fix: Cancel _target task in AsyncWorker.kill() and improve sync close()

- AsyncWorker.kill() now calls self._task.cancel() before clearing the
  reference, preventing duplicate consumers if submit() is called later
- close() with AsyncHttpTransport now does best-effort sync cleanup
  (kill transport, close components) instead of silently returning
- flush()/close() log warnings instead of debug when async transport used
- Add __aenter__/__aexit__ to _Client for 'async with' support

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: BYK

sentry_sdk/client.py

@@ -1042,11 +1042,13 @@ def close(
             if isinstance(self.transport, AsyncHttpTransport) and hasattr(
                 self.transport, "loop"
             ):
-                logger.debug(
-                    "close() used with AsyncHttpTransport, aborting. Please use close_async() instead."
+                logger.warning(
+                    "close() used with AsyncHttpTransport. "
+                    "Prefer close_async() for graceful async shutdown. "
+                    "Performing synchronous best-effort cleanup."
                 )
-                return
-            self.flush(timeout=timeout, callback=callback)
+            else:
+                self.flush(timeout=timeout, callback=callback)
             self._close_components()
             self.transport.kill()
             self.transport = None
@@ -1092,8 +1094,8 @@ def flush(
             if isinstance(self.transport, AsyncHttpTransport) and hasattr(
                 self.transport, "loop"
             ):
-                logger.debug(
-                    "flush() used with AsyncHttpTransport, aborting. Please use flush_async() instead."
+                logger.warning(
+                    "flush() used with AsyncHttpTransport. Please use flush_async() instead."
                 )
                 return
             if timeout is None:
@@ -1136,6 +1138,12 @@ def __enter__(self) -> "_Client":
     def __exit__(self, exc_type: "Any", exc_value: "Any", tb: "Any") -> None:
         self.close()
 
+    async def __aenter__(self) -> "_Client":
+        return self
+
+    async def __aexit__(self, exc_type: "Any", exc_value: "Any", tb: "Any") -> None:
+        await self.close_async()
+
 
 from typing import TYPE_CHECKING
 

sentry_sdk/worker.py

@@ -213,6 +213,8 @@ def is_alive(self) -> bool:
 
     def kill(self) -> None:
         if self._task:
+            # Cancel the main consumer task to prevent duplicate consumers
+            self._task.cancel()
             if self._queue is not None:
                 try:
                     self._queue.put_nowait(_TERMINATOR)