[BUG] [Cowork] Win10 19045 MSIX 3P: Claude-3p unvirtualize exclude ignored; HCS/VirtioFS miss LocalCache bundle/SDK

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported with this verified combination (Win10 19045 + Desktop 1.30096.1 + 3P Claude-3p exclude ignored + CoworkVMService already running)
• [x] This is a single bug report
• [x] I am using the latest Claude Desktop MSIX currently installed on this machine: 1.30096.1.0

Related but not the same:

• #52540 #56542 #66778 (MSIX path split / junction refuse / SDK not verified after VHDX bypass)
• #85693 (3P + 19045 exclude theory; author later blamed a missing service). This host already has CoworkVMService Running/Auto/LocalSystem and still fails.

What's Wrong?

Claude Desktop Cowork Workspace never starts on Windows 10 22H2 build 19045 + MSIX + Developer Mode 3P.

Anthropic's own AppxManifest.xml excludes $(KnownFolder:LocalAppData)\Claude-3p from filesystem write virtualization so 3P userData is supposed to be the real %LOCALAPPDATA%\Claude-3p. That exclude uses virtualization:FileSystemWriteVirtualization (Microsoft min OS 20348) and virtualization is in IgnorableNamespaces. The package does not include desktop6:FileSystemWriteVirtualization (min OS 18362).

On build 19045 < 20348 the exclude is silently ignored.

• Electron/CCD write the VM bundle + SDK into Packages\Claude_pzs8sxrjxfjjc\LocalCache\Local\Claude-3p\
• CoworkVMService / HCS / VirtioFS open C:\Users\<user>\AppData\Local\Claude-3p\, which does not contain vm_bundles or claude-code-vm

The in-app probe checks LocalCache\Roaming\Claude-3p (absent) and logs Filesystem not virtualized while live data is under LocalCache\Local\Claude-3p.

This is not a Hyper-V / volume-redirect / EFS / gateway-auth failure. Local junctions are product-refused. Copying only vm_bundles only advances to the next error. We have stopped local workarounds and are waiting for a vendor fix.

What Should Happen?

Writes to %LOCALAPPDATA%\Claude-3p should land on the real directory (as the manifest comment states), or CoworkVMService / HCS / VirtioFS should resolve the MSIX LocalCache path. Workspace should start without the user copying VHDX/SDK trees or planting junctions.

Suggested fix:

1. Ship desktop6:FileSystemWriteVirtualization so Win10 18362–20347 actually unvirtualizes Claude-3p.
2. And/or teach cowork-svc / HCS / VirtioFS to use the package LocalCache path.
3. Probe LocalCache\Local\Claude-3p, not LocalCache\Roaming\Claude-3p.

Error Messages/Logs

[MSIX] Filesystem not virtualized — ...\LocalCache\Roaming\Claude-3p absent (likely Squirrel upgrade)

failed to set VHDX path: VHDX file not found: C:\Users\<user>\AppData\Local\Claude-3p\vm_bundles\claudevm.bundle\rootfs.vhdx

configure: path C:\Users\<user>\AppData\Local\Claude-3p\vm_bundles is a symlink or junction, refusing to open

RPC error -1: SDK version 2.1.229 not verified at /mnt/.virtiofs-root/shared/c/Users/<user>/AppData/Local/Claude-3p/claude-code-vm/2.1.229/.verified

.verified exists in LocalCache (64-hex marker). The guest looks at the real Local path via VirtioFS, where it is absent.

At the SDK-verify failure, VM network was CONNECTED and API REACHABLE.

Steps to Reproduce

1. Windows 10 22H2 build 19045 (or any build < 20348).
2. Install Claude Desktop MSIX 1.30096.1 (Claude_pzs8sxrjxfjjc).
3. Enable Developer Mode 3P (deploymentMode=3p). This remaps userData to %LOCALAPPDATA%\Claude-3p.
4. Confirm CoworkVMService is Running / Auto / LocalSystem, hypervisor present.
5. Start a Cowork Workspace.
6. Observe VHDX lookup on the real Local path while files were written to Package LocalCache.
7. Optional: a physical copy of only vm_bundles to the real Local path lets the VM boot, then fails at VirtioFS .verified for claude-code-vm\2.1.229.
8. A directory junction is rejected by configure (symlink or junction, refusing to open).

Is this a regression?

I don't know

Last Working Version

Unknown. Cowork Workspace has not successfully started on this host under 1.26832.0 or 1.30096.1.

Claude Code Version

Claude Desktop 1.30096.1.0 MSIX
CCD / VM SDK requested and provisioned: 2.1.229 (normal upgrade from 2.1.227)

Claude Model

Other

Platform

Other

Operating System

Windows

Terminal/Shell

Other

Additional Information

Package: Claude_1.30096.1.0_x64__pzs8sxrjxfjjc
Manifest comment (verbatim): "3P userData lives in LocalAppData; exclude so devirtualizeMsixPath/showItemInFolder see the real path"
Capability unvirtualizedResources is present; it is not sufficient on 19045 without the desktop6 FS virtualization element.

Microsoft docs:

• https://learn.microsoft.com/en-us/uwp/schemas/appxpackage/uapmanifestschema/element-virtualization-filesystemwritevirtualization (min 20348)
• https://learn.microsoft.com/en-us/uwp/schemas/appxpackage/uapmanifestschema/element-desktop6-filesystemwritevirtualization (min 18362)

AppX install + package data are on C:. Files are not EFS-encrypted. We will not continue local filesystem hacks.

Official in-app diagnostic path: Help → Troubleshooting → Generate Diagnostic Report. Can attach the exported bundle if maintainers want it.