Anthropic Releases FlashProve: Cryptographic Proofs That a Reply Came From Committed Weights

Anthropic's Frontier Red Team released FlashProve, an open-source zkSNARK prototype that proves a reply came from a committed model without revealing its weights, reaching about 110 tokens/second on Llama 4 Maverick (400B MoE) with one H100 and 18.78 MB proofs verified on a CPU in 17 seconds. Proving costs roughly 70 to 95x the GPU time of plain vLLM inference, and the system is currently limited to 1,024-token contexts, greedy decoding and MoE models. Security properties are formalized in Lean, with a cheating provider caught except with probability about q/2^124 + 2^-101.