GPT-5.6 Sol Review

Sol is the high end of the GPT-5.6 line that OpenAI shipped to everyone on July 9, 2026, sitting above the cheaper Terra and Luna tiers and a higher effort Sol Ultra mode. It carries a 1.05 million token context window and reads text and images, and on agentic coding it posts the numbers that matter: 88.8 percent on Terminal-Bench 2.1, with Sol Ultra reaching 91.9 percent, a hair ahead of the strongest rivals. On the Artificial Analysis Intelligence Index it led the shipped field for much of the summer. In everyday use it is the model that most often finishes a multi step task without needing a babysitter.

What you are paying for is judgment under long context. Sol holds a plan together across a big repository, calls tools in a sensible order, and recovers from its own mistakes more gracefully than the previous GPT-5.5. The weak spot is cost and cadence for bulk work. At four dollars in and twenty out per million tokens, even on the promotional rate that runs to late November 2026, it is an expensive way to grind through repetitive jobs that Luna or a cheap open model would handle for a fraction. It also deliberates, which is wonderful on a hard bug and wasteful on a mail merge.

This is the model for people whose hardest hour of the day is worth the token bill: engineers wiring up agents, analysts working through messy long documents, anyone who would rather review one careful answer than referee five fast ones. If your work is high volume and low stakes, drop down a tier. If it is the opposite, Sol is the current default.