Cowork rootfs.vhdx.zst checksum mismatch — server serves wrong artifact (expected 21237ca8, got 01b19a53) on Win11 Home, app 1.12603.1.0

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?

Cowork fails to start on Windows 11 Home. The workspace VM download fails with a persistent checksum mismatch for rootfs.vhdx.zst. The downloaded file's hash NEVER matches the expected hash, and the actual hash is byte-for-byte identical across every attempt, which points to the CDN serving a wrong/mismatched artifact rather than local corruption.

Error shown in UI and logs:
Checksum mismatch for rootfs.vhdx.zst:
expected 21237ca86d15885ed7dcbe1c66b8b3a464c914648b16300070b12b1e1212e451
got 01b19a53c3cfd86d7742b19a9fc60eada7225e6042eb7113628487e5e9ead635

Regular Chat mode works perfectly. Only Cowork is affected.

ENVIRONMENT

• OS: Windows 11 Home, version 25H2, OS Build 26200.8655
• Claude Desktop: 1.12603.1.0 (MSIX install)
• Bundle version: 6d1538ba6fecc4e5c5583993c4b30bb1875f0f5a
• Plan: Max
• Hyper-V services confirmed Running: vmms (Automatic), vmcompute (Manual), CoworkVMService (Automatic)

KEY EVIDENCE THAT THIS IS SERVER-SIDE, NOT LOCAL

1. The "got" hash (01b19a53...) is IDENTICAL on every download attempt. Random network corruption would produce a different hash each time.
2. Fully deleted the VM bundle with rd /s /q (Remove-Item -Force silently fails on MSIX LocalCache paths, ref #60371). Confirmed via dir that vm_bundles no longer existed.
3. Log after deletion confirms a 100% fresh download with no cache reuse:

[warm] No warm file found for rootfs.vhdx at current version
[cache] No cached compressed file for rootfs.vhdx
rootfs.vhdx not found, downloading...
...still results in the SAME mismatched hash.

1. Tested over two completely separate networks (home WiFi and mobile-data hotspot / different ISP). Identical "got" hash on both, ruling out any local or ISP cache.

The app (build 1.12603.1.0) expects rootfs.vhdx.zst with hash 21237ca8..., but downloads.claude.ai consistently serves a file with hash 01b19a53.... This looks like a deploy desync between the client's expected checksum and the artifact on the CDN.

STEPS TO REPRODUCE

1. Install Claude Desktop on Windows 11 Home.
2. Open the Cowork tab.
3. Workspace attempts to download rootfs.vhdx.zst and fails with the checksum mismatch above.

EXPECTED: rootfs.vhdx.zst checksum validates and the workspace starts.
ACTUAL: Checksum mismatch on every attempt, across fresh downloads and multiple networks.

What Should Happen?

The Cowork workspace should download rootfs.vhdx.zst with a valid checksum and start successfully, the same way regular Chat mode works without issues.

Error Messages/Logs

2026-06-13 16:18:35 [info] [Bundle:status] rootfs.vhdx missing
2026-06-13 16:18:35 [info] [warm] No warm file found for rootfs.vhdx at current version
2026-06-13 16:18:35 [info] [cache] No cached compressed file for rootfs.vhdx
2026-06-13 16:18:35 [info] rootfs.vhdx not found, downloading...
2026-06-13 16:18:35 [info] Downloading rootfs.vhdx...
2026-06-13 16:18:43 [warn] [setYukonSilverConfig] Stale-bundle refresh failed (non-fatal): Checksum mismatch for rootfs.vhdx.zst: expected 21237ca86d15885ed7dcbe1c66b8b3a464c914648b16300070b12b1e1212e451, got 01b19a53c3cfd86d7742b19a9fc60eada7225e6042eb7113628487e5e9ead635
2026-06-13 16:18:43 [error] [download] VM download failed: Checksum mismatch for rootfs.vhdx.zst: expected 21237ca86d15885ed7dcbe1c66b8b3a464c914648b16300070b12b1e1212e451, got 01b19a53c3cfd86d7742b19a9fc60eada7225e6042eb7113628487e5e9ead635
2026-06-13 16:18:43 [info] [VM:start] Beginning startup, bundlePath=...\vm_bundles\claudevm.bundle
2026-06-13 16:18:43 [info] [VM:start] Bundle version: 6d1538ba6fecc4e5c5583993c4b30bb1875f0f5a
2026-06-13 16:18:47 [error] [VM:start] Startup failed: Error: Checksum mismatch for rootfs.vhdx.zst: expected 21237ca8...64c914648b16300070b12b1e1212e451, got 01b19a53...7225e6042eb7113628487e5e9ead635
2026-06-13 16:18:47 [info] [VM:start] Skipping auto-reinstall (already attempted once)

Steps to Reproduce

1. Install Claude Desktop 1.12603.1.0 on Windows 11 Home (25H2, Build 26200.8655).
2. Open the Cowork tab.
3. The workspace attempts to download rootfs.vhdx.zst and fails with a checksum mismatch (expected 21237ca8..., got 01b19a53...).
4. Fully delete the VM bundle: quit Claude from the system tray, Stop-Service CoworkVMService, then rd /s /q "%LOCALAPPDATA%\Packages\Claude_pzs8sxrjxfjjc\LocalCache\Roaming\Claude\vm_bundles" (note: Remove-Item -Force silently fails on MSIX LocalCache paths).
5. Reopen Cowork. A fully fresh download (no warm/cache files) produces the SAME mismatched hash.
6. Repeat on a different network (mobile-data hotspot, different ISP): identical "got" hash, confirming it is not local or ISP cache.

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

1.12603.1.0

Claude Code Version

N/A — using Cowork in Claude Desktop 1.12603.1.0 (not Claude Code CLI)

Platform

Other

Operating System

Windows

Terminal/Shell

Terminal.app (macOS)

Additional Information

This is a Claude Desktop Cowork issue (not Claude Code CLI). Regular Chat mode works perfectly; only Cowork fails. The form fields are CLI-oriented, so "Platform/Terminal" don't directly apply.

Summary: rootfs.vhdx.zst fails checksum validation on every download attempt with a byte-for-byte identical mismatched hash, across fully fresh downloads (cache deleted via rd /s /q) and two separate networks (WiFi + mobile data). This strongly indicates downloads.claude.ai is serving an artifact whose hash does not match the checksum the client build (1.12603.1.0) expects — a likely deploy desync between client and CDN.