GPT-5.6 Luna is a fast, cost-efficient model in OpenAI's GPT-5.6 series. It is suited for high-volume, latency-sensitive tasks such as chat, classification, and lightweight agentic workflows, providing capable reasoning for...
Model details →OpenAI: GPT-5.6 Luna vs OpenAI: GPT-5.6 Terra Pro
OpenAI: GPT-5.6 Luna wins on 2 of 6 axes — pricing and capability skew in its favour for most workloads.
GPT-5.6 Terra Pro is the same underlying model as [GPT-5.6 Terra](https://openrouter.ai/openai/gpt-5.6-terra), served with `reasoning.mode` set to `pro` for higher-quality responses on complex tasks. Learn more in OpenAI's docs: https://de…
Model details →Side-by-side comparison
| Capability | OpenAI: GPT-5.6 Luna | OpenAI: GPT-5.6 Terra Pro | Winner |
|---|---|---|---|
| Context window Maximum number of input tokens the model can attend to in a single request. | 1.1M | 1.1M | Tie |
| Input price (per 1M) Cost per million input tokens billed by the provider. | $0.10 | $1.00 | 🏆 OpenAI: GPT-5.6 Luna |
| Output price (per 1M) Cost per million output tokens billed by the provider. | $0.60 | $6.00 | 🏆 OpenAI: GPT-5.6 Luna |
| Tool / function calling First-class support for emitting structured tool calls. | Yes | Yes | Tie |
| Vision input Accepts image inputs alongside text. | Yes | Yes | Tie |
| Reasoning mode Internal chain-of-thought / extended-thinking support. | Yes | Yes | Tie |
Frequently asked questions
Is OpenAI: GPT-5.6 Luna better than OpenAI: GPT-5.6 Terra Pro?
OpenAI: GPT-5.6 Luna wins on 2 of 6 axes — pricing and capability skew in its favour for most workloads.
What's the price difference between OpenAI: GPT-5.6 Luna and OpenAI: GPT-5.6 Terra Pro?
Input: $0.10 vs $1.00 per 1M tokens. Output: $0.60 vs $6.00 per 1M tokens.
What context windows do OpenAI: GPT-5.6 Luna and OpenAI: GPT-5.6 Terra Pro support?
OpenAI: GPT-5.6 Luna supports up to 1.1M tokens. OpenAI: GPT-5.6 Terra Pro supports up to 1.1M tokens.
Do both OpenAI: GPT-5.6 Luna and OpenAI: GPT-5.6 Terra Pro support tool calling?
OpenAI: GPT-5.6 Luna: yes. OpenAI: GPT-5.6 Terra Pro: yes.
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