FIXUP

Merge branch 'madlittlemods/sliding-sync-pre-populate-room-meta-data' into erikj/ss_hacks
2024-08-28 15:05:56 +01:00 · 2024-08-28 15:04:48 +01:00 · 2024-08-28 14:58:31 +01:00 · 2024-08-28 14:39:25 +01:00 · 2024-08-28 14:23:32 +01:00 · 2024-08-28 14:23:06 +01:00
174 changed files with 27230 additions and 4819 deletions
@@ -30,7 +30,7 @@ jobs:
        run: docker buildx inspect

      - name: Install Cosign
-        uses: sigstore/cosign-installer@v3.5.0
+        uses: sigstore/cosign-installer@v3.6.0

      - name: Checkout repository
        uses: actions/checkout@v4
@@ -73,7 +73,7 @@ jobs:
            - 'pyproject.toml'
            - 'poetry.lock'
            - '.github/workflows/tests.yml'
-          
+
          linting_readme:
            - 'README.rst'

@@ -139,7 +139,7 @@ jobs:

      - name: Semantic checks (ruff)
        # --quiet suppresses the update check.
-        run: poetry run ruff --quiet .
+        run: poetry run ruff check --quiet .

  lint-mypy:
    runs-on: ubuntu-latest
@@ -305,7 +305,7 @@ jobs:
      - lint-readme
    runs-on: ubuntu-latest
    steps:
-      - uses: matrix-org/done-action@v2
+      - uses: matrix-org/done-action@v3
        with:
          needs: ${{ toJSON(needs) }}

@@ -737,7 +737,7 @@ jobs:
      - linting-done
    runs-on: ubuntu-latest
    steps:
-      - uses: matrix-org/done-action@v2
+      - uses: matrix-org/done-action@v3
        with:
          needs: ${{ toJSON(needs) }}

@@ -1,3 +1,289 @@
+# Synapse 1.114.0rc1 (2024-08-20)
+
+### Features
+
+- Add a flag to `/versions`, `org.matrix.simplified_msc3575`, to indicate whether experimental sliding sync support has been enabled. ([\#17571](https://github.com/element-hq/synapse/issues/17571))
+- Handle changes in `timeline_limit` in experimental sliding sync. ([\#17579](https://github.com/element-hq/synapse/issues/17579))
+- Correctly track read receipts that should be sent down in experimental sliding sync. ([\#17575](https://github.com/element-hq/synapse/issues/17575), [\#17589](https://github.com/element-hq/synapse/issues/17589), [\#17592](https://github.com/element-hq/synapse/issues/17592))
+
+### Bugfixes
+
+- Start handlers for new media endpoints when media resource configured. ([\#17483](https://github.com/element-hq/synapse/issues/17483))
+- Fix timeline ordering (using `stream_ordering` instead of topological ordering) in experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint. ([\#17510](https://github.com/element-hq/synapse/issues/17510))
+- Fix experimental sliding sync implementation to remember any updates in rooms that were not sent down immediately. ([\#17535](https://github.com/element-hq/synapse/issues/17535))
+- Better exclude partially stated rooms if we must await full state in experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint. ([\#17538](https://github.com/element-hq/synapse/issues/17538))
+- Handle lower-case http headers in `_Mulitpart_Parser_Protocol`. ([\#17545](https://github.com/element-hq/synapse/issues/17545))
+- Fix fetching federation signing keys from servers that omit `old_verify_keys`. Contributed by @tulir @ Beeper. ([\#17568](https://github.com/element-hq/synapse/issues/17568))
+- Fix bug where we would respond with an error when a remote server asked for media that had a length of 0, using the new multipart federation media endpoint. ([\#17570](https://github.com/element-hq/synapse/issues/17570))
+
+### Improved Documentation
+
+- Clarify default behaviour of the
+  [`auto_accept_invites.worker_to_run_on`](https://element-hq.github.io/synapse/develop/usage/configuration/config_documentation.html#auto-accept-invites)
+  option. ([\#17515](https://github.com/element-hq/synapse/issues/17515))
+- Improve docstrings for profile methods. ([\#17559](https://github.com/element-hq/synapse/issues/17559))
+
+### Internal Changes
+
+- Add more tracing to experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint. ([\#17514](https://github.com/element-hq/synapse/issues/17514))
+- Fixup comment in sliding sync implementation. ([\#17531](https://github.com/element-hq/synapse/issues/17531))
+- Replace override of deprecated method `HTTPAdapter.get_connection` with `get_connection_with_tls_context`. ([\#17536](https://github.com/element-hq/synapse/issues/17536))
+- Fix performance of device lists in `/key/changes` and sliding sync. ([\#17537](https://github.com/element-hq/synapse/issues/17537), [\#17548](https://github.com/element-hq/synapse/issues/17548))
+- Bump setuptools from 67.6.0 to 72.1.0. ([\#17542](https://github.com/element-hq/synapse/issues/17542))
+- Add a utility function for generating random event IDs. ([\#17557](https://github.com/element-hq/synapse/issues/17557))
+- Speed up responding to media requests. ([\#17558](https://github.com/element-hq/synapse/issues/17558), [\#17561](https://github.com/element-hq/synapse/issues/17561), [\#17564](https://github.com/element-hq/synapse/issues/17564), [\#17566](https://github.com/element-hq/synapse/issues/17566), [\#17567](https://github.com/element-hq/synapse/issues/17567), [\#17569](https://github.com/element-hq/synapse/issues/17569))
+- Test github token before running release script steps. ([\#17562](https://github.com/element-hq/synapse/issues/17562))
+- Reduce log spam of multipart files. ([\#17563](https://github.com/element-hq/synapse/issues/17563))
+- Refactor per-connection state in experimental sliding sync handler. ([\#17574](https://github.com/element-hq/synapse/issues/17574))
+- Add histogram metrics for sliding sync processing time. ([\#17593](https://github.com/element-hq/synapse/issues/17593))
+
+
+
+### Updates to locked dependencies
+
+* Bump bytes from 1.6.1 to 1.7.1. ([\#17526](https://github.com/element-hq/synapse/issues/17526))
+* Bump lxml from 5.2.2 to 5.3.0. ([\#17550](https://github.com/element-hq/synapse/issues/17550))
+* Bump phonenumbers from 8.13.42 to 8.13.43. ([\#17551](https://github.com/element-hq/synapse/issues/17551))
+* Bump regex from 1.10.5 to 1.10.6. ([\#17527](https://github.com/element-hq/synapse/issues/17527))
+* Bump sentry-sdk from 2.10.0 to 2.12.0. ([\#17553](https://github.com/element-hq/synapse/issues/17553))
+* Bump serde from 1.0.204 to 1.0.206. ([\#17556](https://github.com/element-hq/synapse/issues/17556))
+* Bump serde_json from 1.0.122 to 1.0.124. ([\#17555](https://github.com/element-hq/synapse/issues/17555))
+* Bump sigstore/cosign-installer from 3.5.0 to 3.6.0. ([\#17549](https://github.com/element-hq/synapse/issues/17549))
+* Bump types-pyyaml from 6.0.12.20240311 to 6.0.12.20240808. ([\#17552](https://github.com/element-hq/synapse/issues/17552))
+* Bump types-requests from 2.31.0.20240406 to 2.32.0.20240712. ([\#17524](https://github.com/element-hq/synapse/issues/17524))
+
+# Synapse 1.113.0 (2024-08-13)
+
+No significant changes since 1.113.0rc1.
+
+
+
+
+# Synapse 1.113.0rc1 (2024-08-06)
+
+### Features
+
+- Track which rooms have been sent to clients in the experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint. ([\#17447](https://github.com/element-hq/synapse/issues/17447))
+- Add Account Data extension support to experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint. ([\#17477](https://github.com/element-hq/synapse/issues/17477))
+- Add receipts extension support to experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint. ([\#17489](https://github.com/element-hq/synapse/issues/17489))
+- Add typing notification extension support to experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint. ([\#17505](https://github.com/element-hq/synapse/issues/17505))
+
+### Bugfixes
+
+- Update experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint to handle invite/knock rooms when filtering. ([\#17450](https://github.com/element-hq/synapse/issues/17450))
+- Fix a bug introduced in v1.110.0 which caused `/keys/query` to return incomplete results, leading to high network activity and CPU usage on Matrix clients. ([\#17499](https://github.com/element-hq/synapse/issues/17499))
+
+### Improved Documentation
+
+- Update the [`allowed_local_3pids`](https://element-hq.github.io/synapse/v1.112/usage/configuration/config_documentation.html#allowed_local_3pids) config option's msisdn address to a working example. ([\#17476](https://github.com/element-hq/synapse/issues/17476))
+
+### Internal Changes
+
+- Change sliding sync to use their own token format in preparation for storing per-connection state. ([\#17452](https://github.com/element-hq/synapse/issues/17452))
+- Ensure we don't send down negative `bump_stamp` in experimental sliding sync endpoint. ([\#17478](https://github.com/element-hq/synapse/issues/17478))
+- Do not send down empty room entries down experimental sliding sync endpoint. ([\#17479](https://github.com/element-hq/synapse/issues/17479))
+- Refactor Sliding Sync tests to better utilize the `SlidingSyncBase`. ([\#17481](https://github.com/element-hq/synapse/issues/17481), [\#17482](https://github.com/element-hq/synapse/issues/17482))
+- Add some opentracing tags and logging to the experimental sliding sync implementation. ([\#17501](https://github.com/element-hq/synapse/issues/17501))
+- Split and move Sliding Sync tests so we have some more sane test file sizes. ([\#17504](https://github.com/element-hq/synapse/issues/17504))
+- Update the `limited` field description in the Sliding Sync response to accurately describe what it actually represents. ([\#17507](https://github.com/element-hq/synapse/issues/17507))
+- Easier to understand `timeline` assertions in Sliding Sync tests. ([\#17511](https://github.com/element-hq/synapse/issues/17511))
+- Reset the sliding sync connection if we don't recognize the per-connection state position. ([\#17529](https://github.com/element-hq/synapse/issues/17529))
+
+
+
+### Updates to locked dependencies
+
+* Bump bcrypt from 4.1.3 to 4.2.0. ([\#17495](https://github.com/element-hq/synapse/issues/17495))
+* Bump black from 24.4.2 to 24.8.0. ([\#17522](https://github.com/element-hq/synapse/issues/17522))
+* Bump phonenumbers from 8.13.39 to 8.13.42. ([\#17521](https://github.com/element-hq/synapse/issues/17521))
+* Bump ruff from 0.5.4 to 0.5.5. ([\#17494](https://github.com/element-hq/synapse/issues/17494))
+* Bump serde_json from 1.0.120 to 1.0.121. ([\#17493](https://github.com/element-hq/synapse/issues/17493))
+* Bump serde_json from 1.0.121 to 1.0.122. ([\#17525](https://github.com/element-hq/synapse/issues/17525))
+* Bump towncrier from 23.11.0 to 24.7.1. ([\#17523](https://github.com/element-hq/synapse/issues/17523))
+* Bump types-pyopenssl from 24.1.0.20240425 to 24.1.0.20240722. ([\#17496](https://github.com/element-hq/synapse/issues/17496))
+* Bump types-setuptools from 70.1.0.20240627 to 71.1.0.20240726. ([\#17497](https://github.com/element-hq/synapse/issues/17497))
+
+# Synapse 1.112.0 (2024-07-30)
+
+This security release is to update our locked dependency on Twisted to 24.7.0rc1, which includes a security fix for [CVE-2024-41671 / GHSA-c8m8-j448-xjx7: Disordered HTTP pipeline response in twisted.web, again](https://github.com/twisted/twisted/security/advisories/GHSA-c8m8-j448-xjx7).
+
+Note that this security fix is also available as **Synapse 1.111.1**, which does not include the rest of the changes in Synapse 1.112.0.
+
+This issue means that, if multiple HTTP requests are pipelined in the same TCP connection, Synapse can send responses to the wrong HTTP request.
+If a reverse proxy was configured to use HTTP pipelining, this could result in responses being sent to the wrong user, severely harming confidentiality.
+
+With that said, despite being a high severity issue, **we consider it unlikely that Synapse installations will be affected**.
+The use of HTTP pipelining in this fashion would cause worse performance for clients (request-response latencies would be increased as users' responses would be artificially blocked behind other users' slow requests). Further, Nginx and Haproxy, two common reverse proxies, do not appear to support configuring their upstreams to use HTTP pipelining and thus would not be affected. For both of these reasons, we consider it unlikely that a Synapse deployment would be set up in such a configuration.
+
+Despite that, we cannot rule out that some installations may exist with this unusual setup and so we are releasing this security update today.
+
+**pip users:** Note that by default, upgrading Synapse using pip will not automatically upgrade Twisted. **Please manually install the new version of Twisted** using `pip install Twisted==24.7.0rc1`. Note also that even the `--upgrade-strategy=eager` flag to `pip install -U matrix-synapse` will not upgrade Twisted to a patched version because it is only a release candidate at this time.
+
+### Internal Changes
+
+- Upgrade locked dependency on Twisted to 24.7.0rc1. ([\#17502](https://github.com/element-hq/synapse/issues/17502))
+
+
+# Synapse 1.112.0rc1 (2024-07-23)
+
+Please note that this release candidate does not include the security dependency update
+included in version 1.111.1 as this version was released before 1.111.1.
+The same security fix can be found in the full release of 1.112.0.
+
+### Features
+
+- Add to-device extension support to experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint. ([\#17416](https://github.com/element-hq/synapse/issues/17416))
+- Populate `name`/`avatar` fields in experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint. ([\#17418](https://github.com/element-hq/synapse/issues/17418))
+- Populate `heroes` and room summary fields (`joined_count`, `invited_count`) in experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint. ([\#17419](https://github.com/element-hq/synapse/issues/17419))
+- Populate `is_dm` room field in experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint. ([\#17429](https://github.com/element-hq/synapse/issues/17429))
+- Add room subscriptions to experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint. ([\#17432](https://github.com/element-hq/synapse/issues/17432))
+- Prepare for authenticated media freeze. ([\#17433](https://github.com/element-hq/synapse/issues/17433))
+- Add E2EE extension support to experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint. ([\#17454](https://github.com/element-hq/synapse/issues/17454))
+
+### Bugfixes
+
+- Add configurable option to always include offline users in presence sync results. Contributed by @Michael-Hollister. ([\#17231](https://github.com/element-hq/synapse/issues/17231))
+- Fix bug in experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint when using room type filters and the user has one or more remote invites. ([\#17434](https://github.com/element-hq/synapse/issues/17434))
+- Order `heroes` by `stream_ordering` as the Matrix specification states (applies to `/sync`). ([\#17435](https://github.com/element-hq/synapse/issues/17435))
+- Fix rare bug where `/sync` would break for a user when using workers with multiple stream writers. ([\#17438](https://github.com/element-hq/synapse/issues/17438))
+
+### Improved Documentation
+
+- Update the readme image to have a white background, so that it is readable in dark mode. ([\#17387](https://github.com/element-hq/synapse/issues/17387))
+- Add Red Hat Enterprise Linux and Rocky Linux 8 and 9 installation instructions. ([\#17423](https://github.com/element-hq/synapse/issues/17423))
+- Improve documentation for the [`default_power_level_content_override`](https://element-hq.github.io/synapse/latest/usage/configuration/config_documentation.html#default_power_level_content_override) config option. ([\#17451](https://github.com/element-hq/synapse/issues/17451))
+
+### Internal Changes
+
+- Make sure we always use the right logic for enabling the media repo. ([\#17424](https://github.com/element-hq/synapse/issues/17424))
+- Fix argument documentation for method `RateLimiter.record_action`. ([\#17426](https://github.com/element-hq/synapse/issues/17426))
+- Reduce volume of 'Waiting for current token' logs, which were introduced in v1.109.0. ([\#17428](https://github.com/element-hq/synapse/issues/17428))
+- Limit concurrent remote downloads to 6 per IP address, and decrement remote downloads without a content-length from the ratelimiter after the download is complete. ([\#17439](https://github.com/element-hq/synapse/issues/17439))
+- Remove unnecessary call to resume producing in fake channel. ([\#17449](https://github.com/element-hq/synapse/issues/17449))
+- Update experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint to bump room when it is created. ([\#17453](https://github.com/element-hq/synapse/issues/17453))
+- Speed up generating sliding sync responses. ([\#17458](https://github.com/element-hq/synapse/issues/17458))
+- Add cache to `get_rooms_for_local_user_where_membership_is` to speed up sliding sync. ([\#17460](https://github.com/element-hq/synapse/issues/17460))
+- Speed up fetching room keys from backup. ([\#17461](https://github.com/element-hq/synapse/issues/17461))
+- Speed up sorting of the room list in sliding sync. ([\#17468](https://github.com/element-hq/synapse/issues/17468))
+- Implement handling of `$ME` as a state key in sliding sync. ([\#17469](https://github.com/element-hq/synapse/issues/17469))
+
+
+
+### Updates to locked dependencies
+
+* Bump bytes from 1.6.0 to 1.6.1. ([\#17441](https://github.com/element-hq/synapse/issues/17441))
+* Bump hiredis from 2.3.2 to 3.0.0. ([\#17464](https://github.com/element-hq/synapse/issues/17464))
+* Bump jsonschema from 4.22.0 to 4.23.0. ([\#17444](https://github.com/element-hq/synapse/issues/17444))
+* Bump matrix-org/done-action from 2 to 3. ([\#17440](https://github.com/element-hq/synapse/issues/17440))
+* Bump mypy from 1.9.0 to 1.10.1. ([\#17445](https://github.com/element-hq/synapse/issues/17445))
+* Bump pyopenssl from 24.1.0 to 24.2.1. ([\#17465](https://github.com/element-hq/synapse/issues/17465))
+* Bump ruff from 0.5.0 to 0.5.4. ([\#17466](https://github.com/element-hq/synapse/issues/17466))
+* Bump sentry-sdk from 2.6.0 to 2.8.0. ([\#17456](https://github.com/element-hq/synapse/issues/17456))
+* Bump sentry-sdk from 2.8.0 to 2.10.0. ([\#17467](https://github.com/element-hq/synapse/issues/17467))
+* Bump setuptools from 67.6.0 to 70.0.0. ([\#17448](https://github.com/element-hq/synapse/issues/17448))
+* Bump twine from 5.1.0 to 5.1.1. ([\#17443](https://github.com/element-hq/synapse/issues/17443))
+* Bump types-jsonschema from 4.22.0.20240610 to 4.23.0.20240712. ([\#17446](https://github.com/element-hq/synapse/issues/17446))
+* Bump ulid from 1.1.2 to 1.1.3. ([\#17442](https://github.com/element-hq/synapse/issues/17442))
+* Bump zipp from 3.15.0 to 3.19.1. ([\#17427](https://github.com/element-hq/synapse/issues/17427))
+
+
+# Synapse 1.111.1 (2024-07-30)
+
+This security release is to update our locked dependency on Twisted to 24.7.0rc1, which includes a security fix for [CVE-2024-41671 / GHSA-c8m8-j448-xjx7: Disordered HTTP pipeline response in twisted.web, again](https://github.com/twisted/twisted/security/advisories/GHSA-c8m8-j448-xjx7).
+
+This issue means that, if multiple HTTP requests are pipelined in the same TCP connection, Synapse can send responses to the wrong HTTP request.
+If a reverse proxy was configured to use HTTP pipelining, this could result in responses being sent to the wrong user, severely harming confidentiality.
+
+With that said, despite being a high severity issue, **we consider it unlikely that Synapse installations will be affected**.
+The use of HTTP pipelining in this fashion would cause worse performance for clients (request-response latencies would be increased as users' responses would be artificially blocked behind other users' slow requests). Further, Nginx and Haproxy, two common reverse proxies, do not appear to support configuring their upstreams to use HTTP pipelining and thus would not be affected. For both of these reasons, we consider it unlikely that a Synapse deployment would be set up in such a configuration.
+
+Despite that, we cannot rule out that some installations may exist with this unusual setup and so we are releasing this security update today.
+
+**pip users:** Note that by default, upgrading Synapse using pip will not automatically upgrade Twisted. **Please manually install the new version of Twisted** using `pip install Twisted==24.7.0rc1`. Note also that even the `--upgrade-strategy=eager` flag to `pip install -U matrix-synapse` will not upgrade Twisted to a patched version because it is only a release candidate at this time.
+
+
+### Internal Changes
+
+- Upgrade locked dependency on Twisted to 24.7.0rc1. ([\#17502](https://github.com/element-hq/synapse/issues/17502))
+
+
+# Synapse 1.111.0 (2024-07-16)
+
+No significant changes since 1.111.0rc2.
+
+
+
+
+# Synapse 1.111.0rc2 (2024-07-10)
+
+### Bugfixes
+
+- Fix bug where using `synapse.app.media_repository` worker configuration would break the new media endpoints. ([\#17420](https://github.com/element-hq/synapse/issues/17420))
+
+### Improved Documentation
+
+- Document the new federation media worker endpoints in the [upgrade notes](https://element-hq.github.io/synapse/v1.111/upgrade.html) and [worker docs](https://element-hq.github.io/synapse/v1.111/workers.html). ([\#17421](https://github.com/element-hq/synapse/issues/17421))
+
+### Internal Changes
+
+- Route authenticated federation media requests to media repository workers in Complement tests. ([\#17422](https://github.com/element-hq/synapse/issues/17422))
+
+
+
+
+# Synapse 1.111.0rc1 (2024-07-09)
+
+### Features
+
+- Add `rooms` data to experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint. ([\#17320](https://github.com/element-hq/synapse/issues/17320))
+- Add `room_types`/`not_room_types` filtering to experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint. ([\#17337](https://github.com/element-hq/synapse/issues/17337))
+- Return "required state" in experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint. ([\#17342](https://github.com/element-hq/synapse/issues/17342))
+- Support [MSC3916](https://github.com/matrix-org/matrix-spec-proposals/blob/main/proposals/3916-authentication-for-media.md) by adding [`_matrix/client/v1/media/download`](https://spec.matrix.org/v1.11/client-server-api/#get_matrixclientv1mediadownloadservernamemediaid) endpoint. ([\#17365](https://github.com/element-hq/synapse/issues/17365))
+- Support [MSC3916](https://github.com/matrix-org/matrix-spec-proposals/blob/rav/authentication-for-media/proposals/3916-authentication-for-media.md)
+  by adding [`_matrix/client/v1/media/thumbnail`](https://spec.matrix.org/v1.11/client-server-api/#get_matrixclientv1mediathumbnailservernamemediaid), [`_matrix/federation/v1/media/thumbnail`](https://spec.matrix.org/v1.11/server-server-api/#get_matrixfederationv1mediathumbnailmediaid) endpoints and stabilizing the
+  remaining [`_matrix/client/v1/media`](https://spec.matrix.org/v1.11/client-server-api/#get_matrixclientv1mediaconfig) endpoints. ([\#17388](https://github.com/element-hq/synapse/issues/17388))
+- Add `rooms.bump_stamp` for easier client-side sorting in experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint. ([\#17395](https://github.com/element-hq/synapse/issues/17395))
+- Forget all of a user's rooms upon deactivation, preventing local room purges from being blocked on deactivated users. ([\#17400](https://github.com/element-hq/synapse/issues/17400))
+- Declare support for [Matrix 1.11](https://matrix.org/blog/2024/06/20/matrix-v1.11-release/). ([\#17403](https://github.com/element-hq/synapse/issues/17403))
+- [MSC3861](https://github.com/matrix-org/matrix-spec-proposals/pull/3861): allow overriding the introspection endpoint. ([\#17406](https://github.com/element-hq/synapse/issues/17406))
+
+### Bugfixes
+
+- Fix rare race which caused no new to-device messages to be received from remote server. ([\#17362](https://github.com/element-hq/synapse/issues/17362))
+- Fix bug in experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint when using an old database. ([\#17398](https://github.com/element-hq/synapse/issues/17398))
+
+### Improved Documentation
+
+- Clarify that `url_preview_url_blacklist` is a usability feature. ([\#17356](https://github.com/element-hq/synapse/issues/17356))
+- Fix broken links in README. ([\#17379](https://github.com/element-hq/synapse/issues/17379))
+- Clarify that changelog content *and file extension* need to match in order for entries to merge. ([\#17399](https://github.com/element-hq/synapse/issues/17399))
+
+### Internal Changes
+
+- Make the release script create a release branch for Complement as well. ([\#17318](https://github.com/element-hq/synapse/issues/17318))
+- Fix uploading packages to PyPi. ([\#17363](https://github.com/element-hq/synapse/issues/17363))
+- Add CI check for the README. ([\#17367](https://github.com/element-hq/synapse/issues/17367))
+- Fix linting errors from new `ruff` version. ([\#17381](https://github.com/element-hq/synapse/issues/17381), [\#17411](https://github.com/element-hq/synapse/issues/17411))
+- Fix building debian packages on non-clean checkouts. ([\#17390](https://github.com/element-hq/synapse/issues/17390))
+- Finish up work to allow per-user feature flags. ([\#17392](https://github.com/element-hq/synapse/issues/17392), [\#17410](https://github.com/element-hq/synapse/issues/17410))
+- Allow enabling sliding sync per-user. ([\#17393](https://github.com/element-hq/synapse/issues/17393))
+
+
+
+### Updates to locked dependencies
+
+* Bump certifi from 2023.7.22 to 2024.7.4. ([\#17404](https://github.com/element-hq/synapse/issues/17404))
+* Bump cryptography from 42.0.7 to 42.0.8. ([\#17382](https://github.com/element-hq/synapse/issues/17382))
+* Bump ijson from 3.2.3 to 3.3.0. ([\#17413](https://github.com/element-hq/synapse/issues/17413))
+* Bump log from 0.4.21 to 0.4.22. ([\#17384](https://github.com/element-hq/synapse/issues/17384))
+* Bump mypy-zope from 1.0.4 to 1.0.5. ([\#17414](https://github.com/element-hq/synapse/issues/17414))
+* Bump pillow from 10.3.0 to 10.4.0. ([\#17412](https://github.com/element-hq/synapse/issues/17412))
+* Bump pydantic from 2.7.1 to 2.8.2. ([\#17415](https://github.com/element-hq/synapse/issues/17415))
+* Bump ruff from 0.3.7 to 0.5.0. ([\#17381](https://github.com/element-hq/synapse/issues/17381))
+* Bump serde from 1.0.203 to 1.0.204. ([\#17409](https://github.com/element-hq/synapse/issues/17409))
+* Bump serde_json from 1.0.117 to 1.0.120. ([\#17385](https://github.com/element-hq/synapse/issues/17385), [\#17408](https://github.com/element-hq/synapse/issues/17408))
+* Bump types-setuptools from 69.5.0.20240423 to 70.1.0.20240627. ([\#17380](https://github.com/element-hq/synapse/issues/17380))
+
 # Synapse 1.110.0 (2024-07-03)

 No significant changes since 1.110.0rc3.
@@ -48,7 +334,7 @@ No significant changes since 1.110.0rc3.
  This is useful for scripts that bootstrap user accounts with initial passwords. ([\#17304](https://github.com/element-hq/synapse/issues/17304))
 - Add support for via query parameter from [MSC4156](https://github.com/matrix-org/matrix-spec-proposals/pull/4156). ([\#17322](https://github.com/element-hq/synapse/issues/17322))
 - Add `is_invite` filtering to experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint. ([\#17335](https://github.com/element-hq/synapse/issues/17335))
- Support [MSC3916](https://github.com/matrix-org/matrix-spec-proposals/blob/rav/authentication-for-media/proposals/3916-authentication-for-media.md) by adding a federation /download endpoint. ([\#17350](https://github.com/element-hq/synapse/issues/17350))
+- Support [MSC3916](https://github.com/matrix-org/matrix-spec-proposals/blob/main/proposals/3916-authentication-for-media.md) by adding a federation /download endpoint. ([\#17350](https://github.com/element-hq/synapse/issues/17350))

 ### Bugfixes

@@ -67,9 +67,9 @@ checksum = "79296716171880943b8470b5f8d03aa55eb2e645a4874bdbb28adb49162e012c"

 [[package]]
 name = "bytes"
-version = "1.6.0"
+version = "1.7.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "514de17de45fdb8dc022b1a7975556c53c86f9f0aa5f534b98977b171857c2c9"
+checksum = "8318a53db07bb3f8dca91a600466bdb3f2eaadeedfdbcf02e1accbad9271ba50"

 [[package]]
 name = "cfg-if"
@@ -444,9 +444,9 @@ dependencies = [

 [[package]]
 name = "regex"
-version = "1.10.5"
+version = "1.10.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b91213439dad192326a0d7c6ee3955910425f441d7038e0d6933b0aec5c4517f"
+checksum = "4219d74c6b67a3654a9fbebc4b419e22126d13d2f3c4a07ee0cb61ff79a79619"
 dependencies = [
 "aho-corasick",
 "memchr",
@@ -485,18 +485,18 @@ checksum = "94143f37725109f92c262ed2cf5e59bce7498c01bcc1502d7b9afe439a4e9f49"

 [[package]]
 name = "serde"
-version = "1.0.203"
+version = "1.0.208"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7253ab4de971e72fb7be983802300c30b5a7f0c2e56fab8abfc6a214307c0094"
+checksum = "cff085d2cb684faa248efb494c39b68e522822ac0de72ccf08109abde717cfb2"
 dependencies = [
 "serde_derive",
 ]

 [[package]]
 name = "serde_derive"
-version = "1.0.203"
+version = "1.0.208"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "500cbc0ebeb6f46627f50f3f5811ccf6bf00643be300b4c3eabc0ef55dc5b5ba"
+checksum = "24008e81ff7613ed8e5ba0cfaf24e2c2f1e5b8a0495711e44fcd4882fca62bcf"
 dependencies = [
 "proc-macro2",
 "quote",
@@ -505,11 +505,12 @@ dependencies = [

 [[package]]
 name = "serde_json"
-version = "1.0.119"
+version = "1.0.125"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e8eddb61f0697cc3989c5d64b452f5488e2b8a60fd7d5076a3045076ffef8cb0"
+checksum = "83c8e735a073ccf5be70aa8066aa984eaf2fa000db6c8d0100ae605b366d31ed"
 dependencies = [
 "itoa",
+ "memchr",
 "ryu",
 "serde",
 ]
@@ -597,9 +598,9 @@ checksum = "42ff0bf0c66b8238c6f3b578df37d0b7848e55df8577b3f74f92a69acceeb825"

 [[package]]
 name = "ulid"
-version = "1.1.2"
+version = "1.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "34778c17965aa2a08913b57e1f34db9b4a63f5de31768b55bf20d2795f921259"
+checksum = "04f903f293d11f31c0c29e4148f6dc0d033a7f80cebc0282bea147611667d289"
 dependencies = [
 "getrandom",
 "rand",
@@ -1,4 +1,4 @@
-.. image:: https://github.com/element-hq/product/assets/87339233/7abf477a-5277-47f3-be44-ea44917d8ed7
+.. image:: ./docs/element_logo_white_bg.svg
   :height: 60px

 **Element Synapse - Matrix homeserver implementation**
@@ -179,10 +179,10 @@ desired ``localpart`` in the 'User name' box.
 -----------------------

 Enterprise quality support for Synapse including SLAs is available as part of an
-`Element Server Suite (ESS) <https://element.io/pricing>` subscription.
+`Element Server Suite (ESS) <https://element.io/pricing>`_ subscription.

-If you are an existing ESS subscriber then you can raise a `support request <https://ems.element.io/support>`
-and access the `knowledge base <https://ems-docs.element.io>`.
+If you are an existing ESS subscriber then you can raise a `support request <https://ems.element.io/support>`_
+and access the `knowledge base <https://ems-docs.element.io>`_.

 🤝 Community support
 --------------------
@@ -1 +0,0 @@
-Add `rooms` data to experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint.
@@ -1 +0,0 @@
-Add `room_types`/`not_room_types` filtering to experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint.
@@ -1 +0,0 @@
-Clarify `url_preview_url_blacklist` is a usability feature.
@@ -1 +0,0 @@
-Fix rare race which causes no new to-device messages to be received from remote server.
@@ -1 +0,0 @@
-Fix uploading packages to PyPi.
@@ -1 +0,0 @@
-Support [MSC3916](https://github.com/matrix-org/matrix-spec-proposals/blob/rav/authentication-for-media/proposals/3916-authentication-for-media.md) by adding _matrix/client/v1/media/download endpoint.
@@ -1 +0,0 @@
-Add CI check for the README.
@@ -1 +0,0 @@
-Fix building debian packages on non-clean checkouts.
@@ -1 +0,0 @@
-Pin CI to complement release branch for releases.
@@ -0,0 +1 @@
+Pre-populate room data used in experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint for quick filtering/sorting.
@@ -0,0 +1 @@
+Refactor sliding sync class into multiple files.
@@ -0,0 +1 @@
+Store sliding sync per-connection state in the database.
@@ -0,0 +1 @@
+Make the sliding sync `PerConnectionState` class immutable.
@@ -1,3 +1,57 @@
+matrix-synapse-py3 (1.114.0~rc1) stable; urgency=medium
+
+  * New synapse release 1.114.0rc1.
+
+ -- Synapse Packaging team <packages@matrix.org>  Tue, 20 Aug 2024 12:55:28 +0000
+
+matrix-synapse-py3 (1.113.0) stable; urgency=medium
+
+  * New Synapse release 1.113.0.
+
+ -- Synapse Packaging team <packages@matrix.org>  Tue, 13 Aug 2024 14:36:56 +0100
+
+matrix-synapse-py3 (1.113.0~rc1) stable; urgency=medium
+
+  * New Synapse release 1.113.0rc1.
+
+ -- Synapse Packaging team <packages@matrix.org>  Tue, 06 Aug 2024 12:23:23 +0100
+
+matrix-synapse-py3 (1.112.0) stable; urgency=medium
+
+  * New Synapse release 1.112.0.
+
+ -- Synapse Packaging team <packages@matrix.org>  Tue, 30 Jul 2024 17:15:48 +0100
+
+matrix-synapse-py3 (1.112.0~rc1) stable; urgency=medium
+
+  * New Synapse release 1.112.0rc1.
+
+ -- Synapse Packaging team <packages@matrix.org>  Tue, 23 Jul 2024 08:58:55 -0600
+
+matrix-synapse-py3 (1.111.1) stable; urgency=medium
+
+  * New Synapse release 1.111.1.
+
+ -- Synapse Packaging team <packages@matrix.org>  Tue, 30 Jul 2024 16:13:52 +0100
+
+matrix-synapse-py3 (1.111.0) stable; urgency=medium
+
+  * New Synapse release 1.111.0.
+
+ -- Synapse Packaging team <packages@matrix.org>  Tue, 16 Jul 2024 12:42:46 +0200
+
+matrix-synapse-py3 (1.111.0~rc2) stable; urgency=medium
+
+  * New synapse release 1.111.0rc2.
+
+ -- Synapse Packaging team <packages@matrix.org>  Wed, 10 Jul 2024 08:46:54 +0000
+
+matrix-synapse-py3 (1.111.0~rc1) stable; urgency=medium
+
+  * New synapse release 1.111.0rc1.
+
+ -- Synapse Packaging team <packages@matrix.org>  Tue, 09 Jul 2024 09:49:25 +0000
+
 matrix-synapse-py3 (1.110.0) stable; urgency=medium

  * New Synapse release 1.110.0.
@@ -5,7 +5,7 @@ _Description: Name of the server:
 servers via federation. This is normally the public hostname of the
 server running synapse, but can be different if you set up delegation.
 Please refer to the delegation documentation in this case:
- https://github.com/element-hq/synapse/blob/master/docs/delegate.md.
+ https://element-hq.github.io/synapse/latest/delegate.html.

 Template: matrix-synapse/report-stats
 Type: boolean
@@ -27,7 +27,7 @@ ARG PYTHON_VERSION=3.11
 ###
 # We hardcode the use of Debian bookworm here because this could change upstream
 # and other Dockerfiles used for testing are expecting bookworm.
-FROM docker.io/library/python:${PYTHON_VERSION}-slim-bookworm as requirements
+FROM docker.io/library/python:${PYTHON_VERSION}-slim-bookworm AS requirements

 # RUN --mount is specific to buildkit and is documented at
 # https://github.com/moby/buildkit/blob/master/frontend/dockerfile/docs/syntax.md#build-mounts-run---mount.
@@ -87,7 +87,7 @@ RUN if [ -z "$TEST_ONLY_IGNORE_POETRY_LOCKFILE" ]; then \
 ###
 ### Stage 1: builder
 ###
-FROM docker.io/library/python:${PYTHON_VERSION}-slim-bookworm as builder
+FROM docker.io/library/python:${PYTHON_VERSION}-slim-bookworm AS builder

 # install the OS build deps
 RUN \
@@ -24,7 +24,7 @@ ARG distro=""
 # https://launchpad.net/~jyrki-pulliainen/+archive/ubuntu/dh-virtualenv, but
 # it's not obviously easier to use that than to build our own.)

-FROM docker.io/library/${distro} as builder
+FROM docker.io/library/${distro} AS builder

 RUN apt-get update -qq -o Acquire::Languages=none
 RUN env DEBIAN_FRONTEND=noninteractive apt-get install \
@@ -126,6 +126,7 @@ WORKERS_CONFIG: Dict[str, Dict[str, Any]] = {
            "^/_synapse/admin/v1/media/.*$",
            "^/_synapse/admin/v1/quarantine_media/.*$",
            "^/_matrix/client/v1/media/.*$",
+            "^/_matrix/federation/v1/media/.*$",
        ],
        # The first configured media worker will run the media background jobs
        "shared_extra_conf": {
@@ -1,21 +1,17 @@
 # Experimental Features API

 This API allows a server administrator to enable or disable some experimental features on a per-user
-basis. The currently supported features are: 
- [MSC3026](https://github.com/matrix-org/matrix-spec-proposals/pull/3026): busy 
-presence state enabled
- [MSC3881](https://github.com/matrix-org/matrix-spec-proposals/pull/3881): enable remotely toggling push notifications 
-for another client 
- [MSC3967](https://github.com/matrix-org/matrix-spec-proposals/pull/3967): do not require
-UIA when first uploading cross-signing keys. 
-
+basis. The currently supported features are:
+- [MSC3881](https://github.com/matrix-org/matrix-spec-proposals/pull/3881): enable remotely toggling push notifications
+for another client
+- [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575): enable experimental sliding sync support

 To use it, you will need to authenticate by providing an `access_token`
 for a server admin: see [Admin API](../usage/administration/admin_api/).

 ## Enabling/Disabling Features

-This API allows a server administrator to enable experimental features for a given user. The request must 
+This API allows a server administrator to enable experimental features for a given user. The request must
 provide a body containing the user id and listing the features to enable/disable in the following format:
 ```json
 {
@@ -35,7 +31,7 @@ PUT /_synapse/admin/v1/experimental_features/<user_id>
 ```

 ## Listing Enabled Features
- 
+
 To list which features are enabled/disabled for a given user send a request to the following API:

 ```
@@ -52,4 +48,4 @@ user like so:
      "msc3967": false
   }
 }
-```
+```
@@ -449,9 +449,9 @@ For example, a fix in PR #1234 would have its changelog entry in
 > The security levels of Florbs are now validated when received
 > via the `/federation/florb` endpoint. Contributed by Jane Matrix.

-If there are multiple pull requests involved in a single bugfix/feature/etc,
-then the content for each `changelog.d` file should be the same. Towncrier will
-merge the matching files together into a single changelog entry when we come to
+If there are multiple pull requests involved in a single bugfix/feature/etc, then the
+content for each `changelog.d` file and file extension should be the same. Towncrier
+will merge the matching files together into a single changelog entry when we come to
 release.

 ### How do I know what to call the changelog file before I create the PR?
@@ -21,8 +21,10 @@ incrementing integer, but backfilled events start with `stream_ordering=-1` and

 ---

- - `/sync` returns things in the order they arrive at the server (`stream_ordering`).
- - `/messages` (and `/backfill` in the federation API) return them in the order determined by the event graph `(topological_ordering, stream_ordering)`.
+ - Incremental `/sync?since=xxx` returns things in the order they arrive at the server
+   (`stream_ordering`).
+ - Initial `/sync`, `/messages` (and `/backfill` in the federation API) return them in
+   the order determined by the event graph `(topological_ordering, stream_ordering)`.

 The general idea is that, if you're following a room in real-time (i.e.
 `/sync`), you probably want to see the messages as they arrive at your server,
@@ -0,0 +1,94 @@
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+<!-- Created with Inkscape (http://www.inkscape.org/) -->
+
+<svg
+   width="41.440346mm"
+   height="10.383124mm"
+   viewBox="0 0 41.440346 10.383125"
+   version="1.1"
+   id="svg1"
+   xml:space="preserve"
+   sodipodi:docname="element_logo_white_bg.svg"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:svg="http://www.w3.org/2000/svg"><sodipodi:namedview
+     id="namedview1"
+     pagecolor="#ffffff"
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+     inkscape:showpageshadow="2"
+     inkscape:pageopacity="0.0"
+     inkscape:pagecheckerboard="0"
+     inkscape:deskcolor="#d1d1d1"
+     inkscape:document-units="mm"
+     showgrid="false"
+     inkscape:export-bgcolor="#ffffffff" /><defs
+     id="defs1" /><g
+     id="layer1"
+     transform="translate(-84.803844,-143.2075)"
+     inkscape:export-filename="element_logo_white_bg.svg"
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+     inkscape:export-ydpi="96"><g
+       style="fill:none"
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@@ -67,7 +67,7 @@ in Synapse can be deactivated.
 **NOTE**: This has an impact on security and is for testing purposes only!

 To deactivate the certificate validation, the following setting must be added to
-your [homserver.yaml](../usage/configuration/homeserver_sample_config.md).
+your [homeserver.yaml](../usage/configuration/homeserver_sample_config.md).

 ```yaml
 use_insecure_ssl_client_just_for_testing_do_not_use: true
@@ -309,7 +309,62 @@ sudo dnf install libtiff-devel libjpeg-devel libzip-devel freetype-devel \
                 libwebp-devel libxml2-devel libxslt-devel libpq-devel \
                 python3-virtualenv libffi-devel openssl-devel python3-devel \
                 libicu-devel
-sudo dnf groupinstall "Development Tools"
+sudo dnf group install "Development Tools"
+```
+
+##### Red Hat Enterprise Linux / Rocky Linux
+
+*Note: The term "RHEL" below refers to both Red Hat Enterprise Linux and Rocky Linux. The distributions are 1:1 binary compatible.*
+
+It's recommended to use the latest Python versions. 
+
+RHEL 8 in particular ships with Python 3.6 by default which is EOL and therefore no longer supported by Synapse. RHEL 9 ship with Python 3.9 which is still supported by the Python core team as of this writing. However, newer Python versions provide significant performance improvements and they're available in official distributions' repositories. Therefore it's recommended to use them.
+
+Python 3.11 and 3.12 are available for both RHEL 8 and 9.
+
+These commands should be run as root user.
+
+RHEL 8
+```bash
+# Enable PowerTools repository
+dnf config-manager --set-enabled powertools
+```
+RHEL 9
+```bash
+# Enable CodeReady Linux Builder repository
+crb enable
+```
+
+Install new version of Python. You only need one of these:
+```bash
+# Python 3.11
+dnf install python3.11 python3.11-devel
+```
+```bash
+# Python 3.12
+dnf install python3.12 python3.12-devel
+```
+Finally, install common prerequisites
+```bash
+dnf install libicu libicu-devel libpq5 libpq5-devel lz4 pkgconf 
+dnf group install "Development Tools"
+```
+###### Using venv module instead of virtualenv command
+
+It's recommended to use Python venv module directly rather than the virtualenv command.
+* On RHEL 9, virtualenv is only available on [EPEL](https://docs.fedoraproject.org/en-US/epel/).
+* On RHEL 8, virtualenv is based on Python 3.6. It does not support creating 3.11/3.12 virtual environments.
+
+Here's an example of creating Python 3.12 virtual environment and installing Synapse from PyPI. 
+
+```bash
+mkdir -p ~/synapse
+# To use Python 3.11, simply use the command "python3.11" instead.
+python3.12 -m venv ~/synapse/env
+source ~/synapse/env/bin/activate
+pip install --upgrade pip
+pip install --upgrade setuptools
+pip install matrix-synapse
 ```

 ##### macOS
@@ -119,13 +119,14 @@ stacking them up. You can monitor the currently running background updates with

 # Upgrading to v1.111.0

-## New worker endpoints for authenticated client media
+## New worker endpoints for authenticated client and federation media

 [Media repository workers](./workers.md#synapseappmedia_repository) handling
-Media APIs can now handle the following endpoint pattern:
+Media APIs can now handle the following endpoint patterns:

 ```
 ^/_matrix/client/v1/media/.*$
+^/_matrix/federation/v1/media/.*$
 ```

 Please update your reverse proxy configuration.
@@ -246,6 +246,7 @@ Example configuration:
 ```yaml
 presence:
  enabled: false
+  include_offline_users_on_sync: false
 ```

 `enabled` can also be set to a special value of "untracked" which ignores updates
@@ -254,6 +255,10 @@ received via clients and federation, while still accepting updates from the

 *The "untracked" option was added in Synapse 1.96.0.*

+When clients perform an initial or `full_state` sync, presence results for offline users are
+not included by default. Setting `include_offline_users_on_sync` to `true` will always include
+offline users in the results. Defaults to false.
+
 ---
 ### `require_auth_for_profile_requests`

@@ -1863,6 +1868,18 @@ federation_rr_transactions_per_room_per_second: 40
 ## Media Store
 Config options related to Synapse's media store.

+---
+### `enable_authenticated_media`
+
+When set to true, all subsequent media uploads will be marked as authenticated, and will not be available over legacy
+unauthenticated media endpoints (`/_matrix/media/(r0|v3|v1)/download` and `/_matrix/media/(r0|v3|v1)/thumbnail`) - requests for authenticated media over these endpoints will result in a 404. All media, including authenticated media, will be available over the authenticated media endpoints `_matrix/client/v1/media/download` and `_matrix/client/v1/media/thumbnail`. Media uploaded prior to setting this option to true will still be available over the legacy endpoints. Note if the setting is switched to false
+after enabling, media marked as authenticated will be available over legacy endpoints. Defaults to false, but
+this will change to true in a future Synapse release.
+
+Example configuration:
+```yaml
+enable_authenticated_media: true
+```
 ---
 ### `enable_media_repo`

@@ -2369,7 +2386,7 @@ enable_registration_without_verification: true
 ---
 ### `registrations_require_3pid`

-If this is set, users must provide all of the specified types of 3PID when registering an account.
+If this is set, users must provide all of the specified types of [3PID](https://spec.matrix.org/latest/appendices/#3pid-types) when registering an account.

 Note that [`enable_registration`](#enable_registration) must also be set to allow account registration.

@@ -2394,6 +2411,9 @@ disable_msisdn_registration: true

 Mandate that users are only allowed to associate certain formats of
 3PIDs with accounts on this server, as specified by the `medium` and `pattern` sub-options.
+`pattern` is a [Perl-like regular expression](https://docs.python.org/3/library/re.html#module-re).
+
+More information about 3PIDs, allowed `medium` types and their `address` syntax can be found [in the Matrix spec](https://spec.matrix.org/latest/appendices/#3pid-types).

 Example configuration:
 ```yaml
@@ -2403,7 +2423,7 @@ allowed_local_3pids:
  - medium: email
    pattern: '^[^@]+@vector\.im$'
  - medium: msisdn
-    pattern: '\+44'
+    pattern: '^44\d{10}$'
 ```
 ---
 ### `enable_3pid_lookup`
@@ -4134,6 +4154,38 @@ default_power_level_content_override:
   trusted_private_chat: null
   public_chat: null
 ```
+
+The default power levels for each preset are:
+```yaml
+"m.room.name": 50
+"m.room.power_levels": 100
+"m.room.history_visibility": 100
+"m.room.canonical_alias": 50
+"m.room.avatar": 50
+"m.room.tombstone": 100
+"m.room.server_acl": 100
+"m.room.encryption": 100
+```
+
+So a complete example where the default power-levels for a preset are maintained
+but the power level for a new key is set is:
+```yaml
+default_power_level_content_override:
+   private_chat:
+    events:
+      "com.example.foo": 0
+      "m.room.name": 50
+      "m.room.power_levels": 100
+      "m.room.history_visibility": 100
+      "m.room.canonical_alias": 50
+      "m.room.avatar": 50
+      "m.room.tombstone": 100
+      "m.room.server_acl": 100
+      "m.room.encryption": 100
+   trusted_private_chat: null
+   public_chat: null
+```
+
 ---
 ### `forget_rooms_on_leave`

@@ -4633,7 +4685,9 @@ This setting has the following sub-options:
 * `only_for_direct_messages`: Whether invites should be automatically accepted for all room types, or only
   for direct messages. Defaults to false.
 * `only_from_local_users`: Whether to only automatically accept invites from users on this homeserver. Defaults to false.
-* `worker_to_run_on`: Which worker to run this module on. This must match the "worker_name".
+* `worker_to_run_on`: Which worker to run this module on. This must match 
+  the "worker_name". If not set or `null`, invites will be accepted on the
+  main process.

 NOTE: Care should be taken not to enable this setting if the `synapse_auto_accept_invite` module is enabled and installed.
 The two modules will compete to perform the same task and may result in undesired behaviour. For example, multiple join
@@ -740,6 +740,7 @@ Handles the media repository. It can handle all endpoints starting with:

    /_matrix/media/
    /_matrix/client/v1/media/
+    /_matrix/federation/v1/media/

 ... and the following regular expressions matching media-specific administration APIs:

@@ -43,6 +43,7 @@ target-version = ['py38', 'py39', 'py310', 'py311']
 [tool.ruff]
 line-length = 88

+[tool.ruff.lint]
 # See https://beta.ruff.rs/docs/rules/#error-e
 # for error codes. The ones we ignore are:
 #  E501: Line too long (black enforces this for us)
@@ -96,7 +97,7 @@ module-name = "synapse.synapse_rust"

 [tool.poetry]
 name = "matrix-synapse"
-version = "1.110.0"
+version = "1.114.0rc1"
 description = "Homeserver for the Matrix decentralised comms protocol"
 authors = ["Matrix.org Team and Contributors <packages@matrix.org>"]
 license = "AGPL-3.0-or-later"
@@ -200,8 +201,8 @@ netaddr = ">=0.7.18"
 # add a lower bound to the Jinja2 dependency.
 Jinja2 = ">=3.0"
 bleach = ">=1.4.3"
-# We use `Self`, which were added in `typing-extensions` 4.0.
-typing-extensions = ">=4.0"
+# We use `assert_never`, which were added in `typing-extensions` 4.1.
+typing-extensions = ">=4.1"
 # We enforce that we have a `cryptography` version that bundles an `openssl`
 # with the latest security patches.
 cryptography = ">=3.4.7"
@@ -321,7 +322,7 @@ all = [
 # This helps prevents merge conflicts when running a batch of dependabot updates.
 isort = ">=5.10.1"
 black = ">=22.7.0"
-ruff = "0.3.7"
+ruff = "0.5.5"
 # Type checking only works with the pydantic.v1 compat module from pydantic v2
 pydantic = "^2"

@@ -43,7 +43,7 @@ import argparse
 import base64
 import json
 import sys
-from typing import Any, Dict, Optional, Tuple
+from typing import Any, Dict, Mapping, Optional, Tuple, Union
 from urllib import parse as urlparse

 import requests
@@ -75,7 +75,7 @@ def encode_canonical_json(value: object) -> bytes:
        value,
        # Encode code-points outside of ASCII as UTF-8 rather than \u escapes
        ensure_ascii=False,
-        # Remove unecessary white space.
+        # Remove unnecessary white space.
        separators=(",", ":"),
        # Sort the keys of dictionaries.
        sort_keys=True,
@@ -298,12 +298,23 @@ class MatrixConnectionAdapter(HTTPAdapter):

        return super().send(request, *args, **kwargs)

-    def get_connection(
-        self, url: str, proxies: Optional[Dict[str, str]] = None
+    def get_connection_with_tls_context(
+        self,
+        request: PreparedRequest,
+        verify: Optional[Union[bool, str]],
+        proxies: Optional[Mapping[str, str]] = None,
+        cert: Optional[Union[Tuple[str, str], str]] = None,
    ) -> HTTPConnectionPool:
-        # overrides the get_connection() method in the base class
-        parsed = urlparse.urlsplit(url)
-        (host, port, ssl_server_name) = self._lookup(parsed.netloc)
+        # overrides the get_connection_with_tls_context() method in the base class
+        parsed = urlparse.urlsplit(request.url)
+
+        # Extract the server name from the request URL, and ensure it's a str.
+        hostname = parsed.netloc
+        if isinstance(hostname, bytes):
+            hostname = hostname.decode("utf-8")
+        assert isinstance(hostname, str)
+
+        (host, port, ssl_server_name) = self._lookup(hostname)
        print(
            f"Connecting to {host}:{port} with SNI {ssl_server_name}", file=sys.stderr
        )
@@ -112,7 +112,7 @@ python3 -m black "${files[@]}"

 # Catch any common programming mistakes in Python code.
 # --quiet suppresses the update check.
-ruff --quiet --fix "${files[@]}"
+ruff check --quiet --fix "${files[@]}"

 # Catch any common programming mistakes in Rust code.
 #
@@ -38,6 +38,7 @@ from mypy.types import (
    NoneType,
    TupleType,
    TypeAliasType,
+    TypeVarType,
    UninhabitedType,
    UnionType,
 )
@@ -233,6 +234,7 @@ IMMUTABLE_CUSTOM_TYPES = {
    "synapse.synapse_rust.push.FilteredPushRules",
    # This is technically not immutable, but close enough.
    "signedjson.types.VerifyKey",
+    "synapse.types.StrCollection",
 }

 # Immutable containers only if the values are also immutable.
@@ -298,7 +300,7 @@ def is_cacheable(

        elif rt.type.fullname in MUTABLE_CONTAINER_TYPES:
            # Mutable containers are mutable regardless of their underlying type.
-            return False, None
+            return False, f"container {rt.type.fullname} is mutable"

        elif "attrs" in rt.type.metadata:
            # attrs classes are only cachable iff it is frozen (immutable itself)
@@ -318,6 +320,9 @@ def is_cacheable(
            else:
                return False, "non-frozen attrs class"

+        elif rt.type.is_enum:
+            # We assume Enum values are immutable
+            return True, None
        else:
            # Ensure we fail for unknown types, these generally means that the
            # above code is not complete.
@@ -326,6 +331,18 @@ def is_cacheable(
                f"Don't know how to handle {rt.type.fullname} return type instance",
            )

+    elif isinstance(rt, TypeVarType):
+        # We consider TypeVars immutable if they are bound to a set of immutable
+        # types.
+        if rt.values:
+            for value in rt.values:
+                ok, note = is_cacheable(value, signature, verbose)
+                if not ok:
+                    return False, f"TypeVar bound not cacheable {value}"
+            return True, None
+
+        return False, "TypeVar is unbound"
+
    elif isinstance(rt, NoneType):
        # None is cachable.
        return True, None
@@ -70,7 +70,6 @@ def cli() -> None:
            pip install -e .[dev]

      - A checkout of the sytest repository at ../sytest
-
      - A checkout of the complement repository at ../complement

    Then to use:
@@ -116,7 +115,7 @@ def _prepare() -> None:
    sytest_repo = get_repo_and_check_clean_checkout("../sytest", "sytest")
    complement_repo = get_repo_and_check_clean_checkout("../complement", "complement")

-    click.secho("Updating Synapse, Sytest and Complement git repos...")
+    click.secho("Updating Synapse and Sytest git repos...")
    synapse_repo.remote().fetch()
    sytest_repo.remote().fetch()
    complement_repo.remote().fetch()
@@ -203,28 +202,24 @@ def _prepare() -> None:
        # release type.
        if current_version.is_prerelease:
            default = release_branch_name
-            complement_default = release_branch_name
        elif release_type == "minor":
            default = "develop"
-            complement_default = "main"
        else:
            default = "master"
-            complement_default = "main"

-        sy_branch_name = click.prompt(
+        branch_name = click.prompt(
            "Which branch should the release be based on?", default=default
        )

-        complement_branch = click.prompt(
-            "Which Complement branch should the release be based on?",
-            default=complement_default,
-        )
-
-        for repo_name, (repo, branch_name) in {
-            "synapse": (synapse_repo, sy_branch_name),
-            "sytest": (sytest_repo, sy_branch_name),
-            "complement": (complement_repo, complement_branch),
+        for repo_name, repo in {
+            "synapse": synapse_repo,
+            "sytest": sytest_repo,
+            "complement": complement_repo,
        }.items():
+            # Special case for Complement: `develop` maps to `main`
+            if repo_name == "complement" and branch_name == "develop":
+                branch_name = "main"
+
            base_branch = find_ref(repo, branch_name)
            if not base_branch:
                print(f"Could not find base branch {branch_name} for {repo_name}!")
@@ -246,7 +241,8 @@ def _prepare() -> None:
        # not on subsequent RCs or full releases).
        if click.confirm("Push new SyTest branch?", default=True):
            sytest_repo.git.push("-u", sytest_repo.remote().name, release_branch_name)
-        # The same special case rules apply to Complement.
+
+        # Same for Complement
        if click.confirm("Push new Complement branch?", default=True):
            complement_repo.git.push(
                "-u", complement_repo.remote().name, release_branch_name
@@ -328,6 +324,11 @@ def tag(gh_token: Optional[str]) -> None:
 def _tag(gh_token: Optional[str]) -> None:
    """Tags the release and generates a draft GitHub release"""

+    if gh_token:
+        # Test that the GH Token is valid before continuing.
+        gh = Github(gh_token)
+        gh.get_user()
+
    # Make sure we're in a git repo.
    repo = get_repo_and_check_clean_checkout()

@@ -422,6 +423,11 @@ def publish(gh_token: str) -> None:
 def _publish(gh_token: str) -> None:
    """Publish release on GitHub."""

+    if gh_token:
+        # Test that the GH Token is valid before continuing.
+        gh = Github(gh_token)
+        gh.get_user()
+
    # Make sure we're in a git repo.
    get_repo_and_check_clean_checkout()

@@ -464,6 +470,11 @@ def upload(gh_token: Optional[str]) -> None:
 def _upload(gh_token: Optional[str]) -> None:
    """Upload release to pypi."""

+    if gh_token:
+        # Test that the GH Token is valid before continuing.
+        gh = Github(gh_token)
+        gh.get_user()
+
    current_version = get_package_version()
    tag_name = f"v{current_version}"

@@ -559,6 +570,11 @@ def wait_for_actions(gh_token: Optional[str]) -> None:


 def _wait_for_actions(gh_token: Optional[str]) -> None:
+    if gh_token:
+        # Test that the GH Token is valid before continuing.
+        gh = Github(gh_token)
+        gh.get_user()
+
    # Find out the version and tag name.
    current_version = get_package_version()
    tag_name = f"v{current_version}"
@@ -715,6 +731,11 @@ Ask the designated people to do the blog and tweets."""
@cli.command()
@click.option("--gh-token", envvar=["GH_TOKEN", "GITHUB_TOKEN"], required=True)
 def full(gh_token: str) -> None:
+    if gh_token:
+        # Test that the GH Token is valid before continuing.
+        gh = Github(gh_token)
+        gh.get_user()
+
    click.echo("1. If this is a security release, read the security wiki page.")
    click.echo("2. Check for any release blockers before proceeding.")
    click.echo("    https://github.com/element-hq/synapse/labels/X-Release-Blocker")
@@ -44,7 +44,7 @@ logger = logging.getLogger("generate_workers_map")


 class MockHomeserver(HomeServer):
-    DATASTORE_CLASS = DataStore  # type: ignore
+    DATASTORE_CLASS = DataStore

    def __init__(self, config: HomeServerConfig, worker_app: Optional[str]) -> None:
        super().__init__(config.server.server_name, config=config)
@@ -119,18 +119,24 @@ BOOLEAN_COLUMNS = {
    "e2e_room_keys": ["is_verified"],
    "event_edges": ["is_state"],
    "events": ["processed", "outlier", "contains_url"],
-    "local_media_repository": ["safe_from_quarantine"],
+    "local_media_repository": ["safe_from_quarantine", "authenticated"],
+    "per_user_experimental_features": ["enabled"],
    "presence_list": ["accepted"],
    "presence_stream": ["currently_active"],
    "public_room_list_stream": ["visibility"],
    "pushers": ["enabled"],
    "redactions": ["have_censored"],
+    "remote_media_cache": ["authenticated"],
    "room_stats_state": ["is_federatable"],
    "rooms": ["is_public", "has_auth_chain_index"],
+    "sliding_sync_joined_rooms": ["is_encrypted"],
+    "sliding_sync_membership_snapshots": [
+        "has_known_state",
+        "is_encrypted",
+    ],
    "users": ["shadow_banned", "approved", "locked", "suspended"],
    "un_partial_stated_event_stream": ["rejection_status_changed"],
    "users_who_share_rooms": ["share_private"],
-    "per_user_experimental_features": ["enabled"],
 }


@@ -41,7 +41,7 @@ logger = logging.getLogger("update_database")


 class MockHomeserver(HomeServer):
-    DATASTORE_CLASS = DataStore  # type: ignore [assignment]
+    DATASTORE_CLASS = DataStore

    def __init__(self, config: HomeServerConfig):
        super().__init__(
@@ -18,7 +18,7 @@
 # [This file includes modifications made by New Vector Limited]
 #
 #
-from typing import Optional, Tuple
+from typing import TYPE_CHECKING, Optional, Tuple

 from typing_extensions import Protocol

@@ -28,6 +28,9 @@ from synapse.appservice import ApplicationService
 from synapse.http.site import SynapseRequest
 from synapse.types import Requester

+if TYPE_CHECKING:
+    from synapse.rest.admin.experimental_features import ExperimentalFeature
+
 # guests always get this device id.
 GUEST_DEVICE_ID = "guest_device"

@@ -87,6 +90,19 @@ class Auth(Protocol):
            AuthError if access is denied for the user in the access token
        """

+    async def get_user_by_req_experimental_feature(
+        self,
+        request: SynapseRequest,
+        feature: "ExperimentalFeature",
+        allow_guest: bool = False,
+        allow_expired: bool = False,
+        allow_locked: bool = False,
+    ) -> Requester:
+        """Like `get_user_by_req`, except also checks if the user has access to
+        the experimental feature. If they don't returns a 404 unrecognized
+        request.
+        """
+
    async def validate_appservice_can_control_user_id(
        self, app_service: ApplicationService, user_id: str
    ) -> None:
@@ -28,6 +28,7 @@ from synapse.api.errors import (
    Codes,
    InvalidClientTokenError,
    MissingClientTokenError,
+    UnrecognizedRequestError,
 )
 from synapse.http.site import SynapseRequest
 from synapse.logging.opentracing import active_span, force_tracing, start_active_span
@@ -38,8 +39,10 @@ from . import GUEST_DEVICE_ID
 from .base import BaseAuth

 if TYPE_CHECKING:
+    from synapse.rest.admin.experimental_features import ExperimentalFeature
    from synapse.server import HomeServer

+
 logger = logging.getLogger(__name__)


@@ -106,6 +109,32 @@ class InternalAuth(BaseAuth):
                    parent_span.set_tag("appservice_id", requester.app_service.id)
            return requester

+    async def get_user_by_req_experimental_feature(
+        self,
+        request: SynapseRequest,
+        feature: "ExperimentalFeature",
+        allow_guest: bool = False,
+        allow_expired: bool = False,
+        allow_locked: bool = False,
+    ) -> Requester:
+        try:
+            requester = await self.get_user_by_req(
+                request,
+                allow_guest=allow_guest,
+                allow_expired=allow_expired,
+                allow_locked=allow_locked,
+            )
+            if await self.store.is_feature_enabled(requester.user.to_string(), feature):
+                return requester
+
+            raise UnrecognizedRequestError(code=404)
+        except (AuthError, InvalidClientTokenError):
+            if feature.is_globally_enabled(self.hs.config):
+                # If its globally enabled then return the auth error
+                raise
+
+            raise UnrecognizedRequestError(code=404)
+
    @cancellable
    async def _wrapped_get_user_by_req(
        self,
@@ -40,6 +40,7 @@ from synapse.api.errors import (
    OAuthInsufficientScopeError,
    StoreError,
    SynapseError,
+    UnrecognizedRequestError,
 )
 from synapse.http.site import SynapseRequest
 from synapse.logging.context import make_deferred_yieldable
@@ -48,6 +49,7 @@ from synapse.util import json_decoder
 from synapse.util.caches.cached_call import RetryOnExceptionCachedCall

 if TYPE_CHECKING:
+    from synapse.rest.admin.experimental_features import ExperimentalFeature
    from synapse.server import HomeServer

 logger = logging.getLogger(__name__)
@@ -143,6 +145,18 @@ class MSC3861DelegatedAuth(BaseAuth):
        # metadata.validate_introspection_endpoint()
        return metadata

+    async def _introspection_endpoint(self) -> str:
+        """
+        Returns the introspection endpoint of the issuer
+
+        It uses the config option if set, otherwise it will use OIDC discovery to get it
+        """
+        if self._config.introspection_endpoint is not None:
+            return self._config.introspection_endpoint
+
+        metadata = await self._load_metadata()
+        return metadata.get("introspection_endpoint")
+
    async def _introspect_token(self, token: str) -> IntrospectionToken:
        """
        Send a token to the introspection endpoint and returns the introspection response
@@ -159,8 +173,7 @@ class MSC3861DelegatedAuth(BaseAuth):
        Returns:
            The introspection response
        """
-        metadata = await self._issuer_metadata.get()
-        introspection_endpoint = metadata.get("introspection_endpoint")
+        introspection_endpoint = await self._introspection_endpoint()
        raw_headers: Dict[str, str] = {
            "Content-Type": "application/x-www-form-urlencoded",
            "User-Agent": str(self._http_client.user_agent, "utf-8"),
@@ -245,6 +258,32 @@ class MSC3861DelegatedAuth(BaseAuth):

        return requester

+    async def get_user_by_req_experimental_feature(
+        self,
+        request: SynapseRequest,
+        feature: "ExperimentalFeature",
+        allow_guest: bool = False,
+        allow_expired: bool = False,
+        allow_locked: bool = False,
+    ) -> Requester:
+        try:
+            requester = await self.get_user_by_req(
+                request,
+                allow_guest=allow_guest,
+                allow_expired=allow_expired,
+                allow_locked=allow_locked,
+            )
+            if await self.store.is_feature_enabled(requester.user.to_string(), feature):
+                return requester
+
+            raise UnrecognizedRequestError(code=404)
+        except (AuthError, InvalidClientTokenError):
+            if feature.is_globally_enabled(self.hs.config):
+                # If its globally enabled then return the auth error
+                raise
+
+            raise UnrecognizedRequestError(code=404)
+
    async def get_user_by_access_token(
        self,
        token: str,
@@ -50,7 +50,7 @@ class Membership:
    KNOCK: Final = "knock"
    LEAVE: Final = "leave"
    BAN: Final = "ban"
-    LIST: Final = {INVITE, JOIN, KNOCK, LEAVE, BAN}
+    LIST: Final = frozenset((INVITE, JOIN, KNOCK, LEAVE, BAN))


 class PresenceState:
@@ -128,9 +128,13 @@ class EventTypes:
    SpaceParent: Final = "m.space.parent"

    Reaction: Final = "m.reaction"
+    Sticker: Final = "m.sticker"
+    LiveLocationShareStart: Final = "m.beacon_info"

    CallInvite: Final = "m.call.invite"

+    PollStart: Final = "m.poll.start"
+

 class ToDeviceEventTypes:
    RoomKeyRequest: Final = "m.room_key_request"
@@ -221,6 +225,11 @@ class EventContentFields:
    # This is deprecated in MSC2175.
    ROOM_CREATOR: Final = "creator"

+    # The version of the room for `m.room.create` events.
+    ROOM_VERSION: Final = "room_version"
+
+    ROOM_NAME: Final = "name"
+
    # Used in m.room.guest_access events.
    GUEST_ACCESS: Final = "guest_access"

@@ -233,6 +242,11 @@ class EventContentFields:
    # an unspecced field added to to-device messages to identify them uniquely-ish
    TO_DEVICE_MSGID: Final = "org.matrix.msgid"

+    # `m.room.encryption`` algorithm field
+    ENCRYPTION_ALGORITHM: Final = "algorithm"
+
+    TOMBSTONE_SUCCESSOR_ROOM: Final = "replacement_room"
+

 class EventUnsignedContentFields:
    """Fields found inside the 'unsigned' data on events"""
@@ -128,6 +128,10 @@ class Codes(str, Enum):
    # MSC2677
    DUPLICATE_ANNOTATION = "M_DUPLICATE_ANNOTATION"

+    # MSC3575 we are telling the client they need to expire their sliding sync
+    # connection.
+    UNKNOWN_POS = "M_UNKNOWN_POS"
+

 class CodeMessageException(RuntimeError):
    """An exception with integer code, a message string attributes and optional headers.
@@ -847,3 +851,17 @@ class PartialStateConflictError(SynapseError):
            msg=PartialStateConflictError.message(),
            errcode=Codes.UNKNOWN,
        )
+
+
+class SlidingSyncUnknownPosition(SynapseError):
+    """An error that Synapse can return to signal to the client to expire their
+    sliding sync connection (i.e. send a new request without a `?since=`
+    param).
+    """
+
+    def __init__(self) -> None:
+        super().__init__(
+            HTTPStatus.BAD_REQUEST,
+            msg="Unknown position",
+            errcode=Codes.UNKNOWN_POS,
+        )
@@ -236,9 +236,8 @@ class Ratelimiter:
            requester: The requester that is doing the action, if any.
            key: An arbitrary key used to classify an action. Defaults to the
                requester's user ID.
-            n_actions: The number of times the user wants to do this action. If the user
-                cannot do all of the actions, the user's action count is not incremented
-                at all.
+            n_actions: The number of times the user performed the action. May be negative
+                to "refund" the rate limit.
            _time_now_s: The current time. Optional, defaults to the current time according
                to self.clock. Only used by tests.
        """
@@ -110,7 +110,7 @@ class AdminCmdStore(


 class AdminCmdServer(HomeServer):
-    DATASTORE_CLASS = AdminCmdStore  # type: ignore
+    DATASTORE_CLASS = AdminCmdStore


 async def export_data_command(hs: HomeServer, args: argparse.Namespace) -> None:
@@ -74,6 +74,9 @@ from synapse.storage.databases.main.event_push_actions import (
    EventPushActionsWorkerStore,
 )
 from synapse.storage.databases.main.events_worker import EventsWorkerStore
+from synapse.storage.databases.main.experimental_features import (
+    ExperimentalFeaturesStore,
+)
 from synapse.storage.databases.main.filtering import FilteringWorkerStore
 from synapse.storage.databases.main.keys import KeyStore
 from synapse.storage.databases.main.lock import LockStore
@@ -95,6 +98,7 @@ from synapse.storage.databases.main.roommember import RoomMemberWorkerStore
 from synapse.storage.databases.main.search import SearchStore
 from synapse.storage.databases.main.session import SessionStore
 from synapse.storage.databases.main.signatures import SignatureWorkerStore
+from synapse.storage.databases.main.sliding_sync import SlidingSyncStore
 from synapse.storage.databases.main.state import StateGroupWorkerStore
 from synapse.storage.databases.main.stats import StatsStore
 from synapse.storage.databases.main.stream import StreamWorkerStore
@@ -155,6 +159,8 @@ class GenericWorkerStore(
    LockStore,
    SessionStore,
    TaskSchedulerWorkerStore,
+    ExperimentalFeaturesStore,
+    SlidingSyncStore,
 ):
    # Properties that multiple storage classes define. Tell mypy what the
    # expected type is.
@@ -163,7 +169,7 @@ class GenericWorkerStore(


 class GenericWorkerServer(HomeServer):
-    DATASTORE_CLASS = GenericWorkerStore  # type: ignore
+    DATASTORE_CLASS = GenericWorkerStore

    def _listen_http(self, listener_config: ListenerConfig) -> None:
        assert listener_config.http_options is not None
@@ -202,6 +208,21 @@ class GenericWorkerServer(HomeServer):
                                "/_synapse/admin": admin_resource,
                            }
                        )
+
+                        if "federation" not in res.names:
+                            # Only load the federation media resource separately if federation
+                            # resource is not specified since federation resource includes media
+                            # resource.
+                            resources[FEDERATION_PREFIX] = TransportLayerServer(
+                                self, servlet_groups=["media"]
+                            )
+                        if "client" not in res.names:
+                            # Only load the client media resource separately if client
+                            # resource is not specified since client resource includes media
+                            # resource.
+                            resources[CLIENT_API_PREFIX] = ClientRestResource(
+                                self, servlet_groups=["media"]
+                            )
                    else:
                        logger.warning(
                            "A 'media' listener is configured but the media"
@@ -81,7 +81,7 @@ def gz_wrap(r: Resource) -> Resource:


 class SynapseHomeServer(HomeServer):
-    DATASTORE_CLASS = DataStore  # type: ignore
+    DATASTORE_CLASS = DataStore

    def _listener_http(
        self,
@@ -101,6 +101,12 @@ class SynapseHomeServer(HomeServer):
                    # Skip loading openid resource if federation is defined
                    # since federation resource will include openid
                    continue
+                if name == "media" and (
+                    "federation" in res.names or "client" in res.names
+                ):
+                    # Skip loading media resource if federation or client are defined
+                    # since federation & client resources will include media
+                    continue
                if name == "health":
                    # Skip loading, health resource is always included
                    continue
@@ -217,7 +223,7 @@ class SynapseHomeServer(HomeServer):
            )

        if name in ["media", "federation", "client"]:
-            if self.config.server.enable_media_repo:
+            if self.config.media.can_load_media_repo:
                media_repo = self.get_media_repository_resource()
                resources.update(
                    {
@@ -231,6 +237,14 @@ class SynapseHomeServer(HomeServer):
                    "'media' resource conflicts with enable_media_repo=False"
                )

+        if name == "media":
+            resources[FEDERATION_PREFIX] = TransportLayerServer(
+                self, servlet_groups=["media"]
+            )
+            resources[CLIENT_API_PREFIX] = ClientRestResource(
+                self, servlet_groups=["media"]
+            )
+
        if name in ["keys", "federation"]:
            resources[SERVER_KEY_PREFIX] = KeyResource(self)

@@ -140,6 +140,12 @@ class MSC3861:
                ("experimental", "msc3861", "client_auth_method"),
            )

+    introspection_endpoint: Optional[str] = attr.ib(
+        default=None,
+        validator=attr.validators.optional(attr.validators.instance_of(str)),
+    )
+    """The URL of the introspection endpoint used to validate access tokens."""
+
    account_management_url: Optional[str] = attr.ib(
        default=None,
        validator=attr.validators.optional(attr.validators.instance_of(str)),
@@ -437,10 +443,6 @@ class ExperimentalConfig(Config):
            "msc3823_account_suspension", False
        )

-        self.msc3916_authenticated_media_enabled = experimental.get(
-            "msc3916_authenticated_media_enabled", False
-        )
-
        # MSC4151: Report room API (Client-Server API)
        self.msc4151_enabled: bool = experimental.get("msc4151_enabled", False)

@@ -126,7 +126,7 @@ class ContentRepositoryConfig(Config):
        # Only enable the media repo if either the media repo is enabled or the
        # current worker app is the media repo.
        if (
-            self.root.server.enable_media_repo is False
+            config.get("enable_media_repo", True) is False
            and config.get("worker_app") != "synapse.app.media_repository"
        ):
            self.can_load_media_repo = False
@@ -272,6 +272,10 @@ class ContentRepositoryConfig(Config):
                remote_media_lifetime
            )

+        self.enable_authenticated_media = config.get(
+            "enable_authenticated_media", False
+        )
+
    def generate_config_section(self, data_dir_path: str, **kwargs: Any) -> str:
        assert data_dir_path is not None
        media_store = os.path.join(data_dir_path, "media_store")
@@ -384,6 +384,11 @@ class ServerConfig(Config):
        # Whether to internally track presence, requires that presence is enabled,
        self.track_presence = self.presence_enabled and presence_enabled != "untracked"

+        # Determines if presence results for offline users are included on initial/full sync
+        self.presence_include_offline_users_on_sync = presence_config.get(
+            "include_offline_users_on_sync", False
+        )
+
        # Custom presence router module
        # This is the legacy way of configuring it (the config should now be put in the modules section)
        self.presence_router_module_class = None
@@ -395,12 +400,6 @@ class ServerConfig(Config):
                self.presence_router_config,
            ) = load_module(presence_router_config, ("presence", "presence_router"))

-        # whether to enable the media repository endpoints. This should be set
-        # to false if the media repository is running as a separate endpoint;
-        # doing so ensures that we will not run cache cleanup jobs on the
-        # master, potentially causing inconsistency.
-        self.enable_media_repo = config.get("enable_media_repo", True)
-
        # Whether to require authentication to retrieve profile data (avatars,
        # display names) of other users through the client API.
        self.require_auth_for_profile_requests = config.get(
@@ -589,7 +589,7 @@ class BaseV2KeyFetcher(KeyFetcher):
                % (server_name,)
            )

-        for key_id, key_data in response_json["old_verify_keys"].items():
+        for key_id, key_data in response_json.get("old_verify_keys", {}).items():
            if is_signing_algorithm_supported(key_id):
                key_base64 = key_data["key"]
                key_bytes = decode_base64(key_base64)
@@ -554,3 +554,22 @@ def relation_from_event(event: EventBase) -> Optional[_EventRelation]:
            aggregation_key = None

    return _EventRelation(parent_id, rel_type, aggregation_key)
+
+
+@attr.s(slots=True, frozen=True, auto_attribs=True)
+class StrippedStateEvent:
+    """
+    A stripped down state event. Usually used for remote invite/knocks so the user can
+    make an informed decision on whether they want to join.
+
+    Attributes:
+        type: Event `type`
+        state_key: Event `state_key`
+        sender: Event `sender`
+        content: Event `content`
+    """
+
+    type: str
+    state_key: str
+    sender: str
+    content: Dict[str, Any]
@@ -49,7 +49,7 @@ from synapse.api.errors import Codes, SynapseError
 from synapse.api.room_versions import RoomVersion
 from synapse.types import JsonDict, Requester

-from . import EventBase, make_event_from_dict
+from . import EventBase, StrippedStateEvent, make_event_from_dict

 if TYPE_CHECKING:
    from synapse.handlers.relations import BundledAggregations
@@ -854,3 +854,30 @@ def strip_event(event: EventBase) -> JsonDict:
        "content": event.content,
        "sender": event.sender,
    }
+
+
+def parse_stripped_state_event(raw_stripped_event: Any) -> Optional[StrippedStateEvent]:
+    """
+    Given a raw value from an event's `unsigned` field, attempt to parse it into a
+    `StrippedStateEvent`.
+    """
+    if isinstance(raw_stripped_event, dict):
+        # All of these fields are required
+        type = raw_stripped_event.get("type")
+        state_key = raw_stripped_event.get("state_key")
+        sender = raw_stripped_event.get("sender")
+        content = raw_stripped_event.get("content")
+        if (
+            isinstance(type, str)
+            and isinstance(state_key, str)
+            and isinstance(sender, str)
+            and isinstance(content, dict)
+        ):
+            return StrippedStateEvent(
+                type=type,
+                state_key=state_key,
+                sender=sender,
+                content=content,
+            )
+
+    return None
@@ -338,12 +338,11 @@ class PerDestinationQueue:
                    # not caught up yet
                    return

-            pending_pdus = []
            while True:
                self._new_data_to_send = False

                async with _TransactionQueueManager(self) as (
-                    pending_pdus,
+                    pending_pdus,  # noqa: F811
                    pending_edus,
                ):
                    if not pending_pdus and not pending_edus:
@@ -33,6 +33,7 @@ from synapse.federation.transport.server.federation import (
    FEDERATION_SERVLET_CLASSES,
    FederationAccountStatusServlet,
    FederationMediaDownloadServlet,
+    FederationMediaThumbnailServlet,
    FederationUnstableClientKeysClaimServlet,
 )
 from synapse.http.server import HttpServer, JsonResource
@@ -270,6 +271,10 @@ SERVLET_GROUPS: Dict[str, Iterable[Type[BaseFederationServlet]]] = {
    "federation": FEDERATION_SERVLET_CLASSES,
    "room_list": (PublicRoomList,),
    "openid": (OpenIdUserInfo,),
+    "media": (
+        FederationMediaDownloadServlet,
+        FederationMediaThumbnailServlet,
+    ),
 }


@@ -316,8 +321,11 @@ def register_servlets(
            ):
                continue

-            if servletclass == FederationMediaDownloadServlet:
-                if not hs.config.server.enable_media_repo:
+            if (
+                servletclass == FederationMediaDownloadServlet
+                or servletclass == FederationMediaThumbnailServlet
+            ):
+                if not hs.config.media.can_load_media_repo:
                    continue

            servletclass(
@@ -363,6 +363,8 @@ class BaseFederationServlet:
                            if (
                                func.__self__.__class__.__name__  # type: ignore
                                == "FederationMediaDownloadServlet"
+                                or func.__self__.__class__.__name__  # type: ignore
+                                == "FederationMediaThumbnailServlet"
                            ):
                                response = await func(
                                    origin, content, request, *args, **kwargs
@@ -375,6 +377,8 @@ class BaseFederationServlet:
                        if (
                            func.__self__.__class__.__name__  # type: ignore
                            == "FederationMediaDownloadServlet"
+                            or func.__self__.__class__.__name__  # type: ignore
+                            == "FederationMediaThumbnailServlet"
                        ):
                            response = await func(
                                origin, content, request, *args, **kwargs
@@ -46,11 +46,13 @@ from synapse.http.servlet import (
    parse_boolean_from_args,
    parse_integer,
    parse_integer_from_args,
+    parse_string,
    parse_string_from_args,
    parse_strings_from_args,
 )
 from synapse.http.site import SynapseRequest
 from synapse.media._base import DEFAULT_MAX_TIMEOUT_MS, MAXIMUM_ALLOWED_MAX_TIMEOUT_MS
+from synapse.media.thumbnailer import ThumbnailProvider
 from synapse.types import JsonDict
 from synapse.util import SYNAPSE_VERSION
 from synapse.util.ratelimitutils import FederationRateLimiter
@@ -826,6 +828,59 @@ class FederationMediaDownloadServlet(BaseFederationServerServlet):
        )


+class FederationMediaThumbnailServlet(BaseFederationServerServlet):
+    """
+    Implementation of new federation media `/thumbnail` endpoint outlined in MSC3916. Returns
+    a multipart/mixed response consisting of a JSON object and the requested media
+    item. This endpoint only returns local media.
+    """
+
+    PATH = "/media/thumbnail/(?P<media_id>[^/]*)"
+    RATELIMIT = True
+
+    def __init__(
+        self,
+        hs: "HomeServer",
+        ratelimiter: FederationRateLimiter,
+        authenticator: Authenticator,
+        server_name: str,
+    ):
+        super().__init__(hs, authenticator, ratelimiter, server_name)
+        self.media_repo = self.hs.get_media_repository()
+        self.dynamic_thumbnails = hs.config.media.dynamic_thumbnails
+        self.thumbnail_provider = ThumbnailProvider(
+            hs, self.media_repo, self.media_repo.media_storage
+        )
+
+    async def on_GET(
+        self,
+        origin: Optional[str],
+        content: Literal[None],
+        request: SynapseRequest,
+        media_id: str,
+    ) -> None:
+
+        width = parse_integer(request, "width", required=True)
+        height = parse_integer(request, "height", required=True)
+        method = parse_string(request, "method", "scale")
+        # TODO Parse the Accept header to get an prioritised list of thumbnail types.
+        m_type = "image/png"
+        max_timeout_ms = parse_integer(
+            request, "timeout_ms", default=DEFAULT_MAX_TIMEOUT_MS
+        )
+        max_timeout_ms = min(max_timeout_ms, MAXIMUM_ALLOWED_MAX_TIMEOUT_MS)
+
+        if self.dynamic_thumbnails:
+            await self.thumbnail_provider.select_or_generate_local_thumbnail(
+                request, media_id, width, height, method, m_type, max_timeout_ms, True
+            )
+        else:
+            await self.thumbnail_provider.respond_local_thumbnail(
+                request, media_id, width, height, method, m_type, max_timeout_ms, True
+            )
+        self.media_repo.mark_recently_accessed(None, media_id)
+
+
 FEDERATION_SERVLET_CLASSES: Tuple[Type[BaseFederationServlet], ...] = (
    FederationSendServlet,
    FederationEventServlet,
@@ -857,5 +912,4 @@ FEDERATION_SERVLET_CLASSES: Tuple[Type[BaseFederationServlet], ...] = (
    FederationV1SendKnockServlet,
    FederationMakeKnockServlet,
    FederationAccountStatusServlet,
-    FederationMediaDownloadServlet,
 )
@@ -197,8 +197,14 @@ class AdminHandler:
            # events that we have and then filtering, this isn't the most
            # efficient method perhaps but it does guarantee we get everything.
            while True:
-                events, _ = await self._store.paginate_room_events(
-                    room_id, from_key, to_key, limit=100, direction=Direction.FORWARDS
+                events, _ = (
+                    await self._store.paginate_room_events_by_topological_ordering(
+                        room_id=room_id,
+                        from_key=from_key,
+                        to_key=to_key,
+                        limit=100,
+                        direction=Direction.FORWARDS,
+                    )
                )
                if not events:
                    break
@@ -283,6 +283,10 @@ class DeactivateAccountHandler:
                    ratelimit=False,
                    require_consent=False,
                )
+
+                # Mark the room forgotten too, because they won't be able to do this
+                # for us. This may lead to the room being purged eventually.
+                await self._room_member_handler.forget(user, room_id)
            except Exception:
                logger.exception(
                    "Failed to part user %r from room %r: ignoring and continuing",
@@ -20,10 +20,20 @@
 #
 #
 import logging
-from typing import TYPE_CHECKING, Dict, Iterable, List, Mapping, Optional, Set, Tuple
+from typing import (
+    TYPE_CHECKING,
+    AbstractSet,
+    Dict,
+    Iterable,
+    List,
+    Mapping,
+    Optional,
+    Set,
+    Tuple,
+)

 from synapse.api import errors
-from synapse.api.constants import EduTypes, EventTypes
+from synapse.api.constants import EduTypes, EventTypes, Membership
 from synapse.api.errors import (
    Codes,
    FederationDeniedError,
@@ -38,7 +48,9 @@ from synapse.metrics.background_process_metrics import (
    wrap_as_background_process,
 )
 from synapse.storage.databases.main.client_ips import DeviceLastConnectionInfo
+from synapse.storage.databases.main.state_deltas import StateDelta
 from synapse.types import (
+    DeviceListUpdates,
    JsonDict,
    JsonMapping,
    ScheduledTask,
@@ -214,138 +226,210 @@ class DeviceWorkerHandler:
    @cancellable
    async def get_user_ids_changed(
        self, user_id: str, from_token: StreamToken
-    ) -> JsonDict:
+    ) -> DeviceListUpdates:
        """Get list of users that have had the devices updated, or have newly
        joined a room, that `user_id` may be interested in.
        """

        set_tag("user_id", user_id)
        set_tag("from_token", str(from_token))
-        now_room_key = self.store.get_room_max_token()

-        room_ids = await self.store.get_rooms_for_user(user_id)
+        now_token = self._event_sources.get_current_token()

-        changed = await self.get_device_changes_in_shared_rooms(
-            user_id, room_ids, from_token
+        # We need to work out all the different membership changes for the user
+        # and user they share a room with, to pass to
+        # `generate_sync_entry_for_device_list`. See its docstring for details
+        # on the data required.
+
+        joined_room_ids = await self.store.get_rooms_for_user(user_id)
+
+        # Get the set of rooms that the user has joined/left
+        membership_changes = (
+            await self.store.get_current_state_delta_membership_changes_for_user(
+                user_id, from_key=from_token.room_key, to_key=now_token.room_key
+            )
        )

-        # Then work out if any users have since joined
-        rooms_changed = self.store.get_rooms_that_changed(room_ids, from_token.room_key)
+        # Check for newly joined or left rooms. We need to make sure that we add
+        # to newly joined in the case membership goes from join -> leave -> join
+        # again.
+        newly_joined_rooms: Set[str] = set()
+        newly_left_rooms: Set[str] = set()
+        for change in membership_changes:
+            # We check for changes in "joinedness", i.e. if the membership has
+            # changed to or from JOIN.
+            if change.membership == Membership.JOIN:
+                if change.prev_membership != Membership.JOIN:
+                    newly_joined_rooms.add(change.room_id)
+                    newly_left_rooms.discard(change.room_id)
+            elif change.prev_membership == Membership.JOIN:
+                newly_joined_rooms.discard(change.room_id)
+                newly_left_rooms.add(change.room_id)

-        member_events = await self.store.get_membership_changes_for_user(
-            user_id, from_token.room_key, now_room_key
+        # We now work out if any other users have since joined or left the rooms
+        # the user is currently in.
+
+        # List of membership changes per room
+        room_to_deltas: Dict[str, List[StateDelta]] = {}
+        # The set of event IDs of membership events (so we can fetch their
+        # associated membership).
+        memberships_to_fetch: Set[str] = set()
+
+        # TODO: Only pull out membership events?
+        state_changes = await self.store.get_current_state_deltas_for_rooms(
+            joined_room_ids, from_token=from_token.room_key, to_token=now_token.room_key
        )
-        rooms_changed.update(event.room_id for event in member_events)
-
-        stream_ordering = from_token.room_key.stream
-
-        possibly_changed = set(changed)
-        possibly_left = set()
-        for room_id in rooms_changed:
-            # Check if the forward extremities have changed. If not then we know
-            # the current state won't have changed, and so we can skip this room.
-            try:
-                if not await self.store.have_room_forward_extremities_changed_since(
-                    room_id, stream_ordering
-                ):
-                    continue
-            except errors.StoreError:
-                pass
-
-            current_state_ids = await self._state_storage.get_current_state_ids(
-                room_id, await_full_state=False
-            )
-
-            # The user may have left the room
-            # TODO: Check if they actually did or if we were just invited.
-            if room_id not in room_ids:
-                for etype, state_key in current_state_ids.keys():
-                    if etype != EventTypes.Member:
-                        continue
-                    possibly_left.add(state_key)
+        for delta in state_changes:
+            if delta.event_type != EventTypes.Member:
                continue

-            # Fetch the current state at the time.
-            try:
-                event_ids = await self.store.get_forward_extremities_for_room_at_stream_ordering(
-                    room_id, stream_ordering=stream_ordering
-                )
-            except errors.StoreError:
-                # we have purged the stream_ordering index since the stream
-                # ordering: treat it the same as a new room
-                event_ids = []
+            room_to_deltas.setdefault(delta.room_id, []).append(delta)
+            if delta.event_id:
+                memberships_to_fetch.add(delta.event_id)
+            if delta.prev_event_id:
+                memberships_to_fetch.add(delta.prev_event_id)

-            # special-case for an empty prev state: include all members
-            # in the changed list
-            if not event_ids:
-                log_kv(
-                    {"event": "encountered empty previous state", "room_id": room_id}
-                )
-                for etype, state_key in current_state_ids.keys():
-                    if etype != EventTypes.Member:
-                        continue
-                    possibly_changed.add(state_key)
-                continue
+        # Fetch all the memberships for the membership events
+        event_id_to_memberships = await self.store.get_membership_from_event_ids(
+            memberships_to_fetch
+        )

-            current_member_id = current_state_ids.get((EventTypes.Member, user_id))
-            if not current_member_id:
-                continue
+        joined_invited_knocked = (
+            Membership.JOIN,
+            Membership.INVITE,
+            Membership.KNOCK,
+        )

-            # mapping from event_id -> state_dict
-            prev_state_ids = await self._state_storage.get_state_ids_for_events(
-                event_ids,
-                await_full_state=False,
-            )
+        # We now want to find any user that have newly joined/invited/knocked,
+        # or newly left, similarly to above.
+        newly_joined_or_invited_or_knocked_users: Set[str] = set()
+        newly_left_users: Set[str] = set()
+        for _, deltas in room_to_deltas.items():
+            for delta in deltas:
+                # Get the prev/new memberships for the delta
+                new_membership = None
+                prev_membership = None
+                if delta.event_id:
+                    m = event_id_to_memberships.get(delta.event_id)
+                    if m is not None:
+                        new_membership = m.membership
+                if delta.prev_event_id:
+                    m = event_id_to_memberships.get(delta.prev_event_id)
+                    if m is not None:
+                        prev_membership = m.membership

-            # Check if we've joined the room? If so we just blindly add all the users to
-            # the "possibly changed" users.
-            for state_dict in prev_state_ids.values():
-                member_event = state_dict.get((EventTypes.Member, user_id), None)
-                if not member_event or member_event != current_member_id:
-                    for etype, state_key in current_state_ids.keys():
-                        if etype != EventTypes.Member:
-                            continue
-                        possibly_changed.add(state_key)
-                    break
+                # Check if a user has newly joined/invited/knocked, or left.
+                if new_membership in joined_invited_knocked:
+                    if prev_membership not in joined_invited_knocked:
+                        newly_joined_or_invited_or_knocked_users.add(delta.state_key)
+                        newly_left_users.discard(delta.state_key)
+                elif prev_membership in joined_invited_knocked:
+                    newly_joined_or_invited_or_knocked_users.discard(delta.state_key)
+                    newly_left_users.add(delta.state_key)

-            # If there has been any change in membership, include them in the
-            # possibly changed list. We'll check if they are joined below,
-            # and we're not toooo worried about spuriously adding users.
-            for key, event_id in current_state_ids.items():
-                etype, state_key = key
-                if etype != EventTypes.Member:
-                    continue
+        # Now we actually calculate the device list entry with the information
+        # calculated above.
+        device_list_updates = await self.generate_sync_entry_for_device_list(
+            user_id=user_id,
+            since_token=from_token,
+            now_token=now_token,
+            joined_room_ids=joined_room_ids,
+            newly_joined_rooms=newly_joined_rooms,
+            newly_joined_or_invited_or_knocked_users=newly_joined_or_invited_or_knocked_users,
+            newly_left_rooms=newly_left_rooms,
+            newly_left_users=newly_left_users,
+        )

-                # check if this member has changed since any of the extremities
-                # at the stream_ordering, and add them to the list if so.
-                for state_dict in prev_state_ids.values():
-                    prev_event_id = state_dict.get(key, None)
-                    if not prev_event_id or prev_event_id != event_id:
-                        if state_key != user_id:
-                            possibly_changed.add(state_key)
-                        break
+        log_kv(
+            {
+                "changed": device_list_updates.changed,
+                "left": device_list_updates.left,
+            }
+        )

-        if possibly_changed or possibly_left:
-            possibly_joined = possibly_changed
-            possibly_left = possibly_changed | possibly_left
+        return device_list_updates

-            # Double check if we still share rooms with the given user.
-            users_rooms = await self.store.get_rooms_for_users(possibly_left)
-            for changed_user_id, entries in users_rooms.items():
-                if any(rid in room_ids for rid in entries):
-                    possibly_left.discard(changed_user_id)
-                else:
-                    possibly_joined.discard(changed_user_id)
+    @measure_func("_generate_sync_entry_for_device_list")
+    async def generate_sync_entry_for_device_list(
+        self,
+        user_id: str,
+        since_token: StreamToken,
+        now_token: StreamToken,
+        joined_room_ids: AbstractSet[str],
+        newly_joined_rooms: AbstractSet[str],
+        newly_joined_or_invited_or_knocked_users: AbstractSet[str],
+        newly_left_rooms: AbstractSet[str],
+        newly_left_users: AbstractSet[str],
+    ) -> DeviceListUpdates:
+        """Generate the DeviceListUpdates section of sync

-        else:
-            possibly_joined = set()
-            possibly_left = set()
+        Args:
+            sync_result_builder
+            newly_joined_rooms: Set of rooms user has joined since previous sync
+            newly_joined_or_invited_or_knocked_users: Set of users that have joined,
+                been invited to a room or are knocking on a room since
+                previous sync.
+            newly_left_rooms: Set of rooms user has left since previous sync
+            newly_left_users: Set of users that have left a room we're in since
+                previous sync
+        """
+        # Take a copy since these fields will be mutated later.
+        newly_joined_or_invited_or_knocked_users = set(
+            newly_joined_or_invited_or_knocked_users
+        )
+        newly_left_users = set(newly_left_users)

-        result = {"changed": list(possibly_joined), "left": list(possibly_left)}
+        # We want to figure out what user IDs the client should refetch
+        # device keys for, and which users we aren't going to track changes
+        # for anymore.
+        #
+        # For the first step we check:
+        #   a. if any users we share a room with have updated their devices,
+        #      and
+        #   b. we also check if we've joined any new rooms, or if a user has
+        #      joined a room we're in.
+        #
+        # For the second step we just find any users we no longer share a
+        # room with by looking at all users that have left a room plus users
+        # that were in a room we've left.

-        log_kv(result)
+        users_that_have_changed = set()

-        return result
+        # Step 1a, check for changes in devices of users we share a room
+        # with
+        users_that_have_changed = await self.get_device_changes_in_shared_rooms(
+            user_id,
+            joined_room_ids,
+            from_token=since_token,
+            now_token=now_token,
+        )
+
+        # Step 1b, check for newly joined rooms
+        for room_id in newly_joined_rooms:
+            joined_users = await self.store.get_users_in_room(room_id)
+            newly_joined_or_invited_or_knocked_users.update(joined_users)
+
+        # TODO: Check that these users are actually new, i.e. either they
+        # weren't in the previous sync *or* they left and rejoined.
+        users_that_have_changed.update(newly_joined_or_invited_or_knocked_users)
+
+        user_signatures_changed = await self.store.get_users_whose_signatures_changed(
+            user_id, since_token.device_list_key
+        )
+        users_that_have_changed.update(user_signatures_changed)
+
+        # Now find users that we no longer track
+        for room_id in newly_left_rooms:
+            left_users = await self.store.get_users_in_room(room_id)
+            newly_left_users.update(left_users)
+
+        # Remove any users that we still share a room with.
+        left_users_rooms = await self.store.get_rooms_for_users(newly_left_users)
+        for user_id, entries in left_users_rooms.items():
+            if any(rid in joined_room_ids for rid in entries):
+                newly_left_users.discard(user_id)
+
+        return DeviceListUpdates(changed=users_that_have_changed, left=newly_left_users)

    async def on_federation_query_user_devices(self, user_id: str) -> JsonDict:
        if not self.hs.is_mine(UserID.from_string(user_id)):
@@ -291,13 +291,20 @@ class E2eKeysHandler:

            # Only try and fetch keys for destinations that are not marked as
            # down.
-            filtered_destinations = await filter_destinations_by_retry_limiter(
-                remote_queries_not_in_cache.keys(),
-                self.clock,
-                self.store,
-                # Let's give an arbitrary grace period for those hosts that are
-                # only recently down
-                retry_due_within_ms=60 * 1000,
+            unfiltered_destinations = remote_queries_not_in_cache.keys()
+            filtered_destinations = set(
+                await filter_destinations_by_retry_limiter(
+                    unfiltered_destinations,
+                    self.clock,
+                    self.store,
+                    # Let's give an arbitrary grace period for those hosts that are
+                    # only recently down
+                    retry_due_within_ms=60 * 1000,
+                )
+            )
+            failures.update(
+                (dest, _NOT_READY_FOR_RETRY_FAILURE)
+                for dest in (unfiltered_destinations - filtered_destinations)
            )

            await concurrently_execute(
@@ -1641,6 +1648,9 @@ def _check_device_signature(
        raise SynapseError(400, "Invalid signature", Codes.INVALID_SIGNATURE)


+_NOT_READY_FOR_RETRY_FAILURE = {"status": 503, "message": "Not ready for retry"}
+
+
 def _exception_to_failure(e: Exception) -> JsonDict:
    if isinstance(e, SynapseError):
        return {"status": e.code, "errcode": e.errcode, "message": str(e)}
@@ -1649,7 +1659,7 @@ def _exception_to_failure(e: Exception) -> JsonDict:
        return {"status": e.code, "message": str(e)}

    if isinstance(e, NotRetryingDestination):
-        return {"status": 503, "message": "Not ready for retry"}
+        return _NOT_READY_FOR_RETRY_FAILURE

    # include ConnectionRefused and other errors
    #
@@ -34,7 +34,7 @@ from synapse.api.errors import (
 from synapse.logging.opentracing import log_kv, trace
 from synapse.storage.databases.main.e2e_room_keys import RoomKey
 from synapse.types import JsonDict
-from synapse.util.async_helpers import Linearizer
+from synapse.util.async_helpers import ReadWriteLock

 if TYPE_CHECKING:
    from synapse.server import HomeServer
@@ -58,7 +58,7 @@ class E2eRoomKeysHandler:
        # clients belonging to a user will receive and try to upload a new session at
        # roughly the same time.  Also used to lock out uploads when the key is being
        # changed.
-        self._upload_linearizer = Linearizer("upload_room_keys_lock")
+        self._upload_lock = ReadWriteLock()

    @trace
    async def get_room_keys(
@@ -89,7 +89,7 @@ class E2eRoomKeysHandler:

        # we deliberately take the lock to get keys so that changing the version
        # works atomically
-        async with self._upload_linearizer.queue(user_id):
+        async with self._upload_lock.read(user_id):
            # make sure the backup version exists
            try:
                await self.store.get_e2e_room_keys_version_info(user_id, version)
@@ -132,7 +132,7 @@ class E2eRoomKeysHandler:
        """

        # lock for consistency with uploading
-        async with self._upload_linearizer.queue(user_id):
+        async with self._upload_lock.write(user_id):
            # make sure the backup version exists
            try:
                version_info = await self.store.get_e2e_room_keys_version_info(
@@ -193,7 +193,7 @@ class E2eRoomKeysHandler:
        # TODO: Validate the JSON to make sure it has the right keys.

        # XXX: perhaps we should use a finer grained lock here?
-        async with self._upload_linearizer.queue(user_id):
+        async with self._upload_lock.write(user_id):
            # Check that the version we're trying to upload is the current version
            try:
                version_info = await self.store.get_e2e_room_keys_version_info(user_id)
@@ -355,7 +355,7 @@ class E2eRoomKeysHandler:
        # TODO: Validate the JSON to make sure it has the right keys.

        # lock everyone out until we've switched version
-        async with self._upload_linearizer.queue(user_id):
+        async with self._upload_lock.write(user_id):
            new_version = await self.store.create_e2e_room_keys_version(
                user_id, version_info
            )
@@ -382,7 +382,7 @@ class E2eRoomKeysHandler:
        }
        """

-        async with self._upload_linearizer.queue(user_id):
+        async with self._upload_lock.read(user_id):
            try:
                res = await self.store.get_e2e_room_keys_version_info(user_id, version)
            except StoreError as e:
@@ -407,7 +407,7 @@ class E2eRoomKeysHandler:
            NotFoundError: if this backup version doesn't exist
        """

-        async with self._upload_linearizer.queue(user_id):
+        async with self._upload_lock.write(user_id):
            try:
                await self.store.delete_e2e_room_keys_version(user_id, version)
            except StoreError as e:
@@ -437,7 +437,7 @@ class E2eRoomKeysHandler:
            raise SynapseError(
                400, "Version in body does not match", Codes.INVALID_PARAM
            )
-        async with self._upload_linearizer.queue(user_id):
+        async with self._upload_lock.write(user_id):
            try:
                old_info = await self.store.get_e2e_room_keys_version_info(
                    user_id, version
@@ -507,13 +507,15 @@ class PaginationHandler:

        # Initially fetch the events from the database. With any luck, we can return
        # these without blocking on backfill (handled below).
-        events, next_key = await self.store.paginate_room_events(
-            room_id=room_id,
-            from_key=from_token.room_key,
-            to_key=to_room_key,
-            direction=pagin_config.direction,
-            limit=pagin_config.limit,
-            event_filter=event_filter,
+        events, next_key = (
+            await self.store.paginate_room_events_by_topological_ordering(
+                room_id=room_id,
+                from_key=from_token.room_key,
+                to_key=to_room_key,
+                direction=pagin_config.direction,
+                limit=pagin_config.limit,
+                event_filter=event_filter,
+            )
        )

        if pagin_config.direction == Direction.BACKWARDS:
@@ -582,13 +584,15 @@ class PaginationHandler:
                # If we did backfill something, refetch the events from the database to
                # catch anything new that might have been added since we last fetched.
                if did_backfill:
-                    events, next_key = await self.store.paginate_room_events(
-                        room_id=room_id,
-                        from_key=from_token.room_key,
-                        to_key=to_room_key,
-                        direction=pagin_config.direction,
-                        limit=pagin_config.limit,
-                        event_filter=event_filter,
+                    events, next_key = (
+                        await self.store.paginate_room_events_by_topological_ordering(
+                            room_id=room_id,
+                            from_key=from_token.room_key,
+                            to_key=to_room_key,
+                            direction=pagin_config.direction,
+                            limit=pagin_config.limit,
+                            event_filter=event_filter,
+                        )
                    )
            else:
                # Otherwise, we can backfill in the background for eventual
@@ -74,6 +74,17 @@ class ProfileHandler:
        self._third_party_rules = hs.get_module_api_callbacks().third_party_event_rules

    async def get_profile(self, user_id: str, ignore_backoff: bool = True) -> JsonDict:
+        """
+        Get a user's profile as a JSON dictionary.
+
+        Args:
+            user_id: The user to fetch the profile of.
+            ignore_backoff: True to ignore backoff when fetching over federation.
+
+        Returns:
+            A JSON dictionary. For local queries this will include the displayname and avatar_url
+            fields. For remote queries it may contain arbitrary information.
+        """
        target_user = UserID.from_string(user_id)

        if self.hs.is_mine(target_user):
@@ -107,6 +118,15 @@ class ProfileHandler:
                raise e.to_synapse_error()

    async def get_displayname(self, target_user: UserID) -> Optional[str]:
+        """
+        Fetch a user's display name from their profile.
+
+        Args:
+            target_user: The user to fetch the display name of.
+
+        Returns:
+            The user's display name or None if unset.
+        """
        if self.hs.is_mine(target_user):
            try:
                displayname = await self.store.get_profile_displayname(target_user)
@@ -203,6 +223,15 @@ class ProfileHandler:
            await self._update_join_states(requester, target_user)

    async def get_avatar_url(self, target_user: UserID) -> Optional[str]:
+        """
+        Fetch a user's avatar URL from their profile.
+
+        Args:
+            target_user: The user to fetch the avatar URL of.
+
+        Returns:
+            The user's avatar URL or None if unset.
+        """
        if self.hs.is_mine(target_user):
            try:
                avatar_url = await self.store.get_profile_avatar_url(target_user)
@@ -403,6 +432,12 @@ class ProfileHandler:
    async def _update_join_states(
        self, requester: Requester, target_user: UserID
    ) -> None:
+        """
+        Update the membership events of each room the user is joined to with the
+        new profile information.
+
+        Note that this stomps over any custom display name or avatar URL in member events.
+        """
        if not self.hs.is_mine(target_user):
            return

@@ -286,8 +286,14 @@ class ReceiptEventSource(EventSource[MultiWriterStreamToken, JsonMapping]):
        room_ids: Iterable[str],
        is_guest: bool,
        explicit_room_id: Optional[str] = None,
+        to_key: Optional[MultiWriterStreamToken] = None,
    ) -> Tuple[List[JsonMapping], MultiWriterStreamToken]:
-        to_key = self.get_current_key()
+        """
+        Find read receipts for given rooms (> `from_token` and <= `to_token`)
+        """
+
+        if to_key is None:
+            to_key = self.get_current_key()

        if from_key == to_key:
            return [], to_key
@@ -1188,6 +1188,8 @@ class RoomCreationHandler:
            )
            events_to_send.append((power_event, power_context))
        else:
+            # Please update the docs for `default_power_level_content_override` when
+            # updating the `events` dict below
            power_level_content: JsonDict = {
                "users": {creator_id: 100},
                "users_default": 0,
@@ -1748,7 +1750,7 @@ class RoomEventSource(EventSource[RoomStreamToken, EventBase]):
                from_key=from_key,
                to_key=to_key,
                limit=limit or 10,
-                order="ASC",
+                direction=Direction.FORWARDS,
            )

            events = list(room_events)
@@ -0,0 +1,662 @@
+#
+# This file is licensed under the Affero General Public License (AGPL) version 3.
+#
+# Copyright (C) 2023 New Vector, Ltd
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# See the GNU Affero General Public License for more details:
+# <https://www.gnu.org/licenses/agpl-3.0.html>.
+#
+
+import logging
+from typing import TYPE_CHECKING, Dict, List, Mapping, Optional, Sequence, Set
+
+from typing_extensions import assert_never
+
+from synapse.api.constants import AccountDataTypes
+from synapse.handlers.receipts import ReceiptEventSource
+from synapse.logging.opentracing import trace
+from synapse.types import (
+    DeviceListUpdates,
+    JsonMapping,
+    MultiWriterStreamToken,
+    SlidingSyncStreamToken,
+    StreamToken,
+)
+from synapse.types.handlers.sliding_sync import (
+    HaveSentRoomFlag,
+    MutablePerConnectionState,
+    OperationType,
+    PerConnectionState,
+    SlidingSyncConfig,
+    SlidingSyncResult,
+)
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
+logger = logging.getLogger(__name__)
+
+
+class SlidingSyncExtensionHandler:
+    """Handles the extensions to sliding sync."""
+
+    def __init__(self, hs: "HomeServer"):
+        self.store = hs.get_datastores().main
+        self.event_sources = hs.get_event_sources()
+        self.device_handler = hs.get_device_handler()
+        self.push_rules_handler = hs.get_push_rules_handler()
+
+    @trace
+    async def get_extensions_response(
+        self,
+        sync_config: SlidingSyncConfig,
+        previous_connection_state: "PerConnectionState",
+        new_connection_state: "MutablePerConnectionState",
+        actual_lists: Dict[str, SlidingSyncResult.SlidingWindowList],
+        actual_room_ids: Set[str],
+        actual_room_response_map: Dict[str, SlidingSyncResult.RoomResult],
+        to_token: StreamToken,
+        from_token: Optional[SlidingSyncStreamToken],
+    ) -> SlidingSyncResult.Extensions:
+        """Handle extension requests.
+
+        Args:
+            sync_config: Sync configuration
+            new_connection_state: Snapshot of the current per-connection state
+            new_per_connection_state: A mutable copy of the per-connection
+                state, used to record updates to the state during this request.
+            actual_lists: Sliding window API. A map of list key to list results in the
+                Sliding Sync response.
+            actual_room_ids: The actual room IDs in the the Sliding Sync response.
+            actual_room_response_map: A map of room ID to room results in the the
+                Sliding Sync response.
+            to_token: The point in the stream to sync up to.
+            from_token: The point in the stream to sync from.
+        """
+
+        if sync_config.extensions is None:
+            return SlidingSyncResult.Extensions()
+
+        to_device_response = None
+        if sync_config.extensions.to_device is not None:
+            to_device_response = await self.get_to_device_extension_response(
+                sync_config=sync_config,
+                to_device_request=sync_config.extensions.to_device,
+                to_token=to_token,
+            )
+
+        e2ee_response = None
+        if sync_config.extensions.e2ee is not None:
+            e2ee_response = await self.get_e2ee_extension_response(
+                sync_config=sync_config,
+                e2ee_request=sync_config.extensions.e2ee,
+                to_token=to_token,
+                from_token=from_token,
+            )
+
+        account_data_response = None
+        if sync_config.extensions.account_data is not None:
+            account_data_response = await self.get_account_data_extension_response(
+                sync_config=sync_config,
+                actual_lists=actual_lists,
+                actual_room_ids=actual_room_ids,
+                account_data_request=sync_config.extensions.account_data,
+                to_token=to_token,
+                from_token=from_token,
+            )
+
+        receipts_response = None
+        if sync_config.extensions.receipts is not None:
+            receipts_response = await self.get_receipts_extension_response(
+                sync_config=sync_config,
+                previous_connection_state=previous_connection_state,
+                new_connection_state=new_connection_state,
+                actual_lists=actual_lists,
+                actual_room_ids=actual_room_ids,
+                actual_room_response_map=actual_room_response_map,
+                receipts_request=sync_config.extensions.receipts,
+                to_token=to_token,
+                from_token=from_token,
+            )
+
+        typing_response = None
+        if sync_config.extensions.typing is not None:
+            typing_response = await self.get_typing_extension_response(
+                sync_config=sync_config,
+                actual_lists=actual_lists,
+                actual_room_ids=actual_room_ids,
+                actual_room_response_map=actual_room_response_map,
+                typing_request=sync_config.extensions.typing,
+                to_token=to_token,
+                from_token=from_token,
+            )
+
+        return SlidingSyncResult.Extensions(
+            to_device=to_device_response,
+            e2ee=e2ee_response,
+            account_data=account_data_response,
+            receipts=receipts_response,
+            typing=typing_response,
+        )
+
+    def find_relevant_room_ids_for_extension(
+        self,
+        requested_lists: Optional[List[str]],
+        requested_room_ids: Optional[List[str]],
+        actual_lists: Dict[str, SlidingSyncResult.SlidingWindowList],
+        actual_room_ids: Set[str],
+    ) -> Set[str]:
+        """
+        Handle the reserved `lists`/`rooms` keys for extensions. Extensions should only
+        return results for rooms in the Sliding Sync response. This matches up the
+        requested rooms/lists with the actual lists/rooms in the Sliding Sync response.
+
+        {"lists": []}                    // Do not process any lists.
+        {"lists": ["rooms", "dms"]}      // Process only a subset of lists.
+        {"lists": ["*"]}                 // Process all lists defined in the Sliding Window API. (This is the default.)
+
+        {"rooms": []}                    // Do not process any specific rooms.
+        {"rooms": ["!a:b", "!c:d"]}      // Process only a subset of room subscriptions.
+        {"rooms": ["*"]}                 // Process all room subscriptions defined in the Room Subscription API. (This is the default.)
+
+        Args:
+            requested_lists: The `lists` from the extension request.
+            requested_room_ids: The `rooms` from the extension request.
+            actual_lists: The actual lists from the Sliding Sync response.
+            actual_room_ids: The actual room subscriptions from the Sliding Sync request.
+        """
+
+        # We only want to include account data for rooms that are already in the sliding
+        # sync response AND that were requested in the account data request.
+        relevant_room_ids: Set[str] = set()
+
+        # See what rooms from the room subscriptions we should get account data for
+        if requested_room_ids is not None:
+            for room_id in requested_room_ids:
+                # A wildcard means we process all rooms from the room subscriptions
+                if room_id == "*":
+                    relevant_room_ids.update(actual_room_ids)
+                    break
+
+                if room_id in actual_room_ids:
+                    relevant_room_ids.add(room_id)
+
+        # See what rooms from the sliding window lists we should get account data for
+        if requested_lists is not None:
+            for list_key in requested_lists:
+                # Just some typing because we share the variable name in multiple places
+                actual_list: Optional[SlidingSyncResult.SlidingWindowList] = None
+
+                # A wildcard means we process rooms from all lists
+                if list_key == "*":
+                    for actual_list in actual_lists.values():
+                        # We only expect a single SYNC operation for any list
+                        assert len(actual_list.ops) == 1
+                        sync_op = actual_list.ops[0]
+                        assert sync_op.op == OperationType.SYNC
+
+                        relevant_room_ids.update(sync_op.room_ids)
+
+                    break
+
+                actual_list = actual_lists.get(list_key)
+                if actual_list is not None:
+                    # We only expect a single SYNC operation for any list
+                    assert len(actual_list.ops) == 1
+                    sync_op = actual_list.ops[0]
+                    assert sync_op.op == OperationType.SYNC
+
+                    relevant_room_ids.update(sync_op.room_ids)
+
+        return relevant_room_ids
+
+    @trace
+    async def get_to_device_extension_response(
+        self,
+        sync_config: SlidingSyncConfig,
+        to_device_request: SlidingSyncConfig.Extensions.ToDeviceExtension,
+        to_token: StreamToken,
+    ) -> Optional[SlidingSyncResult.Extensions.ToDeviceExtension]:
+        """Handle to-device extension (MSC3885)
+
+        Args:
+            sync_config: Sync configuration
+            to_device_request: The to-device extension from the request
+            to_token: The point in the stream to sync up to.
+        """
+        user_id = sync_config.user.to_string()
+        device_id = sync_config.requester.device_id
+
+        # Skip if the extension is not enabled
+        if not to_device_request.enabled:
+            return None
+
+        # Check that this request has a valid device ID (not all requests have
+        # to belong to a device, and so device_id is None)
+        if device_id is None:
+            return SlidingSyncResult.Extensions.ToDeviceExtension(
+                next_batch=f"{to_token.to_device_key}",
+                events=[],
+            )
+
+        since_stream_id = 0
+        if to_device_request.since is not None:
+            # We've already validated this is an int.
+            since_stream_id = int(to_device_request.since)
+
+            if to_token.to_device_key < since_stream_id:
+                # The since token is ahead of our current token, so we return an
+                # empty response.
+                logger.warning(
+                    "Got to-device.since from the future. since token: %r is ahead of our current to_device stream position: %r",
+                    since_stream_id,
+                    to_token.to_device_key,
+                )
+                return SlidingSyncResult.Extensions.ToDeviceExtension(
+                    next_batch=to_device_request.since,
+                    events=[],
+                )
+
+            # Delete everything before the given since token, as we know the
+            # device must have received them.
+            deleted = await self.store.delete_messages_for_device(
+                user_id=user_id,
+                device_id=device_id,
+                up_to_stream_id=since_stream_id,
+            )
+
+            logger.debug(
+                "Deleted %d to-device messages up to %d for %s",
+                deleted,
+                since_stream_id,
+                user_id,
+            )
+
+        messages, stream_id = await self.store.get_messages_for_device(
+            user_id=user_id,
+            device_id=device_id,
+            from_stream_id=since_stream_id,
+            to_stream_id=to_token.to_device_key,
+            limit=min(to_device_request.limit, 100),  # Limit to at most 100 events
+        )
+
+        return SlidingSyncResult.Extensions.ToDeviceExtension(
+            next_batch=f"{stream_id}",
+            events=messages,
+        )
+
+    @trace
+    async def get_e2ee_extension_response(
+        self,
+        sync_config: SlidingSyncConfig,
+        e2ee_request: SlidingSyncConfig.Extensions.E2eeExtension,
+        to_token: StreamToken,
+        from_token: Optional[SlidingSyncStreamToken],
+    ) -> Optional[SlidingSyncResult.Extensions.E2eeExtension]:
+        """Handle E2EE device extension (MSC3884)
+
+        Args:
+            sync_config: Sync configuration
+            e2ee_request: The e2ee extension from the request
+            to_token: The point in the stream to sync up to.
+            from_token: The point in the stream to sync from.
+        """
+        user_id = sync_config.user.to_string()
+        device_id = sync_config.requester.device_id
+
+        # Skip if the extension is not enabled
+        if not e2ee_request.enabled:
+            return None
+
+        device_list_updates: Optional[DeviceListUpdates] = None
+        if from_token is not None:
+            # TODO: This should take into account the `from_token` and `to_token`
+            device_list_updates = await self.device_handler.get_user_ids_changed(
+                user_id=user_id,
+                from_token=from_token.stream_token,
+            )
+
+        device_one_time_keys_count: Mapping[str, int] = {}
+        device_unused_fallback_key_types: Sequence[str] = []
+        if device_id:
+            # TODO: We should have a way to let clients differentiate between the states of:
+            #   * no change in OTK count since the provided since token
+            #   * the server has zero OTKs left for this device
+            #  Spec issue: https://github.com/matrix-org/matrix-doc/issues/3298
+            device_one_time_keys_count = await self.store.count_e2e_one_time_keys(
+                user_id, device_id
+            )
+            device_unused_fallback_key_types = (
+                await self.store.get_e2e_unused_fallback_key_types(user_id, device_id)
+            )
+
+        return SlidingSyncResult.Extensions.E2eeExtension(
+            device_list_updates=device_list_updates,
+            device_one_time_keys_count=device_one_time_keys_count,
+            device_unused_fallback_key_types=device_unused_fallback_key_types,
+        )
+
+    @trace
+    async def get_account_data_extension_response(
+        self,
+        sync_config: SlidingSyncConfig,
+        actual_lists: Dict[str, SlidingSyncResult.SlidingWindowList],
+        actual_room_ids: Set[str],
+        account_data_request: SlidingSyncConfig.Extensions.AccountDataExtension,
+        to_token: StreamToken,
+        from_token: Optional[SlidingSyncStreamToken],
+    ) -> Optional[SlidingSyncResult.Extensions.AccountDataExtension]:
+        """Handle Account Data extension (MSC3959)
+
+        Args:
+            sync_config: Sync configuration
+            actual_lists: Sliding window API. A map of list key to list results in the
+                Sliding Sync response.
+            actual_room_ids: The actual room IDs in the the Sliding Sync response.
+            account_data_request: The account_data extension from the request
+            to_token: The point in the stream to sync up to.
+            from_token: The point in the stream to sync from.
+        """
+        user_id = sync_config.user.to_string()
+
+        # Skip if the extension is not enabled
+        if not account_data_request.enabled:
+            return None
+
+        global_account_data_map: Mapping[str, JsonMapping] = {}
+        if from_token is not None:
+            # TODO: This should take into account the `from_token` and `to_token`
+            global_account_data_map = (
+                await self.store.get_updated_global_account_data_for_user(
+                    user_id, from_token.stream_token.account_data_key
+                )
+            )
+
+            have_push_rules_changed = await self.store.have_push_rules_changed_for_user(
+                user_id, from_token.stream_token.push_rules_key
+            )
+            if have_push_rules_changed:
+                global_account_data_map = dict(global_account_data_map)
+                # TODO: This should take into account the `from_token` and `to_token`
+                global_account_data_map[AccountDataTypes.PUSH_RULES] = (
+                    await self.push_rules_handler.push_rules_for_user(sync_config.user)
+                )
+        else:
+            # TODO: This should take into account the `to_token`
+            all_global_account_data = await self.store.get_global_account_data_for_user(
+                user_id
+            )
+
+            global_account_data_map = dict(all_global_account_data)
+            # TODO: This should take into account the  `to_token`
+            global_account_data_map[AccountDataTypes.PUSH_RULES] = (
+                await self.push_rules_handler.push_rules_for_user(sync_config.user)
+            )
+
+        # Fetch room account data
+        account_data_by_room_map: Mapping[str, Mapping[str, JsonMapping]] = {}
+        relevant_room_ids = self.find_relevant_room_ids_for_extension(
+            requested_lists=account_data_request.lists,
+            requested_room_ids=account_data_request.rooms,
+            actual_lists=actual_lists,
+            actual_room_ids=actual_room_ids,
+        )
+        if len(relevant_room_ids) > 0:
+            if from_token is not None:
+                # TODO: This should take into account the `from_token` and `to_token`
+                account_data_by_room_map = (
+                    await self.store.get_updated_room_account_data_for_user(
+                        user_id, from_token.stream_token.account_data_key
+                    )
+                )
+            else:
+                # TODO: This should take into account the `to_token`
+                account_data_by_room_map = (
+                    await self.store.get_room_account_data_for_user(user_id)
+                )
+
+        # Filter down to the relevant rooms
+        account_data_by_room_map = {
+            room_id: account_data_map
+            for room_id, account_data_map in account_data_by_room_map.items()
+            if room_id in relevant_room_ids
+        }
+
+        return SlidingSyncResult.Extensions.AccountDataExtension(
+            global_account_data_map=global_account_data_map,
+            account_data_by_room_map=account_data_by_room_map,
+        )
+
+    @trace
+    async def get_receipts_extension_response(
+        self,
+        sync_config: SlidingSyncConfig,
+        previous_connection_state: "PerConnectionState",
+        new_connection_state: "MutablePerConnectionState",
+        actual_lists: Dict[str, SlidingSyncResult.SlidingWindowList],
+        actual_room_ids: Set[str],
+        actual_room_response_map: Dict[str, SlidingSyncResult.RoomResult],
+        receipts_request: SlidingSyncConfig.Extensions.ReceiptsExtension,
+        to_token: StreamToken,
+        from_token: Optional[SlidingSyncStreamToken],
+    ) -> Optional[SlidingSyncResult.Extensions.ReceiptsExtension]:
+        """Handle Receipts extension (MSC3960)
+
+        Args:
+            sync_config: Sync configuration
+            previous_connection_state: The current per-connection state
+            new_connection_state: A mutable copy of the per-connection
+                state, used to record updates to the state.
+            actual_lists: Sliding window API. A map of list key to list results in the
+                Sliding Sync response.
+            actual_room_ids: The actual room IDs in the the Sliding Sync response.
+            actual_room_response_map: A map of room ID to room results in the the
+                Sliding Sync response.
+            account_data_request: The account_data extension from the request
+            to_token: The point in the stream to sync up to.
+            from_token: The point in the stream to sync from.
+        """
+        # Skip if the extension is not enabled
+        if not receipts_request.enabled:
+            return None
+
+        relevant_room_ids = self.find_relevant_room_ids_for_extension(
+            requested_lists=receipts_request.lists,
+            requested_room_ids=receipts_request.rooms,
+            actual_lists=actual_lists,
+            actual_room_ids=actual_room_ids,
+        )
+
+        room_id_to_receipt_map: Dict[str, JsonMapping] = {}
+        if len(relevant_room_ids) > 0:
+            # We need to handle the different cases depending on if we have sent
+            # down receipts previously or not, so we split the relevant rooms
+            # up into different collections based on status.
+            live_rooms = set()
+            previously_rooms: Dict[str, MultiWriterStreamToken] = {}
+            initial_rooms = set()
+
+            for room_id in relevant_room_ids:
+                if not from_token:
+                    initial_rooms.add(room_id)
+                    continue
+
+                # If we're sending down the room from scratch again for some reason, we
+                # should always resend the receipts as well (regardless of if
+                # we've sent them down before). This is to mimic the behaviour
+                # of what happens on initial sync, where you get a chunk of
+                # timeline with all of the corresponding receipts for the events in the timeline.
+                room_result = actual_room_response_map.get(room_id)
+                if room_result is not None and room_result.initial:
+                    initial_rooms.add(room_id)
+                    continue
+
+                room_status = previous_connection_state.receipts.have_sent_room(room_id)
+                if room_status.status == HaveSentRoomFlag.LIVE:
+                    live_rooms.add(room_id)
+                elif room_status.status == HaveSentRoomFlag.PREVIOUSLY:
+                    assert room_status.last_token is not None
+                    previously_rooms[room_id] = room_status.last_token
+                elif room_status.status == HaveSentRoomFlag.NEVER:
+                    initial_rooms.add(room_id)
+                else:
+                    assert_never(room_status.status)
+
+            # The set of receipts that we fetched. Private receipts need to be
+            # filtered out before returning.
+            fetched_receipts = []
+
+            # For live rooms we just fetch all receipts in those rooms since the
+            # `since` token.
+            if live_rooms:
+                assert from_token is not None
+                receipts = await self.store.get_linearized_receipts_for_rooms(
+                    room_ids=live_rooms,
+                    from_key=from_token.stream_token.receipt_key,
+                    to_key=to_token.receipt_key,
+                )
+                fetched_receipts.extend(receipts)
+
+            # For rooms we've previously sent down, but aren't up to date, we
+            # need to use the from token from the room status.
+            if previously_rooms:
+                for room_id, receipt_token in previously_rooms.items():
+                    # TODO: Limit the number of receipts we're about to send down
+                    # for the room, if its too many we should TODO
+                    previously_receipts = (
+                        await self.store.get_linearized_receipts_for_room(
+                            room_id=room_id,
+                            from_key=receipt_token,
+                            to_key=to_token.receipt_key,
+                        )
+                    )
+                    fetched_receipts.extend(previously_receipts)
+
+            # For rooms we haven't previously sent down, we could send all receipts
+            # from that room but we only want to include receipts for events
+            # in the timeline to avoid bloating and blowing up the sync response
+            # as the number of users in the room increases. (this behavior is part of the spec)
+            initial_rooms_and_event_ids = [
+                (room_id, event.event_id)
+                for room_id in initial_rooms
+                if room_id in actual_room_response_map
+                for event in actual_room_response_map[room_id].timeline_events
+            ]
+            if initial_rooms_and_event_ids:
+                initial_receipts = await self.store.get_linearized_receipts_for_events(
+                    room_and_event_ids=initial_rooms_and_event_ids,
+                )
+                fetched_receipts.extend(initial_receipts)
+
+            fetched_receipts = ReceiptEventSource.filter_out_private_receipts(
+                fetched_receipts, sync_config.user.to_string()
+            )
+
+            for receipt in fetched_receipts:
+                # These fields should exist for every receipt
+                room_id = receipt["room_id"]
+                type = receipt["type"]
+                content = receipt["content"]
+
+                room_id_to_receipt_map[room_id] = {"type": type, "content": content}
+
+        # Now we update the per-connection state to track which receipts we have
+        # and haven't sent down.
+        new_connection_state.receipts.record_sent_rooms(relevant_room_ids)
+
+        if from_token:
+            # Now find the set of rooms that may have receipts that we're not sending
+            # down. We only need to check rooms that we have previously returned
+            # receipts for (in `previous_connection_state`) because we only care about
+            # updating `LIVE` rooms to `PREVIOUSLY`. The `PREVIOUSLY` rooms will just
+            # stay pointing at their previous position so we don't need to waste time
+            # checking those and since we default to `NEVER`, rooms that were `NEVER`
+            # sent before don't need to be recorded as we'll handle them correctly when
+            # they come into range for the first time.
+            rooms_no_receipts = [
+                room_id
+                for room_id, room_status in previous_connection_state.receipts._statuses.items()
+                if room_status.status == HaveSentRoomFlag.LIVE
+                and room_id not in relevant_room_ids
+            ]
+            changed_rooms = await self.store.get_rooms_with_receipts_between(
+                rooms_no_receipts,
+                from_key=from_token.stream_token.receipt_key,
+                to_key=to_token.receipt_key,
+            )
+            new_connection_state.receipts.record_unsent_rooms(
+                changed_rooms, from_token.stream_token.receipt_key
+            )
+
+        return SlidingSyncResult.Extensions.ReceiptsExtension(
+            room_id_to_receipt_map=room_id_to_receipt_map,
+        )
+
+    async def get_typing_extension_response(
+        self,
+        sync_config: SlidingSyncConfig,
+        actual_lists: Dict[str, SlidingSyncResult.SlidingWindowList],
+        actual_room_ids: Set[str],
+        actual_room_response_map: Dict[str, SlidingSyncResult.RoomResult],
+        typing_request: SlidingSyncConfig.Extensions.TypingExtension,
+        to_token: StreamToken,
+        from_token: Optional[SlidingSyncStreamToken],
+    ) -> Optional[SlidingSyncResult.Extensions.TypingExtension]:
+        """Handle Typing Notification extension (MSC3961)
+
+        Args:
+            sync_config: Sync configuration
+            actual_lists: Sliding window API. A map of list key to list results in the
+                Sliding Sync response.
+            actual_room_ids: The actual room IDs in the the Sliding Sync response.
+            actual_room_response_map: A map of room ID to room results in the the
+                Sliding Sync response.
+            account_data_request: The account_data extension from the request
+            to_token: The point in the stream to sync up to.
+            from_token: The point in the stream to sync from.
+        """
+        # Skip if the extension is not enabled
+        if not typing_request.enabled:
+            return None
+
+        relevant_room_ids = self.find_relevant_room_ids_for_extension(
+            requested_lists=typing_request.lists,
+            requested_room_ids=typing_request.rooms,
+            actual_lists=actual_lists,
+            actual_room_ids=actual_room_ids,
+        )
+
+        room_id_to_typing_map: Dict[str, JsonMapping] = {}
+        if len(relevant_room_ids) > 0:
+            # Note: We don't need to take connection tracking into account for typing
+            # notifications because they'll get anything still relevant and hasn't timed
+            # out when the room comes into range. We consider the gap where the room
+            # fell out of range, as long enough for any typing notifications to have
+            # timed out (it's not worth the 30 seconds of data we may have missed).
+            typing_source = self.event_sources.sources.typing
+            typing_notifications, _ = await typing_source.get_new_events(
+                user=sync_config.user,
+                from_key=(from_token.stream_token.typing_key if from_token else 0),
+                to_key=to_token.typing_key,
+                # This is a dummy value and isn't used in the function
+                limit=0,
+                room_ids=relevant_room_ids,
+                is_guest=False,
+            )
+
+            for typing_notification in typing_notifications:
+                # These fields should exist for every typing notification
+                room_id = typing_notification["room_id"]
+                type = typing_notification["type"]
+                content = typing_notification["content"]
+
+                room_id_to_typing_map[room_id] = {"type": type, "content": content}
+
+        return SlidingSyncResult.Extensions.TypingExtension(
+            room_id_to_typing_map=room_id_to_typing_map,
+        )
@@ -0,0 +1,123 @@
+#
+# This file is licensed under the Affero General Public License (AGPL) version 3.
+#
+# Copyright (C) 2023 New Vector, Ltd
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# See the GNU Affero General Public License for more details:
+# <https://www.gnu.org/licenses/agpl-3.0.html>.
+#
+
+import logging
+from typing import TYPE_CHECKING, Optional
+
+import attr
+
+from synapse.logging.opentracing import trace
+from synapse.storage.databases.main import DataStore
+from synapse.types import SlidingSyncStreamToken
+from synapse.types.handlers.sliding_sync import (
+    MutablePerConnectionState,
+    PerConnectionState,
+    SlidingSyncConfig,
+)
+
+if TYPE_CHECKING:
+    pass
+
+logger = logging.getLogger(__name__)
+
+
+@attr.s(auto_attribs=True)
+class SlidingSyncConnectionStore:
+    """In-memory store of per-connection state, including what rooms we have
+    previously sent down a sliding sync connection.
+
+    Note: This is NOT safe to run in a worker setup because connection positions will
+    point to different sets of rooms on different workers. e.g. for the same connection,
+    a connection position of 5 might have totally different states on worker A and
+    worker B.
+
+    One complication that we need to deal with here is needing to handle requests being
+    resent, i.e. if we sent down a room in a response that the client received, we must
+    consider the room *not* sent when we get the request again.
+
+    This is handled by using an integer "token", which is returned to the client
+    as part of the sync token. For each connection we store a mapping from
+    tokens to the room states, and create a new entry when we send down new
+    rooms.
+
+    Note that for any given sliding sync connection we will only store a maximum
+    of two different tokens: the previous token from the request and a new token
+    sent in the response. When we receive a request with a given token, we then
+    clear out all other entries with a different token.
+
+    Attributes:
+        _connections: Mapping from `(user_id, conn_id)` to mapping of `token`
+            to mapping of room ID to `HaveSentRoom`.
+    """
+
+    store: "DataStore"
+
+    async def get_per_connection_state(
+        self,
+        sync_config: SlidingSyncConfig,
+        from_token: Optional[SlidingSyncStreamToken],
+    ) -> PerConnectionState:
+        """Fetch the per-connection state for the token.
+
+        Raises:
+            SlidingSyncUnknownPosition if the connection_token is unknown
+        """
+        if from_token is None or from_token.connection_position == 0:
+            return PerConnectionState()
+
+        conn_id = sync_config.conn_id or ""
+
+        device_id = sync_config.requester.device_id
+        assert device_id is not None
+
+        return await self.store.get_per_connection_state(
+            sync_config.user.to_string(),
+            device_id,
+            conn_id,
+            from_token.connection_position,
+        )
+
+    @trace
+    async def record_new_state(
+        self,
+        sync_config: SlidingSyncConfig,
+        from_token: Optional[SlidingSyncStreamToken],
+        new_connection_state: MutablePerConnectionState,
+    ) -> int:
+        """Record updated per-connection state, returning the connection
+        position associated with the new state.
+        If there are no changes to the state this may return the same token as
+        the existing per-connection state.
+        """
+        if not new_connection_state.has_updates():
+            if from_token is not None:
+                return from_token.connection_position
+            else:
+                return 0
+
+        if from_token is not None and from_token.connection_position == 0:
+            from_token = None
+
+        conn_id = sync_config.conn_id or ""
+
+        device_id = sync_config.requester.device_id
+        assert device_id is not None
+
+        return await self.store.persist_per_connection_state(
+            sync_config.user.to_string(),
+            device_id,
+            conn_id,
+            from_token.connection_position if from_token else None,
+            new_connection_state,
+        )
@@ -293,7 +293,9 @@ class StatsHandler:
                    "history_visibility"
                )
            elif delta.event_type == EventTypes.RoomEncryption:
-                room_state["encryption"] = event_content.get("algorithm")
+                room_state["encryption"] = event_content.get(
+                    EventContentFields.ENCRYPTION_ALGORITHM
+                )
            elif delta.event_type == EventTypes.Name:
                room_state["name"] = event_content.get("name")
            elif delta.event_type == EventTypes.Topic:
@@ -43,6 +43,7 @@ from prometheus_client import Counter

 from synapse.api.constants import (
    AccountDataTypes,
+    Direction,
    EventContentFields,
    EventTypes,
    JoinRules,
@@ -64,6 +65,7 @@ from synapse.logging.opentracing import (
 )
 from synapse.storage.databases.main.event_push_actions import RoomNotifCounts
 from synapse.storage.databases.main.roommember import extract_heroes_from_room_summary
+from synapse.storage.databases.main.stream import PaginateFunction
 from synapse.storage.roommember import MemberSummary
 from synapse.types import (
    DeviceListUpdates,
@@ -84,7 +86,7 @@ from synapse.util.async_helpers import concurrently_execute
 from synapse.util.caches.expiringcache import ExpiringCache
 from synapse.util.caches.lrucache import LruCache
 from synapse.util.caches.response_cache import ResponseCache, ResponseCacheContext
-from synapse.util.metrics import Measure, measure_func
+from synapse.util.metrics import Measure
 from synapse.visibility import filter_events_for_client

 if TYPE_CHECKING:
@@ -879,22 +881,49 @@ class SyncHandler:
                since_key = since_token.room_key

            while limited and len(recents) < timeline_limit and max_repeat:
-                # If we have a since_key then we are trying to get any events
-                # that have happened since `since_key` up to `end_key`, so we
-                # can just use `get_room_events_stream_for_room`.
-                # Otherwise, we want to return the last N events in the room
-                # in topological ordering.
-                if since_key:
-                    events, end_key = await self.store.get_room_events_stream_for_room(
-                        room_id,
-                        limit=load_limit + 1,
-                        from_key=since_key,
-                        to_key=end_key,
-                    )
-                else:
-                    events, end_key = await self.store.get_recent_events_for_room(
-                        room_id, limit=load_limit + 1, end_token=end_key
-                    )
+                # For initial `/sync`, we want to view a historical section of the
+                # timeline; to fetch events by `topological_ordering` (best
+                # representation of the room DAG as others were seeing it at the time).
+                # This also aligns with the order that `/messages` returns events in.
+                #
+                # For incremental `/sync`, we want to get all updates for rooms since
+                # the last `/sync` (regardless if those updates arrived late or happened
+                # a while ago in the past); to fetch events by `stream_ordering` (in the
+                # order they were received by the server).
+                #
+                # Relevant spec issue: https://github.com/matrix-org/matrix-spec/issues/1917
+                #
+                # FIXME: Using workaround for mypy,
+                # https://github.com/python/mypy/issues/10740#issuecomment-1997047277 and
+                # https://github.com/python/mypy/issues/17479
+                paginate_room_events_by_topological_ordering: PaginateFunction = (
+                    self.store.paginate_room_events_by_topological_ordering
+                )
+                paginate_room_events_by_stream_ordering: PaginateFunction = (
+                    self.store.paginate_room_events_by_stream_ordering
+                )
+                pagination_method: PaginateFunction = (
+                    # Use `topographical_ordering` for historical events
+                    paginate_room_events_by_topological_ordering
+                    if since_key is None
+                    # Use `stream_ordering` for updates
+                    else paginate_room_events_by_stream_ordering
+                )
+                events, end_key = await pagination_method(
+                    room_id=room_id,
+                    # The bounds are reversed so we can paginate backwards
+                    # (from newer to older events) starting at to_bound.
+                    # This ensures we fill the `limit` with the newest events first,
+                    from_key=end_key,
+                    to_key=since_key,
+                    direction=Direction.BACKWARDS,
+                    # We add one so we can determine if there are enough events to saturate
+                    # the limit or not (see `limited`)
+                    limit=load_limit + 1,
+                )
+                # We want to return the events in ascending order (the last event is the
+                # most recent).
+                events.reverse()

                log_kv({"loaded_recents": len(events)})

@@ -1352,7 +1381,7 @@ class SyncHandler:
            await_full_state = True
            lazy_load_members = False

-        state_at_timeline_end = await self._state_storage_controller.get_state_at(
+        state_at_timeline_end = await self._state_storage_controller.get_state_ids_at(
            room_id,
            stream_position=end_token,
            state_filter=state_filter,
@@ -1480,11 +1509,13 @@ class SyncHandler:
        else:
            # We can get here if the user has ignored the senders of all
            # the recent events.
-            state_at_timeline_start = await self._state_storage_controller.get_state_at(
-                room_id,
-                stream_position=end_token,
-                state_filter=state_filter,
-                await_full_state=await_full_state,
+            state_at_timeline_start = (
+                await self._state_storage_controller.get_state_ids_at(
+                    room_id,
+                    stream_position=end_token,
+                    state_filter=state_filter,
+                    await_full_state=await_full_state,
+                )
            )

        if batch.limited:
@@ -1502,14 +1533,14 @@ class SyncHandler:
            # about them).
            state_filter = StateFilter.all()

-        state_at_previous_sync = await self._state_storage_controller.get_state_at(
+        state_at_previous_sync = await self._state_storage_controller.get_state_ids_at(
            room_id,
            stream_position=since_token,
            state_filter=state_filter,
            await_full_state=await_full_state,
        )

-        state_at_timeline_end = await self._state_storage_controller.get_state_at(
+        state_at_timeline_end = await self._state_storage_controller.get_state_ids_at(
            room_id,
            stream_position=end_token,
            state_filter=state_filter,
@@ -1748,8 +1779,15 @@ class SyncHandler:
                    )

                if include_device_list_updates:
-                    device_lists = await self._generate_sync_entry_for_device_list(
-                        sync_result_builder,
+                    # include_device_list_updates can only be True if we have a
+                    # since token.
+                    assert since_token is not None
+
+                    device_lists = await self._device_handler.generate_sync_entry_for_device_list(
+                        user_id=user_id,
+                        since_token=since_token,
+                        now_token=sync_result_builder.now_token,
+                        joined_room_ids=sync_result_builder.joined_room_ids,
                        newly_joined_rooms=newly_joined_rooms,
                        newly_joined_or_invited_or_knocked_users=newly_joined_or_invited_or_knocked_users,
                        newly_left_rooms=newly_left_rooms,
@@ -1861,8 +1899,14 @@ class SyncHandler:
                newly_left_users,
            ) = sync_result_builder.calculate_user_changes()

-            device_lists = await self._generate_sync_entry_for_device_list(
-                sync_result_builder,
+            # include_device_list_updates can only be True if we have a
+            # since token.
+            assert since_token is not None
+            device_lists = await self._device_handler.generate_sync_entry_for_device_list(
+                user_id=user_id,
+                since_token=since_token,
+                now_token=sync_result_builder.now_token,
+                joined_room_ids=sync_result_builder.joined_room_ids,
                newly_joined_rooms=newly_joined_rooms,
                newly_joined_or_invited_or_knocked_users=newly_joined_or_invited_or_knocked_users,
                newly_left_rooms=newly_left_rooms,
@@ -2039,94 +2083,6 @@ class SyncHandler:

        return sync_result_builder

-    @measure_func("_generate_sync_entry_for_device_list")
-    async def _generate_sync_entry_for_device_list(
-        self,
-        sync_result_builder: "SyncResultBuilder",
-        newly_joined_rooms: AbstractSet[str],
-        newly_joined_or_invited_or_knocked_users: AbstractSet[str],
-        newly_left_rooms: AbstractSet[str],
-        newly_left_users: AbstractSet[str],
-    ) -> DeviceListUpdates:
-        """Generate the DeviceListUpdates section of sync
-
-        Args:
-            sync_result_builder
-            newly_joined_rooms: Set of rooms user has joined since previous sync
-            newly_joined_or_invited_or_knocked_users: Set of users that have joined,
-                been invited to a room or are knocking on a room since
-                previous sync.
-            newly_left_rooms: Set of rooms user has left since previous sync
-            newly_left_users: Set of users that have left a room we're in since
-                previous sync
-        """
-
-        user_id = sync_result_builder.sync_config.user.to_string()
-        since_token = sync_result_builder.since_token
-        assert since_token is not None
-
-        # Take a copy since these fields will be mutated later.
-        newly_joined_or_invited_or_knocked_users = set(
-            newly_joined_or_invited_or_knocked_users
-        )
-        newly_left_users = set(newly_left_users)
-
-        # We want to figure out what user IDs the client should refetch
-        # device keys for, and which users we aren't going to track changes
-        # for anymore.
-        #
-        # For the first step we check:
-        #   a. if any users we share a room with have updated their devices,
-        #      and
-        #   b. we also check if we've joined any new rooms, or if a user has
-        #      joined a room we're in.
-        #
-        # For the second step we just find any users we no longer share a
-        # room with by looking at all users that have left a room plus users
-        # that were in a room we've left.
-
-        users_that_have_changed = set()
-
-        joined_room_ids = sync_result_builder.joined_room_ids
-
-        # Step 1a, check for changes in devices of users we share a room
-        # with
-        users_that_have_changed = (
-            await self._device_handler.get_device_changes_in_shared_rooms(
-                user_id,
-                joined_room_ids,
-                from_token=since_token,
-                now_token=sync_result_builder.now_token,
-            )
-        )
-
-        # Step 1b, check for newly joined rooms
-        for room_id in newly_joined_rooms:
-            joined_users = await self.store.get_users_in_room(room_id)
-            newly_joined_or_invited_or_knocked_users.update(joined_users)
-
-        # TODO: Check that these users are actually new, i.e. either they
-        # weren't in the previous sync *or* they left and rejoined.
-        users_that_have_changed.update(newly_joined_or_invited_or_knocked_users)
-
-        user_signatures_changed = await self.store.get_users_whose_signatures_changed(
-            user_id, since_token.device_list_key
-        )
-        users_that_have_changed.update(user_signatures_changed)
-
-        # Now find users that we no longer track
-        for room_id in newly_left_rooms:
-            left_users = await self.store.get_users_in_room(room_id)
-            newly_left_users.update(left_users)
-
-        # Remove any users that we still share a room with.
-        left_users_rooms = await self.store.get_rooms_for_users(newly_left_users)
-        for user_id, entries in left_users_rooms.items():
-            if any(rid in joined_room_ids for rid in entries):
-                newly_left_users.discard(user_id)
-
-        return DeviceListUpdates(changed=users_that_have_changed, left=newly_left_users)
-
    @trace
    async def _generate_sync_entry_for_to_device(
        self, sync_result_builder: "SyncResultBuilder"
@@ -2268,7 +2224,11 @@ class SyncHandler:
            user=user,
            from_key=presence_key,
            is_guest=sync_config.is_guest,
-            include_offline=include_offline,
+            include_offline=(
+                True
+                if self.hs_config.server.presence_include_offline_users_on_sync
+                else include_offline
+            ),
        )
        assert presence_key
        sync_result_builder.now_token = now_token.copy_and_replace(
@@ -2508,7 +2468,7 @@ class SyncHandler:
                continue

            if room_id in sync_result_builder.joined_room_ids or has_join:
-                old_state_ids = await self._state_storage_controller.get_state_at(
+                old_state_ids = await self._state_storage_controller.get_state_ids_at(
                    room_id,
                    since_token,
                    state_filter=StateFilter.from_types([(EventTypes.Member, user_id)]),
@@ -2539,7 +2499,7 @@ class SyncHandler:
                else:
                    if not old_state_ids:
                        old_state_ids = (
-                            await self._state_storage_controller.get_state_at(
+                            await self._state_storage_controller.get_state_ids_at(
                                room_id,
                                since_token,
                                state_filter=StateFilter.from_types(
@@ -2635,9 +2595,10 @@ class SyncHandler:
        # a "gap" in the timeline, as described by the spec for /sync.
        room_to_events = await self.store.get_room_events_stream_for_rooms(
            room_ids=sync_result_builder.joined_room_ids,
-            from_key=since_token.room_key,
-            to_key=now_token.room_key,
+            from_key=now_token.room_key,
+            to_key=since_token.room_key,
            limit=timeline_limit + 1,
+            direction=Direction.BACKWARDS,
        )

        # We loop through all room ids, even if there are no new events, in case
@@ -2648,6 +2609,9 @@ class SyncHandler:
            newly_joined = room_id in newly_joined_rooms
            if room_entry:
                events, start_key = room_entry
+                # We want to return the events in ascending order (the last event is the
+                # most recent).
+                events.reverse()

                prev_batch_token = now_token.copy_and_replace(
                    StreamKeyType.ROOM, start_key
@@ -565,7 +565,12 @@ class TypingNotificationEventSource(EventSource[int, JsonMapping]):
        room_ids: Iterable[str],
        is_guest: bool,
        explicit_room_id: Optional[str] = None,
+        to_key: Optional[int] = None,
    ) -> Tuple[List[JsonMapping], int]:
+        """
+        Find typing notifications for given rooms (> `from_token` and <= `to_token`)
+        """
+
        with Measure(self.clock, "typing.get_new_events"):
            from_key = int(from_key)
            handler = self.get_typing_handler()
@@ -574,7 +579,9 @@ class TypingNotificationEventSource(EventSource[int, JsonMapping]):
            for room_id in room_ids:
                if room_id not in handler._room_serials:
                    continue
-                if handler._room_serials[room_id] <= from_key:
+                if handler._room_serials[room_id] <= from_key or (
+                    to_key is not None and handler._room_serials[room_id] > to_key
+                ):
                    continue

                events.append(self._make_event_for(room_id))
@@ -1057,11 +1057,11 @@ class _MultipartParserProtocol(protocol.Protocol):
        if not self.parser:

            def on_header_field(data: bytes, start: int, end: int) -> None:
-                if data[start:end] == b"Location":
+                if data[start:end].lower() == b"location":
                    self.has_redirect = True
-                if data[start:end] == b"Content-Disposition":
+                if data[start:end].lower() == b"content-disposition":
                    self.in_disposition = True
-                if data[start:end] == b"Content-Type":
+                if data[start:end].lower() == b"content-type":
                    self.in_content_type = True

            def on_header_value(data: bytes, start: int, end: int) -> None:
@@ -1088,7 +1088,6 @@ class _MultipartParserProtocol(protocol.Protocol):
                    return
                # otherwise we are in the file part
                else:
-                    logger.info("Writing multipart file data to stream")
                    try:
                        self.stream.write(data[start:end])
                    except Exception as e:
@@ -90,7 +90,7 @@ from synapse.logging.context import make_deferred_yieldable, run_in_background
 from synapse.logging.opentracing import set_tag, start_active_span, tags
 from synapse.types import JsonDict
 from synapse.util import json_decoder
-from synapse.util.async_helpers import AwakenableSleeper, timeout_deferred
+from synapse.util.async_helpers import AwakenableSleeper, Linearizer, timeout_deferred
 from synapse.util.metrics import Measure
 from synapse.util.stringutils import parse_and_validate_server_name

@@ -475,6 +475,8 @@ class MatrixFederationHttpClient:
            use_proxy=True,
        )

+        self.remote_download_linearizer = Linearizer("remote_download_linearizer", 6)
+
    def wake_destination(self, destination: str) -> None:
        """Called when the remote server may have come back online."""

@@ -1486,35 +1488,44 @@ class MatrixFederationHttpClient:
        )

        headers = dict(response.headers.getAllRawHeaders())
-
        expected_size = response.length
-        # if we don't get an expected length then use the max length
+
        if expected_size == UNKNOWN_LENGTH:
            expected_size = max_size
-            logger.debug(
-                f"File size unknown, assuming file is max allowable size: {max_size}"
-            )
+        else:
+            if int(expected_size) > max_size:
+                msg = "Requested file is too large > %r bytes" % (max_size,)
+                logger.warning(
+                    "{%s} [%s] %s",
+                    request.txn_id,
+                    request.destination,
+                    msg,
+                )
+                raise SynapseError(HTTPStatus.BAD_GATEWAY, msg, Codes.TOO_LARGE)

-        read_body, _ = await download_ratelimiter.can_do_action(
-            requester=None,
-            key=ip_address,
-            n_actions=expected_size,
-        )
-        if not read_body:
-            msg = "Requested file size exceeds ratelimits"
-            logger.warning(
-                "{%s} [%s] %s",
-                request.txn_id,
-                request.destination,
-                msg,
+            read_body, _ = await download_ratelimiter.can_do_action(
+                requester=None,
+                key=ip_address,
+                n_actions=expected_size,
            )
-            raise SynapseError(HTTPStatus.TOO_MANY_REQUESTS, msg, Codes.LIMIT_EXCEEDED)
+            if not read_body:
+                msg = "Requested file size exceeds ratelimits"
+                logger.warning(
+                    "{%s} [%s] %s",
+                    request.txn_id,
+                    request.destination,
+                    msg,
+                )
+                raise SynapseError(
+                    HTTPStatus.TOO_MANY_REQUESTS, msg, Codes.LIMIT_EXCEEDED
+                )

        try:
-            # add a byte of headroom to max size as function errs at >=
-            d = read_body_with_max_size(response, output_stream, expected_size + 1)
-            d.addTimeout(self.default_timeout_seconds, self.reactor)
-            length = await make_deferred_yieldable(d)
+            async with self.remote_download_linearizer.queue(ip_address):
+                # add a byte of headroom to max size as function errs at >=
+                d = read_body_with_max_size(response, output_stream, expected_size + 1)
+                d.addTimeout(self.default_timeout_seconds, self.reactor)
+                length = await make_deferred_yieldable(d)
        except BodyExceededMaxSize:
            msg = "Requested file is too large > %r bytes" % (expected_size,)
            logger.warning(
@@ -1560,6 +1571,13 @@ class MatrixFederationHttpClient:
            request.method,
            request.uri.decode("ascii"),
        )
+
+        # if we didn't know the length upfront, decrement the actual size from ratelimiter
+        if response.length == UNKNOWN_LENGTH:
+            download_ratelimiter.record_action(
+                requester=None, key=ip_address, n_actions=length
+            )
+
        return length, headers

    async def federation_get_file(
@@ -1630,29 +1648,37 @@ class MatrixFederationHttpClient:
        )

        headers = dict(response.headers.getAllRawHeaders())
-
        expected_size = response.length
-        # if we don't get an expected length then use the max length
+
        if expected_size == UNKNOWN_LENGTH:
            expected_size = max_size
-            logger.debug(
-                f"File size unknown, assuming file is max allowable size: {max_size}"
-            )
+        else:
+            if int(expected_size) > max_size:
+                msg = "Requested file is too large > %r bytes" % (max_size,)
+                logger.warning(
+                    "{%s} [%s] %s",
+                    request.txn_id,
+                    request.destination,
+                    msg,
+                )
+                raise SynapseError(HTTPStatus.BAD_GATEWAY, msg, Codes.TOO_LARGE)

-        read_body, _ = await download_ratelimiter.can_do_action(
-            requester=None,
-            key=ip_address,
-            n_actions=expected_size,
-        )
-        if not read_body:
-            msg = "Requested file size exceeds ratelimits"
-            logger.warning(
-                "{%s} [%s] %s",
-                request.txn_id,
-                request.destination,
-                msg,
+            read_body, _ = await download_ratelimiter.can_do_action(
+                requester=None,
+                key=ip_address,
+                n_actions=expected_size,
            )
-            raise SynapseError(HTTPStatus.TOO_MANY_REQUESTS, msg, Codes.LIMIT_EXCEEDED)
+            if not read_body:
+                msg = "Requested file size exceeds ratelimits"
+                logger.warning(
+                    "{%s} [%s] %s",
+                    request.txn_id,
+                    request.destination,
+                    msg,
+                )
+                raise SynapseError(
+                    HTTPStatus.TOO_MANY_REQUESTS, msg, Codes.LIMIT_EXCEEDED
+                )

        # this should be a multipart/mixed response with the boundary string in the header
        try:
@@ -1672,11 +1698,12 @@ class MatrixFederationHttpClient:
            raise SynapseError(HTTPStatus.BAD_GATEWAY, msg)

        try:
-            # add a byte of headroom to max size as `_MultipartParserProtocol.dataReceived` errs at >=
-            deferred = read_multipart_response(
-                response, output_stream, boundary, expected_size + 1
-            )
-            deferred.addTimeout(self.default_timeout_seconds, self.reactor)
+            async with self.remote_download_linearizer.queue(ip_address):
+                # add a byte of headroom to max size as `_MultipartParserProtocol.dataReceived` errs at >=
+                deferred = read_multipart_response(
+                    response, output_stream, boundary, expected_size + 1
+                )
+                deferred.addTimeout(self.default_timeout_seconds, self.reactor)
        except BodyExceededMaxSize:
            msg = "Requested file is too large > %r bytes" % (expected_size,)
            logger.warning(
@@ -1743,6 +1770,13 @@ class MatrixFederationHttpClient:
            request.method,
            request.uri.decode("ascii"),
        )
+
+        # if we didn't know the length upfront, decrement the actual size from ratelimiter
+        if response.length == UNKNOWN_LENGTH:
+            download_ratelimiter.record_action(
+                requester=None, key=ip_address, n_actions=length
+            )
+
        return length, headers, multipart_response.json


@@ -62,6 +62,15 @@ HOP_BY_HOP_HEADERS = {
    "Upgrade",
 }

+if hasattr(Headers, "_canonicalNameCaps"):
+    # Twisted < 24.7.0rc1
+    _canonicalHeaderName = Headers()._canonicalNameCaps  # type: ignore[attr-defined]
+else:
+    # Twisted >= 24.7.0rc1
+    # But note that `_encodeName` still exists on prior versions,
+    # it just encodes differently
+    _canonicalHeaderName = Headers()._encodeName
+

 def parse_connection_header_value(
    connection_header_value: Optional[bytes],
@@ -85,11 +94,10 @@ def parse_connection_header_value(
        The set of header names that should not be copied over from the remote response.
        The keys are capitalized in canonical capitalization.
    """
-    headers = Headers()
    extra_headers_to_remove: Set[str] = set()
    if connection_header_value:
        extra_headers_to_remove = {
-            headers._canonicalNameCaps(connection_option.strip()).decode("ascii")
+            _canonicalHeaderName(connection_option.strip()).decode("ascii")
            for connection_option in connection_header_value.split(b",")
        }

@@ -658,7 +658,7 @@ class SynapseSite(ProxySite):
        )

        self.site_tag = site_tag
-        self.reactor = reactor
+        self.reactor: ISynapseReactor = reactor

        assert config.http_options is not None
        proxied = config.http_options.x_forwarded
@@ -683,7 +683,7 @@ class SynapseSite(ProxySite):
        self.access_logger = logging.getLogger(logger_name)
        self.server_version_string = server_version_string.encode("ascii")

-    def log(self, request: SynapseRequest) -> None:
+    def log(self, request: SynapseRequest) -> None:  # type: ignore[override]
        pass


@@ -28,6 +28,7 @@ from types import TracebackType
 from typing import (
    TYPE_CHECKING,
    Awaitable,
+    BinaryIO,
    Dict,
    Generator,
    List,
@@ -37,19 +38,28 @@ from typing import (
 )

 import attr
+from zope.interface import implementer

+from twisted.internet import interfaces
+from twisted.internet.defer import Deferred
 from twisted.internet.interfaces import IConsumer
-from twisted.protocols.basic import FileSender
+from twisted.python.failure import Failure
 from twisted.web.server import Request

 from synapse.api.errors import Codes, cs_error
 from synapse.http.server import finish_request, respond_with_json
 from synapse.http.site import SynapseRequest
-from synapse.logging.context import make_deferred_yieldable
+from synapse.logging.context import (
+    defer_to_threadpool,
+    make_deferred_yieldable,
+    run_in_background,
+)
 from synapse.util import Clock
+from synapse.util.async_helpers import DeferredEvent
 from synapse.util.stringutils import is_ascii

 if TYPE_CHECKING:
+    from synapse.server import HomeServer
    from synapse.storage.databases.main.media_repository import LocalMedia


@@ -122,6 +132,7 @@ def respond_404(request: SynapseRequest) -> None:


 async def respond_with_file(
+    hs: "HomeServer",
    request: SynapseRequest,
    media_type: str,
    file_path: str,
@@ -138,7 +149,7 @@ async def respond_with_file(
        add_file_headers(request, media_type, file_size, upload_name)

        with open(file_path, "rb") as f:
-            await make_deferred_yieldable(FileSender().beginFileTransfer(f, request))
+            await ThreadedFileSender(hs).beginFileTransfer(f, request)

        finish_request(request)
    else:
@@ -601,3 +612,151 @@ def _parseparam(s: bytes) -> Generator[bytes, None, None]:
        f = s[:end]
        yield f.strip()
        s = s[end:]
+
+
+@implementer(interfaces.IPushProducer)
+class ThreadedFileSender:
+    """
+    A producer that sends the contents of a file to a consumer, reading from the
+    file on a thread.
+
+    This works by having a loop in a threadpool repeatedly reading from the
+    file, until the consumer pauses the producer. There is then a loop in the
+    main thread that waits until the consumer resumes the producer and then
+    starts reading in the threadpool again.
+
+    This is done to ensure that we're never waiting in the threadpool, as
+    otherwise its easy to starve it of threads.
+    """
+
+    # How much data to read in one go.
+    CHUNK_SIZE = 2**14
+
+    # How long we wait for the consumer to be ready again before aborting the
+    # read.
+    TIMEOUT_SECONDS = 90.0
+
+    def __init__(self, hs: "HomeServer") -> None:
+        self.reactor = hs.get_reactor()
+        self.thread_pool = hs.get_media_sender_thread_pool()
+
+        self.file: Optional[BinaryIO] = None
+        self.deferred: "Deferred[None]" = Deferred()
+        self.consumer: Optional[interfaces.IConsumer] = None
+
+        # Signals if the thread should keep reading/sending data. Set means
+        # continue, clear means pause.
+        self.wakeup_event = DeferredEvent(self.reactor)
+
+        # Signals if the thread should terminate, e.g. because the consumer has
+        # gone away.
+        self.stop_writing = False
+
+    def beginFileTransfer(
+        self, file: BinaryIO, consumer: interfaces.IConsumer
+    ) -> "Deferred[None]":
+        """
+        Begin transferring a file
+        """
+        self.file = file
+        self.consumer = consumer
+
+        self.consumer.registerProducer(self, True)
+
+        # We set the wakeup signal as we should start producing immediately.
+        self.wakeup_event.set()
+        run_in_background(self.start_read_loop)
+
+        return make_deferred_yieldable(self.deferred)
+
+    def resumeProducing(self) -> None:
+        """interfaces.IPushProducer"""
+        self.wakeup_event.set()
+
+    def pauseProducing(self) -> None:
+        """interfaces.IPushProducer"""
+        self.wakeup_event.clear()
+
+    def stopProducing(self) -> None:
+        """interfaces.IPushProducer"""
+
+        # Unregister the consumer so we don't try and interact with it again.
+        if self.consumer:
+            self.consumer.unregisterProducer()
+
+        self.consumer = None
+
+        # Terminate the loop.
+        self.stop_writing = True
+        self.wakeup_event.set()
+
+        if not self.deferred.called:
+            self.deferred.errback(Exception("Consumer asked us to stop producing"))
+
+    async def start_read_loop(self) -> None:
+        """This is the loop that drives reading/writing"""
+        try:
+            while not self.stop_writing:
+                # Start the loop in the threadpool to read data.
+                more_data = await defer_to_threadpool(
+                    self.reactor, self.thread_pool, self._on_thread_read_loop
+                )
+                if not more_data:
+                    # Reached EOF, we can just return.
+                    return
+
+                if not self.wakeup_event.is_set():
+                    ret = await self.wakeup_event.wait(self.TIMEOUT_SECONDS)
+                    if not ret:
+                        raise Exception("Timed out waiting to resume")
+        except Exception:
+            self._error(Failure())
+        finally:
+            self._finish()
+
+    def _on_thread_read_loop(self) -> bool:
+        """This is the loop that happens on a thread.
+
+        Returns:
+            Whether there is more data to send.
+        """
+
+        while not self.stop_writing and self.wakeup_event.is_set():
+            # The file should always have been set before we get here.
+            assert self.file is not None
+
+            chunk = self.file.read(self.CHUNK_SIZE)
+            if not chunk:
+                return False
+
+            self.reactor.callFromThread(self._write, chunk)
+
+        return True
+
+    def _write(self, chunk: bytes) -> None:
+        """Called from the thread to write a chunk of data"""
+        if self.consumer:
+            self.consumer.write(chunk)
+
+    def _error(self, failure: Failure) -> None:
+        """Called when there was a fatal error"""
+        if self.consumer:
+            self.consumer.unregisterProducer()
+            self.consumer = None
+
+        if not self.deferred.called:
+            self.deferred.errback(failure)
+
+    def _finish(self) -> None:
+        """Called when we have finished writing (either on success or
+        failure)."""
+        if self.file:
+            self.file.close()
+            self.file = None
+
+        if self.consumer:
+            self.consumer.unregisterProducer()
+            self.consumer = None
+
+        if not self.deferred.called:
+            self.deferred.callback(None)
@@ -430,6 +430,7 @@ class MediaRepository:
        media_id: str,
        name: Optional[str],
        max_timeout_ms: int,
+        allow_authenticated: bool = True,
        federation: bool = False,
    ) -> None:
        """Responds to requests for local media, if exists, or returns 404.
@@ -442,6 +443,7 @@ class MediaRepository:
                the filename in the Content-Disposition header of the response.
            max_timeout_ms: the maximum number of milliseconds to wait for the
                media to be uploaded.
+            allow_authenticated: whether media marked as authenticated may be served to this request
            federation: whether the local media being fetched is for a federation request

        Returns:
@@ -451,6 +453,10 @@ class MediaRepository:
        if not media_info:
            return

+        if self.hs.config.media.enable_authenticated_media and not allow_authenticated:
+            if media_info.authenticated:
+                raise NotFoundError()
+
        self.mark_recently_accessed(None, media_id)

        media_type = media_info.media_type
@@ -481,6 +487,7 @@ class MediaRepository:
        max_timeout_ms: int,
        ip_address: str,
        use_federation_endpoint: bool,
+        allow_authenticated: bool = True,
    ) -> None:
        """Respond to requests for remote media.

@@ -495,6 +502,8 @@ class MediaRepository:
            ip_address: the IP address of the requester
            use_federation_endpoint: whether to request the remote media over the new
                federation `/download` endpoint
+            allow_authenticated: whether media marked as authenticated may be served to this
+                request

        Returns:
            Resolves once a response has successfully been written to request
@@ -526,6 +535,7 @@ class MediaRepository:
                self.download_ratelimiter,
                ip_address,
                use_federation_endpoint,
+                allow_authenticated,
            )

        # We deliberately stream the file outside the lock
@@ -542,7 +552,13 @@ class MediaRepository:
            respond_404(request)

    async def get_remote_media_info(
-        self, server_name: str, media_id: str, max_timeout_ms: int, ip_address: str
+        self,
+        server_name: str,
+        media_id: str,
+        max_timeout_ms: int,
+        ip_address: str,
+        use_federation: bool,
+        allow_authenticated: bool,
    ) -> RemoteMedia:
        """Gets the media info associated with the remote file, downloading
        if necessary.
@@ -553,6 +569,10 @@ class MediaRepository:
            max_timeout_ms: the maximum number of milliseconds to wait for the
                media to be uploaded.
            ip_address: IP address of the requester
+            use_federation: if a download is necessary, whether to request the remote file
+                over the federation `/download` endpoint
+            allow_authenticated: whether media marked as authenticated may be served to this
+                request

        Returns:
            The media info of the file
@@ -573,7 +593,8 @@ class MediaRepository:
                max_timeout_ms,
                self.download_ratelimiter,
                ip_address,
-                False,
+                use_federation,
+                allow_authenticated,
            )

        # Ensure we actually use the responder so that it releases resources
@@ -591,6 +612,7 @@ class MediaRepository:
        download_ratelimiter: Ratelimiter,
        ip_address: str,
        use_federation_endpoint: bool,
+        allow_authenticated: bool,
    ) -> Tuple[Optional[Responder], RemoteMedia]:
        """Looks for media in local cache, if not there then attempt to
        download from remote server.
@@ -612,6 +634,11 @@ class MediaRepository:
        """
        media_info = await self.store.get_cached_remote_media(server_name, media_id)

+        if self.hs.config.media.enable_authenticated_media and not allow_authenticated:
+            # if it isn't cached then don't fetch it or if it's authenticated then don't serve it
+            if not media_info or media_info.authenticated:
+                raise NotFoundError()
+
        # file_id is the ID we use to track the file locally. If we've already
        # seen the file then reuse the existing ID, otherwise generate a new
        # one.
@@ -785,6 +812,11 @@ class MediaRepository:

        logger.info("Stored remote media in file %r", fname)

+        if self.hs.config.media.enable_authenticated_media:
+            authenticated = True
+        else:
+            authenticated = False
+
        return RemoteMedia(
            media_origin=server_name,
            media_id=media_id,
@@ -795,6 +827,7 @@ class MediaRepository:
            filesystem_id=file_id,
            last_access_ts=time_now_ms,
            quarantined_by=None,
+            authenticated=authenticated,
        )

    async def _federation_download_remote_file(
@@ -908,6 +941,11 @@ class MediaRepository:

        logger.debug("Stored remote media in file %r", fname)

+        if self.hs.config.media.enable_authenticated_media:
+            authenticated = True
+        else:
+            authenticated = False
+
        return RemoteMedia(
            media_origin=server_name,
            media_id=media_id,
@@ -918,6 +956,7 @@ class MediaRepository:
            filesystem_id=file_id,
            last_access_ts=time_now_ms,
            quarantined_by=None,
+            authenticated=authenticated,
        )

    def _get_thumbnail_requirements(
@@ -1023,7 +1062,12 @@ class MediaRepository:
            t_len = os.path.getsize(output_path)

            await self.store.store_local_thumbnail(
-                media_id, t_width, t_height, t_type, t_method, t_len
+                media_id,
+                t_width,
+                t_height,
+                t_type,
+                t_method,
+                t_len,
            )

            return output_path
@@ -49,15 +49,11 @@ from zope.interface import implementer
 from twisted.internet import interfaces
 from twisted.internet.defer import Deferred
 from twisted.internet.interfaces import IConsumer
-from twisted.protocols.basic import FileSender

 from synapse.api.errors import NotFoundError
-from synapse.logging.context import (
-    defer_to_thread,
-    make_deferred_yieldable,
-    run_in_background,
-)
+from synapse.logging.context import defer_to_thread, run_in_background
 from synapse.logging.opentracing import start_active_span, trace, trace_with_opname
+from synapse.media._base import ThreadedFileSender
 from synapse.util import Clock
 from synapse.util.file_consumer import BackgroundFileConsumer

@@ -213,7 +209,7 @@ class MediaStorage:
            local_path = os.path.join(self.local_media_directory, path)
            if os.path.exists(local_path):
                logger.debug("responding with local file %s", local_path)
-                return FileResponder(open(local_path, "rb"))
+                return FileResponder(self.hs, open(local_path, "rb"))
            logger.debug("local file %s did not exist", local_path)

        for provider in self.storage_providers:
@@ -336,13 +332,12 @@ class FileResponder(Responder):
            is closed when finished streaming.
    """

-    def __init__(self, open_file: IO):
+    def __init__(self, hs: "HomeServer", open_file: BinaryIO):
+        self.hs = hs
        self.open_file = open_file

    def write_to_consumer(self, consumer: IConsumer) -> Deferred:
-        return make_deferred_yieldable(
-            FileSender().beginFileTransfer(self.open_file, consumer)
-        )
+        return ThreadedFileSender(self.hs).beginFileTransfer(self.open_file, consumer)

    def __exit__(
        self,
@@ -549,7 +544,7 @@ class MultipartFileConsumer:
        Calculate the content length of the multipart response
        in bytes.
        """
-        if not self.length:
+        if self.length is None:
            return None
        # calculate length of json field and content-type, disposition headers
        json_field = json.dumps(self.json_field)
@@ -145,6 +145,7 @@ class FileStorageProviderBackend(StorageProvider):

    def __init__(self, hs: "HomeServer", config: str):
        self.hs = hs
+        self.reactor = hs.get_reactor()
        self.cache_directory = hs.config.media.media_store_path
        self.base_directory = config

@@ -165,7 +166,7 @@ class FileStorageProviderBackend(StorageProvider):
        shutil_copyfile: Callable[[str, str], str] = shutil.copyfile
        with start_active_span("shutil_copyfile"):
            await defer_to_thread(
-                self.hs.get_reactor(),
+                self.reactor,
                shutil_copyfile,
                primary_fname,
                backup_fname,
@@ -177,7 +178,7 @@ class FileStorageProviderBackend(StorageProvider):

        backup_fname = os.path.join(self.base_directory, path)
        if os.path.isfile(backup_fname):
-            return FileResponder(open(backup_fname, "rb"))
+            return FileResponder(self.hs, open(backup_fname, "rb"))

        return None

@@ -26,7 +26,7 @@ from typing import TYPE_CHECKING, List, Optional, Tuple, Type

 from PIL import Image

-from synapse.api.errors import Codes, SynapseError, cs_error
+from synapse.api.errors import Codes, NotFoundError, SynapseError, cs_error
 from synapse.config.repository import THUMBNAIL_SUPPORTED_MEDIA_FORMAT_MAP
 from synapse.http.server import respond_with_json
 from synapse.http.site import SynapseRequest
@@ -36,9 +36,11 @@ from synapse.media._base import (
    ThumbnailInfo,
    respond_404,
    respond_with_file,
+    respond_with_multipart_responder,
    respond_with_responder,
 )
-from synapse.media.media_storage import MediaStorage
+from synapse.media.media_storage import FileResponder, MediaStorage
+from synapse.storage.databases.main.media_repository import LocalMedia

 if TYPE_CHECKING:
    from synapse.media.media_repository import MediaRepository
@@ -257,6 +259,7 @@ class ThumbnailProvider:
        media_storage: MediaStorage,
    ):
        self.hs = hs
+        self.reactor = hs.get_reactor()
        self.media_repo = media_repo
        self.media_storage = media_storage
        self.store = hs.get_datastores().main
@@ -271,6 +274,8 @@ class ThumbnailProvider:
        method: str,
        m_type: str,
        max_timeout_ms: int,
+        for_federation: bool,
+        allow_authenticated: bool = True,
    ) -> None:
        media_info = await self.media_repo.get_local_media_info(
            request, media_id, max_timeout_ms
@@ -278,6 +283,12 @@ class ThumbnailProvider:
        if not media_info:
            return

+        # if the media the thumbnail is generated from is authenticated, don't serve the
+        # thumbnail over an unauthenticated endpoint
+        if self.hs.config.media.enable_authenticated_media and not allow_authenticated:
+            if media_info.authenticated:
+                raise NotFoundError()
+
        thumbnail_infos = await self.store.get_local_media_thumbnails(media_id)
        await self._select_and_respond_with_thumbnail(
            request,
@@ -290,6 +301,8 @@ class ThumbnailProvider:
            media_id,
            url_cache=bool(media_info.url_cache),
            server_name=None,
+            for_federation=for_federation,
+            media_info=media_info,
        )

    async def select_or_generate_local_thumbnail(
@@ -301,14 +314,21 @@ class ThumbnailProvider:
        desired_method: str,
        desired_type: str,
        max_timeout_ms: int,
+        for_federation: bool,
+        allow_authenticated: bool = True,
    ) -> None:
        media_info = await self.media_repo.get_local_media_info(
            request, media_id, max_timeout_ms
        )
-
        if not media_info:
            return

+        # if the media the thumbnail is generated from is authenticated, don't serve the
+        # thumbnail over an unauthenticated endpoint
+        if self.hs.config.media.enable_authenticated_media and not allow_authenticated:
+            if media_info.authenticated:
+                raise NotFoundError()
+
        thumbnail_infos = await self.store.get_local_media_thumbnails(media_id)
        for info in thumbnail_infos:
            t_w = info.width == desired_width
@@ -326,10 +346,16 @@ class ThumbnailProvider:

                responder = await self.media_storage.fetch_media(file_info)
                if responder:
-                    await respond_with_responder(
-                        request, responder, info.type, info.length
-                    )
-                    return
+                    if for_federation:
+                        await respond_with_multipart_responder(
+                            self.hs.get_clock(), request, responder, media_info
+                        )
+                        return
+                    else:
+                        await respond_with_responder(
+                            request, responder, info.type, info.length
+                        )
+                        return

        logger.debug("We don't have a thumbnail of that size. Generating")

@@ -344,7 +370,15 @@ class ThumbnailProvider:
        )

        if file_path:
-            await respond_with_file(request, desired_type, file_path)
+            if for_federation:
+                await respond_with_multipart_responder(
+                    self.hs.get_clock(),
+                    request,
+                    FileResponder(self.hs, open(file_path, "rb")),
+                    media_info,
+                )
+            else:
+                await respond_with_file(self.hs, request, desired_type, file_path)
        else:
            logger.warning("Failed to generate thumbnail")
            raise SynapseError(400, "Failed to generate thumbnail.")
@@ -360,14 +394,28 @@ class ThumbnailProvider:
        desired_type: str,
        max_timeout_ms: int,
        ip_address: str,
+        use_federation: bool,
+        allow_authenticated: bool = True,
    ) -> None:
        media_info = await self.media_repo.get_remote_media_info(
-            server_name, media_id, max_timeout_ms, ip_address
+            server_name,
+            media_id,
+            max_timeout_ms,
+            ip_address,
+            use_federation,
+            allow_authenticated,
        )
        if not media_info:
            respond_404(request)
            return

+        # if the media the thumbnail is generated from is authenticated, don't serve the
+        # thumbnail over an unauthenticated endpoint
+        if self.hs.config.media.enable_authenticated_media and not allow_authenticated:
+            if media_info.authenticated:
+                respond_404(request)
+                return
+
        thumbnail_infos = await self.store.get_remote_media_thumbnails(
            server_name, media_id
        )
@@ -408,7 +456,7 @@ class ThumbnailProvider:
        )

        if file_path:
-            await respond_with_file(request, desired_type, file_path)
+            await respond_with_file(self.hs, request, desired_type, file_path)
        else:
            logger.warning("Failed to generate thumbnail")
            raise SynapseError(400, "Failed to generate thumbnail.")
@@ -424,16 +472,29 @@ class ThumbnailProvider:
        m_type: str,
        max_timeout_ms: int,
        ip_address: str,
+        use_federation: bool,
+        allow_authenticated: bool = True,
    ) -> None:
        # TODO: Don't download the whole remote file
        # We should proxy the thumbnail from the remote server instead of
        # downloading the remote file and generating our own thumbnails.
        media_info = await self.media_repo.get_remote_media_info(
-            server_name, media_id, max_timeout_ms, ip_address
+            server_name,
+            media_id,
+            max_timeout_ms,
+            ip_address,
+            use_federation,
+            allow_authenticated,
        )
        if not media_info:
            return

+        # if the media the thumbnail is generated from is authenticated, don't serve the
+        # thumbnail over an unauthenticated endpoint
+        if self.hs.config.media.enable_authenticated_media and not allow_authenticated:
+            if media_info.authenticated:
+                raise NotFoundError()
+
        thumbnail_infos = await self.store.get_remote_media_thumbnails(
            server_name, media_id
        )
@@ -448,6 +509,7 @@ class ThumbnailProvider:
            media_info.filesystem_id,
            url_cache=False,
            server_name=server_name,
+            for_federation=False,
        )

    async def _select_and_respond_with_thumbnail(
@@ -461,6 +523,8 @@ class ThumbnailProvider:
        media_id: str,
        file_id: str,
        url_cache: bool,
+        for_federation: bool,
+        media_info: Optional[LocalMedia] = None,
        server_name: Optional[str] = None,
    ) -> None:
        """
@@ -476,6 +540,8 @@ class ThumbnailProvider:
            file_id: The ID of the media that a thumbnail is being requested for.
            url_cache: True if this is from a URL cache.
            server_name: The server name, if this is a remote thumbnail.
+            for_federation: whether the request is from the federation /thumbnail request
+            media_info: metadata about the media being requested.
        """
        logger.debug(
            "_select_and_respond_with_thumbnail: media_id=%s desired=%sx%s (%s) thumbnail_infos=%s",
@@ -511,13 +577,20 @@ class ThumbnailProvider:

            responder = await self.media_storage.fetch_media(file_info)
            if responder:
-                await respond_with_responder(
-                    request,
-                    responder,
-                    file_info.thumbnail.type,
-                    file_info.thumbnail.length,
-                )
-                return
+                if for_federation:
+                    assert media_info is not None
+                    await respond_with_multipart_responder(
+                        self.hs.get_clock(), request, responder, media_info
+                    )
+                    return
+                else:
+                    await respond_with_responder(
+                        request,
+                        responder,
+                        file_info.thumbnail.type,
+                        file_info.thumbnail.length,
+                    )
+                    return

            # If we can't find the thumbnail we regenerate it. This can happen
            # if e.g. we've deleted the thumbnails but still have the original
@@ -558,12 +631,18 @@ class ThumbnailProvider:
                )

            responder = await self.media_storage.fetch_media(file_info)
-            await respond_with_responder(
-                request,
-                responder,
-                file_info.thumbnail.type,
-                file_info.thumbnail.length,
-            )
+            if for_federation:
+                assert media_info is not None
+                await respond_with_multipart_responder(
+                    self.hs.get_clock(), request, responder, media_info
+                )
+            else:
+                await respond_with_responder(
+                    request,
+                    responder,
+                    file_info.thumbnail.type,
+                    file_info.thumbnail.length,
+                )
        else:
            # This might be because:
            # 1. We can't create thumbnails for the given media (corrupted or
@@ -773,6 +773,7 @@ class Notifier:
        stream_token = await self.event_sources.bound_future_token(stream_token)

        start = self.clock.time_msec()
+        logged = False
        while True:
            current_token = self.event_sources.get_current_token()
            if stream_token.is_before_or_eq(current_token):
@@ -783,11 +784,13 @@ class Notifier:
            if now - start > 10_000:
                return False

-            logger.info(
-                "Waiting for current token to reach %s; currently at %s",
-                stream_token,
-                current_token,
-            )
+            if not logged:
+                logger.info(
+                    "Waiting for current token to reach %s; currently at %s",
+                    stream_token,
+                    current_token,
+                )
+                logged = True

            # TODO: be better
            await self.clock.sleep(0.5)
@@ -18,7 +18,8 @@
 # [This file includes modifications made by New Vector Limited]
 #
 #
-from typing import TYPE_CHECKING, Callable
+import logging
+from typing import TYPE_CHECKING, Callable, Dict, Iterable, List, Optional, Tuple

 from synapse.http.server import HttpServer, JsonResource
 from synapse.rest import admin
@@ -67,11 +68,64 @@ from synapse.rest.client import (
    voip,
 )

+logger = logging.getLogger(__name__)
+
 if TYPE_CHECKING:
    from synapse.server import HomeServer

 RegisterServletsFunc = Callable[["HomeServer", HttpServer], None]

+CLIENT_SERVLET_FUNCTIONS: Tuple[RegisterServletsFunc, ...] = (
+    versions.register_servlets,
+    initial_sync.register_servlets,
+    room.register_deprecated_servlets,
+    events.register_servlets,
+    room.register_servlets,
+    login.register_servlets,
+    profile.register_servlets,
+    presence.register_servlets,
+    directory.register_servlets,
+    voip.register_servlets,
+    pusher.register_servlets,
+    push_rule.register_servlets,
+    logout.register_servlets,
+    sync.register_servlets,
+    filter.register_servlets,
+    account.register_servlets,
+    register.register_servlets,
+    auth.register_servlets,
+    receipts.register_servlets,
+    read_marker.register_servlets,
+    room_keys.register_servlets,
+    keys.register_servlets,
+    tokenrefresh.register_servlets,
+    tags.register_servlets,
+    account_data.register_servlets,
+    reporting.register_servlets,
+    openid.register_servlets,
+    notifications.register_servlets,
+    devices.register_servlets,
+    thirdparty.register_servlets,
+    sendtodevice.register_servlets,
+    user_directory.register_servlets,
+    room_upgrade_rest_servlet.register_servlets,
+    capabilities.register_servlets,
+    account_validity.register_servlets,
+    relations.register_servlets,
+    password_policy.register_servlets,
+    knock.register_servlets,
+    appservice_ping.register_servlets,
+    admin.register_servlets_for_client_rest_resource,
+    mutual_rooms.register_servlets,
+    login_token_request.register_servlets,
+    rendezvous.register_servlets,
+    auth_issuer.register_servlets,
+)
+
+SERVLET_GROUPS: Dict[str, Iterable[RegisterServletsFunc]] = {
+    "client": CLIENT_SERVLET_FUNCTIONS,
+}
+

 class ClientRestResource(JsonResource):
    """Matrix Client API REST resource.
@@ -83,80 +137,56 @@ class ClientRestResource(JsonResource):
       * etc
    """

-    def __init__(self, hs: "HomeServer"):
+    def __init__(self, hs: "HomeServer", servlet_groups: Optional[List[str]] = None):
        JsonResource.__init__(self, hs, canonical_json=False)
-        self.register_servlets(self, hs)
+        if hs.config.media.can_load_media_repo:
+            # This import is here to prevent a circular import failure
+            from synapse.rest.client import media
+
+            SERVLET_GROUPS["media"] = (media.register_servlets,)
+        self.register_servlets(self, hs, servlet_groups)

    @staticmethod
-    def register_servlets(client_resource: HttpServer, hs: "HomeServer") -> None:
+    def register_servlets(
+        client_resource: HttpServer,
+        hs: "HomeServer",
+        servlet_groups: Optional[Iterable[str]] = None,
+    ) -> None:
        # Some servlets are only registered on the main process (and not worker
        # processes).
        is_main_process = hs.config.worker.worker_app is None

-        versions.register_servlets(hs, client_resource)
+        if not servlet_groups:
+            servlet_groups = SERVLET_GROUPS.keys()

-        # Deprecated in r0
-        initial_sync.register_servlets(hs, client_resource)
-        room.register_deprecated_servlets(hs, client_resource)
+        for servlet_group in servlet_groups:
+            # Fail on unknown servlet groups.
+            if servlet_group not in SERVLET_GROUPS:
+                if servlet_group == "media":
+                    logger.warn(
+                        "media.can_load_media_repo needs to be configured for the media servlet to be available"
+                    )
+                raise RuntimeError(
+                    f"Attempting to register unknown client servlet: '{servlet_group}'"
+                )

-        # Partially deprecated in r0
-        events.register_servlets(hs, client_resource)
+            for servletfunc in SERVLET_GROUPS[servlet_group]:
+                if not is_main_process and servletfunc in [
+                    pusher.register_servlets,
+                    logout.register_servlets,
+                    auth.register_servlets,
+                    tokenrefresh.register_servlets,
+                    reporting.register_servlets,
+                    openid.register_servlets,
+                    thirdparty.register_servlets,
+                    room_upgrade_rest_servlet.register_servlets,
+                    account_validity.register_servlets,
+                    admin.register_servlets_for_client_rest_resource,
+                    mutual_rooms.register_servlets,
+                    login_token_request.register_servlets,
+                    rendezvous.register_servlets,
+                    auth_issuer.register_servlets,
+                ]:
+                    continue

-        room.register_servlets(hs, client_resource)
-        login.register_servlets(hs, client_resource)
-        profile.register_servlets(hs, client_resource)
-        presence.register_servlets(hs, client_resource)
-        directory.register_servlets(hs, client_resource)
-        voip.register_servlets(hs, client_resource)
-        if is_main_process:
-            pusher.register_servlets(hs, client_resource)
-        push_rule.register_servlets(hs, client_resource)
-        if is_main_process:
-            logout.register_servlets(hs, client_resource)
-        sync.register_servlets(hs, client_resource)
-        filter.register_servlets(hs, client_resource)
-        account.register_servlets(hs, client_resource)
-        register.register_servlets(hs, client_resource)
-        if is_main_process:
-            auth.register_servlets(hs, client_resource)
-        receipts.register_servlets(hs, client_resource)
-        read_marker.register_servlets(hs, client_resource)
-        room_keys.register_servlets(hs, client_resource)
-        keys.register_servlets(hs, client_resource)
-        if is_main_process:
-            tokenrefresh.register_servlets(hs, client_resource)
-        tags.register_servlets(hs, client_resource)
-        account_data.register_servlets(hs, client_resource)
-        if is_main_process:
-            reporting.register_servlets(hs, client_resource)
-            openid.register_servlets(hs, client_resource)
-        notifications.register_servlets(hs, client_resource)
-        devices.register_servlets(hs, client_resource)
-        if is_main_process:
-            thirdparty.register_servlets(hs, client_resource)
-        sendtodevice.register_servlets(hs, client_resource)
-        user_directory.register_servlets(hs, client_resource)
-        if is_main_process:
-            room_upgrade_rest_servlet.register_servlets(hs, client_resource)
-        capabilities.register_servlets(hs, client_resource)
-        if is_main_process:
-            account_validity.register_servlets(hs, client_resource)
-        relations.register_servlets(hs, client_resource)
-        password_policy.register_servlets(hs, client_resource)
-        knock.register_servlets(hs, client_resource)
-        appservice_ping.register_servlets(hs, client_resource)
-        if hs.config.server.enable_media_repo:
-            from synapse.rest.client import media
-
-            media.register_servlets(hs, client_resource)
-
-        # moving to /_synapse/admin
-        if is_main_process:
-            admin.register_servlets_for_client_rest_resource(hs, client_resource)
-
-        # unstable
-        if is_main_process:
-            mutual_rooms.register_servlets(hs, client_resource)
-            login_token_request.register_servlets(hs, client_resource)
-            rendezvous.register_servlets(hs, client_resource)
-            auth_issuer.register_servlets(hs, client_resource)
+                servletfunc(hs, client_resource)
@@ -31,7 +31,9 @@ from synapse.rest.admin import admin_patterns, assert_requester_is_admin
 from synapse.types import JsonDict, UserID

 if TYPE_CHECKING:
-    from synapse.server import HomeServer
+    from typing_extensions import assert_never
+
+    from synapse.server import HomeServer, HomeServerConfig


 class ExperimentalFeature(str, Enum):
@@ -39,8 +41,16 @@ class ExperimentalFeature(str, Enum):
    Currently supported per-user features
    """

-    MSC3026 = "msc3026"
    MSC3881 = "msc3881"
+    MSC3575 = "msc3575"
+
+    def is_globally_enabled(self, config: "HomeServerConfig") -> bool:
+        if self is ExperimentalFeature.MSC3881:
+            return config.experimental.msc3881_enabled
+        if self is ExperimentalFeature.MSC3575:
+            return config.experimental.msc3575_enabled
+
+        assert_never(self)


 class ExperimentalFeaturesRestServlet(RestServlet):
@@ -256,9 +256,15 @@ class KeyChangesServlet(RestServlet):

        user_id = requester.user.to_string()

-        results = await self.device_handler.get_user_ids_changed(user_id, from_token)
+        device_list_updates = await self.device_handler.get_user_ids_changed(
+            user_id, from_token
+        )

-        return 200, results
+        response: JsonDict = {}
+        response["changed"] = list(device_list_updates.changed)
+        response["left"] = list(device_list_updates.left)
+
+        return 200, response


 class OneTimeKeyServlet(RestServlet):
@@ -47,7 +47,7 @@ from synapse.util.stringutils import parse_and_validate_server_name
 logger = logging.getLogger(__name__)


-class UnstablePreviewURLServlet(RestServlet):
+class PreviewURLServlet(RestServlet):
    """
    Same as `GET /_matrix/media/r0/preview_url`, this endpoint provides a generic preview API
    for URLs which outputs Open Graph (https://ogp.me/) responses (with some Matrix
@@ -65,9 +65,7 @@ class UnstablePreviewURLServlet(RestServlet):
      * Matrix cannot be used to distribute the metadata between homeservers.
    """

-    PATTERNS = [
-        re.compile(r"^/_matrix/client/unstable/org.matrix.msc3916/media/preview_url$")
-    ]
+    PATTERNS = [re.compile(r"^/_matrix/client/v1/media/preview_url$")]

    def __init__(
        self,
@@ -95,10 +93,8 @@ class UnstablePreviewURLServlet(RestServlet):
        respond_with_json_bytes(request, 200, og, send_cors=True)


-class UnstableMediaConfigResource(RestServlet):
-    PATTERNS = [
-        re.compile(r"^/_matrix/client/unstable/org.matrix.msc3916/media/config$")
-    ]
+class MediaConfigResource(RestServlet):
+    PATTERNS = [re.compile(r"^/_matrix/client/v1/media/config$")]

    def __init__(self, hs: "HomeServer"):
        super().__init__()
@@ -112,10 +108,10 @@ class UnstableMediaConfigResource(RestServlet):
        respond_with_json(request, 200, self.limits_dict, send_cors=True)


-class UnstableThumbnailResource(RestServlet):
+class ThumbnailResource(RestServlet):
    PATTERNS = [
        re.compile(
-            "/_matrix/client/unstable/org.matrix.msc3916/media/thumbnail/(?P<server_name>[^/]*)/(?P<media_id>[^/]*)$"
+            "/_matrix/client/v1/media/thumbnail/(?P<server_name>[^/]*)/(?P<media_id>[^/]*)$"
        )
    ]

@@ -159,11 +155,25 @@ class UnstableThumbnailResource(RestServlet):
        if self._is_mine_server_name(server_name):
            if self.dynamic_thumbnails:
                await self.thumbnailer.select_or_generate_local_thumbnail(
-                    request, media_id, width, height, method, m_type, max_timeout_ms
+                    request,
+                    media_id,
+                    width,
+                    height,
+                    method,
+                    m_type,
+                    max_timeout_ms,
+                    False,
                )
            else:
                await self.thumbnailer.respond_local_thumbnail(
-                    request, media_id, width, height, method, m_type, max_timeout_ms
+                    request,
+                    media_id,
+                    width,
+                    height,
+                    method,
+                    m_type,
+                    max_timeout_ms,
+                    False,
                )
            self.media_repo.mark_recently_accessed(None, media_id)
        else:
@@ -191,6 +201,7 @@ class UnstableThumbnailResource(RestServlet):
                m_type,
                max_timeout_ms,
                ip_address,
+                True,
            )
            self.media_repo.mark_recently_accessed(server_name, media_id)

@@ -260,11 +271,9 @@ class DownloadResource(RestServlet):
 def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
    media_repo = hs.get_media_repository()
    if hs.config.media.url_preview_enabled:
-        UnstablePreviewURLServlet(hs, media_repo, media_repo.media_storage).register(
+        PreviewURLServlet(hs, media_repo, media_repo.media_storage).register(
            http_server
        )
-    UnstableMediaConfigResource(hs).register(http_server)
-    UnstableThumbnailResource(hs, media_repo, media_repo.media_storage).register(
-        http_server
-    )
+    MediaConfigResource(hs).register(http_server)
+    ThumbnailResource(hs, media_repo, media_repo.media_storage).register(http_server)
    DownloadResource(hs, media_repo).register(http_server)
@@ -32,6 +32,7 @@ from synapse.http.servlet import (
 )
 from synapse.http.site import SynapseRequest
 from synapse.push import PusherConfigException
+from synapse.rest.admin.experimental_features import ExperimentalFeature
 from synapse.rest.client._base import client_patterns
 from synapse.rest.synapse.client.unsubscribe import UnsubscribeResource
 from synapse.types import JsonDict
@@ -49,20 +50,22 @@ class PushersRestServlet(RestServlet):
        super().__init__()
        self.hs = hs
        self.auth = hs.get_auth()
-        self._msc3881_enabled = self.hs.config.experimental.msc3881_enabled
+        self._store = hs.get_datastores().main

    async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
        requester = await self.auth.get_user_by_req(request)
-        user = requester.user
+        user_id = requester.user.to_string()

-        pushers = await self.hs.get_datastores().main.get_pushers_by_user_id(
-            user.to_string()
+        msc3881_enabled = await self._store.is_feature_enabled(
+            user_id, ExperimentalFeature.MSC3881
        )

+        pushers = await self.hs.get_datastores().main.get_pushers_by_user_id(user_id)
+
        pusher_dicts = [p.as_dict() for p in pushers]

        for pusher in pusher_dicts:
-            if self._msc3881_enabled:
+            if msc3881_enabled:
                pusher["org.matrix.msc3881.enabled"] = pusher["enabled"]
                pusher["org.matrix.msc3881.device_id"] = pusher["device_id"]
            del pusher["enabled"]
@@ -80,11 +83,15 @@ class PushersSetRestServlet(RestServlet):
        self.auth = hs.get_auth()
        self.notifier = hs.get_notifier()
        self.pusher_pool = self.hs.get_pusherpool()
-        self._msc3881_enabled = self.hs.config.experimental.msc3881_enabled
+        self._store = hs.get_datastores().main

    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
        requester = await self.auth.get_user_by_req(request)
-        user = requester.user
+        user_id = requester.user.to_string()
+
+        msc3881_enabled = await self._store.is_feature_enabled(
+            user_id, ExperimentalFeature.MSC3881
+        )

        content = parse_json_object_from_request(request)

@@ -95,7 +102,7 @@ class PushersSetRestServlet(RestServlet):
            and content["kind"] is None
        ):
            await self.pusher_pool.remove_pusher(
-                content["app_id"], content["pushkey"], user_id=user.to_string()
+                content["app_id"], content["pushkey"], user_id=user_id
            )
            return 200, {}

@@ -120,19 +127,19 @@ class PushersSetRestServlet(RestServlet):
            append = content["append"]

        enabled = True
-        if self._msc3881_enabled and "org.matrix.msc3881.enabled" in content:
+        if msc3881_enabled and "org.matrix.msc3881.enabled" in content:
            enabled = content["org.matrix.msc3881.enabled"]

        if not append:
            await self.pusher_pool.remove_pushers_by_app_id_and_pushkey_not_user(
                app_id=content["app_id"],
                pushkey=content["pushkey"],
-                not_user_id=user.to_string(),
+                not_user_id=user_id,
            )

        try:
            await self.pusher_pool.add_or_update_pusher(
-                user_id=user.to_string(),
+                user_id=user_id,
                kind=content["kind"],
                app_id=content["app_id"],
                app_display_name=content["app_display_name"],
@@ -67,7 +67,8 @@ from synapse.streams.config import PaginationConfig
 from synapse.types import JsonDict, Requester, StreamToken, ThirdPartyInstanceID, UserID
 from synapse.types.state import StateFilter
 from synapse.util.cancellation import cancellable
-from synapse.util.stringutils import parse_and_validate_server_name, random_string
+from synapse.util.events import generate_fake_event_id
+from synapse.util.stringutils import parse_and_validate_server_name

 if TYPE_CHECKING:
    from synapse.server import HomeServer
@@ -325,7 +326,7 @@ class RoomStateEventRestServlet(RestServlet):
                )
                event_id = event.event_id
        except ShadowBanError:
-            event_id = "$" + random_string(43)
+            event_id = generate_fake_event_id()

        set_tag("event_id", event_id)
        ret = {"event_id": event_id}
@@ -377,7 +378,7 @@ class RoomSendEventRestServlet(TransactionRestServlet):
            )
            event_id = event.event_id
        except ShadowBanError:
-            event_id = "$" + random_string(43)
+            event_id = generate_fake_event_id()

        set_tag("event_id", event_id)
        return 200, {"event_id": event_id}
@@ -1193,7 +1194,7 @@ class RoomRedactEventRestServlet(TransactionRestServlet):

            event_id = event.event_id
        except ShadowBanError:
-            event_id = "$" + random_string(43)
+            event_id = generate_fake_event_id()

        set_tag("event_id", event_id)
        return 200, {"event_id": event_id}
@@ -52,8 +52,9 @@ from synapse.http.servlet import (
    parse_string,
 )
 from synapse.http.site import SynapseRequest
-from synapse.logging.opentracing import trace_with_opname
-from synapse.types import JsonDict, Requester, StreamToken
+from synapse.logging.opentracing import log_kv, set_tag, trace_with_opname
+from synapse.rest.admin.experimental_features import ExperimentalFeature
+from synapse.types import JsonDict, Requester, SlidingSyncStreamToken, StreamToken
 from synapse.types.rest.client import SlidingSyncBody
 from synapse.util import json_decoder
 from synapse.util.caches.lrucache import LruCache
@@ -673,7 +674,9 @@ class SlidingSyncE2eeRestServlet(RestServlet):
        )

    async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
-        requester = await self.auth.get_user_by_req(request, allow_guest=True)
+        requester = await self.auth.get_user_by_req_experimental_feature(
+            request, allow_guest=True, feature=ExperimentalFeature.MSC3575
+        )
        user = requester.user
        device_id = requester.device_id

@@ -873,9 +876,11 @@ class SlidingSyncRestServlet(RestServlet):
        self.event_serializer = hs.get_event_client_serializer()

    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
-        requester = await self.auth.get_user_by_req(request, allow_guest=True)
+        requester = await self.auth.get_user_by_req_experimental_feature(
+            request, allow_guest=True, feature=ExperimentalFeature.MSC3575
+        )
+
        user = requester.user
-        device_id = requester.device_id

        timeout = parse_integer(request, "timeout", default=0)
        # Position in the stream
@@ -883,22 +888,50 @@ class SlidingSyncRestServlet(RestServlet):

        from_token = None
        if from_token_string is not None:
-            from_token = await StreamToken.from_string(self.store, from_token_string)
+            from_token = await SlidingSyncStreamToken.from_string(
+                self.store, from_token_string
+            )

        # TODO: We currently don't know whether we're going to use sticky params or
        # maybe some filters like sync v2  where they are built up once and referenced
        # by filter ID. For now, we will just prototype with always passing everything
        # in.
        body = parse_and_validate_json_object_from_request(request, SlidingSyncBody)
-        logger.info("Sliding sync request: %r", body)
+
+        # Tag and log useful data to differentiate requests.
+        set_tag(
+            "sliding_sync.sync_type", "initial" if from_token is None else "incremental"
+        )
+        set_tag("sliding_sync.conn_id", body.conn_id or "")
+        log_kv(
+            {
+                "sliding_sync.lists": {
+                    list_name: {
+                        "ranges": list_config.ranges,
+                        "timeline_limit": list_config.timeline_limit,
+                    }
+                    for list_name, list_config in (body.lists or {}).items()
+                },
+                "sliding_sync.room_subscriptions": list(
+                    (body.room_subscriptions or {}).keys()
+                ),
+                # We also include the number of room subscriptions because logs are
+                # limited to 1024 characters and the large room ID list above can be cut
+                # off.
+                "sliding_sync.num_room_subscriptions": len(
+                    (body.room_subscriptions or {}).keys()
+                ),
+            }
+        )

        sync_config = SlidingSyncConfig(
            user=user,
-            device_id=device_id,
+            requester=requester,
            # FIXME: Currently, we're just manually copying the fields from the
-            # `SlidingSyncBody` into the config. How can we gurantee into the future
+            # `SlidingSyncBody` into the config. How can we guarantee into the future
            # that we don't forget any? I would like something more structured like
            # `copy_attributes(from=body, to=config)`
+            conn_id=body.conn_id,
            lists=body.lists,
            room_subscriptions=body.room_subscriptions,
            extensions=body.extensions,
@@ -921,7 +954,6 @@ class SlidingSyncRestServlet(RestServlet):

        return 200, response_content

-    # TODO: Is there a better way to encode things?
    async def encode_response(
        self,
        requester: Requester,
@@ -936,7 +968,9 @@ class SlidingSyncRestServlet(RestServlet):
        response["rooms"] = await self.encode_rooms(
            requester, sliding_sync_result.rooms
        )
-        response["extensions"] = {}  # TODO: sliding_sync_result.extensions
+        response["extensions"] = await self.encode_extensions(
+            requester, sliding_sync_result.extensions
+        )

        return response

@@ -976,6 +1010,7 @@ class SlidingSyncRestServlet(RestServlet):
        serialized_rooms: Dict[str, JsonDict] = {}
        for room_id, room_result in rooms.items():
            serialized_rooms[room_id] = {
+                "bump_stamp": room_result.bump_stamp,
                "joined_count": room_result.joined_count,
                "invited_count": room_result.invited_count,
                "notification_count": room_result.notification_count,
@@ -988,16 +1023,37 @@ class SlidingSyncRestServlet(RestServlet):
            if room_result.avatar:
                serialized_rooms[room_id]["avatar"] = room_result.avatar

-            if room_result.heroes:
-                serialized_rooms[room_id]["heroes"] = room_result.heroes
+            if room_result.heroes is not None and len(room_result.heroes) > 0:
+                serialized_heroes = []
+                for hero in room_result.heroes:
+                    serialized_hero = {
+                        "user_id": hero.user_id,
+                    }
+                    if hero.display_name is not None:
+                        # Not a typo, just how "displayname" is spelled in the spec
+                        serialized_hero["displayname"] = hero.display_name
+
+                    if hero.avatar_url is not None:
+                        serialized_hero["avatar_url"] = hero.avatar_url
+
+                    serialized_heroes.append(serialized_hero)
+                serialized_rooms[room_id]["heroes"] = serialized_heroes

            # We should only include the `initial` key if it's `True` to save bandwidth.
            # The absense of this flag means `False`.
            if room_result.initial:
                serialized_rooms[room_id]["initial"] = room_result.initial

-            # This will omitted for invite/knock rooms with `stripped_state`
-            if room_result.required_state is not None:
+            if room_result.unstable_expanded_timeline:
+                serialized_rooms[room_id][
+                    "unstable_expanded_timeline"
+                ] = room_result.unstable_expanded_timeline
+
+            # This will be omitted for invite/knock rooms with `stripped_state`
+            if (
+                room_result.required_state is not None
+                and len(room_result.required_state) > 0
+            ):
                serialized_required_state = (
                    await self.event_serializer.serialize_events(
                        room_result.required_state,
@@ -1007,8 +1063,11 @@ class SlidingSyncRestServlet(RestServlet):
                )
                serialized_rooms[room_id]["required_state"] = serialized_required_state

-            # This will omitted for invite/knock rooms with `stripped_state`
-            if room_result.timeline_events is not None:
+            # This will be omitted for invite/knock rooms with `stripped_state`
+            if (
+                room_result.timeline_events is not None
+                and len(room_result.timeline_events) > 0
+            ):
                serialized_timeline = await self.event_serializer.serialize_events(
                    room_result.timeline_events,
                    time_now,
@@ -1017,17 +1076,17 @@ class SlidingSyncRestServlet(RestServlet):
                )
                serialized_rooms[room_id]["timeline"] = serialized_timeline

-            # This will omitted for invite/knock rooms with `stripped_state`
+            # This will be omitted for invite/knock rooms with `stripped_state`
            if room_result.limited is not None:
                serialized_rooms[room_id]["limited"] = room_result.limited

-            # This will omitted for invite/knock rooms with `stripped_state`
+            # This will be omitted for invite/knock rooms with `stripped_state`
            if room_result.prev_batch is not None:
                serialized_rooms[room_id]["prev_batch"] = (
                    await room_result.prev_batch.to_string(self.store)
                )

-            # This will omitted for invite/knock rooms with `stripped_state`
+            # This will be omitted for invite/knock rooms with `stripped_state`
            if room_result.num_live is not None:
                serialized_rooms[room_id]["num_live"] = room_result.num_live

@@ -1036,7 +1095,10 @@ class SlidingSyncRestServlet(RestServlet):
                serialized_rooms[room_id]["is_dm"] = room_result.is_dm

            # Stripped state only applies to invite/knock rooms
-            if room_result.stripped_state is not None:
+            if (
+                room_result.stripped_state is not None
+                and len(room_result.stripped_state) > 0
+            ):
                # TODO: `knocked_state` but that isn't specced yet.
                #
                # TODO: Instead of adding `knocked_state`, it would be good to rename
@@ -1047,10 +1109,76 @@ class SlidingSyncRestServlet(RestServlet):

        return serialized_rooms

+    async def encode_extensions(
+        self, requester: Requester, extensions: SlidingSyncResult.Extensions
+    ) -> JsonDict:
+        serialized_extensions: JsonDict = {}
+
+        if extensions.to_device is not None:
+            serialized_extensions["to_device"] = {
+                "next_batch": extensions.to_device.next_batch,
+                "events": extensions.to_device.events,
+            }
+
+        if extensions.e2ee is not None:
+            serialized_extensions["e2ee"] = {
+                # We always include this because
+                # https://github.com/vector-im/element-android/issues/3725. The spec
+                # isn't terribly clear on when this can be omitted and how a client
+                # would tell the difference between "no keys present" and "nothing
+                # changed" in terms of whole field absent / individual key type entry
+                # absent Corresponding synapse issue:
+                # https://github.com/matrix-org/synapse/issues/10456
+                "device_one_time_keys_count": extensions.e2ee.device_one_time_keys_count,
+                # https://github.com/matrix-org/matrix-doc/blob/54255851f642f84a4f1aaf7bc063eebe3d76752b/proposals/2732-olm-fallback-keys.md
+                # states that this field should always be included, as long as the
+                # server supports the feature.
+                "device_unused_fallback_key_types": extensions.e2ee.device_unused_fallback_key_types,
+            }
+
+            if extensions.e2ee.device_list_updates is not None:
+                serialized_extensions["e2ee"]["device_lists"] = {}
+
+                serialized_extensions["e2ee"]["device_lists"]["changed"] = list(
+                    extensions.e2ee.device_list_updates.changed
+                )
+                serialized_extensions["e2ee"]["device_lists"]["left"] = list(
+                    extensions.e2ee.device_list_updates.left
+                )
+
+        if extensions.account_data is not None:
+            serialized_extensions["account_data"] = {
+                # Same as the the top-level `account_data.events` field in Sync v2.
+                "global": [
+                    {"type": account_data_type, "content": content}
+                    for account_data_type, content in extensions.account_data.global_account_data_map.items()
+                ],
+                # Same as the joined room's account_data field in Sync v2, e.g the path
+                # `rooms.join["!foo:bar"].account_data.events`.
+                "rooms": {
+                    room_id: [
+                        {"type": account_data_type, "content": content}
+                        for account_data_type, content in event_map.items()
+                    ]
+                    for room_id, event_map in extensions.account_data.account_data_by_room_map.items()
+                },
+            }
+
+        if extensions.receipts is not None:
+            serialized_extensions["receipts"] = {
+                "rooms": extensions.receipts.room_id_to_receipt_map,
+            }
+
+        if extensions.typing is not None:
+            serialized_extensions["typing"] = {
+                "rooms": extensions.typing.room_id_to_typing_map,
+            }
+
+        return serialized_extensions
+

 def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
    SyncRestServlet(hs).register(http_server)

-    if hs.config.experimental.msc3575_enabled:
-        SlidingSyncRestServlet(hs).register(http_server)
-        SlidingSyncE2eeRestServlet(hs).register(http_server)
+    SlidingSyncRestServlet(hs).register(http_server)
+    SlidingSyncE2eeRestServlet(hs).register(http_server)
@@ -25,11 +25,11 @@ import logging
 import re
 from typing import TYPE_CHECKING, Tuple

-from twisted.web.server import Request
-
 from synapse.api.constants import RoomCreationPreset
 from synapse.http.server import HttpServer
 from synapse.http.servlet import RestServlet
+from synapse.http.site import SynapseRequest
+from synapse.rest.admin.experimental_features import ExperimentalFeature
 from synapse.types import JsonDict

 if TYPE_CHECKING:
@@ -45,6 +45,8 @@ class VersionsRestServlet(RestServlet):
    def __init__(self, hs: "HomeServer"):
        super().__init__()
        self.config = hs.config
+        self.auth = hs.get_auth()
+        self.store = hs.get_datastores().main

        # Calculate these once since they shouldn't change after start-up.
        self.e2ee_forced_public = (
@@ -60,7 +62,26 @@ class VersionsRestServlet(RestServlet):
            in self.config.room.encryption_enabled_by_default_for_room_presets
        )

-    def on_GET(self, request: Request) -> Tuple[int, JsonDict]:
+    async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
+        msc3881_enabled = self.config.experimental.msc3881_enabled
+        msc3575_enabled = self.config.experimental.msc3575_enabled
+
+        if self.auth.has_access_token(request):
+            requester = await self.auth.get_user_by_req(
+                request,
+                allow_guest=True,
+                allow_locked=True,
+                allow_expired=True,
+            )
+            user_id = requester.user.to_string()
+
+            msc3881_enabled = await self.store.is_feature_enabled(
+                user_id, ExperimentalFeature.MSC3881
+            )
+            msc3575_enabled = await self.store.is_feature_enabled(
+                user_id, ExperimentalFeature.MSC3575
+            )
+
        return (
            200,
            {
@@ -90,6 +111,7 @@ class VersionsRestServlet(RestServlet):
                    "v1.8",
                    "v1.9",
                    "v1.10",
+                    "v1.11",
                ],
                # as per MSC1497:
                "unstable_features": {
@@ -124,7 +146,7 @@ class VersionsRestServlet(RestServlet):
                    # TODO: this is no longer needed once unstable MSC3882 does not need to be supported:
                    "org.matrix.msc3882": self.config.auth.login_via_existing_enabled,
                    # Adds support for remotely enabling/disabling pushers, as per MSC3881
-                    "org.matrix.msc3881": self.config.experimental.msc3881_enabled,
+                    "org.matrix.msc3881": 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
@@ -151,6 +173,8 @@ class VersionsRestServlet(RestServlet):
                    ),
                    # MSC4151: Report room API (Client-Server API)
                    "org.matrix.msc4151": self.config.experimental.msc4151_enabled,
+                    # Simplified sliding sync
+                    "org.matrix.simplified_msc3575": msc3575_enabled,
                },
            },
        )
@@ -84,7 +84,7 @@ class DownloadResource(RestServlet):

        if self._is_mine_server_name(server_name):
            await self.media_repo.get_local_media(
-                request, media_id, file_name, max_timeout_ms
+                request, media_id, file_name, max_timeout_ms, allow_authenticated=False
            )
        else:
            allow_remote = parse_boolean(request, "allow_remote", default=True)
@@ -106,4 +106,5 @@ class DownloadResource(RestServlet):
                max_timeout_ms,
                ip_address,
                False,
+                allow_authenticated=False,
            )
@@ -88,11 +88,27 @@ class ThumbnailResource(RestServlet):
        if self._is_mine_server_name(server_name):
            if self.dynamic_thumbnails:
                await self.thumbnail_provider.select_or_generate_local_thumbnail(
-                    request, media_id, width, height, method, m_type, max_timeout_ms
+                    request,
+                    media_id,
+                    width,
+                    height,
+                    method,
+                    m_type,
+                    max_timeout_ms,
+                    False,
+                    allow_authenticated=False,
                )
            else:
                await self.thumbnail_provider.respond_local_thumbnail(
-                    request, media_id, width, height, method, m_type, max_timeout_ms
+                    request,
+                    media_id,
+                    width,
+                    height,
+                    method,
+                    m_type,
+                    max_timeout_ms,
+                    False,
+                    allow_authenticated=False,
                )
            self.media_repo.mark_recently_accessed(None, media_id)
        else:
@@ -120,5 +136,7 @@ class ThumbnailResource(RestServlet):
                m_type,
                max_timeout_ms,
                ip_address,
+                use_federation=False,
+                allow_authenticated=False,
            )
            self.media_repo.mark_recently_accessed(server_name, media_id)
@@ -28,12 +28,13 @@
 import abc
 import functools
 import logging
-from typing import TYPE_CHECKING, Callable, Dict, List, Optional, TypeVar, cast
+from typing import TYPE_CHECKING, Callable, Dict, List, Optional, Type, TypeVar, cast

 from typing_extensions import TypeAlias

 from twisted.internet.interfaces import IOpenSSLContextFactory
 from twisted.internet.tcp import Port
+from twisted.python.threadpool import ThreadPool
 from twisted.web.iweb import IPolicyForHTTPS
 from twisted.web.resource import Resource

@@ -123,6 +124,7 @@ from synapse.http.client import (
 )
 from synapse.http.matrixfederationclient import MatrixFederationHttpClient
 from synapse.media.media_repository import MediaRepository
+from synapse.metrics import register_threadpool
 from synapse.metrics.common_usage_metrics import CommonUsageMetricsManager
 from synapse.module_api import ModuleApi
 from synapse.module_api.callbacks import ModuleApiCallbacks
@@ -161,6 +163,7 @@ if TYPE_CHECKING:
    from synapse.handlers.jwt import JwtHandler
    from synapse.handlers.oidc import OidcHandler
    from synapse.handlers.saml import SamlHandler
+    from synapse.storage._base import SQLBaseStore


 # The annotation for `cache_in_self` used to be
@@ -255,10 +258,13 @@ class HomeServer(metaclass=abc.ABCMeta):
        "stats",
    ]

-    # This is overridden in derived application classes
-    # (such as synapse.app.homeserver.SynapseHomeServer) and gives the class to be
-    # instantiated during setup() for future return by get_datastores()
-    DATASTORE_CLASS = abc.abstractproperty()
+    @property
+    @abc.abstractmethod
+    def DATASTORE_CLASS(self) -> Type["SQLBaseStore"]:
+        # This is overridden in derived application classes
+        # (such as synapse.app.homeserver.SynapseHomeServer) and gives the class to be
+        # instantiated during setup() for future return by get_datastores()
+        pass

    def __init__(
        self,
@@ -555,6 +561,7 @@ class HomeServer(metaclass=abc.ABCMeta):
    def get_sync_handler(self) -> SyncHandler:
        return SyncHandler(self)

+    @cache_in_self
    def get_sliding_sync_handler(self) -> SlidingSyncHandler:
        return SlidingSyncHandler(self)

@@ -936,3 +943,24 @@ class HomeServer(metaclass=abc.ABCMeta):
    @cache_in_self
    def get_task_scheduler(self) -> TaskScheduler:
        return TaskScheduler(self)
+
+    @cache_in_self
+    def get_media_sender_thread_pool(self) -> ThreadPool:
+        """Fetch the threadpool used to read files when responding to media
+        download requests."""
+
+        # We can choose a large threadpool size as these threads predominately
+        # do IO rather than CPU work.
+        media_threadpool = ThreadPool(
+            name="media_threadpool", minthreads=1, maxthreads=50
+        )
+
+        media_threadpool.start()
+        self.get_reactor().addSystemEventTrigger(
+            "during", "shutdown", media_threadpool.stop
+        )
+
+        # Register the threadpool with our metrics.
+        register_threadpool("media", media_threadpool)
+
+        return media_threadpool
@@ -119,14 +119,16 @@ class SQLBaseStore(metaclass=ABCMeta):
            self._attempt_to_invalidate_cache(
                "get_user_in_room_with_profile", (room_id, user_id)
            )
-            self._attempt_to_invalidate_cache(
-                "get_rooms_for_user_with_stream_ordering", (user_id,)
-            )
            self._attempt_to_invalidate_cache("get_rooms_for_user", (user_id,))
+            self._attempt_to_invalidate_cache(
+                "_get_rooms_for_local_user_where_membership_is_inner", (user_id,)
+            )

        # Purge other caches based on room state.
        self._attempt_to_invalidate_cache("get_room_summary", (room_id,))
        self._attempt_to_invalidate_cache("get_partial_current_state_ids", (room_id,))
+        self._attempt_to_invalidate_cache("get_room_type", (room_id,))
+        self._attempt_to_invalidate_cache("get_room_encryption", (room_id,))

    def _invalidate_state_caches_all(self, room_id: str) -> None:
        """Invalidates caches that are based on the current state, but does
@@ -148,11 +150,13 @@ class SQLBaseStore(metaclass=ABCMeta):
        self._attempt_to_invalidate_cache("get_local_users_in_room", (room_id,))
        self._attempt_to_invalidate_cache("does_pair_of_users_share_a_room", None)
        self._attempt_to_invalidate_cache("get_user_in_room_with_profile", None)
-        self._attempt_to_invalidate_cache(
-            "get_rooms_for_user_with_stream_ordering", None
-        )
        self._attempt_to_invalidate_cache("get_rooms_for_user", None)
+        self._attempt_to_invalidate_cache(
+            "_get_rooms_for_local_user_where_membership_is_inner", None
+        )
        self._attempt_to_invalidate_cache("get_room_summary", (room_id,))
+        self._attempt_to_invalidate_cache("get_room_type", (room_id,))
+        self._attempt_to_invalidate_cache("get_room_encryption", (room_id,))

    def _attempt_to_invalidate_cache(
        self, cache_name: str, key: Optional[Collection[Any]]
@@ -502,8 +502,15 @@ class EventsPersistenceStorageController:
        """
        state = await self._calculate_current_state(room_id)
        delta = await self._calculate_state_delta(room_id, state)
+        sliding_sync_table_changes = (
+            await self.persist_events_store._calculate_sliding_sync_table_changes(
+                room_id, [], delta
+            )
+        )

-        await self.persist_events_store.update_current_state(room_id, delta)
+        await self.persist_events_store.update_current_state(
+            room_id, delta, sliding_sync_table_changes
+        )

    async def _calculate_current_state(self, room_id: str) -> StateMap[str]:
        """Calculate the current state of a room, based on the forward extremities
@@ -409,7 +409,7 @@ class StateStorageController:

        return state_ids

-    async def get_state_at(
+    async def get_state_ids_at(
        self,
        room_id: str,
        stream_position: StreamToken,
@@ -460,6 +460,30 @@ class StateStorageController:
            )
        return state

+    @trace
+    @tag_args
+    async def get_state_at(
+        self,
+        room_id: str,
+        stream_position: StreamToken,
+        state_filter: Optional[StateFilter] = None,
+        await_full_state: bool = True,
+    ) -> StateMap[EventBase]:
+        """Same as `get_state_ids_at` but also fetches the events"""
+        state_map_ids = await self.get_state_ids_at(
+            room_id, stream_position, state_filter, await_full_state
+        )
+
+        event_map = await self.stores.main.get_events(list(state_map_ids.values()))
+
+        state_map = {}
+        for key, event_id in state_map_ids.items():
+            event = event_map.get(event_id)
+            if event:
+                state_map[key] = event
+
+        return state_map
+
    @trace
    @tag_args
    async def get_state_for_groups(
--- a/Show More
+++ b/Show More
				`@@ -1 +0,0 @@`
				Add `rooms` data to experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint.
				`@@ -1 +0,0 @@`
				Add `room_types`/`not_room_types` filtering to experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint.
				`@@ -1 +0,0 @@`
				Clarify `url_preview_url_blacklist` is a usability feature.
				`@@ -1 +0,0 @@`
				`Fix rare race which causes no new to-device messages to be received from remote server.`
				`@@ -1 +0,0 @@`
				`Support [MSC3916](https://github.com/matrix-org/matrix-spec-proposals/blob/rav/authentication-for-media/proposals/3916-authentication-for-media.md) by adding _matrix/client/v1/media/download endpoint.`
				`@@ -1 +0,0 @@`
				`Fix building debian packages on non-clean checkouts.`
				`@@ -1 +0,0 @@`
				`Pin CI to complement release branch for releases.`
				`@@ -0,0 +1 @@`
				Pre-populate room data used in experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint for quick filtering/sorting.
				`@@ -0,0 +1 @@`
				`Refactor sliding sync class into multiple files.`
				`@@ -0,0 +1 @@`
				`Store sliding sync per-connection state in the database.`