Session restore fails silently when sessions-index.json misses entries (Windows)

Description

Session resume (claude --resume "name" or /resume) frequently restores a blank/wrong session on Windows. Root cause investigation reveals 3 compounding issues:

Root Cause Analysis

1. Index Gap (Critical)

• sessions-index.json only tracks 25 of 95 actual session files on disk
• Orphaned .jsonl files exist but are invisible to the resume picker
• Likely caused by sessions ending abnormally or index write failures

2. Resume Only Matches customTitle

• The Em() function in cli.js only searches the customTitle field
• Sessions without /rename applied are completely unfindable by name
• No fallback to summary or firstPrompt

3. /clear Creates Blank Shells

• /clear preserves the session ID and index entry but wipes all messages
• /rename after /clear sets a customTitle on what is now an empty session
• Resuming this session loads the blank shell instead of the original content

Reproduction Steps

1. Start a new Claude Code session, do substantial work
2. Run /clear to clear the context
3. Run /rename "MySession" to name it
4. Exit Claude Code
5. Run claude --resume "MySession"
6. Expected: Original session content restored
7. Actual: Blank session with only post-clear messages

Environment

• Platform: Windows 11
• Claude Code: 2.1.34
• Node.js: 25.x

Related Issues

• #23610 — Session name overwritten after /resume
• #23421 — sessions-index.json stops updating
• #22614 — Incomplete session context loaded despite full file
• #23275 — /resume shows empty list (Windows)

Suggested Fix

1. Index should be rebuilt/verified on startup or periodically
2. Resume search should fall back to summary when no customTitle match
3. /clear should warn that resume will only restore post-clear content