### Client-Server API
Backwards Compatible Changes
- Add `m.reference` relations, as per [MSC3267](https://github.com/matrix-org/matrix-spec-proposals/pull/3267). ([#1206](https://github.com/matrix-org/matrix-spec/issues/1206))
- Add missing documentation for `m.key.verification.request` msgtype for in-room verification. ([#1271](https://github.com/matrix-org/matrix-spec/issues/1271))
Spec Clarifications
- Fix various typos throughout the specification. ([#1260](https://github.com/matrix-org/matrix-spec/issues/1260), [#1265](https://github.com/matrix-org/matrix-spec/issues/1265), [#1276](https://github.com/matrix-org/matrix-spec/issues/1276))
- Fix naming of `device_one_time_keys_count` in `/sync`. ([#1266](https://github.com/matrix-org/matrix-spec/issues/1266))
- Improve display of event subtypes. ([#1283](https://github.com/matrix-org/matrix-spec/issues/1283))
- Improve documentation about ephemeral events. ([#1284](https://github.com/matrix-org/matrix-spec/issues/1284))
- Define a 400 response from `/_matrix/client/v3/directory/rooms/{roomAlias}`. ([#1286](https://github.com/matrix-org/matrix-spec/issues/1286))
- Clarify parts of the end-to-end encryption sections. ([#1294](https://github.com/matrix-org/matrix-spec/issues/1294), [#1345](https://github.com/matrix-org/matrix-spec/issues/1345))
- Various clarifications throughout the specification. ([#1306](https://github.com/matrix-org/matrix-spec/issues/1306))
- Replace `set_sound` push rule action by `set_tweak`. ([#1318](https://github.com/matrix-org/matrix-spec/issues/1318))
- Clarify the behavior of `PUT /_matrix/client/v3/pushrules/{scope}/{kind}/{ruleId}`. ([#1319](https://github.com/matrix-org/matrix-spec/issues/1319))
- Clarify that `.m.rule.master` has a higher priority than any push rule. ([#1320](https://github.com/matrix-org/matrix-spec/issues/1320))
- Require request field `refresh_token` at endpoint `POST /_matrix/client/v3/refresh`. ([#1323](https://github.com/matrix-org/matrix-spec/issues/1323))
- Fix a number of broken links in the specification. ([#1330](https://github.com/matrix-org/matrix-spec/issues/1330))
- Add example read receipt to `GET /_matrix/client/v3/sync` response example. ([#1341](https://github.com/matrix-org/matrix-spec/issues/1341))
### Server-Server API
Spec Clarifications
- Fix a number of broken links in the specification. ([#1330](https://github.com/matrix-org/matrix-spec/issues/1330))
### Application Service API
Spec Clarifications
- Clarify that application services can only register an interest in local users, as per [MSC3905](https://github.com/matrix-org/matrix-spec-proposals/issues/3905). ([#1305](https://github.com/matrix-org/matrix-spec/issues/1305))
### Identity Service API
Spec Clarifications
- Fix a number of broken links in the specification. ([#1330](https://github.com/matrix-org/matrix-spec/issues/1330))
### Push Gateway API
No significant changes.
### Room Versions
Spec Clarifications
- Reword the event auth rules to clarify that users cannot demote other users with the same power level. ([#1269](https://github.com/matrix-org/matrix-spec/issues/1269))
- Various clarifications to the text on event authorisation rules. ([#1270](https://github.com/matrix-org/matrix-spec/issues/1270))
- Fix a number of broken links in the specification. ([#1330](https://github.com/matrix-org/matrix-spec/issues/1330))
### Appendices
No significant changes.
### Internal Changes/Tooling
Backwards Compatible Changes
- Update docsy theme to v0.5.0 + matrix.org modifications (https://github.com/matrix-org/docsy/commit/a0032f8db919a6c67ba6cdef2c455f105b6272a2). ([#1295](https://github.com/matrix-org/matrix-spec/issues/1295))
Spec Clarifications
- Improve error messages emitted by `resolve-additional-types` template. ([#1303](https://github.com/matrix-org/matrix-spec/issues/1303))
- Fix link to API viewer. ([#1308](https://github.com/matrix-org/matrix-spec/issues/1308))
- Stop rendering the subsections of the Client-Server API and Room Versions specs as their own separate pages. ([#1317](https://github.com/matrix-org/matrix-spec/issues/1317))
- Use a link checker to ensure that we do not have broken links. ([#1329](https://github.com/matrix-org/matrix-spec/issues/1329), [#1338](https://github.com/matrix-org/matrix-spec/issues/1338))
- Update instructions to preview Swagger definitions. ([#1331](https://github.com/matrix-org/matrix-spec/issues/1331))
- Make definition anchors more unique. ([#1339](https://github.com/matrix-org/matrix-spec/issues/1339))
- Generate the unstable changelogs with towncrier, for consistency. ([#1340](https://github.com/matrix-org/matrix-spec/issues/1340))
- Update CONTRIBUTING.md to mention that non-content changes to this repo should have an "internal" changelog entry. ([#1342](https://github.com/matrix-org/matrix-spec/issues/1342))
- Update module summary table with new modules: Event Replacements, Threading and Reference Relations. ([#1344](https://github.com/matrix-org/matrix-spec/issues/1344))
- Disable RSS generation for the spec. ([#1346](https://github.com/matrix-org/matrix-spec/issues/1346))