Proxy fails to start on Windows with AttributeError: module 'os' has no attribute 'WNOHANG'.

litellm/proxy/utils.py

@@ -5,6 +5,7 @@
 import json
 import os
 import smtplib
+import sys
 import threading
 import time
 import traceback
@@ -3663,7 +3664,11 @@ def _reap_all_zombies() -> set:
         Returns a set of reaped PIDs.  As PID 1 in Docker (or any
         process that spawns children), we must reap ALL terminated
         children to prevent zombie accumulation.
+
+        No-op on Windows: os.waitpid and os.WNOHANG are Unix-only.
         """
+        if sys.platform == "win32":
+            return set()
         reaped: set = set()
         while True:
             try:
@@ -3684,7 +3689,11 @@ def _try_waitpid_watch(self, pid: int) -> bool:
         via call_soon_threadsafe.
 
         Returns True if the thread was started, False on failure.
+        On Windows, returns False immediately (os.waitpid/WNOHANG are Unix-only);
+        caller falls back to os.kill polling.
         """
+        if sys.platform == "win32":
+            return False
         try:
             probe_pid, _ = os.waitpid(pid, os.WNOHANG)
         except ChildProcessError:

tests/litellm/proxy/test_prisma_engine_watchdog.py

@@ -342,10 +342,25 @@ async def test_stop_watchdog_task_also_stops_engine_watcher(
 
 
 # ---------------------------------------------------------------------------
-# waitpid thread (cross-platform)
+# waitpid thread (Unix only; Windows falls back to os.kill polling)
 # ---------------------------------------------------------------------------
 
 
+def test_try_waitpid_watch_returns_false_on_windows(engine_client):
+    """_try_waitpid_watch returns False on Windows (os.waitpid/WNOHANG unavailable)."""
+    with patch("sys.platform", "win32"):
+        result = engine_client._try_waitpid_watch(1234)
+    assert result is False
+    assert engine_client._engine_wait_thread is None
+
+
+def test_reap_all_zombies_returns_empty_on_windows(engine_client):
+    """_reap_all_zombies returns empty set on Windows (waitpid unavailable)."""
+    with patch("sys.platform", "win32"):
+        reaped = PrismaClient._reap_all_zombies()
+    assert reaped == set()
+
+
 def test_try_waitpid_watch_returns_false_when_not_child(engine_client):
     """_try_waitpid_watch returns False when PID is not our child process."""
     engine_client._engine_pid = 9999