[BUG] Cowork: Minor version update permanently deletes chat history and scheduled tasks

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?

After a minor version update of Claude Desktop (Cowork mode) on Windows 11 Pro, ALL previous chat session history (left sidebar) and ALL Cowork MCP scheduled tasks were permanently deleted. Restarting the app does not restore the data.

What Should Happen?

Chat session history and scheduled tasks should be preserved across minor version updates. At minimum, users should receive a warning before any data-destructive update occurs.

Error Messages/Logs

No error message shown. The app updated silently and launched normally, but all previous session data was gone.

Investigation findings (via filesystem inspection):
- %APPDATA%\Claude\local-agent-mode-sessions\ contained only 1 session (the current one)
- Previous sessions under the old VM UUID were deleted during update
- mcp__scheduled-tasks__list_scheduled_tasks returned "No scheduled tasks found"
- sessiondata.vhdx appeared to be freshly initialized

Steps to Reproduce

1. Use Claude Desktop (Cowork mode) over multiple sessions, accumulating chat history and scheduled tasks
2. Allow the app to perform a minor version auto-update
3. Relaunch the app
4. Observe: left sidebar shows no previous chat history
5. Run any scheduled task list tool: returns "No scheduled tasks found"

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Unknown - version before the minor update that caused the issue

Claude Code Version

Claude Desktop (Cowork mode) - claude-code v2.1.78

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

Root Cause Analysis

Chat history loss:
Session data is stored in:
%APPDATA%\Claude\local-agent-mode-sessions\{vm-uuid}\{org-id}\

The minor version update appears to provision a new VM instance (new vm-uuid) without migrating .json/.jsonl session files from the previous instance. Only the active session survives.

Scheduled task loss:
Cowork MCP scheduled tasks are stored inside sessiondata.vhdx (VM persistent disk). This file appears to be reset/replaced during the update, wiping all task definitions.

Impact Summary

• Chat history: permanently lost (unrecoverable)
• MCP scheduled tasks: permanently lost (unrecoverable)
• No warning shown before or after the update

Suggested Fixes

1. Migrate session .json/.jsonl files between VM UUID directories on update
2. Preserve sessiondata.vhdx content across version upgrades
3. Show warning dialog before any data-destructive update
4. Consider cloud backup for session metadata