mautrix bridges ship with backfill disabled by default
Diagnosing why a freshly-logged-in Matrix puppet bridge creates portal rooms for every conversation but leaves them empty of historical messages
The bridge config's backfill.enabled defaults to false in mautrix-linkedin (and the other Go bridges). On first login the bridge happily creates one portal room per remote conversation — looking like success — but until the flag is flipped, the only messages that flow are NEW ones arriving via the realtime/SSE loop. Flip backfill.enabled: true and restart, and the resync loop fills empty rooms (up to max_initial_messages per chat, max_catchup_messages for known chats post-restart). Unrelated nuance: backfill.queue only does anything on Beeper's hungryserv since standard Synapse can't insert into pre-existing history — the bridge fills rooms forward-style, with old timestamps tacked on after the room-creation event, and the client sorts them chronologically.
When a bridge looks half-working — chats appear but rooms are empty — check backfill.enabled before suspecting double-puppeting or 403s. Empty rooms with no errors usually means backfill is off, not that the bridge is broken.