The universal MCP server (a2a_mcp_server.py) was outbound-only — agents
in standalone runtimes (Claude Code, hermes, codex, etc.) could
delegate, list peers, and write memories, but never observed the
canvas-user or peer-agent messages addressed to them. This blocked
"constantly responding" loops without forcing operators back onto a
runtime-specific channel plugin.
This PR closes the inbound gap with a poller-fed in-memory queue and
three new MCP tools:
- wait_for_message(timeout_secs?) — block until next message arrives
- inbox_peek(limit?) — list pending messages (non-destructive)
- inbox_pop(activity_id) — drop a handled message
A daemon thread polls /workspaces/:id/activity?type=a2a_receive every
5s, fills the queue from the cursor (since_id), and persists the cursor
to ${CONFIGS_DIR}/.mcp_inbox_cursor so a restart doesn't replay backlog.
On 410 (cursor pruned) we fall back to since_secs=600 for a bounded
recovery window. Activity-row → InboxMessage extraction mirrors the
molecule-mcp-claude-channel plugin's extractText (envelope shapes #1-3
+ summary fallback).
mcp_cli.main starts the poller alongside the existing register +
heartbeat threads. In-container runtimes (which have push delivery via
canvas WebSocket) skip activation, so inbox tools return an
informational "(inbox not enabled)" message instead of double-delivery.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
b47d4ceb00