Fast-mode variant of [Opus 4.8](/anthropic/claude-opus-4.8) - identical capabilities with higher output speed at 2x pricing relative to regular Opus 4.8. Learn more in Anthropic's docs: https://platform.claude.com/docs/en/build-with-claude…
Model details →Anthropic: Claude Opus 4.8 (Fast) vs OpenAI: GPT-5.6 Luna Pro
OpenAI: GPT-5.6 Luna Pro wins on 3 of 6 axes — pricing and capability skew in its favour for most workloads.
GPT-5.6 Luna Pro is the same underlying model as [GPT-5.6 Luna](https://openrouter.ai/openai/gpt-5.6-luna), served with `reasoning.mode` set to `pro` for higher-quality responses on complex tasks. Learn more in OpenAI's docs: https://devel…
Model details →Side-by-side comparison
| Capability | Anthropic: Claude Opus 4.8 (Fast) | OpenAI: GPT-5.6 Luna Pro | Winner |
|---|---|---|---|
| Context window Maximum number of input tokens the model can attend to in a single request. | 1M | 1.1M | 🏆 OpenAI: GPT-5.6 Luna Pro |
| Input price (per 1M) Cost per million input tokens billed by the provider. | $10.00 | $0.10 | 🏆 OpenAI: GPT-5.6 Luna Pro |
| Output price (per 1M) Cost per million output tokens billed by the provider. | $50.00 | $0.60 | 🏆 OpenAI: GPT-5.6 Luna Pro |
| 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 Anthropic: Claude Opus 4.8 (Fast) better than OpenAI: GPT-5.6 Luna Pro?
OpenAI: GPT-5.6 Luna Pro wins on 3 of 6 axes — pricing and capability skew in its favour for most workloads.
What's the price difference between Anthropic: Claude Opus 4.8 (Fast) and OpenAI: GPT-5.6 Luna Pro?
Input: $10.00 vs $0.10 per 1M tokens. Output: $50.00 vs $0.60 per 1M tokens.
What context windows do Anthropic: Claude Opus 4.8 (Fast) and OpenAI: GPT-5.6 Luna Pro support?
Anthropic: Claude Opus 4.8 (Fast) supports up to 1M tokens. OpenAI: GPT-5.6 Luna Pro supports up to 1.1M tokens.
Do both Anthropic: Claude Opus 4.8 (Fast) and OpenAI: GPT-5.6 Luna Pro support tool calling?
Anthropic: Claude Opus 4.8 (Fast): yes. OpenAI: GPT-5.6 Luna Pro: yes.
Compare Anthropic: Claude Opus 4.8 (Fast) with other models
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