fix: prevent /copy crash on Windows by skipping /dev/tty

[ManojINaik]

On Windows, the pickTty() function attempted to open /dev/tty which doesn't exist, causing an ENOENT error ('C:\dev\tty'). This caused the CLI to crash when users ran the /copy command.

The fix adds a platform check to skip /dev/tty on Windows and fall back to stderr/stdout or clipboardy for clipboard operations.

Fixes #15648
Fixes #15567

Summary

Fix CLI crash on Windows when using /copy command. The pickTty() function attempted to open /dev/tty (Unix-only) which caused an unhandled ENOENT error on Windows.

Details

Root Cause: On Windows, Node.js interprets /dev/tty as C:\dev\tty, which doesn't exist. The fs.createWriteStream() call doesn't throw synchronously - it emits an async 'error' event that was unhandled.

Solution: Added process.platform !== 'win32' check before attempting /dev/tty. On Windows:

• Falls back to stderr/stdout if TTY available (for SSH sessions)
• Falls back to clipboardy library for native Windows clipboard

Files Changed:

• packages/cli/src/ui/utils/commandUtils.ts - Added platform check in pickTty()
• packages/cli/src/ui/utils/commandUtils.test.ts - Added 2 Windows-specific tests

Related Issues

Fixes #15648 - CLI crashes on Windows when using /copy (Error: ENOENT 'C:\dev\tty')
Fixes #15567 - [Bug] Windows crash when using /copy: Error: ENOENT: no such file or directory
Fixes #15660
Fixes #15667
Fixes #15920

How to Validate

1. Run tests: cd packages/cli && npx vitest run src/ui/utils/commandUtils.test.ts
2. Verify all 24 tests pass including:
   • skips /dev/tty on Windows and uses stderr fallback for OSC-52
   • uses clipboardy on native Windows without SSH/WSL
3. On Windows: Run gemini, generate a response, run /copy, verify no crash and content is copied

Pre-Merge Checklist

• Updated relevant documentation and README (if needed)
• Added/updated tests (if needed)
• Noted breaking changes (if any)
• Validated on required platforms/methods:
  • MacOS
    • npm run
    • npx
    • Docker
    • Podman
    • Seatbelt
  • Windows
    • npm run
    • npx
    • Docker
  • Linux
    • npm run
    • npx
    • Docker

[gemini-code-assist]

Summary of Changes

Hello @ManojINaik, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a critical bug that caused the CLI to crash on Windows when users attempted to use the /copy command. The issue stemmed from an attempt to access /dev/tty, a Unix-specific device, on Windows systems. The changes introduce a robust platform check, ensuring that the CLI gracefully handles clipboard operations on Windows by falling back to appropriate mechanisms like stderr/stdout for SSH sessions or the clipboardy library for native environments, thereby significantly improving the application's stability and user experience on the Windows platform.

Highlights

• Windows Crash Fix: Prevented a CLI crash on Windows that occurred when using the /copy command, which was caused by an attempt to open /dev/tty.
• Platform-Specific TTY Handling: Implemented a platform check (process.platform !== 'win32') in the pickTty() function to explicitly skip /dev/tty on Windows systems.
• Clipboard Fallback Logic: Ensured that on Windows, the CLI now correctly falls back to stderr/stdout for OSC-52 in SSH sessions or utilizes the clipboardy library for native Windows clipboard operations.
• New Test Cases: Added two new Windows-specific test cases to commandUtils.test.ts to validate the correct behavior of TTY and clipboard handling on the Windows platform.

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[gemini-code-assist]

Code Review

This pull request fixes a crash on Windows when using the /copy command by avoiding an attempt to access /dev/tty. The change is correct and includes relevant tests. My review includes two suggestions: one to improve test isolation to prevent flaky tests, and another to enhance the robustness of error handling for fs.createWriteStream on non-Windows platforms to prevent potential crashes, building upon the insight from the PR description.

[jackwotherspoon]

nits

[jackwotherspoon]

I have verified this fix works on my Windows machine. Once builds pass will merge.

Thanks for this @ManojINaik 👏