[BUG] Cowork: ALL session chat histories truncated - only last user message visible across ~1967 sessions

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?

In the Claude Desktop app (Cowork mode, Windows Microsoft Store version), ALL session chat histories have been truncated. Approximately 1967 sessions are affected.

Symptoms:

• Only the last user message remains visible in every Cowork session
• All prior conversation history (both user and assistant messages) before that final message has disappeared from the UI
• This affects ALL sessions simultaneously, not just specific ones

Investigation findings:

• Session transcripts are still accessible via the backend API (read_transcript returns full data)
• IndexedDB LevelDB files in AppData\Local\Packages\Claude_pzs8sxrjxfjjc\LocalCache\Roaming\Claude\IndexedDB still contain data (verified with strings and plyvel)
• The data is NOT physically deleted - only the UI fails to render it
• Cache clearing, app restart, and computer restart do NOT resolve the issue

Related issues: #27752, #33130, #29793, #29684, #27349

This appears to be the same IndexedDB rendering/corruption issue reported in #33130, but specifically affecting Cowork mode on Windows.

What Should Happen?

All Cowork session chat histories should display their full conversation history (all user and assistant messages) when opened in the UI, matching the data available via the backend API.

Error Messages/Logs

No specific error messages in the UI. Sessions simply show truncated history.

IndexedDB investigation confirms data exists:
- LevelDB files contain session data (verified via strings command and plyvel)
- Backend API read_transcript returns full conversation transcripts
- Custom comparator idb_cmp1 in use

Path: AppData\Local\Packages\Claude_pzs8sxrjxfjjc\LocalCache\Roaming\Claude\IndexedDB\https_claude.ai_0.indexeddb.leveldb

Steps to Reproduce

1. Open Claude Desktop app (Windows, Microsoft Store version)
2. Navigate to Cowork mode
3. Open any existing session from the sidebar
4. Observe: only the last user message is visible; all prior conversation (user + assistant messages) is missing
5. Repeat with any other session - same result across all ~1967 sessions
6. Use read_transcript API - full conversation data is returned (proving backend data is intact)
7. Inspect IndexedDB files in AppData - data exists in LevelDB binary files
8. Clear app cache, restart app, restart computer - issue persists

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Claude Desktop (Windows Microsoft Store) - Cowork mode - Claude_pzs8sxrjxfjjc

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Critical issue affecting ~1967 Cowork sessions with important AI VTuber project context.

Related issues: #27752, #33130, #29793, #29684, #27349

Root cause likely IndexedDB corruption/rendering failure (same as #33130).

Environment: Windows 11, Claude Desktop Microsoft Store (Claude_pzs8sxrjxfjjc)