### Client-Server API
New Endpoints
- [`POST /_matrix/media/v1/create`](/client-server-api/#post_matrixmediav1create) ([#1499](https://github.com/matrix-org/matrix-spec/issues/1499))
- [`PUT /_matrix/media/v3/upload/{serverName}/{mediaId}`](/client-server-api/#put_matrixmediav3uploadservernamemediaid) ([#1499](https://github.com/matrix-org/matrix-spec/issues/1499))
- [`POST /_matrix/client/v1/login/get_token`](/client-server-api/#post_matrixclientv1loginget_token) ([#1530](https://github.com/matrix-org/matrix-spec/issues/1530))
Backwards Compatible Changes
- Changes to the server-side aggregation of `m.replace` (edit) events, as per [MSC3925](https://github.com/matrix-org/matrix-spec-proposals/pull/3925). ([#1440](https://github.com/matrix-org/matrix-spec/issues/1440), [#1525](https://github.com/matrix-org/matrix-spec/issues/1525))
- Add new push rule conditions `event_property_is` and `event_property_contains`, as per [MSC3758](https://github.com/matrix-org/matrix-spec-proposals/pull/3758) and [MSC3966](https://github.com/matrix-org/matrix-spec-proposals/pull/3966). ([#1464](https://github.com/matrix-org/matrix-spec/issues/1464))
- Add `m.annotation` relations (reactions), as per [MSC2677](https://github.com/matrix-org/matrix-spec-proposals/pull/2677). ([#1475](https://github.com/matrix-org/matrix-spec/issues/1475), [#1531](https://github.com/matrix-org/matrix-spec/issues/1531))
- Support asynchronous media uploads, as per [MSC2246](https://github.com/matrix-org/matrix-spec-proposals/pull/2246). ([#1499](https://github.com/matrix-org/matrix-spec/issues/1499), [#1510](https://github.com/matrix-org/matrix-spec/issues/1510))
- Document the `m.mentions` property; the `.m.rule.is_user_mention` and `.m.rule.is_room_mention` push rules; and other notification behaviour, as per [MSC3952](https://github.com/matrix-org/matrix-spec-proposals/pull/3952). ([#1508](https://github.com/matrix-org/matrix-spec/issues/1508))
- Improve VoIP signaling, as per [MSC2746](https://github.com/matrix-org/matrix-spec-proposals/pull/2746). ([#1511](https://github.com/matrix-org/matrix-spec/issues/1511), [#1540](https://github.com/matrix-org/matrix-spec/issues/1540))
- Update the scope of transaction IDs, as per [MSC3970](https://github.com/matrix-org/matrix-spec-proposals/pull/3970). ([#1526](https://github.com/matrix-org/matrix-spec/issues/1526))
- Add an ability to redirect media downloads, as per [MSC3860](https://github.com/matrix-org/matrix-spec-proposals/pull/3860). ([#1529](https://github.com/matrix-org/matrix-spec/issues/1529))
- Add an ability to use an existing session to log in another, as per [MSC3882](https://github.com/matrix-org/matrix-spec-proposals/pull/3882). ([#1530](https://github.com/matrix-org/matrix-spec/issues/1530))
Spec Clarifications
- Clarify the sections of the specification concerning aggregation of child events. ([#1424](https://github.com/matrix-org/matrix-spec/issues/1424))
- Fix various typos throughout the specification. ([#1432](https://github.com/matrix-org/matrix-spec/issues/1432), [#1442](https://github.com/matrix-org/matrix-spec/issues/1442), [#1447](https://github.com/matrix-org/matrix-spec/issues/1447), [#1455](https://github.com/matrix-org/matrix-spec/issues/1455), [#1465](https://github.com/matrix-org/matrix-spec/issues/1465), [#1500](https://github.com/matrix-org/matrix-spec/issues/1500), [#1509](https://github.com/matrix-org/matrix-spec/issues/1509))
- Clarify that reply chain fallback for threads might not be present. ([#1439](https://github.com/matrix-org/matrix-spec/issues/1439))
- Clarify what event property the content-specific push rules match against. ([#1441](https://github.com/matrix-org/matrix-spec/issues/1441))
- Clarify the semantics that make requests idempotent. ([#1449](https://github.com/matrix-org/matrix-spec/issues/1449))
- Improve documentation of how clients use push rules. ([#1461](https://github.com/matrix-org/matrix-spec/issues/1461))
- Clarify that servers should enforce a default `limit` on a filter if one is not specified. ([#1463](https://github.com/matrix-org/matrix-spec/issues/1463))
- Disambiguate using property names with dots in them during push rule processing, as per [MSC3873](https://github.com/matrix-org/matrix-spec-proposals/pull/3873) and [MSC3980](https://github.com/matrix-org/matrix-spec-proposals/pull/3980). ([#1464](https://github.com/matrix-org/matrix-spec/issues/1464))
- Fix phrasing & typography in the registration endpoint description. Contributed by @HarHarLinks. ([#1474](https://github.com/matrix-org/matrix-spec/issues/1474))
- Remove outdated text saying that `state_default` is 0 if there is no `m.room.power_levels` event in a room. ([#1479](https://github.com/matrix-org/matrix-spec/issues/1479))
- Remove fictitious `token` parameter on `/keys/query` endpoint. ([#1485](https://github.com/matrix-org/matrix-spec/issues/1485))
- Fix rendering of properties with a list of types. ([#1487](https://github.com/matrix-org/matrix-spec/issues/1487))
- Clarify parts of the cross-signing signature upload request. ([#1495](https://github.com/matrix-org/matrix-spec/issues/1495))
- Remove the `dont_notify` and `coalesce` push rule actions, as per [MSC3987](https://github.com/matrix-org/matrix-spec-proposals/pull/3987). ([#1501](https://github.com/matrix-org/matrix-spec/issues/1501))
- Clarify `m.location` scheme by partially reverting [f1f32d3](https://github.com/matrix-org/matrix-spec/commit/f1f32d3a15c325ee8aa9d2c6bafd96c38069bb53). Contributed by @HarHarLinks. ([#1507](https://github.com/matrix-org/matrix-spec/issues/1507))
- Add missing `knock_restricted` join rule to the `m.room.join_rules` schema. ([#1535](https://github.com/matrix-org/matrix-spec/issues/1535))
### Server-Server API
Spec Clarifications
- Fix various typos throughout the specification. ([#1431](https://github.com/matrix-org/matrix-spec/issues/1431), [#1447](https://github.com/matrix-org/matrix-spec/issues/1447), [#1466](https://github.com/matrix-org/matrix-spec/issues/1466), [#1518](https://github.com/matrix-org/matrix-spec/issues/1518))
- Fix PDU examples by removing invalid OpenAPI reference to `examples/minimal_pdu.json`. ([#1454](https://github.com/matrix-org/matrix-spec/issues/1454))
- Remove leftover `{key_id}` from `/_matrix/key/v2/server/`. ([#1473](https://github.com/matrix-org/matrix-spec/issues/1473))
- Remove extraneous `age_ts` field from the reference hash calculation section. ([#1536](https://github.com/matrix-org/matrix-spec/issues/1536))
### Application Service API
New Endpoints
- [`POST /_matrix/app/v1/ping`](/application-service-api/#post_matrixappv1ping) ([#1516](https://github.com/matrix-org/matrix-spec/issues/1516))
- [`POST /_matrix/client/v1/appservice/{appserviceId}/ping`](/application-service-api/#post_matrixclientv1appserviceappserviceidping) ([#1516](https://github.com/matrix-org/matrix-spec/issues/1516))
Backwards Compatible Changes
- Add homeserver->appservice ping mechanism, as per [MSC2659](https://github.com/matrix-org/matrix-spec-proposals/pull/2659). Contributed by @tulir at @beeper. ([#1516](https://github.com/matrix-org/matrix-spec/issues/1516), [#1541](https://github.com/matrix-org/matrix-spec/issues/1541))
Spec Clarifications
- Fix various typos throughout the specification. ([#1447](https://github.com/matrix-org/matrix-spec/issues/1447))
### Identity Service API
Spec Clarifications
- Corrections to the response format of `/_matrix/identity/v2/store-invite`. ([#1486](https://github.com/matrix-org/matrix-spec/issues/1486))
### Push Gateway API
No significant changes.
### Room Versions
Spec Clarifications
- Clarifications of event ID formats in early room versions ([#1484](https://github.com/matrix-org/matrix-spec/issues/1484))
### Appendices
Spec Clarifications
- Clarify that the term "Canonical JSON" is a specific thing within the Matrix specification. ([#1468](https://github.com/matrix-org/matrix-spec/issues/1468))
- Remove references to groups. ([#1483](https://github.com/matrix-org/matrix-spec/issues/1483))
- Clarifications of event ID formats in early room versions. ([#1484](https://github.com/matrix-org/matrix-spec/issues/1484))
### Internal Changes/Tooling
Spec Clarifications
- Update references to Inter font. ([#1444](https://github.com/matrix-org/matrix-spec/issues/1444))
- Endpoint disclosures now hide everything but the URL. ([#1446](https://github.com/matrix-org/matrix-spec/issues/1446))
- Wrap $ref in allOf where other attributes are present, to improve OpenAPI compliance. ([#1457](https://github.com/matrix-org/matrix-spec/issues/1457))
- Minor cleanups to the GitHub Actions workflows ([#1476](https://github.com/matrix-org/matrix-spec/issues/1476))
- Fix generation of anchors for additional properties. ([#1488](https://github.com/matrix-org/matrix-spec/issues/1488))
- Fix various typos throughout the specification. ([#1534](https://github.com/matrix-org/matrix-spec/issues/1534))
- Document more of the spec release timeline/process. ([#1538](https://github.com/matrix-org/matrix-spec/issues/1538))