Merge PR #892: fix MCP connection retry and concurrent connection guard

nanobot/agent/loop.py

@@ -94,6 +94,7 @@ class AgentLoop:
         self._mcp_servers = mcp_servers or {}
         self._mcp_stack: AsyncExitStack | None = None
         self._mcp_connected = False
+        self._mcp_connecting = False
         self._consolidating: set[str] = set()  # Session keys with consolidation in progress
         self._register_default_tools()
 
@@ -131,13 +132,25 @@ class AgentLoop:
 
     async def _connect_mcp(self) -> None:
         """Connect to configured MCP servers (one-time, lazy)."""
-        if self._mcp_connected or not self._mcp_servers:
+        if self._mcp_connected or self._mcp_connecting or not self._mcp_servers:
             return
-        self._mcp_connected = True
+        self._mcp_connecting = True
         from nanobot.agent.tools.mcp import connect_mcp_servers
+        try:
             self._mcp_stack = AsyncExitStack()
             await self._mcp_stack.__aenter__()
             await connect_mcp_servers(self._mcp_servers, self.tools, self._mcp_stack)
+            self._mcp_connected = True
+        except Exception as e:
+            logger.error("Failed to connect MCP servers (will retry next message): {}", e)
+            if self._mcp_stack:
+                try:
+                    await self._mcp_stack.aclose()
+                except Exception:
+                    pass
+                self._mcp_stack = None
+        finally:
+            self._mcp_connecting = False
 
     def _set_tool_context(self, channel: str, chat_id: str, message_id: str | None = None) -> None:
         """Update context for all tools that need routing info."""