- Drop support for the undocumented /_matrix/client/v2_alpha API prefix. ([\#5190](https://github.com/matrix-org/synapse/issues/5190))
- Add an option to disable per-room profiles. ([\#5196](https://github.com/matrix-org/synapse/issues/5196))
- Stick an expiration date to any registered user missing one at startup if account validity is enabled. ([\#5204](https://github.com/matrix-org/synapse/issues/5204))
- Add experimental support for relations (aka reactions and edits). ([\#5209](https://github.com/matrix-org/synapse/issues/5209), [\#5211](https://github.com/matrix-org/synapse/issues/5211))
- Add experimental support for relations (aka reactions and edits). ([\#5209](https://github.com/matrix-org/synapse/issues/5209), [\#5211](https://github.com/matrix-org/synapse/issues/5211), [\#5203](https://github.com/matrix-org/synapse/issues/5203), [\#5212](https://github.com/matrix-org/synapse/issues/5212))
- Add a room version 4 which uses a new event ID format, as per [MSC2002](https://github.com/matrix-org/matrix-doc/pull/2002). ([\#5210](https://github.com/matrix-org/synapse/issues/5210), [\#5217](https://github.com/matrix-org/synapse/issues/5217))
Richard van der Hoff
6 years ago