OpenAI releases GPT-5.6 in three tiers with limited government-coordinated rollout

OpenAI announced GPT-5.6, launching two months after GPT-5.5, through a limited preview coordinated with the U.S. government before broader availability "in the coming weeks."

Three-tier model structure

GPT-5.6 introduces a new naming system with three capability tiers:

• Sol: Flagship model with advanced reasoning capabilities
• Terra: Balanced model for everyday work
• Luna: Fast and affordable model

According to OpenAI, this naming system uses numbers to identify model generations while Sol, Terra, and Luna represent "durable capability tiers that can advance on their own cadence."

Pricing per million tokens

The models are priced as follows:

• Sol: $5 input / $30 output
• Terra: $2.50 input / $15 output
• Luna: $1 input / $6 output

GPT-5.6 includes improved prompt caching with explicit cache breakpoints and 30-minute minimum cache life. Cache writes are billed at 1.25x the model's uncached input rate, while cache reads receive a 90% discount.

New reasoning capabilities

GPT-5.6 Sol introduces "max" reasoning effort mode, allowing the model more time for deep reasoning. An "ultra" mode goes beyond single-agent capabilities by leveraging subagents for complex work.

OpenAI claims the models show advancement in coding, biology, and cybersecurity, though specific benchmark scores were not disclosed.

Government-coordinated limited release

Unlike previous model releases, GPT-5.6 is launching through a limited preview to "a select group of trusted partners" whose participation has been shared with the U.S. government. OpenAI states: "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."

The company says it developed GPT-5.6 "with our most robust safeguards to date, with configurations matched to each model's capabilities," particularly regarding cybersecurity.

What this means

The government-coordinated rollout represents a significant shift in how frontier AI models are being released, suggesting increased regulatory oversight of advanced capabilities. The three-tier pricing structure creates clear segmentation between performance levels, with Sol priced at 6x Luna's cost for both input and output tokens. The lack of disclosed benchmark scores and the two-month release cycle from GPT-5.5 indicate OpenAI may be prioritizing rapid iteration over transparency, though the coordinated preview suggests the capabilities warranted additional scrutiny before public release.