Add tests for notification counts

Newsfile
SS: Hook up notification counts
2024-08-16 10:45:15 +01:00 · 2024-08-09 10:32:58 +01:00 · 2024-08-09 10:31:56 +01:00 · 2024-08-08 10:44:17 +01:00 · 2024-08-07 11:27:50 -05:00 · 2024-08-07 10:37:54 +01:00
137 changed files with 16480 additions and 3390 deletions
@@ -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 +1,228 @@
+# 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 +273,7 @@ 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 = "1.0.204"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7253ab4de971e72fb7be983802300c30b5a7f0c2e56fab8abfc6a214307c0094"
+checksum = "bc76f558e0cbb2a839d37354c575f1dc3fdc6546b5be373ba43d95f231bf7c12"
 dependencies = [
 "serde_derive",
 ]

 [[package]]
 name = "serde_derive"
-version = "1.0.203"
+version = "1.0.204"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "500cbc0ebeb6f46627f50f3f5811ccf6bf00643be300b4c3eabc0ef55dc5b5ba"
+checksum = "e0cd7e117be63d3c3678776753929474f3b04a43a080c744d6b0ae2a8c28e222"
 dependencies = [
 "proc-macro2",
 "quote",
@@ -505,11 +505,12 @@ dependencies = [

 [[package]]
 name = "serde_json"
-version = "1.0.119"
+version = "1.0.122"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e8eddb61f0697cc3989c5d64b452f5488e2b8a60fd7d5076a3045076ffef8cb0"
+checksum = "784b6203951c57ff748476b126ccb5e8e2959a5c19e5c617ab1956be3dbc68da"
 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 `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.
@@ -0,0 +1 @@
+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.
@@ -1 +1 @@
-Add `rooms` data to experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint.
+Add more tracing to experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint.
@@ -0,0 +1,3 @@
+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.
@@ -0,0 +1 @@
+Fixup comment in sliding sync implementation.
@@ -0,0 +1 @@
+Fix experimental sliding sync implementation to remember any updates in rooms that were not sent down immediately.
@@ -0,0 +1 @@
+Return correct per-room notification and highlight counts in experimental sliding sync implementation.
@@ -1,3 +1,45 @@
+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,
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+         d="m 127.105,9.74282 v 1.97148 c 0.343,-0.6477 0.905,-1.1905 1.686,-1.6286 0.8,-0.45716 1.762,-0.68573 2.885,-0.68573 1.753,0 3.105,0.53333 4.058,1.60003 0.971,1.0666 1.457,2.4857 1.457,4.2571 v 9.3143 h -3.4 v -8.8857 c 0,-1.0476 -0.248,-1.8667 -0.743,-2.4572 -0.476,-0.6095 -1.21,-0.9142 -2.2,-0.9142 -1.086,0 -1.943,0.3238 -2.572,0.9714 -0.609,0.6476 -0.914,1.5428 -0.914,2.6857 v 8.6 h -3.4 V 9.74282 Z"
+         fill="#000000"
+         id="path11" /><path
+         d="m 147.12,21.5428 v 2.9429 c -0.419,0.1143 -1.009,0.1714 -1.771,0.1714 -2.895,0 -4.343,-1.4571 -4.343,-4.3714 v -7.8286 h -2.257 V 9.74282 h 2.257 V 5.88568 h 3.4 v 3.85714 h 2.772 v 2.71428 h -2.772 v 7.4857 c 0,1.1619 0.552,1.7429 1.657,1.7429 z"
+         fill="#000000"
+         id="path12" /></g></g></svg>
@@ -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 = "1.113.0rc1"
 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"

@@ -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.
 #
@@ -70,6 +70,7 @@ 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:

@@ -112,10 +113,12 @@ def _prepare() -> None:
    # Make sure we're in a git repo.
    synapse_repo = get_repo_and_check_clean_checkout()
    sytest_repo = get_repo_and_check_clean_checkout("../sytest", "sytest")
+    complement_repo = get_repo_and_check_clean_checkout("../complement", "complement")

    click.secho("Updating Synapse and Sytest git repos...")
    synapse_repo.remote().fetch()
    sytest_repo.remote().fetch()
+    complement_repo.remote().fetch()

    # Get the current version and AST from root Synapse module.
    current_version = get_package_version()
@@ -208,7 +211,15 @@ def _prepare() -> None:
            "Which branch should the release be based on?", default=default
        )

-        for repo_name, repo in {"synapse": synapse_repo, "sytest": sytest_repo}.items():
+        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}!")
@@ -231,6 +242,12 @@ def _prepare() -> None:
        if click.confirm("Push new SyTest branch?", default=True):
            sytest_repo.git.push("-u", sytest_repo.remote().name, release_branch_name)

+        # Same for Complement
+        if click.confirm("Push new Complement branch?", default=True):
+            complement_repo.git.push(
+                "-u", complement_repo.remote().name, release_branch_name
+            )
+
    # Switch to the release branch and ensure it's up to date.
    synapse_repo.git.checkout(release_branch_name)
    update_branch(synapse_repo)
@@ -630,6 +647,9 @@ def _merge_back() -> None:
    else:
        # Full release
        sytest_repo = get_repo_and_check_clean_checkout("../sytest", "sytest")
+        complement_repo = get_repo_and_check_clean_checkout(
+            "../complement", "complement"
+        )

        if click.confirm(f"Merge {branch_name} → master?", default=True):
            _merge_into(synapse_repo, branch_name, "master")
@@ -643,6 +663,9 @@ def _merge_back() -> None:
        if click.confirm("On SyTest, merge master → develop?", default=True):
            _merge_into(sytest_repo, "master", "develop")

+        if click.confirm(f"On Complement, merge {branch_name} → main?", default=True):
+            _merge_into(complement_repo, branch_name, "main")
+

@cli.command()
 def announce() -> None:
@@ -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 +119,19 @@ 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"],
    "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 +242,9 @@ 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"
+

 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
@@ -155,6 +158,7 @@ class GenericWorkerStore(
    LockStore,
    SessionStore,
    TaskSchedulerWorkerStore,
+    ExperimentalFeaturesStore,
 ):
    # Properties that multiple storage classes define. Tell mypy what the
    # expected type is.
@@ -163,7 +167,7 @@ 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
@@ -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,
@@ -217,7 +217,7 @@ 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(
                    {
@@ -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(
@@ -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
@@ -316,8 +317,11 @@ 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,
@@ -858,4 +913,5 @@ FEDERATION_SERVLET_CLASSES: Tuple[Type[BaseFederationServlet], ...] = (
    FederationMakeKnockServlet,
    FederationAccountStatusServlet,
    FederationMediaDownloadServlet,
+    FederationMediaThumbnailServlet,
 )
@@ -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",
@@ -39,6 +39,7 @@ from synapse.metrics.background_process_metrics import (
 )
 from synapse.storage.databases.main.client_ips import DeviceLastConnectionInfo
 from synapse.types import (
+    DeviceListUpdates,
    JsonDict,
    JsonMapping,
    ScheduledTask,
@@ -214,7 +215,7 @@ 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.
        """
@@ -341,11 +342,19 @@ class DeviceWorkerHandler:
            possibly_joined = set()
            possibly_left = set()

-        result = {"changed": list(possibly_joined), "left": list(possibly_left)}
+        device_list_updates = DeviceListUpdates(
+            changed=possibly_joined,
+            left=possibly_left,
+        )

-        log_kv(result)
+        log_kv(
+            {
+                "changed": device_list_updates.changed,
+                "left": device_list_updates.left,
+            }
+        )

-        return result
+        return device_list_updates

    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
@@ -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)
@@ -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,
@@ -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,
@@ -2268,7 +2299,11 @@ 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 +2543,7 @@ 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 +2574,7 @@ 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 +2670,10 @@ 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 +2684,9 @@ 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))
@@ -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",")
        }

@@ -74,6 +74,7 @@ from synapse.api.errors import (
 from synapse.config.homeserver import HomeServerConfig
 from synapse.logging.context import defer_to_thread, preserve_fn, run_in_background
 from synapse.logging.opentracing import active_span, start_active_span, trace_servlet
+from synapse.types import ISynapseReactor
 from synapse.util import json_encoder
 from synapse.util.caches import intern_dict
 from synapse.util.cancellation import is_function_cancellable
@@ -868,7 +869,8 @@ async def _async_write_json_to_request_in_thread(

    with start_active_span("encode_json_response"):
        span = active_span()
-        json_str = await defer_to_thread(request.reactor, encode, span)
+        reactor: ISynapseReactor = request.reactor  # type: ignore
+        json_str = await defer_to_thread(reactor, encode, span)

    _write_bytes_to_request(request, json_str)

@@ -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


@@ -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
@@ -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
@@ -271,6 +273,8 @@ 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 +282,12 @@ 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 +300,8 @@ 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 +313,21 @@ 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 +345,16 @@ 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 +369,15 @@ 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(open(file_path, "rb")),
+                    media_info,
+                )
+            else:
+                await respond_with_file(request, desired_type, file_path)
        else:
            logger.warning("Failed to generate thumbnail")
            raise SynapseError(400, "Failed to generate thumbnail.")
@@ -360,14 +393,28 @@ 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
        )
@@ -424,16 +471,29 @@ 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 +508,7 @@ 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 +522,8 @@ 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 +539,8 @@ 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 +576,20 @@ 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 +630,18 @@ 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)
@@ -145,7 +145,7 @@ class ClientRestResource(JsonResource):
        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:
+        if hs.config.media.can_load_media_repo:
            from synapse.rest.client import media

            media.register_servlets(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"],
@@ -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 +1023,32 @@ 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:
+            # 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 +1058,11 @@ 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 +1071,17 @@ 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 +1090,10 @@ 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 +1104,76 @@ 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 +62,22 @@ 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
+
+        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
+            )
+
        return (
            200,
            {
@@ -90,6 +107,7 @@ class VersionsRestServlet(RestServlet):
                    "v1.8",
                    "v1.9",
                    "v1.10",
+                    "v1.11",
                ],
                # as per MSC1497:
                "unstable_features": {
@@ -124,7 +142,7 @@ 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
@@ -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)
@@ -28,7 +28,7 @@
 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

@@ -161,6 +161,7 @@ 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 +256,13 @@ 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 +559,7 @@ 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)

@@ -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]]
@@ -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(
@@ -268,17 +268,23 @@ class CacheInvalidationWorkerStore(SQLBaseStore):
            self._curr_state_delta_stream_cache.entity_has_changed(data.room_id, token)  # type: ignore[attr-defined]

            if data.type == EventTypes.Member:
-                self.get_rooms_for_user_with_stream_ordering.invalidate(  # type: ignore[attr-defined]
-                    (data.state_key,)
+                self._attempt_to_invalidate_cache(
+                    "get_rooms_for_user", (data.state_key,)
                )
-                self.get_rooms_for_user.invalidate((data.state_key,))  # type: ignore[attr-defined]
+            elif data.type == EventTypes.RoomEncryption:
+                self._attempt_to_invalidate_cache(
+                    "get_room_encryption", (data.room_id,)
+                )
+            elif data.type == EventTypes.Create:
+                self._attempt_to_invalidate_cache("get_room_type", (data.room_id,))
        elif row.type == EventsStreamAllStateRow.TypeId:
            assert isinstance(data, EventsStreamAllStateRow)
            # Similar to the above, but the entire caches are invalidated. This is
            # unfortunate for the membership caches, but should recover quickly.
            self._curr_state_delta_stream_cache.entity_has_changed(data.room_id, token)  # type: ignore[attr-defined]
-            self.get_rooms_for_user_with_stream_ordering.invalidate_all()  # type: ignore[attr-defined]
-            self.get_rooms_for_user.invalidate_all()  # type: ignore[attr-defined]
+            self._attempt_to_invalidate_cache("get_rooms_for_user", None)
+            self._attempt_to_invalidate_cache("get_room_type", (data.room_id,))
+            self._attempt_to_invalidate_cache("get_room_encryption", (data.room_id,))
        else:
            raise Exception("Unknown events stream row type %s" % (row.type,))

@@ -334,10 +340,10 @@ class CacheInvalidationWorkerStore(SQLBaseStore):
            self._attempt_to_invalidate_cache(
                "get_invited_rooms_for_local_user", (state_key,)
            )
-            self._attempt_to_invalidate_cache(
-                "get_rooms_for_user_with_stream_ordering", (state_key,)
-            )
            self._attempt_to_invalidate_cache("get_rooms_for_user", (state_key,))
+            self._attempt_to_invalidate_cache(
+                "_get_rooms_for_local_user_where_membership_is_inner", (state_key,)
+            )

            self._attempt_to_invalidate_cache(
                "did_forget",
@@ -349,6 +355,10 @@ class CacheInvalidationWorkerStore(SQLBaseStore):
            self._attempt_to_invalidate_cache(
                "get_forgotten_rooms_for_user", (state_key,)
            )
+        elif etype == EventTypes.Create:
+            self._attempt_to_invalidate_cache("get_room_type", (room_id,))
+        elif etype == EventTypes.RoomEncryption:
+            self._attempt_to_invalidate_cache("get_room_encryption", (room_id,))

        if relates_to:
            self._attempt_to_invalidate_cache(
@@ -399,16 +409,18 @@ class CacheInvalidationWorkerStore(SQLBaseStore):
        self._attempt_to_invalidate_cache("get_thread_id", None)
        self._attempt_to_invalidate_cache("get_thread_id_for_receipts", None)
        self._attempt_to_invalidate_cache("get_invited_rooms_for_local_user", 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("did_forget", None)
        self._attempt_to_invalidate_cache("get_forgotten_rooms_for_user", None)
        self._attempt_to_invalidate_cache("get_references_for_event", None)
        self._attempt_to_invalidate_cache("get_thread_summary", None)
        self._attempt_to_invalidate_cache("get_thread_participated", None)
        self._attempt_to_invalidate_cache("get_threads", (room_id,))
+        self._attempt_to_invalidate_cache("get_room_type", (room_id,))
+        self._attempt_to_invalidate_cache("get_room_encryption", (room_id,))

        self._attempt_to_invalidate_cache("_get_state_group_for_event", None)

@@ -461,6 +473,8 @@ class CacheInvalidationWorkerStore(SQLBaseStore):
        self._attempt_to_invalidate_cache("get_forgotten_rooms_for_user", None)
        self._attempt_to_invalidate_cache("_get_membership_from_event_id", None)
        self._attempt_to_invalidate_cache("get_room_version_id", (room_id,))
+        self._attempt_to_invalidate_cache("get_room_type", (room_id,))
+        self._attempt_to_invalidate_cache("get_room_encryption", (room_id,))

        # And delete state caches.

@@ -1313,6 +1313,11 @@ class EventFederationWorkerStore(SignatureWorkerStore, EventsWorkerStore, SQLBas
        # We want to make the cache more effective, so we clamp to the last
        # change before the given ordering.
        last_change = self._events_stream_cache.get_max_pos_of_last_change(room_id)  # type: ignore[attr-defined]
+        if last_change is None:
+            # If the room isn't in the cache we know that the last change was
+            # somewhere before the earliest known position of the cache, so we
+            # can clamp to that.
+            last_change = self._events_stream_cache.get_earliest_known_position()  # type: ignore[attr-defined]

        # We don't always have a full stream_to_exterm_id table, e.g. after
        # the upgrade that introduced it, so we make sure we never ask for a
@@ -1457,7 +1457,8 @@ class EventsWorkerStore(SQLBaseStore):
                event_dict[event_id] = _EventRow(
                    event_id=event_id,
                    stream_ordering=row[1],
-                    instance_name=row[2],
+                    # If instance_name is null we default to "master"
+                    instance_name=row[2] or "master",
                    internal_metadata=row[3],
                    json=row[4],
                    format_version=row[5],
@@ -21,7 +21,11 @@

 from typing import TYPE_CHECKING, Dict, FrozenSet, List, Tuple, cast

-from synapse.storage.database import DatabasePool, LoggingDatabaseConnection
+from synapse.storage.database import (
+    DatabasePool,
+    LoggingDatabaseConnection,
+    LoggingTransaction,
+)
 from synapse.storage.databases.main import CacheInvalidationWorkerStore
 from synapse.util.caches.descriptors import cached

@@ -73,12 +77,54 @@ class ExperimentalFeaturesStore(CacheInvalidationWorkerStore):
            features:
                pairs of features and True/False for whether the feature should be enabled
        """
-        for feature, enabled in features.items():
-            await self.db_pool.simple_upsert(
-                table="per_user_experimental_features",
-                keyvalues={"feature": feature, "user_id": user},
-                values={"enabled": enabled},
-                insertion_values={"user_id": user, "feature": feature},
-            )

-            await self.invalidate_cache_and_stream("list_enabled_features", (user,))
+        def set_features_for_user_txn(txn: LoggingTransaction) -> None:
+            for feature, enabled in features.items():
+                self.db_pool.simple_upsert_txn(
+                    txn,
+                    table="per_user_experimental_features",
+                    keyvalues={"feature": feature, "user_id": user},
+                    values={"enabled": enabled},
+                    insertion_values={"user_id": user, "feature": feature},
+                )
+
+                self._invalidate_cache_and_stream(
+                    txn, self.is_feature_enabled, (user, feature)
+                )
+
+            self._invalidate_cache_and_stream(txn, self.list_enabled_features, (user,))
+
+        return await self.db_pool.runInteraction(
+            "set_features_for_user", set_features_for_user_txn
+        )
+
+    @cached()
+    async def is_feature_enabled(
+        self, user_id: str, feature: "ExperimentalFeature"
+    ) -> bool:
+        """
+        Checks to see if a given feature is enabled for the user
+        Args:
+            user_id: the user to be queried on
+            feature: the feature in question
+        Returns:
+                True if the feature is enabled, False if it is not or if the feature was
+                not found.
+        """
+
+        if feature.is_globally_enabled(self.hs.config):
+            return True
+
+        # if it's not enabled globally, check if it is enabled per-user
+        res = await self.db_pool.simple_select_one_onecol(
+            table="per_user_experimental_features",
+            keyvalues={"user_id": user_id, "feature": feature},
+            retcol="enabled",
+            allow_none=True,
+            desc="get_feature_enabled",
+        )
+
+        # None and false are treated the same
+        db_enabled = bool(res)
+
+        return db_enabled
@@ -64,6 +64,7 @@ class LocalMedia:
    quarantined_by: Optional[str]
    safe_from_quarantine: bool
    user_id: Optional[str]
+    authenticated: Optional[bool]


@attr.s(slots=True, frozen=True, auto_attribs=True)
@@ -77,6 +78,7 @@ class RemoteMedia:
    created_ts: int
    last_access_ts: int
    quarantined_by: Optional[str]
+    authenticated: Optional[bool]


@attr.s(slots=True, frozen=True, auto_attribs=True)
@@ -218,6 +220,7 @@ class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
                "last_access_ts",
                "safe_from_quarantine",
                "user_id",
+                "authenticated",
            ),
            allow_none=True,
            desc="get_local_media",
@@ -235,6 +238,7 @@ class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
            last_access_ts=row[6],
            safe_from_quarantine=row[7],
            user_id=row[8],
+            authenticated=row[9],
        )

    async def get_local_media_by_user_paginate(
@@ -290,7 +294,8 @@ class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
                    last_access_ts,
                    quarantined_by,
                    safe_from_quarantine,
-                    user_id
+                    user_id,
+                    authenticated
                FROM local_media_repository
                WHERE user_id = ?
                ORDER BY {order_by_column} {order}, media_id ASC
@@ -314,6 +319,7 @@ class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
                    quarantined_by=row[7],
                    safe_from_quarantine=bool(row[8]),
                    user_id=row[9],
+                    authenticated=row[10],
                )
                for row in txn
            ]
@@ -417,12 +423,18 @@ class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
        time_now_ms: int,
        user_id: UserID,
    ) -> None:
+        if self.hs.config.media.enable_authenticated_media:
+            authenticated = True
+        else:
+            authenticated = False
+
        await self.db_pool.simple_insert(
            "local_media_repository",
            {
                "media_id": media_id,
                "created_ts": time_now_ms,
                "user_id": user_id.to_string(),
+                "authenticated": authenticated,
            },
            desc="store_local_media_id",
        )
@@ -438,6 +450,11 @@ class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
        user_id: UserID,
        url_cache: Optional[str] = None,
    ) -> None:
+        if self.hs.config.media.enable_authenticated_media:
+            authenticated = True
+        else:
+            authenticated = False
+
        await self.db_pool.simple_insert(
            "local_media_repository",
            {
@@ -448,6 +465,7 @@ class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
                "media_length": media_length,
                "user_id": user_id.to_string(),
                "url_cache": url_cache,
+                "authenticated": authenticated,
            },
            desc="store_local_media",
        )
@@ -638,6 +656,7 @@ class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
                "filesystem_id",
                "last_access_ts",
                "quarantined_by",
+                "authenticated",
            ),
            allow_none=True,
            desc="get_cached_remote_media",
@@ -654,6 +673,7 @@ class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
            filesystem_id=row[4],
            last_access_ts=row[5],
            quarantined_by=row[6],
+            authenticated=row[7],
        )

    async def store_cached_remote_media(
@@ -666,6 +686,11 @@ class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
        upload_name: Optional[str],
        filesystem_id: str,
    ) -> None:
+        if self.hs.config.media.enable_authenticated_media:
+            authenticated = True
+        else:
+            authenticated = False
+
        await self.db_pool.simple_insert(
            "remote_media_cache",
            {
@@ -677,6 +702,7 @@ class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
                "upload_name": upload_name,
                "filesystem_id": filesystem_id,
                "last_access_ts": time_now_ms,
+                "authenticated": authenticated,
            },
            desc="store_cached_remote_media",
        )
@@ -39,6 +39,7 @@ from typing import (
 import attr

 from synapse.api.constants import EventTypes, Membership
+from synapse.logging.opentracing import trace
 from synapse.metrics import LaterGauge
 from synapse.metrics.background_process_metrics import wrap_as_background_process
 from synapse.storage._base import SQLBaseStore, db_to_json, make_in_list_sql_clause
@@ -50,12 +51,7 @@ from synapse.storage.database import (
 from synapse.storage.databases.main.cache import CacheInvalidationWorkerStore
 from synapse.storage.databases.main.events_worker import EventsWorkerStore
 from synapse.storage.engines import Sqlite3Engine
-from synapse.storage.roommember import (
-    GetRoomsForUserWithStreamOrdering,
-    MemberSummary,
-    ProfileInfo,
-    RoomsForUser,
-)
+from synapse.storage.roommember import MemberSummary, ProfileInfo, RoomsForUser
 from synapse.types import (
    JsonDict,
    PersistedEventPosition,
@@ -284,8 +280,19 @@ class RoomMemberWorkerStore(EventsWorkerStore, CacheInvalidationWorkerStore):

    @cached(max_entries=100000)  # type: ignore[synapse-@cached-mutable]
    async def get_room_summary(self, room_id: str) -> Mapping[str, MemberSummary]:
-        """Get the details of a room roughly suitable for use by the room
+        """
+        Get the details of a room roughly suitable for use by the room
        summary extension to /sync. Useful when lazy loading room members.
+
+        Returns the total count of members in the room by membership type, and a
+        truncated list of members (the heroes). This will be the first 6 members of the
+        room:
+        - We want 5 heroes plus 1, in case one of them is the
+        calling user.
+        - They are ordered by `stream_ordering`, which are joined or
+        invited. When no joined or invited members are available, this also includes
+        banned and left users.
+
        Args:
            room_id: The room ID to query
        Returns:
@@ -313,23 +320,36 @@ class RoomMemberWorkerStore(EventsWorkerStore, CacheInvalidationWorkerStore):
            for count, membership in txn:
                res.setdefault(membership, MemberSummary([], count))

-            # we order by membership and then fairly arbitrarily by event_id so
-            # heroes are consistent
-            # Note, rejected events will have a null membership field, so
-            # we we manually filter them out.
+            # Order by membership (joins -> invites -> leave (former insiders) ->
+            # everything else (outsiders like bans/knocks), then by `stream_ordering` so
+            # the first members in the room show up first and to make the sort stable
+            # (consistent heroes).
+            #
+            # Note: rejected events will have a null membership field, so we we manually
+            # filter them out.
            sql = """
                SELECT state_key, membership, event_id
                FROM current_state_events
                WHERE type = 'm.room.member' AND room_id = ?
                    AND membership IS NOT NULL
                ORDER BY
-                    CASE membership WHEN ? THEN 1 WHEN ? THEN 2 ELSE 3 END ASC,
-                    event_id ASC
+                    CASE membership WHEN ? THEN 1 WHEN ? THEN 2 WHEN ? THEN 3 ELSE 4 END ASC,
+                    event_stream_ordering ASC
                LIMIT ?
            """

-            # 6 is 5 (number of heroes) plus 1, in case one of them is the calling user.
-            txn.execute(sql, (room_id, Membership.JOIN, Membership.INVITE, 6))
+            txn.execute(
+                sql,
+                (
+                    room_id,
+                    # Sort order
+                    Membership.JOIN,
+                    Membership.INVITE,
+                    Membership.LEAVE,
+                    # 6 is 5 (number of heroes) plus 1, in case one of them is the calling user.
+                    6,
+                ),
+            )
            for user_id, membership, event_id in txn:
                summary = res[membership]
                # we will always have a summary for this membership type at this
@@ -403,6 +423,7 @@ class RoomMemberWorkerStore(EventsWorkerStore, CacheInvalidationWorkerStore):
                return invite
        return None

+    @trace
    async def get_rooms_for_local_user_where_membership_is(
        self,
        user_id: str,
@@ -426,9 +447,11 @@ class RoomMemberWorkerStore(EventsWorkerStore, CacheInvalidationWorkerStore):
        if not membership_list:
            return []

-        rooms = await self.db_pool.runInteraction(
-            "get_rooms_for_local_user_where_membership_is",
-            self._get_rooms_for_local_user_where_membership_is_txn,
+        # Convert membership list to frozen set as a) it needs to be hashable,
+        # and b) we don't care about the order.
+        membership_list = frozenset(membership_list)
+
+        rooms = await self._get_rooms_for_local_user_where_membership_is_inner(
            user_id,
            membership_list,
        )
@@ -447,6 +470,24 @@ class RoomMemberWorkerStore(EventsWorkerStore, CacheInvalidationWorkerStore):

        return [room for room in rooms if room.room_id not in rooms_to_exclude]

+    @cached(max_entries=1000, tree=True)
+    async def _get_rooms_for_local_user_where_membership_is_inner(
+        self,
+        user_id: str,
+        membership_list: Collection[str],
+    ) -> Sequence[RoomsForUser]:
+        if not membership_list:
+            return []
+
+        rooms = await self.db_pool.runInteraction(
+            "get_rooms_for_local_user_where_membership_is",
+            self._get_rooms_for_local_user_where_membership_is_txn,
+            user_id,
+            membership_list,
+        )
+
+        return rooms
+
    def _get_rooms_for_local_user_where_membership_is_txn(
        self,
        txn: LoggingTransaction,
@@ -494,7 +535,11 @@ class RoomMemberWorkerStore(EventsWorkerStore, CacheInvalidationWorkerStore):
                sender=sender,
                membership=membership,
                event_id=event_id,
-                event_pos=PersistedEventPosition(instance_name, stream_ordering),
+                event_pos=PersistedEventPosition(
+                    # If instance_name is null we default to "master"
+                    instance_name or "master",
+                    stream_ordering,
+                ),
                room_version_id=room_version,
            )
            for room_id, sender, membership, event_id, instance_name, stream_ordering, room_version in txn
@@ -606,53 +651,6 @@ class RoomMemberWorkerStore(EventsWorkerStore, CacheInvalidationWorkerStore):

        return results

-    @cached(max_entries=500000, iterable=True)
-    async def get_rooms_for_user_with_stream_ordering(
-        self, user_id: str
-    ) -> FrozenSet[GetRoomsForUserWithStreamOrdering]:
-        """Returns a set of room_ids the user is currently joined to.
-
-        If a remote user only returns rooms this server is currently
-        participating in.
-
-        Args:
-            user_id
-
-        Returns:
-            Returns the rooms the user is in currently, along with the stream
-            ordering of the most recent join for that user and room, along with
-            the room version of the room.
-        """
-        return await self.db_pool.runInteraction(
-            "get_rooms_for_user_with_stream_ordering",
-            self._get_rooms_for_user_with_stream_ordering_txn,
-            user_id,
-        )
-
-    def _get_rooms_for_user_with_stream_ordering_txn(
-        self, txn: LoggingTransaction, user_id: str
-    ) -> FrozenSet[GetRoomsForUserWithStreamOrdering]:
-        # We use `current_state_events` here and not `local_current_membership`
-        # as a) this gets called with remote users and b) this only gets called
-        # for rooms the server is participating in.
-        sql = """
-            SELECT room_id, e.instance_name, e.stream_ordering
-            FROM current_state_events AS c
-            INNER JOIN events AS e USING (room_id, event_id)
-            WHERE
-                c.type = 'm.room.member'
-                AND c.state_key = ?
-                AND c.membership = ?
-        """
-
-        txn.execute(sql, (user_id, Membership.JOIN))
-        return frozenset(
-            GetRoomsForUserWithStreamOrdering(
-                room_id, PersistedEventPosition(instance, stream_id)
-            )
-            for room_id, instance, stream_id in txn
-        )
-
    async def get_users_server_still_shares_room_with(
        self, user_ids: Collection[str]
    ) -> Set[str]:
@@ -701,13 +699,6 @@ class RoomMemberWorkerStore(EventsWorkerStore, CacheInvalidationWorkerStore):
        If a remote user only returns rooms this server is currently
        participating in.
        """
-        rooms = self.get_rooms_for_user_with_stream_ordering.cache.get_immediate(
-            (user_id,),
-            None,
-            update_metrics=False,
-        )
-        if rooms:
-            return frozenset(r.room_id for r in rooms)

        room_ids = await self.db_pool.simple_select_onecol(
            table="current_state_events",
@@ -1564,10 +1555,19 @@ def extract_heroes_from_room_summary(
 ) -> List[str]:
    """Determine the users that represent a room, from the perspective of the `me` user.

+    This function expects `MemberSummary.members` to already be sorted by
+    `stream_ordering` like the results from `get_room_summary(...)`.
+
    The rules which say which users we select are specified in the "Room Summary"
    section of
    https://spec.matrix.org/v1.4/client-server-api/#get_matrixclientv3sync

+
+    Args:
+        details: Mapping from membership type to member summary. We expect
+            `MemberSummary.members` to already be sorted by `stream_ordering`.
+        me: The user for whom we are determining the heroes for.
+
    Returns a list (possibly empty) of heroes' mxids.
    """
    empty_ms = MemberSummary([], 0)
@@ -1582,11 +1582,11 @@ def extract_heroes_from_room_summary(
        r[0] for r in details.get(Membership.LEAVE, empty_ms).members if r[0] != me
    ] + [r[0] for r in details.get(Membership.BAN, empty_ms).members if r[0] != me]

-    # FIXME: order by stream ordering rather than as returned by SQL
+    # We expect `MemberSummary.members` to already be sorted by `stream_ordering`
    if joined_user_ids or invited_user_ids:
-        return sorted(joined_user_ids + invited_user_ids)[0:5]
+        return (joined_user_ids + invited_user_ids)[0:5]
    else:
-        return sorted(gone_user_ids)[0:5]
+        return gone_user_ids[0:5]


@attr.s(slots=True, auto_attribs=True)
@@ -30,6 +30,7 @@ from typing import (
    Iterable,
    List,
    Mapping,
+    MutableMapping,
    Optional,
    Set,
    Tuple,
@@ -41,7 +42,7 @@ from typing import (

 import attr

-from synapse.api.constants import EventTypes, Membership
+from synapse.api.constants import EventContentFields, EventTypes, Membership
 from synapse.api.errors import NotFoundError, UnsupportedRoomVersionError
 from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, RoomVersion
 from synapse.events import EventBase
@@ -72,10 +73,18 @@ logger = logging.getLogger(__name__)

 _T = TypeVar("_T")

-
 MAX_STATE_DELTA_HOPS = 100


+# Freeze so it's immutable and we can use it as a cache value
+@attr.s(slots=True, frozen=True, auto_attribs=True)
+class Sentinel:
+    pass
+
+
+ROOM_UNKNOWN_SENTINEL = Sentinel()
+
+
@attr.s(slots=True, frozen=True, auto_attribs=True)
 class EventMetadata:
    """Returned by `get_metadata_for_events`"""
@@ -298,6 +307,194 @@ class StateGroupWorkerStore(EventsWorkerStore, SQLBaseStore):
        create_event = await self.get_event(create_id)
        return create_event

+    @cached(max_entries=10000)
+    async def get_room_type(self, room_id: str) -> Optional[str]:
+        raise NotImplementedError()
+
+    @cachedList(cached_method_name="get_room_type", list_name="room_ids")
+    async def bulk_get_room_type(
+        self, room_ids: Set[str]
+    ) -> Mapping[str, Union[Optional[str], Sentinel]]:
+        """
+        Bulk fetch room types for the given rooms (via current state).
+
+        Since this function is cached, any missing values would be cached as `None`. In
+        order to distinguish between an unencrypted room that has `None` encryption and
+        a room that is unknown to the server where we might want to omit the value
+        (which would make it cached as `None`), instead we use the sentinel value
+        `ROOM_UNKNOWN_SENTINEL`.
+
+        Returns:
+            A mapping from room ID to the room's type (`None` is a valid room type).
+            Rooms unknown to this server will return `ROOM_UNKNOWN_SENTINEL`.
+        """
+
+        def txn(
+            txn: LoggingTransaction,
+        ) -> MutableMapping[str, Union[Optional[str], Sentinel]]:
+            clause, args = make_in_list_sql_clause(
+                txn.database_engine, "room_id", room_ids
+            )
+
+            # We can't rely on `room_stats_state.room_type` if the server has left the
+            # room because the `room_id` will still be in the table but everything will
+            # be set to `None` but `None` is a valid room type value. We join against
+            # the `room_stats_current` table which keeps track of the
+            # `current_state_events` count (and a proxy value `local_users_in_room`
+            # which can used to assume the server is participating in the room and has
+            # current state) to ensure that the data in `room_stats_state` is up-to-date
+            # with the current state.
+            #
+            # FIXME: Use `room_stats_current.current_state_events` instead of
+            # `room_stats_current.local_users_in_room` once
+            # https://github.com/element-hq/synapse/issues/17457 is fixed.
+            sql = f"""
+                SELECT room_id, room_type
+                FROM room_stats_state
+                INNER JOIN room_stats_current USING (room_id)
+                WHERE
+                    {clause}
+                    AND local_users_in_room > 0
+            """
+
+            txn.execute(sql, args)
+
+            room_id_to_type_map = {}
+            for row in txn:
+                room_id_to_type_map[row[0]] = row[1]
+
+            return room_id_to_type_map
+
+        results = await self.db_pool.runInteraction(
+            "bulk_get_room_type",
+            txn,
+        )
+
+        # If we haven't updated `room_stats_state` with the room yet, query the
+        # create events directly. This should happen only rarely so we don't
+        # mind if we do this in a loop.
+        for room_id in room_ids - results.keys():
+            try:
+                create_event = await self.get_create_event_for_room(room_id)
+                room_type = create_event.content.get(EventContentFields.ROOM_TYPE)
+                results[room_id] = room_type
+            except NotFoundError:
+                # We use the sentinel value to distinguish between `None` which is a
+                # valid room type and a room that is unknown to the server so the value
+                # is just unset.
+                results[room_id] = ROOM_UNKNOWN_SENTINEL
+
+        return results
+
+    @cached(max_entries=10000)
+    async def get_room_encryption(self, room_id: str) -> Optional[str]:
+        raise NotImplementedError()
+
+    @cachedList(cached_method_name="get_room_encryption", list_name="room_ids")
+    async def bulk_get_room_encryption(
+        self, room_ids: Set[str]
+    ) -> Mapping[str, Union[Optional[str], Sentinel]]:
+        """
+        Bulk fetch room encryption for the given rooms (via current state).
+
+        Since this function is cached, any missing values would be cached as `None`. In
+        order to distinguish between an unencrypted room that has `None` encryption and
+        a room that is unknown to the server where we might want to omit the value
+        (which would make it cached as `None`), instead we use the sentinel value
+        `ROOM_UNKNOWN_SENTINEL`.
+
+        Returns:
+            A mapping from room ID to the room's encryption algorithm if the room is
+            encrypted, otherwise `None`. Rooms unknown to this server will return
+            `ROOM_UNKNOWN_SENTINEL`.
+        """
+
+        def txn(
+            txn: LoggingTransaction,
+        ) -> MutableMapping[str, Union[Optional[str], Sentinel]]:
+            clause, args = make_in_list_sql_clause(
+                txn.database_engine, "room_id", room_ids
+            )
+
+            # We can't rely on `room_stats_state.encryption` if the server has left the
+            # room because the `room_id` will still be in the table but everything will
+            # be set to `None` but `None` is a valid encryption value. We join against
+            # the `room_stats_current` table which keeps track of the
+            # `current_state_events` count (and a proxy value `local_users_in_room`
+            # which can used to assume the server is participating in the room and has
+            # current state) to ensure that the data in `room_stats_state` is up-to-date
+            # with the current state.
+            #
+            # FIXME: Use `room_stats_current.current_state_events` instead of
+            # `room_stats_current.local_users_in_room` once
+            # https://github.com/element-hq/synapse/issues/17457 is fixed.
+            sql = f"""
+                SELECT room_id, encryption
+                FROM room_stats_state
+                INNER JOIN room_stats_current USING (room_id)
+                WHERE
+                    {clause}
+                    AND local_users_in_room > 0
+            """
+
+            txn.execute(sql, args)
+
+            room_id_to_encryption_map = {}
+            for row in txn:
+                room_id_to_encryption_map[row[0]] = row[1]
+
+            return room_id_to_encryption_map
+
+        results = await self.db_pool.runInteraction(
+            "bulk_get_room_encryption",
+            txn,
+        )
+
+        # If we haven't updated `room_stats_state` with the room yet, query the state
+        # directly. This should happen only rarely so we don't mind if we do this in a
+        # loop.
+        encryption_event_ids: List[str] = []
+        for room_id in room_ids - results.keys():
+            state_map = await self.get_partial_filtered_current_state_ids(
+                room_id,
+                state_filter=StateFilter.from_types(
+                    [
+                        (EventTypes.Create, ""),
+                        (EventTypes.RoomEncryption, ""),
+                    ]
+                ),
+            )
+            # We can use the create event as a canary to tell whether the server has
+            # seen the room before
+            create_event_id = state_map.get((EventTypes.Create, ""))
+            encryption_event_id = state_map.get((EventTypes.RoomEncryption, ""))
+
+            if create_event_id is None:
+                # We use the sentinel value to distinguish between `None` which is a
+                # valid room type and a room that is unknown to the server so the value
+                # is just unset.
+                results[room_id] = ROOM_UNKNOWN_SENTINEL
+                continue
+
+            if encryption_event_id is None:
+                results[room_id] = None
+            else:
+                encryption_event_ids.append(encryption_event_id)
+
+        encryption_event_map = await self.get_events(encryption_event_ids)
+
+        for encryption_event_id in encryption_event_ids:
+            encryption_event = encryption_event_map.get(encryption_event_id)
+            # If the curent state says there is an encryption event, we should have it
+            # in the database.
+            assert encryption_event is not None
+
+            results[encryption_event.room_id] = encryption_event.content.get(
+                EventContentFields.ENCRYPTION_ALGORITHM
+            )
+
+        return results
+
    @cached(max_entries=100000, iterable=True)
    async def get_partial_current_state_ids(self, room_id: str) -> StateMap[str]:
        """Get the current state event ids for a room based on the
@@ -24,8 +24,11 @@ from typing import List, Optional, Tuple

 import attr

+from synapse.logging.opentracing import trace
 from synapse.storage._base import SQLBaseStore
 from synapse.storage.database import LoggingTransaction
+from synapse.storage.databases.main.stream import _filter_results_by_stream
+from synapse.types import RoomStreamToken
 from synapse.util.caches.stream_change_cache import StreamChangeCache

 logger = logging.getLogger(__name__)
@@ -156,3 +159,39 @@ class StateDeltasStore(SQLBaseStore):
            "get_max_stream_id_in_current_state_deltas",
            self._get_max_stream_id_in_current_state_deltas_txn,
        )
+
+    @trace
+    async def get_current_state_deltas_for_room(
+        self, room_id: str, from_token: RoomStreamToken, to_token: RoomStreamToken
+    ) -> List[StateDelta]:
+        """Get the state deltas between two tokens."""
+
+        def get_current_state_deltas_for_room_txn(
+            txn: LoggingTransaction,
+        ) -> List[StateDelta]:
+            sql = """
+                SELECT instance_name, stream_id, type, state_key, event_id, prev_event_id
+                FROM current_state_delta_stream
+                WHERE room_id = ? AND ? < stream_id AND stream_id <= ?
+                ORDER BY stream_id ASC
+            """
+            txn.execute(
+                sql, (room_id, from_token.stream, to_token.get_max_stream_pos())
+            )
+
+            return [
+                StateDelta(
+                    stream_id=row[1],
+                    room_id=room_id,
+                    event_type=row[2],
+                    state_key=row[3],
+                    event_id=row[4],
+                    prev_event_id=row[5],
+                )
+                for row in txn
+                if _filter_results_by_stream(from_token, to_token, row[0], row[1])
+            ]
+
+        return await self.db_pool.runInteraction(
+            "get_current_state_deltas_for_room", get_current_state_deltas_for_room_txn
+        )
@@ -51,6 +51,7 @@ from typing import (
    Iterable,
    List,
    Optional,
+    Protocol,
    Set,
    Tuple,
    cast,
@@ -59,7 +60,7 @@ from typing import (

 import attr
 from immutabledict import immutabledict
-from typing_extensions import Literal
+from typing_extensions import Literal, assert_never

 from twisted.internet import defer

@@ -67,7 +68,7 @@ from synapse.api.constants import Direction, EventTypes, Membership
 from synapse.api.filtering import Filter
 from synapse.events import EventBase
 from synapse.logging.context import make_deferred_yieldable, run_in_background
-from synapse.logging.opentracing import trace
+from synapse.logging.opentracing import tag_args, trace
 from synapse.storage._base import SQLBaseStore
 from synapse.storage.database import (
    DatabasePool,
@@ -78,10 +79,11 @@ from synapse.storage.database import (
 from synapse.storage.databases.main.events_worker import EventsWorkerStore
 from synapse.storage.engines import BaseDatabaseEngine, PostgresEngine, Sqlite3Engine
 from synapse.storage.util.id_generators import MultiWriterIdGenerator
-from synapse.types import PersistedEventPosition, RoomStreamToken
+from synapse.types import PersistedEventPosition, RoomStreamToken, StrCollection
 from synapse.util.caches.descriptors import cached
 from synapse.util.caches.stream_change_cache import StreamChangeCache
 from synapse.util.cancellation import cancellable
+from synapse.util.iterutils import batch_iter

 if TYPE_CHECKING:
    from synapse.server import HomeServer
@@ -96,6 +98,18 @@ _STREAM_TOKEN = "stream"
 _TOPOLOGICAL_TOKEN = "topological"


+class PaginateFunction(Protocol):
+    async def __call__(
+        self,
+        *,
+        room_id: str,
+        from_key: RoomStreamToken,
+        to_key: Optional[RoomStreamToken] = None,
+        direction: Direction = Direction.BACKWARDS,
+        limit: int = 0,
+    ) -> Tuple[List[EventBase], RoomStreamToken]: ...
+
+
 # Used as return values for pagination APIs
@attr.s(slots=True, frozen=True, auto_attribs=True)
 class _EventDictReturn:
@@ -279,7 +293,7 @@ def generate_pagination_bounds(


 def generate_next_token(
-    direction: Direction, last_topo_ordering: int, last_stream_ordering: int
+    direction: Direction, last_topo_ordering: Optional[int], last_stream_ordering: int
 ) -> RoomStreamToken:
    """
    Generate the next room stream token based on the currently returned data.
@@ -371,7 +385,7 @@ def _make_generic_sql_bound(
 def _filter_results(
    lower_token: Optional[RoomStreamToken],
    upper_token: Optional[RoomStreamToken],
-    instance_name: str,
+    instance_name: Optional[str],
    topological_ordering: int,
    stream_ordering: int,
 ) -> bool:
@@ -384,8 +398,14 @@ def _filter_results(
    position maps, which we handle by fetching more than necessary from the DB
    and then filtering (rather than attempting to construct a complicated SQL
    query).
+
+    The `instance_name` arg is optional to handle historic rows, and is
+    interpreted as if it was "master".
    """

+    if instance_name is None:
+        instance_name = "master"
+
    event_historical_tuple = (
        topological_ordering,
        stream_ordering,
@@ -420,7 +440,7 @@ def _filter_results(
 def _filter_results_by_stream(
    lower_token: Optional[RoomStreamToken],
    upper_token: Optional[RoomStreamToken],
-    instance_name: str,
+    instance_name: Optional[str],
    stream_ordering: int,
 ) -> bool:
    """
@@ -436,7 +456,13 @@ def _filter_results_by_stream(
    position maps, which we handle by fetching more than necessary from the DB
    and then filtering (rather than attempting to construct a complicated SQL
    query).
+
+    The `instance_name` arg is optional to handle historic rows, and is
+    interpreted as if it was "master".
    """
+    if instance_name is None:
+        instance_name = "master"
+
    if lower_token:
        assert lower_token.topological is None

@@ -646,33 +672,43 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):

    async def get_room_events_stream_for_rooms(
        self,
+        *,
        room_ids: Collection[str],
        from_key: RoomStreamToken,
-        to_key: RoomStreamToken,
+        to_key: Optional[RoomStreamToken] = None,
+        direction: Direction = Direction.BACKWARDS,
        limit: int = 0,
-        order: str = "DESC",
    ) -> Dict[str, Tuple[List[EventBase], RoomStreamToken]]:
        """Get new room events in stream ordering since `from_key`.

        Args:
            room_ids
-            from_key: Token from which no events are returned before
-            to_key: Token from which no events are returned after. (This
-                is typically the current stream token)
+            from_key: The token to stream from (starting point and heading in the given
+                direction)
+            to_key: The token representing the end stream position (end point)
            limit: Maximum number of events to return
-            order: Either "DESC" or "ASC". Determines which events are
-                returned when the result is limited. If "DESC" then the most
-                recent `limit` events are returned, otherwise returns the
-                oldest `limit` events.
+            direction: Indicates whether we are paginating forwards or backwards
+                from `from_key`.

        Returns:
            A map from room id to a tuple containing:
                - list of recent events in the room
                - stream ordering key for the start of the chunk of events returned.
+
+            When Direction.FORWARDS: from_key < x <= to_key, (ascending order)
+            When Direction.BACKWARDS: from_key >= x > to_key, (descending order)
        """
-        room_ids = self._events_stream_cache.get_entities_changed(
-            room_ids, from_key.stream
-        )
+        if direction == Direction.FORWARDS:
+            room_ids = self._events_stream_cache.get_entities_changed(
+                room_ids, from_key.stream
+            )
+        elif direction == Direction.BACKWARDS:
+            if to_key is not None:
+                room_ids = self._events_stream_cache.get_entities_changed(
+                    room_ids, to_key.stream
+                )
+        else:
+            assert_never(direction)

        if not room_ids:
            return {}
@@ -684,12 +720,12 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
                defer.gatherResults(
                    [
                        run_in_background(
-                            self.get_room_events_stream_for_room,
-                            room_id,
-                            from_key,
-                            to_key,
-                            limit,
-                            order=order,
+                            self.paginate_room_events_by_stream_ordering,
+                            room_id=room_id,
+                            from_key=from_key,
+                            to_key=to_key,
+                            direction=direction,
+                            limit=limit,
                        )
                        for room_id in rm_ids
                    ],
@@ -713,69 +749,122 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
            if self._events_stream_cache.has_entity_changed(room_id, from_id)
        }

-    async def get_room_events_stream_for_room(
+    async def paginate_room_events_by_stream_ordering(
        self,
+        *,
        room_id: str,
        from_key: RoomStreamToken,
-        to_key: RoomStreamToken,
+        to_key: Optional[RoomStreamToken] = None,
+        direction: Direction = Direction.BACKWARDS,
        limit: int = 0,
-        order: str = "DESC",
    ) -> Tuple[List[EventBase], RoomStreamToken]:
-        """Get new room events in stream ordering since `from_key`.
+        """
+        Paginate events by `stream_ordering` in the room from the `from_key` in the
+        given `direction` to the `to_key` or `limit`.

        Args:
            room_id
-            from_key: Token from which no events are returned before
-            to_key: Token from which no events are returned after. (This
-                is typically the current stream token)
+            from_key: The token to stream from (starting point and heading in the given
+                direction)
+            to_key: The token representing the end stream position (end point)
+            direction: Indicates whether we are paginating forwards or backwards
+                from `from_key`.
            limit: Maximum number of events to return
-            order: Either "DESC" or "ASC". Determines which events are
-                returned when the result is limited. If "DESC" then the most
-                recent `limit` events are returned, otherwise returns the
-                oldest `limit` events.

        Returns:
-            The list of events (in ascending stream order) and the token from the start
-            of the chunk of events returned.
-        """
-        if from_key == to_key:
-            return [], from_key
+            The results as a list of events and a token that points to the end
+            of the result set. If no events are returned then the end of the
+            stream has been reached (i.e. there are no events between `from_key`
+            and `to_key`).

-        has_changed = self._events_stream_cache.has_entity_changed(
-            room_id, from_key.stream
-        )
+            When Direction.FORWARDS: from_key < x <= to_key, (ascending order)
+            When Direction.BACKWARDS: from_key >= x > to_key, (descending order)
+        """
+
+        # FIXME: When going forwards, we should enforce that the `to_key` is not `None`
+        # because we always need an upper bound when querying the events stream (as
+        # otherwise we'll potentially pick up events that are not fully persisted).
+
+        # We should only be working with `stream_ordering` tokens here
+        assert from_key is None or from_key.topological is None
+        assert to_key is None or to_key.topological is None
+
+        # We can bail early if we're looking forwards, and our `to_key` is already
+        # before our `from_key`.
+        if (
+            direction == Direction.FORWARDS
+            and to_key is not None
+            and to_key.is_before_or_eq(from_key)
+        ):
+            # Token selection matches what we do below if there are no rows
+            return [], to_key if to_key else from_key
+        # Or vice-versa, if we're looking backwards and our `from_key` is already before
+        # our `to_key`.
+        elif (
+            direction == Direction.BACKWARDS
+            and to_key is not None
+            and from_key.is_before_or_eq(to_key)
+        ):
+            # Token selection matches what we do below if there are no rows
+            return [], to_key if to_key else from_key
+
+        # We can do a quick sanity check to see if any events have been sent in the room
+        # since the earlier token.
+        has_changed = True
+        if direction == Direction.FORWARDS:
+            has_changed = self._events_stream_cache.has_entity_changed(
+                room_id, from_key.stream
+            )
+        elif direction == Direction.BACKWARDS:
+            if to_key is not None:
+                has_changed = self._events_stream_cache.has_entity_changed(
+                    room_id, to_key.stream
+                )
+        else:
+            assert_never(direction)

        if not has_changed:
-            return [], from_key
+            # Token selection matches what we do below if there are no rows
+            return [], to_key if to_key else from_key
+
+        order, from_bound, to_bound = generate_pagination_bounds(
+            direction, from_key, to_key
+        )
+
+        bounds = generate_pagination_where_clause(
+            direction=direction,
+            # The empty string will shortcut downstream code to only use the
+            # `stream_ordering` column
+            column_names=("", "stream_ordering"),
+            from_token=from_bound,
+            to_token=to_bound,
+            engine=self.database_engine,
+        )

        def f(txn: LoggingTransaction) -> List[_EventDictReturn]:
-            # To handle tokens with a non-empty instance_map we fetch more
-            # results than necessary and then filter down
-            min_from_id = from_key.stream
-            max_to_id = to_key.get_max_stream_pos()
-
-            sql = """
-                SELECT event_id, instance_name, topological_ordering, stream_ordering
+            sql = f"""
+                SELECT event_id, instance_name, stream_ordering
                FROM events
                WHERE
                    room_id = ?
                    AND not outlier
-                    AND stream_ordering > ? AND stream_ordering <= ?
-                ORDER BY stream_ordering %s LIMIT ?
-            """ % (
-                order,
-            )
-            txn.execute(sql, (room_id, min_from_id, max_to_id, 2 * limit))
+                    AND {bounds}
+                ORDER BY stream_ordering {order} LIMIT ?
+            """
+            txn.execute(sql, (room_id, 2 * limit))

            rows = [
                _EventDictReturn(event_id, None, stream_ordering)
-                for event_id, instance_name, topological_ordering, stream_ordering in txn
-                if _filter_results(
-                    from_key,
-                    to_key,
-                    instance_name,
-                    topological_ordering,
-                    stream_ordering,
+                for event_id, instance_name, stream_ordering in txn
+                if _filter_results_by_stream(
+                    lower_token=(
+                        to_key if direction == Direction.BACKWARDS else from_key
+                    ),
+                    upper_token=(
+                        from_key if direction == Direction.BACKWARDS else to_key
+                    ),
+                    instance_name=instance_name,
+                    stream_ordering=stream_ordering,
                )
            ][:limit]
            return rows
@@ -786,18 +875,20 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
            [r.event_id for r in rows], get_prev_content=True
        )

-        if order.lower() == "desc":
-            ret.reverse()
-
        if rows:
-            key = RoomStreamToken(stream=min(r.stream_ordering for r in rows))
+            next_key = generate_next_token(
+                direction=direction,
+                last_topo_ordering=None,
+                last_stream_ordering=rows[-1].stream_ordering,
+            )
        else:
-            # Assume we didn't get anything because there was nothing to
-            # get.
-            key = from_key
+            # TODO (erikj): We should work out what to do here instead. (same as
+            # `_paginate_room_events_by_topological_ordering_txn(...)`)
+            next_key = to_key if to_key else from_key

-        return ret, key
+        return ret, next_key

+    @trace
    async def get_current_state_delta_membership_changes_for_user(
        self,
        user_id: str,
@@ -912,7 +1003,6 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
                prev_sender,
            ) in txn:
                assert room_id is not None
-                assert instance_name is not None
                assert stream_ordering is not None

                if _filter_results_by_stream(
@@ -936,7 +1026,8 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
                        # Event
                        event_id=event_id,
                        event_pos=PersistedEventPosition(
-                            instance_name=instance_name,
+                            # If instance_name is null we default to "master"
+                            instance_name=instance_name or "master",
                            stream=stream_ordering,
                        ),
                        # When `s.event_id = null`, we won't be able to get respective
@@ -952,13 +1043,11 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
                        prev_event_id=prev_event_id,
                        prev_event_pos=(
                            PersistedEventPosition(
-                                instance_name=prev_instance_name,
+                                # If instance_name is null we default to "master"
+                                instance_name=prev_instance_name or "master",
                                stream=prev_stream_ordering,
                            )
-                            if (
-                                prev_instance_name is not None
-                                and prev_stream_ordering is not None
-                            )
+                            if (prev_stream_ordering is not None)
                            else None
                        ),
                        prev_membership=prev_membership,
@@ -1105,7 +1194,7 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):

        rows, token = await self.db_pool.runInteraction(
            "get_recent_event_ids_for_room",
-            self._paginate_room_events_txn,
+            self._paginate_room_events_by_topological_ordering_txn,
            room_id,
            from_token=end_token,
            limit=limit,
@@ -1174,10 +1263,12 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):

        return None

+    @trace
    async def get_last_event_pos_in_room_before_stream_ordering(
        self,
        room_id: str,
        end_token: RoomStreamToken,
+        event_types: Optional[Collection[str]] = None,
    ) -> Optional[Tuple[str, PersistedEventPosition]]:
        """
        Returns the ID and event position of the last event in a room at or before a
@@ -1186,6 +1277,7 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
        Args:
            room_id
            end_token: The token used to stream from
+            event_types: Optional allowlist of event types to filter by

        Returns:
            The ID of the most recent event and it's position, or None if there are no
@@ -1207,9 +1299,17 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
            min_stream = end_token.stream
            max_stream = end_token.get_max_stream_pos()

-            # We use `union all` because we don't need any of the deduplication logic
-            # (`union` is really a union + distinct). `UNION ALL` does preserve the
-            # ordering of the operand queries but there is no actual gurantee that it
+            event_type_clause = ""
+            event_type_args: List[str] = []
+            if event_types is not None and len(event_types) > 0:
+                event_type_clause, event_type_args = make_in_list_sql_clause(
+                    txn.database_engine, "type", event_types
+                )
+                event_type_clause = f"AND {event_type_clause}"
+
+            # We use `UNION ALL` because we don't need any of the deduplication logic
+            # (`UNION` is really a `UNION` + `DISTINCT`). `UNION ALL` does preserve the
+            # ordering of the operand queries but there is no actual guarantee that it
            # has this behavior in all scenarios so we need the extra `ORDER BY` at the
            # bottom.
            sql = """
@@ -1218,6 +1318,7 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
                    FROM events
                    LEFT JOIN rejections USING (event_id)
                    WHERE room_id = ?
+                        %s
                        AND ? < stream_ordering AND stream_ordering <= ?
                        AND NOT outlier
                        AND rejections.event_id IS NULL
@@ -1229,6 +1330,7 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
                    FROM events
                    LEFT JOIN rejections USING (event_id)
                    WHERE room_id = ?
+                        %s
                        AND stream_ordering <= ?
                        AND NOT outlier
                        AND rejections.event_id IS NULL
@@ -1236,16 +1338,17 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
                    LIMIT 1
                ) AS b
                ORDER BY stream_ordering DESC
-            """
+            """ % (
+                event_type_clause,
+                event_type_clause,
+            )
            txn.execute(
                sql,
-                (
-                    room_id,
-                    min_stream,
-                    max_stream,
-                    room_id,
-                    min_stream,
-                ),
+                [room_id]
+                + event_type_args
+                + [min_stream, max_stream, room_id]
+                + event_type_args
+                + [min_stream],
            )

            for instance_name, stream_ordering, topological_ordering, event_id in txn:
@@ -1257,7 +1360,9 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
                    stream_ordering=stream_ordering,
                ):
                    return event_id, PersistedEventPosition(
-                        instance_name, stream_ordering
+                        # If instance_name is null we default to "master"
+                        instance_name or "master",
+                        stream_ordering,
                    )

            return None
@@ -1267,6 +1372,126 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
            get_last_event_pos_in_room_before_stream_ordering_txn,
        )

+    async def bulk_get_last_event_pos_in_room_before_stream_ordering(
+        self,
+        room_ids: StrCollection,
+        end_token: RoomStreamToken,
+    ) -> Dict[str, int]:
+        """Bulk fetch the stream position of the latest events in the given
+        rooms
+        """
+
+        min_token = end_token.stream
+        max_token = end_token.get_max_stream_pos()
+        results: Dict[str, int] = {}
+
+        # First, we check for the rooms in the stream change cache to see if we
+        # can just use the latest position from it.
+        missing_room_ids: Set[str] = set()
+        for room_id in room_ids:
+            stream_pos = self._events_stream_cache.get_max_pos_of_last_change(room_id)
+            if stream_pos and stream_pos <= min_token:
+                results[room_id] = stream_pos
+            else:
+                missing_room_ids.add(room_id)
+
+        # Next, we query the stream position from the DB. At first we fetch all
+        # positions less than the *max* stream pos in the token, then filter
+        # them down. We do this as a) this is a cheaper query, and b) the vast
+        # majority of rooms will have a latest token from before the min stream
+        # pos.
+
+        def bulk_get_last_event_pos_txn(
+            txn: LoggingTransaction, batch_room_ids: StrCollection
+        ) -> Dict[str, int]:
+            # This query fetches the latest stream position in the rooms before
+            # the given max position.
+            clause, args = make_in_list_sql_clause(
+                self.database_engine, "room_id", batch_room_ids
+            )
+            sql = f"""
+                SELECT room_id, (
+                    SELECT stream_ordering FROM events AS e
+                    LEFT JOIN rejections USING (event_id)
+                    WHERE e.room_id = r.room_id
+                        AND stream_ordering <= ?
+                        AND NOT outlier
+                        AND rejection_reason IS NULL
+                    ORDER BY stream_ordering DESC
+                    LIMIT 1
+                )
+                FROM rooms AS r
+                WHERE {clause}
+            """
+            txn.execute(sql, [max_token] + args)
+            return {row[0]: row[1] for row in txn}
+
+        recheck_rooms: Set[str] = set()
+        for batched in batch_iter(missing_room_ids, 1000):
+            result = await self.db_pool.runInteraction(
+                "bulk_get_last_event_pos_in_room_before_stream_ordering",
+                bulk_get_last_event_pos_txn,
+                batched,
+            )
+
+            # Check that the stream position for the rooms are from before the
+            # minimum position of the token. If not then we need to fetch more
+            # rows.
+            for room_id, stream in result.items():
+                if stream <= min_token:
+                    results[room_id] = stream
+                else:
+                    recheck_rooms.add(room_id)
+
+        if not recheck_rooms:
+            return results
+
+        # For the remaining rooms we need to fetch all rows between the min and
+        # max stream positions in the end token, and filter out the rows that
+        # are after the end token.
+        #
+        # This query should be fast as the range between the min and max should
+        # be small.
+
+        def bulk_get_last_event_pos_recheck_txn(
+            txn: LoggingTransaction, batch_room_ids: StrCollection
+        ) -> Dict[str, int]:
+            clause, args = make_in_list_sql_clause(
+                self.database_engine, "room_id", batch_room_ids
+            )
+            sql = f"""
+                SELECT room_id, instance_name, stream_ordering
+                FROM events
+                WHERE ? < stream_ordering AND stream_ordering <= ?
+                    AND NOT outlier
+                    AND rejection_reason IS NULL
+                    AND {clause}
+                ORDER BY stream_ordering ASC
+            """
+            txn.execute(sql, [min_token, max_token] + args)
+
+            # We take the max stream ordering that is less than the token. Since
+            # we ordered by stream ordering we just need to iterate through and
+            # take the last matching stream ordering.
+            txn_results: Dict[str, int] = {}
+            for row in txn:
+                room_id = row[0]
+                event_pos = PersistedEventPosition(row[1], row[2])
+                if not event_pos.persisted_after(end_token):
+                    txn_results[room_id] = event_pos.stream
+
+            return txn_results
+
+        for batched in batch_iter(recheck_rooms, 1000):
+            recheck_result = await self.db_pool.runInteraction(
+                "bulk_get_last_event_pos_in_room_before_stream_ordering_recheck",
+                bulk_get_last_event_pos_recheck_txn,
+                batched,
+            )
+            results.update(recheck_result)
+
+        return results
+
    async def get_current_room_stream_token_for_room_id(
        self, room_id: str
    ) -> RoomStreamToken:
@@ -1475,7 +1700,7 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
            topological=topological_ordering, stream=stream_ordering
        )

-        rows, start_token = self._paginate_room_events_txn(
+        rows, start_token = self._paginate_room_events_by_topological_ordering_txn(
            txn,
            room_id,
            before_token,
@@ -1485,7 +1710,7 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
        )
        events_before = [r.event_id for r in rows]

-        rows, end_token = self._paginate_room_events_txn(
+        rows, end_token = self._paginate_room_events_by_topological_ordering_txn(
            txn,
            room_id,
            after_token,
@@ -1648,14 +1873,14 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
    def has_room_changed_since(self, room_id: str, stream_id: int) -> bool:
        return self._events_stream_cache.has_entity_changed(room_id, stream_id)

-    def _paginate_room_events_txn(
+    def _paginate_room_events_by_topological_ordering_txn(
        self,
        txn: LoggingTransaction,
        room_id: str,
        from_token: RoomStreamToken,
        to_token: Optional[RoomStreamToken] = None,
        direction: Direction = Direction.BACKWARDS,
-        limit: int = -1,
+        limit: int = 0,
        event_filter: Optional[Filter] = None,
    ) -> Tuple[List[_EventDictReturn], RoomStreamToken]:
        """Returns list of events before or after a given token.
@@ -1677,6 +1902,24 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
            been reached (i.e. there are no events between `from_token` and
            `to_token`), or `limit` is zero.
        """
+        # We can bail early if we're looking forwards, and our `to_key` is already
+        # before our `from_token`.
+        if (
+            direction == Direction.FORWARDS
+            and to_token is not None
+            and to_token.is_before_or_eq(from_token)
+        ):
+            # Token selection matches what we do below if there are no rows
+            return [], to_token if to_token else from_token
+        # Or vice-versa, if we're looking backwards and our `from_token` is already before
+        # our `to_token`.
+        elif (
+            direction == Direction.BACKWARDS
+            and to_token is not None
+            and from_token.is_before_or_eq(to_token)
+        ):
+            # Token selection matches what we do below if there are no rows
+            return [], to_token if to_token else from_token

        args: List[Any] = [room_id]

@@ -1761,7 +2004,6 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
            "bounds": bounds,
            "order": order,
        }
-
        txn.execute(sql, args)

        # Filter the result set.
@@ -1793,27 +2035,30 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
        return rows, next_token

    @trace
-    async def paginate_room_events(
+    @tag_args
+    async def paginate_room_events_by_topological_ordering(
        self,
+        *,
        room_id: str,
        from_key: RoomStreamToken,
        to_key: Optional[RoomStreamToken] = None,
        direction: Direction = Direction.BACKWARDS,
-        limit: int = -1,
+        limit: int = 0,
        event_filter: Optional[Filter] = None,
    ) -> Tuple[List[EventBase], RoomStreamToken]:
-        """Returns list of events before or after a given token.
-
-        When Direction.FORWARDS: from_key < x <= to_key
-        When Direction.BACKWARDS: from_key >= x > to_key
+        """
+        Paginate events by `topological_ordering` (tie-break with `stream_ordering`) in
+        the room from the `from_key` in the given `direction` to the `to_key` or
+        `limit`.

        Args:
            room_id
-            from_key: The token used to stream from
-            to_key: A token which if given limits the results to only those before
+            from_key: The token to stream from (starting point and heading in the given
+                direction)
+            to_key: The token representing the end stream position (end point)
            direction: Indicates whether we are paginating forwards or backwards
                from `from_key`.
-            limit: The maximum number of events to return.
+            limit: Maximum number of events to return
            event_filter: If provided filters the events to those that match the filter.

        Returns:
@@ -1821,8 +2066,18 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
            of the result set. If no events are returned then the end of the
            stream has been reached (i.e. there are no events between `from_key`
            and `to_key`).
+
+            When Direction.FORWARDS: from_key < x <= to_key, (ascending order)
+            When Direction.BACKWARDS: from_key >= x > to_key, (descending order)
        """

+        # FIXME: When going forwards, we should enforce that the `to_key` is not `None`
+        # because we always need an upper bound when querying the events stream (as
+        # otherwise we'll potentially pick up events that are not fully persisted).
+
+        # We have these checks outside of the transaction function (txn) to save getting
+        # a DB connection and switching threads if we don't need to.
+        #
        # We can bail early if we're looking forwards, and our `to_key` is already
        # before our `from_key`.
        if (
@@ -1845,8 +2100,8 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
            return [], to_key if to_key else from_key

        rows, token = await self.db_pool.runInteraction(
-            "paginate_room_events",
-            self._paginate_room_events_txn,
+            "paginate_room_events_by_topological_ordering",
+            self._paginate_room_events_by_topological_ordering_txn,
            room_id,
            from_key,
            to_key,
@@ -1957,3 +2212,14 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
            return RoomStreamToken(stream=last_position.stream - 1)

        return None
+
+    @trace
+    def get_rooms_that_might_have_updates(
+        self, room_ids: StrCollection, from_token: RoomStreamToken
+    ) -> StrCollection:
+        """Filters given room IDs down to those that might have updates, i.e.
+        removes rooms that definitely do not have updates.
+        """
+        return self._events_stream_cache.get_entities_changed(
+            room_ids, from_token.stream
+        )
@@ -19,7 +19,7 @@
 #
 #

-SCHEMA_VERSION = 85  # remember to update the list below when updating
+SCHEMA_VERSION = 86  # remember to update the list below when updating
 """Represents the expectations made by the codebase about the database schema

 This should be incremented whenever the codebase changes its requirements on the
@@ -139,6 +139,9 @@ Changes in SCHEMA_VERSION = 84

 Changes in SCHEMA_VERSION = 85
    - Add a column `suspended` to the `users` table
+
+Changes in SCHEMA_VERSION = 86
+    - Add a column `authenticated` to the tables `local_media_repository` and `remote_media_cache`
 """


@@ -0,0 +1,15 @@
+--
+-- This file is licensed under the Affero General Public License (AGPL) version 3.
+--
+-- Copyright (C) 2024 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>.
+
+ALTER TABLE remote_media_cache ADD COLUMN authenticated BOOLEAN DEFAULT FALSE NOT NULL;
+ALTER TABLE local_media_repository ADD COLUMN authenticated BOOLEAN DEFAULT FALSE NOT NULL;
@@ -20,6 +20,7 @@
 #
 #
 import abc
+import logging
 import re
 import string
 from enum import Enum
@@ -74,6 +75,9 @@ if TYPE_CHECKING:
    from synapse.storage.databases.main import DataStore, PurgeEventsStore
    from synapse.storage.databases.main.appservice import ApplicationServiceWorkerStore

+
+logger = logging.getLogger(__name__)
+
 # Define a state map type from type/state_key to T (usually an event ID or
 # event)
 T = TypeVar("T")
@@ -454,6 +458,8 @@ class AbstractMultiWriterStreamToken(metaclass=abc.ABCMeta):
    represented by a default `stream` attribute and a map of instance name to
    stream position of any writers that are ahead of the default stream
    position.
+
+    The values in `instance_map` must be greater than the `stream` attribute.
    """

    stream: int = attr.ib(validator=attr.validators.instance_of(int), kw_only=True)
@@ -468,6 +474,15 @@ class AbstractMultiWriterStreamToken(metaclass=abc.ABCMeta):
        kw_only=True,
    )

+    def __attrs_post_init__(self) -> None:
+        # Enforce that all instances have a value greater than the min stream
+        # position.
+        for i, v in self.instance_map.items():
+            if v <= self.stream:
+                raise ValueError(
+                    f"'instance_map' includes a stream position before the main 'stream' attribute. Instance: {i}"
+                )
+
    @classmethod
    @abc.abstractmethod
    async def parse(cls, store: "DataStore", string: str) -> "Self":
@@ -494,6 +509,9 @@ class AbstractMultiWriterStreamToken(metaclass=abc.ABCMeta):
            for instance in set(self.instance_map).union(other.instance_map)
        }

+        # Filter out any redundant entries.
+        instance_map = {i: s for i, s in instance_map.items() if s > max_stream}
+
        return attr.evolve(
            self, stream=max_stream, instance_map=immutabledict(instance_map)
        )
@@ -539,10 +557,15 @@ class AbstractMultiWriterStreamToken(metaclass=abc.ABCMeta):
    def bound_stream_token(self, max_stream: int) -> "Self":
        """Bound the stream positions to a maximum value"""

+        min_pos = min(self.stream, max_stream)
        return type(self)(
-            stream=min(self.stream, max_stream),
+            stream=min_pos,
            instance_map=immutabledict(
-                {k: min(s, max_stream) for k, s in self.instance_map.items()}
+                {
+                    k: min(s, max_stream)
+                    for k, s in self.instance_map.items()
+                    if min(s, max_stream) > min_pos
+                }
            ),
        )

@@ -637,6 +660,8 @@ class RoomStreamToken(AbstractMultiWriterStreamToken):
                "Cannot set both 'topological' and 'instance_map' on 'RoomStreamToken'."
            )

+        super().__attrs_post_init__()
+
    @classmethod
    async def parse(cls, store: "PurgeEventsStore", string: str) -> "RoomStreamToken":
        try:
@@ -651,6 +676,11 @@ class RoomStreamToken(AbstractMultiWriterStreamToken):

                instance_map = {}
                for part in parts[1:]:
+                    if not part:
+                        # Handle tokens of the form `m5~`, which were created by
+                        # a bug
+                        continue
+
                    key, value = part.split(".")
                    instance_id = int(key)
                    pos = int(value)
@@ -666,7 +696,10 @@ class RoomStreamToken(AbstractMultiWriterStreamToken):
        except CancelledError:
            raise
        except Exception:
-            pass
+            # We log an exception here as even though this *might* be a client
+            # handing a bad token, its more likely that Synapse returned a bad
+            # token (and we really want to catch those!).
+            logger.exception("Failed to parse stream token: %r", string)
        raise SynapseError(400, "Invalid room stream token %r" % (string,))

    @classmethod
@@ -713,6 +746,8 @@ class RoomStreamToken(AbstractMultiWriterStreamToken):
        return self.instance_map.get(instance_name, self.stream)

    async def to_string(self, store: "DataStore") -> str:
+        """See class level docstring for information about the format."""
+
        if self.topological is not None:
            return "t%d-%d" % (self.topological, self.stream)
        elif self.instance_map:
@@ -727,8 +762,10 @@ class RoomStreamToken(AbstractMultiWriterStreamToken):
                instance_id = await store.get_id_for_instance(name)
                entries.append(f"{instance_id}.{pos}")

-            encoded_map = "~".join(entries)
-            return f"m{self.stream}~{encoded_map}"
+            if entries:
+                encoded_map = "~".join(entries)
+                return f"m{self.stream}~{encoded_map}"
+            return f"s{self.stream}"
        else:
            return "s%d" % (self.stream,)

@@ -740,6 +777,13 @@ class RoomStreamToken(AbstractMultiWriterStreamToken):

        return super().bound_stream_token(max_stream)

+    def __str__(self) -> str:
+        instances = ", ".join(f"{k}: {v}" for k, v in sorted(self.instance_map.items()))
+        return (
+            f"RoomStreamToken(stream: {self.stream}, topological: {self.topological}, "
+            f"instances: {{{instances}}})"
+        )
+

@attr.s(frozen=True, slots=True, order=False)
 class MultiWriterStreamToken(AbstractMultiWriterStreamToken):
@@ -756,6 +800,11 @@ class MultiWriterStreamToken(AbstractMultiWriterStreamToken):

                instance_map = {}
                for part in parts[1:]:
+                    if not part:
+                        # Handle tokens of the form `m5~`, which were created by
+                        # a bug
+                        continue
+
                    key, value = part.split(".")
                    instance_id = int(key)
                    pos = int(value)
@@ -770,10 +819,15 @@ class MultiWriterStreamToken(AbstractMultiWriterStreamToken):
        except CancelledError:
            raise
        except Exception:
-            pass
+            # We log an exception here as even though this *might* be a client
+            # handing a bad token, its more likely that Synapse returned a bad
+            # token (and we really want to catch those!).
+            logger.exception("Failed to parse stream token: %r", string)
        raise SynapseError(400, "Invalid stream token %r" % (string,))

    async def to_string(self, store: "DataStore") -> str:
+        """See class level docstring for information about the format."""
+
        if self.instance_map:
            entries = []
            for name, pos in self.instance_map.items():
@@ -786,8 +840,10 @@ class MultiWriterStreamToken(AbstractMultiWriterStreamToken):
                instance_id = await store.get_id_for_instance(name)
                entries.append(f"{instance_id}.{pos}")

-            encoded_map = "~".join(entries)
-            return f"m{self.stream}~{encoded_map}"
+            if entries:
+                encoded_map = "~".join(entries)
+                return f"m{self.stream}~{encoded_map}"
+            return str(self.stream)
        else:
            return str(self.stream)

@@ -824,6 +880,13 @@ class MultiWriterStreamToken(AbstractMultiWriterStreamToken):

        return True

+    def __str__(self) -> str:
+        instances = ", ".join(f"{k}: {v}" for k, v in sorted(self.instance_map.items()))
+        return (
+            f"MultiWriterStreamToken(stream: {self.stream}, "
+            f"instances: {{{instances}}})"
+        )
+

 class StreamKeyType(Enum):
    """Known stream types.
@@ -1082,12 +1145,64 @@ class StreamToken:

        return True

+    def __str__(self) -> str:
+        return (
+            f"StreamToken(room: {self.room_key}, presence: {self.presence_key}, "
+            f"typing: {self.typing_key}, receipt: {self.receipt_key}, "
+            f"account_data: {self.account_data_key}, push_rules: {self.push_rules_key}, "
+            f"to_device: {self.to_device_key}, device_list: {self.device_list_key}, "
+            f"groups: {self.groups_key}, un_partial_stated_rooms: {self.un_partial_stated_rooms_key})"
+        )
+

 StreamToken.START = StreamToken(
    RoomStreamToken(stream=0), 0, 0, MultiWriterStreamToken(stream=0), 0, 0, 0, 0, 0, 0
 )


+@attr.s(slots=True, frozen=True, auto_attribs=True)
+class SlidingSyncStreamToken:
+    """The same as a `StreamToken`, but includes an extra field at the start for
+    the sliding sync connection token (separated by a '/'). This is used to
+    store per-connection state.
+
+    This then looks something like:
+        5/s2633508_17_338_6732159_1082514_541479_274711_265584_1_379
+
+    Attributes:
+        stream_token: Token representing the position of all the standard
+            streams.
+        connection_position: Token used by sliding sync to track updates to any
+            per-connection state stored by Synapse.
+    """
+
+    stream_token: StreamToken
+    connection_position: int
+
+    @staticmethod
+    @cancellable
+    async def from_string(store: "DataStore", string: str) -> "SlidingSyncStreamToken":
+        """Creates a SlidingSyncStreamToken from its textual representation."""
+        try:
+            connection_position_str, stream_token_str = string.split("/", 1)
+            connection_position = int(connection_position_str)
+            stream_token = await StreamToken.from_string(store, stream_token_str)
+
+            return SlidingSyncStreamToken(
+                stream_token=stream_token,
+                connection_position=connection_position,
+            )
+        except CancelledError:
+            raise
+        except Exception:
+            raise SynapseError(400, "Invalid stream token")
+
+    async def to_string(self, store: "DataStore") -> str:
+        """Serializes the token to a string"""
+        stream_token_str = await self.stream_token.to_string(store)
+        return f"{self.connection_position}/{stream_token_str}"
+
+
@attr.s(slots=True, frozen=True, auto_attribs=True)
 class PersistedPosition:
    """Position of a newly persisted row with instance that persisted it."""
@@ -1170,11 +1285,12 @@ class ReadReceipt:
@attr.s(slots=True, frozen=True, auto_attribs=True)
 class DeviceListUpdates:
    """
-    An object containing a diff of information regarding other users' device lists, intended for
-    a recipient to carry out device list tracking.
+    An object containing a diff of information regarding other users' device lists,
+    intended for a recipient to carry out device list tracking.

    Attributes:
-        changed: A set of users whose device lists have changed recently.
+        changed: A set of users who have updated their device identity or
+            cross-signing keys, or who now share an encrypted room with.
        left: A set of users who the recipient no longer needs to track the device lists of.
            Typically when those users no longer share any end-to-end encryption enabled rooms.
    """
@@ -18,7 +18,7 @@
 #
 #
 from enum import Enum
-from typing import TYPE_CHECKING, Dict, Final, List, Optional, Tuple
+from typing import TYPE_CHECKING, Dict, Final, List, Mapping, Optional, Sequence, Tuple

 import attr
 from typing_extensions import TypedDict
@@ -31,7 +31,15 @@ else:
    from pydantic import Extra

 from synapse.events import EventBase
-from synapse.types import JsonDict, JsonMapping, StreamToken, UserID
+from synapse.types import (
+    DeviceListUpdates,
+    JsonDict,
+    JsonMapping,
+    Requester,
+    SlidingSyncStreamToken,
+    StreamToken,
+    UserID,
+)
 from synapse.types.rest.client import SlidingSyncBody

 if TYPE_CHECKING:
@@ -102,7 +110,7 @@ class SlidingSyncConfig(SlidingSyncBody):
    """

    user: UserID
-    device_id: Optional[str]
+    requester: Requester

    # Pydantic config
    class Config:
@@ -144,7 +152,7 @@ class SlidingSyncResult:
    Attributes:
        next_pos: The next position token in the sliding window to request (next_batch).
        lists: Sliding window API. A map of list key to list results.
-        rooms: Room subscription API. A map of room ID to room subscription to room results.
+        rooms: Room subscription API. A map of room ID to room results.
        extensions: Extensions API. A map of extension key to extension results.
    """

@@ -156,6 +164,8 @@ class SlidingSyncResult:
            avatar: Room avatar
            heroes: List of stripped membership events (containing `user_id` and optionally
                `avatar_url` and `displayname`) for the users used to calculate the room name.
+            is_dm: Flag to specify whether the room is a direct-message room (most likely
+                between two people).
            initial: Flag which is set when this is the first time the server is sending this
                data on this connection. Clients can use this flag to replace or update
                their local state. When there is an update, servers MUST omit this flag
@@ -167,15 +177,27 @@ class SlidingSyncResult:
                the timeline events above. This allows clients to show accurate reaction
                counts (or edits, threads), even if some of the reaction events were skipped
                over in a gappy sync.
-            is_dm: Flag to specify whether the room is a direct-message room (most likely
-                between two people).
            stripped_state: Stripped state events (for rooms where the usre is
                invited/knocked). Same as `rooms.invite.$room_id.invite_state` in sync v2,
                absent on joined/left rooms
            prev_batch: A token that can be passed as a start parameter to the
                `/rooms/<room_id>/messages` API to retrieve earlier messages.
-            limited: True if their are more events than fit between the given position and now.
-                Sync again to get more.
+            limited: True if there are more events than `timeline_limit` looking
+                backwards from the `response.pos` to the `request.pos`.
+            num_live: The number of timeline events which have just occurred and are not historical.
+                The last N events are 'live' and should be treated as such. This is mostly
+                useful to determine whether a given @mention event should make a noise or not.
+                Clients cannot rely solely on the absence of `initial: true` to determine live
+                events because if a room not in the sliding window bumps into the window because
+                of an @mention it will have `initial: true` yet contain a single live event
+                (with potentially other old events in the timeline).
+            bump_stamp: The `stream_ordering` of the last event according to the
+                `bump_event_types`. This helps clients sort more readily without them
+                needing to pull in a bunch of the timeline to determine the last activity.
+                `bump_event_types` is a thing because for example, we don't want display
+                name changes to mark the room as unread and bump it to the top. For
+                encrypted rooms, we just have to consider any activity as a bump because we
+                can't see the content and the client has to figure it out for themselves.
            joined_count: The number of users with membership of join, including the client's
                own user ID. (same as sync `v2 m.joined_member_count`)
            invited_count: The number of users with membership of invite. (same as sync v2
@@ -184,37 +206,48 @@ class SlidingSyncResult:
                as sync v2)
            highlight_count: The number of unread notifications for this room with the highlight
                flag set. (same as sync v2)
-            num_live: The number of timeline events which have just occurred and are not historical.
-                The last N events are 'live' and should be treated as such. This is mostly
-                useful to determine whether a given @mention event should make a noise or not.
-                Clients cannot rely solely on the absence of `initial: true` to determine live
-                events because if a room not in the sliding window bumps into the window because
-                of an @mention it will have `initial: true` yet contain a single live event
-                (with potentially other old events in the timeline).
        """

+        @attr.s(slots=True, frozen=True, auto_attribs=True)
+        class StrippedHero:
+            user_id: str
+            display_name: Optional[str]
+            avatar_url: Optional[str]
+
        name: Optional[str]
        avatar: Optional[str]
-        heroes: Optional[List[EventBase]]
-        initial: bool
-        # Only optional because it won't be included for invite/knock rooms with `stripped_state`
-        required_state: Optional[List[EventBase]]
-        # Only optional because it won't be included for invite/knock rooms with `stripped_state`
-        timeline_events: Optional[List[EventBase]]
-        bundled_aggregations: Optional[Dict[str, "BundledAggregations"]]
+        heroes: Optional[List[StrippedHero]]
        is_dm: bool
+        initial: bool
+        # Should be empty for invite/knock rooms with `stripped_state`
+        required_state: List[EventBase]
+        # Should be empty for invite/knock rooms with `stripped_state`
+        timeline_events: List[EventBase]
+        bundled_aggregations: Optional[Dict[str, "BundledAggregations"]]
        # Optional because it's only relevant to invite/knock rooms
-        stripped_state: Optional[List[JsonDict]]
+        stripped_state: List[JsonDict]
        # Only optional because it won't be included for invite/knock rooms with `stripped_state`
        prev_batch: Optional[StreamToken]
        # Only optional because it won't be included for invite/knock rooms with `stripped_state`
        limited: Optional[bool]
+        # Only optional because it won't be included for invite/knock rooms with `stripped_state`
+        num_live: Optional[int]
+        bump_stamp: int
        joined_count: int
        invited_count: int
        notification_count: int
        highlight_count: int
-        # Only optional because it won't be included for invite/knock rooms with `stripped_state`
-        num_live: Optional[int]
+
+        def __bool__(self) -> bool:
+            return (
+                # If this is the first time the client is seeing the room, we should not filter it out
+                # under any circumstance.
+                self.initial
+                # We need to let the client know if there are any new events
+                or bool(self.required_state)
+                or bool(self.timeline_events)
+                or bool(self.stripped_state)
+            )

    @attr.s(slots=True, frozen=True, auto_attribs=True)
    class SlidingWindowList:
@@ -244,24 +277,155 @@ class SlidingSyncResult:
        count: int
        ops: List[Operation]

-    next_pos: StreamToken
+    @attr.s(slots=True, frozen=True, auto_attribs=True)
+    class Extensions:
+        """Responses for extensions
+
+        Attributes:
+            to_device: The to-device extension (MSC3885)
+            e2ee: The E2EE device extension (MSC3884)
+        """
+
+        @attr.s(slots=True, frozen=True, auto_attribs=True)
+        class ToDeviceExtension:
+            """The to-device extension (MSC3885)
+
+            Attributes:
+                next_batch: The to-device stream token the client should use
+                    to get more results
+                events: A list of to-device messages for the client
+            """
+
+            next_batch: str
+            events: Sequence[JsonMapping]
+
+            def __bool__(self) -> bool:
+                return bool(self.events)
+
+        @attr.s(slots=True, frozen=True, auto_attribs=True)
+        class E2eeExtension:
+            """The E2EE device extension (MSC3884)
+
+            Attributes:
+                device_list_updates: List of user_ids whose devices have changed or left (only
+                    present on incremental syncs).
+                device_one_time_keys_count: Map from key algorithm to the number of
+                    unclaimed one-time keys currently held on the server for this device. If
+                    an algorithm is unlisted, the count for that algorithm is assumed to be
+                    zero. If this entire parameter is missing, the count for all algorithms
+                    is assumed to be zero.
+                device_unused_fallback_key_types: List of unused fallback key algorithms
+                    for this device.
+            """
+
+            # Only present on incremental syncs
+            device_list_updates: Optional[DeviceListUpdates]
+            device_one_time_keys_count: Mapping[str, int]
+            device_unused_fallback_key_types: Sequence[str]
+
+            def __bool__(self) -> bool:
+                # Note that "signed_curve25519" is always returned in key count responses
+                # regardless of whether we uploaded any keys for it. This is necessary until
+                # https://github.com/matrix-org/matrix-doc/issues/3298 is fixed.
+                #
+                # Also related:
+                # https://github.com/element-hq/element-android/issues/3725 and
+                # https://github.com/matrix-org/synapse/issues/10456
+                default_otk = self.device_one_time_keys_count.get("signed_curve25519")
+                more_than_default_otk = len(self.device_one_time_keys_count) > 1 or (
+                    default_otk is not None and default_otk > 0
+                )
+
+                return bool(
+                    more_than_default_otk
+                    or self.device_list_updates
+                    or self.device_unused_fallback_key_types
+                )
+
+        @attr.s(slots=True, frozen=True, auto_attribs=True)
+        class AccountDataExtension:
+            """The Account Data extension (MSC3959)
+
+            Attributes:
+                global_account_data_map: Mapping from `type` to `content` of global account
+                    data events.
+                account_data_by_room_map: Mapping from room_id to mapping of `type` to
+                    `content` of room account data events.
+            """
+
+            global_account_data_map: Mapping[str, JsonMapping]
+            account_data_by_room_map: Mapping[str, Mapping[str, JsonMapping]]
+
+            def __bool__(self) -> bool:
+                return bool(
+                    self.global_account_data_map or self.account_data_by_room_map
+                )
+
+        @attr.s(slots=True, frozen=True, auto_attribs=True)
+        class ReceiptsExtension:
+            """The Receipts extension (MSC3960)
+
+            Attributes:
+                room_id_to_receipt_map: Mapping from room_id to `m.receipt` ephemeral
+                    event (type, content)
+            """
+
+            room_id_to_receipt_map: Mapping[str, JsonMapping]
+
+            def __bool__(self) -> bool:
+                return bool(self.room_id_to_receipt_map)
+
+        @attr.s(slots=True, frozen=True, auto_attribs=True)
+        class TypingExtension:
+            """The Typing Notification extension (MSC3961)
+
+            Attributes:
+                room_id_to_typing_map: Mapping from room_id to `m.typing` ephemeral
+                    event (type, content)
+            """
+
+            room_id_to_typing_map: Mapping[str, JsonMapping]
+
+            def __bool__(self) -> bool:
+                return bool(self.room_id_to_typing_map)
+
+        to_device: Optional[ToDeviceExtension] = None
+        e2ee: Optional[E2eeExtension] = None
+        account_data: Optional[AccountDataExtension] = None
+        receipts: Optional[ReceiptsExtension] = None
+        typing: Optional[TypingExtension] = None
+
+        def __bool__(self) -> bool:
+            return bool(
+                self.to_device
+                or self.e2ee
+                or self.account_data
+                or self.receipts
+                or self.typing
+            )
+
+    next_pos: SlidingSyncStreamToken
    lists: Dict[str, SlidingWindowList]
    rooms: Dict[str, RoomResult]
-    extensions: JsonMapping
+    extensions: Extensions

    def __bool__(self) -> bool:
        """Make the result appear empty if there are no updates. This is used
        to tell if the notifier needs to wait for more events when polling for
        events.
        """
-        return bool(self.lists or self.rooms or self.extensions)
+        # We don't include `self.lists` here, as a) `lists` is always non-empty even if
+        # there are no changes, and b) since we're sorting rooms by `stream_ordering` of
+        # the latest activity, anything that would cause the order to change would end
+        # up in `self.rooms` and cause us to send down the change.
+        return bool(self.rooms or self.extensions)

    @staticmethod
-    def empty(next_pos: StreamToken) -> "SlidingSyncResult":
+    def empty(next_pos: SlidingSyncStreamToken) -> "SlidingSyncResult":
        "Return a new empty result"
        return SlidingSyncResult(
            next_pos=next_pos,
            lists={},
            rooms={},
-            extensions={},
+            extensions=SlidingSyncResult.Extensions(),
        )
--- a/Show More
+++ b/Show More
				`@@ -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.`
				`@@ -0,0 +1 @@`
				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.
				`@@ -0,0 +1 @@`
				`Fixup comment in sliding sync implementation.`
				`@@ -0,0 +1 @@`
				`Fix experimental sliding sync implementation to remember any updates in rooms that were not sent down immediately.`
				`@@ -0,0 +1 @@`
				`Return correct per-room notification and highlight counts in experimental sliding sync implementation.`