[BUG] Claude will not use /bin/ash on Alpine

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?

In alpine linux, with the shell /bin/ash, claude code will always give this kind of error:

Bash(xxxxx)
  ⎿  Error: No suitable shell found. Claude CLI requires a Posix shell environment. Please ensure you have a valid shell installed and the SHELL environment variable set.

As far as I know ash is POSIX compliant, and I can confirm that it is properly installed and set in the $SHELL variable:

$ env | grep SHELL 
   SHELL=/bin/ash

$ /bin/ash --help
   BusyBox v1.36.1 (2024-06-10 07:11:47 UTC) multi-call binary.

   Usage: ash [-il] [-|+Cabefmnuvx] [-|+o OPT]... [-c 'SCRIPT' [ARG0 ARGS] | FILE ARGS | -s ARGS]

   Unix shell interpreter

What Should Happen?

Expected Claude to pick /bin/ash as specified in the SHELL env variable.

Error Messages/Logs

Error: No suitable shell found. Claude CLI requires a Posix shell environment. Please ensure you have a valid shell installed and the SHELL environment variable set.

Steps to Reproduce

1. Install claude in a alpine environment, without bash install
2. Run claude and get it to use a bash command

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

1.0.127

Platform

Anthropic API

Operating System

Other Linux

Terminal/Shell

Other

Additional Information

_No response_