OpenAI Ships GPT-5.6 (Sol, Terra, Luna) to General Availability — Sol Beats Claude Fable 5 on Agents' Last Exam

Summary

On July 9, 2026, OpenAI released the GPT-5.6 family to general availability across ChatGPT, Codex, and the API — moving beyond the June 29 limited preview. The family has three tiers: **Sol** (flagship, complex reasoning and agentic workloads, $5 in / $30 out per 1M tokens), **Terra** (balanced, competitive with GPT-5.5 at roughly half the cost, $2.50 / $15), and **Luna** (smallest and cheapest, $1 / $6). All three carry a 1M-token context window, 128K max output, and a February 16, 2026 knowled