Guild access tokens are short-lived (~15 min); the inbound socket
survives via socket.io reconnect but the token captured at connect
time goes stale, so attachment downloads (and reply posts) start
401ing on long-lived agents. Re-login with the agent's Fabric API key
on a short TTL and use the fresh token for fetch + post.
Verified live: 'fabric: fetched 1 attachment(s)' now succeeds where it
previously logged 'attachment fetch 401'.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
hzhang
d79a04b8a3