[BUG] installDxtFromDirectory reply never sent — org connector fails to install on v1.12603.1

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?

i want to file a bug report when installing desktop extension (.mcpb) for the latest 1.12 version. It works on older version.. After MSIX auto-update on Windows, the installDxtFromDirectory IPC handler never sends a reply when attempting to install the org-published connector, consistently failing on both VDI and laptop across multiple reinstall attempts.

This custom extension is set up as an allowed connector.

See attached for log files

From claude-ai-web.log:
installDxtFromDirectory': reply was never sent
From main.log:
Installing unsigned extension from ...\dxt-download-*.mcpb
[MSIX] Filesystem virtualization active

claude-diagnostic-sed-b5f3725d-20260612-2001.zip

What Should Happen?

It should install custom extension without issues.

Error Messages/Logs

Steps to Reproduce

Steps to Reproduce
Environment:

Windows 11 (10.0.26100)
Claude Desktop v1.12603.1
Install type: MSIX via Microsoft Store / Intune
Claude Enterprise org with connector allowlist enabled
Org-published connector: ant.dir.ant.0x7233f24.exeter-sql-mcp-server v2.0.1

Prerequisites:

Clean install of Claude Desktop (MSIX) — connector installs successfully ✅
Allow Claude to auto-update to latest version

Steps:

Install Claude Desktop via MSIX package
Launch Claude — install org connector from Settings → Connectors → confirm it works ✅
Allow Claude to auto-update (or force update)
After update completes, relaunch Claude
Attempt to install org connector from Settings → Connectors

Expected: Connector installs successfully as it did before the update
Actual: Connector download starts, temp .mcpb file is created, then installDxtFromDirectory IPC handler never responds — connector never installs

Observed in logs:
claude-ai-web.log:
Error invoking remote method '...$_Extensions_$_installDxtFromDirectory': reply was never sent

main.log:
[MSIX] Filesystem virtualization active
Installing unsigned extension from ...\dxt-download-*.mcpb <-- IT IS STUCK HERE...
can_install check completed: 0 extensions checked

Additional notes:

Reproducible 100% with 1.12. It works it 1.11
Full AppData wipe + reinstall with older version resolves it (not viable at scale)
No Intune registry policies present at HKLM:\SOFTWARE\Policies\Claude

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

1.12

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_