OpenAI Unveils GPT-5.6 Sol, Terra And Luna

Credit: OpenAI

OpenAI has officially unveiled its GPT-5.6 language model family, which includes three models at different levels: the flagship Sol, the balanced Terra, and the accessible Luna. Currently, these models are available only to a limited number of trusted partners via the API and Codex, but the company expects to make them widely available in the coming weeks, including through ChatGPT.

• Sol is the flagship for the most complex tasks. A competitor to Mythos/Fable 5. It outperforms Claude in TerminalBench 2.1 (terminal/command line management), and lags slightly behind in ExploitBench (vulnerability scanning). However, it is much cheaper in terms of tokens spent.

• Terra is a balance of quality and cost. It should be roughly comparable in performance to GPT-5.5, but half the token cost.

• Luna is a fast and inexpensive model for everyday use. It looks like it will be roughly comparable to the old Opus 4.7.

For Sol, they also invented (that is, stole it from Anthropic) two additional modes:

• Max – for when the deepest reasoning is needed.

• Ultra – when the model can use subagents to solve a single problem. According to OpenAI, GPT-5.6 has been particularly strengthened in the most hyped areas:

• programming

• cybersecurity

• biology/biotech

• long agent-based tasks, where the model must maintain a goal for tens of minutes and execute a large action plan.

The models are currently in preview. More comprehensive benchmarks will follow the release of the final versions.

The company also reported that over 700,000 GPU hours were spent on automated security testing of the model on NVIDIA A100-class accelerators. Independent security experts also participated in the testing and will continue to test the model throughout the preview period.

During the limited testing, OpenAI is intentionally using stricter security measures. The company warns that some legitimate requests, particularly those related to information security research, may be temporarily blocked or subject to additional review.