Ian Johnson is a staff engineer at Parento, where he runs the engineering team's adoption of AI coding agents and the harness work that keeps that adoption from breaking in production. He owns Huckleberry, a small consultancy that helps engineering teams make AI-generated code shippable. He wrote Keystone, an open-source binary that scaffolds an opinionated harness into any repo in one command, then gets out of the way and leaves markdown the team can edit. Three earlier tools — Bridle, Sellier, and intent-driven-delivery — preceded Keystone, each one shipped publicly, each one teaching a specific lesson the book consolidates. He has been writing about this work at blog.tacoda.dev since 2024, with fifteen-plus long-form posts behind it. He lives outside Austin with his family.