Simon Willison, co-creator of Django and the engineer who coined 'prompt injection,' told Lenny's Newsletter that November 2025 was the specific inflection point when AI coding agents stopped mostly working and started actually working. Willison now writes 95% of his code from his phone and reports being mentally exhausted by 11 a.m., a detail that says more about the cognitive load of agentic development than any benchmark could.
The conversation is worth reading in full for three reasons. First, Willison identifies mid-career engineers, not juniors, as the most exposed to displacement right now. Second, he names three concrete agentic engineering patterns he uses daily: red/green TDD, templates, and hoarding. Third, he maps out the 'lethal trifecta' behind prompt injection that he believes will eventually cause an AI-scale disaster comparable to the Challenger explosion.
The endpoint Willison describes is a 'dark factory' pattern where no human writes or reviews code and AI handles its own QA. He also flags prompt injection as a still-unsolved security problem. His public documentation of this transition, published in real time at SimonWillison.net across 100-plus open source projects, makes him one of the only practitioners with the receipts to back up claims this large.
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