diff --git a/tests/conftest.py b/tests/conftest.py
index 2da7d4a1eb..468926b0f5 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -534,6 +534,14 @@ def pytest_configure(config):  # noqa: D401 — pytest hook
         "behaviour — e.g. PTY tests that signal their own child).",
     )
 
+    # The pyproject addopts pin ``--timeout-method=signal`` relies on
+    # ``signal.SIGALRM``, which does not exist on Windows — pytest-timeout
+    # raises AttributeError at timer setup and the whole run aborts before any
+    # test executes. Fall back to the thread-based timer on Windows so the
+    # suite runs natively there (POSIX keeps the more reliable signal method).
+    if sys.platform == "win32" and getattr(config.option, "timeout_method", None) == "signal":
+        config.option.timeout_method = "thread"
+
 
 @pytest.fixture(autouse=True)
 def _live_system_guard(request, monkeypatch):