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Ep 632 API Docs 1:14 w/ Laura

OpenAI Releases GPT 5.6 (Sol, Terra, Luna): A Three Tier Model Family With Programmatic Tool Calling in the Responses API

OpenAI's GPT-5.6 family — Sol, Terra, and Luna — introduces three permanent capability tiers with distinct cost profiles and a new cache billing model, plus a multi-agent Ultra mode that runs four agents in parallel by default.

New ModelsInferenceLaunchOpenAIGpt 5 6Responses APIKV CacheToken EconomicsMulti Agent OrchestrationAgentic LoopsAPI Docs
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Script Sonnet 4.6 Voice Inworld TTS 2

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Laura OpenAI just dropped a three-tier model family — and the tier names are permanent, not version numbers.

Laura Sol, Terra, and Luna each have a fixed role. They improve on their own schedule… but you pick the tier for the job, not the latest number.

Laura The sharpest change is cache billing. Cache writes now cost 1.25x the normal input rate. That's new. Cache reads still get a 90% discount — but there's a 30-minute minimum cache life to qualify.

Laura So if you're caching aggressively, you need explicit breakpoints and you need to hold that cache long enough to earn the discount back. It rewards planning.

Laura Then there's Ultra mode. By default it spins up four agents in parallel. Higher token use, stronger benchmark scores, faster time-to-result. OpenAI also tested 16-agent runs on BrowseComp and SEC-Bench Pro.

Laura Ultra lives in ChatGPT Work for Pro and Enterprise users, and in Codex for Plus and up. In the API, the multi-agent beta inside the Responses API gets you close.

Laura So the action today — pull OpenAI's published eval tables, run your token volume through their cost calculator, and check whether the Responses API multi-agent beta fits your stack.

Laura The tier you pick at the start is going to shape your spend and your ceiling for a while.