On March 5, 2026, the much-anticipated paper for FlashAttention-4 (FA4) was published. The code was dropped on GitHub months ago; early benchmarks circulated, and preliminary results were presented at Hot Chips in August 2025. Now we have the complete technical write-up, the full benchmark methodology, and the rigorous backward-pass results to go with it. FA4 is the best open-source attention kernel, running on the most powerful GPU hardware we have.
