The default .netrc file in the home directory is no longer used

[malmans2]

Describe the bug

aiohttp v3.13.1 introduced a breaking change: the default .netrc file in the home directory is no longer used.

The snippet below returns a 401 with the latest version of aiohttp, while it works fine with previous versions.

To Reproduce

Here is my $HOME/.netrc

machine httpbin.org
  login myuser
  password mypassword

MRE:

import aiohttp
import asyncio


async def main():
    url = "https://httpbin.org/basic-auth/myuser/mypassword"

    async with aiohttp.ClientSession(trust_env=True) as session:
        async with session.get(url) as response:
            response.raise_for_status()


asyncio.run(main())

Expected behavior

aiohttp used to read credentials by default from the .netrc file in the home directory.

Logs/tracebacks

---------------------------------------------------------------------------
ClientResponseError                       Traceback (most recent call last)
Cell In[2], line 13
      9         async with session.get(url) as response:
     10             response.raise_for_status()
---> 13 asyncio.run(main())

File ~/miniforge3/envs/test/lib/python3.13/asyncio/runners.py:195, in run(main, debug, loop_factory)
    191     raise RuntimeError(
    192         "asyncio.run() cannot be called from a running event loop")
    194 with Runner(debug=debug, loop_factory=loop_factory) as runner:
--> 195     return runner.run(main)

File ~/miniforge3/envs/test/lib/python3.13/asyncio/runners.py:118, in Runner.run(self, coro, context)
    116 self._interrupt_count = 0
    117 try:
--> 118     return self._loop.run_until_complete(task)
    119 except exceptions.CancelledError:
    120     if self._interrupt_count > 0:

File ~/miniforge3/envs/test/lib/python3.13/asyncio/base_events.py:725, in BaseEventLoop.run_until_complete(self, future)
    722 if not future.done():
    723     raise RuntimeError('Event loop stopped before Future completed.')
--> 725 return future.result()

Cell In[2], line 10, in main()
      8 async with aiohttp.ClientSession(trust_env=True) as session:
      9     async with session.get(url) as response:
---> 10         response.raise_for_status()

File ~/miniforge3/envs/test/lib/python3.13/site-packages/aiohttp/client_reqrep.py:636, in ClientResponse.raise_for_status(self)
    633 if not self._in_context:
    634     self.release()
--> 636 raise ClientResponseError(
    637     self.request_info,
    638     self.history,
    639     status=self.status,
    640     message=self.reason,
    641     headers=self.headers,
    642 )

ClientResponseError: 401, message='UNAUTHORIZED', url='https://httpbin.org/basic-auth/myuser/mypassword'

Python Version

Python 3.13.9

aiohttp Version

Name: aiohttp
Version: 3.13.1
Summary: Async http client/server framework (asyncio)
Home-page: https://github.com/aio-libs/aiohttp
Author:
Author-email:
License: Apache-2.0 AND MIT
Location: /Users/mattia/miniforge3/envs/test/lib/python3.13/site-packages
Requires: aiohappyeyeballs, aiosignal, attrs, frozenlist, multidict, propcache, yarl
Required-by:

multidict Version

Name: multidict
Version: 6.6.3
Summary: multidict implementation
Home-page: https://github.com/aio-libs/multidict
Author: Andrew Svetlov
Author-email: andrew.svetlov@gmail.com
License: Apache License 2.0
Location: /Users/mattia/miniforge3/envs/test/lib/python3.13/site-packages
Requires:
Required-by: aiohttp, yarl

propcache Version

Name: propcache
Version: 0.3.1
Summary: Accelerated property cache
Home-page: https://github.com/aio-libs/propcache
Author: Andrew Svetlov
Author-email: andrew.svetlov@gmail.com
License: Apache-2.0
Location: /Users/mattia/miniforge3/envs/test/lib/python3.13/site-packages
Requires:
Required-by: aiohttp, yarl

yarl Version

Name: yarl
Version: 1.20.1
Summary: Yet another URL library
Home-page: https://github.com/aio-libs/yarl
Author: Andrew Svetlov
Author-email: andrew.svetlov@gmail.com
License: Apache-2.0
Location: /Users/mattia/miniforge3/envs/test/lib/python3.13/site-packages
Requires: idna, multidict, propcache
Required-by: aiohttp

OS

macOS

Related component

Client

Additional context

No response

Code of Conduct

• I agree to follow the aio-libs Code of Conduct

[bdraco]

It must have regressed with #11634

[alexamici]

I confirm I hit the issue and I also note that v3.13.0 works as expected.

[bdraco]

If you set the NETRC environmental variable does the problem go away?

[bdraco]

oh I see the issue. We have to take a performance hit to fix this but it is what it is

[malmans2]

Setting the NETRC variable explicitly works as expected.
The problem is that the default behavior when it's not set changed in v3.13.1

[bdraco]

Right, its a regression. #11714 will fix it

[malmans2]

Awesome, thanks for the quick turnaround!