OpenAI Launches GPT-6 Sol and Luna at Half the API Cost

OpenAI, based in San Francisco, released updated versions of two smaller models in its GPT-6 lineup on Tuesday, pricing them at half the cost of the prior 5.6 series and describing them as more accurate, according to the company's announcement reported by TechCrunch.

What are GPT-6 Sol and Luna built to do?

Sol and Luna sit below GPT-6 Astra, the flagship model OpenAI introduced earlier this month and described as its most capable system yet, TechCrunch reported. Sol is aimed at complex work such as coding, while Luna is intended for "high-volume tasks with a clear goal, like summarizing documents, extracting information, or answering quick questions," OpenAI said. "GPT-6 Astra introduced a new generation of intelligence; these models extend its benefits by making that intelligence more efficient and accessible," the company said in its announcement.

How much cheaper is API access?

OpenAI said the new Sol and Luna models are available through its API at half the price of the outgoing 5.6-series versions. The company attributed the reduction to improvements in caching and inference rather than a change in model size or architecture, according to the announcement cited by TechCrunch.

What does OpenAI say about factual accuracy?

OpenAI said GPT-6 Sol produces fewer mistakes than its predecessor and cites lower coding error rates as well. "On our internal factuality evaluation, which is based on de-identified real-world conversations where users flagged mistakes by our models, GPT-6 Sol makes about half as many mistakes as its predecessor, reaching Astra-level reliability at much lower cost," the company said. The evaluation is OpenAI's own internal measure, built from user-flagged errors rather than an independent audit.

How does the release compare with Anthropic's timing?

OpenAI's announcement repeatedly contrasts Sol and Luna's performance with Anthropic's top models, Fable and Opus, TechCrunch reported. Anthropic released an updated version of Opus 5.5 roughly 90 minutes before OpenAI's release, a sequence TechCrunch described as reflecting the pace of competition between the two labs. Neither company's benchmark claims in this exchange have been independently verified.

Where can the new models be used?

The updated Sol and Luna models are available now in ChatGPT Work, in Codex, and through the ChatGPT API for most paid accounts, according to OpenAI. Luna is also rolling out to the ChatGPT desktop app and to Free and Go tier users. OpenAI said the models would reach the ChatGPT app and website gradually over the course of the day.

What to watch

• Whether independent benchmarks corroborate OpenAI's factuality and coding-error claims, which are drawn from the company's own internal evaluation.
• How Anthropic responds with further Opus or Fable updates given the near-simultaneous release timing.
• Pricing moves from competing labs following OpenAI's stated 50 percent API cost reduction.
• Rollout pace for Luna across Free and Go tier ChatGPT users over the coming days.

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