diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 643403f..8b80583 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -201,6 +201,13 @@ jobs:
     needs: [lint, changes]
     if: needs.changes.outputs.python == 'true' || github.event_name == 'push'
     runs-on: ${{ matrix.os }}
+    env:
+      # setup-python on macOS upgrades certifi via pip; pip's HTTP cache
+      # occasionally fails to deserialize across runner image versions and
+      # surfaces as a noisy "Cache entry deserialization failed" annotation.
+      # Disabling pip's cache eliminates the warning at zero cost (we use uv
+      # for actual package installs).
+      PIP_NO_CACHE_DIR: "1"
     strategy:
       matrix:
         os: [ubuntu-latest]
@@ -247,26 +254,10 @@ jobs:
           args: --release --features extension-module,postgres,redis,native-async,workflows
 
       - name: Run Python test suite
-        run: |
-          set +e
-          uv run python -m pytest tests/python/ -v --junitxml=test-results.xml
-          PYTEST_EXIT=$?
-          if [ $PYTEST_EXIT -eq 0 ]; then exit 0; fi
-          # SIGABRT (134) during interpreter shutdown is a known PyO3 issue;
-          # check junit XML to confirm all tests actually passed.
-          if [ $PYTEST_EXIT -eq 134 ] && [ -f test-results.xml ]; then
-            FAILURES=$(python -c "
-          import xml.etree.ElementTree as ET
-          r = ET.parse('test-results.xml').getroot()
-          print(int(r.get('failures',0)) + int(r.get('errors',0)))
-          ")
-            if [ "$FAILURES" = "0" ]; then
-              echo "::warning::Tests passed but process crashed during cleanup (known PyO3 issue)"
-              exit 0
-            fi
-          fi
-          exit $PYTEST_EXIT
-        shell: bash
+        # The pytest_unconfigure hook in tests/python/conftest.py calls
+        # ``os._exit(0)`` on a clean run to bypass CPython finalization and
+        # avoid the PyO3 daemon-thread SIGABRT we used to paper over here.
+        run: uv run python -m pytest tests/python/ -v --junitxml=test-results.xml
 
   ci-status:
     name: CI status
diff --git a/tests/python/conftest.py b/tests/python/conftest.py
index 5042703..2d82fd7 100644
--- a/tests/python/conftest.py
+++ b/tests/python/conftest.py
@@ -1,5 +1,7 @@
 """Shared fixtures for taskito tests."""
 
+import os
+import sys
 import threading
 from collections.abc import Generator
 from pathlib import Path
@@ -24,3 +26,34 @@ def run_worker(queue: Queue) -> Generator[threading.Thread]:
     yield thread
     queue._inner.request_shutdown()
     thread.join(timeout=5)
+
+
+_PYTEST_EXIT_STATUS: int = 0
+
+
+def pytest_sessionfinish(session: pytest.Session, exitstatus: int) -> None:
+    """Capture the exit status for ``pytest_unconfigure`` to act on."""
+    global _PYTEST_EXIT_STATUS
+    _PYTEST_EXIT_STATUS = int(exitstatus)
+
+
+def pytest_unconfigure(config: pytest.Config) -> None:
+    """Bypass CPython's interpreter finalization on a clean exit.
+
+    Many tests leave PyO3-backed daemon threads (heartbeat, async executor,
+    webhook delivery, distributed-lock extender) running at process end.
+    During ``Py_Finalize`` those threads may try to (re)acquire the GIL after
+    it has been torn down, producing ``FATAL: exception not rethrown`` and a
+    SIGABRT — even though every test passed. ``os._exit`` skips finalization
+    entirely after the terminal summary and junit XML are already written,
+    eliminating the spurious crash.
+
+    ``pytest_unconfigure`` fires after every other hook (terminal summary,
+    junitxml plugin, etc.), so output and side effects are preserved. We
+    skip the bypass on failure so pytest's normal traceback machinery still
+    runs.
+    """
+    if _PYTEST_EXIT_STATUS == 0:
+        sys.stdout.flush()
+        sys.stderr.flush()
+        os._exit(0)