Breaking

OpenAI to Open GPT-5.6 Sol, Terra and Luna to Public Thursday

July 8, 2026 at 02:50 EDT

Foundation Models
AI Agents
Software Dev & Coding

Around July 8, 2026, OpenAI officially announced it will release its next-generation models "GPT-5.6 Sol," "Terra" and "Luna" to the public this Thursday (around July 10). It is currently expanding preview access globally, intensifying the "frontier model" contest with Anthropic's Claude Fable 5.

June 26, 2026 · OpenAI

GPT-5.6 Arrives: Cheaper & Faster to Challenge Claude Fable 5

OpenAI previews its next-gen trio — flagship Sol, balanced Terra, and low-cost Luna — with public launch around July 9. Sol undercuts Anthropic's Fable 5 on price and speed while the rivalry over autonomy and intelligence sharpens.

Output price per 1M tokens — Sol vs Fable 5

$30

GPT-5.6 Sol

$50

Claude Fable 5

Sol's output is 40% cheaper; on input it's $5 vs Fable's $10 per 1M tokens.

$1 / $6

Luna in/out per 1M tokens — the low-cost tier

750 t/s

Sol's supported throughput on Cerebras

11.3h–270h+

Measured Time Horizon of autonomous operation

Terminal-Bench 2.1 — higher is better

Sol Ultra91.9%

Sol (standard)88.8%

Fable 583.4–84.3%

Sol leads here, but some results such as SWE-Bench Pro are said to favor Fable.

Praise for Sol

"Fixes all the pain points" of Fable
Excellent subagent understanding
Runs autonomously for more than a day
Strong for iOS development

Fable 5 still leads

Ahead on agentic ability & intelligence
Better frontend and UI sensibility
But expensive with strict usage quotas
Frustration over limits and resets

The takeaway

With Sol, Terra and Luna launching around July 9, a "use both" sentiment is spreading — OpenAI leads on price and speed, while Anthropic draws support for autonomy and intelligence.

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