Why the Top‑Tier GPT‑5.6 Model Is Still Unavailable

OpenAI announced the release of GPT‑5.6, yet the most capable version cannot be used yet due to intervention by the United States government. The model has been divided into three tiers—Sol, Terra, and Luna—corresponding to premium, mainstream, and budget editions.

The Sol ultra tier is the most noteworthy. In the publicly available evaluations, Sol ultra scores 91.0% on the Terminal‑Bench 2.1 coding benchmark, surpassing Mythos/Fable 5’s 88.0% by three points. In the CyberGym security benchmark, Sol ultra achieves 83.6% , slightly ahead of Mythos Preview’s 83.1% .

Mythos still holds advantages in other suites such as ExploitBench, CyScenarioBench, and HealthBench Professional, where it remains the stronger performer.

Consequently, the claim is not that Sol ultra "completely crushes" its rival, but that it has taken the lead in several high‑value battlefields, making the overall impression clearly stronger than Mythos.

Beyond raw performance, Sol ultra introduces a more aggressive task‑decomposition ability: it can automatically break a complex objective into multiple sub‑tasks and assign them to different agents, effectively turning a single model into a temporary team that coordinates the work.

Because of its strength, the U.S. government has begun to intervene in areas like coding, vulnerability discovery, and network security. As a result, the high‑capability version is not being fully opened to the public, and many users cannot access it at present.

This situation highlights a shift in large‑model competition: the race is moving from "who releases first" to "who opens the model to users first." If Sol ultra eventually becomes fully available, OpenAI’s entire coding product line, especially the Codex direction, is likely to see a major upgrade.