OpenAI

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

Generally Available

OpenAI's prior frontier large-language-model family. GPT-5.5 (April 2026) was the broadly available flagship, built for agentic coding, computer use, and knowledge work. GPT-5.6 - variants Sol, Terra and Luna - opened to the public on July 9, 2026 after an initial government-gated preview. GPT-6 Astra, launched September 3, 2026, is now the new flagship (see that product).

Latest update Sep 10, 2026

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

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Current status

GPT-5.5 remains GA across ChatGPT and the API. GPT-5.6 Sol, Terra and Luna became publicly available on July 9, 2026; Luna is the default free-tier model with unlimited text chats as of August 2026. On July 30, 2026 OpenAI cut Luna API pricing 80% to $0.20/$1.20 per million input/output tokens and Terra pricing 20% to $2/$12, leaving Sol at $5/$30. The paid flagship role has moved to GPT-6 Astra as of September 3, 2026.

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Specifications5

GPT-5.5 Release
April 23, 2026
GPT-5.6 Release
June 26, 2026 (preview); public July 9, 2026
GPT-5.6 Variants
Sol

(flagship), Terra (balanced), Luna (fast/low-cost)

GPT-5.6 API Pricing (per M input/output tokens)
Sol $5/$30

Terra $2/$12 (cut 20% Jul 30); Luna $0.20/$1.20 (cut 80% Jul 30)

Ultrafast Mode (Sol, Cerebras)

Previewed Aug 13, 2026: up to 750 output tokens/sec (~14x standard), same intelligence level; limited preview to select API customers

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