Microsoft has restricted internal access to Claude Fable 5, Anthropic's newest flagship, on the same day it launched externally.
Anthropic released Fable 5, its first Mythos-class model, and Microsoft moved quickly to make it available through GitHub Copilot and Azure Foundry for external customers. Internally, though, employees using Microsoft's own version of GitHub Copilot won't find the model in the picker. Every other Claude model available to Microsoft staff runs under Zero Data Retention rules, meaning Anthropic doesn't hold conversation data. Fable 5 comes with different retention terms that Microsoft's internal policies won't accept.
The gap between what Microsoft sells and what it trusts is worth pausing on. Routing external customer prompts through Fable 5 is a commercial decision; exposing internal code, documents, and communications to a different data handling regime is a different one entirely. The internal ban is an implicit endorsement of the concern, not just a compliance formality.
Microsoft is one of Anthropic's larger distribution partners, which makes this less a sign of strain between the two and more a mundane reminder that vendor enthusiasm and data governance rarely travel at the same speed.