[BUG] Session resume crashes with "Cannot read properties of undefined (reading 'trim')"

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?

## Description

When trying to resume a session from the session list, Claude Code crashes with:

Cannot read properties of undefined (reading 'trim')

file:///.../claude-code/cli.js:2722:6198

## Root Cause Analysis

Session .jsonl files are being created without proper summary header lines. They start with file-history-snapshot, progress, or user
type records instead of a summary record.

I wrote a repair script that adds missing summary headers, but the crash persists even after fixing all session files. This suggests the bug may
be in how session content is parsed for preview/display, not just the header.

Additionally, new sessions keep being created without proper headers - the bug is ongoing, not just affecting old sessions.

## Affected session first lines

• {"type":"file-history-snapshot",...} ❌
• {"type":"progress",...} ❌
• {"type":"user",...} ❌

## Expected first line

• {"type":"summary","summary":"...","leafUuid":null,"cwd":"..."} ✓

## Version

2.1.47+ (based on session metadata)

## Suggested Fix

Add null-safe handling when reading session data:
```javascript
const summary = sessionData?.summary?.trim?.() ?? 'Untitled Session';

Also ensure new sessions are always created with a proper summary header.

What Should Happen?

Claude should resume large session files from previously created sessions without errors.

Error Messages/Logs

ERROR  Cannot read properties of undefined (reading 'trim')

 file:///Users/id/.nvm/versions/node/v20.16.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:2722:6198

 - d15 (file:///Users/id/.nvm/versions/node/v20.16.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:2722:6198)
 - A9 (file:///Users/id/.nvm/versions/node/v20.16.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:601:21820)
 - i2 (file:///Users/id/.nvm/versions/node/v20.16.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:601:38061)
 - oT (file:///Users/id/.nvm/versions/node/v20.16.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:601:49007)
 - _M (file:///Users/id/.nvm/versions/node/v20.16.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:601:85342)
 - Li (file:///Users/id/.nvm/versions/node/v20.16.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:601:84348)
 - qi (file:///Users/id/.nvm/versions/node/v20.16.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:601:84174)
 - wh (file:///Users/id/.nvm/versions/node/v20.16.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:601:81067)
 - g0 (file:///Users/id/.nvm/versions/node/v20.16.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:601:8914)
 - hA (file:///Users/id/.nvm/versions/node/v20.16.0/lib/node_modules/@anthropic-ai/claude-code/cli.js:601:7651)

Steps to Reproduce

1. Start Claude Code in a project that has session hooks configured (e.g., SessionStart hook)
2. Have a conversation
3. Exit and try to resume the session later
4. Crash occurs - the session was created starting with a progress event instead of a summary header

The issue seems to be: When session hooks run at startup, the session file gets created with a progress record as the first line instead of a
proper summary header.
Additional context:

• Version: 2.0.64
• Platform: macOS (Darwin 22.6.0)
• The crash appears to be triggered by session files that are missing a summary header line
• New sessions are sometimes created without proper headers, causing future resume attempts to crash
• Manually adding summary headers to .jsonl files does not fix the issue - crash still occurs

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.0.64

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_