claude-fast

A pi extension that enables Anthropic Claude Fast mode for supported Claude Opus models.

When active, the extension injects this into eligible Anthropic request payloads:

{
  "speed": "fast"
}

It also adds the required Anthropic beta header value to the current model before requests:

anthropic-beta: fast-mode-2026-02-01

Eligibility

Fast mode is only injected when all of these are true:

• The current provider is anthropic.
• The current API is anthropic-messages.
• The current model is claude-opus-4-6, claude-opus-4-7, or claude-opus-4-8.
• The request payload does not already include speed.

Claude Fast mode is available for API-key access and Claude Code subscription/OAuth access when the account has access to Anthropic's Fast mode research preview. For Claude Code subscription users, Anthropic documents this as extra usage credits, not included subscription usage.

Commands

/claude-fast

Run /claude-fast to toggle Fast mode on or off for the current session/runtime. The command reports the new state in chat, and the footer shows fast while Fast mode is active for an eligible model.

The extension defaults to off so installing the full collection does not accidentally spend Fast-mode credits.

Config

Optional global config:

~/.pi/agent/extensions/claude-fast.json

Optional project config:

.pi/claude-fast.json

Project config overrides global config.

{
  "enabled": false,
  "showStatus": true
}

• enabled: default Fast-mode state when there is no session override.
• showStatus: show a compact fast status when Fast mode is active for the current model.

Install

Standalone npm package

pi install npm:@diegopetrucci/pi-claude-fast

Collection package

pi install npm:@diegopetrucci/pi-extensions

GitHub package

pi install git:github.com/diegopetrucci/pi-extensions

Then reload pi:

/reload

Notes

• Anthropic Fast mode has separate rate limits and costs more than standard speed.
• Requests at different speeds do not share prompt-cache prefixes.
• Anthropic documents Fast mode as unavailable with Priority Tier.
• If pi adds first-class speed support later, this extension skips payloads that already contain speed.