[Bug] Workload upload fails on Windows: valid .nupkg rejected with “Please ensure you upload a valid .nupkg package" file”

Workload Manifest Schema Version

N/A

Description

After updating to Windows 11 OS Build 26200.8xxx, workload uploads can fail because the system may not correctly recognize .nupkg files during validation.

Error: “Please ensure you upload a valid .nupkg package file.”

✅Workaround (temporary)

On the machine used to upload the workload package:

1. Open Registry Editor (regedit)
2. Go to: HKEY_CLASSES_ROOT.nupkg
3. Ensure:
   • (Default) = (value not set)
   • ContentType = not present (delete it if it exists)

4. Restart the machine (may be required) and retry the upload

Estimated fix date: 2026-05-03 (estimate; may change).

Steps to Reproduce

1. Install the latest Windows updates so the device is running Windows 11 OS Build 26200.8xxx.
2. In Microsoft Fabric Admin portal → Workloads → Upload workload, try uploading a valid .nupkg (NuGet) package.

Expected vs Actual Behavior

Expected behavior

Uploading a valid .nupkg workload package in Microsoft Fabric Admin portal → Workloads → Upload workload should succeed and the package should be accepted by the portal.

Actual behavior

After recent Windows updates (Windows 11 OS Build 26200.8xxx), the upload fails and the portal shows:
“Please ensure you upload a valid .nupkg package file.”

Relevant Logs / Error Codes

Additional Context

No response

Start by reproducing the upload in the Microsoft Fabric Admin portal on Windows 11 OS Build 26200.8xxx with a valid .nupkg package, then compare behavior with the documented registry workaround. Done means the portal accepts the valid package without requiring that workaround; no source file or test is identified in the issue.