Microsoft Build Shows Rayfin Shipping Backends to Fabric
Microsoft Build on June 2–3, 2026 put Rayfin in preview, and the pitch is plain: turn a generated app into a typed, governed backend with one CLI command. The open-source SDK and CLI are aimed at developers who want app data, identity, and policy to stay inside a Microsoft Fabric tenant instead of being stitched together later.
Rayfin and Microsoft Fabric
Rayfin can generate a backend that includes database, auth, storage and access policies, then ship it to Microsoft Fabric through one CLI command. For developers, that means the handoff from prototype to something closer to production is meant to take fewer steps, with app data landing in OneLake by default without copy or ETL.
Microsoft partnered with Replit on the deployment workflow. Build in Replit, deploy with Rayfin, and the app, data and services stay in the user's own Fabric tenant. That is the practical guardrail in the announcement, because the workflow is not just about speed; it is also about where the backend ends up and who controls it.
Replit and tenant control
The friction point is that Rayfin is still a preview. Microsoft is asking developers to trust a new path from AI-assisted app generation to governed deployment before the broader rollout details are complete, so teams that need strict production planning will still have to treat the workflow as early.
Rayfin also arrived inside a larger Build push around agent development, which included the GitHub Copilot app in preview and Microsoft Foundry releases that the company said rounded out four layers production agents had been missing.
Foundry and Copilot preview
The GitHub Copilot app is a native desktop app, and it can start from existing GitHub Issues, Pull Requests and other sessions. It uses git worktrees so each session has its own space with its own branches, files, conversations and task state, which gives developers a clearer way to keep parallel work from colliding.
Microsoft said Hosted Agents in Foundry Agent Service will be generally available in coming weeks, with per-session sandboxing for untrusted code, sub-100 ms cold starts and zero idle cost in a framework-agnostic runtime. Microsoft Agent Framework v1.0 was generally available, new toolboxes in Foundry were in preview, Fireworks AI on Foundry was generally available, Managed Compute was in private preview and Foundry IQ was generally available.
The open question for teams weighing Rayfin is pricing and release timing beyond preview, because the Build announcement gives deployment details but not the commercial terms or a full availability date for the broader rollout.
