OpenAI gives a deterministic length-n discrete Fourier transform algorithm using O(n(logn)\^{1−δ}) operations for every n, with explicit δ =1e-13. I used Opus 5.5 to improve δ to 3.2e-6. The result has been verified in lean. I suspect it can be taken further, and I don't think OpenAI was particularly interested in optimizing δ in their solution.