GPT-6 Sol and Luna arrive at half the GPT-5.6 API price

OpenAI introduced GPT-6 Sol and GPT-6 Luna on Tuesday, September 22, the same day Anthropic released Claude Opus 5.5, Quartz reported.

What it costs

OpenAI's price table, per million tokens:

• GPT-6 Sol: $2 input, $10 output (GPT-5.6 Sol was $4 and $20)
• GPT-6 Luna: $0.10 input, $0.50 output (GPT-5.6 Luna was $0.20 and $1.20)

OpenAI describes this as 50% cheaper than GPT-5.6 promotional pricing. Quartz reports an OpenAI spokesperson told VentureBeat the rates have no expiration date. OpenAI also says cached input-token reads get a 90% discount. The API names are gpt-6-sol and gpt-6-luna.

Where they are

At launch, OpenAI said both models were in ChatGPT Work and Codex for Plus, Pro, Business, Enterprise, and Edu users, with Free and Go users getting Luna in the desktop app. They were "not yet available in Chat." On October 7, OpenAI brought GPT-6 to the Chat tab, using Sol for paid tiers and Luna for Free and Go.

The claims, labeled

OpenAI says GPT-6 Sol makes about half as many factual errors as its predecessor on an internal evaluation built from conversations where users flagged mistakes. OpenAI notes those conversations are not representative of typical use. Benchmark comparisons with Claude in the post are OpenAI's.

Should you switch

If you already call GPT-5.6 Sol or Luna, the new list price is half, so testing the swap costs little. If you are comparing vendors, Sol's $2/$10 is the same list price as Claude Sonnet 5.5.