Windows AppContainer process fails to start with error 0xC0000142

Hi @jkrause berkeleyconstructors.com ,

0xC0000142 (STATUS_DLL_INIT_FAILED) indicates a failure during DLL initialization, but the status alone does not identify the module or resource responsible.

I would first trace the startup while keeping the current AppContainer/LPAC configuration unchanged. Possible causes include a dependency failing to load, a DLL failing during initialization, or initialization attempting to access a resource unavailable inside the container.

Start with Process Monitor:

1. Run Process Monitor elevated and start capturing.
2. Launch python.exe through the same AppContainer/LPAC launcher.
3. Stop the capture after it exits.
4. Use Tools > Process Tree to locate python.exe and add it as an Include filter.
5. Inspect the events immediately preceding Thread Exit / Process Exit, especially file, registry, and image-loading activity.

Microsoft documents this workflow in Troubleshoot Apps failing to start using Process Monitor. It also notes that not every ACCESS DENIED result is necessarily the cause, so nearby failures should be evaluated in context.

If Process Monitor does not isolate the issue, enable Show Loader Snaps for Python:

gflags /i python.exe +sls 

Show Loader Snaps provides detailed information about executable and DLL loading and unloading, and Microsoft documents the same gflags /i <image> +sls syntax in Example 2: Setting a Flag by Using a Flag Abbreviation.

I would avoid disabling the sandbox or broadly changing permissions until the trace identifies a specific resource. This is particularly important with LPAC, which Microsoft documents as providing greater isolation than a regular AppContainer and requiring explicit capabilities for resources that regular AppContainers may otherwise access. See Launch an AppContainer.

If possible, please share the Process Monitor events immediately preceding the python.exe exit. That should help determine whether this is a DLL initialization/loading issue or a resource-access issue.

If you found this helpful, you can refer to this guidance to confirm it and help others with similar questions.

Thank you.