Windows: yarn/npm commands produce no output in Bash tool

Description

On Windows, running yarn or npm commands via the Bash tool returns immediately with no output. The commands execute (or appear to), but stdout/stderr are not captured.

Environment

• Platform: Windows (win32)
• Shell: Git Bash (MINGW64)
• Yarn version: 1.22.19

Steps to Reproduce

1. Run any yarn command via the Bash tool:

yarn --version

Result: (No content) or Tool ran without output or errors

1. Run npm commands:

npm --version

Result: Same - no output

Expected Behavior

Should return the version number (e.g., 1.22.19 for yarn)

Actual Behavior

Returns immediately with no output captured.

Workaround

Wrapping yarn/npm commands in node's child_process works:

node -e "const {execSync} = require('child_process'); console.log(execSync('yarn --version', {encoding: 'utf8', stdio: 'pipe'}))"

This correctly outputs: 1.22.19

Additional Context

• Other bash commands work fine (ls, pwd, which yarn, etc.)
• node -e "console.log('test')" works fine
• This was working a few days ago, suggesting a regression
• The issue appears specific to how yarn/npm handle their output streams on Windows when not attached to a TTY