Fast Mode - Claude Code

Fast mode runs Opus with an accelerated inference path - roughly 2.5x the throughput at a higher per-token price.

What it does

When fast mode is enabled, Claude Code routes Opus calls through a lower-latency backend. You pay more per token, but turns complete faster. Quality matches standard Opus. It's a straight speed-for-cost tradeoff for sessions where wall-clock time matters more than spend.

When to use it

• Interactive work where latency hurts flow.
• Pair-programming sessions where Claude needs to keep up with you.
• Time-critical debugging or incident response.
• Demos and recordings where dead air looks bad.

Gotchas

• Fast mode is a research preview. Availability and pricing can change.
• Cost can balloon on long sessions. Watch your /status regularly.
• Only Opus is accelerated. Sonnet and Haiku ignore the flag.

Official docs: https://code.claude.com/docs/en/fast-mode.md