Mention picker validates against local managed-agents store instead of relay membership (kind:39002); locally registering remote agents intercepts mentions

[idk-its-unknown]

Summary

Two related problems for agents that are relay members but run on a remote host (external buzz-acp instances, not spawned by the desktop app):

1. False "not in channel" warning. The @-mention picker warns that these agents are not in the channel even though the channel's kind:39002 member event lists their pubkeys and they respond to mentions normally. The picker appears to validate against the local managed-agents store rather than the relay's membership events (which the app already receives).

2. Local registration intercepts mentions. If such agents are added to the local store (agents/managed-agents.json) so they render in the Agents tab, mentioning them fails hard: "Could not start agent mention: : This agent's configuration is missing — it may still be syncing or was deleted on another device." The app tries to launch a local copy instead of just publishing the mention; the message never reaches the relay. There is no way to register an agent as display-only/remote.

Repro

1. Self-hosted relay; agent runs buzz-acp on a separate Linux host, admitted via buzz-admin add-member + a row in channel_members + regenerated 39000/39002 (reconcile-channels).
2. Desktop app (Windows, v0.5.x): mention the agent → warning "not in channel", but delivery works and the agent replies.
3. Add the agent to managed-agents.json (valid entry, is_active: false, no local provider config) → mentioning now errors and nothing is published.

Expected

• Picker membership check sourced from the channel's 39002 event (or channel_members), not the local spawn registry.
• Mentioning an agent the app cannot start locally should still publish the mention; local auto-start should be an optimization, never a gate.

Environment

Desktop v0.5.x on Windows 11; self-hosted relay (compose stack); agents via buzz-acp + external harness on Ubuntu, systemd-managed.

[barrettchelsea0]

连接池大小有经验值分享吗 ✨🧪

[jaozolins]

Self-hosting Buzz on a VPS with server-side agents (buzz-acp under systemd). Hit this exact path: Desktop @ picker only surfaces local managed agents, so our remote agent either disappears from @ or loses proper Activity/ownership chrome. +1 — room membership (or relay-visible agents) should be enough to mention.