OpenAI launches GPT-6 Sol and GPT-6 Luna at half the price of GPT-5.6
On Sept 22, 2026, 19 days after Astra, OpenAI released GPT-6 Sol (complex tasks, coding) and GPT-6 Luna (high-volume clerical tasks), trained with Astra's methods and priced 50% below their GPT-5.6 predecessors ($2/$10 and $0.10/$0.50 per 1M tokens); OpenAI says Sol makes about half as many factual mistakes as GPT-5.6 Sol, reaching "Astra-level reliability at much lower cost".
Key facts
- Released Sept 22, 2026 in ChatGPT Work, Codex and the API
- Plus, Pro, Business, Enterprise and Edu get both models; Free and Go users get GPT-6 Luna in the desktop app
- GPT-6 Sol API: $2 input / $10 output per 1M tokens, cached input $0.20 (OpenAI compared against $4/$20 for GPT-5.6 Sol)
- GPT-6 Luna API: $0.10 input / $0.50 output per 1M tokens, cached input $0.01 (vs $0.20/$1.20 for GPT-5.6 Luna)
- Price cut attributed to caching and inference improvements
- Sol: about half the factual mistakes of GPT-5.6 Sol on OpenAI's internal factuality eval
- Agents' Last Exam: Sol 56.4% (~95% of Astra's top score)
- DeepSWE v1.1: Sol 68.8%, Luna 66.6%; OSWorld 2.0 Offline: Sol 60.5%, Luna 58.1%
- AutomationBench 1.0.6: Sol 33.2% (extra-high effort)
- Codex CLI 0.156.1 (Sept 23) added Sol and Luna to its model picker; Codex 0.157.0 (Sept 25) added Amazon Bedrock support for them
What happened
OpenAI extended the GPT-6 generation with two cheaper models. GPT-6 Sol targets complex work such as coding; GPT-6 Luna targets "high-volume tasks with a clear goal, like summarizing documents, extracting information, or answering quick questions". Both were trained with similar methods to GPT-6 Astra. OpenAI: "GPT-6 Astra introduced a new generation of intelligence; these models extend its benefits by making that intelligence more efficient and accessible." OpenAI also claims both beat Anthropic's Fable and Opus models on its comparisons.
Why it matters
Frontier-level reliability dropped in price by half within three weeks of the flagship launch, and a GPT-6-class model (Luna) reached free users. This continues the 2026 pattern of rapid price compression across OpenAI's tiers (see the July 30 GPT-5.6 price cut).
Caveat: OpenAI's comparison uses $4/$20 for GPT-5.6 Sol, whereas launch-time third-party sources listed GPT-5.6 Sol at $5/$30; the developer-community post refers to "GPT-5.6 promotional pricing". Context window not confirmed in sources read.
Changelog
- 2026-09-29: added post link(s) (OpenAI cluster post research)
- 2026-09-29: created
Related posts (3)
- Altman: GPT-6 Sol and Luna are big improvements at half the price Sam Altman @sama · x · 2026-09-22
Altman's launch post for GPT-6 Sol/Luna emphasising the 50% token price cut. - OpenAI: 'Please welcome GPT-6 Sol and GPT-6 Luna' OpenAI @OpenAI · x · 2026-09-22
OpenAI's official launch post for the cheaper GPT-6 Sol and Luna models. - Claude Opus 5.5, GPT-6 Sol, GPT-6 Luna, and a new price war Simon Willison @simonw · blog · 2026-09-22
Same-day comparison of the two simultaneous frontier launches, framing them as a price war.
Related events
- OpenAI releases GPT-6 Astra, its first GPT-6 model ★★★★★
- OpenAI broadly releases GPT-5.6 (Sol, Terra, Luna) after government-gated preview ★★★★
- OpenAI cuts GPT-5.6 Luna price 80% and Terra 20% ★★
- OpenAI launches ChatGPT Work, a long-running agent for office work ★★★★
Sources (8)
- officialIntroducing GPT-6 Sol and Luna (OpenAI)
- officialOpenAI Developer Community announcement
- pressTechCrunch: OpenAI launches GPT-6 Sol and Luna
- pressThe New Stack: OpenAI releases GPT-6 Sol and Luna and cuts token prices in half
- pressVellum: GPT-6 Sol and Luna benchmarks explained
- discussionReleasebot: OpenAI release notes (Codex versions)
- officialOpenAI on X: 'Please welcome GPT-6 Sol and GPT-6 Luna'
- officialSam Altman on X: Sol and Luna at half the price
id: 2026-09-22-gpt-6-sol-luna · updated 2026-09-29 · open in the interactive timeline