[BUG] Windows: CTRL+Z (Undo) Crashed Claude Code

Status Fixed / completed

Maintainer reply ✓ Yes — ant-kurt

Activity 3 comments · opened Jul 20, 2025 · closed Aug 6, 2025

💡 Likely answer: A maintainer (ant-kurt, collaborator) responded on this thread — see the highlighted reply below.

Environment

Platform (select one):
[ ] Anthropic API
[ ] AWS Bedrock
[ ] Google Vertex AI
[ x] Other: Windows
Claude CLI version: 1.0.56
Operating System: Windows 11

Bug Description

Using the universal Windows key sequence for undoing an action crashed Claude Code.

Steps to Reproduce

Paste something you didn't mean to paste into the editor.
Hit CTRL+Z
Watch Claude Code crash

I expect the last keyboard action to be undone

Actual Behavior

Claude Code has been suspended. Run `fg` to bring Claude Code back.
Note: ctrl + z now suspends Claude Code, ctrl + _ undoes input.
node:internal/process/per_thread:230
        throw new ERR_UNKNOWN_SIGNAL(sig);
        ^

TypeError [ERR_UNKNOWN_SIGNAL]: Unknown signal: SIGSTOP
    at process.kill (node:internal/process/per_thread:230:15)
    at c71.handleSuspend (file:///C:/Users/RobertMcLaws/AppData/Roaming/npm/node_modules/@anthropic-ai/claude-code/cli.js:584:1908)
    at c71.handleInput (file:///C:/Users/RobertMcLaws/AppData/Roaming/npm/node_modules/@anthropic-ai/claude-code/cli.js:584:1159)
    at c71.processInput (file:///C:/Users/RobertMcLaws/AppData/Roaming/npm/node_modules/@anthropic-ai/claude-code/cli.js:584:667)
    at ReadStream.handleReadable (file:///C:/Users/RobertMcLaws/AppData/Roaming/npm/node_modules/@anthropic-ai/claude-code/cli.js:584:1049)
    at ReadStream.emit (node:events:518:28)
    at ReadStream.emit (node:domain:489:12)
    at emitReadable_ (node:internal/streams/readable:834:12)
    at process.processTicksAndRejections (node:internal/process/task_queues:89:21) {
  code: 'ERR_UNKNOWN_SIGNAL'
}

Additional Context

On Windows, there needs to be a different key that suspends the app. CTRL+Z is the universal Windows combination for "Undo".

View original on GitHub ↗

3 Comments

lukstafi · 1 year ago

This also happens under WSL with the VS Code extension -- Claude Code window disappears, opening the Claude window starts a new session (hint: bo back with /resume). Would be great to disable this effect soon, it's very easy to press CTRL+Z due to muscle memory.

ant-kurt collaborator · 1 year ago

The issue with crashing on native Windows was fixed in v1.0.57

As for WSL - we do output instructions around resumption ("Claude Code has been suspended. Run fg to bring Claude Code back."). If this keyboard shortcut continues to cause issues in WSL, we may revisit this.

github-actions[bot] · 1 year ago

This issue has been automatically locked since it was closed and has not had any activity for 7 days. If you're experiencing a similar issue, please file a new issue and reference this one if it's relevant.