OpenAI launched the GPT-5.6 family with three models: Sol, Terra, and Luna, integrated across ChatGPT, Codex, and the API. Pricing tiers range from $1 to $5 per million tokens with new cache-write pricing and a 90% cache-read discount. The launch includes new app features like ChatGPT Work, a desktop app merging Codex and ChatGPT, Sites beta, programmatic tool calling, and multi-agent beta. Sam Altman called GPT-5.6 Sol "the best model we have ever produced" with strong agentic and coding performance, improved artifact quality, and better economics.

Independent evaluations show Sol near the frontier on coding-agent workloads with an Intelligence Index score of 59, slightly below Claude Fable 5 but at about one-third the cost. Terra and Luna offer lower-cost alternatives with competitive performance.