OpenAI ships the GPT-5.6 line — Sol, Terra, and Luna — spanning flagship reasoning down to high-volume economics. Aggressive July 2026 price cuts (Luna down 80%) reshaped the production tier.
OpenAI fields the broadest single-vendor closed lineup by tier economics: the GPT-5.6 line splits into Sol for flagship reasoning, Terra at the balanced tier, and Luna for high-volume production. Sol carries an independent index of 59, second only to Opus 5, keeping the lab within striking distance of the lead on a verified number.
Pricing is the through-line. Aggressive July 2026 cuts — Luna down roughly 80% — reset the economics of the production tier and pressured every competitor priced against high-volume workloads. The three-name split is deliberate segmentation: one architecture family addressed at three distinct cost-capability points.
Weights remain closed. The independent standing is strong at the top, but the lab's differentiation increasingly rests on price and ecosystem rather than a benchmark lead it does not hold. Where the register compares on independent numbers, OpenAI is a close second; where it competes on production economics, it is currently setting the pace.