Mechanism◆Article
OpenAI used GPT-5.6 Sol to optimize the model's forward pass and autonomously rewrite production kernels in Triton and Gluon, reducing end-to-end serving costs by 20%.
OpenAI explains how GPT-5.6 Sol optimized load balancing and the computational forward pass, using Codex to rewrite GPU kernels and reduce serving costs by 20%. ✦ AI generated
OpenAI · Simon Willison's Weblog · 2026-07-30 · original ↗
We also used GPT‑5.6 Sol to optimize the model's forward pass: the computation that transforms inputs into next-token predictions. Even when individual operations are fast, excess memory movement, synchronization, and inefficient data layouts can leave GPUs idle. To avoid this, GPT‑5.6 Sol found work that could be precomputed, avoided, or parallelized. With Codex, GPT‑5.6 Sol autonomously rewrote and optimized our production kernels, the core code that executes the mathematical operations that make up the model. This worked in part because we've trained GPT‑5.6 to be effective at writing and improving kernels in Triton and Gluon, two open-source GPU programming languages maintained by OpenAI. These efforts, combined with broader kernel advancements from GPT‑5.6 Sol, reduced end-to-end serving costs by 20%.
Read full article ↗excerpt · fair-use quotation
- ·Found precomputable, avoidable, or parallelizable work
- ·Reduced GPU idle from memory movement and synchronization
- ·Optimized the input-to-prediction computation
- ·Codex autonomously rewrote and optimized production kernels
- ·Kernels in Triton and Gluon, OpenAI's open-source GPU languages
- ·Combined efforts cut end-to-end serving costs by 20%
Around this claim
This moment responds to
explains mechanism → At $0.20/$1.20 per million tokens, GPT-5.6 Luna is cheaper than Google's Gemini 3.1 Flash-Lite and 1/5th the input price of Anthropic's Claude Haiku 4.5.Author · Simon Willison's Weblogprovides context → Sol did not autonomously conduct end-to-end post-training or research on Luna; what likely happened is a model implementing small graders, reward-shaping logic, or training configs on top of OpenAI's existing mature RL infrastructure.scaling01 (X/Twitter) · Latent Space