GPT-5.6 Sol, Terra & Luna: Developer Guide, Benchmarks & Pricing
OpenAI announced GPT-5.6 on June 26, 2026 as a three-tier family: Sol (flagship), Terra (balanced, about 2x cheaper than GPT-5.5), and Luna (cheapest), plus a Sol Ultra mode. This guide covers what shipped in the limited preview, the tiers explained, TerminalBench 2.1 and SecureBio biology benchmarks, full pricing, how to choose a tier, the US-government rollout limit, and API usage notes.




































