[BUG] TypeError: undefined is not an object (evaluating '_.startsWith') when resuming conversation

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report
• [x] I am using the latest version of Claude Code

What's Wrong?

Resuming a specific conversation via claude --resume <id> crashes immediately with undefined is not an object (evaluating '_.startsWith'). The crash occurs in the diff rendering code (kF7) when the UI tries to re-render a past tool result that has an undefined file_path.

What Should Happen?

The conversation should resume and render past tool results without crashing, even if a file_path field is missing/null in a stored tool result.

Error Messages/Logs

ERROR  undefined is not an object (evaluating '_.startsWith')

 /$bunfs/root/src/entrypoints/cli.js:3142:1937

 - kF7 (/$bunfs/root/src/entrypoints/cli.js:3142:1937)
 - EW7 (/$bunfs/root/src/entrypoints/cli.js:2593:44450)
 - SA (/$bunfs/root/src/entrypoints/cli.js:675:21000)
 - BH (/$bunfs/root/src/entrypoints/cli.js:675:39546)
 - G8 (/$bunfs/root/src/entrypoints/cli.js:675:50237)
 - Ce_ (/$bunfs/root/src/entrypoints/cli.js:675:86958)
 - P3_ (/$bunfs/root/src/entrypoints/cli.js:675:85915)
 - Py_ (/$bunfs/root/src/entrypoints/cli.js:675:85736)
 - jy_ (/$bunfs/root/src/entrypoints/cli.js:675:82474)
 - OT (/$bunfs/root/src/entrypoints/cli.js:675:6372)

Steps to Reproduce

1. Have a conversation that contains file edit tool results
2. End the conversation
3. Resume it with claude --resume <conversation-id>
4. CLI crashes immediately during rendering

I haven't been able to identify what's special about this conversation vs. others that resume fine. The conversation likely contains an edit tool result where file_path is undefined/null in the stored state.

Claude Model

Opus

Is this a regression?

I don't know

Claude Code Version

2.1.84 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

iTerm2

Additional Information

Root cause analysis: The crash is in kF7, which destructures {filePath: _} from the tool result and immediately calls _.startsWith(S1()) without a null guard. This function renders structured patches for file diffs. When resuming a conversation, if a stored tool result has an undefined file_path, the renderer crashes instead of gracefully handling the missing field.