test(mcp): compare the installed SDK against the pyproject pin for every 2.0-only file

Move the require_mcp_2_sdk fixture from tests/tools/conftest.py to the root
tests/conftest.py so tests/test_mcp_serve.py can use it too, and read the
required version from the `mcp==X` pin in pyproject's [mcp] extra instead of
a hardcoded "2.0.0" — the pin moves, the guard follows.

Sharpen the remaining presence-only guards named in the issue that still went
red under an installed-but-older SDK on current main: tests/test_mcp_serve.py
(the mcp_server_e2e fixture and TestServerCreation asserted `mcp.server.MCPServer`,
absent in 1.x) and tests/tools/test_mcp_oauth.py::TestCallbackPortReservation
(2.0 AuthorizationCodeResult vs the 1.x tuple). test_mcp_oauth_manager.py and
test_mcp_device_flow.py already pass under 1.28.1 on current main, so they are
left alone; PR #114068's importorskip hunks in those files do not overlap these
edits.

tests/conftest.py

@@ -1266,6 +1266,40 @@ def _relocate_basetemp_outside_operator_home(config) -> None:
     config.option.basetemp = str(safe)
 
 
+def _pinned_mcp_sdk_version() -> str:
+    """The ``mcp==X`` pin carried by the ``[mcp]`` extra in pyproject.toml."""
+    import tomllib
+
+    with open(Path(__file__).resolve().parent.parent / "pyproject.toml", "rb") as fh:
+        extras = tomllib.load(fh)["project"]["optional-dependencies"]
+    for req in extras["mcp"]:
+        if req.startswith("mcp=="):
+            return req.split("==", 1)[1].strip()
+    raise RuntimeError("pyproject.toml [mcp] extra no longer pins mcp==X")
+
+
+@pytest.fixture
+def require_mcp_2_sdk():
+    """Skip tests that pin mcp 2.0-only behaviour when an older SDK is installed.
+
+    The runtime deliberately supports both SDK generations (the dual streamable-client probe in
+    mcp_tool), so a stale ``mcp`` distribution imports fine and presence-only guards let these
+    tests through — where they fail later with opaque SDK errors. Compare the installed
+    distribution against the pin so the outcome is an explicit skip with an actionable reason.
+    """
+    from importlib.metadata import PackageNotFoundError, version as dist_version
+
+    from packaging.version import Version
+
+    pinned = _pinned_mcp_sdk_version()
+    try:
+        found = dist_version("mcp")
+    except PackageNotFoundError:
+        pytest.skip(f"requires mcp=={pinned} (not installed); install the [mcp] extra")
+    if Version(found) < Version(pinned):
+        pytest.skip(f"requires mcp=={pinned} (found {found}); install the [mcp] extra")
+
+
 @pytest.hookimpl(trylast=True)  # after _pytest.tmpdir has built config._tmp_path_factory
 def pytest_configure(config):  # noqa: D401 — pytest hook
     """Register markers used by hermetic conftest."""

tests/test_mcp_serve.py

@@ -522,9 +522,8 @@ class TestEventBridge:
 # ---------------------------------------------------------------------------
 
 @pytest.fixture
-def mcp_server_e2e(populated_sessions_dir, mock_session_db, monkeypatch):
-    """Create a fully wired MCP server for E2E testing."""
-    mcp = pytest.importorskip("mcp", reason="MCP SDK not installed")
+def mcp_server_e2e(populated_sessions_dir, mock_session_db, monkeypatch, require_mcp_2_sdk):
+    """Create a fully wired MCP server for E2E testing (pinned SDK: 1.x lacks mcp.server.MCPServer)."""
     import mcp_serve
     monkeypatch.setattr(mcp_serve, "_get_sessions_dir", lambda: populated_sessions_dir)
     monkeypatch.setattr(mcp_serve, "_get_session_db", lambda: mock_session_db)
@@ -987,14 +986,14 @@ class TestToolRegistration:
 # ---------------------------------------------------------------------------
 
 class TestServerCreation:
+    @pytest.mark.usefixtures("require_mcp_2_sdk")
     def test_create_server(self, populated_sessions_dir, monkeypatch):
-        pytest.importorskip("mcp", reason="MCP SDK not installed")
         import mcp_serve
         monkeypatch.setattr(mcp_serve, "_get_sessions_dir", lambda: populated_sessions_dir)
         assert mcp_serve.create_mcp_server() is not None
 
+    @pytest.mark.usefixtures("require_mcp_2_sdk")
     def test_create_with_bridge(self, populated_sessions_dir, monkeypatch):
-        pytest.importorskip("mcp", reason="MCP SDK not installed")
         import mcp_serve
         monkeypatch.setattr(mcp_serve, "_get_sessions_dir", lambda: populated_sessions_dir)
         bridge = mcp_serve.EventBridge()

tests/tools/conftest.py

@@ -55,29 +55,6 @@ def _materialize_mcp_sdk_symbols():
     yield
 
 
-@pytest.fixture
-def require_mcp_2_sdk():
-    """Skip tests that pin mcp 2.0-only behaviour when an older SDK is installed.
-
-    The runtime deliberately supports both SDK generations (the dual
-    streamable-client probe in mcp_tool), so a stale ``mcp`` distribution
-    imports fine and presence-only guards let these tests through — where
-    they fail later with opaque SDK errors. Compare the installed
-    distribution against the 2.0.0 pin carried by the ``[mcp]`` extra so the
-    outcome is an explicit skip with an actionable reason.
-    """
-    from importlib.metadata import PackageNotFoundError, version as dist_version
-
-    from packaging.version import Version
-
-    try:
-        found = dist_version("mcp")
-    except PackageNotFoundError:
-        pytest.skip("mcp SDK not installed; install the [mcp] extra")
-    if Version(found) < Version("2.0.0"):
-        pytest.skip(f"requires mcp>=2.0.0 (found {found}); install the [mcp] extra")
-
-
 @pytest.fixture(autouse=True)
 def _clear_web_result_cache():
     """Reset the web_search TTL memo between tests.

tests/tools/test_mcp_oauth.py

@@ -543,6 +543,7 @@ class TestCallbackHandlerErrorEscaping:
 # TOCTOU port reservation (#22161)
 # ---------------------------------------------------------------------------
 
+@pytest.mark.usefixtures("require_mcp_2_sdk")
 class TestCallbackPortReservation:
     """The socket picked at selection time stays bound until callback bind.