GPT-5 family (GPT-5.5 / GPT-5.6)

Overview

OpenAI's frontier large-language-model family. GPT-5.5 (April 2026) is the broadly available flagship, built for agentic coding, computer use, and knowledge work. GPT-5.6 — variants Sol, Terra and Luna — is the next generation, opened to the public on July 9, 2026 after an initial government-gated preview.

GPT-5.5 is GA across ChatGPT and the API and became the default ChatGPT model in May 2026. GPT-5.6 'Sol' (flagship), 'Terra' (balanced) and 'Luna' (fast/low-cost) entered a staggered, government-gated preview on June 26, 2026 and became publicly available to all users on July 9, 2026, with preview API pricing of $5/$30 (Sol), $2.50/$15 (Terra) and $1/$6 (Luna) per million input/output tokens.

Key Specs