OpenAI

OpenAI stopped naming models after their size. With the GPT-5.6 release on 9 July 2026 the suffixes mini and nano gave way to three names that are meant to outlive the generation: "the number identifies a model's generation, while Sol, Terra, and Luna identify durable capability tiers." GitHub's Copilot changelog states the tiers plainly on the day of general availability — Sol has "the highest reasoning ceiling in the family", Terra is "the balanced default," Luna is "a lightweight, cost-efficient variant." If the naming holds, a future generation's Sol replaces this one without renaming anything downstream.

The launch is also the first visible instance of a new gate. An executive order signed 2 June 2026 set up a voluntary process for developers to give federal agencies up to 30 days of pre-release access to "covered frontier models" for national security and cybersecurity assessment — voluntary by design, with no licensing requirement. OpenAI said it had shared the models and its release plans with the government ahead of launch and that, at the government's request, it was "starting with a limited preview" — roughly 20 organisations, before the public release two weeks later.

What the tiers cost is where the naming meets the catalog. The rows do fall in the promised order on the Artificial Analysis intelligence index — Sol at 47.1openrouter-models, last checked 2026-09-14, Terra at 42.3openrouter-models, last checked 2026-09-14, Luna at 37.5openrouter-models, last checked 2026-09-14. Listed input price sorts them into two groups rather than three: the Sol and Terra rows list at $2.00per million tokensopenrouter-models, last checked 2026-09-14 and $2.00per million tokensopenrouter-models, last checked 2026-09-14, the same number, while the Luna row lists at $0.20per million tokensopenrouter-models, last checked 2026-09-14. The names describe three rungs; the input column has two.

One oddity in the catalog, as observed on 28 August 2026: each tier's -pro row lists at the same price as its base row — openai/gpt-5.6-sol-pro matches openai/gpt-5.6-sol exactly — where the earlier openai/gpt-5.2-pro and openai/gpt-5.5-pro rows listed at several times their base rows. Either the pro premium moved into something other than per-token price, or the listing is wrong; the catalog is what it is, dated.