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OpenAI Opens Limited Preview of GPT-5.6 Sol, Terra and Luna

June 26, 2026 at 13:12 EDT

Foundation Models
AI Agents

OpenAI on June 26, 2026 unveiled a limited preview of new models led by its next-generation flagship, GPT-5.6 Sol. The three-tier lineup also includes Terra for everyday work and Luna for fast, low-cost use, and for now is available only to a small set of approved organizations via the API and Codex.

June 26, 2026 · OpenAI

GPT-5.6 Arrives as a Three-Model Family — Released Under a Government-Requested Limited Preview

OpenAI unveils Sol, Terra and Luna. The flagship Sol is its strongest model on cybersecurity — and that very capability is the reason its rollout has been deliberately restricted.

GPT-5.6 SOL

Next-gen flagship

Strongest on cybersecurity · SOTA on Terminal-Bench 2.1

GPT-5.6 TERRA

Balanced everyday work

GPT-5.5-level performance at half the cost

GPT-5.6 LUNA

Fast, affordable, high-volume

Most cost-efficient option

ExploitBench — Sol matches the rival, with a fraction of the tokens

Same exploitation result. Output tokens used (lower is better):

3×

Mythos Preview

1×

GPT-5.6 Sol

~one-third the output tokens for the same exploitation result.

700k

GPU-hours of automated safety testing, plus human red teaming

750

Tokens/sec for "Sol Ultra" on Cerebras, slated for July

6–7

Week update cadence — two months after GPT-5.5

Reported pricing — per million tokens (input / output)

GPT-5.6 LUNA

$1 / $6

GPT-5.6 SOL

$5 / $30

User-reported estimates — some figures remain officially unconfirmed.

Welcomed

Terminal-Bench SOTA and ExploitBench token efficiency are seen as proof OpenAI "held its lead in agentic coding."

Frustration

The preview is open only to a few pre-approved companies, and government-requested restrictions narrow access.

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