OpenAI is introducing GPT-5.6, its next-generation model, two months after the release of GPT-5.5. However, the rollout to customers won’t be as straightforward as previous model updates to ChatGPT and Codex.

GPT-5.6 consists of three models

OpenAI’s new GPT-5.6 models include three versions, inspired by the Sun, Earth, and Moon. From today’s announcement:

• Sol, our flagship model
• Terra, a balanced model for everyday work
• Luna, a fast and affordable model

OpenAI explains its thinking behind the new naming approach:

In this new naming system introduced with GPT‑5.6, the number identifies a model’s generation, while Sol, Terra, and Luna identify durable capability tiers that can advance on their own cadence. Together, the family gives people and developers clearer choices across intelligence, speed, and cost.

The company says it is “beginning a limited preview” of the GPT-5.6 series. The staggered release is due to corporation with the U.S. government:

We believe in broad access, and we plan to make GPT‑5.6 Sol, Terra, and Luna generally available in the coming weeks. As part of our ongoing engagement with the U.S. government, we previewed our plans and the models’ capabilities ahead of today’s launch. At their request, we are starting with a limited preview for a small group of trusted partners whose participation has been shared with the government, before releasing more broadly. During this preview, we will continue testing and coordinating closely with partners as we work toward broader availability. 

You can read OpenAI’s full statement on the release schedule from today’s announcement post.

As for what GPT-5.6 can do, it starts with new “max” and “ultra” reasoning effort options for GPT-5.6 Sol.

“With GPT‑5.6, we’re introducing a new max reasoning effort to give Sol the most time to reason deeply,” the company says. “Additionally, we’re introducing a new ultra mode that goes beyond the capabilities of a single agent by leveraging subagents to accelerate complex work.”

The new model displays an advancement in coding, biology, and cybersecurity, according to the company.

GPT-5.6 availability and pricing

Regarding cybersecurity, OpenAI says it “developed GPT‑5.6 Sol, Terra and Luna with our most robust safeguards to date, with configurations matched to each model’s capabilities.”

As part of the limited preview release approach, OpenAI is only releasing the new models to “a select group of trust partners and organizations” to start.

Here’s pricing details for new model usage as it becomes available:

GPT‑5.6 is priced per 1M tokens across three model sizes: Sol is $5 input / $30 output; Terra is $2.50 input / $15 output; and Luna is $1 input / $6 output. GPT‑5.6 also introduces more predictable prompt caching, including support for explicit cache breakpoints and a 30-minute minimum cache life. For GPT‑5.6 and later models, cache writes are billed at 1.25x the model’s uncached input rate, while cache reads continue to receive the 90% cached-input discount.

You can learn much more about the new GPT-5.6 models here.