feat(tools): add mcp support

nanobot/agent/loop.py

@@ -1,6 +1,7 @@
 """Agent loop: the core processing engine."""
 
 import asyncio
+from contextlib import AsyncExitStack
 import json
 from pathlib import Path
 from typing import Any
@@ -46,6 +47,7 @@ class AgentLoop:
         cron_service: "CronService | None" = None,
         restrict_to_workspace: bool = False,
         session_manager: SessionManager | None = None,
+        mcp_servers: dict | None = None,
     ):
         from nanobot.config.schema import ExecToolConfig
         from nanobot.cron.service import CronService
@@ -73,6 +75,9 @@ class AgentLoop:
         )
         
         self._running = False
+        self._mcp_servers = mcp_servers or {}
+        self._mcp_stack: AsyncExitStack | None = None
+        self._mcp_connected = False
         self._register_default_tools()
     
     def _register_default_tools(self) -> None:
@@ -107,9 +112,20 @@ class AgentLoop:
         if self.cron_service:
             self.tools.register(CronTool(self.cron_service))
     
+    async def _connect_mcp(self) -> None:
+        """Connect to configured MCP servers (one-time, lazy)."""
+        if self._mcp_connected or not self._mcp_servers:
+            return
+        self._mcp_connected = True
+        from nanobot.agent.tools.mcp import connect_mcp_servers
+        self._mcp_stack = AsyncExitStack()
+        await self._mcp_stack.__aenter__()
+        await connect_mcp_servers(self._mcp_servers, self.tools, self._mcp_stack)
+
     async def run(self) -> None:
         """Run the agent loop, processing messages from the bus."""
         self._running = True
+        await self._connect_mcp()
         logger.info("Agent loop started")
         
         while self._running:
@@ -136,6 +152,15 @@ class AgentLoop:
             except asyncio.TimeoutError:
                 continue
     
+    async def _close_mcp(self) -> None:
+        """Close MCP connections."""
+        if self._mcp_stack:
+            try:
+                await self._mcp_stack.aclose()
+            except (RuntimeError, BaseExceptionGroup):
+                pass  # MCP SDK cancel scope cleanup is noisy but harmless
+            self._mcp_stack = None
+
     def stop(self) -> None:
         """Stop the agent loop."""
         self._running = False
@@ -225,6 +250,8 @@ class AgentLoop:
                     messages = self.context.add_tool_result(
                         messages, tool_call.id, tool_call.name, result
                     )
+                # Interleaved CoT: reflect before next action
+                messages.append({"role": "user", "content": "Reflect on the results and decide next steps."})
             else:
                 # No tool calls, we're done
                 final_content = response.content
@@ -330,6 +357,8 @@ class AgentLoop:
                     messages = self.context.add_tool_result(
                         messages, tool_call.id, tool_call.name, result
                     )
+                # Interleaved CoT: reflect before next action
+                messages.append({"role": "user", "content": "Reflect on the results and decide next steps."})
             else:
                 final_content = response.content
                 break
@@ -367,6 +396,7 @@ class AgentLoop:
         Returns:
             The agent's response.
         """
+        await self._connect_mcp()
         msg = InboundMessage(
             channel=channel,
             sender_id="user",