fix(tests): don't stomp real mcp with MagicMocks when mcp is installed

code_puppy/agents/_runtime.py

@@ -409,8 +409,8 @@ async def run_agent_task() -> Any:
         except* Exception as other:
             unexpected = _collect_exceptions(
                 other,
-                lambda e: not isinstance(
-                    e, (asyncio.CancelledError, UsageLimitExceeded)
+                lambda e: (
+                    not isinstance(e, (asyncio.CancelledError, UsageLimitExceeded))
                 ),
             )
             for exc in unexpected:

tests/plugins/conftest.py

@@ -9,11 +9,23 @@
 def pytest_configure(config):
     """Configure pytest with compatibility workarounds.
 
-    Pre-patch sys.modules to provide a mock ``mcp.types`` during collection.
-    This prevents a ValueError in pydantic's RootModel metaclass when MCP
-    is not installed in the test environment.
+    Pre-patch sys.modules to provide a mock ``mcp.types`` during collection,
+    but only when the real ``mcp`` package is not importable. Previously we
+    checked ``"mcp" not in sys.modules`` which is true on a clean start —
+    that installed MagicMocks for ``mcp.client`` etc. and then, when other
+    tests (e.g. ``tests/agents/test_compaction.py``) transitively imported
+    ``pydantic_ai.mcp``, its ``from mcp.client.sse import sse_client`` blew
+    up with "'mcp.client' is not a package" because the MagicMock had no
+    ``__path__``.
+
+    Real ``mcp`` is installed in this project's dev environment, so the
+    mock path is only needed in bare CI images. Probe with a real import
+    first; only fall back to mocks if that fails.
     """
-    if "mcp" not in sys.modules:
+    try:
+        import mcp  # noqa: F401
+        import mcp.types  # noqa: F401
+    except ImportError:
         mcp_mock = MagicMock()
         mcp_mock.types = MagicMock()
         sys.modules["mcp"] = mcp_mock