Switching to Windows containers fails #777

Bug report

Bug description

I occasionally need to verify a Windows container project and therefore switch between Linux and Windows mode.
Eventually it's failing and crashes.

Analysis (AI supported)

service.251.txt

Docker Desktop fails while preparing the Windows engine, before dockerd.exe even starts. From C:\ProgramData\DockerDesktop\service.txt:

[WindowsContainersController][E] Failed to start Windows containers:
System.Exception: Path contains symlink: C:\ProgramData\Docker\exec-root\extensions\callback.sock
at Docker.Core.PermissionUtils.CheckPath(...)
at Docker.Service.HttpAPI.WindowsContainersController.FixPermissions(String path)

Before starting the engine, Docker Desktop 4.96.3 checks the permissions on C:\ProgramData\Docker. It refuses to continue if it finds a symlink or reparse point there, which is a security hardening check. A leftover callback.sock from an earlier Windows engine session is a Unix socket, and Windows stores those as reparse points, so the check fails. The GUI then shows "An error has occurred" and switches back to Linux. This happened on every attempt today (07:16, 07:23, 07:38).

Everything else looks fine: Hyper-V is running, the vmcompute, hns and vmms services are running, and the Linux engine works.

Platform

Windows

Version information

Client:
 Version:           29.9.2
 API version:       1.56
 Go version:        go1.26.10
 Git commit:        a82e528
 Built:             Tue Oct 20 19:44:07 2026
 OS/Arch:           windows/amd64
 Context:           desktop-windows

Server: Docker Desktop 4.96.3 (244472)
 Engine:
  Version:          29.9.2
  API version:      1.56 (minimum version 1.40)
  Go version:       go1.26.10
  Git commit:       0367cbe
  Built:            Tue Oct 20 19:40:53 2026
  OS/Arch:          windows/amd64
  Experimental:     false

Diagnostics ID

No response