Anthropic Releases FlashProve: Open-Source System Enables Verifiable LLM Inference

US-based AI company Anthropic released FlashProve on November 2, 2026, an open-source prototype system designed to solve the problem of "provable inference" for Large Language Models (LLMs). The system allows model providers to attach a short cryptographic proof to their responses, enabling users to verify within seconds that the reply was indeed generated by the claimed specific model, without needing access to the model's weights or specialized hardware.

This technology addresses trust challenges in the AI supply chain. Currently, users cannot determine if API results come from the premium model they paid for, or if they were secretly substituted by a routing service with a cheaper model, or even tampered with by attackers. FlashProve is built on Zero-Knowledge Succinct Arguments (zkSNARKs), a cryptographic tool that verifies computation integrity while hiding model weights with minimal computational overhead.

According to test data published by Anthropic, for a 400-billion-parameter mixture-of-experts model (Llama 4 Maverick, 4-bit quantized), a single H100 GPU generates proofs at approximately 110 tokens per second, with a proof size of about 19 MB per 1,024-token request. While this requires 70 to 95 times more GPU time than running the model directly using common libraries like vLLM, it represents a significant improvement over prior open-source systems, which were orders of magnitude slower.

Anthropic emphasizes that FlashProve is currently a prototype sharing intermediate progress, not a completed research agenda. Code, Lean formalization proofs, and technical reports are open-sourced under the Apache 2.0 license. This research not only helps enhance customer trust in AI providers but also offers potential tools for regulators to monitor AI development pacing and compliance, such as ensuring providers devote hardware to inference rather than secretly training new models.