sorb chose C, fully disabling federation at the edge. Building it showed that would
have killed group calls: lk-jwt-service verifies OpenID tokens through
/_matrix/federation/v1/openid/userinfo and reaches it over the public name, so a path
block on /_matrix/federation is the mrtc outage again with a different cause. C was
dropped and B implemented.
The ADR records the measurement the decision rests on - zero destinations, zero remote
users, zero rooms with outside participation in four months - and the trap, so nobody
completes C later as a quick follow-up. Doing that safely means binding the auth
service to Synapse in-cluster first, which is its own undertaking with a call
acceptance.
Also recorded because it nearly slipped through: Flux applied the ConfigMap while
Synapse kept running its old config from 2026-08-01. The config is rendered at pod
start, so the change was inert until a restart - the same class as #0044. Verified
afterwards inside the running process rather than in the ConfigMap, with the client
API and the OpenID endpoint still answering.
Thore Cimbal
15134d1846