- Experimental support for the thread relation defined in [MSC3440](https://github.com/matrix-org/matrix-doc/pull/3440). ([\#11161](https://github.com/matrix-org/synapse/issues/11161))
- Add a new version of delete room admin API `DELETE /_synapse/admin/v2/rooms/<room_id>` to run it in background. Contributed by @dklimpel. ([\#11223](https://github.com/matrix-org/synapse/issues/11223))
- Allow the admin [Delete Room API](https://matrix-org.github.io/synapse/latest/admin_api/rooms.html#delete-room-api) to block a room without the need to join it. ([\#11228](https://github.com/matrix-org/synapse/issues/11228))
- Support filtering by relation senders & types per [MSC3440](https://github.com/matrix-org/matrix-doc/pull/3440). ([\#11236](https://github.com/matrix-org/synapse/issues/11236))
- Add support for the `/_matrix/client/v3` APIs from Matrix v1.1. ([\#11318](https://github.com/matrix-org/synapse/issues/11318))
- Add dedicated admin API for blocking a room. ([\#11324](https://github.com/matrix-org/synapse/issues/11324))
- Support the stable version of [MSC2778](https://github.com/matrix-org/matrix-doc/pull/2778): the `m.login.application_service` login type. Contributed by @tulir. ([\#11335](https://github.com/matrix-org/synapse/issues/11335))
- Add admin API to un-shadow-ban a user. ([\#11347](https://github.com/matrix-org/synapse/issues/11347))
- Add admin API to run background jobs. ([\#11352](https://github.com/matrix-org/synapse/issues/11352))
- Update the JWT login type to support custom a `sub` claim. ([\#11361](https://github.com/matrix-org/synapse/issues/11361))
- Add support for the `/_matrix/media/v3` APIs from Matrix v1.1. ([\#11371](https://github.com/matrix-org/synapse/issues/11371))
- Store and allow querying of arbitrary event relations. ([\#11391](https://github.com/matrix-org/synapse/issues/11391))
Bugfixes
--------
- Fix a long-standing bug wherein display names or avatar URLs containing null bytes cause an internal server error
when stored in the DB. ([\#11230](https://github.com/matrix-org/synapse/issues/11230))
- Prevent [MSC2716](https://github.com/matrix-org/matrix-doc/pull/2716) historical state events from being pushed to an application service via `/transactions`. ([\#11265](https://github.com/matrix-org/synapse/issues/11265))
- Fix a long-standing bug where uploading extremely thin images (e.g. 1000x1) would fail. Contributed by @Neeeflix. ([\#11288](https://github.com/matrix-org/synapse/issues/11288))
- Fix a bug, introduced in Synapse 1.46.0, which caused the `check_3pid_auth` and `on_logged_out` callbacks in legacy password authentication provider modules to not be registered. Modules using the generic module API were not affected. ([\#11340](https://github.com/matrix-org/synapse/issues/11340))
- Fix a bug introduced in 1.41.0 where space hierarchy responses would be incorrectly reused if multiple users were to make the same request at the same time. ([\#11355](https://github.com/matrix-org/synapse/issues/11355))
- Fix a bug introduced in v1.45.0 where the `read_templates` method of the module API would error. ([\#11377](https://github.com/matrix-org/synapse/issues/11377))
- Fix an issue introduced in v1.47.0 which prevented servers re-joining rooms they had previously left, if their signing keys were replaced. ([\#11379](https://github.com/matrix-org/synapse/issues/11379))
- Fix a bug introduced in v1.13.0 where creating and publishing a room could cause errors if `room_list_publication_rules` is configured. ([\#11392](https://github.com/matrix-org/synapse/issues/11392))
- Improve performance of various background database schema updates. ([\#11421](https://github.com/matrix-org/synapse/issues/11421), [\#11422](https://github.com/matrix-org/synapse/issues/11422))
Improved Documentation
----------------------
- Suggest users of the Debian packages add configuration to `/etc/matrix-synapse/conf.d/` to prevent, upon upgrade, being asked to choose between their configuration and the maintainer's. ([\#11281](https://github.com/matrix-org/synapse/issues/11281))
- Fix typo in the word `available` and fix HTTP method (should be `GET`) for the `username_available` admin API. Contributed by Stanislav Motylkov. ([\#11286](https://github.com/matrix-org/synapse/issues/11286))
- Add Single Sign-On, SAML and CAS pages to the documentation. ([\#11298](https://github.com/matrix-org/synapse/issues/11298))
- Changed the word 'Home server' as one word 'homeserver' in documentation. ([\#11320](https://github.com/matrix-org/synapse/issues/11320))
- Fix missing quotes for wildcard domains in `federation_certificate_verification_whitelist`. ([\#11381](https://github.com/matrix-org/synapse/issues/11381))
- Add type annotations to `synapse.metrics`. ([\#10847](https://github.com/matrix-org/synapse/issues/10847))
- Split out federated PDU retrieval function into a non-cached version. ([\#11242](https://github.com/matrix-org/synapse/issues/11242))
- Clean up code relating to to-device messages and sending ephemeral events to application services. ([\#11247](https://github.com/matrix-org/synapse/issues/11247))
- Fix a small typo in the error response when a relation type other than 'm.annotation' is passed to `GET /rooms/{room_id}/aggregations/{event_id}`. ([\#11278](https://github.com/matrix-org/synapse/issues/11278))
- Drop unused db tables `room_stats_historical` and `user_stats_historical`. ([\#11280](https://github.com/matrix-org/synapse/issues/11280))
- Require all files in synapse/ and tests/ to pass mypy unless specifically excluded. ([\#11282](https://github.com/matrix-org/synapse/issues/11282), [\#11285](https://github.com/matrix-org/synapse/issues/11285), [\#11359](https://github.com/matrix-org/synapse/issues/11359))
- Add missing type hints to `synapse.app`. ([\#11287](https://github.com/matrix-org/synapse/issues/11287))
- Remove unused parameters on `FederationEventHandler._check_event_auth`. ([\#11292](https://github.com/matrix-org/synapse/issues/11292))
- Add type hints to `synapse._scripts`. ([\#11297](https://github.com/matrix-org/synapse/issues/11297))
- Fix an issue which prevented the 'remove deleted devices from device_inbox column' background process from running when updating from a recent Synapse version. ([\#11303](https://github.com/matrix-org/synapse/issues/11303))
- Add type hints to storage classes. ([\#11307](https://github.com/matrix-org/synapse/issues/11307), [\#11310](https://github.com/matrix-org/synapse/issues/11310), [\#11311](https://github.com/matrix-org/synapse/issues/11311), [\#11312](https://github.com/matrix-org/synapse/issues/11312), [\#11313](https://github.com/matrix-org/synapse/issues/11313), [\#11314](https://github.com/matrix-org/synapse/issues/11314), [\#11316](https://github.com/matrix-org/synapse/issues/11316), [\#11322](https://github.com/matrix-org/synapse/issues/11322), [\#11332](https://github.com/matrix-org/synapse/issues/11332), [\#11339](https://github.com/matrix-org/synapse/issues/11339), [\#11342](https://github.com/matrix-org/synapse/issues/11342))
- Add type hints to `synapse.util`. ([\#11321](https://github.com/matrix-org/synapse/issues/11321), [\#11328](https://github.com/matrix-org/synapse/issues/11328))
- Improve type annotations in Synapse's test suite. ([\#11323](https://github.com/matrix-org/synapse/issues/11323), [\#11330](https://github.com/matrix-org/synapse/issues/11330))
- Test that room alias deletion works as intended. ([\#11327](https://github.com/matrix-org/synapse/issues/11327))
- Add type annotations for some methods and properties in the module API. ([\#11341](https://github.com/matrix-org/synapse/issues/11341))
- Fix running `scripts-dev/complement.sh`, which was broken in v1.47.0rc1. ([\#11368](https://github.com/matrix-org/synapse/issues/11368))
- Rename `get_access_token_for_user_id` to `create_access_token_for_user_id` to better reflect what it does. ([\#11369](https://github.com/matrix-org/synapse/issues/11369))
- Rename `get_refresh_token_for_user_id` to `create_refresh_token_for_user_id` to better describe what it does. ([\#11370](https://github.com/matrix-org/synapse/issues/11370))
- Add type hints to configuration classes. ([\#11377](https://github.com/matrix-org/synapse/issues/11377))
- Publish a `develop` image to dockerhub. ([\#11380](https://github.com/matrix-org/synapse/issues/11380))
- Keep fallback key marked as used if it's re-uploaded. ([\#11382](https://github.com/matrix-org/synapse/issues/11382))
- Use `auto_attribs` on the `attrs` class `RefreshTokenLookupResult`. ([\#11386](https://github.com/matrix-org/synapse/issues/11386))
- Rename unstable `access_token_lifetime` configuration option to `refreshable_access_token_lifetime` to make it clear it only concerns refreshable access tokens. ([\#11388](https://github.com/matrix-org/synapse/issues/11388))
- Do not run the broken MSC2716 tests when running `scripts-dev/complement.sh`. ([\#11389](https://github.com/matrix-org/synapse/issues/11389))
- Remove dead code from supporting ACME. ([\#11393](https://github.com/matrix-org/synapse/issues/11393))
- Refactor including the bundled relations when serializing an event. ([\#11408](https://github.com/matrix-org/synapse/issues/11408))
Allowtheadmin[DeleteRoomAPI](https://matrix-org.github.io/synapse/latest/admin_api/rooms.html#delete-room-api) to block a room without the need to join it.
Prevent [MSC2716](https://github.com/matrix-org/matrix-doc/pull/2716) historical state events from being pushed to an application service via `/transactions`.
Suggest users of the Debian packages add configuration to `/etc/matrix-synapse/conf.d/` to prevent, upon upgrade, being asked to choose between their configuration and the maintainer's.
Fix an issue which prevented the 'remove deleted devices from device_inbox column' background process from running when updating from a recent Synapse version.
Fix a bug, introduced in Synapse 1.46.0, which caused the `check_3pid_auth` and `on_logged_out` callbacks in legacy password authentication provider modules to not be registered. Modules using the generic module API were not affected.
Fix a bug introduced in 1.41.0 where space hierarchy responses would be incorrectly reused if multiple users were to make the same request at the same time.
Rename unstable `access_token_lifetime` configuration option to `refreshable_access_token_lifetime` to make it clear it only concerns refreshable access tokens.