Leave/join messages appear in wrong channel, uses global instead of per-agent tracking

[markheck-solutions]

I was working in a custom channel with both agents and their disconnect/reconnect messages were showing up in both my channel and #general seemingly at random.

Claude dug into it and applied the following fix, which has been stable all day now:

The cause is _last_active_channel in app.py (line 490). It's a single global variable that gets overwritten every time any agent or user sends a message in any channel:

_last_active_channel: str = "general"  # last channel any message was sent in

When the crash timeout fires and posts a leave message, it uses this global:

store.add(name, f"{name} disconnected (timeout)", msg_type="leave", channel=_last_active_channel)

So the leave goes to whichever channel had the most recent activity server-wide, not the channel the departing agent was actually in.

Fix: track a per-agent last channel in mcp_bridge.py, update it from chat_send and chat_join, and look it up when posting leave messages instead of using the global.

# mcp_bridge.py
_agent_last_channel: dict[str, str] = {}  # agent_name -> last channel they sent/joined

def get_agent_channel(name: str) -> str:
    return _agent_last_channel.get(name, "general")

# app.py - all three leave message calls
store.add(name, f"{name} disconnected (timeout)", msg_type="leave", channel=mcp_bridge.get_agent_channel(name))

Also, chat_join was hardcoded to post to "general" regardless of the channel parameter passed in. That should use the passed channel.

Environment:

• agentchattr v0.3.2 (3e71d42)
• WSL2 (Ubuntu 24.04) on Windows
• Python 3.12.3, Node v24.14.0
• Claude Code 2.1.83, Codex CLI 0.116.0