Testing on Terminal-Bench 2.1 found that GPT-5.6 Terra completed successful tasks in Kiro at roughly 82% cost reduction. OpenAI has made its GPT-5.6 family — Sol, Terra, and Luna — available in Kiro, AWS's software development agent. The companies say the models support spec-driven development, helping developers turn requirements into implementation plans, complete multi-step coding tasks, and review work at checkpoints.
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