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uvx can't find executables on Windows when the package name contains a "." #15165

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#15300
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uvx can't find executables on Windows when the package name contains a "."#15165
#15300
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bugSomething isn't workinghelp wantedContribution especially encouraged
@crh23

Description

@crh23
crh23
opened on Aug 8, 2025

Summary

Running (for example) uvx awslabs.cdk-mcp-server@latest on Windows will produce the error

error: Failed to spawn: `awslabs.cdk-mcp-server`
  Caused by: program not found

This can be worked around by running uvx --from awslabs.cdk-mcp-server@latest awslabs.cdk-mcp-server.exe, indicating that uv is not correctly finding the Windows executable.

I believe this is due to the extension guessing implementation found in

uv/crates/uv-shell/src/runnable.rs

Lines 73 to 100 in 57df014

pub fn from_script_path(script_path: &Path, runnable_name: &OsStr) -> Command {
let script_path = script_path.join(runnable_name);
// Honor explicit extension if provided and recognized.
if let Some(script_type) = script_path
.extension()
.and_then(OsStr::to_str)
.and_then(Self::from_extension)
.filter(|_| script_path.is_file())
{
return script_type.as_command(&script_path);
}
// Guess the extension when an explicit one is not provided.
// We also add the extension when missing since for some types (e.g. PowerShell) it must be explicit.
Self::all()
.iter()
.map(|script_type| {
(
script_type,
script_path.with_extension(script_type.to_extension()),
)
})
.find(|(_, script_path)| script_path.is_file())
.map(|(script_type, script_path)| script_type.as_command(&script_path))
.unwrap_or_else(|| Command::new(runnable_name))
}
}

since

script_path.with_extension(script_type.to_extension())

will replace the "extension" found after the "." of the original script name, so instead of searching for awslabs.cdk-mcp-server.exe it will search for awslabs.exe (see the examples for with_extension).

Platform

Windows 11 x86_64

Version

uv 0.8.0 (0b23572 2025-07-17)

Python version

Python 3.12.1

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