[non-deterministic] is_client_connected() crashes with KeyError: '_pydevd_bundle.pydevd_comm_constants'

[francescomikulis]

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Environment data

• debugpy version: 1.8.20
• OS and version: macOS 26.3 + uv / .venv
• Python version: 3.13
• Using Cursor

Actual behavior

Crash during parallel testing on github runner (using pytest xdist) - the code calls:

is_client_connected()

Backtrace:

../../../.venv/lib/python3.13/site-packages/debugpy/public_api.py:44: in wrapper
    from debugpy.server import api
../../../.venv/lib/python3.13/site-packages/debugpy/server/__init__.py:7: in <module>
    import debugpy._vendored.force_pydevd  # noqa
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
../../../.venv/lib/python3.13/site-packages/debugpy/_vendored/force_pydevd.py:44: in <module>
    preimport('pydevd', [
../../../.venv/lib/python3.13/site-packages/debugpy/_vendored/__init__.py:126: in preimport
    import_module(name)
/home/runner/.local/share/uv/python/cpython-3.13.11-linux-x86_64-gnu/lib/python3.13/importlib/__init__.py:88: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
../../../.venv/lib/python3.13/site-packages/debugpy/_vendored/pydevd/pydevd.py:39: in <module>
    import pydevd_file_utils
../../../.venv/lib/python3.13/site-packages/debugpy/_vendored/pydevd/pydevd_file_utils.py:47: in <module>
    from _pydevd_bundle.pydevd_comm_constants import file_system_encoding, filesystem_encoding_is_utf8
<frozen importlib._bootstrap>:1360: in _find_and_load
    ???
<frozen importlib._bootstrap>:1331: in _find_and_load_unlocked
    ???
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

spec = ModuleSpec(name='_pydevd_bundle.pydevd_comm_constants', loader=<_frozen_importlib_external.SourceFileLoader object at ...venv/lib/python3.13/site-packages/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_comm_constants.py')

>   ???
E   KeyError: '_pydevd_bundle.pydevd_comm_constants'

<frozen importlib._bootstrap>:946: KeyError

Expected behavior

No crash.

Steps to reproduce:

Unable to reproduce.

[rchiodo]

Thanks for the issue. Without a reproduction it'd be hard to diagnose though. The callstack doesn't make much sense to me. How can the loader have a key error?

[francescomikulis]

Unfortunately the setup to reproduce this is complex.
I'm using pytest-xdist with async tests.
A function I call during the test, within an async context, and potentially many times in parallel (one per process) is:

debugpy_is_client_connected()

I'm using a .venv generated by uv.

Also, this just happened again, this time with a different key error:

..[my private code]..
    and not debugpy_is_client_connected()
../../../.venv/lib/python3.13/site-packages/debugpy/public_api.py:44: in wrapper
    from debugpy.server import api
../../../.venv/lib/python3.13/site-packages/debugpy/server/__init__.py:7: in <module>
    import debugpy._vendored.force_pydevd  # noqa
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
../../../.venv/lib/python3.13/site-packages/debugpy/_vendored/force_pydevd.py:44: in <module>
    preimport('pydevd', [
../../../.venv/lib/python3.13/site-packages/debugpy/_vendored/__init__.py:126: in preimport
    import_module(name)
/home/runner/.local/share/uv/python/cpython-3.13.11-linux-x86_64-gnu/lib/python3.13/importlib/__init__.py:88: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
../../../.venv/lib/python3.13/site-packages/debugpy/_vendored/pydevd/pydevd.py:51: in <module>
    from _pydev_bundle.pydev_console_utils import DebugConsoleStdIn
<frozen importlib._bootstrap>:1360: in _find_and_load
    ???
<frozen importlib._bootstrap>:1331: in _find_and_load_unlocked
    ???
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

spec = ModuleSpec(name='_pydev_bundle.pydev_console_utils', loader=<_frozen_importlib_external.SourceFileLoader object at ../.venv/lib/python3.13/site-packages/debugpy/_vendored/pydevd/_pydev_bundle/pydev_console_utils.py')

>   ???
E   KeyError: '_pydev_bundle.pydev_console_utils'

<frozen importlib._bootstrap>:946: KeyError

[francescomikulis]

Unfortunately the setup to reproduce this is complex.
I'm using pytest-xdist with async tests.
A function I call during the test, within an async context, and potentially many times in parallel (one per process) is:
debugpy_is_client_connected()
I'm using a .venv generated by uv.

@rchiodo is the above enough background?

[rchiodo]

I'd need tests that reproduce it. That's not enough for me to figure out where the problem is. Otherwise my guess is that the debugpy module is getting loaded from the wrong path and it can't find the matching pydevd.