Channel message routing: inbound notifications and outbound verification #36

Parent: #32
Blocked by: All prior sub-issues

Problem

Two halves of channel messaging are broken:

Inbound: The bridge's runtime.channel.reply() sends notifications/astrid.inboundMessage to the Rust host (see astrid_bridge.mjs:116-123). But AstridClientHandler (in astrid-mcp) doesn't handle this notification — messages are silently dropped.

Outbound: When the agent calls a send tool, it needs to route through the plugin. This is likely automatic once Items 1+2 land — if the Unicity plugin registers a send tool via registerTool(), the tool wiring makes it reachable. Verify before building anything.

Approach — Inbound

1. Define an InboundChannelMessage struct with fields: plugin_id, context (the context object from the bridge), and content
2. Add a bounded mpsc::channel(256) sender to either AstridClientHandler or McpPlugin's notification path
3. Handle notifications/astrid.inboundMessage in the notification dispatch — validate payload size (<1MB), extract fields, send through the channel
4. The DaemonServer consumes from the receiver, finds the appropriate agent session, and injects the message as a new user turn

The notification arrives via the rmcp ClientHandler trait. Check AstridClientHandler in crates/astrid-mcp/src/capabilities.rs — it currently handles on_tool_list_changed (line 682). Custom notifications may need a different hook point; check rmcp's ClientHandler trait for a on_notification or similar method.

Approach — Outbound

Verify after Items 1-3: load the Unicity plugin and check what tools it exports. If it registers a send tool via registerTool(), Items 1+2 make it automatically available (appears in LLM tool list, dispatches through Peer<RoleClient>, bridge routes to handler). If no send tool exists, add a synthetic one or use an MCP notification path.

Key Files

• crates/astrid-mcp/src/capabilities.rs — AstridClientHandler (line 419), rmcp ClientHandler impl (line 445)
• crates/astrid-plugins/src/mcp_plugin.rs — McpPlugin notification handling
• crates/astrid-gateway/src/server.rs — DaemonServer and session routing
• crates/openclaw-bridge/bridge/astrid_bridge.mjs — runtime.channel.reply() (line 116-123) shows the notification format

Gotchas

• The bridge sends: { method: "notifications/astrid.inboundMessage", params: { pluginId, context, content } }
• Use a bounded channel (mpsc::channel(256)) to prevent unbounded memory growth. Log a warning and drop on full.
• Validate payload size before forwarding — reject >1MB to prevent DoS from a compromised plugin.
• The DaemonServer doesn't currently have a message router — this may need a simple lookup from plugin ID to session. Consider which session should receive the message (the most recent one? all of them?).
• This is the most architecturally involved item. It may be worth splitting into two sub-PRs: (a) notification capture + channel, (b) session injection + routing.

Verification

• Send a message through the bridge's channel.reply() → verify it appears on the Rust receiver
• Outbound: verify Unicity's send tool appears in tool list and is callable
• End-to-end: CLI → agent → Unicity channel → verify round-trip
• cargo test --workspace -- --quiet passes