›_ Claude Code Issues
Claude Code Issues / #67843

[BUG] Filesystem extension silently fails to install after Squirrel → MSIX upgrade on Windows

Status Fixed / completed
Maintainer reply None cached
Workaround ✓ Mentioned in thread ↓
Activity 12 comments · opened Jun 12, 2026 · closed Jun 17, 2026

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?

Summary

After upgrading from the Squirrel-based installer to the MSIX package, the Filesystem desktop extension cannot be installed via the Connectors directory. Clicking the Install button triggers a download but the installation never completes — no error is shown and the extension does not appear as installed.

Environment

  • OS: Windows 11
  • Claude Desktop version: 1.12603.1.0 (MSIX)
  • Package family: Claude_pzs8sxrjxfjjc
  • Upgrade path: Squirrel installer → MSIX package

What Should Happen?

Expected behavior

The Filesystem extension installs successfully and appears as an available connector.

Actual behavior

The .mcpb file is downloaded to a temp folder and copied to a dxt-install-* directory, but installation never completes. Multiple retries leave behind orphaned dxt-install-* folders.

Error Messages/Logs

### Root cause (from logs)

On every app startup, `main.log` shows:


[MSIX] Filesystem not virtualized — C:\Users\<user>\AppData\Local\Packages\Claude_pzs8sxrjxfjjc\LocalCache\Roaming\Claude absent (likely Squirrel upgrade)


The MSIX virtualization path is never created by the app on startup, so the extension installer has no valid write target. Manually creating the directory is overwritten/ignored on next launch.

The install sequence in the log:

[download:N] Starting download from .../ant.dir.ant.anthropic.filesystem/download
[warn] Installing unsigned extension from C:\...\dxt-download-XXXX.mcpb

…followed by silence. No success or failure log entry ever appears after `Installing unsigned extension`.

Steps to Reproduce

Steps to reproduce

  1. Install Claude Desktop via the Squirrel installer (older method)
  2. Upgrade to the MSIX version (e.g. via Microsoft Store or new installer)
  3. Open Claude Desktop → Code tab → + button → Connectors
  4. Select Filesystem → click Install
  5. Nothing happens — no confirmation, no error, no extension installed

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

1.12603.1.0

Platform

Other

Operating System

Windows

Terminal/Shell

Other

Additional Information

Additional notes

  • extensions-blocklist.json has 0 entries — not a blocklist issue
  • Windows Defender shows no blocks related to Claude or .mcpb files
  • Manually creating the virtualization path (AppData\Local\Packages\Claude_pzs8sxrjxfjjc\LocalCache\Roaming\Claude) does not persist across app restarts
  • Other app functionality (Code sessions, remote connectors) works normally
  • The same issue affects repeated install attempts; each attempt creates a new orphaned dxt-install-* folder in both AppData\Roaming\Claude and the virtualization path

View original on GitHub ↗

11 Comments

KunJakob · 2 months ago

Can confirm this happens for all packaged desktop extensions in our org on machines running msix installs. Installing unpackaged does however work. Seems to suggest it's related to the unzip step. I ran the app's exact extraction logic with the same yauzl version in plain Node and it worked fine. It only ever hangs inside Claude Desktop's Electron runtime, and leaks a dxt-install-* temp dir per attempt.

ChenZHAO-factorial · 2 months ago

Confirming this issue. After auto-update to Claude Desktop 1.12603.1.0 (Windows MSIX, PackageFamilyName: Claude_pzs8sxrjxfjjc):

  • Prior builds (1.106xx → 1.10628 → 1.11187) installed .mcpb files with no issue — log showed [warn] Installing unsigned extension from ... followed by Successfully installed extension.
  • On 1.12603: install attempts (both double-click and Settings → Extensions → "Install Extension") produce zero log entries. No Installing unsigned extension line, no dialog, no error. The .mcpb itself is verified intact (SHA + zip integrity).
  • Our log also surfaces the chrome-native-host EBUSY warning: Failed to copy native host binary: ... copyfile 'C:\Program Files\WindowsApps\Claude_1.12603.1.0_x64__pzs8sxrjxfjjc\...\chrome-native-host.exe' -> '...\AppData\Roaming\Claude\ChromeNativeHost\...'. Consistent with the MSIX-virtualization-path theory in this issue.
  • Affects multiple users across our org who all hit the same auto-update.

Workaround for anyone else stuck: bypass the broken install pipeline by configuring the MCP server directly in the MSIX-virtualized config at %LOCALAPPDATA%\Packages\<PackageFamilyName>\LocalCache\Roaming\Claude\claude_desktop_config.json. The standard %APPDATA%\Claude\claude_desktop_config.json no longer takes effect on MSIX builds — that's the trap.

AnaCatarino · 2 months ago

Seeing this too, and a full clean reinstall did not fix it for me.
Environment: Windows 11, personal machine. Claude Desktop 1.12603.1 (3df4fd), build 2026-06-11.
History: Originally installed Claude Desktop from the Microsoft Store (MSIX), then later installed the direct build from claude.ai/download over the top — so I hit the Store→direct migration described here.
Symptom: Trying to install the Autodesk Fusion desktop extension, the "Install Extension?" confirmation dialog appears, but clicking Install does nothing — no error, no progress indicator, and the extension never appears in the installed list.
Already tried, without success:

Run as administrator
Full quit, confirmed no leftover claude.exe (Task Manager + Get-Process claude in PowerShell)
Logged out and back in
Clean uninstall of both the Store and direct builds
Deleted leftover folders in %APPDATA%\Claude and %LOCALAPPDATA%\Packages\Claude_pzs8sxrjxfjjc
Fresh single-build reinstall from claude.ai/download

The clean single-build reinstall did not resolve it, which suggests the fix isn't simply "remove the MSIX version" — the broken state persists even after fully clearing both app-data paths.

philipjohnbasile-ta · 2 months ago

Seeing this too, can't install custom MCPs.

mauritzv · 2 months ago

Getting the same issue. Cannot install any MCPB file. Getting this error in Claude Desktop.

<img width="734" height="280" alt="Image" src="https://github.com/user-attachments/assets/f0c406da-a29b-4c58-ab27-e92727561a2c" />

haroExplorium · 2 months ago

Any news on this one?

bobikdomik54-dot · 2 months ago

@haroExplorium AND ALL OF US Its a bug with connector file unpacking, for me i got it fixed doing this:

  1. Select and click "install" on connector you want
  2. Nothing happens, so you go to path C:\Users\USERNAME\AppData\Local\Packages\Claude_pzs8sxrjxfjjc\LocalCache\Roaming\Claude and there find something like dxt-install-******, that MCPB file in that folder you need to unpack with 7zip or similar apps
  3. In Claude App you click on your nickname in left down corner —> Settings —> Extensions —> Advanced Settings
  4. Here you click on button "Install Unpacked Extension" and select a folder where you have all that files from unpacked MCPB file
  5. wait about 20 sec and Claude App will show you page with that Connector if it will work

After that i see connector in connector list and can use it ( now idk if it work because i hit my limits, but it seems fixed )

bobikdomik54-dot · 2 months ago

@KunJakob @AnaCatarino @mauritzv @haroExplorium Try if my suggestion works for you, i seen somewhere ( maybe in this chat ) that guy said to unpack it, and after success try i wrote about how to fix here

sadrirammal · 2 months ago

@bobikdomik54-dot fucking legend. Spent a few hours on this already.

philipjohnbasile-ta · 2 months ago

Does this work for an org level install?
________________________________
From: sadrirammal @.*>
Sent: Tuesday, June 16, 2026 3:58 PM
To: anthropics/claude-code @.*>
Cc: Philip John Basile @.>; Comment @.>
Subject: Re: [anthropics/claude-code] [BUG] Filesystem extension silently fails to install after Squirrel → MSIX upgrade on Windows (Issue #67843)

[https://avatars.githubusercontent.com/u/118466994?s=20&v=4]sadrirammal left a comment (anthropics/claude-code#67843)<https://github.com/anthropics/claude-code/issues/67843#issuecomment-4722901514>

@bobikdomik54-dot<https://github.com/bobikdomik54-dot> fucking legend. Spent a few hours on this already.

—
Reply to this email directly, view it on GitHub<https://github.com/anthropics/claude-code/issues/67843?email_source=notifications&email_token=B2LVDB7PWEWVQATI7KYSBB35AGRH7A5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTINZSGI4TAMJVGE2KM4TFMFZW63VHMNXW23LFNZ2KKZLWMVXHJLDGN5XXIZLSL5RWY2LDNM#issuecomment-4722901514>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/B2LVDB332O5S3K4TIZSEOZT5AGRH7AVCNFSNUABFKJSXA33TNF2G64TZHM4TGNZSGUZTINZVHNEXG43VMU5TINRUHAYDCNJVGEYKC5QC>.
Triage notifications, keep track of coding agent tasks and review pull requests on the go with GitHub Mobile for iOS<https://github.com/notifications/mobile/ios/B2LVDB6W3F3J2IKIMVGL7ID5AGRH7A5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTINZSGI4TAMJVGE2KM4TFMFZW63VHMNXW23LFNZ2KKZLWMVXHJKTGN5XXIZLSL5UW64Y> and Android<https://github.com/notifications/mobile/android/B2LVDB3GI6WWVUO2N77KMN35AGRH7A5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTINZSGI4TAMJVGE2KM4TFMFZW63VHMNXW23LFNZ2KKZLWMVXHJLTGN5XXIZLSL5QW4ZDSN5UWI>. Download it today!
You are receiving this because you commented.Message ID: @.***>

tkdats1002 · 2 months ago

The issue was resolved after updating to the latest version released today (June 18, 2026).

Showing cached comments. Read the full discussion on GitHub ↗

Related Claude Code issues

Matched on shared title terms, labels, topic and reported release — ranked so issues with real discussion come first.

Browse by topic

Same class of failure, ranked by community engagement — this issue is one of many, so it may not appear in the visible list: IDE & terminal integration, Windows & WSL problems

Browse all Claude Code issue topics →