Simon Willison · 2026-08-02 · notable
Simon Willison — three open letters split AI labs on open weights and safety
Simon Willison compares three AI open letters shipped in two weeks: Microsoft plus 235 co-signers defending open weights, Anthropic pushing back on distillation, and 1,324 lab staff asking governments to slow automated AI research.
Simon Willison reads three back-to-back AI open letters and maps where Microsoft, Anthropic and 1,324 lab employees actually disagree.
What is it?
Simon Willison's post walks through three open letters published between July 24 and July 28: 'Open Weights and American AI Leadership' organised by Microsoft with 235 co-signers including NVIDIA, Amazon, Y Combinator and OpenAI; Anthropic's solo 'Our Position on Open-Weights Models'; and 'Pacing the Frontier', signed by 1,324 frontier-lab employees.
How does it work?
Willison quotes each letter, contrasts the arguments (broad-community safety review vs. distillation risk vs. government-supported pacing), and notes who is conspicuously absent — Anthropic did not sign the Microsoft letter and released its own two days later. He then folds in Dario Amodei's public position and the recent 'Claude Code writes 80% of Anthropic's code' data point as context for the pacing letter.
Why does it matter?
The three letters are the clearest split so far between the open-weights camp and the safety-cautious camp inside frontier AI, and any US or EU rulemaking on model distribution over the next year will be shaped by which side lawmakers listen to. Willison's synthesis is one of the first serious side-by-side reads that isn't tied to a signatory.