claude-code - 💡(How to fix) Fix CLI crash: highlight.js toLowerCase TypeError during long sessions [1 comments, 2 participants]

ERROR  (r||"").toLowerCase is not a function. (In '(r||"").toLowerCase()', '(r||"").toLowerCase' is undefined)

/$bunfs/root/src/entrypoints/cli.js:1317:2087

The stack trace dumps ~860KB of minified highlight.js / CLI bundle source to stderr.

TL;DR

Wrap the toLowerCase() call in a type guard to prevent the TypeError from crashing the Claude Code session.

Guidance

• Verify the issue by checking if the error occurs when rendering unusual or large content, such as Metal shader source or long compiler diagnostics.
• Apply the suggested fix by wrapping the toLowerCase() call in a type guard, e.g., (typeof r === 'string' ? r : '').toLowerCase().
• Consider catching errors in the highlight pass to prevent rendering failures from crashing the entire CLI.
• Test the fix by running long multi-agent sessions with heavy tool use to ensure the error no longer occurs.

Example

// Before
(r || "").toLowerCase()

// After
(typeof r === 'string' ? r : '').toLowerCase()

Notes

This fix assumes that the r variable is expected to be a string, and that wrapping the toLowerCase() call in a type guard will prevent the TypeError. However, the root cause of the r variable being undefined or a non-string value may still need to be investigated.

Recommendation

Apply the workaround by wrapping the toLowerCase() call in a type guard, as this will prevent the TypeError from crashing the session and allow for further investigation into the root cause of the issue.