### Client-Server API
Backwards Compatible Changes
- Add information on standard error responses for unknown endpoints/methods, as per [MSC3743](https://github.com/matrix-org/matrix-spec-proposals/pull/3743). ([#1347](https://github.com/matrix-org/matrix-spec/issues/1347))
- Add `/rooms//timestamp_to_event` endpoint, as per [MSC3030](https://github.com/matrix-org/matrix-spec-proposals/pull/3030). ([#1366](https://github.com/matrix-org/matrix-spec/issues/1366))
- Define `hkdf-hmac-sha256.v2` MAC method for SAS verification, as per [MSC3783](https://github.com/matrix-org/matrix-spec-proposals/pull/3783). ([#1412](https://github.com/matrix-org/matrix-spec/issues/1412))
Spec Clarifications
- Clarify the power levels integer range. ([#1169](https://github.com/matrix-org/matrix-spec/issues/1169), [#1355](https://github.com/matrix-org/matrix-spec/issues/1355))
- Clarify that `/context` always returns `event` even if `limit` is zero. Contributed by @sumnerevans at @beeper. ([#1239](https://github.com/matrix-org/matrix-spec/issues/1239))
- Clarify what fields are required when deleting a pusher ([#1321](https://github.com/matrix-org/matrix-spec/issues/1321))
- Improve the presentation of push rule kinds and actions. ([#1348](https://github.com/matrix-org/matrix-spec/issues/1348))
- Add missing description to m.call.answer schema. ([#1353](https://github.com/matrix-org/matrix-spec/issues/1353))
- Fix various typos throughout the specification. ([#1363](https://github.com/matrix-org/matrix-spec/issues/1363))
- Clarify parts of the end-to-end encryption sections. ([#1381](https://github.com/matrix-org/matrix-spec/issues/1381))
- Move login API definitions to the right heading. Contributed by @HarHarLinks. ([#1382](https://github.com/matrix-org/matrix-spec/issues/1382))
- Clarify which events will be included in Stripped State. Contributed by @andybalaam. ([#1409](https://github.com/matrix-org/matrix-spec/issues/1409))
- Add links to the spec for the definition of 3PID `medium`. ([#1417](https://github.com/matrix-org/matrix-spec/issues/1417))
- Correct the order of the default override pushrules in the spec. ([#1421](https://github.com/matrix-org/matrix-spec/issues/1421))
- Improve distinction between tags and their attributes in the rich text section. Contributed by Nico. ([#1433](https://github.com/matrix-org/matrix-spec/issues/1433))
### Server-Server API
Breaking Changes
- Remove `keyId` from the server `/keys` endpoints, as per [MSC3938](https://github.com/matrix-org/matrix-spec-proposals/pull/3938). ([#1350](https://github.com/matrix-org/matrix-spec/issues/1350))
Backwards Compatible Changes
- Add information on standard error responses for unknown endpoints/methods, as per [MSC3743](https://github.com/matrix-org/matrix-spec-proposals/pull/3743). ([#1347](https://github.com/matrix-org/matrix-spec/issues/1347))
- Add `/timestamp_to_event/` endpoint, as per [MSC3030](https://github.com/matrix-org/matrix-spec-proposals/pull/3030). ([#1366](https://github.com/matrix-org/matrix-spec/issues/1366))
- Extend `/_matrix/federation/v2/send_join` to allow omitting membership events, per [MSC3706](https://github.com/matrix-org/matrix-doc/pull/3706). ([#1393](https://github.com/matrix-org/matrix-spec/issues/1393), [#1398](https://github.com/matrix-org/matrix-spec/issues/1398))
- Note that `/_matrix/federation/v2/send_join` should include heroes for nameless rooms, even when allowed to omit membership events, per [MSC3943](https://github.com/matrix-org/matrix-doc/pull/3943). ([#1425](https://github.com/matrix-org/matrix-spec/issues/1425))
Spec Clarifications
- Include examples inline instead of using a reference for invite endpoint definitions. ([#1349](https://github.com/matrix-org/matrix-spec/issues/1349))
- Fix `POST _matrix/federation/v1/user/keys/claim` response schema. ([#1351](https://github.com/matrix-org/matrix-spec/issues/1351))
- Correct the default invite level definition in the "Checks performed on receipt of a PDU" section. ([#1371](https://github.com/matrix-org/matrix-spec/issues/1371))
- Clarify that CNAMEs are permissible for server names. ([#1376](https://github.com/matrix-org/matrix-spec/issues/1376))
- Fix `edu_type` in EDU examples. ([#1383](https://github.com/matrix-org/matrix-spec/issues/1383))
### Application Service API
Backwards Compatible Changes
- Add information on standard error responses for unknown endpoints/methods, as per [MSC3743](https://github.com/matrix-org/matrix-spec-proposals/pull/3743). ([#1347](https://github.com/matrix-org/matrix-spec/issues/1347))
### Identity Service API
Backwards Compatible Changes
- Add information on standard error responses for unknown endpoints/methods, as per [MSC3743](https://github.com/matrix-org/matrix-spec-proposals/pull/3743). ([#1347](https://github.com/matrix-org/matrix-spec/issues/1347))
### Push Gateway API
Backwards Compatible Changes
- Add information on standard error responses for unknown endpoints/methods, as per [MSC3743](https://github.com/matrix-org/matrix-spec-proposals/pull/3743). ([#1347](https://github.com/matrix-org/matrix-spec/issues/1347))
### Room Versions
Backwards Compatible Changes
- Update the default room version to 10, as per [MSC3904](https://github.com/matrix-org/matrix-spec-proposals/pull/3904). ([#1397](https://github.com/matrix-org/matrix-spec/issues/1397))
Spec Clarifications
- Clarify the grammar for room versions. ([#1422](https://github.com/matrix-org/matrix-spec/issues/1422))
- Fix various typos throughout the specification. ([#1423](https://github.com/matrix-org/matrix-spec/issues/1423))
### Appendices
No significant changes.
### Internal Changes/Tooling
Spec Clarifications
- Add link to the unstable spec to the README. ([#1357](https://github.com/matrix-org/matrix-spec/issues/1357))
- Improve safety of the proposals retrieval script in the event of failure. ([#1368](https://github.com/matrix-org/matrix-spec/issues/1368))
- Rename `` to `content` in the OpenAPI files for content uploads. ([#1370](https://github.com/matrix-org/matrix-spec/issues/1370))
- Stop autogenerating examples where we already have an example. ([#1384](https://github.com/matrix-org/matrix-spec/issues/1384))
- Improve formatting of definitions in the Push Notifications section. ([#1415](https://github.com/matrix-org/matrix-spec/issues/1415))