Microsoft has removed an access step for Windows developers using its Language Model APIs. In the October 27 Windows App SDK 2.6.4 release notes, the company says apps using that version no longer need to unlock the Language Model Limited Access Feature before using the APIs. Earlier SDK versions must still follow the applicable requirements for their target Windows versions.

The big change

  • Access: Microsoft has removed a developer-side unlock from the Language Model API path in the new SDK. Earlier SDKs retain version-specific requirements.
  • Device experience: A feature built on the API still depends on a supported, ready model. An app needs to distinguish a device that can proceed from one that needs preparation, and provide an alternative when the system cannot support the feature.
  • What to watch: Developers considering GPU use should verify Microsoft’s current deployment conditions. BIG CHANGE reviewed the documentation and did not test the release.

From permission to a working model

The Phi Silica guide describes the local model running on Copilot+ PC neural processors and qualifying Windows 11 GPUs. Microsoft’s getting-started guide shows an app submitting a prompt and receiving generated text.

Supported GPUs start at RTX 30 and Radeon RX 9060 series, with at least 6 GB VRAM. It requires Windows Insider Experimental build 26300.8553 or later, SDK 2.2.2-experimental9 or later, Developer Mode and current manufacturer-installed drivers.

The Phi Silica guide still directs developers to obtain a token without qualifying that warning by SDK version. This conflicts with the 2.6.4 release note’s version-specific change.

Microsoft plans to replace Phi Silica with Aion Instruct: Insider Preview rollout begins in November 2026 with Phi Silica initially retained, followed by retail rollout and removal in January 2027.

Check readiness before offering the feature

Microsoft’s Windows AI getting-started guide tells developers to call GetReadyState before using a model. A ready result allows the app to proceed; a supported device that is not ready may need preparation or a download. If the component is disabled or the system is unsupported, the app needs to handle that state instead of assuming an install will succeed. The guide recommends explaining a download and obtaining consent before calling EnsureReadyAsync.

The Phi Silica guide says its Copilot+ PC model is preinstalled, while the GPU model is downloaded on demand through Windows Update. The download is several gigabytes and removable by the user. The guide says Phi Silica features are unavailable in China.