fix(mcp): re-register tools during parked revival

tests/tools/test_mcp_parked_self_probe.py

@@ -8,10 +8,39 @@ revival probe on its own.
 """
 
 import asyncio
+from types import SimpleNamespace
+from unittest.mock import AsyncMock, MagicMock
 
 import pytest
 
 
+def test_revival_discovery_registers_tools_while_ready_is_cleared(monkeypatch):
+    """A managed server revival must publish tools before readiness is reset."""
+    from tools import mcp_tool
+    from tools.mcp_tool import MCPServerTask
+
+    server = MCPServerTask("srv")
+    server._config = {"url": "https://example.test/mcp"}
+    server.session = SimpleNamespace(
+        list_tools=AsyncMock(
+            return_value=SimpleNamespace(
+                tools=[SimpleNamespace(name="send_message")],
+            )
+        )
+    )
+    server._ready.clear()
+    server._registered_tool_names = []
+    monkeypatch.setitem(mcp_tool._servers, server.name, server)
+
+    register = MagicMock(return_value=["srv__send_message"])
+    monkeypatch.setattr(mcp_tool, "_register_server_tools", register)
+
+    asyncio.run(server._discover_tools())
+
+    register.assert_called_once_with(server.name, server, server._config)
+    assert server._registered_tool_names == ["srv__send_message"]
+
+
 @pytest.mark.no_isolate
 def test_parked_server_self_probes_and_revives(monkeypatch, tmp_path):
     """A parked server must revive on its own once the backend recovers,

tools/mcp_tool.py

@@ -2986,14 +2986,18 @@ class MCPServerTask:
         """Re-register tools after a post-ready reconnect if needed.
 
         Initial registration is performed by ``_discover_and_register_server``
-        after ``start()`` completes. During a later reconnect, however,
-        ``_ready`` remains set; if outage handling previously deregistered
-        stale tools (parking calls ``_deregister_tools``), a successful
-        revival must publish the freshly discovered tools again — otherwise
-        the transport comes back alive with zero registered tools.
+        after ``start()`` completes. During a later reconnect, outage handling
+        may clear ``_ready`` before discovery and may deregister stale tools.
+        A managed server can still be identified by its entry in ``_servers``;
+        publish its freshly discovered tools before transport readiness is
+        restored so a successful revival cannot come back with zero tools.
         """
-        if not self._ready.is_set() or self._registered_tool_names:
+        if self._registered_tool_names:
             return
+        if not self._ready.is_set():
+            with _lock:
+                if _servers.get(self.name) is not self:
+                    return
         self._registered_tool_names = _register_server_tools(
             self.name, self, self._config
         )