Ensemble is the coding agent built from The Art of Building AI Coding Agents, Bill Cox's executable teaching book. Edition 3 is the current edition: the application is C# 14 / .NET 10, developed inside Ensemble with Cadence.
Build the code and the specification together. Development earns the spec. The goal is not to write a detailed plan up front and hand it to an AI, or to vibe-code a system and document its source afterward. The goal is to become the expert by pair-programming with the AI, then preserve that expertise in a form another agent can execute.
The result is an executable specification: a codebook that transfers the judgment needed to build the system, not merely a list of desired features. Ensemble V2 executed this book to build V3; Bill and Cadence then worked inside V3 to improve both the agent and the teaching. Individual chapters retain their documented verification limits.
