Microsoft Corp. today introduced Rayfin, an open-source software development kit and command-line interface that lets developers and coding agents define an entire application back end in code and deploy it onto Microsoft Fabric.

Announced at Microsoft Build 2026, Rayfin targets a gap that has widened as artificial intelligence has made it trivial to spin up an app front end. The backend, including data, identity and access policies, still requires teams to stitch together multiple services and governance and compliance often get added too late. Many teams hit enterprise requirements they never designed for and end up replatforming to reach production.

With Rayfin, developers or the coding agents working on their behalf define data models, application programming interfaces, business logic, access policies and connections to existing data sources in one place. The definitions are strongly typed, so coding agents such as GitHub Copilot can read and modify them with the same reliability as a human. The CLI handles deployment to Fabric and stands up the databases, authentication, access policies and APIs, work that teams would otherwise wire together by hand.

Once deployed, applications run as first-class artifacts inside Fabric and connect directly to OneLake, Microsoft’s unified data layer. Governance, security and compliance come from Fabric itself, so developers do not configure them per app. And because the app sits inside the data platform, its data is ready for analytics and AI use the moment it is written, with no copies or pipelines in between. That data lands in OneLake and becomes available to Power BI, data science notebooks and Fabric’s data agents.

Microsoft is also pairing Rayfin with Replit Inc., the AI-first coding platform, so developers can build in an environment they already use while deploying into a managed Fabric tenant.

“Rayfin unlocks a new development model for our users,” Replit Chief Executive Amjad Masad said in the announcement. “Agents write the code. Fabric ships it quickly and safely. Together, we’re giving developers something they’ve never had before: a path from idea to enterprise-grade production that’s measured in hours, not months.”

Microsoft cited multitool manufacturer Leatherman Tool Group Inc. as an early customer. Its teams build and iterate in Replit but keep operational and analytical data centralized in Fabric, said Cody Luth, an AI solutions architect at the company, who noted Rayfin gives the firm fast development alongside governed data.

The release fits a wider Build 2026 theme of making Fabric the place where AI agents build and run software. Microsoft also declared general availability of Fabric IQ, which gives agents a shared layer of business context and detailed new analytics tooling on the platform.

Image: Microsoft