GPT-5.6 Terra
⧉GPT-5.6 Terra is the balanced everyday model of the GPT-5.6 family, striking an excellent balance of capability, speed and cost for day-to-day development and agent workflows. Fully OpenAI-SDK compatible: plug it into Codex, Cursor, Claude Code and similar tools with zero code changes.
Live Test · Playground
Try out GPT-5.6 Terra right here (available after login)。
Input
Advanced
This model is served over a ChatGPT-subscription upstream that does not accept temperature / top_p / max_tokens (they are silently ignored). Use reasoning_effort below for thinking depth, and prompt wording for length.
Conversation
About GPT-5.6 Terra
GPT-5.6 Terra is the balanced everyday model of the GPT-5.6 family, striking an excellent balance of capability, speed and cost for day-to-day development and agent workflows. Fully OpenAI-SDK compatible with streaming and reasoning_effort control; plug it into Codex, Cursor or Claude Code by setting model to gpt-5.6-terra. Pay-as-you-go, failed calls never billed.
Use cases
Completion, refactoring, code explanation and test writing: Terra has the best capability-to-cost ratio for everyday use.
Multi-turn tool calls and automated flows with both speed and reasoning, without paying the frontier price on every call.
OpenAI-compatible JSON / tools shapes, so existing workflows run unchanged.
How to choose
When in doubt pick Terra: it covers most tasks. Step up to Sol for the hardest work, down to Luna for high-volume low-latency traffic; all three switch on the model field alone.
FAQ
How does it differ from Sol and Luna?
Does it support reasoning_effort?
How large is the context window?
Am I charged for failed calls?
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