GPT-5.6 Sol, Terra, and Luna Are Now Available on just4o.chat

OpenAI’s new GPT-5.6 family is now available on just4o.chat.

Released on July 9, 2026, GPT-5.6 is a family rather than a single setting: Sol is the frontier model for difficult reasoning and coding, Terra is the balanced everyday choice, and Luna is designed for cost-sensitive, high-volume work.

Three models, one clear choice

The family is built around a simple idea: the right amount of intelligence depends on the work in front of you.

• GPT-5.6 Sol is the premium option for complex reasoning, serious coding, and knowledge work.
• GPT-5.6 Terra is the middle path when you want strong capability with a more measured cost.
• GPT-5.6 Luna is the efficient choice for repeatable workflows, drafts, classification, and high-volume tasks.

OpenAI’s API documentation lists text and image input, text output, a 1.05M-token context window, and up to 128K output tokens across the family. The documented tool surface includes functions, web search, file search, computer use, and more. Pricing is listed at $5/$30 per million input/output tokens for Sol, $2.50/$15 for Terra, and $1/$6 for Luna.

How it fits on just4o.chat

We added all three models to the model selector so you can make the tradeoff yourself instead of relying on silent routing. Sol sits at the premium end of the just4o.chat lineup; Terra and Luna make it easier to choose a capable model without spending flagship-model budget on every message. The family also supports the lower reasoning settings available in the app, giving you a practical way to tune depth to the task.

The result is a tighter workspace for moving between a hard problem, an everyday conversation, and a batch of smaller jobs without losing your context or opening another tool.

Read the official GPT-5.6 announcement and the GPT-5.6 model documentation.