fix(tools): spawn daemon workers with the 3.14 worker context

tests/tools/test_daemon_pool.py

@@ -45,6 +45,22 @@ def _init(tag):
         pool.shutdown(wait=True)
 
 
+def test_worker_args_match_stdlib_worker_signature():
+    """CPython changes _worker's signature between versions (3.14 moved
+    initializer/initargs into a worker context), so the mirrored spawn
+    path must adapt instead of passing a stale argument tuple."""
+    import inspect
+    import weakref
+    from concurrent.futures.thread import _worker
+
+    expected = len(inspect.signature(_worker).parameters)
+    pool = DaemonThreadPoolExecutor(max_workers=1)
+    try:
+        assert len(pool._worker_args(weakref.ref(pool))) == expected
+    finally:
+        pool.shutdown(wait=True)
+
+
 def test_idle_worker_reuse():
     pool = DaemonThreadPoolExecutor(max_workers=4)
     try:

tools/daemon_pool.py

@@ -38,7 +38,7 @@ class DaemonThreadPoolExecutor(ThreadPoolExecutor):
     """ThreadPoolExecutor variant whose workers do not block process exit."""
 
     def _adjust_thread_count(self) -> None:
-        # Mirrors CPython's implementation (3.8–3.13) with two changes:
+        # Mirrors CPython's implementation (3.8–3.14) with two changes:
         # daemon=True and no _threads_queues registration.
         if self._idle_semaphore.acquire(timeout=0):
             return
@@ -52,13 +52,22 @@ def weakref_cb(_, q=self._work_queue):
             t = threading.Thread(
                 name=thread_name,
                 target=_worker,
-                args=(
-                    weakref.ref(self, weakref_cb),
-                    self._work_queue,
-                    self._initializer,
-                    self._initargs,
-                ),
+                args=self._worker_args(weakref.ref(self, weakref_cb)),
                 daemon=True,
             )
             t.start()
             self._threads.add(t)
+
+    def _worker_args(self, executor_ref: weakref.ref) -> tuple:
+        # CPython 3.14 replaced the (queue, initializer, initargs) worker
+        # arguments with a per-worker context object built by the executor,
+        # so reading self._initializer there raises AttributeError.
+        create_context = getattr(self, "_create_worker_context", None)
+        if create_context is not None:
+            return (executor_ref, create_context(), self._work_queue)
+        return (
+            executor_ref,
+            self._work_queue,
+            self._initializer,
+            self._initargs,
+        )