Issue Station
Sign In
Tools hereToolbox

claude-code - 💡(How to fix) Fix Bash tool hook rewrites \!= to \\!= in command text, breaking inline Python comparisons [1 comments, 2 participants]

Official PRs (…)
ON THIS PAGE

Recommended Tools

×6

Utilities matched from this issue’s tags and category — try them while you read without losing context.

GitHub issue graph ai analysis

Paste a GitHub issue URL. We fetch that issue, discover linked issues from bodies/comments/timeline, collect linked pull requests, and produce a structured English report.

The report is written in English Markdown for sharing and archival.

Helpful · Quick feedback

Loading…
GitHub stats
anthropics/claude-code#52850•Fetched 2026-04-25 06:19:13
View on GitHub
Comments
1
Participants
2
Timeline
6
Reactions
0
Author
masahiroono36masahiroono36
Participants
github-actions[bot]github-actions[bot]masahiroono36masahiroono36
Timeline (top)
labeled ×5commented ×1

The Claude Code user-prompt-submit-hook (or an equivalent pre-execution transform) rewrites \!= to \\!= inside Bash tool command text. When a command embeds Python code inline via python3 -c "..." or a heredoc (python3 - << 'PY'), the rewritten \\!= causes a Python SyntaxError.

Root Cause

The Claude Code user-prompt-submit-hook (or an equivalent pre-execution transform) rewrites \!= to \\!= inside Bash tool command text. When a command embeds Python code inline via python3 -c "..." or a heredoc (python3 - << 'PY'), the rewritten \\!= causes a Python SyntaxError.

Fix Action

Workaround

Write Python code to a .py file and invoke with python3 file.py to bypass the hook transform.

Code Example

python3 -c "x = 1; print(x \!= 2)"

---

python3 -c "x = 1; print(x \\!= 2)"
RAW_BUFFERClick to expand / collapse

Description

The Claude Code user-prompt-submit-hook (or an equivalent pre-execution transform) rewrites \!= to \\!= inside Bash tool command text. When a command embeds Python code inline via python3 -c "..." or a heredoc (python3 - << 'PY'), the rewritten \\!= causes a Python SyntaxError.

Steps to Reproduce

  1. In a Claude Code session, run via the Bash tool: 
    python3 -c "x = 1; print(x \!= 2)"
  2. The hook rewrites it to: 
    python3 -c "x = 1; print(x \\!= 2)"
  3. Python raises SyntaxError: invalid syntax at the \\!= token.

Expected Behavior

\!= inside Bash tool command strings should not be rewritten. It is valid Python (and valid bash) syntax and has no security implications that would justify escaping.

Actual Behavior

\!= is escaped to \\!=, breaking any inline Python that uses inequality comparisons.

Workaround

Write Python code to a .py file and invoke with python3 file.py to bypass the hook transform.

Impact

Automation frameworks that generate inline Python for state manipulation (e.g. JSON ledger updates) cannot use \!= comparisons without a file-based workaround. This is especially disruptive in orchestration contexts where writing temp files adds fragility.

Environment

  • Claude Code CLI (macOS)
  • Python 3.x (any version)
  • Observed during agentic run sessions using Bash tool

extent analysis

TL;DR

The issue can be worked around by writing Python code to a file and invoking it with python3 file.py instead of using inline Python code.

Guidance

  • Identify instances where inline Python code is used with \!= comparisons and consider rewriting them to use a file-based approach.
  • Verify that the user-prompt-submit-hook is the cause of the issue by checking if the hook is enabled and if disabling it resolves the problem.
  • Consider modifying the hook to exclude rewriting \!= inside Bash tool command strings, if possible.
  • Test the workaround in different environments to ensure it works consistently.

Example

# Instead of this
python3 -c "x = 1; print(x \!= 2)"

# Use this
echo "x = 1; print(x != 2)" > temp.py
python3 temp.py
rm temp.py

Notes

The provided workaround may add complexity to automation frameworks, and a more permanent solution may be needed. The root cause of the issue is the user-prompt-submit-hook rewriting \!= to \\!=, which is not a standard Bash or Python syntax.

Recommendation

Apply the workaround of writing Python code to a file and invoking it with python3 file.py, as it is a reliable solution that bypasses the hook transform.

Vote matrix · Quick signals

Works
Did the solution work? Tap to confirm.
Easy Fix
Was it a quick fix?
Time Saver
Did it save you time?
Blocking
Was it severely blocking?
Common Issue
Are others likely hitting this too?
Flaky / Intermittent
Is it intermittent?
Verified / Reproducible
Can you reproduce it reliably?
Loading…
#api#serialization error#model compatibility#GPU setup#container setup

Still need to ship something?

×6

Another batch ranked right after the header list — different links, same matching logic.

Back to top recommendations

TRENDING

claude-code - 💡(How to fix) Fix Bash tool hook rewrites \!= to \\!= in command text, breaking inline Python comparisons [1 comments, 2 participants]