[BUG] a POSIX shell is required, but bash is invoked instead

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?

Claude indicates that it requires a POSIX shell, but it then tries to explicitly use bash instead.

This fails when there is a POSIX shell installed, but bash is not installed.

Even if SHELL=/bin/sh is defined, claude still attempts to use bash instead.

What Should Happen?

/bin/sh should be used. $SHELL should be invoked directly, not through bash.

Error Messages/Logs

● Bash(cargo check)
  ⎿  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.

● Let me try with shell explicitly set to sh:

● Bash(SHELL=/bin/sh cargo check)
  ⎿  Running…

Steps to Reproduce

Run any command without installing bash first.

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

1.0.115 (Claude Code)

Platform

Anthropic API

Operating System

Other Linux

Terminal/Shell

Other

Additional Information

_No response_