Synapse 1.151.0rc1 (2026-03-31)

Features

Add stable support for MSC4284 Policy Servers. (#19503)
Update and stabilize support for MSC2666: Get rooms in common with another user. Contributed by @tulir @ Beeper. (#19511)
Updated experimental support for MSC4388: Secure out-of-band channel for sign in with QR. (#19573)
Stabilize room_version and encryption fields in the space/room /hierarchy API (part of MSC3266). (#19576)
Introduce a configuration option to allow using HTTP/2 over plaintext when Synapse connects to Matrix Authentication Service. (#19586)

Fix MSC4284 Policy Servers implementation to skip signing org.matrix.msc4284.policy and m.room.policy state events. (#19503)
Correctly apply MSC4284 Policy Server signatures to events when the sender and policy server have the same server name. (#19503)
Allow Synapse to start up even when discovery fails for an OpenID Connect provider. (#19509)
Fix quarantine media admin APIs sometimes returning inaccurate counts for remote media. (#19559)
Fix Build and push complement image CI job not having poetry available for the Complement runner script. (#19578)
Increase timeout for policy server requests to avoid repeated requests for checking media. (#19629)

Fix small comment typo in config output from the demo/start.sh script. (#19538)
Add MSC3820 comment context to RoomVersion attributes. (#19577)
Remove redacted_because from internal unsigned. (#19581)
Prevent sending registration emails if registration is disabled. (#19585)
Port RoomVersion to Rust. (#19589)
Only show failing Complement tests in the formatted output in CI. (#19590)
Ensure old Complement test files are removed when downloading a Complement checkout via ./scripts-dev/complement.sh. (#19592)
Update HomeserverTestCase.pump() docstring to demystify behavior (Twisted reactor/clock). (#19602)
Deprecate HomeserverTestCase.pump() in favor of more direct HomeserverTestCase.reactor.advance(...) usage. (#19602)
Lower the Postgres database statement_timeout to 10m (previously 1h). (#19604)