Popup windows "Making stdin/stdout/stderr inheritable failed" when when running a gui-script on Windows

[deffi]

Summary

When using uv run or uv tool run to run a script from [project.gui-scripts] in pyproject.toml, 3 popup messages are displayed before the script is started:

• "Making stdin inheritable failed"
• "Making stdout inheritable failed"
• "Making stderr inheritable failed"

This is regardless of whether the script is doing anything GUI related or not.

To reproduce

Preparation:

• uv init --app --package foo
• In pyproject.toml, replace [project.scripts] with [project.gui-scripts]

Issue demonstration, in foo/:

• uv run foo → popup messages
• uv tool run --from . foo → popup messages

On the other hand, this works as expected:

• .venv\Scripts\foo.exe → no popups
• uv tool install . & foo → no popups

Output from uv --verbose run foo:

Output

DEBUG uv 0.5.20 (1c17662b3 2025-01-15)
DEBUG Found project root: `c:\Users\[...]\foo`
DEBUG No workspace root found, using project root
DEBUG Discovered project `foo` at: c:\Users\[...]\foo
DEBUG Reading Python requests from version file at `c:\Users\[...]\foo\.python-version`
DEBUG Using Python request `3.13` from version file at `.python-version`
DEBUG The virtual environment's Python version satisfies `3.13`
DEBUG Using request timeout of 30s
DEBUG Found static `pyproject.toml` for: foo @ file:///C:/Users/[...]/foo
DEBUG No workspace root found, using project root
DEBUG Existing `uv.lock` satisfies workspace requirements
Resolved 1 package in 10ms
DEBUG Using request timeout of 30s
DEBUG Requirement already installed: foo==0.1.0 (from file:///C:/Users/[...]/foo)
Audited 1 package in 0.49ms
DEBUG Using Python 3.13.1 interpreter at: C:\Users\[...]\foo\.venv\Scripts\python.exe
DEBUG Running `foo`
DEBUG Command exited with code: 0

Additional information

For scripts in [project.scripts] (as opposed to [project.gui-scripts]), this does not happen.

The message seems to be generated by the spawn_child function in uv-trampoline's bounce.rs.

Redirecting the output changes the behavior slightly:

• uv run foo >1.txt → popups only for "stdin" and "stderr", output of foo in 1.txt
• uv run foo 2>2.txt → no popups, messages written to 2.txt instead

Versions

Windows 11 Version 23H2 (Build 22631.4460)
uv 0.5.20 (1c17662 2025-01-15)