fix(mcp): coerce numeric tool args defensively

mcp_serve.py

@@ -115,6 +115,25 @@ def _load_channel_directory() -> dict:
         return {}
 
 
+def _coerce_int(
+    value,
+    *,
+    default: int,
+    minimum: int,
+    maximum: int,
+) -> int:
+    """Coerce value to int with fallback and clamping.
+
+    Used at MCP tool boundaries to handle invalid types from external clients.
+    Returns default if value cannot be converted to int.
+    """
+    try:
+        coerced = int(value)
+    except (TypeError, ValueError):
+        coerced = default
+    return max(minimum, min(coerced, maximum))
+
+
 def _extract_message_content(msg: dict) -> str:
     """Extract text content from a message, handling multi-part content."""
     content = msg.get("content", "")
@@ -465,6 +484,7 @@ def create_mcp_server(event_bridge: Optional[EventBridge] = None) -> "FastMCP":
             limit: Maximum number of conversations to return (default 50)
             search: Optional text to filter conversations by name
         """
+        limit = _coerce_int(limit, default=50, minimum=1, maximum=200)
         entries = _load_sessions_index()
         conversations = []
 
@@ -552,6 +572,7 @@ def create_mcp_server(event_bridge: Optional[EventBridge] = None) -> "FastMCP":
             session_key: The session key from conversations_list
             limit: Maximum number of messages to return (default 50, most recent)
         """
+        limit = _coerce_int(limit, default=50, minimum=1, maximum=200)
         entries = _load_sessions_index()
         entry = entries.get(session_key)
         if not entry:
@@ -664,6 +685,8 @@ def create_mcp_server(event_bridge: Optional[EventBridge] = None) -> "FastMCP":
             session_key: Optional filter to one conversation
             limit: Maximum events to return (default 20)
         """
+        after_cursor = _coerce_int(after_cursor, default=0, minimum=0, maximum=10**18)
+        limit = _coerce_int(limit, default=20, minimum=1, maximum=200)
         result = bridge.poll_events(
             after_cursor=after_cursor,
             session_key=session_key,
@@ -689,10 +712,17 @@ def create_mcp_server(event_bridge: Optional[EventBridge] = None) -> "FastMCP":
             session_key: Optional filter to one conversation
             timeout_ms: Maximum wait time in milliseconds (default 30000)
         """
+        after_cursor = _coerce_int(after_cursor, default=0, minimum=0, maximum=10**18)
+        timeout_ms = _coerce_int(
+            timeout_ms,
+            default=30000,
+            minimum=0,
+            maximum=300000,
+        )  # Cap at 5 minutes
         event = bridge.wait_for_event(
             after_cursor=after_cursor,
             session_key=session_key,
-            timeout_ms=min(timeout_ms, 300000),  # Cap at 5 minutes
+            timeout_ms=timeout_ms,
         )
         if event:
             return json.dumps({"event": event}, indent=2)