OpenAI previews GPT-5.6 in three tiers: Sol, Terra, Luna

Category: AI
Status: developing
Sources: OpenAI, MarkTechPost, discussion
Summary: OpenAI previewed GPT-5.6 on 2026-06-26 as a three-tier family: Sol (flagship), Terra (production), and Luna (low-cost). Pricing per 1M tokens is Sol $5 input / $30 output, Terra $2.50 / $15, Luna $1 / $6. The release adds two reasoning controls: a max effort for deeper single-chain reasoning and an ultra mode that splits work across subagents. OpenAI reports Sol scoring 91.91% (ultra) and 88.76% (max) on Terminal-Bench 2.1, against 83.4% for GPT-5.5 and a cited 88% for Claude Mythos 5; these are vendor figures without independent reproduction.
Comments: HN commenters criticized the Sol/Terra/Luna naming and questioned why a "next generation model" is not GPT-6, and noted Sol keeps GPT-5.5 flagship pricing while Terra roughly halves it.
Why it matters: A tiered frontier release with a subagent reasoning mode raises the coding and cybersecurity ceiling that agent harnesses build on.
Follow-up: Watch for the broader ChatGPT/Codex/API rollout, an official context-window figure, and independent SWE-bench Verified and Terminal-Bench reproduction.