Coding agents have made the front end of software almost trivial to generate, while standing up a secure, governed production backend has barely gotten easier. At its Build 2026 conference, Microsoft introduced Rayfin, an open-source toolset that lets developers and their coding agents define a complete application backend in code and deploy it onto Microsoft Fabric. The move turns Fabric from a destination for analytics into a governed runtime for the applications now built by agents, closing the distance between where enterprise data lives and where it gets acted on.

Where Agent-Built Apps Tend to Stall

The fastest-growing move in software development right now is describing an application in plain language and watching an agent build it. GitHub Copilot has passed 20 million users, and natural-language tools like Replit have turned code generation from autocomplete into something close to delegation. The front of the development cycle has collapsed from weeks into an afternoon, and producing a working app no longer requires an engineer.

What agents haven’t made easier is everything that comes after the prototype works. A generated app still needs a database, authentication, access policies, storage, and safe plumbing, and in an enterprise all of that has to connect to systems that the security and compliance teams already trust. That’s where most agent-built apps stall, and the deeper problem comes with the data those apps touch. Enterprises have spent years consolidating their information into governed data estates, where the most sensitive data sits under strict access and audit controls. No security team will let a quickly assembled app carrying customer records run outside that estate, so the applications that matter most are the ones least able to use the fast new path.

Closing that gap calls for a backend an agent can define as easily as it builds the front end. The definition has to live in code as one authoritative source, so the database, its API, and the app’s own code never drift apart the way generated code usually does. The access rules belong in that same code rather than a separate dashboard, and deployment has to land the finished app inside the governed estate the enterprise already runs, so that each new app strengthens that estate instead of spawning another silo.

How Microsoft Rayfin Builds a Governed Backend in Code

Rayfin, now in public preview, is Microsoft’s attempt to make building a secure production backend as fast as generating the app it serves. It’s an open-source SDK and command-line tool, available on GitHub, that lets a developer or their coding agent declare an application’s backend in code. Data models, business logic, APIs, identity, and access policies live together in one code definition, and from it Rayfin generates the database, the API, and the application code that calls them, so those pieces share a single source of truth instead of falling out of sync. The security rules sit in the same file as the data, so a row-level policy lives next to the column it protects rather than in a separate dashboard. Deploying lands the whole backend on Microsoft Fabric, where it runs as a fully managed part of the platform. It signs users in through Microsoft Entra, the company’s identity service, and stores its data in OneLake, Fabric’s data lake. The data inherits Fabric’s governance and compliance by default, usable right away by Power BI, notebooks, and Fabric’s data agents.

Access splits by audience. A developer installs Rayfin and works in an editor such as VS Code, while a business user reaches the same backend through Replit, the natural-language platform Microsoft has partnered with, which an administrator can wire to deploy straight into the company’s Fabric tenant. Both the developer and the business user stay where they already work without sidestepping governance. Replit’s chief executive framed the division of labor plainly, saying that agents write the code and Fabric ships it quickly and safely. A presenter from tool maker Leatherman, an early customer running both Fabric and Replit, described his team finally developing fast using its preferred tools while keeping applications on governed enterprise data.

Rayfin is one part of Microsoft’s broader push to make Fabric a production backend for applications, alongside other Build launches including Azure HorizonDB, a Postgres-based database, and Fabric IQ (now in GA) as a shared context layer for agents. Fabric brings real scale to that role, now past 31,000 customer organizations and running at more than $2 billion in annual revenue — which means it has grown 60% over the past year.

Governance Wins with the CIO, but the Developer Ultimately Decides

Some have likened Rayfin to a Heroku for AI-native applications, which holds in spirit, though it’s more opinionated and built for agents to target rather than humans. Speed at the front of the build stopped being the constraint a while ago. The scarce thing now is getting a generated app safely into production, and that is the work Rayfin compresses. What turns the compression into a purchase is governance, because absorbing agent speed into a controlled environment is the part almost no one has solved. Call it assurance — the confidence that a new app touches the right data, enforces the right rules, and can be reconstructed for an auditor later. Every app a team builds through Rayfin inherits that assurance the moment it ships, picking up Entra identity, OneLake data, and Fabric’s policies at deployment time instead of after a security review weeks later.

At scale, that approach should bring shadow AI under control the same way platforms once tamed shadow IT, leaving a CIO one identity model, one data layer, and one set of policies rather than a patchwork per project. The packaging is a crucial point of differentiation, with the security rules sitting in the same file as the data and a Replit on-ramp for non-developers who would otherwise build outside the tenant entirely.

The harder question is whether developers will actually use it. Governance is what a CIO wants, sure, but to a developer that same governance can feel like being locked in. Microsoft could sell Rayfin to the CIO and still watch the people who write the code skip it, because they can always build the app their usual way and add the controls later. So which apps actually use Rayfin will show whether the pitch worked. If it mostly draws small new projects rather than the important apps that hold sensitive customer data, then the governance pitch hasn’t really landed, and Fabric ends up as a place to host apps more than the place people build them. Rayfin is also still in preview, and the idea of defining a backend in code is one that other vendors are already chasing, so Rayfin will be judged on whether it holds up at real scale, rather than simply being first.

It’s worth flagging that Rayfin ties an app closely to Fabric, although that closeness is also where the value comes from. The governance is automatic precisely because the integration runs deep, so the biggest payoff naturally comes for teams already on Fabric. Microsoft is widening the path from there, keeping the SDK open source and signaling support for other places to run it over time. Microsoft’s platform breadth puts it among the front-running hyperscalers, pulling analytics, databases, a semantic layer, and now app development onto one platform while most point-solution rivals go deep in just one. The other hyperscalers are chasing the same broad vision, which keeps this a real race. What matters next is making it easy to start small, smoothing the transition away from older and competing systems, and answering the questions that Build left open about pricing, availability, and how Rayfin overlaps with Power Apps, Microsoft’s existing low-code app builder.

Owning the Data Estate and the Software on Top

Enterprise software is shifting from a craft of writing code to a discipline of governing what gets built. Once anyone can stand up a working application by describing it, the bottleneck stops being how fast the thing gets made and becomes whether anyone can vouch for what it does. Boards and regulators are already asking which data a given app reached and who authorized it, and those questions get harder when an agent built the app. The organizations pulling ahead treat that scrutiny as a reason to centralize what their people build rather than a reason to slow them down.

Rayfin is Microsoft’s bet that whoever owns the governed data estate is best positioned to own the application layer that agents are building on top of it. The natural home for that bet is the software that runs inside the business, where stitching together separate data, AI, and app tools gets expensive once audit and governance enter the picture — and where a single governed platform can win on cost and control. That’s where Rayfin is aimed, with consumer-scale apps left to the best-of-breed combinations that already fit them. Within that home, the platform that already holds the data can now host the software that runs against it. Whether the bet pays off depends on the months after the preview, as Microsoft works to turn demos into customers running Rayfin in production, extend the open-source promise past Fabric’s own walls, and win over the developers who decide whether Fabric becomes a place to build or only a place to deploy.