Bash/PowerShell tool fails instantly on Windows — exit code 1, zero stdout/stderr, every command

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Every command run through the shell tool fails immediately with exit code 1 and completely empty output (no stdout, no stderr) — including trivial ones like Write-Output "hello" or exit 0. PowerShell itself is confirmed healthy on the machine: the exact same commands run fine when typed manually in a real terminal window, including with -NonInteractive -NoProfile flags that mimic non-interactive invocation. The failure appears to be specific to how the app's own process spawns the child shell, not to PowerShell, execution policy, or the command content.

What Should Happen?

The shell tool should execute the given command in PowerShell and return its actual stdout/stderr/exit code, matching what running the same command manually produces.

Error Messages/Logs

Tool reports only: "Exit code 1" — no stdout, no stderr, no further diagnostic detail is surfaced by the tool for any command, regardless of content.

Steps to Reproduce

1. On Windows 11, open a Claude Code session (desktop app, Code tab).
2. Run any shell command, e.g. Write-Output "hello".
3. Observe: tool reports "Exit code 1" with no stdout/stderr, regardless of command content.
4. Confirm PowerShell itself is fine by opening a normal terminal (Win+X → Terminal) and running the identical command directly — it succeeds.
5. Confirm non-interactive invocation also works outside the app: powershell.exe -NonInteractive -NoProfile -Command "Write-Output 'hello'" succeeds when run manually.

What we ruled out:

• Execution policy: Get-ExecutionPolicy -List shows Bypass at LocalMachine, all other scopes Undefined — not a policy block.
• Sandbox flag: fails identically with the tool's sandbox-disable option on or off.
• Execution mode: fails identically in foreground and background modes.
• App state: persisted through full app restart, full uninstall/reinstall, and full machine reboot.
• Security software: personal (non-managed) device, Smart App Control off, no third-party AV/EDR beyond built-in Windows Defender.
• Working directory: confirmed accessible — file tools (Read/Write/Edit/Glob/Grep) work fine; only process execution fails.

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Windows 11 Home 10.0.26200

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_