[BUG] Claude Code crashes when Edit tool renders code containing } braces - Chalk template literal parser in diff/edit display

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 Code crashes when the Edit tool attempts to render/display code changes for files containing closing braces }. This appears to be a recent regression - the same codebase was being actively developed without this issue until recently.
The crash does NOT occur during:

File search/glob operations ✅
Reading files (even files with many } characters) ✅

The crash DOES occur during:
Edit tool operations on files containing } ❌

What Should Happen?

Rendering closing braces should not cause a claude code crash.

Error Messages/Logs

ERROR  undefined is not a constructor (evaluating 'new G($,I,L)')
/$bunfs/root/claude:1139:2360

or

ERROR  undefined is not a constructor (evaluating 'new U($,A)')
/$bunfs/root/claude:1147:5029

Steps to Reproduce

1. Open Claude Code in any project
2. Ask Claude to edit any file containing a closing brace }
3. Claude Code crashes when rendering the edit diff

What works: Reading files with } characters (Read tool succeeds)
What crashes: Editing files with } characters (Edit tool diff rendering fails)

Example

> Edit logger.php to add a comment to line 1

[Claude reads file successfully]
[Claude attempts Edit tool]
ERROR undefined is not a constructor (evaluating 'new G($,I,L)')

Root Cause

Chalk's tagged template literal parser crashes on unescaped closing braces:

const chalk = require('chalk');
chalk}; // CRASH: Found extraneous } in Chalk template literal

The Edit tool's diff rendering passes file content through Chalk templates without escaping } characters.

Test Script

const chalk = require('chalk');
const fs = require('fs');

const lines = fs.readFileSync(process.argv[2], 'utf8').split('\n');
lines.forEach((line, i) => {
try {
eval('chalk' + line.replace(//g, '\\') + '');
} catch (e) {
if (e.message.includes('extraneous') || e.message.includes('Chalk template')) {
console.log(Line ${i + 1}: ${line.substring(0, 60)});
}
}
});

Result: Any line containing } crashes.

Impact

Editing is broken for virtually all code files (PHP, JavaScript, C, Java, Go, etc.) - any language using braces for blocks.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

unsure - seems like a brand new issue, i use claude code a lot

Claude Code Version

2.0.72

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Windows Terminal

Additional Information

Issue #14180 reports crashes with Unicode filenames, also citing Chalk template parsing errors. This is the same underlying bug with a different trigger:

Aspect | #14180 | This Issue
----------------|-------------------------|---------------------------
Trigger | Unicode in filenames | } in code content
Operation | File operations | Edit tool diff rendering
Root cause | Chalk tagged template | Same
Error | undefined is not a... | Same

The #14180 author attributed the bug to Unicode handling, but our testing reveals the actual root cause: any content that doesn't conform to Chalk's {stylename text} syntax will crash the parser. Unicode characters likely create byte sequences that the parser misinterprets as malformed style syntax.