fix(mcp): prevent parallel-safe prefix collisions

tests/tools/test_mcp_tool.py

@@ -3781,16 +3781,26 @@ class TestMcpParallelToolCalls:
 
     def test_is_mcp_tool_parallel_safe_no_servers(self):
         """MCP tool from unknown server returns False."""
-        from tools.mcp_tool import is_mcp_tool_parallel_safe, _parallel_safe_servers, _lock
+        from tools.mcp_tool import (
+            is_mcp_tool_parallel_safe, _mcp_tool_server_names,
+            _parallel_safe_servers, _lock,
+        )
         with _lock:
             _parallel_safe_servers.clear()
+            _mcp_tool_server_names.clear()
         assert is_mcp_tool_parallel_safe("mcp_docs_search") is False
 
     def test_is_mcp_tool_parallel_safe_with_flag(self):
         """MCP tool from a parallel-safe server returns True."""
-        from tools.mcp_tool import is_mcp_tool_parallel_safe, _parallel_safe_servers, _lock
+        from tools.mcp_tool import (
+            is_mcp_tool_parallel_safe, _mcp_tool_server_names,
+            _parallel_safe_servers, _lock,
+        )
         with _lock:
             _parallel_safe_servers.add("docs")
+            _mcp_tool_server_names["mcp_docs_search"] = "docs"
+            _mcp_tool_server_names["mcp_docs_read_file"] = "docs"
+            _mcp_tool_server_names["mcp_github_list_repos"] = "github"
         try:
             assert is_mcp_tool_parallel_safe("mcp_docs_search") is True
             assert is_mcp_tool_parallel_safe("mcp_docs_read_file") is True
@@ -3799,23 +3809,86 @@ class TestMcpParallelToolCalls:
         finally:
             with _lock:
                 _parallel_safe_servers.discard("docs")
+                _mcp_tool_server_names.pop("mcp_docs_search", None)
+                _mcp_tool_server_names.pop("mcp_docs_read_file", None)
+                _mcp_tool_server_names.pop("mcp_github_list_repos", None)
 
     def test_is_mcp_tool_parallel_safe_server_with_underscores(self):
         """Server names containing underscores are correctly matched."""
-        from tools.mcp_tool import is_mcp_tool_parallel_safe, _parallel_safe_servers, _lock
+        from tools.mcp_tool import (
+            is_mcp_tool_parallel_safe, _mcp_tool_server_names,
+            _parallel_safe_servers, _lock,
+        )
         with _lock:
             _parallel_safe_servers.add("my_server")
+            _mcp_tool_server_names["mcp_my_server_query"] = "my_server"
         try:
             assert is_mcp_tool_parallel_safe("mcp_my_server_query") is True
         finally:
             with _lock:
                 _parallel_safe_servers.discard("my_server")
+                _mcp_tool_server_names.pop("mcp_my_server_query", None)
+
+    def test_is_mcp_tool_parallel_safe_uses_exact_registered_server(self):
+        """Ambiguous MCP names must not match a shorter parallel-safe prefix."""
+        from tools.mcp_tool import (
+            is_mcp_tool_parallel_safe, _mcp_tool_server_names,
+            _parallel_safe_servers, _lock,
+        )
+        with _lock:
+            _parallel_safe_servers.add("a")
+            _mcp_tool_server_names["mcp_a_search"] = "a"
+            _mcp_tool_server_names["mcp_a_b_tool"] = "a_b"
+        try:
+            assert is_mcp_tool_parallel_safe("mcp_a_search") is True
+            assert is_mcp_tool_parallel_safe("mcp_a_b_tool") is False
+        finally:
+            with _lock:
+                _parallel_safe_servers.discard("a")
+                _mcp_tool_server_names.pop("mcp_a_search", None)
+                _mcp_tool_server_names.pop("mcp_a_b_tool", None)
+
+    def test_registered_tool_provenance_prevents_prefix_collision(self):
+        """Registration records exact server ownership for ambiguous names."""
+        from tools.registry import registry
+        from tools.mcp_tool import (
+            _mcp_tool_server_names, _parallel_safe_servers,
+            _register_server_tools, is_mcp_tool_parallel_safe, _lock,
+        )
+
+        server = _make_mock_server(
+            "a_b",
+            tools=[_make_mcp_tool("tool", "Ambiguous tool name")],
+        )
+        registered = _register_server_tools("a_b", server, {})
+        try:
+            assert registered == ["mcp_a_b_tool"]
+            with _lock:
+                assert _mcp_tool_server_names["mcp_a_b_tool"] == "a_b"
+                _parallel_safe_servers.add("a")
+            assert is_mcp_tool_parallel_safe("mcp_a_b_tool") is False
+
+            with _lock:
+                _parallel_safe_servers.add("a_b")
+            assert is_mcp_tool_parallel_safe("mcp_a_b_tool") is True
+        finally:
+            for tool_name in registered:
+                registry.deregister(tool_name)
+            with _lock:
+                _parallel_safe_servers.discard("a")
+                _parallel_safe_servers.discard("a_b")
+                _mcp_tool_server_names.pop("mcp_a_b_tool", None)
 
     def test_is_mcp_tool_parallel_safe_no_tool_suffix(self):
         """Tool name that is just 'mcp_{server}' without a tool part returns False."""
-        from tools.mcp_tool import is_mcp_tool_parallel_safe, _parallel_safe_servers, _lock
+        from tools.mcp_tool import (
+            is_mcp_tool_parallel_safe, _mcp_tool_server_names,
+            _parallel_safe_servers, _lock,
+        )
         with _lock:
             _parallel_safe_servers.add("docs")
+            _mcp_tool_server_names.pop("mcp_docs", None)
+            _mcp_tool_server_names.pop("mcp_docs_", None)
         try:
             # "mcp_docs" has no tool part after the server name
             assert is_mcp_tool_parallel_safe("mcp_docs") is False