OpenAI launches GPT-6 Sol and Luna, cheaper than Astra
Two new models join the GPT-6 family, with API prices cut in half and immediate deployment in Work and Codex.
Translation of the original French article. Proposed by AI, reviewed by the author.
OpenAI announced on September 22, 2026 GPT-6 Sol and GPT-6 Luna, two models of the GPT-6 generation designed to bring some of Astra's advances to faster, cheaper use cases. The official announcement specifies a 50% drop in API prices compared to the promotional rate of the GPT-5.6 Sol and Luna versions, with immediate availability in ChatGPT Work and Codex for most paid accounts.
What GPT-6 Sol and GPT-6 Luna are
Earlier in September, OpenAI launched GPT-6 Astra, presented as the most capable model in the family. Sol and Luna expand this generation. According to OpenAI, they were trained with methods similar to Astra's, to bring gains in professional work, factuality, code, computer use and alignment to more affordable models.
In the hierarchy described by the press and product notes, Sol targets complex tasks, notably code and agentic workflows. Luna targets high-volume, clear-objective tasks — document summarization, information extraction, quick answers. Astra remains the "no-compromise" choice when depth matters more than cost.
API pricing and positioning versus GPT-6 Astra
OpenAI attributes the price drop to gains in caching and inference, passed on to customers. The official API rates (per million tokens) are as follows:
| Model | Input | Output | Change vs GPT-5.6 |
|---|---|---|---|
| GPT-6 Sol | $2 (vs $4) | $10 (vs $20) | −50% |
| GPT-6 Luna | $0.10 (vs $0.20) | $0.50 (vs $1.20) | −50% |
The API identifiers are gpt-6-sol and gpt-6-luna. OpenAI adds that prompt caching for GPT-6 aims for higher hit rates by default, with an announced 90% reduction on cached input token reads — a useful point for agents and long conversations.
Astra is not being replaced. OpenAI keeps it as the best "all-around" model, reserved for the most demanding projects. Sol and Luna sit on the cost–intelligence curve, to iterate more and deploy at greater scale.
Where to use Sol and Luna in ChatGPT and Codex
According to the official announcement, GPT-6 Sol and GPT-6 Luna are available starting today in ChatGPT Work and Codex for Plus, Pro, Business, Enterprise and Edu users. Free and Go accounts can access Luna in the desktop app. These models are not yet available in Chat.
Rollout in ChatGPT Work and Codex may be gradual throughout the day. 9to5Mac notes also point out that availability depends on deployment and workspace settings; Enterprise admins must enable the new models.
What the duo changes for code and agents
OpenAI emphasizes the cost of long-running agentic code. In its blog, the lab estimates that, valued at API price, daily token usage exceeds $600 for the median internal researcher, and $7,000 at the 90th percentile — hence the push for more efficient models for Codex and agents.
On substance, OpenAI claims measured gains (factual and internal benchmarks) over the GPT-5.6 predecessors and, in several tables, over Anthropic models cited for comparison. These scores come from the vendor; they should be read as claims to be checked against real-world use, not as an independent verdict. TechCrunch also notes that the release comes about 90 minutes after Claude Opus 5.5, a sign of the day's head-to-head competition.
In short, Sol and Luna are not a single "GPT-6 bis." They are two tiers of the same Astra generation, calibrated for volume, code and agents, with a clear message on price and a presence first in Work, Codex and the API.
Sources
- Introducing GPT-6 Sol and Luna (OpenAI, Sept. 22, 2026)
- OpenAI launches GPT-6 Sol and Luna (TechCrunch)
- OpenAI upgrading ChatGPT and Codex with two more GPT-6 models (9to5Mac)
- Anthropic and OpenAI roll out cheaper models (CNBC)
- GPT-6 Sol API model documentation
Frequently asked questions
What are GPT-6 Sol and GPT-6 Luna
They are two OpenAI models of the GPT-6 generation, announced on September 22, 2026. Sol is geared toward complex tasks (code, agents); Luna is geared toward focused, high-volume tasks. They extend Astra's advances toward faster, cheaper use cases.
How do they differ from GPT-6 Astra
Astra remains the most capable model in the family, recommended for the most demanding projects. Sol and Luna carry over some of Astra's methods and strengths (professional work, factuality, code, computer use, alignment) with a cost-efficiency positioning and API prices cut in half compared to GPT-5.6 Sol and Luna.
How much do GPT-6 Sol and Luna cost via the API
According to OpenAI, Sol drops to $2 / million tokens for input and $10 for output; Luna to $0.10 for input and $0.50 for output. That's a 50% drop compared to the GPT-5.6 promotional rate. The API IDs are gpt-6-sol and gpt-6-luna.
Where are GPT-6 Sol and GPT-6 Luna available
They are available in ChatGPT Work and Codex for Plus, Pro, Business, Enterprise and Edu. Free and Go have access to Luna on the desktop app. They are not yet in Chat. Rollout may be gradual; the API exposes them under the IDs above.
The AI Desk. (2026). OpenAI launches GPT-6 Sol and Luna, cheaper than Astra. The AI Desk. https://ntilia.com/u/aidesk/en/openai-launches-gpt-6-sol-and-luna-cheaper-than-astra (consulté le 2026-10-22)