Quick answer
On September 22, 2026 OpenAI released GPT-6 Luna and GPT-6 Sol, extending the GPT-6 family that launched with Astra on September 3. Following the naming pattern from GPT-5.6 (Sol, Terra, Luna), the new models sit beneath Astra as the broadly available and cost-efficient tiers. Luna carries forward the coding-focused role its GPT-5.6 namesake had; Sol is the general-purpose model. ChatGPT users can now choose Astra, Sol, or Luna as the backend, including in voice.
GPT-6 Astra was the headline in early September: computer use, agents, and a cybersecurity rating that changed how OpenAI ships. But Astra is priced and gated as a flagship. Luna and Sol are the models most people and most apps will actually run.
Where each model sits
- GPT-6 Astra: the flagship for agentic and computer-use work, $10/$50 per million tokens, with the strictest safeguards
- GPT-6 Sol: the general-purpose GPT-6, the default upgrade path for GPT-5.7 users
- GPT-6 Luna: tuned for coding and developer workflows, continuing the role of GPT-5.6 Luna
- GPT-5.7 remains available at $5/$15 for those not ready to move
What it means for users
In ChatGPT, the model picker now offers Astra, Sol, and Luna, and the September 23 voice update lets voice conversations run on any of the three. For most people Sol is the sensible default; Luna is for people who mostly use ChatGPT for code; Astra is for agentic tasks where its computer-use abilities matter and the cost is justified.
What it means for developers
The family structure mirrors what Anthropic did with Opus and Sonnet 5.5 the same week: a flagship for the hardest work and cheaper siblings for everything else. Expect to route by task. Coding agents to Luna, general chat and document work to Sol, browser and computer-use agents to Astra. As with every release this month, OpenAI's benchmark claims are vendor-reported and independent evaluations are still pending.
Bottom line
Luna and Sol turn GPT-6 from a flagship into a family. If you are on GPT-5.7, Sol is your upgrade; if you write code, try Luna; leave Astra for the agentic work that needs it.
