[BUG] exclamation mark corrupted in shell calls

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?

When using the shell tools, "!" characters are replaced with "\\!", which obviously completely breaks actual shell usage.

This already been reported, but closed without fixing it. I'm pretty sure Claude Code can fix this bug autonomously and correctly, so not sure what you are waiting for to fix it. Please fix ASAP.

Claude says:

  In the Claude Code Bash tool, every ! character in a command is backslash-escaped to \! before the command
  reaches bash. This is not limited to the leading negation operator — it affects ! in any position. Depending on
  context the escaping either breaks the command (reserved word, indirect expansion) or silently corrupts output
  (literal ! inside quotes). It only survives where shell unescaping happens to restore it (unquoted arguments, [
  ]/test/find predicates).

What Should Happen?

It should obviously be passed through without mucking with it.

Error Messages/Logs

Steps to Reproduce

Claude says (after testing it itself):

Run each of the following through the Claude Code Bash tool (a non-interactive bash invocation) and compare the actual output to the expected:

  1. Negation reserved word (leading):
  ! false; echo "exit=$?"
    - Expected: exit=0
    - Actual: /bin/bash: line 1: !: command not found then exit=127
  2. Negation in other positions:
  true && ! false; echo "exit=$?"
  echo hi; ! false; echo "exit=$?"
  if ! false; then echo ok; fi
    - Expected: negation evaluates normally (exit=0, prints ok)
    - Actual: each prints !: command not found, exit 127
  3. Indirect parameter expansion:
  v=PATH; echo "${!v}"
    - Expected: the value of $PATH
    - Actual: bash: ${\!v}: bad substitution
  4. Literal ! inside quotes (output corruption):
  echo "hello world!"
  echo 'single: hi!'
    - Expected: hello world! and single: hi!
    - Actual: hello world\! and single: hi\! (stray backslash)
  5. Confirm the root cause — inspect the bytes bash actually receives:
  printf '%s' "x!y" | cat -A
    - Expected: x!y
    - Actual: x\!y (every ! has been rewritten to \! before execution)
  6. Confirm history expansion is already off (so the escaping is unnecessary):
  shopt -po histexpand
    - Output: set +o histexpand

  Contrast — cases that work (the shell strips the backslash during normal unescaping), showing the bug is the
  escaping itself, not the ! semantics:
  echo unquoted_abc!def          # prints abc!def correctly
  find . -maxdepth 1 ! -name .   # works
  [ ! -e /nonexistent ] && echo ok   # works
  [ a != b ] && echo ok              # works

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.168 (Claude Code)

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_