[BUG] Cowork session history, conversation logs, and project metadata silently lost between sessions (macOS)

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, macOS Apple Silicon), all session chat histories and project metadata have disappeared overnight. The Recents sidebar shows only the current session, and the Projects section displays "Create your first project" as if nothing was ever created.

Investigation findings:

• The .claude/sessions/ directory contains only one file (the current session). All previous session files are gone.
• The .claude/projects/ directory contains only one conversation log (the current session).
• All project output files on disk are intact. Only session metadata and conversation history are missing.

Only session metadata and conversation history are missing.

• Two backup files exist in .claude/backups/ but there is no documented way to restore from them.
• No user action was taken - no archiving, no account change, no app update. The app was closed normally and reopened the next morning.

Support interaction issues:

• Support initially diagnosed this as "corrupted local metadata" and recommended a destructive reset (rm ~/.claude.json, rm -rf ~/.claude/). This would have wiped 9 custom skills without recovering any data.
• Support later corrected this to a "current Cowork limitation" where session history is not guaranteed to persist.
• Support suggested checking claude.ai/recents, then acknowledged Cowork sessions do not sync to the web.
• Getting a trackable conversation ID (215473819693102) required multiple escalation requests.

This appears to be the macOS counterpart of the IndexedDB rendering/corruption issue in #33130 (Windows, ~1967 sessions affected) and related to the auto-update disk reformat that destroyed 31 sessions on Linux. The common pattern across all three: Cowork silently loses user session data without warning or recovery path.

Related issues: #33130, #27752, #29793, #29684, #27349, #24070, #29373, #29154

What Should Happen?

All Cowork session histories should persist across app restarts and be visible in the Recents sidebar. The Projects section should retain all previously created projects. Session data should never be silently deleted without user consent. If session ephemerality is intentional during the research preview, this should be clearly documented before users invest significant context into Cowork sessions.

Error Messages/Logs

No error messages in the UI. Sessions simply disappeared between app restarts.

Filesystem investigation confirms data loss (not just a rendering issue):
- `.claude/sessions/` contains only 1 file: `5.json` (current session)
- `.claude/projects/` contains only 1 .jsonl file (current session conversation log)
- `.claude/backups/` contains 2 backup files:
  - `.claude.json.backup.1775588528690` (207 bytes - minimal config)
  - `.claude.json.backup.1775628898165` (19,620 bytes - full config)
- No previous session files found anywhere on the mounted volume

Steps to Reproduce

1. Open Claude Desktop app, switch to Cowork mode
2. Work across multiple sessions over several days (creating projects, building skills, having conversations)
3. Close the app normally at end of day
4. Reopen the next morning
5. Observe: Recents sidebar is empty except for the current session
6. Observe: Projects section shows "Create your first project"
7. Inspect .claude/sessions/ - only current session file exists
8. Inspect .claude/projects/ - only current session conversation log exists
9. All project output files and SKILL.md files on user-mounted disk are intact

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Unknown - sessions were visible on April 7, 2026 and gone on April 8, 2026. No app update was observed between these dates.

Claude Code Version

Claude Desktop app (Cowork mode) - Claude 1.1062.0 (b81bcd) 2026-04-06T21:20:28.000Z

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Scope of affected work:

• Multiple weeks of Cowork sessions lost, including conversational context and iterative reasoning behind a substantial body of project work
• Output files survived on user-mounted disk; only session metadata and conversation history are missing

Support trail:

• Anthropic support conversation ID: 215473819693102
• Support initially recommended destructive reset that would have wiped custom skills without recovering data
• Support later reclassified as "current Cowork limitation" rather than a bug

Related cross-platform reports:

• #33130 - IndexedDB rendering failure, ~1967 Cowork sessions truncated (Windows). Data confirmed still in LevelDB but UI fails to render.
• Auto-update disk reformat destroying 31 active sessions (Linux). coworkd ran mkfs.ext4 on session disk after update.
• #27752, #29793, #29684, #27349 - Related session history issues

Common pattern: Cowork silently destroys user session data across macOS, Windows, and Linux without warning, confirmation, or recovery path.