OpenAI has begun a limited preview of the GPT-5.6 series, which includes flagship Sol, balanced Terra and low-cost Luna. Terra delivers performance comparable to GPT-5.5 at roughly half the cost; Luna is positioned as a faster, highly economical option. OpenAI says GPT-5.6 Sol is its most powerful model and features strengthened safety controls against high‑risk uses, sensitive network requests and repeated abuse; the company spent weeks probing system weaknesses and stress‑testing to harden def

OpenAI has begun a limited preview of the GPT-5.6 series, which includes flagship Sol, balanced Terra and low-cost Luna. Terra delivers performance comparable to GPT-5.5 at roughly half the cost; Luna is positioned as a faster, highly economical option. OpenAI says GPT-5.6 Sol is its most powerful model and features strengthened safety controls against high‑risk uses, sensitive network requests and repeated abuse; the company spent weeks probing system weaknesses and stress‑testing to harden defenses. OpenAI plans broad availability of Sol, Terra and Luna in the coming weeks and briefed the US government on the release plan and capabilities ahead of Friday’s public notice.