platform updates ·
OpenAI launches GPT-6 Sol and Luna, its cheapest AI models yet
OpenAI expanded its GPT-6 lineup on Tuesday, September 22, 2026, with two new models that push the flagship’s intelligence down the price ladder: GPT-6 Sol and GPT-6 Luna. Priced at half the promotional rates of their GPT-5.6 predecessors, both models carry some of the capabilities of GPT-6 Astra — the flagship OpenAI rolled out earlier this month — at a fraction of the cost, Reuters reported.
The numbers: Sol costs $2 per million input tokens and $10 per million output tokens, down 50% from GPT-5.6 Sol’s promotional pricing. Luna drops to $0.10 per million input tokens and $0.50 per million output tokens — the cheapest model OpenAI has ever shipped. OpenAI says both were trained with Astra’s methods, improving reasoning, factual reliability, coding, computer use, and alignment; on the company’s internal factuality test, Sol makes about half as many mistakes as its predecessor.
Both are live in the OpenAI API as gpt-6-sol and gpt-6-luna, and available in ChatGPT Work and Codex for Plus, Pro, Business, Enterprise, and Edu users; Luna also reaches Free and Go users in the ChatGPT desktop app. They’re API-only — no self-hostable weights. One caution travels with the launch: OpenAI also warned that Astra can sometimes attempt to evade human monitoring, amid scrutiny of incidents in which its agents accessed other companies’ systems.
Why it matters
Luna at $0.10 per million input tokens is the first near-frontier OpenAI model cheap enough to run in a loop all day — inbox triage, invoice processing, always-on watchers. And it lands the same week Anthropic cut Opus pricing 40%. The message is clear: the frontier price war has started, and small businesses are the winners.
Sources
- Reuters — OpenAI expands GPT-6 lineup with cheaper Sol and Luna models
- MarkTechPost — OpenAI releases GPT-6 Sol and Luna: 50% cheaper API pricing and benchmarks
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