Fast Mode / Claude Code v2.1.36

Feature flag

tengu_penguins_enabled On for this account, and not off by default

The flag server returned on for the one account this site reads, and nothing in this release compiles it off by default. The compiled default is shown below, and says which it is when we cannot read one: a fifth of gates compile in a string or a number rather than on or off, and most published releases have no gate table behind them at all. No client can see what the server returns for your account.

This account: on · anonymous baseline: on · compiled default in v2.1.36: no gate table built for this version

These values were read against a different version of Claude Code, so treat them as the nearest reading available instead of one taken on this release.

Read once, for one account on one subscription tier, against v2.1.36. It isn't a statement about your account. What a flag value here can and cannot tell you

What

High-speed output mode for Claude Opus 4.6 that provides faster token generation without switching to a different model. Currently available as a research preview.

Usage

# Toggle fast mode from the prompt
/fast

# Or configure in settings.json
{
  "fastMode": true
}

Details

Uses the same Opus 4.6 model with accelerated output generation
Billed as extra usage at a premium rate with separate rate limits
Interactive toggle shows current status: "Fast mode ON" or "Fast mode OFF"
When enabled, displays with the penguin icon (↯) and orange color theming
Has its own rate limits; when reached, enters a cooldown period and automatically re-enables when reset
Model automatically switches to Opus 4.6 if not already selected

Availability:

Requires a paid subscription
Requires extra usage billing to be enabled (/extra-usage)
Requires the native binary (not available via npm install)
Not available on Bedrock, Vertex, Foundry, or in the Agent SDK
Organizations can disable fast mode for their accounts

Rate Limiting:

Displays "Fast limit reached and temporarily disabled · resets in X" when hitting limits
Shows "Fast limit reset · now using fast mode" when cooldown expires
Tracks remaining time to reset in the UI

Promotions:

May show discount percentages for extra usage (e.g., "50% off through [date]")

Evidence

Fast mode system (search for "Fast mode", "tengu_penguins_enabled", "/fast")

Strings lifted out of the shipped bundle, so the claim above can be checked against them.