/rename sets customTitle but not summary, causing sessions to not display in /resume picker

When using /rename to give a session a custom name, the session becomes invisible or hard to find in the /resume picker.

Root Cause

/rename sets the customTitle field in sessions-index.json, but the /resume picker displays the summary field. If a session has customTitle but no summary, it doesn't display properly.

Steps to Reproduce

1. Start a new session
2. Use /rename to give it a custom name (e.g., "My Important Session")
3. Exit the session
4. Run /resume — the custom-named session is missing or shows with wrong name

Investigation

Comparing sessions in ~/.claude/projects/*/sessions-index.json:

| Session | customTitle | summary | Shows in /resume |
|---------|-------------|---------|------------------|
| Session A | ✓ "My Title" | ✗ missing | ✗ No |
| Session B | ✓ "Other Title" | ✓ "Auto Summary" | ✓ Yes |

Sessions that were renamed but never had a summary generated are invisible in the picker.

Expected Behavior

Either:

• /rename should set both customTitle AND summary to the new name, OR
• The /resume picker should prefer customTitle over summary when displaying session names

Workaround

Manually add summary field to affected sessions in sessions-index.json:

for entry in data['entries']:
    if entry.get('customTitle') and not entry.get('summary'):
        entry['summary'] = entry['customTitle']

Environment

• Claude Code version: 2.1.29
• OS: macOS

Related

This may be related to #16973 (conversation name lost after /resume), but is a distinct issue — that bug is about name not showing in active session, this is about sessions not appearing in the picker at all.