GPT-5.6 (Sol / Terra / Luna)

GPT-5.6 (previewed June 2026) is OpenAI's new three-tier frontier family — flagship Sol, balanced Terra and low-cost Luna — with a new maximum reasoning effort and an 'ultra' sub-agent mode. It's in limited preview (API + Codex), not yet in ChatGPT.

Best for

• Frontier agentic coding and cybersecurity-grade tasks (Sol)
• Balanced everyday quality at lower cost (Terra)
• High-volume, cost-minimised workloads (Luna)
• Max reasoning effort + sub-agent 'ultra' mode

How it compares — and the India angle

• Terra matches GPT-5.5 quality at roughly half the cost, and Luna pushes price to the floor — good news for Indian budgets once it's GA.
• First major frontier launch gated behind a US-government-coordinated limited preview — not in ChatGPT yet, GA 'in coming weeks'.
• Until GA, GPT-5.5/5.4 remain the practical picks; plan to migrate to Terra/Luna for value.