OpenAI unveils GPT-5.6 Sol, Terra and Luna models — but only accessible to limited preview partners for now, per US Gov

OpenAI has announced a limited preview of its GPT-5.6 model series, consisting of three models: Sol, Terra, and Luna, with the flagship Sol model delivering a major performance gain for long-running coding, cybersecurity, and agentic tasks. The GPT-5.6 series introduces a new max reasoning effort mode and an ultra mode, which expands past the structural boundaries of a single standalone model, deploying specialized "subagents" to divide, conquer, and accelerate multi-step, long-horizon projects. The models have achieved state-of-the-art scores on various benchmarks, including Terminal-Bench 2.1 and Agent's Last Exam. The limited preview is available to a narrow set of trusted partners and organizations, with a broader public launch pending completion of a 30-day review process by the U.S. government. The practical implication for engineers building AI systems is that they will need to na

⚡ Key Takeaways

• The GPT-5.6 Sol model is priced at $5.00 per million input tokens and $30.00 per million output tokens.
• The ultra mode configuration expands past the structural boundaries of a single standalone model, deploying specialized "subagents" to divide, conquer, and accelerate multi-step, long-horizon projects.
• GPT-5.6 Sol (Ultra) achieves a state-of-the-art score of 91.91% on Terminal-Bench 2.1.
• The models have achieved superior token efficiency relative to preceding architectures, as shown in benchmarks such as Agent's Last Exam.
• The limited preview is available through the API and Codex to a narrow set of trusted partners and organizations.

The introduction of the GPT-5.6 model series and its novel architectural features, such as the max reasoning effort mode and ultra mode, has the potential to significantly impact the development of AI systems, particularly in areas such as coding, cybersecurity, and agentic tasks. The limited preview and pending review process by the U.S. government also highlight the increasing importance of safe

✅ Practical Steps

1. Apply the concepts from this article to your own system design, considering the potential benefits and challenges of implementing the max reasoning effort mode and ultra mode in your AI systems.
2. Evaluate the potential benefits of using the GPT-5.6 model series for your specific use case, considering factors such as performance gain, token efficiency, and compliance requirements.

Want the full story? Read the original article.