OpenAI has initiated a limited preview of the GPT-5.6 model series, introducing three distinct variants: Sol as the flagship, Terra for balanced everyday work, and Luna for fast, affordable tasks. The company plans to make these models generally available in the coming weeks following this initial phase with trusted partners.
The GPT-5.6 series includes specific pricing per 1M tokens: Sol costs $5 input / $30 output; Terra is priced at $2.50 input / $15 output; and Luna is $1 input / $6 output. The update also introduces more predictable prompt caching with support for explicit cache breakpoints, a 30-minute minimum cache life, and specific billing rates for cache writes and reads.
This preview serves as part of OpenAI's ongoing engagement with the U.S. government, allowing officials to review the models' capabilities before broader release.