Anthropic's new prototype proves which model wrote an AI response without exposing its weights

Anthropic released FlashProve, an open-source research prototype that uses zkSNARK cryptography to prove a response came from a claimed model without revealing its weights. For Meta's 400-billion-parameter Llama 4 Maverick, it generates proofs at roughly 110 tokens per second on a single H100 GPU, with each ~19 MB proof verifiable in 17 seconds on a standard CPU, adding 70x to 95x overhead over normal inference. Anthropic notes the prototype only proves contexts up to 1,024 tokens, hides weights but not architecture, and works only when the model picks the single most likely next token rather than randomized sampling.