[Windows] Desktop app installation fails with 0x80073CF6 / windows.stateExtension on build 29648

Summary

The official Codex Windows desktop app cannot be installed. Microsoft Store and direct package registration both fail with 0x80073CF6.

Environment

• OS: Windows 10 Pro, Insider Dev build 29648.1000.amd64fre.rs_prerelease.260807-1623
• Architecture: x64
• Codex package: OpenAI.Codex_26.818.3698.0_x64__2p2nqsd0c76g0
• Installation source: official Microsoft Store / official Codex installer link

Error

The AppX deployment log reports:

• 0x800700B7: creation of the secure system app data folder failed because the file already exists
• windows.stateExtension registration failed with 0x800700B7
• rollback then reports 0x800703FA: registry key is marked for deletion
• final deployment error: 0x80073CF6

The package is downloaded and its signature/SHA-256 were verified. The failure occurs during AppX registration, not download or signature validation.

Steps already tried

• Reset and re-registered Microsoft Store
• DISM /Online /Cleanup-Image /RestoreHealth
• sfc /scannow
• Windows repair/in-place repair installation
• Removed OpenAI.Codex StateRepository records and WindowsApps remnants
• Verified MSIX SHA-256 and Authenticode signature
• Rebooted repeatedly
• Tested installation with a new Windows user account
• Retried Microsoft Store, winget, the official installer link, and Add-AppxPackage -Register

The same registration error remains for a new Windows user, so this does not appear to be limited to one user profile.

Additional observation

The package manifest declares MaxVersionTested="10.0.26100.0", while this machine is on Insider build 29648.

Expected behavior

The official Codex desktop app should install and register successfully on Windows, or report a clear unsupported-build requirement.

Request

Please confirm whether build 29648 is unsupported and whether a newer package or workaround exists for the windows.stateExtension registration failure.

Start by reviewing the package manifest's MaxVersionTested value alongside the AppX deployment log for the windows.stateExtension registration failure on build 29648. Determine whether the build is unsupported or the package needs updating; done means a confirmed compatibility requirement, workaround, or package fix that allows installation.