fix(relay): republish group metadata when a huddle auto-archives

[Pratikkale26]

Summary

When the last audio peer leaves a huddle, the relay archives the ephemeral backing channel in the database but never republishes kind:39000. Clients build their channel list from kind:39000, so the channel stays in the sidebar forever, on every client, including a fresh install — and no user action can remove it.

Fixes #4879.

The divergence, measured

Against a local relay on main, after the last audio peer drops:

# relay log
INFO audio room empty — auto-ending huddle channel_id=c773e368-…

# database — archived
$ select archived_at is not null from channels where id = 'c773e368-…';
 t

# newest kind:39000 for that channel — NOT archived
[["d","c773e368-…"],["name","huddle-c773e368-…"],["public"],["closed"],
 ["t","stream"],["ttl","3600"],["ttl_deadline","2026-08-05T17:25:13Z"]]
  ↑ no ["archived","true"]

The relay knows. No client ever will.

Root cause

crates/buzz-relay/src/audio/handler.rs — the auto-end path archives the channel and emits only kind:48103:

match state.db.archive_channel(tenant.community(), channel_id).await {
    Ok(()) => {
        room_emptied = state.audio_rooms.cleanup_if_empty(...);
        emit_participant_event(..., Kind::Custom(48103), ...).await;
        // never calls emit_group_discovery_events
    }
    ...
}

Every other archive path publishes the discovery update:

Path	Republishes kind:39000?
Owner-driven kind:9002 (handlers/side_effects.rs:1649)	✅
Ephemeral reaper (main.rs:685)	✅
Huddle audio auto-end (audio/handler.rs)	❌

This does not self-heal. The reaper is the one path that would republish, but reap_expired_ephemeral_channels filters archived_at IS NULL, so a row archived here is never picked up. And kind:39000 is replaceable, so the stale event is what every future client syncs.

The fix

After a successful archive_channel, mirror what the reaper already does:

• emit_group_discovery_events — republishes kind:39000, which stamps ["archived","true"] from channel.archived_at. This is the actual fix.
• evict_all_channel_subscriptions — drops live subscriptions so connected clients remove the channel immediately, rather than waiting for a reconnect.

Both are best-effort and logged on failure: a discovery hiccup must not change huddle teardown, which has already completed by this point.

One deliberate omission

The reaper also emits a channel_auto_archived system message. I left that out here: this path already emits kind:48103 (huddle ended), which is the semantically precise signal for a huddle, so a second "auto archived" notice would be redundant in the timeline. Happy to add it if maintainers prefer strict parity with the reaper — it's a one-line change.

On the broader suggestion in the issue

The issue notes that coupling the republish to the archive itself would make this class of divergence unrepresentable. I agree that's the better end state, but db.archive_channel lives in buzz-db, which has no access to relay state and cannot emit events, so it would need a relay-level wrapper adopted by all three paths. That's a refactor of two currently-working paths and felt out of scope for a bug fix — happy to follow up with it separately if wanted.

Testing

New crates/buzz-test-client/tests/e2e_huddle_archive.rs drives the real path end to end: create parent + ephemeral channel, publish the kind:48100 link, connect a peer to /huddle/{id}/audio, complete the NIP-42 handshake, wait for joined, then drop the socket and assert the newest kind:39000 carries ["archived","true"].

Validated by reverting the fix and re-running — it fails with:

assertion `left == right` failed: after the last audio peer leaves, the newest kind:39000
for the huddle channel must carry ["archived", "true"] — otherwise clients keep the channel forever
  left: Some(false)
 right: Some(true)

cargo fmt --all -- --check                              ✅
cargo clippy --workspace --all-targets -- -D warnings    ✅
just test                                                ✅
RELAY_URL=ws://localhost:3000 cargo test -p buzz-test-client \
  --test e2e_huddle_archive -- --ignored                 ✅

Related

• Deleting an auto-archived huddle channel returns 400 "channel is archived" #2954 — proposes letting kind:9008 through for archived channels. Complementary: that one is about deleting a ghost row, this one stops the ghost from being created.
• Searched open PRs for Huddle auto-archive never republishes kind:39000, so the ephemeral channel stays live in every client forever #4879 and for huddle/archive work — none found.