Cowork shows "validation_failed" banner on launch — task history inaccessible after reinstall

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?

What's Wrong?

After reinstalling Claude Desktop on Windows, the Cowork tab displays
a persistent "validation_failed" warning banner immediately on launch.
The home screen loads but previous Cowork task history is not
displayed or accessible.

Local working files in connected folders are intact — only the
Cowork task/conversation history is affected.

Steps to Reproduce

1. Open Claude Desktop (post-reinstall)
2. Navigate to Cowork tab
3. "validation_failed" banner appears in the top-right corner
4. No prior Cowork task history is visible in the UI

Expected Behavior

Cowork should load without validation errors and display task history
from previous sessions.

Actual Behavior

Persistent "validation_failed" banner. Task history not displayed.

Environment

OS: Windows 11 [fill in your exact version if you know it — otherwise just "Windows 11"]
Claude Desktop version: [Open Claude → Settings or Help → About → copy the version number here]
Installation: Fresh reinstall from claude.ai/download
Account: [Pro / Max / Team — pick whichever applies]

App Data Folder State

The MSIX app data folder at
C:\Users\[username]\AppData\Local\Packages\Claude_pzs8sxrjxfjjc\
exists and contains all expected subfolders (AC, AppData, LocalCache,
LocalState, RoamingState, Settings, SystemAppData, TempState) with
recent timestamps matching my last session.

This suggests data is present on disk but cannot be read by the app
due to the validation failure.

What I've Tried

• Full uninstall + clean reinstall from claude.ai/download
• Verified working files in connected folders are intact
• Located and backed up the MSIX app data folder

Impact

Cowork task history contains work product I was actively using.
Support has clarified Cowork history is stored locally (not on
backend), so recovery depends on accessing the data in this folder.

What Should Happen?

Cowork should load without validation errors and display my previous task history. The task history should be accessible from the Cowork home screen as it was before the "validation_failed" banner appeared.

Error Messages/Logs

validation_failed

Steps to Reproduce

<img width="1318" height="866" alt="Image" src="https://github.com/user-attachments/assets/c3f42cdb-f2a1-475d-bd01-50deae9df66b" />

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

MAX

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_