Simon Willison at Pragmatic Summit: TDD, Conformance-Driven Development, and Prompt Injection as the Three Pillars of Production Agentic Engineering

simonwillison.net·medium signal

Willison's fireside chat at the Pragmatic Summit (Mar 14, 2026, hosted by Statsig's Eric Liu) delivers his most distilled production guidance: red-green TDD is the primary mechanism for tethering AI to reality; conformance-driven development (spec before code generation) is the discipline that makes agents maintainable; prompt injection is the systemic risk the industry is not taking seriously enough. The staged adoption model — from assistant to autonomous — provides a decision framework for how much authority to delegate per use case. This is a more compressed and opinionated version of the Agentic Engineering Patterns guide, suited for engineering leads who need to brief teams quickly.