Error using EchoAgent on windows regarding asyncio

[THZthz]

It seems asyncio only support running the script on unix-like environment? I got OSError: [WinError 6] The handle is invalid running it on windows. Seems the default proactor loop is designed for sockets, not for pipes like standard I/O.

Here is the example output:

(agent-client-protocol-python) PS D:\dev\projects\agent-client-protocol-python> python .\examples\agent.py
Exception in callback _ProactorReadPipeTransport._loop_reading()
handle: <Handle _ProactorReadPipeTransport._loop_reading()>
Traceback (most recent call last):
 File "C:\Users\tanhz1\AppData\Roaming\uv\python\cpython-3.13.7-windows-x86_64-none\Lib\asyncio\proactor_events.py", line 306, in _loop_reading
 self._read_fut = self._loop._proactor.recv_into(self._sock, self._data)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^
 File "C:\Users\tanhz1\AppData\Roaming\uv\python\cpython-3.13.7-windows-x86_64-none\Lib\asyncio\windows_events.py", line 497, in recv_into
 self._register_with_iocp(conn)
 ~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
 File "C:\Users\tanhz1\AppData\Roaming\uv\python\cpython-3.13.7-windows-x86_64-none\Lib\asyncio\windows_events.py", line 710, in _register_with_iocp
 _overlapped.CreateIoCompletionPort(obj.fileno(), self._iocp, 0, 0)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
OSError: [WinError 6] The handle is invalid

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
 File "C:\Users\tanhz1\AppData\Roaming\uv\python\cpython-3.13.7-windows-x86_64-none\Lib\asyncio\events.py", line 89, in _run
 self._context.run(self._callback, *self._args)
 ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "C:\Users\tanhz1\AppData\Roaming\uv\python\cpython-3.13.7-windows-x86_64-none\Lib\asyncio\proactor_events.py", line 316, in _loop_reading
 self._fatal_error(exc, 'Fatal read error on pipe transport')
 ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "C:\Users\tanhz1\AppData\Roaming\uv\python\cpython-3.13.7-windows-x86_64-none\Lib\asyncio\proactor_events.py", line 132, in _fatal_error
 self._force_close(exc)
 ~~~~~~~~~~~~~~~~~^^^^^
 File "C:\Users\tanhz1\AppData\Roaming\uv\python\cpython-3.13.7-windows-x86_64-none\Lib\asyncio\proactor_events.py", line 135, in _force_close
 if self._empty_waiter is not None and not self._empty_waiter.done():
 ^^^^^^^^^^^^^^^^^^
AttributeError: '_ProactorReadPipeTransport' object has no attribute '_empty_waiter'
Traceback (most recent call last):
 File "D:\dev\projects\agent-client-protocol-python\examples\agent.py", line 50, in <module>
 asyncio.run(main())
 ~~~~~~~~~~~^^^^^^^^
 File "C:\Users\tanhz1\AppData\Roaming\uv\python\cpython-3.13.7-windows-x86_64-none\Lib\asyncio\runners.py", line 195, in run
 return runner.run(main)
 ~~~~~~~~~~^^^^^^
 File "C:\Users\tanhz1\AppData\Roaming\uv\python\cpython-3.13.7-windows-x86_64-none\Lib\asyncio\runners.py", line 118, in run
 return self._loop.run_until_complete(task)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
 File "C:\Users\tanhz1\AppData\Roaming\uv\python\cpython-3.13.7-windows-x86_64-none\Lib\asyncio\base_events.py", line 725, in run_until_complete
 return future.result()
 ~~~~~~~~~~~~~^^
 File "D:\dev\projects\agent-client-protocol-python\examples\agent.py", line 42, in main
 reader, writer = await stdio_streams()
 ^^^^^^^^^^^^^^^^^^^^^
 File "D:\dev\projects\agent-client-protocol-python\src\acp\stdio.py", line 46, in stdio_streams
 transport, _ = await loop.connect_write_pipe(lambda: write_protocol, sys.stdout)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "C:\Users\tanhz1\AppData\Roaming\uv\python\cpython-3.13.7-windows-x86_64-none\Lib\asyncio\base_events.py", line 1713, in connect_write_pipe
 transport = self._make_write_pipe_transport(pipe, protocol, waiter)
 File "C:\Users\tanhz1\AppData\Roaming\uv\python\cpython-3.13.7-windows-x86_64-none\Lib\asyncio\proactor_events.py", line 681, in _make_write_pipe_transport
 return _ProactorWritePipeTransport(self,
 sock, protocol, waiter, extra)
 File "C:\Users\tanhz1\AppData\Roaming\uv\python\cpython-3.13.7-windows-x86_64-none\Lib\asyncio\proactor_events.py", line 441, in __init__
 self._read_fut = self._loop._proactor.recv(self._sock, 16)
 ~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^
 File "C:\Users\tanhz1\AppData\Roaming\uv\python\cpython-3.13.7-windows-x86_64-none\Lib\asyncio\windows_events.py", line 484, in recv
 self._register_with_iocp(conn)
 ~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
 File "C:\Users\tanhz1\AppData\Roaming\uv\python\cpython-3.13.7-windows-x86_64-none\Lib\asyncio\windows_events.py", line 710, in _register_with_iocp
 _overlapped.CreateIoCompletionPort(obj.fileno(), self._iocp, 0, 0)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
OSError: [WinError 6] The handle is invalid

Can you fix it? Thanks!

[PsiACE]

Perhaps you might consider trying to run it within WSL? I shall look into it on Windows tomorrow – which ACP client are you using?

[THZthz]

I intend to use it in Zed on Windows (installed by scoop).

[PsiACE]

Hi @THZthz , try replacing the default stdio_streams implementation in echo agent with the following code:

async def stdio_streams() -> tuple[asyncio.StreamReader, asyncio.StreamWriter]:
 """
 Create asyncio StreamReader/StreamWriter from the current process's
 stdin/stdout without blocking the event loop.

 On Windows, avoids using asyncio pipe APIs which are not compatible with stdio.
 """
 if platform.system() == "Windows":
 loop = asyncio.get_running_loop()
 reader = asyncio.StreamReader()
 _ = asyncio.StreamReaderProtocol(reader)

 # Feed stdin from a background thread line-by-line
 def blocking_read() -> None:
 try:
 while True:
 data = sys.stdin.buffer.readline()
 if not data:
 break
 loop.call_soon_threadsafe(reader.feed_data, data)
 finally:
 loop.call_soon_threadsafe(reader.feed_eof)

 import threading
 threading.Thread(target=blocking_read, daemon=True).start()

 # Minimal write-transport wrapping stdout for a real asyncio.StreamWriter
 class _StdoutTransport(asyncio.BaseTransport):
 def __init__(self) -> None:
 self._is_closing = False

 def write(self, data: bytes) -> None: # type: ignore[override]
 if self._is_closing:
 return
 try:
 sys.stdout.buffer.write(data)
 sys.stdout.buffer.flush()
 except Exception:
 # Ignore write errors; reader side will observe EOF
 pass

 def can_write_eof(self) -> bool: # type: ignore[override]
 return False

 def is_closing(self) -> bool: # type: ignore[override]
 return self._is_closing

 def close(self) -> None: # type: ignore[override]
 self._is_closing = True
 try:
 sys.stdout.flush()
 except Exception:
 pass

 def abort(self) -> None: # type: ignore[override]
 self.close()

 def get_extra_info(self, name: str, default=None): # type: ignore[override]
 return default

 write_protocol = _WritePipeProtocol()
 transport = _StdoutTransport()
 writer = asyncio.StreamWriter(transport, write_protocol, None, loop)
 return reader, writer
 else:
 loop = asyncio.get_running_loop()
 reader = asyncio.StreamReader()
 reader_protocol = asyncio.StreamReaderProtocol(reader)
 await loop.connect_read_pipe(lambda: reader_protocol, sys.stdin)
 write_protocol = _WritePipeProtocol()
 transport, _ = await loop.connect_write_pipe(lambda: write_protocol, sys.stdout)
 writer = asyncio.StreamWriter(transport, write_protocol, None, loop)
 return reader, writer

If it works fine, I'll treat it as a patch or update it in the documentation.

[THZthz]

No... Something is wrong since I got no response from the agent. When running the duet, I can see no response from the agent too.

[PsiACE]

No... Something is wrong since I got no response from the agent. When running the duet, I can see no response from the agent too.

Could you show me the screenshot?