GPT-5.5 vs GPT-5.6 Terra

Choose GPT-5.5 if you want hard reasoning and coding for teams in the OpenAI ecosystem. Choose GPT-5.6 Terra if you want the everyday OpenAI default for agents — volume work with frontier-adjacent quality.

In our editorial scoring, GPT-5.6 Terra leads in 3 of five dimensions (speed, value for $ and reliability), while GPT-5.5 leads in 2. On price, GPT-5.5 runs about $13 per 1M tokens (blended) and is proprietary; GPT-5.6 Terra is about $6.25 and proprietary.

The model is half the story — the agent is the other half

The model picks the moves; the agent runs the loop, the tools, and the guardrails. Once you've chosen a model, see which agent gets the most out of it.