MODELS
by Anthropic
Fast mode for Claude Opus 4.6 is a faster inference configuration enabled with `speed: "fast"` for supported Opus models.
Anthropic documents Fast mode as a research-preview inference configuration for supported Opus models, including Claude Opus 4.6 with model ID `claude-opus-4-6`, enabled through the Claude API using `speed: "fast"`. OpenRouter lists “Anthropic: Claude Opus 4.6 (Fast)” as a fast-mode variant of Opus 4.6 with identical capabilities, higher output speed, and premium 6x pricing. Anthropic’s Claude Opus 4.6 launch page says the base model is available on claude.ai, the Claude API, and major cloud platforms, and the official system card describes Claude Opus 4.6 as a large language model from Anthropic with documented capabilities, evaluations, safety testing, and deployment considerations.
Use when you want Claude Opus 4.6 with Anthropic’s documented faster Fast mode inference configuration. Use when higher output speed is worth the separate Fast mode pricing listed by Anthropic. Use when integrating through the Claude API and you can set `speed: "fast"` for model ID `claude-opus-4-6`.
Last updated Jun 1, 2026