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OpenAI Rolls Out GPT-5.6 in API With Three Tiers: Sol, Terra, Luna

July 9, 2026 at 13:41 EDT

Foundation Models
Software Dev & Coding
AI Agents

On July 9, 2026, OpenAI began general availability of its new model family "GPT-5.6" in the API. It comprises three capability tiers — the flagship Sol, the balanced Terra, and the fast, low-cost Luna — with rollout also starting simultaneously in ChatGPT and Codex.

July 9, 2026 · OpenAI

GPT-5.6 Goes Live: Three Tiers — Sol, Terra, Luna

OpenAI opens general API access to a new model family split by intent — the flagship Sol, the balanced Terra, and the fast, low-cost Luna — letting developers pick intelligence, balance, or price.

88.8%

Sol on Terminal-Bench 2.1 (Sol Ultra: 91.9%)

~2×

Terra cheaper than GPT-5.5 at equivalent performance

750 tok/s

High-speed Sol via Cerebras, coming soon

Terminal-Bench 2.1 — coding score

Column height ∝ score (%). Sol tiers lead rivals and the prior generation.

91.9%

Sol Ultra

88.8%

Sol

84.3%

Claude Mythos 5

83.4%

GPT-5.5

Output pricing by tier

Column height ∝ output cost per 1M tokens ($). Cost drops sharply as you move down the tiers.

$30

Sol

Flagship · in $5

$15

Terra

Balanced · in $2.50

Luna

Fast/low-cost · in $1

Early praise

Stronger front-end design & reliable one-shot UI generation
High scores on math tasks
Better token efficiency → cost benefits

Open questions

Skepticism toward vendor-reported benchmarks
Possible over-optimization for benchmarks
Preview access limits & routine government review

New capabilities

Prompt caching
Explicit cache breakpoints · 30-min minimum lifetime

Multi-agent tools
Tool calling via the Responses API

Max / Ultra reasoning
Modes that leverage sub-agents

Model IDs: gpt-5.6-sol · gpt-5.6-terra · gpt-5.6-luna — delivered via API & Codex.

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