We ship an agent that builds .NET apps; the agent itself is .NET and runs in your browser as WebAssembly. This talk is a from-the-trenches tour of the harness behind Uno Platform Studio, built on Microsoft.Extensions.AI and Microsoft Agent Framework. The decisions that survived production, with the numbers that drove them.

The centrepiece is a migration story. App generation began as one conversational agent with phase ordering written in prose, enforced by hope, and became a network of typed workflow graphs. You'll see why the LLM router we designed never shipped. Why scaffolding the app, applying themes, and the phase orchestration all became plain code. How that refactor happened, and how that meant a second production pipeline cost us a constructor rather than a new architecture.

Build, Measure, Delete: The skills system we engineered onto a strict context budget, the framework feature that came too late, and the day we reversed it all. Deleting our own machinery for the framework's native Agent Skills, watching the old failure return on cue, and settling it with one routing line.

We'll finish with questions that we still need to explore, how we might scale out further inside of our agent, and perhaps some final reflections on why LLM codegen is harder than it looks.