›_ Claude Code Issues
Claude Code Issues / #14270

[BUG] Error: undefined is not a constructor (evaluating 'new U($,A)')

Status Fixed / completed
Maintainer reply None cached
Workaround ✓ Mentioned in description ↑
Activity 3 comments · opened Dec 17, 2025 · closed Dec 18, 2025

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 it tries to create a file it's crashing. The error undefined is not a constructor means something Claude Code expected to be a class (likely a syntax highlighter module) is undefined when it tries to instantiate it with new.

When It Triggers
It appears to crash when Claude Code tries to render file contents - specifically when:

  • Writing new files
  • Showing diffs/patches
  • Displaying code blocks

Says intermittent issue but I tried several times. Happens in Opus and Sonnet models.

What Should Happen?

Should correctly create files.

Error Messages/Logs

● This is a crash in Claude Code itself (the CLI tool), not in your project. Here's what's happening:

  Error Summary

  Error: undefined is not a constructor (evaluating 'new U($,A)')

  Location: Internal Claude Code binary (/$bunfs/root/claude:1137)

  What's Causing It

  The crash is occurring in Claude Code's syntax highlighting system when it tries to display code or file contents. Looking at the stack trace:

  1. useMemo - React is trying to memoize/cache something
  2. f6 component - This is the code display component
  3. MdI() - This appears to be a Tree-sitter based syntax highlighter
  4. IKH.highlight - Fallback highlight.js library

  The error undefined is not a constructor means something Claude Code expected to be a class (likely a syntax highlighter module) is undefined when it tries to instantiate it with new.

  When It Triggers

  It appears to crash when Claude Code tries to render file contents - specifically when:
  - Writing new files
  - Showing diffs/patches
  - Displaying code blocks

  Workaround

  The crash is intermittent. You can try:
  1. Restart Claude Code (exit and re-launch)
  2. Avoid operations that trigger code display temporarily

  How to Report

  Report this at: https://github.com/anthropics/claude-code/issues

  Include:
  - Error message: undefined is not a constructor (evaluating 'new U($,A)')
  - Location: /$bunfs/root/claude:1137:5029
  - Context: Crashes when creating files/displaying code
  - Platform: Linux (el9_7)
  - Stack trace: The useMemo → MdI() → highlight chain

  This is a bug in Claude Code's bundled syntax highlighting, not anything in your code or configuration.

Steps to Reproduce

Creating new folder and writing files.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.0.71

Platform

Anthropic API

Operating System

Other Linux

Terminal/Shell

Other

Additional Information

A custom project not related to CoHarmonify that I want to keep segregated from CoHarmonify. It's a test project I want to come
back to and see if it's something I want to pursue further.
⎿ Interrupted · What should Claude do instead?

We want to build in the staging environment so I can test a few things.

● Let me create a dedicated Chamber Universe project folder in staging.

● Bash(mkdir -p /home/elevatf7/staging/chamber-universe && ls -la /home/elevatf7/staging/)
⎿ total 1772
drwxr-x--- 17 elevatf7 nobody 12288 Dec 16 21:42 .
drwx--x--x 42 elevatf7 elevatf7 4096 Dec 7 02:00 ..
… +178 lines (ctrl+o to expand)

● Chamber Universe folder created. Now let me add the starter files.

ERROR undefined is not a constructor (evaluating 'new U($,A)')

/$bunfs/root/claude:1137:5029

1134: )+A,I=L+1,L=H.indexOf(
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  • <anonymous> (/$bunfs/root/claude:1137:5029)
  • useMemo (/$bunfs/root/claude:170:102600)
  • <anonymous> (/$bunfs/root/claude:45:7784)
  • <anonymous> (/$bunfs/root/claude:1137:4975)
  • hU (/$bunfs/root/claude:170:20695)
  • gU (/$bunfs/root/claude:170:39063)
  • zH (/$bunfs/root/claude:170:36448)
  • PH (/$bunfs/root/claude:170:35983)
  • xe (/$bunfs/root/claude:170:52039)
  • V5 (/$bunfs/root/claude:170:85835)

View original on GitHub ↗

3 Comments

shawnm-anthropic · 10 months ago

This should be fixed in tomorrow's scheduled release (v2.0.74). Thanks for reporting!

paulrigor · 10 months ago
This should be fixed in tomorrow's scheduled release (v2.0.74). Thanks for reporting!

Qq: @shawnm-anthropic - What's the usual release cadence? The installation from official bash method still points to v2.0.74. TIA!

github-actions[bot] · 9 months 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.

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