a2a_mcp peer closed connection without sending complete message body

### What happened?

Using the projects cli tool to test the air ticketing agent, it closes the connection without sending the complete body.

### Relevant log output

```shell
python . --agent http://localhost:10103 ok | 3.13.4 a2a-samples py | 3.12 py
Will use headers: {}
======= Agent Card ========
{"capabilities":{"pushNotifications":true,"stateTransitionHistory":false,"streaming":true},"defaultInputModes":["text","text/plain"],"defaultOutputModes":["text","text/plain"],"description":"Helps book air tickets given a criteria","name":"Air Ticketing Agent","skills":[{"description":"Helps with booking air tickets given a criteria","examples":["Book return tickets from SFO to LHR, starting June 24 2025 and returning 30th June 2025"],"id":"book_air_tickets","name":"Book Air Tickets","tags":["Book air tickets"]}],"url":"http://localhost:10103/","version":"1.0.0"}
========= starting a new task ========

What do you want to send to the agent? (:q or quit to exit): book a flight from SFO
Select a file path to attach? (press enter to skip):
stream event => {"contextId":"395d8b92e6ad44e6a3f07523d1585ea6","history":[{"contextId":"395d8b92e6ad44e6a3f07523d1585ea6","kind":"message","messageId":"c81e9eea-1b07-41f6-860b-c01a5e2a758f","parts":[{"kind":"text","text":"book a flight from SFO"}],"role":"user","taskId":"3bbec46e-bb6a-46f5-a6b9-3efe8fb30505"}],"id":"3bbec46e-bb6a-46f5-a6b9-3efe8fb30505","kind":"task","status":{"state":"submitted"}}
Traceback (most recent call last):
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/httpx/_transports/default.py", line 101, in map_httpcore_exceptions
yield
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/httpx/_transports/default.py", line 271, in __aiter__
async for part in self._httpcore_stream:
yield part
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/httpcore/_async/connection_pool.py", line 407, in __aiter__
raise exc from None
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/httpcore/_async/connection_pool.py", line 403, in __aiter__
async for part in self._stream:
yield part
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/httpcore/_async/http11.py", line 342, in __aiter__
raise exc
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/httpcore/_async/http11.py", line 334, in __aiter__
async for chunk in self._connection._receive_response_body(**kwargs):
yield chunk
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/httpcore/_async/http11.py", line 203, in _receive_response_body
event = await self._receive_event(timeout=timeout)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/httpcore/_async/http11.py", line 213, in _receive_event
with map_exceptions({h11.RemoteProtocolError: RemoteProtocolError}):
~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/opt/homebrew/Cellar/python@3.13/3.13.4/Frameworks/Python.framework/Versions/3.13/lib/python3.13/contextlib.py", line 162, in __exit__
self.gen.throw(value)
~~~~~~~~~~~~~~^^^^^^^
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/httpcore/_exceptions.py", line 14, in map_exceptions
raise to_exc(exc) from exc
httpcore.RemoteProtocolError: peer closed connection without sending complete message body (incomplete chunked read)

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/a2a/client/client.py", line 259, in send_message_streaming
async for sse in event_source.aiter_sse():
yield SendStreamingMessageResponse(**json.loads(sse.data))
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/httpx_sse/_api.py", line 39, in aiter_sse
async for line in self._response.aiter_lines():
...<3 lines>...
yield sse
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/httpx/_models.py", line 1031, in aiter_lines
async for text in self.aiter_text():
for line in decoder.decode(text):
yield line
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/httpx/_models.py", line 1018, in aiter_text
async for byte_content in self.aiter_bytes():
...<2 lines>...
yield chunk
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/httpx/_models.py", line 997, in aiter_bytes
async for raw_bytes in self.aiter_raw():
...<2 lines>...
yield chunk
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/httpx/_models.py", line 1055, in aiter_raw
async for raw_stream_bytes in self.stream:
...<2 lines>...
yield chunk
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/httpx/_client.py", line 176, in __aiter__
async for chunk in self._stream:
yield chunk
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/httpx/_transports/default.py", line 270, in __aiter__
with map_httpcore_exceptions():
~~~~~~~~~~~~~~~~~~~~~~~^^
File "/opt/homebrew/Cellar/python@3.13/3.13.4/Frameworks/Python.framework/Versions/3.13/lib/python3.13/contextlib.py", line 162, in __exit__
self.gen.throw(value)
~~~~~~~~~~~~~~^^^^^^^
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/httpx/_transports/default.py", line 118, in map_httpcore_exceptions
raise mapped_exc(message) from exc
httpx.RemoteProtocolError: peer closed connection without sending complete message body (incomplete chunked read)

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "", line 198, in _run_module_as_main
File "", line 88, in _run_code
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/hosts/cli/__main__.py", line 252, in
asyncio.run(cli())
~~~^^
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/asyncclick/core.py", line 1211, in __call__
return anyio.run(self._main, main, args, kwargs, **opts)
~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/anyio/_core/_eventloop.py", line 74, in run
return async_backend.run(func, args, {}, backend_options)
~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/anyio/_backends/_asyncio.py", line 2310, in run
return runner.run(wrapper())
~~~~~~~~~~^^^^^^^^^^^
File "/opt/homebrew/Cellar/python@3.13/3.13.4/Frameworks/Python.framework/Versions/3.13/lib/python3.13/asyncio/runners.py", line 118, in run
return self._loop.run_until_complete(task)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
File "/opt/homebrew/Cellar/python@3.13/3.13.4/Frameworks/Python.framework/Versions/3.13/lib/python3.13/asyncio/base_events.py", line 725, in run_until_complete
return future.result()
~~~~~~~~~~~~~^^
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/anyio/_backends/_asyncio.py", line 2298, in wrapper
return await func(*args)
^^^^^^^^^^^^^^^^^
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/asyncclick/core.py", line 1214, in _main
return await main(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/asyncclick/core.py", line 1126, in main
rv = await self.invoke(ctx)
^^^^^^^^^^^^^^^^^^^^^^
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/asyncclick/core.py", line 1496, in invoke
return await ctx.invoke(self.callback, **ctx.params)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/asyncclick/core.py", line 829, in invoke
rv = await rv
^^^^^^^^
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/hosts/cli/__main__.py", line 84, in cli
continue_loop, _, taskId = await completeTask(
^^^^^^^^^^^^^^^^^^^
...<7 lines>...
)
^
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/hosts/cli/__main__.py", line 166, in completeTask
async for result in response_stream:
...<13 lines>...
print(f"stream event => {event.model_dump_json(exclude_none=True)}")
File "/Users/greg/Dev/a2a/a2a-samples/samples/python/.venv/lib/python3.13/site-packages/a2a/client/client.py", line 269, in send_message_streaming
raise A2AClientHTTPError(
503, f'Network communication error: {e}'
) from e
a2a.client.errors.A2AClientHTTPError: HTTP Error 503: Network communication error: peer closed connection without sending complete message body (incomplete chunked read)
```

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct