestResource(JsonResource):
         # unstable
         mutual_rooms.register_servlets(hs, client_resource)
         login_token_request.register_servlets(hs, client_resource)
+        rendezvous.register_servlets(hs, client_resource)
diff --git a/synapse/rest/client/directory.py b/synapse/rest/client/directory.py
index bc1b18c92d..f17b4c8d22 100644
--- a/synapse/rest/client/directory.py
+++ b/synapse/rest/client/directory.py
@@ -13,15 +13,22 @@
 # limitations under the License.
 
 import logging
-from typing import TYPE_CHECKING, Tuple
+from typing import TYPE_CHECKING, List, Optional, Tuple
+
+from pydantic import StrictStr
+from typing_extensions import Literal
 
 from twisted.web.server import Request
 
 from synapse.api.errors import AuthError, Codes, NotFoundError, SynapseError
 from synapse.http.server import HttpServer
-from synapse.http.servlet import RestServlet, parse_json_object_from_request
+from synapse.http.servlet import (
+    RestServlet,
+    parse_and_validate_json_object_from_request,
+)
 from synapse.http.site import SynapseRequest
 from synapse.rest.client._base import client_patterns
+from synapse.rest.models import RequestBodyModel
 from synapse.types import JsonDict, RoomAlias
 
 if TYPE_CHECKING:
@@ -54,6 +61,12 @@ class ClientDirectoryServer(RestServlet):
 
         return 200, res
 
+    class PutBody(RequestBodyModel):
+        # TODO: get Pydantic to validate that this is a valid room id?
+        room_id: StrictStr
+        # `servers` is unspecced
+        servers: Optional[List[StrictStr]] = None
+
     async def on_PUT(
         self, request: SynapseRequest, room_alias: str
     ) -> Tuple[int, JsonDict]:
@@ -61,31 +74,22 @@ class ClientDirectoryServer(RestServlet):
             raise SynapseError(400, "Room alias invalid", errcode=Codes.INVALID_PARAM)
         room_alias_obj = RoomAlias.from_string(room_alias)
 
-        content = parse_json_object_from_request(request)
-        if "room_id" not in content:
-            raise SynapseError(
-                400, 'Missing params: ["room_id"]', errcode=Codes.BAD_JSON
-            )
+        content = parse_and_validate_json_object_from_request(request, self.PutBody)
 
         logger.debug("Got content: %s", content)
         logger.debug("Got room name: %s", room_alias_obj.to_string())
 
-        room_id = content["room_id"]
-        servers = content["servers"] if "servers" in content else None
-
-        logger.debug("Got room_id: %s", room_id)
-        logger.debug("Got servers: %s", servers)
+        logger.debug("Got room_id: %s", content.room_id)
+        logger.debug("Got servers: %s", content.servers)
 
-        # TODO(erikj): Check types.
-
-        room = await self.store.get_room(room_id)
+        room = await self.store.get_room(content.room_id)
         if room is None:
             raise SynapseError(400, "Room does not exist")
 
         requester = await self.auth.get_user_by_req(request)
 
         await self.directory_handler.create_association(
-            requester, room_alias_obj, room_id, servers
+            requester, room_alias_obj, content.room_id, content.servers
         )
 
         return 200, {}
@@ -137,16 +141,18 @@ class ClientDirectoryListServer(RestServlet):
 
         return 200, {"visibility": "public" if room["is_public"] else "private"}
 
+    class PutBody(RequestBodyModel):
+        visibility: Literal["public", "private"] = "public"
+
     async def on_PUT(
         self, request: SynapseRequest, room_id: str
     ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
 
-        content = parse_json_object_from_request(request)
-        visibility = content.get("visibility", "public")
+        content = parse_and_validate_json_object_from_request(request, self.PutBody)
 
         await self.directory_handler.edit_published_room_list(
-            requester, room_id, visibility
+            requester, room_id, content.visibility
         )
 
         return 200, {}
@@ -163,12 +169,14 @@ class ClientAppserviceDirectoryListServer(RestServlet):
         self.directory_handler = hs.get_directory_handler()
         self.auth = hs.get_auth()
 
+    class PutBody(RequestBodyModel):
+        visibility: Literal["public", "private"] = "public"
+
     async def on_PUT(
         self, request: SynapseRequest, network_id: str, room_id: str
     ) -> Tuple[int, JsonDict]:
-        content = parse_json_object_from_request(request)
-        visibility = content.get("visibility", "public")
-        return await self._edit(request, network_id, room_id, visibility)
+        content = parse_and_validate_json_object_from_request(request, self.PutBody)
+        return await self._edit(request, network_id, room_id, content.visibility)
 
     async def on_DELETE(
         self, request: SynapseRequest, network_id: str, room_id: str
@@ -176,7 +184,11 @@ class ClientAppserviceDirectoryListServer(RestServlet):
         return await self._edit(request, network_id, room_id, "private")
 
     async def _edit(
-        self, request: SynapseRequest, network_id: str, room_id: str, visibility: str
+        self,
+        request: SynapseRequest,
+        network_id: str,
+        room_id: str,
+        visibility: Literal["public", "private"],
     ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
         if not requester.app_service:
diff --git a/synapse/rest/client/events.py b/synapse/rest/client/events.py
index 916f5230f1..782e7d14e8 100644
--- a/synapse/rest/client/events.py
+++ b/synapse/rest/client/events.py
@@ -50,7 +50,9 @@ class EventStreamRestServlet(RestServlet):
                 raise SynapseError(400, "Guest users must specify room_id param")
         room_id = parse_string(request, "room_id")
 
-        pagin_config = await PaginationConfig.from_request(self.store, request)
+        pagin_config = await PaginationConfig.from_request(
+            self.store, request, default_limit=10
+        )
         timeout = EventStreamRestServlet.DEFAULT_LONGPOLL_TIME_MS
         if b"timeout" in args:
             try:
diff --git a/synapse/rest/client/initial_sync.py b/synapse/rest/client/initial_sync.py
index cfadcb8e50..9b1bb8b521 100644
--- a/synapse/rest/client/initial_sync.py
+++ b/synapse/rest/client/initial_sync.py
@@ -39,7 +39,9 @@ class InitialSyncRestServlet(RestServlet):
         requester = await self.auth.get_user_by_req(request)
         args: Dict[bytes, List[bytes]] = request.args  # type: ignore
         as_client_event = b"raw" not in args
-        pagination_config = await PaginationConfig.from_request(self.store, request)
+        pagination_config = await PaginationConfig.from_request(
+            self.store, request, default_limit=10
+        )
         include_archived = parse_boolean(request, "archived", default=False)
         content = await self.initial_sync_handler.snapshot_all_rooms(
             user_id=requester.user.to_string(),
diff --git a/synapse/rest/client/receipts.py b/synapse/rest/client/receipts.py
index 14dec7ac4e..18a282b22c 100644
--- a/synapse/rest/client/receipts.py
+++ b/synapse/rest/client/receipts.py
@@ -15,7 +15,7 @@
 import logging
 from typing import TYPE_CHECKING, Tuple
 
-from synapse.api.constants import ReceiptTypes
+from synapse.api.constants import MAIN_TIMELINE, ReceiptTypes
 from synapse.api.errors import Codes, SynapseError
 from synapse.http.server import HttpServer
 from synapse.http.servlet import RestServlet, parse_json_object_from_request
@@ -83,7 +83,7 @@ class ReceiptRestServlet(RestServlet):
                 )
 
             # Ensure the event ID roughly correlates to the thread ID.
-            if thread_id != await self._main_store.get_thread_id(event_id):
+            if not await self._is_event_in_thread(event_id, thread_id):
                 raise SynapseError(
                     400,
                     f"event_id {event_id} is not related to thread {thread_id}",
@@ -109,6 +109,46 @@ class ReceiptRestServlet(RestServlet):
 
         return 200, {}
 
+    async def _is_event_in_thread(self, event_id: str, thread_id: str) -> bool:
+        """
+        The event must be related to the thread ID (in a vague sense) to ensure
+        clients aren't sending bogus receipts.
+
+        A thread ID is considered valid for a given event E if:
+
+        1. E has a thread relation which matches the thread ID;
+        2. E has another event which has a thread relation to E matching the
+           thread ID; or
+        3. E is recursively related (via any rel_type) to an event which
+           satisfies 1 or 2.
+
+        Given the following DAG:
+
+            A <---[m.thread]-- B <--[m.annotation]-- C
+            ^
+            |--[m.reference]-- D <--[m.annotation]-- E
+
+        It is valid to send a receipt for thread A on A, B, C, D, or E.
+
+        It is valid to send a receipt for the main timeline on A, D, and E.
+
+        Args:
+            event_id: The event ID to check.
+            thread_id: The thread ID the event is potentially part of.
+
+        Returns:
+            True if the event belongs to the given thread, otherwise False.
+        """
+
+        # If the receipt is on the main timeline, it is enough to check whether
+        # the event is directly related to a thread.
+        if thread_id == MAIN_TIMELINE:
+            return MAIN_TIMELINE == await self._main_store.get_thread_id(event_id)
+
+        # Otherwise, check if the event is directly part of a thread, or is the
+        # root message (or related to the root message) of a thread.
+        return thread_id == await self._main_store.get_thread_id_for_receipts(event_id)
+
 
 def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     ReceiptRestServlet(hs).register(http_server)
diff --git a/synapse/rest/client/relations.py b/synapse/rest/client/relations.py
index b31ce5a0d3..9dd59196d9 100644
--- a/synapse/rest/client/relations.py
+++ b/synapse/rest/client/relations.py
@@ -13,12 +13,15 @@
 # limitations under the License.
 
 import logging
+import re
 from typing import TYPE_CHECKING, Optional, Tuple
 
+from synapse.handlers.relations import ThreadsListInclude
 from synapse.http.server import HttpServer
-from synapse.http.servlet import RestServlet
+from synapse.http.servlet import RestServlet, parse_integer, parse_string
 from synapse.http.site import SynapseRequest
 from synapse.rest.client._base import client_patterns
+from synapse.storage.databases.main.relations import ThreadsNextBatch
 from synapse.streams.config import PaginationConfig
 from synapse.types import JsonDict
 
@@ -78,5 +81,45 @@ class RelationPaginationServlet(RestServlet):
         return 200, result
 
 
+class ThreadsServlet(RestServlet):
+    PATTERNS = (re.compile("^/_matrix/client/v1/rooms/(?P<room_id>[^/]*)/threads"),)
+
+    def __init__(self, hs: "HomeServer"):
+        super().__init__()
+        self.auth = hs.get_auth()
+        self.store = hs.get_datastores().main
+        self._relations_handler = hs.get_relations_handler()
+
+    async def on_GET(
+        self, request: SynapseRequest, room_id: str
+    ) -> Tuple[int, JsonDict]:
+        requester = await self.auth.get_user_by_req(request)
+
+        limit = parse_integer(request, "limit", default=5)
+        from_token_str = parse_string(request, "from")
+        include = parse_string(
+            request,
+            "include",
+            default=ThreadsListInclude.all.value,
+            allowed_values=[v.value for v in ThreadsListInclude],
+        )
+
+        # Return the relations
+        from_token = None
+        if from_token_str:
+            from_token = ThreadsNextBatch.from_string(from_token_str)
+
+        result = await self._relations_handler.get_threads(
+            requester=requester,
+            room_id=room_id,
+            include=ThreadsListInclude(include),
+            limit=limit,
+            from_token=from_token,
+        )
+
+        return 200, result
+
+
 def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     RelationPaginationServlet(hs).register(http_server)
+    ThreadsServlet(hs).register(http_server)
diff --git a/synapse/rest/client/rendezvous.py b/synapse/rest/client/rendezvous.py
new file mode 100644
index 0000000000..89176b1ffa
--- /dev/null
+++ b/synapse/rest/client/rendezvous.py
@@ -0,0 +1,74 @@
+# Copyright 2022 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import logging
+from http.client import TEMPORARY_REDIRECT
+from typing import TYPE_CHECKING, Optional
+
+from synapse.http.server import HttpServer, respond_with_redirect
+from synapse.http.servlet import RestServlet
+from synapse.http.site import SynapseRequest
+from synapse.rest.client._base import client_patterns
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
+logger = logging.getLogger(__name__)
+
+
+class RendezvousServlet(RestServlet):
+    """
+    This is a placeholder implementation of [MSC3886](https://github.com/matrix-org/matrix-spec-proposals/pull/3886)
+    simple client rendezvous capability that is used by the "Sign in with QR" functionality.
+
+    This implementation only serves as a 307 redirect to a configured server rather than being a full implementation.
+
+    A module that implements the full functionality is available at: https://pypi.org/project/matrix-http-rendezvous-synapse/.
+
+    Request:
+
+    POST /rendezvous HTTP/1.1
+    Content-Type: ...
+
+    ...
+
+    Response:
+
+    HTTP/1.1 307
+    Location: <configured endpoint>
+    """
+
+    PATTERNS = client_patterns(
+        "/org.matrix.msc3886/rendezvous$", releases=[], v1=False, unstable=True
+    )
+
+    def __init__(self, hs: "HomeServer"):
+        super().__init__()
+        redirection_target: Optional[str] = hs.config.experimental.msc3886_endpoint
+        assert (
+            redirection_target is not None
+        ), "Servlet is only registered if there is a redirection target"
+        self.endpoint = redirection_target.encode("utf-8")
+
+    async def on_POST(self, request: SynapseRequest) -> None:
+        respond_with_redirect(
+            request, self.endpoint, statusCode=TEMPORARY_REDIRECT, cors=True
+        )
+
+    # PUT, GET and DELETE are not implemented as they should be fulfilled by the redirect target.
+
+
+def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
+    if hs.config.experimental.msc3886_endpoint is not None:
+        RendezvousServlet(hs).register(http_server)
diff --git a/synapse/rest/client/room.py b/synapse/rest/client/room.py
index b6dedbed04..01e5079963 100644
--- a/synapse/rest/client/room.py
+++ b/synapse/rest/client/room.py
@@ -729,7 +729,9 @@ class RoomInitialSyncRestServlet(RestServlet):
         self, request: SynapseRequest, room_id: str
     ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
-        pagination_config = await PaginationConfig.from_request(self.store, request)
+        pagination_config = await PaginationConfig.from_request(
+            self.store, request, default_limit=10
+        )
         content = await self.initial_sync_handler.room_initial_sync(
             room_id=room_id, requester=requester, pagin_config=pagination_config
         )
diff --git a/synapse/rest/client/versions.py b/synapse/rest/client/versions.py
index d1d2e5f7e3..9b1b72c68a 100644
--- a/synapse/rest/client/versions.py
+++ b/synapse/rest/client/versions.py
@@ -76,6 +76,7 @@ class VersionsRestServlet(RestServlet):
                     "v1.1",
                     "v1.2",
                     "v1.3",
+                    "v1.4",
                 ],
                 # as per MSC1497:
                 "unstable_features": {
@@ -113,6 +114,11 @@ class VersionsRestServlet(RestServlet):
                     "org.matrix.msc3882": self.config.experimental.msc3882_enabled,
                     # Adds support for remotely enabling/disabling pushers, as per MSC3881
                     "org.matrix.msc3881": self.config.experimental.msc3881_enabled,
+                    # Adds support for filtering /messages by event relation.
+                    "org.matrix.msc3874": self.config.experimental.msc3874_enabled,
+                    # Adds support for simple HTTP rendezvous as per MSC3886
+                    "org.matrix.msc3886": self.config.experimental.msc3886_endpoint
+                    is not None,
                 },
             },
         )
diff --git a/synapse/rest/key/v2/__init__.py b/synapse/rest/key/v2/__init__.py
index 7f8c1de1ff..26403facb8 100644
--- a/synapse/rest/key/v2/__init__.py
+++ b/synapse/rest/key/v2/__init__.py
@@ -14,17 +14,20 @@
 
 from typing import TYPE_CHECKING
 
-from twisted.web.resource import Resource
-
-from .local_key_resource import LocalKey
-from .remote_key_resource import RemoteKey
+from synapse.http.server import HttpServer, JsonResource
+from synapse.rest.key.v2.local_key_resource import LocalKey
+from synapse.rest.key.v2.remote_key_resource import RemoteKey
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
 
-class KeyApiV2Resource(Resource):
+class KeyResource(JsonResource):
     def __init__(self, hs: "HomeServer"):
-        Resource.__init__(self)
-        self.putChild(b"server", LocalKey(hs))
-        self.putChild(b"query", RemoteKey(hs))
+        super().__init__(hs, canonical_json=True)
+        self.register_servlets(self, hs)
+
+    @staticmethod
+    def register_servlets(http_server: HttpServer, hs: "HomeServer") -> None:
+        LocalKey(hs).register(http_server)
+        RemoteKey(hs).register(http_server)
diff --git a/synapse/rest/key/v2/local_key_resource.py b/synapse/rest/key/v2/local_key_resource.py
index 0c9f042c84..d03e728d42 100644
--- a/synapse/rest/key/v2/local_key_resource.py
+++ b/synapse/rest/key/v2/local_key_resource.py
@@ -13,16 +13,15 @@
 # limitations under the License.
 
 import logging
-from typing import TYPE_CHECKING, Optional
+import re
+from typing import TYPE_CHECKING, Optional, Tuple
 
-from canonicaljson import encode_canonical_json
 from signedjson.sign import sign_json
 from unpaddedbase64 import encode_base64
 
-from twisted.web.resource import Resource
 from twisted.web.server import Request
 
-from synapse.http.server import respond_with_json_bytes
+from synapse.http.servlet import RestServlet
 from synapse.types import JsonDict
 
 if TYPE_CHECKING:
@@ -31,7 +30,7 @@ if TYPE_CHECKING:
 logger = logging.getLogger(__name__)
 
 
-class LocalKey(Resource):
+class LocalKey(RestServlet):
     """HTTP resource containing encoding the TLS X.509 certificate and NACL
     signature verification keys for this server::
 
@@ -61,18 +60,17 @@ class LocalKey(Resource):
         }
     """
 
-    isLeaf = True
+    PATTERNS = (re.compile("^/_matrix/key/v2/server(/(?P<key_id>[^/]*))?$"),)
 
     def __init__(self, hs: "HomeServer"):
         self.config = hs.config
         self.clock = hs.get_clock()
         self.update_response_body(self.clock.time_msec())
-        Resource.__init__(self)
 
     def update_response_body(self, time_now_msec: int) -> None:
         refresh_interval = self.config.key.key_refresh_interval
         self.valid_until_ts = int(time_now_msec + refresh_interval)
-        self.response_body = encode_canonical_json(self.response_json_object())
+        self.response_body = self.response_json_object()
 
     def response_json_object(self) -> JsonDict:
         verify_keys = {}
@@ -99,9 +97,11 @@ class LocalKey(Resource):
             json_object = sign_json(json_object, self.config.server.server_name, key)
         return json_object
 
-    def render_GET(self, request: Request) -> Optional[int]:
+    def on_GET(
+        self, request: Request, key_id: Optional[str] = None
+    ) -> Tuple[int, JsonDict]:
         time_now = self.clock.time_msec()
         # Update the expiry time if less than half the interval remains.
         if time_now + self.config.key.key_refresh_interval / 2 > self.valid_until_ts:
             self.update_response_body(time_now)
-        return respond_with_json_bytes(request, 200, self.response_body)
+        return 200, self.response_body
diff --git a/synapse/rest/key/v2/remote_key_resource.py b/synapse/rest/key/v2/remote_key_resource.py
index 7f8ad29566..19820886f5 100644
--- a/synapse/rest/key/v2/remote_key_resource.py
+++ b/synapse/rest/key/v2/remote_key_resource.py
@@ -13,15 +13,20 @@
 # limitations under the License.
 
 import logging
-from typing import TYPE_CHECKING, Dict, Set
+import re
+from typing import TYPE_CHECKING, Dict, Optional, Set, Tuple
 
 from signedjson.sign import sign_json
 
-from synapse.api.errors import Codes, SynapseError
+from twisted.web.server import Request
+
 from synapse.crypto.keyring import ServerKeyFetcher
-from synapse.http.server import DirectServeJsonResource, respond_with_json
-from synapse.http.servlet import parse_integer, parse_json_object_from_request
-from synapse.http.site import SynapseRequest
+from synapse.http.server import HttpServer
+from synapse.http.servlet import (
+    RestServlet,
+    parse_integer,
+    parse_json_object_from_request,
+)
 from synapse.types import JsonDict
 from synapse.util import json_decoder
 from synapse.util.async_helpers import yieldable_gather_results
@@ -32,7 +37,7 @@ if TYPE_CHECKING:
 logger = logging.getLogger(__name__)
 
 
-class RemoteKey(DirectServeJsonResource):
+class RemoteKey(RestServlet):
     """HTTP resource for retrieving the TLS certificate and NACL signature
     verification keys for a collection of servers. Checks that the reported
     X.509 TLS certificate matches the one used in the HTTPS connection. Checks
@@ -88,11 +93,7 @@ class RemoteKey(DirectServeJsonResource):
     }
     """
 
-    isLeaf = True
-
     def __init__(self, hs: "HomeServer"):
-        super().__init__()
-
         self.fetcher = ServerKeyFetcher(hs)
         self.store = hs.get_datastores().main
         self.clock = hs.get_clock()
@@ -101,36 +102,48 @@ class RemoteKey(DirectServeJsonResource):
         )
         self.config = hs.config
 
-    async def _async_render_GET(self, request: SynapseRequest) -> None:
-        assert request.postpath is not None
-        if len(request.postpath) == 1:
-            (server,) = request.postpath
-            query: dict = {server.decode("ascii"): {}}
-        elif len(request.postpath) == 2:
-            server, key_id = request.postpath
+    def register(self, http_server: HttpServer) -> None:
+        http_server.register_paths(
+            "GET",
+            (
+                re.compile(
+                    "^/_matrix/key/v2/query/(?P<server>[^/]*)(/(?P<key_id>[^/]*))?$"
+                ),
+            ),
+            self.on_GET,
+            self.__class__.__name__,
+        )
+        http_server.register_paths(
+            "POST",
+            (re.compile("^/_matrix/key/v2/query$"),),
+            self.on_POST,
+            self.__class__.__name__,
+        )
+
+    async def on_GET(
+        self, request: Request, server: str, key_id: Optional[str] = None
+    ) -> Tuple[int, JsonDict]:
+        if server and key_id:
             minimum_valid_until_ts = parse_integer(request, "minimum_valid_until_ts")
             arguments = {}
             if minimum_valid_until_ts is not None:
                 arguments["minimum_valid_until_ts"] = minimum_valid_until_ts
-            query = {server.decode("ascii"): {key_id.decode("ascii"): arguments}}
+            query = {server: {key_id: arguments}}
         else:
-            raise SynapseError(404, "Not found %r" % request.postpath, Codes.NOT_FOUND)
+            query = {server: {}}
 
-        await self.query_keys(request, query, query_remote_on_cache_miss=True)
+        return 200, await self.query_keys(query, query_remote_on_cache_miss=True)
 
-    async def _async_render_POST(self, request: SynapseRequest) -> None:
+    async def on_POST(self, request: Request) -> Tuple[int, JsonDict]:
         content = parse_json_object_from_request(request)
 
         query = content["server_keys"]
 
-        await self.query_keys(request, query, query_remote_on_cache_miss=True)
+        return 200, await self.query_keys(query, query_remote_on_cache_miss=True)
 
     async def query_keys(
-        self,
-        request: SynapseRequest,
-        query: JsonDict,
-        query_remote_on_cache_miss: bool = False,
-    ) -> None:
+        self, query: JsonDict, query_remote_on_cache_miss: bool = False
+    ) -> JsonDict:
         logger.info("Handling query for keys %r", query)
 
         store_queries = []
@@ -232,7 +245,7 @@ class RemoteKey(DirectServeJsonResource):
                     for server_name, keys in cache_misses.items()
                 ),
             )
-            await self.query_keys(request, query, query_remote_on_cache_miss=False)
+            return await self.query_keys(query, query_remote_on_cache_miss=False)
         else:
             signed_keys = []
             for key_json_raw in json_results:
@@ -244,6 +257,4 @@ class RemoteKey(DirectServeJsonResource):
 
                 signed_keys.append(key_json)
 
-            response = {"server_keys": signed_keys}
-
-            respond_with_json(request, 200, response, canonical_json=True)
+            return {"server_keys": signed_keys}
diff --git a/synapse/rest/synapse/client/new_user_consent.py b/synapse/rest/synapse/client/new_user_consent.py
index 1c1c7b3613..22784157e6 100644
--- a/synapse/rest/synapse/client/new_user_consent.py
+++ b/synapse/rest/synapse/client/new_user_consent.py
@@ -20,6 +20,7 @@ from synapse.api.errors import SynapseError
 from synapse.handlers.sso import get_username_mapping_session_cookie_from_request
 from synapse.http.server import DirectServeHtmlResource, respond_with_html
 from synapse.http.servlet import parse_string
+from synapse.http.site import SynapseRequest
 from synapse.types import UserID
 from synapse.util.templates import build_jinja_env
 
@@ -88,7 +89,7 @@ class NewUserConsentResource(DirectServeHtmlResource):
         html = template.render(template_params)
         respond_with_html(request, 200, html)
 
-    async def _async_render_POST(self, request: Request) -> None:
+    async def _async_render_POST(self, request: SynapseRequest) -> None:
         try:
             session_id = get_username_mapping_session_cookie_from_request(request)
         except SynapseError as e:
diff --git a/synapse/rest/well_known.py b/synapse/rest/well_known.py
index 6f7ac54c65..e2174fdfea 100644
--- a/synapse/rest/well_known.py
+++ b/synapse/rest/well_known.py
@@ -18,6 +18,7 @@ from twisted.web.resource import Resource
 from twisted.web.server import Request
 
 from synapse.http.server import set_cors_headers
+from synapse.http.site import SynapseRequest
 from synapse.types import JsonDict
 from synapse.util import json_encoder
 from synapse.util.stringutils import parse_server_name
@@ -63,7 +64,7 @@ class ClientWellKnownResource(Resource):
         Resource.__init__(self)
         self._well_known_builder = WellKnownBuilder(hs)
 
-    def render_GET(self, request: Request) -> bytes:
+    def render_GET(self, request: SynapseRequest) -> bytes:
         set_cors_headers(request)
         r = self._well_known_builder.get_well_known()
         if not r:
diff --git a/synapse/storage/database.py b/synapse/storage/database.py
index 7bb21f8f81..4717c9728a 100644
--- a/synapse/storage/database.py
+++ b/synapse/storage/database.py
@@ -1658,7 +1658,7 @@ class DatabasePool:
             table: string giving the table name
             keyvalues: dict of column names and values to select the row with
             retcol: string giving the name of the column to return
-            allow_none: If true, return None instead of failing if the SELECT
+            allow_none: If true, return None instead of raising StoreError if the SELECT
                 statement returns no rows
             desc: description of the transaction, for logging and metrics
         """
diff --git a/synapse/storage/databases/main/cache.py b/synapse/storage/databases/main/cache.py
index 3b8ed1f7ee..ddb7397714 100644
--- a/synapse/storage/databases/main/cache.py
+++ b/synapse/storage/databases/main/cache.py
@@ -244,12 +244,18 @@ class CacheInvalidationWorkerStore(SQLBaseStore):
             # redacted.
             self._attempt_to_invalidate_cache("get_relations_for_event", (redacts,))
             self._attempt_to_invalidate_cache("get_applicable_edit", (redacts,))
+            self._attempt_to_invalidate_cache("get_thread_id", (redacts,))
+            self._attempt_to_invalidate_cache("get_thread_id_for_receipts", (redacts,))
 
         if etype == EventTypes.Member:
             self._membership_stream_cache.entity_has_changed(state_key, stream_ordering)
             self._attempt_to_invalidate_cache(
                 "get_invited_rooms_for_local_user", (state_key,)
             )
+            self._attempt_to_invalidate_cache(
+                "get_rooms_for_user_with_stream_ordering", (state_key,)
+            )
+            self._attempt_to_invalidate_cache("get_rooms_for_user", (state_key,))
 
         if relates_to:
             self._attempt_to_invalidate_cache("get_relations_for_event", (relates_to,))
@@ -259,9 +265,7 @@ class CacheInvalidationWorkerStore(SQLBaseStore):
             self._attempt_to_invalidate_cache("get_applicable_edit", (relates_to,))
             self._attempt_to_invalidate_cache("get_thread_summary", (relates_to,))
             self._attempt_to_invalidate_cache("get_thread_participated", (relates_to,))
-            self._attempt_to_invalidate_cache(
-                "get_mutual_event_relations_for_rel_type", (relates_to,)
-            )
+            self._attempt_to_invalidate_cache("get_threads", (room_id,))
 
     async def invalidate_cache_and_stream(
         self, cache_name: str, keys: Tuple[Any, ...]
diff --git a/synapse/storage/databases/main/devices.py b/synapse/storage/databases/main/devices.py
index 18358eca46..830b076a32 100644
--- a/synapse/storage/databases/main/devices.py
+++ b/synapse/storage/databases/main/devices.py
@@ -539,9 +539,11 @@ class DeviceWorkerStore(RoomMemberWorkerStore, EndToEndKeyWorkerStore):
                     "device_id": device_id,
                     "prev_id": [prev_id] if prev_id else [],
                     "stream_id": stream_id,
-                    "org.matrix.opentracing_context": opentracing_context,
                 }
 
+                if opentracing_context != "{}":
+                    result["org.matrix.opentracing_context"] = opentracing_context
+
                 prev_id = stream_id
 
                 if device is not None:
@@ -549,7 +551,11 @@ class DeviceWorkerStore(RoomMemberWorkerStore, EndToEndKeyWorkerStore):
                     if keys:
                         result["keys"] = keys
 
-                    device_display_name = device.display_name
+                    device_display_name = None
+                    if (
+                        self.hs.config.federation.allow_device_name_lookup_over_federation
+                    ):
+                        device_display_name = device.display_name
                     if device_display_name:
                         result["device_display_name"] = device_display_name
                 else:
diff --git a/synapse/storage/databases/main/event_federation.py b/synapse/storage/databases/main/event_federation.py
index 6b9a629edd..309a4ba664 100644
--- a/synapse/storage/databases/main/event_federation.py
+++ b/synapse/storage/databases/main/event_federation.py
@@ -1501,6 +1501,12 @@ class EventFederationWorkerStore(SignatureWorkerStore, EventsWorkerStore, SQLBas
             event_id: The event that failed to be fetched or processed
             cause: The error message or reason that we failed to pull the event
         """
+        logger.debug(
+            "record_event_failed_pull_attempt room_id=%s, event_id=%s, cause=%s",
+            room_id,
+            event_id,
+            cause,
+        )
         await self.db_pool.runInteraction(
             "record_event_failed_pull_attempt",
             self._record_event_failed_pull_attempt_upsert_txn,
@@ -1530,6 +1536,54 @@ class EventFederationWorkerStore(SignatureWorkerStore, EventsWorkerStore, SQLBas
 
         txn.execute(sql, (room_id, event_id, 1, self._clock.time_msec(), cause))
 
+    @trace
+    async def get_event_ids_to_not_pull_from_backoff(
+        self,
+        room_id: str,
+        event_ids: Collection[str],
+    ) -> List[str]:
+        """
+        Filter down the events to ones that we've failed to pull before recently. Uses
+        exponential backoff.
+
+        Args:
+            room_id: The room that the events belong to
+            event_ids: A list of events to filter down
+
+        Returns:
+            List of event_ids that should not be attempted to be pulled
+        """
+        event_failed_pull_attempts = await self.db_pool.simple_select_many_batch(
+            table="event_failed_pull_attempts",
+            column="event_id",
+            iterable=event_ids,
+            keyvalues={},
+            retcols=(
+                "event_id",
+                "last_attempt_ts",
+                "num_attempts",
+            ),
+            desc="get_event_ids_to_not_pull_from_backoff",
+        )
+
+        current_time = self._clock.time_msec()
+        return [
+            event_failed_pull_attempt["event_id"]
+            for event_failed_pull_attempt in event_failed_pull_attempts
+            # Exponential back-off (up to the upper bound) so we don't try to
+            # pull the same event over and over. ex. 2hr, 4hr, 8hr, 16hr, etc.
+            if current_time
+            < event_failed_pull_attempt["last_attempt_ts"]
+            + (
+                2
+                ** min(
+                    event_failed_pull_attempt["num_attempts"],
+                    BACKFILL_EVENT_EXPONENTIAL_BACKOFF_MAXIMUM_DOUBLING_STEPS,
+                )
+            )
+            * BACKFILL_EVENT_EXPONENTIAL_BACKOFF_STEP_MILLISECONDS
+        ]
+
     async def get_missing_events(
         self,
         room_id: str,
diff --git a/synapse/storage/databases/main/event_push_actions.py b/synapse/storage/databases/main/event_push_actions.py
index 332e13d1c9..b283ab0f9c 100644
--- a/synapse/storage/databases/main/event_push_actions.py
+++ b/synapse/storage/databases/main/event_push_actions.py
@@ -294,6 +294,44 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
             self._background_backfill_thread_id,
         )
 
+        # Indexes which will be used to quickly make the thread_id column non-null.
+        self.db_pool.updates.register_background_index_update(
+            "event_push_actions_thread_id_null",
+            index_name="event_push_actions_thread_id_null",
+            table="event_push_actions",
+            columns=["thread_id"],
+            where_clause="thread_id IS NULL",
+        )
+        self.db_pool.updates.register_background_index_update(
+            "event_push_summary_thread_id_null",
+            index_name="event_push_summary_thread_id_null",
+            table="event_push_summary",
+            columns=["thread_id"],
+            where_clause="thread_id IS NULL",
+        )
+
+        # Check ASAP (and then later, every 1s) to see if we have finished
+        # background updates the event_push_actions and event_push_summary tables.
+        self._clock.call_later(0.0, self._check_event_push_backfill_thread_id)
+        self._event_push_backfill_thread_id_done = False
+
+    @wrap_as_background_process("check_event_push_backfill_thread_id")
+    async def _check_event_push_backfill_thread_id(self) -> None:
+        """
+        Has thread_id finished backfilling?
+
+        If not, we need to just-in-time update it so the queries work.
+        """
+        done = await self.db_pool.updates.has_completed_background_update(
+            "event_push_backfill_thread_id"
+        )
+
+        if done:
+            self._event_push_backfill_thread_id_done = True
+        else:
+            # Reschedule to run.
+            self._clock.call_later(15.0, self._check_event_push_backfill_thread_id)
+
     async def _background_backfill_thread_id(
         self, progress: JsonDict, batch_size: int
     ) -> int:
@@ -310,11 +348,11 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
         event_push_actions_done = progress.get("event_push_actions_done", False)
 
         def add_thread_id_txn(
-            txn: LoggingTransaction, table_name: str, start_stream_ordering: int
+            txn: LoggingTransaction, start_stream_ordering: int
         ) -> int:
-            sql = f"""
+            sql = """
             SELECT stream_ordering
-            FROM {table_name}
+            FROM event_push_actions
             WHERE
                 thread_id IS NULL
                 AND stream_ordering > ?
@@ -326,7 +364,7 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
             # No more rows to process.
             rows = txn.fetchall()
             if not rows:
-                progress[f"{table_name}_done"] = True
+                progress["event_push_actions_done"] = True
                 self.db_pool.updates._background_update_progress_txn(
                     txn, "event_push_backfill_thread_id", progress
                 )
@@ -335,16 +373,65 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
             # Update the thread ID for any of those rows.
             max_stream_ordering = rows[-1][0]
 
-            sql = f"""
-            UPDATE {table_name}
+            sql = """
+            UPDATE event_push_actions
             SET thread_id = 'main'
-            WHERE stream_ordering <= ? AND thread_id IS NULL
+            WHERE ? < stream_ordering AND stream_ordering <= ? AND thread_id IS NULL
             """
-            txn.execute(sql, (max_stream_ordering,))
+            txn.execute(
+                sql,
+                (
+                    start_stream_ordering,
+                    max_stream_ordering,
+                ),
+            )
 
             # Update progress.
             processed_rows = txn.rowcount
-            progress[f"max_{table_name}_stream_ordering"] = max_stream_ordering
+            progress["max_event_push_actions_stream_ordering"] = max_stream_ordering
+            self.db_pool.updates._background_update_progress_txn(
+                txn, "event_push_backfill_thread_id", progress
+            )
+
+            return processed_rows
+
+        def add_thread_id_summary_txn(txn: LoggingTransaction) -> int:
+            min_user_id = progress.get("max_summary_user_id", "")
+            min_room_id = progress.get("max_summary_room_id", "")
+
+            # Slightly overcomplicated query for getting the Nth user ID / room
+            # ID tuple, or the last if there are less than N remaining.
+            sql = """
+            SELECT user_id, room_id FROM (
+                SELECT user_id, room_id FROM event_push_summary
+                WHERE (user_id, room_id) > (?, ?)
+                    AND thread_id IS NULL
+                ORDER BY user_id, room_id
+                LIMIT ?
+            ) AS e
+            ORDER BY user_id DESC, room_id DESC
+            LIMIT 1
+            """
+
+            txn.execute(sql, (min_user_id, min_room_id, batch_size))
+            row = txn.fetchone()
+            if not row:
+                return 0
+
+            max_user_id, max_room_id = row
+
+            sql = """
+            UPDATE event_push_summary
+            SET thread_id = 'main'
+            WHERE
+                (?, ?) < (user_id, room_id) AND (user_id, room_id) <= (?, ?)
+                AND thread_id IS NULL
+            """
+            txn.execute(sql, (min_user_id, min_room_id, max_user_id, max_room_id))
+            processed_rows = txn.rowcount
+
+            progress["max_summary_user_id"] = max_user_id
+            progress["max_summary_room_id"] = max_room_id
             self.db_pool.updates._background_update_progress_txn(
                 txn, "event_push_backfill_thread_id", progress
             )
@@ -360,15 +447,12 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
             result = await self.db_pool.runInteraction(
                 "event_push_backfill_thread_id",
                 add_thread_id_txn,
-                "event_push_actions",
                 progress.get("max_event_push_actions_stream_ordering", 0),
             )
         else:
             result = await self.db_pool.runInteraction(
                 "event_push_backfill_thread_id",
-                add_thread_id_txn,
-                "event_push_summary",
-                progress.get("max_event_push_summary_stream_ordering", 0),
+                add_thread_id_summary_txn,
             )
 
             # Only done after the event_push_summary table is done.
@@ -480,6 +564,25 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
             (ReceiptTypes.READ, ReceiptTypes.READ_PRIVATE),
         )
 
+        # First ensure that the existing rows have an updated thread_id field.
+        if not self._event_push_backfill_thread_id_done:
+            txn.execute(
+                """
+                UPDATE event_push_summary
+                SET thread_id = ?
+                WHERE room_id = ? AND user_id = ? AND thread_id is NULL
+                """,
+                (MAIN_TIMELINE, room_id, user_id),
+            )
+            txn.execute(
+                """
+                UPDATE event_push_actions
+                SET thread_id = ?
+                WHERE room_id = ? AND user_id = ? AND thread_id is NULL
+                """,
+                (MAIN_TIMELINE, room_id, user_id),
+            )
+
         # First we pull the counts from the summary table.
         #
         # We check that `last_receipt_stream_ordering` matches the stream ordering of the
@@ -1295,6 +1398,25 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
                 (room_id, user_id, stream_ordering, *thread_args),
             )
 
+            # First ensure that the existing rows have an updated thread_id field.
+            if not self._event_push_backfill_thread_id_done:
+                txn.execute(
+                    """
+                    UPDATE event_push_summary
+                    SET thread_id = ?
+                    WHERE room_id = ? AND user_id = ? AND thread_id is NULL
+                    """,
+                    (MAIN_TIMELINE, room_id, user_id),
+                )
+                txn.execute(
+                    """
+                    UPDATE event_push_actions
+                    SET thread_id = ?
+                    WHERE room_id = ? AND user_id = ? AND thread_id is NULL
+                    """,
+                    (MAIN_TIMELINE, room_id, user_id),
+                )
+
             # Fetch the notification counts between the stream ordering of the
             # latest receipt and what was previously summarised.
             unread_counts = self._get_notif_unread_count_for_user_room(
@@ -1429,6 +1551,19 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
             rotate_to_stream_ordering: The new maximum event stream ordering to summarise.
         """
 
+        # Ensure that any new actions have an updated thread_id.
+        if not self._event_push_backfill_thread_id_done:
+            txn.execute(
+                """
+                UPDATE event_push_actions
+                SET thread_id = ?
+                WHERE ? < stream_ordering AND stream_ordering <= ? AND thread_id IS NULL
+                """,
+                (MAIN_TIMELINE, old_rotate_stream_ordering, rotate_to_stream_ordering),
+            )
+
+        # XXX Do we need to update summaries here too?
+
         # Calculate the new counts that should be upserted into event_push_summary
         sql = """
             SELECT user_id, room_id, thread_id,
@@ -1491,6 +1626,20 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
 
         logger.info("Rotating notifications, handling %d rows", len(summaries))
 
+        # Ensure that any updated threads have the proper thread_id.
+        if not self._event_push_backfill_thread_id_done:
+            txn.execute_batch(
+                """
+                UPDATE event_push_summary
+                SET thread_id = ?
+                WHERE room_id = ? AND user_id = ? AND thread_id is NULL
+                """,
+                [
+                    (MAIN_TIMELINE, room_id, user_id)
+                    for user_id, room_id, _ in summaries
+                ],
+            )
+
         self.db_pool.simple_upsert_many_txn(
             txn,
             table="event_push_summary",
diff --git a/synapse/storage/databases/main/events.py b/synapse/storage/databases/main/events.py
index 3e15827986..6698cbf664 100644
--- a/synapse/storage/databases/main/events.py
+++ b/synapse/storage/databases/main/events.py
@@ -35,7 +35,7 @@ import attr
 from prometheus_client import Counter
 
 import synapse.metrics
-from synapse.api.constants import EventContentFields, EventTypes
+from synapse.api.constants import EventContentFields, EventTypes, RelationTypes
 from synapse.api.errors import Codes, SynapseError
 from synapse.api.room_versions import RoomVersions
 from synapse.events import EventBase, relation_from_event
@@ -1616,7 +1616,7 @@ class PersistEventsStore:
                 )
 
                 # Remove from relations table.
-                self._handle_redact_relations(txn, event.redacts)
+                self._handle_redact_relations(txn, event.room_id, event.redacts)
 
         # Update the event_forward_extremities, event_backward_extremities and
         # event_edges tables.
@@ -1866,6 +1866,34 @@ class PersistEventsStore:
             },
         )
 
+        if relation.rel_type == RelationTypes.THREAD:
+            # Upsert into the threads table, but only overwrite the value if the
+            # new event is of a later topological order OR if the topological
+            # ordering is equal, but the stream ordering is later.
+            sql = """
+            INSERT INTO threads (room_id, thread_id, latest_event_id, topological_ordering, stream_ordering)
+            VALUES (?, ?, ?, ?, ?)
+            ON CONFLICT (room_id, thread_id)
+            DO UPDATE SET
+                latest_event_id = excluded.latest_event_id,
+                topological_ordering = excluded.topological_ordering,
+                stream_ordering = excluded.stream_ordering
+            WHERE
+                threads.topological_ordering <= excluded.topological_ordering AND
+                threads.stream_ordering < excluded.stream_ordering
+            """
+
+            txn.execute(
+                sql,
+                (
+                    event.room_id,
+                    relation.parent_id,
+                    event.event_id,
+                    event.depth,
+                    event.internal_metadata.stream_ordering,
+                ),
+            )
+
     def _handle_insertion_event(
         self, txn: LoggingTransaction, event: EventBase
     ) -> None:
@@ -1989,13 +2017,14 @@ class PersistEventsStore:
         txn.execute(sql, (batch_id,))
 
     def _handle_redact_relations(
-        self, txn: LoggingTransaction, redacted_event_id: str
+        self, txn: LoggingTransaction, room_id: str, redacted_event_id: str
     ) -> None:
         """Handles receiving a redaction and checking whether the redacted event
         has any relations which must be removed from the database.
 
         Args:
             txn
+            room_id: The room ID of the event that was redacted.
             redacted_event_id: The event that was redacted.
         """
 
@@ -2025,9 +2054,7 @@ class PersistEventsStore:
                 txn, self.store.get_thread_participated, (redacted_relates_to,)
             )
             self.store._invalidate_cache_and_stream(
-                txn,
-                self.store.get_mutual_event_relations_for_rel_type,
-                (redacted_relates_to,),
+                txn, self.store.get_threads, (room_id,)
             )
 
         self.db_pool.simple_delete_txn(
diff --git a/synapse/storage/databases/main/events_worker.py b/synapse/storage/databases/main/events_worker.py
index 7cdc9fe98f..69fea452ad 100644
--- a/synapse/storage/databases/main/events_worker.py
+++ b/synapse/storage/databases/main/events_worker.py
@@ -374,7 +374,7 @@ class EventsWorkerStore(SQLBaseStore):
                 If there is a mismatch, behave as per allow_none.
 
         Returns:
-            The event, or None if the event was not found.
+            The event, or None if the event was not found and allow_none is `True`.
         """
         if not isinstance(event_id, str):
             raise TypeError("Invalid event event_id %r" % (event_id,))
@@ -474,7 +474,7 @@ class EventsWorkerStore(SQLBaseStore):
             return []
 
         # there may be duplicates so we cast the list to a set
-        event_entry_map = await self._get_events_from_cache_or_db(
+        event_entry_map = await self.get_unredacted_events_from_cache_or_db(
             set(event_ids), allow_rejected=allow_rejected
         )
 
@@ -509,7 +509,9 @@ class EventsWorkerStore(SQLBaseStore):
                     continue
 
                 redacted_event_id = entry.event.redacts
-                event_map = await self._get_events_from_cache_or_db([redacted_event_id])
+                event_map = await self.get_unredacted_events_from_cache_or_db(
+                    [redacted_event_id]
+                )
                 original_event_entry = event_map.get(redacted_event_id)
                 if not original_event_entry:
                     # we don't have the redacted event (or it was rejected).
@@ -588,11 +590,16 @@ class EventsWorkerStore(SQLBaseStore):
         return events
 
     @cancellable
-    async def _get_events_from_cache_or_db(
-        self, event_ids: Iterable[str], allow_rejected: bool = False
+    async def get_unredacted_events_from_cache_or_db(
+        self,
+        event_ids: Iterable[str],
+        allow_rejected: bool = False,
     ) -> Dict[str, EventCacheEntry]:
         """Fetch a bunch of events from the cache or the database.
 
+        Note that the events pulled by this function will not have any redactions
+        applied, and no guarantee is made about the ordering of the events returned.
+
         If events are pulled from the database, they will be cached for future lookups.
 
         Unknown events are omitted from the response.
@@ -1495,21 +1502,15 @@ class EventsWorkerStore(SQLBaseStore):
         Returns:
              a dict {event_id -> bool}
         """
-        # if the event cache contains the event, obviously we've seen it.
-
-        cache_results = {
-            event_id
-            for event_id in event_ids
-            if await self._get_event_cache.contains((event_id,))
-        }
-        results = dict.fromkeys(cache_results, True)
-        remaining = [
-            event_id for event_id in event_ids if event_id not in cache_results
-        ]
-        if not remaining:
-            return results
+        # TODO: We used to query the _get_event_cache here as a fast-path before
+        #  hitting the database. For if an event were in the cache, we've presumably
+        #  seen it before.
+        #
+        #  But this is currently an invalid assumption due to the _get_event_cache
+        #  not being invalidated when purging events from a room. The optimisation can
+        #  be re-added after https://github.com/matrix-org/synapse/issues/13476
 
-        def have_seen_events_txn(txn: LoggingTransaction) -> None:
+        def have_seen_events_txn(txn: LoggingTransaction) -> Dict[str, bool]:
             # we deliberately do *not* query the database for room_id, to make the
             # query an index-only lookup on `events_event_id_key`.
             #
@@ -1517,16 +1518,17 @@ class EventsWorkerStore(SQLBaseStore):
 
             sql = "SELECT event_id FROM events AS e WHERE "
             clause, args = make_in_list_sql_clause(
-                txn.database_engine, "e.event_id", remaining
+                txn.database_engine, "e.event_id", event_ids
             )
             txn.execute(sql + clause, args)
             found_events = {eid for eid, in txn}
 
             # ... and then we can update the results for each key
-            results.update({eid: (eid in found_events) for eid in remaining})
+            return {eid: (eid in found_events) for eid in event_ids}
 
-        await self.db_pool.runInteraction("have_seen_events", have_seen_events_txn)
-        return results
+        return await self.db_pool.runInteraction(
+            "have_seen_events", have_seen_events_txn
+        )
 
     @cached(max_entries=100000, tree=True)
     async def have_seen_event(self, room_id: str, event_id: str) -> bool:
@@ -1969,12 +1971,17 @@ class EventsWorkerStore(SQLBaseStore):
 
         Args:
             room_id: room where the event lives
-            event_id: event to check
+            event: event to check (can't be an `outlier`)
 
         Returns:
             Boolean indicating whether it's an extremity
         """
 
+        assert not event.internal_metadata.is_outlier(), (
+            "is_event_next_to_backward_gap(...) can't be used with `outlier` events. "
+            "This function relies on `event_backward_extremities` which won't be filled in for `outliers`."
+        )
+
         def is_event_next_to_backward_gap_txn(txn: LoggingTransaction) -> bool:
             # If the event in question has any of its prev_events listed as a
             # backward extremity, it's next to a gap.
@@ -2024,12 +2031,17 @@ class EventsWorkerStore(SQLBaseStore):
 
         Args:
             room_id: room where the event lives
-            event_id: event to check
+            event: event to check (can't be an `outlier`)
 
         Returns:
             Boolean indicating whether it's an extremity
         """
 
+        assert not event.internal_metadata.is_outlier(), (
+            "is_event_next_to_forward_gap(...) can't be used with `outlier` events. "
+            "This function relies on `event_edges` and `event_forward_extremities` which won't be filled in for `outliers`."
+        )
+
         def is_event_next_to_gap_txn(txn: LoggingTransaction) -> bool:
             # If the event in question is a forward extremity, we will just
             # consider any potential forward gap as not a gap since it's one of
@@ -2110,13 +2122,33 @@ class EventsWorkerStore(SQLBaseStore):
             The closest event_id otherwise None if we can't find any event in
             the given direction.
         """
+        if direction == "b":
+            # Find closest event *before* a given timestamp. We use descending
+            # (which gives values largest to smallest) because we want the
+            # largest possible timestamp *before* the given timestamp.
+            comparison_operator = "<="
+            order = "DESC"
+        else:
+            # Find closest event *after* a given timestamp. We use ascending
+            # (which gives values smallest to largest) because we want the
+            # closest possible timestamp *after* the given timestamp.
+            comparison_operator = ">="
+            order = "ASC"
 
-        sql_template = """
+        sql_template = f"""
             SELECT event_id FROM events
             LEFT JOIN rejections USING (event_id)
             WHERE
-                origin_server_ts %s ?
-                AND room_id = ?
+                room_id = ?
+                AND origin_server_ts {comparison_operator} ?
+                /**
+                 * Make sure the event isn't an `outlier` because we have no way
+                 * to later check whether it's next to a gap. `outliers` do not
+                 * have entries in the `event_edges`, `event_forward_extremeties`,
+                 * and `event_backward_extremities` tables to check against
+                 * (used by `is_event_next_to_backward_gap` and `is_event_next_to_forward_gap`).
+                 */
+                AND NOT outlier
                 /* Make sure event is not rejected */
                 AND rejections.event_id IS NULL
             /**
@@ -2126,27 +2158,14 @@ class EventsWorkerStore(SQLBaseStore):
              * Finally, we can tie-break based on when it was received on the server
              * (`stream_ordering`).
              */
-            ORDER BY origin_server_ts %s, depth %s, stream_ordering %s
+            ORDER BY origin_server_ts {order}, depth {order}, stream_ordering {order}
             LIMIT 1;
         """
 
         def get_event_id_for_timestamp_txn(txn: LoggingTransaction) -> Optional[str]:
-            if direction == "b":
-                # Find closest event *before* a given timestamp. We use descending
-                # (which gives values largest to smallest) because we want the
-                # largest possible timestamp *before* the given timestamp.
-                comparison_operator = "<="
-                order = "DESC"
-            else:
-                # Find closest event *after* a given timestamp. We use ascending
-                # (which gives values smallest to largest) because we want the
-                # closest possible timestamp *after* the given timestamp.
-                comparison_operator = ">="
-                order = "ASC"
-
             txn.execute(
-                sql_template % (comparison_operator, order, order, order),
-                (timestamp, room_id),
+                sql_template,
+                (room_id, timestamp),
             )
             row = txn.fetchone()
             if row:
diff --git a/synapse/storage/databases/main/push_rule.py b/synapse/storage/databases/main/push_rule.py
index 8295322b0e..51416b2236 100644
--- a/synapse/storage/databases/main/push_rule.py
+++ b/synapse/storage/databases/main/push_rule.py
@@ -29,7 +29,6 @@ from typing import (
 )
 
 from synapse.api.errors import StoreError
-from synapse.config.homeserver import ExperimentalConfig
 from synapse.replication.slave.storage._slaved_id_tracker import SlavedIdTracker
 from synapse.storage._base import SQLBaseStore
 from synapse.storage.database import (
@@ -63,9 +62,7 @@ logger = logging.getLogger(__name__)
 
 
 def _load_rules(
-    rawrules: List[JsonDict],
-    enabled_map: Dict[str, bool],
-    experimental_config: ExperimentalConfig,
+    rawrules: List[JsonDict], enabled_map: Dict[str, bool]
 ) -> FilteredPushRules:
     """Take the DB rows returned from the DB and convert them into a full
     `FilteredPushRules` object.
@@ -83,9 +80,7 @@ def _load_rules(
 
     push_rules = PushRules(ruleslist)
 
-    filtered_rules = FilteredPushRules(
-        push_rules, enabled_map, msc3772_enabled=experimental_config.msc3772_enabled
-    )
+    filtered_rules = FilteredPushRules(push_rules, enabled_map)
 
     return filtered_rules
 
@@ -165,7 +160,7 @@ class PushRulesWorkerStore(
 
         enabled_map = await self.get_push_rules_enabled_for_user(user_id)
 
-        return _load_rules(rows, enabled_map, self.hs.config.experimental)
+        return _load_rules(rows, enabled_map)
 
     async def get_push_rules_enabled_for_user(self, user_id: str) -> Dict[str, bool]:
         results = await self.db_pool.simple_select_list(
@@ -224,9 +219,7 @@ class PushRulesWorkerStore(
         results: Dict[str, FilteredPushRules] = {}
 
         for user_id, rules in raw_rules.items():
-            results[user_id] = _load_rules(
-                rules, enabled_map_by_user.get(user_id, {}), self.hs.config.experimental
-            )
+            results[user_id] = _load_rules(rules, enabled_map_by_user.get(user_id, {}))
 
         return results
 
diff --git a/synapse/storage/databases/main/receipts.py b/synapse/storage/databases/main/receipts.py
index 246f78ac1f..dc6989527e 100644
--- a/synapse/storage/databases/main/receipts.py
+++ b/synapse/storage/databases/main/receipts.py
@@ -418,6 +418,8 @@ class ReceiptsWorkerStore(SQLBaseStore):
             receipt_type = event_entry.setdefault(row["receipt_type"], {})
 
             receipt_type[row["user_id"]] = db_to_json(row["data"])
+            if row["thread_id"]:
+                receipt_type[row["user_id"]]["thread_id"] = row["thread_id"]
 
         results = {
             room_id: [results[room_id]] if room_id in results else []
diff --git a/synapse/storage/databases/main/relations.py b/synapse/storage/databases/main/relations.py
index 116abef9de..1de62ee9df 100644
--- a/synapse/storage/databases/main/relations.py
+++ b/synapse/storage/databases/main/relations.py
@@ -14,6 +14,7 @@
 
 import logging
 from typing import (
+    TYPE_CHECKING,
     Collection,
     Dict,
     FrozenSet,
@@ -28,19 +29,48 @@ from typing import (
 
 import attr
 
-from synapse.api.constants import RelationTypes
+from synapse.api.constants import MAIN_TIMELINE, RelationTypes
+from synapse.api.errors import SynapseError
 from synapse.events import EventBase
 from synapse.storage._base import SQLBaseStore
-from synapse.storage.database import LoggingTransaction, make_in_list_sql_clause
+from synapse.storage.database import (
+    DatabasePool,
+    LoggingDatabaseConnection,
+    LoggingTransaction,
+    make_in_list_sql_clause,
+)
 from synapse.storage.databases.main.stream import generate_pagination_where_clause
 from synapse.storage.engines import PostgresEngine
 from synapse.types import JsonDict, RoomStreamToken, StreamKeyType, StreamToken
 from synapse.util.caches.descriptors import cached, cachedList
 
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
 logger = logging.getLogger(__name__)
 
 
 @attr.s(slots=True, frozen=True, auto_attribs=True)
+class ThreadsNextBatch:
+    topological_ordering: int
+    stream_ordering: int
+
+    def __str__(self) -> str:
+        return f"{self.topological_ordering}_{self.stream_ordering}"
+
+    @classmethod
+    def from_string(cls, string: str) -> "ThreadsNextBatch":
+        """
+        Creates a ThreadsNextBatch from its textual representation.
+        """
+        try:
+            keys = (int(s) for s in string.split("_"))
+            return cls(*keys)
+        except Exception:
+            raise SynapseError(400, "Invalid threads token")
+
+
+@attr.s(slots=True, frozen=True, auto_attribs=True)
 class _RelatedEvent:
     """
     Contains enough information about a related event in order to properly filter
@@ -56,6 +86,76 @@ class _RelatedEvent:
 
 
 class RelationsWorkerStore(SQLBaseStore):
+    def __init__(
+        self,
+        database: DatabasePool,
+        db_conn: LoggingDatabaseConnection,
+        hs: "HomeServer",
+    ):
+        super().__init__(database, db_conn, hs)
+
+        self.db_pool.updates.register_background_update_handler(
+            "threads_backfill", self._backfill_threads
+        )
+
+    async def _backfill_threads(self, progress: JsonDict, batch_size: int) -> int:
+        """Backfill the threads table."""
+
+        def threads_backfill_txn(txn: LoggingTransaction) -> int:
+            last_thread_id = progress.get("last_thread_id", "")
+
+            # Get the latest event in each thread by topo ordering / stream ordering.
+            #
+            # Note that the MAX(event_id) is needed to abide by the rules of group by,
+            # but doesn't actually do anything since there should only be a single event
+            # ID per topo/stream ordering pair.
+            sql = f"""
+            SELECT room_id, relates_to_id, MAX(topological_ordering), MAX(stream_ordering), MAX(event_id)
+            FROM event_relations
+            INNER JOIN events USING (event_id)
+            WHERE
+                relates_to_id > ? AND
+                relation_type = '{RelationTypes.THREAD}'
+            GROUP BY room_id, relates_to_id
+            ORDER BY relates_to_id
+            LIMIT ?
+            """
+            txn.execute(sql, (last_thread_id, batch_size))
+
+            # No more rows to process.
+            rows = txn.fetchall()
+            if not rows:
+                return 0
+
+            # Insert the rows into the threads table. If a matching thread already exists,
+            # assume it is from a newer event.
+            sql = """
+            INSERT INTO threads (room_id, thread_id, topological_ordering, stream_ordering, latest_event_id)
+            VALUES %s
+            ON CONFLICT (room_id, thread_id)
+            DO NOTHING
+            """
+            if isinstance(txn.database_engine, PostgresEngine):
+                txn.execute_values(sql % ("?",), rows, fetch=False)
+            else:
+                txn.execute_batch(sql % ("(?, ?, ?, ?, ?)",), rows)
+
+            # Mark the progress.
+            self.db_pool.updates._background_update_progress_txn(
+                txn, "threads_backfill", {"last_thread_id": rows[-1][1]}
+            )
+
+            return txn.rowcount
+
+        result = await self.db_pool.runInteraction(
+            "threads_backfill", threads_backfill_txn
+        )
+
+        if not result:
+            await self.db_pool.updates._end_background_update("threads_backfill")
+
+        return result
+
     @cached(uncached_args=("event",), tree=True)
     async def get_relations_for_event(
         self,
@@ -776,95 +876,194 @@ class RelationsWorkerStore(SQLBaseStore):
             "get_if_user_has_annotated_event", _get_if_user_has_annotated_event
         )
 
-    @cached(iterable=True)
-    async def get_mutual_event_relations_for_rel_type(
-        self, event_id: str, relation_type: str
-    ) -> Set[Tuple[str, str]]:
-        raise NotImplementedError()
-
-    @cachedList(
-        cached_method_name="get_mutual_event_relations_for_rel_type",
-        list_name="relation_types",
-    )
-    async def get_mutual_event_relations(
-        self, event_id: str, relation_types: Collection[str]
-    ) -> Dict[str, Set[Tuple[str, str]]]:
-        """
-        Fetch event metadata for events which related to the same event as the given event.
-
-        If the given event has no relation information, returns an empty dictionary.
+    @cached(tree=True)
+    async def get_threads(
+        self,
+        room_id: str,
+        limit: int = 5,
+        from_token: Optional[ThreadsNextBatch] = None,
+    ) -> Tuple[List[str], Optional[ThreadsNextBatch]]:
+        """Get a list of thread IDs, ordered by topological ordering of their
+        latest reply.
 
         Args:
-            event_id: The event ID which is targeted by relations.
-            relation_types: The relation types to check for mutual relations.
+            room_id: The room the event belongs to.
+            limit: Only fetch the most recent `limit` threads.
+            from_token: Fetch rows from a previous next_batch, or from the start if None.
 
         Returns:
-            A dictionary of relation type to:
-                A set of tuples of:
-                    The sender
-                    The event type
+            A tuple of:
+                A list of thread root event IDs.
+
+                The next_batch, if one exists.
         """
-        rel_type_sql, rel_type_args = make_in_list_sql_clause(
-            self.database_engine, "relation_type", relation_types
-        )
+        # Generate the pagination clause, if necessary.
+        #
+        # Find any threads where the latest reply is equal / before the last
+        # thread's topo ordering and earlier in stream ordering.
+        pagination_clause = ""
+        pagination_args: tuple = ()
+        if from_token:
+            pagination_clause = "AND topological_ordering <= ? AND stream_ordering < ?"
+            pagination_args = (
+                from_token.topological_ordering,
+                from_token.stream_ordering,
+            )
 
         sql = f"""
-            SELECT DISTINCT relation_type, sender, type FROM event_relations
-            INNER JOIN events USING (event_id)
-            WHERE relates_to_id = ? AND {rel_type_sql}
+            SELECT thread_id, topological_ordering, stream_ordering
+            FROM threads
+            WHERE
+                room_id = ?
+                {pagination_clause}
+            ORDER BY topological_ordering DESC, stream_ordering DESC
+            LIMIT ?
         """
 
-        def _get_event_relations(
+        def _get_threads_txn(
             txn: LoggingTransaction,
-        ) -> Dict[str, Set[Tuple[str, str]]]:
-            txn.execute(sql, [event_id] + rel_type_args)
-            result: Dict[str, Set[Tuple[str, str]]] = {
-                rel_type: set() for rel_type in relation_types
-            }
-            for rel_type, sender, type in txn.fetchall():
-                result[rel_type].add((sender, type))
-            return result
+        ) -> Tuple[List[str], Optional[ThreadsNextBatch]]:
+            txn.execute(sql, (room_id, *pagination_args, limit + 1))
 
-        return await self.db_pool.runInteraction(
-            "get_event_relations", _get_event_relations
-        )
+            rows = cast(List[Tuple[str, int, int]], txn.fetchall())
+            thread_ids = [r[0] for r in rows]
+
+            # If there are more events, generate the next pagination key from the
+            # last thread which will be returned.
+            next_token = None
+            if len(thread_ids) > limit:
+                last_topo_id = rows[-2][1]
+                last_stream_id = rows[-2][2]
+                next_token = ThreadsNextBatch(last_topo_id, last_stream_id)
+
+            return thread_ids[:limit], next_token
+
+        return await self.db_pool.runInteraction("get_threads", _get_threads_txn)
 
     @cached()
-    async def get_thread_id(self, event_id: str) -> Optional[str]:
+    async def get_thread_id(self, event_id: str) -> str:
         """
         Get the thread ID for an event. This considers multi-level relations,
         e.g. an annotation to an event which is part of a thread.
 
+        It only searches up the relations tree, i.e. it only searches for events
+        which the given event is related to (and which those events are related
+        to, etc.)
+
+        Given the following DAG:
+
+            A <---[m.thread]-- B <--[m.annotation]-- C
+            ^
+            |--[m.reference]-- D <--[m.annotation]-- E
+
+        get_thread_id(X) considers events B and C as part of thread A.
+
+        See also get_thread_id_for_receipts.
+
         Args:
             event_id: The event ID to fetch the thread ID for.
 
         Returns:
             The event ID of the root event in the thread, if this event is part
-            of a thread. None, otherwise.
+            of a thread. "main", otherwise.
         """
-        # Since event relations form a tree, we should only ever find 0 or 1
-        # results from the below query.
+
+        # Recurse event relations up to the *root* event, then search that chain
+        # of relations for a thread relation. If one is found, the root event is
+        # returned.
+        #
+        # Note that this should only ever find 0 or 1 entries since it is invalid
+        # for an event to have a thread relation to an event which also has a
+        # relation.
         sql = """
             WITH RECURSIVE related_events AS (
-                SELECT event_id, relates_to_id, relation_type
+                SELECT event_id, relates_to_id, relation_type, 0 depth
                 FROM event_relations
                 WHERE event_id = ?
-                UNION SELECT e.event_id, e.relates_to_id, e.relation_type
+                UNION SELECT e.event_id, e.relates_to_id, e.relation_type, depth + 1
                 FROM event_relations e
                 INNER JOIN related_events r ON r.relates_to_id = e.event_id
-            ) SELECT relates_to_id FROM related_events WHERE relation_type = 'm.thread';
+                WHERE depth <= 3
+            )
+            SELECT relates_to_id FROM related_events
+            WHERE relation_type = 'm.thread'
+            ORDER BY depth DESC
+            LIMIT 1;
         """
 
-        def _get_thread_id(txn: LoggingTransaction) -> Optional[str]:
+        def _get_thread_id(txn: LoggingTransaction) -> str:
             txn.execute(sql, (event_id,))
-            # TODO Should we ensure there's only a single result here?
             row = txn.fetchone()
             if row:
                 return row[0]
-            return None
+
+            # If no thread was found, it is part of the main timeline.
+            return MAIN_TIMELINE
 
         return await self.db_pool.runInteraction("get_thread_id", _get_thread_id)
 
+    @cached()
+    async def get_thread_id_for_receipts(self, event_id: str) -> str:
+        """
+        Get the thread ID for an event by traversing to the top-most related event
+        and confirming any children events form a thread.
+
+        Given the following DAG:
+
+            A <---[m.thread]-- B <--[m.annotation]-- C
+            ^
+            |--[m.reference]-- D <--[m.annotation]-- E
+
+        get_thread_id_for_receipts(X) considers events A, B, C, D, and E as part
+        of thread A.
+
+        See also get_thread_id.
+
+        Args:
+            event_id: The event ID to fetch the thread ID for.
+
+        Returns:
+            The event ID of the root event in the thread, if this event is part
+            of a thread. "main", otherwise.
+        """
+
+        # Recurse event relations up to the *root* event, then search for any events
+        # related to that root node for a thread relation. If one is found, the
+        # root event is returned.
+        #
+        # Note that there cannot be thread relations in the middle of the chain since
+        # it is invalid for an event to have a thread relation to an event which also
+        # has a relation.
+        sql = """
+        SELECT relates_to_id FROM event_relations WHERE relates_to_id = COALESCE((
+            WITH RECURSIVE related_events AS (
+                SELECT event_id, relates_to_id, relation_type, 0 depth
+                FROM event_relations
+                WHERE event_id = ?
+                UNION SELECT e.event_id, e.relates_to_id, e.relation_type, depth + 1
+                FROM event_relations e
+                INNER JOIN related_events r ON r.relates_to_id = e.event_id
+                WHERE depth <= 3
+            )
+            SELECT relates_to_id FROM related_events
+            ORDER BY depth DESC
+            LIMIT 1
+        ), ?) AND relation_type = 'm.thread' LIMIT 1;
+        """
+
+        def _get_related_thread_id(txn: LoggingTransaction) -> str:
+            txn.execute(sql, (event_id, event_id))
+            row = txn.fetchone()
+            if row:
+                return row[0]
+
+            # If no thread was found, it is part of the main timeline.
+            return MAIN_TIMELINE
+
+        return await self.db_pool.runInteraction(
+            "get_related_thread_id", _get_related_thread_id
+        )
+
 
 class RelationsStore(RelationsWorkerStore):
     pass
diff --git a/synapse/storage/databases/main/room.py b/synapse/storage/databases/main/room.py
index e41c99027a..7d97f8f60e 100644
--- a/synapse/storage/databases/main/room.py
+++ b/synapse/storage/databases/main/room.py
@@ -97,6 +97,12 @@ class RoomSortOrder(Enum):
     STATE_EVENTS = "state_events"
 
 
+@attr.s(slots=True, frozen=True, auto_attribs=True)
+class PartialStateResyncInfo:
+    joined_via: Optional[str]
+    servers_in_room: List[str] = attr.ib(factory=list)
+
+
 class RoomWorkerStore(CacheInvalidationWorkerStore):
     def __init__(
         self,
@@ -1160,17 +1166,29 @@ class RoomWorkerStore(CacheInvalidationWorkerStore):
             desc="get_partial_state_servers_at_join",
         )
 
-    async def get_partial_state_rooms_and_servers(
+    async def get_partial_state_room_resync_info(
         self,
-    ) -> Mapping[str, Collection[str]]:
-        """Get all rooms containing events with partial state, and the servers known
-        to be in the room.
+    ) -> Mapping[str, PartialStateResyncInfo]:
+        """Get all rooms containing events with partial state, and the information
+        needed to restart a "resync" of those rooms.
 
         Returns:
             A dictionary of rooms with partial state, with room IDs as keys and
             lists of servers in rooms as values.
         """
-        room_servers: Dict[str, List[str]] = {}
+        room_servers: Dict[str, PartialStateResyncInfo] = {}
+
+        rows = await self.db_pool.simple_select_list(
+            table="partial_state_rooms",
+            keyvalues={},
+            retcols=("room_id", "joined_via"),
+            desc="get_server_which_served_partial_join",
+        )
+
+        for row in rows:
+            room_id = row["room_id"]
+            joined_via = row["joined_via"]
+            room_servers[room_id] = PartialStateResyncInfo(joined_via=joined_via)
 
         rows = await self.db_pool.simple_select_list(
             "partial_state_rooms_servers",
@@ -1182,7 +1200,15 @@ class RoomWorkerStore(CacheInvalidationWorkerStore):
         for row in rows:
             room_id = row["room_id"]
             server_name = row["server_name"]
-            room_servers.setdefault(room_id, []).append(server_name)
+            entry = room_servers.get(room_id)
+            if entry is None:
+                # There is a foreign key constraint which enforces that every room_id in
+                # partial_state_rooms_servers appears in partial_state_rooms. So we
+                # expect `entry` to be non-null. (This reasoning fails if we've
+                # partial-joined between the two SELECTs, but this is unlikely to happen
+                # in practice.)
+                continue
+            entry.servers_in_room.append(server_name)
 
         return room_servers
 
@@ -1827,6 +1853,7 @@ class RoomStore(RoomBackgroundUpdateStore, RoomWorkerStore):
         room_id: str,
         servers: Collection[str],
         device_lists_stream_id: int,
+        joined_via: str,
     ) -> None:
         """Mark the given room as containing events with partial state.
 
@@ -1842,6 +1869,7 @@ class RoomStore(RoomBackgroundUpdateStore, RoomWorkerStore):
             servers: other servers known to be in the room
             device_lists_stream_id: the device_lists stream ID at the time when we first
                 joined the room.
+            joined_via: the server name we requested a partial join from.
         """
         await self.db_pool.runInteraction(
             "store_partial_state_room",
@@ -1849,6 +1877,7 @@ class RoomStore(RoomBackgroundUpdateStore, RoomWorkerStore):
             room_id,
             servers,
             device_lists_stream_id,
+            joined_via,
         )
 
     def _store_partial_state_room_txn(
@@ -1857,6 +1886,7 @@ class RoomStore(RoomBackgroundUpdateStore, RoomWorkerStore):
         room_id: str,
         servers: Collection[str],
         device_lists_stream_id: int,
+        joined_via: str,
     ) -> None:
         DatabasePool.simple_insert_txn(
             txn,
@@ -1866,6 +1896,7 @@ class RoomStore(RoomBackgroundUpdateStore, RoomWorkerStore):
                 "device_lists_stream_id": device_lists_stream_id,
                 # To be updated later once the join event is persisted.
                 "join_event_id": None,
+                "joined_via": joined_via,
             },
         )
         DatabasePool.simple_insert_many_txn(
diff --git a/synapse/storage/databases/main/roommember.py b/synapse/storage/databases/main/roommember.py
index 2337289d88..32e1e983a5 100644
--- a/synapse/storage/databases/main/roommember.py
+++ b/synapse/storage/databases/main/roommember.py
@@ -666,7 +666,7 @@ class RoomMemberWorkerStore(EventsWorkerStore):
         cached_method_name="get_rooms_for_user",
         list_name="user_ids",
     )
-    async def get_rooms_for_users(
+    async def _get_rooms_for_users(
         self, user_ids: Collection[str]
     ) -> Dict[str, FrozenSet[str]]:
         """A batched version of `get_rooms_for_user`.
@@ -697,6 +697,21 @@ class RoomMemberWorkerStore(EventsWorkerStore):
 
         return {key: frozenset(rooms) for key, rooms in user_rooms.items()}
 
+    async def get_rooms_for_users(
+        self, user_ids: Collection[str]
+    ) -> Dict[str, FrozenSet[str]]:
+        """A batched wrapper around `_get_rooms_for_users`, to prevent locking
+        other calls to `get_rooms_for_user` for large user lists.
+        """
+        all_user_rooms: Dict[str, FrozenSet[str]] = {}
+
+        # 250 users is pretty arbitrary but the data can be quite large if users
+        # are in many rooms.
+        for batch_user_ids in batch_iter(user_ids, 250):
+            all_user_rooms.update(await self._get_rooms_for_users(batch_user_ids))
+
+        return all_user_rooms
+
     @cached(max_entries=10000)
     async def does_pair_of_users_share_a_room(
         self, user_id: str, other_user_id: str
diff --git a/synapse/storage/databases/main/stream.py b/synapse/storage/databases/main/stream.py
index 530f04e149..09ce855aa8 100644
--- a/synapse/storage/databases/main/stream.py
+++ b/synapse/storage/databases/main/stream.py
@@ -357,6 +357,24 @@ def filter_to_clause(event_filter: Optional[Filter]) -> Tuple[str, List[str]]:
         )
         args.extend(event_filter.related_by_rel_types)
 
+    if event_filter.rel_types:
+        clauses.append(
+            "(%s)"
+            % " OR ".join(
+                "event_relation.relation_type = ?" for _ in event_filter.rel_types
+            )
+        )
+        args.extend(event_filter.rel_types)
+
+    if event_filter.not_rel_types:
+        clauses.append(
+            "((%s) OR event_relation.relation_type IS NULL)"
+            % " AND ".join(
+                "event_relation.relation_type != ?" for _ in event_filter.not_rel_types
+            )
+        )
+        args.extend(event_filter.not_rel_types)
+
     return " AND ".join(clauses), args
 
 
@@ -1024,28 +1042,31 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
             "after": {"event_ids": events_after, "token": end_token},
         }
 
-    async def get_all_new_events_stream(
-        self, from_id: int, current_id: int, limit: int, get_prev_content: bool = False
-    ) -> Tuple[int, List[EventBase], Dict[str, Optional[int]]]:
+    async def get_all_new_event_ids_stream(
+        self,
+        from_id: int,
+        current_id: int,
+        limit: int,
+    ) -> Tuple[int, Dict[str, Optional[int]]]:
         """Get all new events
 
-        Returns all events with from_id < stream_ordering <= current_id.
+        Returns all event ids with from_id < stream_ordering <= current_id.
 
         Args:
             from_id:  the stream_ordering of the last event we processed
             current_id:  the stream_ordering of the most recently processed event
             limit: the maximum number of events to return
-            get_prev_content: whether to fetch previous event content
 
         Returns:
-            A tuple of (next_id, events, event_to_received_ts), where `next_id`
+            A tuple of (next_id, event_to_received_ts), where `next_id`
             is the next value to pass as `from_id` (it will either be the
             stream_ordering of the last returned event, or, if fewer than `limit`
             events were found, the `current_id`). The `event_to_received_ts` is
-            a dictionary mapping event ID to the event `received_ts`.
+            a dictionary mapping event ID to the event `received_ts`, sorted by ascending
+            stream_ordering.
         """
 
-        def get_all_new_events_stream_txn(
+        def get_all_new_event_ids_stream_txn(
             txn: LoggingTransaction,
         ) -> Tuple[int, Dict[str, Optional[int]]]:
             sql = (
@@ -1070,15 +1091,10 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
             return upper_bound, event_to_received_ts
 
         upper_bound, event_to_received_ts = await self.db_pool.runInteraction(
-            "get_all_new_events_stream", get_all_new_events_stream_txn
-        )
-
-        events = await self.get_events_as_list(
-            event_to_received_ts.keys(),
-            get_prev_content=get_prev_content,
+            "get_all_new_event_ids_stream", get_all_new_event_ids_stream_txn
         )
 
-        return upper_bound, events, event_to_received_ts
+        return upper_bound, event_to_received_ts
 
     async def get_federation_out_pos(self, typ: str) -> int:
         if self._need_to_reset_federation_stream_positions:
@@ -1202,8 +1218,6 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
             `to_token`), or `limit` is zero.
         """
 
-        assert int(limit) >= 0
-
         # Tokens really represent positions between elements, but we use
         # the convention of pointing to the event before the gap. Hence
         # we have a bit of asymmetry when it comes to equalities.
@@ -1282,8 +1296,8 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
                 # Multiple labels could cause the same event to appear multiple times.
                 needs_distinct = True
 
-        # If there is a filter on relation_senders and relation_types join to the
-        # relations table.
+        # If there is a relation_senders and relation_types filter join to the
+        # relations table to get events related to the current event.
         if event_filter and (
             event_filter.related_by_senders or event_filter.related_by_rel_types
         ):
@@ -1298,6 +1312,13 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
                     LEFT JOIN events AS related_event ON (relation.event_id = related_event.event_id)
                 """
 
+        # If there is a not_rel_types filter join to the relations table to get
+        # the event's relation information.
+        if event_filter and (event_filter.rel_types or event_filter.not_rel_types):
+            join_clause += """
+                LEFT JOIN event_relations AS event_relation USING (event_id)
+            """
+
         if needs_distinct:
             select_keywords += " DISTINCT"
 
diff --git a/synapse/storage/schema/main/delta/73/06thread_notifications_backfill.sql b/synapse/storage/schema/main/delta/73/06thread_notifications_backfill.sql
deleted file mode 100644
index 0ffde9bbeb..0000000000
--- a/synapse/storage/schema/main/delta/73/06thread_notifications_backfill.sql
+++ /dev/null
@@ -1,29 +0,0 @@
-/* Copyright 2022 The Matrix.org Foundation C.I.C
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *    http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
--- Forces the background updates from 06thread_notifications.sql to run in the
--- foreground as code will now require those to be "done".
-
-DELETE FROM background_updates WHERE update_name = 'event_push_backfill_thread_id';
-
--- Overwrite any null thread_id columns.
-UPDATE event_push_actions_staging SET thread_id = 'main' WHERE thread_id IS NULL;
-UPDATE event_push_actions SET thread_id = 'main' WHERE thread_id IS NULL;
-UPDATE event_push_summary SET thread_id = 'main' WHERE thread_id IS NULL;
-
--- Do not run the event_push_summary_unique_index job if it is pending; the
--- thread_id field will be made required.
-DELETE FROM background_updates WHERE update_name = 'event_push_summary_unique_index';
-DROP INDEX IF EXISTS event_push_summary_unique_index;
diff --git a/synapse/storage/schema/main/delta/73/06thread_notifications_thread_id_idx.sql b/synapse/storage/schema/main/delta/73/06thread_notifications_thread_id_idx.sql
new file mode 100644
index 0000000000..8b3c636594
--- /dev/null
+++ b/synapse/storage/schema/main/delta/73/06thread_notifications_thread_id_idx.sql
@@ -0,0 +1,23 @@
+/* Copyright 2022 The Matrix.org Foundation C.I.C
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+-- Allow there to be multiple summaries per user/room.
+DROP INDEX IF EXISTS event_push_summary_unique_index;
+
+INSERT INTO background_updates (ordering, update_name, progress_json, depends_on) VALUES
+  (7306, 'event_push_actions_thread_id_null', '{}', 'event_push_backfill_thread_id');
+
+INSERT INTO background_updates (ordering, update_name, progress_json, depends_on) VALUES
+  (7306, 'event_push_summary_thread_id_null', '{}', 'event_push_backfill_thread_id');
diff --git a/synapse/storage/schema/main/delta/73/07thread_notifications_not_null.sql.sqlite b/synapse/storage/schema/main/delta/73/07thread_notifications_not_null.sql.sqlite
deleted file mode 100644
index 5322ad77a4..0000000000
--- a/synapse/storage/schema/main/delta/73/07thread_notifications_not_null.sql.sqlite
+++ /dev/null
@@ -1,101 +0,0 @@
-/* Copyright 2022 The Matrix.org Foundation C.I.C
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *    http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
--- SQLite doesn't support modifying columns to an existing table, so it must
--- be recreated.
-
--- Create the new tables.
-CREATE TABLE event_push_actions_staging_new (
-    event_id TEXT NOT NULL,
-    user_id TEXT NOT NULL,
-    actions TEXT NOT NULL,
-    notif SMALLINT NOT NULL,
-    highlight SMALLINT NOT NULL,
-    unread SMALLINT,
-    thread_id TEXT NOT NULL,
-    inserted_ts BIGINT
-);
-
-CREATE TABLE event_push_actions_new (
-    room_id TEXT NOT NULL,
-    event_id TEXT NOT NULL,
-    user_id TEXT NOT NULL,
-    profile_tag VARCHAR(32),
-    actions TEXT NOT NULL,
-    topological_ordering BIGINT,
-    stream_ordering BIGINT,
-    notif SMALLINT,
-    highlight SMALLINT,
-    unread SMALLINT,
-    thread_id TEXT NOT NULL,
-    CONSTRAINT event_id_user_id_profile_tag_uniqueness UNIQUE (room_id, event_id, user_id, profile_tag)
-);
-
-CREATE TABLE event_push_summary_new (
-    user_id TEXT NOT NULL,
-    room_id TEXT NOT NULL,
-    notif_count BIGINT NOT NULL,
-    stream_ordering BIGINT NOT NULL,
-    unread_count BIGINT,
-    last_receipt_stream_ordering BIGINT,
-    thread_id TEXT NOT NULL
-);
-
--- Swap the indexes.
-DROP INDEX IF EXISTS event_push_actions_staging_id;
-CREATE INDEX event_push_actions_staging_id ON event_push_actions_staging_new(event_id);
-
-DROP INDEX IF EXISTS event_push_actions_room_id_user_id;
-DROP INDEX IF EXISTS event_push_actions_rm_tokens;
-DROP INDEX IF EXISTS event_push_actions_stream_ordering;
-DROP INDEX IF EXISTS event_push_actions_u_highlight;
-DROP INDEX IF EXISTS event_push_actions_highlights_index;
-CREATE INDEX event_push_actions_room_id_user_id on event_push_actions_new(room_id, user_id);
-CREATE INDEX event_push_actions_rm_tokens on event_push_actions_new( user_id, room_id, topological_ordering, stream_ordering );
-CREATE INDEX event_push_actions_stream_ordering on event_push_actions_new( stream_ordering, user_id );
-CREATE INDEX event_push_actions_u_highlight ON event_push_actions_new (user_id, stream_ordering);
-CREATE INDEX event_push_actions_highlights_index ON event_push_actions_new (user_id, room_id, topological_ordering, stream_ordering);
-
--- Copy the data.
-INSERT INTO event_push_actions_staging_new (event_id, user_id, actions, notif, highlight, unread, thread_id, inserted_ts)
-    SELECT event_id, user_id, actions, notif, highlight, unread, thread_id, inserted_ts
-    FROM event_push_actions_staging;
-
-INSERT INTO event_push_actions_new (room_id, event_id, user_id, profile_tag, actions, topological_ordering, stream_ordering, notif, highlight, unread, thread_id)
-    SELECT room_id, event_id, user_id, profile_tag, actions, topological_ordering, stream_ordering, notif, highlight, unread, thread_id
-    FROM event_push_actions;
-
-INSERT INTO event_push_summary_new (user_id, room_id, notif_count, stream_ordering, unread_count, last_receipt_stream_ordering, thread_id)
-    SELECT user_id, room_id, notif_count, stream_ordering, unread_count, last_receipt_stream_ordering, thread_id
-    FROM event_push_summary;
-
--- Drop the old tables.
-DROP TABLE event_push_actions_staging;
-DROP TABLE event_push_actions;
-DROP TABLE event_push_summary;
-
--- Rename the tables.
-ALTER TABLE event_push_actions_staging_new RENAME TO event_push_actions_staging;
-ALTER TABLE event_push_actions_new RENAME TO event_push_actions;
-ALTER TABLE event_push_summary_new RENAME TO event_push_summary;
-
--- Re-run background updates from 72/02event_push_actions_index.sql and
--- 72/06thread_notifications.sql.
-INSERT INTO background_updates (ordering, update_name, progress_json) VALUES
-  (7307, 'event_push_summary_unique_index2', '{}')
-  ON CONFLICT (update_name) DO NOTHING;
-INSERT INTO background_updates (ordering, update_name, progress_json) VALUES
-  (7307, 'event_push_actions_stream_highlight_index', '{}')
-  ON CONFLICT (update_name) DO NOTHING;
diff --git a/synapse/storage/schema/main/delta/73/07thread_notifications_not_null.sql.postgres b/synapse/storage/schema/main/delta/73/09partial_joined_via_destination.sql
index 33674f8c62..066d602b18 100644
--- a/synapse/storage/schema/main/delta/73/07thread_notifications_not_null.sql.postgres
+++ b/synapse/storage/schema/main/delta/73/09partial_joined_via_destination.sql
@@ -13,7 +13,6 @@
  * limitations under the License.
  */
 
--- The columns can now be made non-nullable.
-ALTER TABLE event_push_actions_staging ALTER COLUMN thread_id SET NOT NULL;
-ALTER TABLE event_push_actions ALTER COLUMN thread_id SET NOT NULL;
-ALTER TABLE event_push_summary ALTER COLUMN thread_id SET NOT NULL;
+-- When we resync partial state, we prioritise doing so using the server we
+-- partial-joined from. To do this we need to record which server that was!
+ALTER TABLE partial_state_rooms ADD COLUMN joined_via TEXT;
diff --git a/synapse/storage/schema/main/delta/73/09threads_table.sql b/synapse/storage/schema/main/delta/73/09threads_table.sql
new file mode 100644
index 0000000000..aa7c5e9a2e
--- /dev/null
+++ b/synapse/storage/schema/main/delta/73/09threads_table.sql
@@ -0,0 +1,30 @@
+/* Copyright 2022 The Matrix.org Foundation C.I.C
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+CREATE TABLE threads (
+    room_id TEXT NOT NULL,
+    -- The event ID of the root event in the thread.
+    thread_id TEXT NOT NULL,
+    -- The latest event ID and corresponding topo / stream ordering.
+    latest_event_id TEXT NOT NULL,
+    topological_ordering BIGINT NOT NULL,
+    stream_ordering BIGINT NOT NULL,
+    CONSTRAINT threads_uniqueness UNIQUE (room_id, thread_id)
+);
+
+CREATE INDEX threads_ordering_idx ON threads(room_id, topological_ordering, stream_ordering);
+
+INSERT INTO background_updates (ordering, update_name, progress_json) VALUES
+  (7309, 'threads_backfill', '{}');
diff --git a/synapse/streams/__init__.py b/synapse/streams/__init__.py
index 806b671305..2dcd43d0a2 100644
--- a/synapse/streams/__init__.py
+++ b/synapse/streams/__init__.py
@@ -27,7 +27,7 @@ class EventSource(Generic[K, R]):
         self,
         user: UserID,
         from_key: K,
-        limit: Optional[int],
+        limit: int,
         room_ids: Collection[str],
         is_guest: bool,
         explicit_room_id: Optional[str] = None,
diff --git a/synapse/streams/config.py b/synapse/streams/config.py
index f6f7bf3d8b..6df2de919c 100644
--- a/synapse/streams/config.py
+++ b/synapse/streams/config.py
@@ -35,14 +35,14 @@ class PaginationConfig:
     from_token: Optional[StreamToken]
     to_token: Optional[StreamToken]
     direction: str
-    limit: Optional[int]
+    limit: int
 
     @classmethod
     async def from_request(
         cls,
         store: "DataStore",
         request: SynapseRequest,
-        default_limit: Optional[int] = None,
+        default_limit: int,
         default_dir: str = "f",
     ) -> "PaginationConfig":
         direction = parse_string(
@@ -69,12 +69,10 @@ class PaginationConfig:
             raise SynapseError(400, "'to' parameter is invalid")
 
         limit = parse_integer(request, "limit", default=default_limit)
+        if limit < 0:
+            raise SynapseError(400, "Limit must be 0 or above")
 
-        if limit:
-            if limit < 0:
-                raise SynapseError(400, "Limit must be 0 or above")
-
-            limit = min(int(limit), MAX_LIMIT)
+        limit = min(limit, MAX_LIMIT)
 
         try:
             return PaginationConfig(from_tok, to_tok, direction, limit)
diff --git a/synapse/util/caches/deferred_cache.py b/synapse/util/caches/deferred_cache.py
index 6425f851ea..bcb1cba362 100644
--- a/synapse/util/caches/deferred_cache.py
+++ b/synapse/util/caches/deferred_cache.py
@@ -395,8 +395,8 @@ class DeferredCache(Generic[KT, VT]):
             # _pending_deferred_cache.pop should either return a CacheEntry, or, in the
             # case of a TreeCache, a dict of keys to cache entries. Either way calling
             # iterate_tree_cache_entry on it will do the right thing.
-            for entry in iterate_tree_cache_entry(entry):
-                for cb in entry.get_invalidation_callbacks(key):
+            for iter_entry in iterate_tree_cache_entry(entry):
+                for cb in iter_entry.get_invalidation_callbacks(key):
                     cb()
 
     def invalidate_all(self) -> None:
diff --git a/synapse/util/caches/descriptors.py b/synapse/util/caches/descriptors.py
index 0391966462..b3c748ef44 100644
--- a/synapse/util/caches/descriptors.py
+++ b/synapse/util/caches/descriptors.py
@@ -432,7 +432,7 @@ class DeferredCacheListDescriptor(_CacheDescriptorBase):
         num_args = cached_method.num_args
 
         if num_args != self.num_args:
-            raise Exception(
+            raise TypeError(
                 "Number of args (%s) does not match underlying cache_method_name=%s (%s)."
                 % (self.num_args, self.cached_method_name, num_args)
             )
diff --git a/synapse/util/stringutils.py b/synapse/util/stringutils.py
index 27a363d7e5..4961fe9313 100644
--- a/synapse/util/stringutils.py
+++ b/synapse/util/stringutils.py
@@ -86,7 +86,7 @@ def parse_server_name(server_name: str) -> Tuple[str, Optional[int]]:
         ValueError if the server name could not be parsed.
     """
     try:
-        if server_name[-1] == "]":
+        if server_name and server_name[-1] == "]":
             # ipv6 literal, hopefully
             return server_name, None
 
@@ -123,7 +123,7 @@ def parse_and_validate_server_name(server_name: str) -> Tuple[str, Optional[int]
     # that nobody is sneaking IP literals in that look like hostnames, etc.
 
     # look for ipv6 literals
-    if host[0] == "[":
+    if host and host[0] == "[":
         if host[-1] != "]":
             raise ValueError("Mismatched [...] in server name '%s'" % (server_name,))
 
diff --git a/synapse/visibility.py b/synapse/visibility.py
index c4048d2477..40a9c5b53f 100644
--- a/synapse/visibility.py
+++ b/synapse/visibility.py
@@ -84,7 +84,15 @@ async def filter_events_for_client(
     """
     # Filter out events that have been soft failed so that we don't relay them
     # to clients.
+    events_before_filtering = events
     events = [e for e in events if not e.internal_metadata.is_soft_failed()]
+    if len(events_before_filtering) != len(events):
+        if logger.isEnabledFor(logging.DEBUG):
+            logger.debug(
+                "filter_events_for_client: Filtered out soft-failed events: Before=%s, After=%s",
+                [event.event_id for event in events_before_filtering],
+                [event.event_id for event in events],
+            )
 
     types = (_HISTORY_VIS_KEY, (EventTypes.Member, user_id))
 
@@ -301,6 +309,10 @@ def _check_client_allowed_to_see_event(
             _check_filter_send_to_client(event, clock, retention_policy, sender_ignored)
             == _CheckFilter.DENIED
         ):
+            logger.debug(
+                "_check_client_allowed_to_see_event(event=%s): Filtered out event because `_check_filter_send_to_client` returned `_CheckFilter.DENIED`",
+                event.event_id,
+            )
             return None
 
     if event.event_id in always_include_ids:
@@ -312,9 +324,17 @@ def _check_client_allowed_to_see_event(
         # for out-of-band membership events (eg, incoming invites, or rejections of
         # said invite) for the user themselves.
         if event.type == EventTypes.Member and event.state_key == user_id:
-            logger.debug("Returning out-of-band-membership event %s", event)
+            logger.debug(
+                "_check_client_allowed_to_see_event(event=%s): Returning out-of-band-membership event %s",
+                event.event_id,
+                event,
+            )
             return event
 
+        logger.debug(
+            "_check_client_allowed_to_see_event(event=%s): Filtered out event because it's an outlier",
+            event.event_id,
+        )
         return None
 
     if state is None:
@@ -337,11 +357,21 @@ def _check_client_allowed_to_see_event(
 
     membership_result = _check_membership(user_id, event, visibility, state, is_peeking)
     if not membership_result.allowed:
+        logger.debug(
+            "_check_client_allowed_to_see_event(event=%s): Filtered out event because the user can't see the event because of their membership, membership_result.allowed=%s membership_result.joined=%s",
+            event.event_id,
+            membership_result.allowed,
+            membership_result.joined,
+        )
         return None
 
     # If the sender has been erased and the user was not joined at the time, we
     # must only return the redacted form.
     if sender_erased and not membership_result.joined:
+        logger.debug(
+            "_check_client_allowed_to_see_event(event=%s): Returning pruned event because `sender_erased` and the user was not joined at the time",
+            event.event_id,
+        )
         event = prune_event(event)
 
     return event
diff --git a/tests/api/test_filtering.py b/tests/api/test_filtering.py
index a269c477fb..a82c4eed86 100644
--- a/tests/api/test_filtering.py
+++ b/tests/api/test_filtering.py
@@ -35,6 +35,8 @@ def MockEvent(**kwargs):
         kwargs["event_id"] = "fake_event_id"
     if "type" not in kwargs:
         kwargs["type"] = "fake_type"
+    if "content" not in kwargs:
+        kwargs["content"] = {}
     return make_event_from_dict(kwargs)
 
 
@@ -357,6 +359,66 @@ class FilteringTestCase(unittest.HomeserverTestCase):
 
         self.assertTrue(Filter(self.hs, definition)._check(event))
 
+    @unittest.override_config({"experimental_features": {"msc3874_enabled": True}})
+    def test_filter_rel_type(self):
+        definition = {"org.matrix.msc3874.rel_types": ["m.thread"]}
+        event = MockEvent(
+            sender="@foo:bar",
+            type="m.room.message",
+            room_id="!secretbase:unknown",
+            content={},
+        )
+
+        self.assertFalse(Filter(self.hs, definition)._check(event))
+
+        event = MockEvent(
+            sender="@foo:bar",
+            type="m.room.message",
+            room_id="!secretbase:unknown",
+            content={"m.relates_to": {"event_id": "$abc", "rel_type": "m.reference"}},
+        )
+
+        self.assertFalse(Filter(self.hs, definition)._check(event))
+
+        event = MockEvent(
+            sender="@foo:bar",
+            type="m.room.message",
+            room_id="!secretbase:unknown",
+            content={"m.relates_to": {"event_id": "$abc", "rel_type": "m.thread"}},
+        )
+
+        self.assertTrue(Filter(self.hs, definition)._check(event))
+
+    @unittest.override_config({"experimental_features": {"msc3874_enabled": True}})
+    def test_filter_not_rel_type(self):
+        definition = {"org.matrix.msc3874.not_rel_types": ["m.thread"]}
+        event = MockEvent(
+            sender="@foo:bar",
+            type="m.room.message",
+            room_id="!secretbase:unknown",
+            content={"m.relates_to": {"event_id": "$abc", "rel_type": "m.thread"}},
+        )
+
+        self.assertFalse(Filter(self.hs, definition)._check(event))
+
+        event = MockEvent(
+            sender="@foo:bar",
+            type="m.room.message",
+            room_id="!secretbase:unknown",
+            content={},
+        )
+
+        self.assertTrue(Filter(self.hs, definition)._check(event))
+
+        event = MockEvent(
+            sender="@foo:bar",
+            type="m.room.message",
+            room_id="!secretbase:unknown",
+            content={"m.relates_to": {"event_id": "$abc", "rel_type": "m.reference"}},
+        )
+
+        self.assertTrue(Filter(self.hs, definition)._check(event))
+
     def test_filter_presence_match(self):
         user_filter_json = {"presence": {"types": ["m.*"]}}
         filter_id = self.get_success(
@@ -456,7 +518,6 @@ class FilteringTestCase(unittest.HomeserverTestCase):
 
         self.assertEqual(filtered_room_ids, ["!allowed:example.com"])
 
-    @unittest.override_config({"experimental_features": {"msc3440_enabled": True}})
     def test_filter_relations(self):
         events = [
             # An event without a relation.
diff --git a/tests/app/test_openid_listener.py b/tests/app/test_openid_listener.py
index c7dae58eb5..8d03da7f96 100644
--- a/tests/app/test_openid_listener.py
+++ b/tests/app/test_openid_listener.py
@@ -79,7 +79,7 @@ class FederationReaderOpenIDListenerTests(HomeserverTestCase):
         self.assertEqual(channel.code, 401)
 
 
-@patch("synapse.app.homeserver.KeyApiV2Resource", new=Mock())
+@patch("synapse.app.homeserver.KeyResource", new=Mock())
 class SynapseHomeserverOpenIDListenerTests(HomeserverTestCase):
     def make_homeserver(self, reactor, clock):
         hs = self.setup_test_homeserver(
diff --git a/tests/federation/transport/test_client.py b/tests/federation/transport/test_client.py
index 0926e0583d..dd4d1b56de 100644
--- a/tests/federation/transport/test_client.py
+++ b/tests/federation/transport/test_client.py
@@ -17,6 +17,7 @@ from unittest.mock import Mock
 
 from synapse.api.room_versions import RoomVersions
 from synapse.federation.transport.client import SendJoinParser
+from synapse.util import ExceptionBundle
 
 from tests.unittest import TestCase
 
@@ -121,10 +122,8 @@ class SendJoinParserTestCase(TestCase):
         # Send half of the data to the parser
         parser.write(serialisation[: len(serialisation) // 2])
 
-        # Close the parser. There should be _some_ kind of exception, but it need not
-        # be that RuntimeError directly. E.g. we might want to raise a wrapper
-        # encompassing multiple errors from multiple coroutines.
-        with self.assertRaises(Exception):
+        # Close the parser. There should be _some_ kind of exception.
+        with self.assertRaises(ExceptionBundle):
             parser.finish()
 
         # In any case, we should have tried to close both coros.
diff --git a/tests/handlers/test_appservice.py b/tests/handlers/test_appservice.py
index af24c4984d..7e4570f990 100644
--- a/tests/handlers/test_appservice.py
+++ b/tests/handlers/test_appservice.py
@@ -76,9 +76,13 @@ class AppServiceHandlerTestCase(unittest.TestCase):
         event = Mock(
             sender="@someone:anywhere", type="m.room.message", room_id="!foo:bar"
         )
-        self.mock_store.get_all_new_events_stream.side_effect = [
-            make_awaitable((0, [], {})),
-            make_awaitable((1, [event], {event.event_id: 0})),
+        self.mock_store.get_all_new_event_ids_stream.side_effect = [
+            make_awaitable((0, {})),
+            make_awaitable((1, {event.event_id: 0})),
+        ]
+        self.mock_store.get_events_as_list.side_effect = [
+            make_awaitable([]),
+            make_awaitable([event]),
         ]
         self.handler.notify_interested_services(RoomStreamToken(None, 1))
 
@@ -95,10 +99,10 @@ class AppServiceHandlerTestCase(unittest.TestCase):
 
         event = Mock(sender=user_id, type="m.room.message", room_id="!foo:bar")
         self.mock_as_api.query_user.return_value = make_awaitable(True)
-        self.mock_store.get_all_new_events_stream.side_effect = [
-            make_awaitable((0, [event], {event.event_id: 0})),
+        self.mock_store.get_all_new_event_ids_stream.side_effect = [
+            make_awaitable((0, {event.event_id: 0})),
         ]
-
+        self.mock_store.get_events_as_list.side_effect = [make_awaitable([event])]
         self.handler.notify_interested_services(RoomStreamToken(None, 0))
 
         self.mock_as_api.query_user.assert_called_once_with(services[0], user_id)
@@ -112,7 +116,7 @@ class AppServiceHandlerTestCase(unittest.TestCase):
 
         event = Mock(sender=user_id, type="m.room.message", room_id="!foo:bar")
         self.mock_as_api.query_user.return_value = make_awaitable(True)
-        self.mock_store.get_all_new_events_stream.side_effect = [
+        self.mock_store.get_all_new_event_ids_stream.side_effect = [
             make_awaitable((0, [event], {event.event_id: 0})),
         ]
 
diff --git a/tests/handlers/test_federation.py b/tests/handlers/test_federation.py
index 745750b1d7..d00c69c229 100644
--- a/tests/handlers/test_federation.py
+++ b/tests/handlers/test_federation.py
@@ -19,7 +19,13 @@ from unittest.mock import Mock, patch
 from twisted.test.proto_helpers import MemoryReactor
 
 from synapse.api.constants import EventTypes
-from synapse.api.errors import AuthError, Codes, LimitExceededError, SynapseError
+from synapse.api.errors import (
+    AuthError,
+    Codes,
+    LimitExceededError,
+    NotFoundError,
+    SynapseError,
+)
 from synapse.api.room_versions import RoomVersions
 from synapse.events import EventBase, make_event_from_dict
 from synapse.federation.federation_base import event_from_pdu_json
@@ -28,6 +34,7 @@ from synapse.logging.context import LoggingContext, run_in_background
 from synapse.rest import admin
 from synapse.rest.client import login, room
 from synapse.server import HomeServer
+from synapse.storage.databases.main.events_worker import EventCacheEntry
 from synapse.util import Clock
 from synapse.util.stringutils import random_string
 
@@ -322,6 +329,102 @@ class FederationTestCase(unittest.FederatingHomeserverTestCase):
             )
         self.get_success(d)
 
+    def test_backfill_ignores_known_events(self) -> None:
+        """
+        Tests that events that we already know about are ignored when backfilling.
+        """
+        # Set up users
+        user_id = self.register_user("kermit", "test")
+        tok = self.login("kermit", "test")
+
+        other_server = "otherserver"
+        other_user = "@otheruser:" + other_server
+
+        # Create a room to backfill events into
+        room_id = self.helper.create_room_as(room_creator=user_id, tok=tok)
+        room_version = self.get_success(self.store.get_room_version(room_id))
+
+        # Build an event to backfill
+        event = event_from_pdu_json(
+            {
+                "type": EventTypes.Message,
+                "content": {"body": "hello world", "msgtype": "m.text"},
+                "room_id": room_id,
+                "sender": other_user,
+                "depth": 32,
+                "prev_events": [],
+                "auth_events": [],
+                "origin_server_ts": self.clock.time_msec(),
+            },
+            room_version,
+        )
+
+        # Ensure the event is not already in the DB
+        self.get_failure(
+            self.store.get_event(event.event_id),
+            NotFoundError,
+        )
+
+        # Backfill the event and check that it has entered the DB.
+
+        # We mock out the FederationClient.backfill method, to pretend that a remote
+        # server has returned our fake event.
+        federation_client_backfill_mock = Mock(return_value=make_awaitable([event]))
+        self.hs.get_federation_client().backfill = federation_client_backfill_mock
+
+        # We also mock the persist method with a side effect of itself. This allows us
+        # to track when it has been called while preserving its function.
+        persist_events_and_notify_mock = Mock(
+            side_effect=self.hs.get_federation_event_handler().persist_events_and_notify
+        )
+        self.hs.get_federation_event_handler().persist_events_and_notify = (
+            persist_events_and_notify_mock
+        )
+
+        # Small side-tangent. We populate the event cache with the event, even though
+        # it is not yet in the DB. This is an invalid scenario that can currently occur
+        # due to not properly invalidating the event cache.
+        # See https://github.com/matrix-org/synapse/issues/13476.
+        #
+        # As a result, backfill should not rely on the event cache to check whether
+        # we already have an event in the DB.
+        # TODO: Remove this bit when the event cache is properly invalidated.
+        cache_entry = EventCacheEntry(
+            event=event,
+            redacted_event=None,
+        )
+        self.store._get_event_cache.set_local((event.event_id,), cache_entry)
+
+        # We now call FederationEventHandler.backfill (a separate method) to trigger
+        # a backfill request. It should receive the fake event.
+        self.get_success(
+            self.hs.get_federation_event_handler().backfill(
+                other_user,
+                room_id,
+                limit=10,
+                extremities=[],
+            )
+        )
+
+        # Check that our fake event was persisted.
+        persist_events_and_notify_mock.assert_called_once()
+        persist_events_and_notify_mock.reset_mock()
+
+        # Now we repeat the backfill, having the homeserver receive the fake event
+        # again.
+        self.get_success(
+            self.hs.get_federation_event_handler().backfill(
+                other_user,
+                room_id,
+                limit=10,
+                extremities=[],
+            ),
+        )
+
+        # This time, we expect no event persistence to have occurred, as we already
+        # have this event.
+        persist_events_and_notify_mock.assert_not_called()
+
     @unittest.override_config(
         {"rc_invites": {"per_user": {"per_second": 0.5, "burst_count": 3}}}
     )
diff --git a/tests/handlers/test_federation_event.py b/tests/handlers/test_federation_event.py
index 918010cddb..e448cb1901 100644
--- a/tests/handlers/test_federation_event.py
+++ b/tests/handlers/test_federation_event.py
@@ -14,7 +14,7 @@
 from typing import Optional
 from unittest import mock
 
-from synapse.api.errors import AuthError
+from synapse.api.errors import AuthError, StoreError
 from synapse.api.room_versions import RoomVersion
 from synapse.event_auth import (
     check_state_dependent_auth_rules,
@@ -43,7 +43,7 @@ class FederationEventHandlerTests(unittest.FederatingHomeserverTestCase):
     def make_homeserver(self, reactor, clock):
         # mock out the federation transport client
         self.mock_federation_transport_client = mock.Mock(
-            spec=["get_room_state_ids", "get_room_state", "get_event"]
+            spec=["get_room_state_ids", "get_room_state", "get_event", "backfill"]
         )
         return super().setup_test_homeserver(
             federation_transport_client=self.mock_federation_transport_client
@@ -459,6 +459,203 @@ class FederationEventHandlerTests(unittest.FederatingHomeserverTestCase):
         )
         self.assertIsNotNone(persisted, "pulled event was not persisted at all")
 
+    def test_backfill_signature_failure_does_not_fetch_same_prev_event_later(
+        self,
+    ) -> None:
+        """
+        Test to make sure we backoff and don't try to fetch a missing prev_event when we
+        already know it has a invalid signature from checking the signatures of all of
+        the events in the backfill response.
+        """
+        OTHER_USER = f"@user:{self.OTHER_SERVER_NAME}"
+        main_store = self.hs.get_datastores().main
+
+        # Create the room
+        user_id = self.register_user("kermit", "test")
+        tok = self.login("kermit", "test")
+        room_id = self.helper.create_room_as(room_creator=user_id, tok=tok)
+        room_version = self.get_success(main_store.get_room_version(room_id))
+
+        # Allow the remote user to send state events
+        self.helper.send_state(
+            room_id,
+            "m.room.power_levels",
+            {"events_default": 0, "state_default": 0},
+            tok=tok,
+        )
+
+        # Add the remote user to the room
+        member_event = self.get_success(
+            event_injection.inject_member_event(self.hs, room_id, OTHER_USER, "join")
+        )
+
+        initial_state_map = self.get_success(
+            main_store.get_partial_current_state_ids(room_id)
+        )
+
+        auth_event_ids = [
+            initial_state_map[("m.room.create", "")],
+            initial_state_map[("m.room.power_levels", "")],
+            member_event.event_id,
+        ]
+
+        # We purposely don't run `add_hashes_and_signatures_from_other_server`
+        # over this because we want the signature check to fail.
+        pulled_event_without_signatures = make_event_from_dict(
+            {
+                "type": "test_regular_type",
+                "room_id": room_id,
+                "sender": OTHER_USER,
+                "prev_events": [member_event.event_id],
+                "auth_events": auth_event_ids,
+                "origin_server_ts": 1,
+                "depth": 12,
+                "content": {"body": "pulled_event_without_signatures"},
+            },
+            room_version,
+        )
+
+        # Create a regular event that should pass except for the
+        # `pulled_event_without_signatures` in the `prev_event`.
+        pulled_event = make_event_from_dict(
+            self.add_hashes_and_signatures_from_other_server(
+                {
+                    "type": "test_regular_type",
+                    "room_id": room_id,
+                    "sender": OTHER_USER,
+                    "prev_events": [
+                        member_event.event_id,
+                        pulled_event_without_signatures.event_id,
+                    ],
+                    "auth_events": auth_event_ids,
+                    "origin_server_ts": 1,
+                    "depth": 12,
+                    "content": {"body": "pulled_event"},
+                }
+            ),
+            room_version,
+        )
+
+        # We expect an outbound request to /backfill, so stub that out
+        self.mock_federation_transport_client.backfill.return_value = make_awaitable(
+            {
+                "origin": self.OTHER_SERVER_NAME,
+                "origin_server_ts": 123,
+                "pdus": [
+                    # This is one of the important aspects of this test: we include
+                    # `pulled_event_without_signatures` so it fails the signature check
+                    # when we filter down the backfill response down to events which
+                    # have valid signatures in
+                    # `_check_sigs_and_hash_for_pulled_events_and_fetch`
+                    pulled_event_without_signatures.get_pdu_json(),
+                    # Then later when we process this valid signature event, when we
+                    # fetch the missing `prev_event`s, we want to make sure that we
+                    # backoff and don't try and fetch `pulled_event_without_signatures`
+                    # again since we know it just had an invalid signature.
+                    pulled_event.get_pdu_json(),
+                ],
+            }
+        )
+
+        # Keep track of the count and make sure we don't make any of these requests
+        event_endpoint_requested_count = 0
+        room_state_ids_endpoint_requested_count = 0
+        room_state_endpoint_requested_count = 0
+
+        async def get_event(
+            destination: str, event_id: str, timeout: Optional[int] = None
+        ) -> None:
+            nonlocal event_endpoint_requested_count
+            event_endpoint_requested_count += 1
+
+        async def get_room_state_ids(
+            destination: str, room_id: str, event_id: str
+        ) -> None:
+            nonlocal room_state_ids_endpoint_requested_count
+            room_state_ids_endpoint_requested_count += 1
+
+        async def get_room_state(
+            room_version: RoomVersion, destination: str, room_id: str, event_id: str
+        ) -> None:
+            nonlocal room_state_endpoint_requested_count
+            room_state_endpoint_requested_count += 1
+
+        # We don't expect an outbound request to `/event`, `/state_ids`, or `/state` in
+        # the happy path but if the logic is sneaking around what we expect, stub that
+        # out so we can detect that failure
+        self.mock_federation_transport_client.get_event.side_effect = get_event
+        self.mock_federation_transport_client.get_room_state_ids.side_effect = (
+            get_room_state_ids
+        )
+        self.mock_federation_transport_client.get_room_state.side_effect = (
+            get_room_state
+        )
+
+        # The function under test: try to backfill and process the pulled event
+        with LoggingContext("test"):
+            self.get_success(
+                self.hs.get_federation_event_handler().backfill(
+                    self.OTHER_SERVER_NAME,
+                    room_id,
+                    limit=1,
+                    extremities=["$some_extremity"],
+                )
+            )
+
+        if event_endpoint_requested_count > 0:
+            self.fail(
+                "We don't expect an outbound request to /event in the happy path but if "
+                "the logic is sneaking around what we expect, make sure to fail the test. "
+                "We don't expect it because the signature failure should cause us to backoff "
+                "and not asking about pulled_event_without_signatures="
+                f"{pulled_event_without_signatures.event_id} again"
+            )
+
+        if room_state_ids_endpoint_requested_count > 0:
+            self.fail(
+                "We don't expect an outbound request to /state_ids in the happy path but if "
+                "the logic is sneaking around what we expect, make sure to fail the test. "
+                "We don't expect it because the signature failure should cause us to backoff "
+                "and not asking about pulled_event_without_signatures="
+                f"{pulled_event_without_signatures.event_id} again"
+            )
+
+        if room_state_endpoint_requested_count > 0:
+            self.fail(
+                "We don't expect an outbound request to /state in the happy path but if "
+                "the logic is sneaking around what we expect, make sure to fail the test. "
+                "We don't expect it because the signature failure should cause us to backoff "
+                "and not asking about pulled_event_without_signatures="
+                f"{pulled_event_without_signatures.event_id} again"
+            )
+
+        # Make sure we only recorded a single failure which corresponds to the signature
+        # failure initially in `_check_sigs_and_hash_for_pulled_events_and_fetch` before
+        # we process all of the pulled events.
+        backfill_num_attempts_for_event_without_signatures = self.get_success(
+            main_store.db_pool.simple_select_one_onecol(
+                table="event_failed_pull_attempts",
+                keyvalues={"event_id": pulled_event_without_signatures.event_id},
+                retcol="num_attempts",
+            )
+        )
+        self.assertEqual(backfill_num_attempts_for_event_without_signatures, 1)
+
+        # And make sure we didn't record a failure for the event that has the missing
+        # prev_event because we don't want to cause a cascade of failures. Not being
+        # able to fetch the `prev_events` just means we won't be able to de-outlier the
+        # pulled event. But we can still use an `outlier` in the state/auth chain for
+        # another event. So we shouldn't stop a downstream event from trying to pull it.
+        self.get_failure(
+            main_store.db_pool.simple_select_one_onecol(
+                table="event_failed_pull_attempts",
+                keyvalues={"event_id": pulled_event.event_id},
+                retcol="num_attempts",
+            ),
+            # StoreError: 404: No row found
+            StoreError,
+        )
+
     def test_process_pulled_event_with_rejected_missing_state(self) -> None:
         """Ensure that we correctly handle pulled events with missing state containing a
         rejected state event
diff --git a/tests/http/test_endpoint.py b/tests/http/test_endpoint.py
index c8cc21cadd..a801f002a0 100644
--- a/tests/http/test_endpoint.py
+++ b/tests/http/test_endpoint.py
@@ -25,6 +25,8 @@ class ServerNameTestCase(unittest.TestCase):
             "[0abc:1def::1234]": ("[0abc:1def::1234]", None),
             "1.2.3.4:1": ("1.2.3.4", 1),
             "[0abc:1def::1234]:8080": ("[0abc:1def::1234]", 8080),
+            ":80": ("", 80),
+            "": ("", None),
         }
 
         for i, o in test_data.items():
@@ -42,6 +44,7 @@ class ServerNameTestCase(unittest.TestCase):
             "newline.com\n",
             ".empty-label.com",
             "1234:5678:80",  # too many colons
+            ":80",
         ]
         for i in test_data:
             try:
diff --git a/tests/logging/test_terse_json.py b/tests/logging/test_terse_json.py
index 96f399b7ab..0b0d8737c1 100644
--- a/tests/logging/test_terse_json.py
+++ b/tests/logging/test_terse_json.py
@@ -153,6 +153,7 @@ class TerseJsonTestCase(LoggerCleanupMixin, TestCase):
         site.site_tag = "test-site"
         site.server_version_string = "Server v1"
         site.reactor = Mock()
+        site.experimental_cors_msc3886 = False
         request = SynapseRequest(FakeChannel(site, None), site)
         # Call requestReceived to finish instantiating the object.
         request.content = BytesIO()
diff --git a/tests/push/test_push_rule_evaluator.py b/tests/push/test_push_rule_evaluator.py
index 8804f0e0d3..decf619466 100644
--- a/tests/push/test_push_rule_evaluator.py
+++ b/tests/push/test_push_rule_evaluator.py
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import Dict, Optional, Set, Tuple, Union
+from typing import Dict, Optional, Union
 
 import frozendict
 
@@ -38,12 +38,7 @@ from tests.test_utils.event_injection import create_event, inject_member_event
 
 
 class PushRuleEvaluatorTestCase(unittest.TestCase):
-    def _get_evaluator(
-        self,
-        content: JsonDict,
-        relations: Optional[Dict[str, Set[Tuple[str, str]]]] = None,
-        relations_match_enabled: bool = False,
-    ) -> PushRuleEvaluator:
+    def _get_evaluator(self, content: JsonDict) -> PushRuleEvaluator:
         event = FrozenEvent(
             {
                 "event_id": "$event_id",
@@ -63,8 +58,6 @@ class PushRuleEvaluatorTestCase(unittest.TestCase):
             room_member_count,
             sender_power_level,
             power_levels.get("notifications", {}),
-            relations or {},
-            relations_match_enabled,
         )
 
     def test_display_name(self) -> None:
@@ -299,71 +292,6 @@ class PushRuleEvaluatorTestCase(unittest.TestCase):
             {"sound": "default", "highlight": True},
         )
 
-    def test_relation_match(self) -> None:
-        """Test the relation_match push rule kind."""
-
-        # Check if the experimental feature is disabled.
-        evaluator = self._get_evaluator(
-            {}, {"m.annotation": {("@user:test", "m.reaction")}}
-        )
-
-        # A push rule evaluator with the experimental rule enabled.
-        evaluator = self._get_evaluator(
-            {}, {"m.annotation": {("@user:test", "m.reaction")}}, True
-        )
-
-        # Check just relation type.
-        condition = {
-            "kind": "org.matrix.msc3772.relation_match",
-            "rel_type": "m.annotation",
-        }
-        self.assertTrue(evaluator.matches(condition, "@user:test", "foo"))
-
-        # Check relation type and sender.
-        condition = {
-            "kind": "org.matrix.msc3772.relation_match",
-            "rel_type": "m.annotation",
-            "sender": "@user:test",
-        }
-        self.assertTrue(evaluator.matches(condition, "@user:test", "foo"))
-        condition = {
-            "kind": "org.matrix.msc3772.relation_match",
-            "rel_type": "m.annotation",
-            "sender": "@other:test",
-        }
-        self.assertFalse(evaluator.matches(condition, "@user:test", "foo"))
-
-        # Check relation type and event type.
-        condition = {
-            "kind": "org.matrix.msc3772.relation_match",
-            "rel_type": "m.annotation",
-            "type": "m.reaction",
-        }
-        self.assertTrue(evaluator.matches(condition, "@user:test", "foo"))
-
-        # Check just sender, this fails since rel_type is required.
-        condition = {
-            "kind": "org.matrix.msc3772.relation_match",
-            "sender": "@user:test",
-        }
-        self.assertFalse(evaluator.matches(condition, "@user:test", "foo"))
-
-        # Check sender glob.
-        condition = {
-            "kind": "org.matrix.msc3772.relation_match",
-            "rel_type": "m.annotation",
-            "sender": "@*:test",
-        }
-        self.assertTrue(evaluator.matches(condition, "@user:test", "foo"))
-
-        # Check event type glob.
-        condition = {
-            "kind": "org.matrix.msc3772.relation_match",
-            "rel_type": "m.annotation",
-            "event_type": "*.reaction",
-        }
-        self.assertTrue(evaluator.matches(condition, "@user:test", "foo"))
-
 
 class TestBulkPushRuleEvaluator(unittest.HomeserverTestCase):
     """Tests for the bulk push rule evaluator"""
diff --git a/tests/rest/client/test_relations.py b/tests/rest/client/test_relations.py
index 988cdb746d..ddf315b894 100644
--- a/tests/rest/client/test_relations.py
+++ b/tests/rest/client/test_relations.py
@@ -1677,7 +1677,6 @@ class RelationRedactionTestCase(BaseRelationsTestCase):
             {"chunk": [{"type": "m.reaction", "key": "👍", "count": 1}]},
         )
 
-    @unittest.override_config({"experimental_features": {"msc3440_enabled": True}})
     def test_redact_parent_thread(self) -> None:
         """
         Test that thread replies are still available when the root event is redacted.
@@ -1707,3 +1706,165 @@ class RelationRedactionTestCase(BaseRelationsTestCase):
             relations[RelationTypes.THREAD]["latest_event"]["event_id"],
             related_event_id,
         )
+
+
+class ThreadsTestCase(BaseRelationsTestCase):
+    def _get_threads(self, body: JsonDict) -> List[Tuple[str, str]]:
+        return [
+            (
+                ev["event_id"],
+                ev["unsigned"]["m.relations"]["m.thread"]["latest_event"]["event_id"],
+            )
+            for ev in body["chunk"]
+        ]
+
+    def test_threads(self) -> None:
+        """Create threads and ensure the ordering is due to their latest event."""
+        # Create 2 threads.
+        thread_1 = self.parent_id
+        res = self.helper.send(self.room, body="Thread Root!", tok=self.user_token)
+        thread_2 = res["event_id"]
+
+        channel = self._send_relation(RelationTypes.THREAD, "m.room.test")
+        reply_1 = channel.json_body["event_id"]
+        channel = self._send_relation(
+            RelationTypes.THREAD, "m.room.test", parent_id=thread_2
+        )
+        reply_2 = channel.json_body["event_id"]
+
+        # Request the threads in the room.
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/v1/rooms/{self.room}/threads",
+            access_token=self.user_token,
+        )
+        self.assertEquals(200, channel.code, channel.json_body)
+        threads = self._get_threads(channel.json_body)
+        self.assertEqual(threads, [(thread_2, reply_2), (thread_1, reply_1)])
+
+        # Update the first thread, the ordering should swap.
+        channel = self._send_relation(RelationTypes.THREAD, "m.room.test")
+        reply_3 = channel.json_body["event_id"]
+
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/v1/rooms/{self.room}/threads",
+            access_token=self.user_token,
+        )
+        self.assertEquals(200, channel.code, channel.json_body)
+        # Tuple of (thread ID, latest event ID) for each thread.
+        threads = self._get_threads(channel.json_body)
+        self.assertEqual(threads, [(thread_1, reply_3), (thread_2, reply_2)])
+
+    def test_pagination(self) -> None:
+        """Create threads and paginate through them."""
+        # Create 2 threads.
+        thread_1 = self.parent_id
+        res = self.helper.send(self.room, body="Thread Root!", tok=self.user_token)
+        thread_2 = res["event_id"]
+
+        self._send_relation(RelationTypes.THREAD, "m.room.test")
+        self._send_relation(RelationTypes.THREAD, "m.room.test", parent_id=thread_2)
+
+        # Request the threads in the room.
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/v1/rooms/{self.room}/threads?limit=1",
+            access_token=self.user_token,
+        )
+        self.assertEquals(200, channel.code, channel.json_body)
+        thread_roots = [ev["event_id"] for ev in channel.json_body["chunk"]]
+        self.assertEqual(thread_roots, [thread_2])
+
+        # Make sure next_batch has something in it that looks like it could be a
+        # valid token.
+        next_batch = channel.json_body.get("next_batch")
+        self.assertIsInstance(next_batch, str, channel.json_body)
+
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/v1/rooms/{self.room}/threads?limit=1&from={next_batch}",
+            access_token=self.user_token,
+        )
+        self.assertEquals(200, channel.code, channel.json_body)
+        thread_roots = [ev["event_id"] for ev in channel.json_body["chunk"]]
+        self.assertEqual(thread_roots, [thread_1], channel.json_body)
+
+        self.assertNotIn("next_batch", channel.json_body, channel.json_body)
+
+    def test_include(self) -> None:
+        """Filtering threads to all or participated in should work."""
+        # Thread 1 has the user as the root event.
+        thread_1 = self.parent_id
+        self._send_relation(
+            RelationTypes.THREAD, "m.room.test", access_token=self.user2_token
+        )
+
+        # Thread 2 has the user replying.
+        res = self.helper.send(self.room, body="Thread Root!", tok=self.user2_token)
+        thread_2 = res["event_id"]
+        self._send_relation(RelationTypes.THREAD, "m.room.test", parent_id=thread_2)
+
+        # Thread 3 has the user not participating in.
+        res = self.helper.send(self.room, body="Another thread!", tok=self.user2_token)
+        thread_3 = res["event_id"]
+        self._send_relation(
+            RelationTypes.THREAD,
+            "m.room.test",
+            access_token=self.user2_token,
+            parent_id=thread_3,
+        )
+
+        # All threads in the room.
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/v1/rooms/{self.room}/threads",
+            access_token=self.user_token,
+        )
+        self.assertEquals(200, channel.code, channel.json_body)
+        thread_roots = [ev["event_id"] for ev in channel.json_body["chunk"]]
+        self.assertEqual(
+            thread_roots, [thread_3, thread_2, thread_1], channel.json_body
+        )
+
+        # Only participated threads.
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/v1/rooms/{self.room}/threads?include=participated",
+            access_token=self.user_token,
+        )
+        self.assertEquals(200, channel.code, channel.json_body)
+        thread_roots = [ev["event_id"] for ev in channel.json_body["chunk"]]
+        self.assertEqual(thread_roots, [thread_2, thread_1], channel.json_body)
+
+    def test_ignored_user(self) -> None:
+        """Events from ignored users should be ignored."""
+        # Thread 1 has a reply from an ignored user.
+        thread_1 = self.parent_id
+        self._send_relation(
+            RelationTypes.THREAD, "m.room.test", access_token=self.user2_token
+        )
+
+        # Thread 2 is created by an ignored user.
+        res = self.helper.send(self.room, body="Thread Root!", tok=self.user2_token)
+        thread_2 = res["event_id"]
+        self._send_relation(RelationTypes.THREAD, "m.room.test", parent_id=thread_2)
+
+        # Ignore user2.
+        self.get_success(
+            self.store.add_account_data_for_user(
+                self.user_id,
+                AccountDataTypes.IGNORED_USER_LIST,
+                {"ignored_users": {self.user2_id: {}}},
+            )
+        )
+
+        # Only thread 1 is returned.
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/v1/rooms/{self.room}/threads",
+            access_token=self.user_token,
+        )
+        self.assertEquals(200, channel.code, channel.json_body)
+        thread_roots = [ev["event_id"] for ev in channel.json_body["chunk"]]
+        self.assertEqual(thread_roots, [thread_1], channel.json_body)
diff --git a/tests/rest/client/test_rendezvous.py b/tests/rest/client/test_rendezvous.py
new file mode 100644
index 0000000000..ad00a476e1
--- /dev/null
+++ b/tests/rest/client/test_rendezvous.py
@@ -0,0 +1,45 @@
+# Copyright 2022 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from twisted.test.proto_helpers import MemoryReactor
+
+from synapse.rest.client import rendezvous
+from synapse.server import HomeServer
+from synapse.util import Clock
+
+from tests import unittest
+from tests.unittest import override_config
+
+endpoint = "/_matrix/client/unstable/org.matrix.msc3886/rendezvous"
+
+
+class RendezvousServletTestCase(unittest.HomeserverTestCase):
+
+    servlets = [
+        rendezvous.register_servlets,
+    ]
+
+    def make_homeserver(self, reactor: MemoryReactor, clock: Clock) -> HomeServer:
+        self.hs = self.setup_test_homeserver()
+        return self.hs
+
+    def test_disabled(self) -> None:
+        channel = self.make_request("POST", endpoint, {}, access_token=None)
+        self.assertEqual(channel.code, 400)
+
+    @override_config({"experimental_features": {"msc3886_endpoint": "/asd"}})
+    def test_redirect(self) -> None:
+        channel = self.make_request("POST", endpoint, {}, access_token=None)
+        self.assertEqual(channel.code, 307)
+        self.assertEqual(channel.headers.getRawHeaders("Location"), ["/asd"])
diff --git a/tests/rest/client/test_rooms.py b/tests/rest/client/test_rooms.py
index 3612ebe7b9..716366eb90 100644
--- a/tests/rest/client/test_rooms.py
+++ b/tests/rest/client/test_rooms.py
@@ -35,11 +35,12 @@ from synapse.api.constants import (
     EventTypes,
     Membership,
     PublicRoomsFilterFields,
-    RelationTypes,
     RoomTypes,
 )
 from synapse.api.errors import Codes, HttpResponseException
 from synapse.appservice import ApplicationService
+from synapse.events import EventBase
+from synapse.events.snapshot import EventContext
 from synapse.handlers.pagination import PurgeStatus
 from synapse.rest import admin
 from synapse.rest.client import account, directory, login, profile, register, room, sync
@@ -50,7 +51,9 @@ from synapse.util.stringutils import random_string
 
 from tests import unittest
 from tests.http.server._base import make_request_with_cancellation_test
+from tests.storage.test_stream import PaginationTestCase
 from tests.test_utils import make_awaitable
+from tests.test_utils.event_injection import create_event
 
 PATH_PREFIX = b"/_matrix/client/api/v1"
 
@@ -2915,149 +2918,20 @@ class LabelsTestCase(unittest.HomeserverTestCase):
         return event_id
 
 
-class RelationsTestCase(unittest.HomeserverTestCase):
-    servlets = [
-        synapse.rest.admin.register_servlets_for_client_rest_resource,
-        room.register_servlets,
-        login.register_servlets,
-    ]
-
-    def default_config(self) -> Dict[str, Any]:
-        config = super().default_config()
-        config["experimental_features"] = {"msc3440_enabled": True}
-        return config
-
-    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
-        self.user_id = self.register_user("test", "test")
-        self.tok = self.login("test", "test")
-        self.room_id = self.helper.create_room_as(self.user_id, tok=self.tok)
-
-        self.second_user_id = self.register_user("second", "test")
-        self.second_tok = self.login("second", "test")
-        self.helper.join(
-            room=self.room_id, user=self.second_user_id, tok=self.second_tok
-        )
-
-        self.third_user_id = self.register_user("third", "test")
-        self.third_tok = self.login("third", "test")
-        self.helper.join(room=self.room_id, user=self.third_user_id, tok=self.third_tok)
-
-        # An initial event with a relation from second user.
-        res = self.helper.send_event(
-            room_id=self.room_id,
-            type=EventTypes.Message,
-            content={"msgtype": "m.text", "body": "Message 1"},
-            tok=self.tok,
-        )
-        self.event_id_1 = res["event_id"]
-        self.helper.send_event(
-            room_id=self.room_id,
-            type="m.reaction",
-            content={
-                "m.relates_to": {
-                    "rel_type": RelationTypes.ANNOTATION,
-                    "event_id": self.event_id_1,
-                    "key": "👍",
-                }
-            },
-            tok=self.second_tok,
-        )
-
-        # Another event with a relation from third user.
-        res = self.helper.send_event(
-            room_id=self.room_id,
-            type=EventTypes.Message,
-            content={"msgtype": "m.text", "body": "Message 2"},
-            tok=self.tok,
-        )
-        self.event_id_2 = res["event_id"]
-        self.helper.send_event(
-            room_id=self.room_id,
-            type="m.reaction",
-            content={
-                "m.relates_to": {
-                    "rel_type": RelationTypes.REFERENCE,
-                    "event_id": self.event_id_2,
-                }
-            },
-            tok=self.third_tok,
-        )
-
-        # An event with no relations.
-        self.helper.send_event(
-            room_id=self.room_id,
-            type=EventTypes.Message,
-            content={"msgtype": "m.text", "body": "No relations"},
-            tok=self.tok,
-        )
-
-    def _filter_messages(self, filter: JsonDict) -> List[JsonDict]:
+class RelationsTestCase(PaginationTestCase):
+    def _filter_messages(self, filter: JsonDict) -> List[str]:
         """Make a request to /messages with a filter, returns the chunk of events."""
+        from_token = self.get_success(
+            self.from_token.to_string(self.hs.get_datastores().main)
+        )
         channel = self.make_request(
             "GET",
-            "/rooms/%s/messages?filter=%s&dir=b" % (self.room_id, json.dumps(filter)),
+            f"/rooms/{self.room_id}/messages?filter={json.dumps(filter)}&dir=f&from={from_token}",
             access_token=self.tok,
         )
         self.assertEqual(channel.code, HTTPStatus.OK, channel.result)
 
-        return channel.json_body["chunk"]
-
-    def test_filter_relation_senders(self) -> None:
-        # Messages which second user reacted to.
-        filter = {"related_by_senders": [self.second_user_id]}
-        chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 1, chunk)
-        self.assertEqual(chunk[0]["event_id"], self.event_id_1)
-
-        # Messages which third user reacted to.
-        filter = {"related_by_senders": [self.third_user_id]}
-        chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 1, chunk)
-        self.assertEqual(chunk[0]["event_id"], self.event_id_2)
-
-        # Messages which either user reacted to.
-        filter = {"related_by_senders": [self.second_user_id, self.third_user_id]}
-        chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 2, chunk)
-        self.assertCountEqual(
-            [c["event_id"] for c in chunk], [self.event_id_1, self.event_id_2]
-        )
-
-    def test_filter_relation_type(self) -> None:
-        # Messages which have annotations.
-        filter = {"related_by_rel_types": [RelationTypes.ANNOTATION]}
-        chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 1, chunk)
-        self.assertEqual(chunk[0]["event_id"], self.event_id_1)
-
-        # Messages which have references.
-        filter = {"related_by_rel_types": [RelationTypes.REFERENCE]}
-        chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 1, chunk)
-        self.assertEqual(chunk[0]["event_id"], self.event_id_2)
-
-        # Messages which have either annotations or references.
-        filter = {
-            "related_by_rel_types": [
-                RelationTypes.ANNOTATION,
-                RelationTypes.REFERENCE,
-            ]
-        }
-        chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 2, chunk)
-        self.assertCountEqual(
-            [c["event_id"] for c in chunk], [self.event_id_1, self.event_id_2]
-        )
-
-    def test_filter_relation_senders_and_type(self) -> None:
-        # Messages which second user reacted to.
-        filter = {
-            "related_by_senders": [self.second_user_id],
-            "related_by_rel_types": [RelationTypes.ANNOTATION],
-        }
-        chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 1, chunk)
-        self.assertEqual(chunk[0]["event_id"], self.event_id_1)
+        return [ev["event_id"] for ev in channel.json_body["chunk"]]
 
 
 class ContextTestCase(unittest.HomeserverTestCase):
@@ -3615,3 +3489,65 @@ class ThreepidInviteTestCase(unittest.HomeserverTestCase):
         )
         self.assertEqual(channel.code, 400)
         self.assertEqual(channel.json_body["errcode"], "M_MISSING_PARAM")
+
+
+class TimestampLookupTestCase(unittest.HomeserverTestCase):
+    servlets = [
+        admin.register_servlets,
+        room.register_servlets,
+        login.register_servlets,
+    ]
+
+    def default_config(self) -> JsonDict:
+        config = super().default_config()
+        config["experimental_features"] = {"msc3030_enabled": True}
+        return config
+
+    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
+        self._storage_controllers = self.hs.get_storage_controllers()
+
+        self.room_owner = self.register_user("room_owner", "test")
+        self.room_owner_tok = self.login("room_owner", "test")
+
+    def _inject_outlier(self, room_id: str) -> EventBase:
+        event, _context = self.get_success(
+            create_event(
+                self.hs,
+                room_id=room_id,
+                type="m.test",
+                sender="@test_remote_user:remote",
+            )
+        )
+
+        event.internal_metadata.outlier = True
+        self.get_success(
+            self._storage_controllers.persistence.persist_event(
+                event, EventContext.for_outlier(self._storage_controllers)
+            )
+        )
+        return event
+
+    def test_no_outliers(self) -> None:
+        """
+        Test to make sure `/timestamp_to_event` does not return `outlier` events.
+        We're unable to determine whether an `outlier` is next to a gap so we
+        don't know whether it's actually the closest event. Instead, let's just
+        ignore `outliers` with this endpoint.
+
+        This test is really seeing that we choose the non-`outlier` event behind the
+        `outlier`. Since the gap checking logic considers the latest message in the room
+        as *not* next to a gap, asking over federation does not come into play here.
+        """
+        room_id = self.helper.create_room_as(self.room_owner, tok=self.room_owner_tok)
+
+        outlier_event = self._inject_outlier(room_id)
+
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/unstable/org.matrix.msc3030/rooms/{room_id}/timestamp_to_event?dir=b&ts={outlier_event.origin_server_ts}",
+            access_token=self.room_owner_tok,
+        )
+        self.assertEqual(HTTPStatus.OK, channel.code, msg=channel.json_body)
+
+        # Make sure the outlier event is not returned
+        self.assertNotEqual(channel.json_body["event_id"], outlier_event.event_id)
diff --git a/tests/rest/client/test_typing.py b/tests/rest/client/test_typing.py
index 61b66d7685..fdc433a8b5 100644
--- a/tests/rest/client/test_typing.py
+++ b/tests/rest/client/test_typing.py
@@ -59,7 +59,8 @@ class RoomTypingTestCase(unittest.HomeserverTestCase):
             self.event_source.get_new_events(
                 user=UserID.from_string(self.user_id),
                 from_key=0,
-                limit=None,
+                # Limit is unused.
+                limit=0,
                 room_ids=[self.room_id],
                 is_guest=False,
             )
diff --git a/tests/rest/key/v2/test_remote_key_resource.py b/tests/rest/key/v2/test_remote_key_resource.py
index ac0ac06b7e..7f1fba1086 100644
--- a/tests/rest/key/v2/test_remote_key_resource.py
+++ b/tests/rest/key/v2/test_remote_key_resource.py
@@ -26,7 +26,7 @@ from twisted.web.resource import NoResource, Resource
 
 from synapse.crypto.keyring import PerspectivesKeyFetcher
 from synapse.http.site import SynapseRequest
-from synapse.rest.key.v2 import KeyApiV2Resource
+from synapse.rest.key.v2 import KeyResource
 from synapse.server import HomeServer
 from synapse.storage.keys import FetchKeyResult
 from synapse.types import JsonDict
@@ -46,7 +46,7 @@ class BaseRemoteKeyResourceTestCase(unittest.HomeserverTestCase):
 
     def create_test_resource(self) -> Resource:
         return create_resource_tree(
-            {"/_matrix/key/v2": KeyApiV2Resource(self.hs)}, root_resource=NoResource()
+            {"/_matrix/key/v2": KeyResource(self.hs)}, root_resource=NoResource()
         )
 
     def expect_outgoing_key_request(
diff --git a/tests/server.py b/tests/server.py
index c447d5e4c4..8b1d186219 100644
--- a/tests/server.py
+++ b/tests/server.py
@@ -266,7 +266,12 @@ class FakeSite:
     site_tag = "test"
     access_logger = logging.getLogger("synapse.access.http.fake")
 
-    def __init__(self, resource: IResource, reactor: IReactorTime):
+    def __init__(
+        self,
+        resource: IResource,
+        reactor: IReactorTime,
+        experimental_cors_msc3886: bool = False,
+    ):
         """
 
         Args:
@@ -274,6 +279,7 @@ class FakeSite:
         """
         self._resource = resource
         self.reactor = reactor
+        self.experimental_cors_msc3886 = experimental_cors_msc3886
 
     def getResourceFor(self, request):
         return self._resource
diff --git a/tests/storage/databases/main/test_events_worker.py b/tests/storage/databases/main/test_events_worker.py
index 32a798d74b..5773172ab8 100644
--- a/tests/storage/databases/main/test_events_worker.py
+++ b/tests/storage/databases/main/test_events_worker.py
@@ -90,18 +90,6 @@ class HaveSeenEventsTestCase(unittest.HomeserverTestCase):
             self.assertEqual(res, {self.event_ids[0]})
             self.assertEqual(ctx.get_resource_usage().db_txn_count, 0)
 
-    def test_query_via_event_cache(self):
-        # fetch an event into the event cache
-        self.get_success(self.store.get_event(self.event_ids[0]))
-
-        # looking it up should now cause no db hits
-        with LoggingContext(name="test") as ctx:
-            res = self.get_success(
-                self.store.have_seen_events(self.room_id, [self.event_ids[0]])
-            )
-            self.assertEqual(res, {self.event_ids[0]})
-            self.assertEqual(ctx.get_resource_usage().db_txn_count, 0)
-
     def test_persisting_event_invalidates_cache(self):
         """
         Test to make sure that the `have_seen_event` cache
diff --git a/tests/storage/test_event_federation.py b/tests/storage/test_event_federation.py
index 59b8910907..853db930d6 100644
--- a/tests/storage/test_event_federation.py
+++ b/tests/storage/test_event_federation.py
@@ -27,6 +27,8 @@ from synapse.api.room_versions import (
     RoomVersion,
 )
 from synapse.events import _EventInternalMetadata
+from synapse.rest import admin
+from synapse.rest.client import login, room
 from synapse.server import HomeServer
 from synapse.storage.database import LoggingTransaction
 from synapse.types import JsonDict
@@ -43,6 +45,12 @@ class _BackfillSetupInfo:
 
 
 class EventFederationWorkerStoreTestCase(tests.unittest.HomeserverTestCase):
+    servlets = [
+        admin.register_servlets,
+        room.register_servlets,
+        login.register_servlets,
+    ]
+
     def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
         self.store = hs.get_datastores().main
 
@@ -1122,6 +1130,62 @@ class EventFederationWorkerStoreTestCase(tests.unittest.HomeserverTestCase):
         backfill_event_ids = [backfill_point[0] for backfill_point in backfill_points]
         self.assertEqual(backfill_event_ids, ["insertion_eventA"])
 
+    def test_get_event_ids_to_not_pull_from_backoff(
+        self,
+    ):
+        """
+        Test to make sure only event IDs we should backoff from are returned.
+        """
+        # Create the room
+        user_id = self.register_user("alice", "test")
+        tok = self.login("alice", "test")
+        room_id = self.helper.create_room_as(room_creator=user_id, tok=tok)
+
+        self.get_success(
+            self.store.record_event_failed_pull_attempt(
+                room_id, "$failed_event_id", "fake cause"
+            )
+        )
+
+        event_ids_to_backoff = self.get_success(
+            self.store.get_event_ids_to_not_pull_from_backoff(
+                room_id=room_id, event_ids=["$failed_event_id", "$normal_event_id"]
+            )
+        )
+
+        self.assertEqual(event_ids_to_backoff, ["$failed_event_id"])
+
+    def test_get_event_ids_to_not_pull_from_backoff_retry_after_backoff_duration(
+        self,
+    ):
+        """
+        Test to make sure no event IDs are returned after the backoff duration has
+        elapsed.
+        """
+        # Create the room
+        user_id = self.register_user("alice", "test")
+        tok = self.login("alice", "test")
+        room_id = self.helper.create_room_as(room_creator=user_id, tok=tok)
+
+        self.get_success(
+            self.store.record_event_failed_pull_attempt(
+                room_id, "$failed_event_id", "fake cause"
+            )
+        )
+
+        # Now advance time by 2 hours so we wait long enough for the single failed
+        # attempt (2^1 hours).
+        self.reactor.advance(datetime.timedelta(hours=2).total_seconds())
+
+        event_ids_to_backoff = self.get_success(
+            self.store.get_event_ids_to_not_pull_from_backoff(
+                room_id=room_id, event_ids=["$failed_event_id", "$normal_event_id"]
+            )
+        )
+        # Since this function only returns events we should backoff from, time has
+        # elapsed past the backoff range so there is no events to backoff from.
+        self.assertEqual(event_ids_to_backoff, [])
+
 
 @attr.s
 class FakeEvent:
diff --git a/tests/storage/test_relations.py b/tests/storage/test_relations.py
new file mode 100644
index 0000000000..cd1d00208b
--- /dev/null
+++ b/tests/storage/test_relations.py
@@ -0,0 +1,111 @@
+# Copyright 2022 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from twisted.test.proto_helpers import MemoryReactor
+
+from synapse.api.constants import MAIN_TIMELINE
+from synapse.server import HomeServer
+from synapse.util import Clock
+
+from tests import unittest
+
+
+class RelationsStoreTestCase(unittest.HomeserverTestCase):
+    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
+        """
+        Creates a DAG:
+
+            A <---[m.thread]-- B <--[m.annotation]-- C
+            ^
+            |--[m.reference]-- D <--[m.annotation]-- E
+
+            F <--[m.annotation]-- G
+
+        """
+        self._main_store = self.hs.get_datastores().main
+
+        self._create_relation("A", "B", "m.thread")
+        self._create_relation("B", "C", "m.annotation")
+        self._create_relation("A", "D", "m.reference")
+        self._create_relation("D", "E", "m.annotation")
+        self._create_relation("F", "G", "m.annotation")
+
+    def _create_relation(self, parent_id: str, event_id: str, rel_type: str) -> None:
+        self.get_success(
+            self._main_store.db_pool.simple_insert(
+                table="event_relations",
+                values={
+                    "event_id": event_id,
+                    "relates_to_id": parent_id,
+                    "relation_type": rel_type,
+                },
+            )
+        )
+
+    def test_get_thread_id(self) -> None:
+        """
+        Ensure that get_thread_id only searches up the tree for threads.
+        """
+        # The thread itself and children of it return the thread.
+        thread_id = self.get_success(self._main_store.get_thread_id("B"))
+        self.assertEqual("A", thread_id)
+
+        thread_id = self.get_success(self._main_store.get_thread_id("C"))
+        self.assertEqual("A", thread_id)
+
+        # But the root and events related to the root do not.
+        thread_id = self.get_success(self._main_store.get_thread_id("A"))
+        self.assertEqual(MAIN_TIMELINE, thread_id)
+
+        thread_id = self.get_success(self._main_store.get_thread_id("D"))
+        self.assertEqual(MAIN_TIMELINE, thread_id)
+
+        thread_id = self.get_success(self._main_store.get_thread_id("E"))
+        self.assertEqual(MAIN_TIMELINE, thread_id)
+
+        # Events which are not related to a thread at all should return the
+        # main timeline.
+        thread_id = self.get_success(self._main_store.get_thread_id("F"))
+        self.assertEqual(MAIN_TIMELINE, thread_id)
+
+        thread_id = self.get_success(self._main_store.get_thread_id("G"))
+        self.assertEqual(MAIN_TIMELINE, thread_id)
+
+    def test_get_thread_id_for_receipts(self) -> None:
+        """
+        Ensure that get_thread_id_for_receipts searches up and down the tree for a thread.
+        """
+        # All of the events are considered related to this thread.
+        thread_id = self.get_success(self._main_store.get_thread_id_for_receipts("A"))
+        self.assertEqual("A", thread_id)
+
+        thread_id = self.get_success(self._main_store.get_thread_id_for_receipts("B"))
+        self.assertEqual("A", thread_id)
+
+        thread_id = self.get_success(self._main_store.get_thread_id_for_receipts("C"))
+        self.assertEqual("A", thread_id)
+
+        thread_id = self.get_success(self._main_store.get_thread_id_for_receipts("D"))
+        self.assertEqual("A", thread_id)
+
+        thread_id = self.get_success(self._main_store.get_thread_id_for_receipts("E"))
+        self.assertEqual("A", thread_id)
+
+        # Events which are not related to a thread at all should return the
+        # main timeline.
+        thread_id = self.get_success(self._main_store.get_thread_id("F"))
+        self.assertEqual(MAIN_TIMELINE, thread_id)
+
+        thread_id = self.get_success(self._main_store.get_thread_id("G"))
+        self.assertEqual(MAIN_TIMELINE, thread_id)
diff --git a/tests/storage/test_stream.py b/tests/storage/test_stream.py
index 78663a53fe..34fa810cf6 100644
--- a/tests/storage/test_stream.py
+++ b/tests/storage/test_stream.py
@@ -16,7 +16,6 @@ from typing import List
 
 from synapse.api.constants import EventTypes, RelationTypes
 from synapse.api.filtering import Filter
-from synapse.events import EventBase
 from synapse.rest import admin
 from synapse.rest.client import login, room
 from synapse.types import JsonDict
@@ -40,7 +39,7 @@ class PaginationTestCase(HomeserverTestCase):
 
     def default_config(self):
         config = super().default_config()
-        config["experimental_features"] = {"msc3440_enabled": True}
+        config["experimental_features"] = {"msc3874_enabled": True}
         return config
 
     def prepare(self, reactor, clock, homeserver):
@@ -58,6 +57,11 @@ class PaginationTestCase(HomeserverTestCase):
         self.third_tok = self.login("third", "test")
         self.helper.join(room=self.room_id, user=self.third_user_id, tok=self.third_tok)
 
+        # Store a token which is after all the room creation events.
+        self.from_token = self.get_success(
+            self.hs.get_event_sources().get_current_token_for_pagination(self.room_id)
+        )
+
         # An initial event with a relation from second user.
         res = self.helper.send_event(
             room_id=self.room_id,
@@ -66,7 +70,7 @@ class PaginationTestCase(HomeserverTestCase):
             tok=self.tok,
         )
         self.event_id_1 = res["event_id"]
-        self.helper.send_event(
+        res = self.helper.send_event(
             room_id=self.room_id,
             type="m.reaction",
             content={
@@ -78,6 +82,7 @@ class PaginationTestCase(HomeserverTestCase):
             },
             tok=self.second_tok,
         )
+        self.event_id_annotation = res["event_id"]
 
         # Another event with a relation from third user.
         res = self.helper.send_event(
@@ -87,7 +92,7 @@ class PaginationTestCase(HomeserverTestCase):
             tok=self.tok,
         )
         self.event_id_2 = res["event_id"]
-        self.helper.send_event(
+        res = self.helper.send_event(
             room_id=self.room_id,
             type="m.reaction",
             content={
@@ -98,68 +103,59 @@ class PaginationTestCase(HomeserverTestCase):
             },
             tok=self.third_tok,
         )
+        self.event_id_reference = res["event_id"]
 
         # An event with no relations.
-        self.helper.send_event(
+        res = self.helper.send_event(
             room_id=self.room_id,
             type=EventTypes.Message,
             content={"msgtype": "m.text", "body": "No relations"},
             tok=self.tok,
         )
+        self.event_id_none = res["event_id"]
 
-    def _filter_messages(self, filter: JsonDict) -> List[EventBase]:
+    def _filter_messages(self, filter: JsonDict) -> List[str]:
         """Make a request to /messages with a filter, returns the chunk of events."""
 
-        from_token = self.get_success(
-            self.hs.get_event_sources().get_current_token_for_pagination(self.room_id)
-        )
-
         events, next_key = self.get_success(
             self.hs.get_datastores().main.paginate_room_events(
                 room_id=self.room_id,
-                from_key=from_token.room_key,
+                from_key=self.from_token.room_key,
                 to_key=None,
-                direction="b",
+                direction="f",
                 limit=10,
                 event_filter=Filter(self.hs, filter),
             )
         )
 
-        return events
+        return [ev.event_id for ev in events]
 
     def test_filter_relation_senders(self):
         # Messages which second user reacted to.
         filter = {"related_by_senders": [self.second_user_id]}
         chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 1, chunk)
-        self.assertEqual(chunk[0].event_id, self.event_id_1)
+        self.assertEqual(chunk, [self.event_id_1])
 
         # Messages which third user reacted to.
         filter = {"related_by_senders": [self.third_user_id]}
         chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 1, chunk)
-        self.assertEqual(chunk[0].event_id, self.event_id_2)
+        self.assertEqual(chunk, [self.event_id_2])
 
         # Messages which either user reacted to.
         filter = {"related_by_senders": [self.second_user_id, self.third_user_id]}
         chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 2, chunk)
-        self.assertCountEqual(
-            [c.event_id for c in chunk], [self.event_id_1, self.event_id_2]
-        )
+        self.assertCountEqual(chunk, [self.event_id_1, self.event_id_2])
 
     def test_filter_relation_type(self):
         # Messages which have annotations.
         filter = {"related_by_rel_types": [RelationTypes.ANNOTATION]}
         chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 1, chunk)
-        self.assertEqual(chunk[0].event_id, self.event_id_1)
+        self.assertEqual(chunk, [self.event_id_1])
 
         # Messages which have references.
         filter = {"related_by_rel_types": [RelationTypes.REFERENCE]}
         chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 1, chunk)
-        self.assertEqual(chunk[0].event_id, self.event_id_2)
+        self.assertEqual(chunk, [self.event_id_2])
 
         # Messages which have either annotations or references.
         filter = {
@@ -169,10 +165,7 @@ class PaginationTestCase(HomeserverTestCase):
             ]
         }
         chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 2, chunk)
-        self.assertCountEqual(
-            [c.event_id for c in chunk], [self.event_id_1, self.event_id_2]
-        )
+        self.assertCountEqual(chunk, [self.event_id_1, self.event_id_2])
 
     def test_filter_relation_senders_and_type(self):
         # Messages which second user reacted to.
@@ -181,8 +174,7 @@ class PaginationTestCase(HomeserverTestCase):
             "related_by_rel_types": [RelationTypes.ANNOTATION],
         }
         chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 1, chunk)
-        self.assertEqual(chunk[0].event_id, self.event_id_1)
+        self.assertEqual(chunk, [self.event_id_1])
 
     def test_duplicate_relation(self):
         """An event should only be returned once if there are multiple relations to it."""
@@ -201,5 +193,65 @@ class PaginationTestCase(HomeserverTestCase):
 
         filter = {"related_by_senders": [self.second_user_id]}
         chunk = self._filter_messages(filter)
-        self.assertEqual(len(chunk), 1, chunk)
-        self.assertEqual(chunk[0].event_id, self.event_id_1)
+        self.assertEqual(chunk, [self.event_id_1])
+
+    def test_filter_rel_types(self) -> None:
+        # Messages which are annotations.
+        filter = {"org.matrix.msc3874.rel_types": [RelationTypes.ANNOTATION]}
+        chunk = self._filter_messages(filter)
+        self.assertEqual(chunk, [self.event_id_annotation])
+
+        # Messages which are references.
+        filter = {"org.matrix.msc3874.rel_types": [RelationTypes.REFERENCE]}
+        chunk = self._filter_messages(filter)
+        self.assertEqual(chunk, [self.event_id_reference])
+
+        # Messages which are either annotations or references.
+        filter = {
+            "org.matrix.msc3874.rel_types": [
+                RelationTypes.ANNOTATION,
+                RelationTypes.REFERENCE,
+            ]
+        }
+        chunk = self._filter_messages(filter)
+        self.assertCountEqual(
+            chunk,
+            [self.event_id_annotation, self.event_id_reference],
+        )
+
+    def test_filter_not_rel_types(self) -> None:
+        # Messages which are not annotations.
+        filter = {"org.matrix.msc3874.not_rel_types": [RelationTypes.ANNOTATION]}
+        chunk = self._filter_messages(filter)
+        self.assertEqual(
+            chunk,
+            [
+                self.event_id_1,
+                self.event_id_2,
+                self.event_id_reference,
+                self.event_id_none,
+            ],
+        )
+
+        # Messages which are not references.
+        filter = {"org.matrix.msc3874.not_rel_types": [RelationTypes.REFERENCE]}
+        chunk = self._filter_messages(filter)
+        self.assertEqual(
+            chunk,
+            [
+                self.event_id_1,
+                self.event_id_annotation,
+                self.event_id_2,
+                self.event_id_none,
+            ],
+        )
+
+        # Messages which are neither annotations or references.
+        filter = {
+            "org.matrix.msc3874.not_rel_types": [
+                RelationTypes.ANNOTATION,
+                RelationTypes.REFERENCE,
+            ]
+        }
+        chunk = self._filter_messages(filter)
+        self.assertEqual(chunk, [self.event_id_1, self.event_id_2, self.event_id_none])
diff --git a/tests/test_server.py b/tests/test_server.py
index 7c66448245..2d9a0257d4 100644
--- a/tests/test_server.py
+++ b/tests/test_server.py
@@ -222,13 +222,22 @@ class OptionsResourceTests(unittest.TestCase):
         self.resource = OptionsResource()
         self.resource.putChild(b"res", DummyResource())
 
-    def _make_request(self, method: bytes, path: bytes) -> FakeChannel:
+    def _make_request(
+        self, method: bytes, path: bytes, experimental_cors_msc3886: bool = False
+    ) -> FakeChannel:
         """Create a request from the method/path and return a channel with the response."""
         # Create a site and query for the resource.
         site = SynapseSite(
             "test",
             "site_tag",
-            parse_listener_def(0, {"type": "http", "port": 0}),
+            parse_listener_def(
+                0,
+                {
+                    "type": "http",
+                    "port": 0,
+                    "experimental_cors_msc3886": experimental_cors_msc3886,
+                },
+            ),
             self.resource,
             "1.0",
             max_request_body_size=4096,
@@ -239,25 +248,58 @@ class OptionsResourceTests(unittest.TestCase):
         channel = make_request(self.reactor, site, method, path, shorthand=False)
         return channel
 
+    def _check_cors_standard_headers(self, channel: FakeChannel) -> None:
+        # Ensure the correct CORS headers have been added
+        # as per https://spec.matrix.org/v1.4/client-server-api/#web-browser-clients
+        self.assertEqual(
+            channel.headers.getRawHeaders(b"Access-Control-Allow-Origin"),
+            [b"*"],
+            "has correct CORS Origin header",
+        )
+        self.assertEqual(
+            channel.headers.getRawHeaders(b"Access-Control-Allow-Methods"),
+            [b"GET, HEAD, POST, PUT, DELETE, OPTIONS"],  # HEAD isn't in the spec
+            "has correct CORS Methods header",
+        )
+        self.assertEqual(
+            channel.headers.getRawHeaders(b"Access-Control-Allow-Headers"),
+            [b"X-Requested-With, Content-Type, Authorization, Date"],
+            "has correct CORS Headers header",
+        )
+
+    def _check_cors_msc3886_headers(self, channel: FakeChannel) -> None:
+        # Ensure the correct CORS headers have been added
+        # as per https://github.com/matrix-org/matrix-spec-proposals/blob/hughns/simple-rendezvous-capability/proposals/3886-simple-rendezvous-capability.md#cors
+        self.assertEqual(
+            channel.headers.getRawHeaders(b"Access-Control-Allow-Origin"),
+            [b"*"],
+            "has correct CORS Origin header",
+        )
+        self.assertEqual(
+            channel.headers.getRawHeaders(b"Access-Control-Allow-Methods"),
+            [b"GET, HEAD, POST, PUT, DELETE, OPTIONS"],  # HEAD isn't in the spec
+            "has correct CORS Methods header",
+        )
+        self.assertEqual(
+            channel.headers.getRawHeaders(b"Access-Control-Allow-Headers"),
+            [
+                b"X-Requested-With, Content-Type, Authorization, Date, If-Match, If-None-Match"
+            ],
+            "has correct CORS Headers header",
+        )
+        self.assertEqual(
+            channel.headers.getRawHeaders(b"Access-Control-Expose-Headers"),
+            [b"ETag, Location, X-Max-Bytes"],
+            "has correct CORS Expose Headers header",
+        )
+
     def test_unknown_options_request(self) -> None:
         """An OPTIONS requests to an unknown URL still returns 204 No Content."""
         channel = self._make_request(b"OPTIONS", b"/foo/")
         self.assertEqual(channel.code, 204)
         self.assertNotIn("body", channel.result)
 
-        # Ensure the correct CORS headers have been added
-        self.assertTrue(
-            channel.headers.hasHeader(b"Access-Control-Allow-Origin"),
-            "has CORS Origin header",
-        )
-        self.assertTrue(
-            channel.headers.hasHeader(b"Access-Control-Allow-Methods"),
-            "has CORS Methods header",
-        )
-        self.assertTrue(
-            channel.headers.hasHeader(b"Access-Control-Allow-Headers"),
-            "has CORS Headers header",
-        )
+        self._check_cors_standard_headers(channel)
 
     def test_known_options_request(self) -> None:
         """An OPTIONS requests to an known URL still returns 204 No Content."""
@@ -265,19 +307,17 @@ class OptionsResourceTests(unittest.TestCase):
         self.assertEqual(channel.code, 204)
         self.assertNotIn("body", channel.result)
 
-        # Ensure the correct CORS headers have been added
-        self.assertTrue(
-            channel.headers.hasHeader(b"Access-Control-Allow-Origin"),
-            "has CORS Origin header",
-        )
-        self.assertTrue(
-            channel.headers.hasHeader(b"Access-Control-Allow-Methods"),
-            "has CORS Methods header",
-        )
-        self.assertTrue(
-            channel.headers.hasHeader(b"Access-Control-Allow-Headers"),
-            "has CORS Headers header",
+        self._check_cors_standard_headers(channel)
+
+    def test_known_options_request_msc3886(self) -> None:
+        """An OPTIONS requests to an known URL still returns 204 No Content."""
+        channel = self._make_request(
+            b"OPTIONS", b"/res/", experimental_cors_msc3886=True
         )
+        self.assertEqual(channel.code, 204)
+        self.assertNotIn("body", channel.result)
+
+        self._check_cors_msc3886_headers(channel)
 
     def test_unknown_request(self) -> None:
         """A non-OPTIONS request to an unknown URL should 404."""
diff --git a/tests/util/caches/test_descriptors.py b/tests/util/caches/test_descriptors.py
index 90861fe522..78fd7b6961 100644
--- a/tests/util/caches/test_descriptors.py
+++ b/tests/util/caches/test_descriptors.py
@@ -1037,5 +1037,5 @@ class CachedListDescriptorTestCase(unittest.TestCase):
         obj = Cls()
 
         # Make sure this raises an error about the arg mismatch
-        with self.assertRaises(Exception):
+        with self.assertRaises(TypeError):
             obj.list_fn([("foo", "bar")])
author	H. Shay <hillerys@element.io>	2022-10-20 14:22:21 -0700
committer	H. Shay <hillerys@element.io>	2022-10-20 14:22:21 -0700
commit	63f8ee4007e736be8f9c8666f534cc3e867bbf2f (patch)
tree	e2aa4481f7a331bbdd26f4bbebee97dfc5feb35f
parent	add version of eventcontext without state group (diff)
parent	Use servlets for /key/ endpoints. (#14229) (diff)
download	synapse-63f8ee4007e736be8f9c8666f534cc3e867bbf2f.tar.xz