Breaking

Anthropic Makes /fast a 2.5x Speed Lever for Claude Code on Opus 5.5

October 8, 2026 at 22:27 EDT

Software Dev & Coding
Foundation Models
AI Agents

Anthropic's Claude Code can use /fast as a high-speed path for Claude Opus 5.5, raising output-token speed by up to 2.5x without changing model weights. The setting is a clear speed-for-cost tradeoff: faster interactive coding loops, premium per-token pricing, and usage-credit requirements outside normal subscription rate limits.

Oct. 2026 · Anthropic

Claude Code gets a faster Opus path

The /fast toggle serves Opus 5.5 through a higher-speed configuration, giving up to 2.5x more output-token speed while keeping the same model behavior.

2.5x

maximum output-token speed gain

$8/$40

Opus 5.5 fast-mode input/output per MTok

supported Opus models: 5.5, 5, and 4.8

The speed tradeoff, drawn to scale

Each block represents 0.5x output-token speed.

Standard

Fast mode

2.5x

How a turn changes

/fast on

same Opus model

faster output stream

Best fit

Rapid coding loops, live debugging, and time-sensitive work where waiting for output is the bottleneck.

Watchouts

Premium token prices, usage-credit billing, prompt-cache effects, and separate fast-mode rate limits.

Fast mode and effort are different controls.

/fast changes serving speed. /effort changes how much work Claude does before it answers. Combining them can help small tasks, but complex work may still need higher effort.

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