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Fast mode is in research preview. The feature, pricing, and availability may change based on feedback.
Fast mode is a high-speed configuration for Claude Opus, making the model 2.5x faster at a higher cost per token. Toggle it on with /fast when you need speed for interactive work like rapid iteration or live debugging, and toggle it off when cost matters more than latency. Fast mode is not a different model. It uses Claude Opus with a different API configuration that prioritizes speed over cost efficiency. You get identical quality and capabilities, just faster responses. Fast mode is supported on Opus 4.6 and Opus 4.7. It is not available on Sonnet, Haiku, or other models.
Fast mode requires Claude Code v2.1.36 or later. Check your version with claude --version.
What to know:
  • Use /fast to toggle on fast mode in Claude Code CLI. Also available via /fast in Claude Code VS Code Extension.
  • By default, /fast runs on Opus 4.6. To run fast mode on Opus 4.7 instead, set the CLAUDE_CODE_ENABLE_OPUS_4_7_FAST_MODE environment variable.
  • Fast mode pricing is 30/30/150 MTok on both Opus 4.6 and Opus 4.7.
  • Available to all Claude Code users on subscription plans (Pro/Max/Team/Enterprise) and Claude Console.
  • For Claude Code users on subscription plans (Pro/Max/Team/Enterprise), fast mode is available via extra usage only and not included in the subscription rate limits.
This page covers how to toggle fast mode, use fast mode on Opus 4.7, the cost tradeoff, when to use it, requirements, per-session opt-in, and rate limit behavior.

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Toggle fast mode

Toggle fast mode in either of these ways:
  • Type /fast and press Tab to toggle on or off
  • Set "fastMode": true in your user settings file
By default, fast mode persists across sessions. Administrators can configure fast mode to reset each session. See require per-session opt-in for details. For the best cost efficiency, enable fast mode at the start of a session rather than switching mid-conversation. See understand the cost tradeoff for details. When you enable fast mode:
  • If you’re on a different model, Claude Code automatically switches to the fast mode model: Opus 4.6 by default, or Opus 4.7 when CLAUDE_CODE_ENABLE_OPUS_4_7_FAST_MODE is set.
  • You’ll see a confirmation message: “Fast mode ON”
  • A small ↯ icon appears next to the prompt while fast mode is active
  • Run /fast again at any time to check whether fast mode is on or off
When you disable fast mode with /fast again, you remain on the same Opus version that fast mode was running on. The model does not revert to your previous model. To switch to a different model, use /model.

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Use fast mode on Opus 4.7

Fast mode on Opus 4.7 requires Claude Code v2.1.139 or later.
Fast mode for Claude Opus 4.7 is in research preview. It runs at the same 2.5x speed and the same price as fast mode for Opus 4.6, with no other behavior changes.
On May 14, 2026, Opus 4.7 becomes the default fast mode model. Until then, opt in by setting CLAUDE_CODE_ENABLE_OPUS_4_7_FAST_MODE=1.
To opt in, set CLAUDE_CODE_ENABLE_OPUS_4_7_FAST_MODE=1 before launching Claude Code. With the variable set, /fast runs on Opus 4.7. Without it, /fast continues to run on Opus 4.6. You can set the variable as a shell export: 
export CLAUDE_CODE_ENABLE_OPUS_4_7_FAST_MODE=1
Or in any Claude Code settings file, including user, project, and managed settings, to scope the opt-in: 
{
  "env": {
    "CLAUDE_CODE_ENABLE_OPUS_4_7_FAST_MODE": "1"
  }
}
Fast mode for Opus 4.6 remains available alongside Opus 4.7. The two share the same fast mode rate limit pool: usage on either model draws from the same limits. To pin fast mode to Opus 4.6 explicitly, set CLAUDE_CODE_OPUS_4_6_FAST_MODE_OVERRIDE=1. This variable takes precedence, so fast mode runs on Opus 4.6 regardless of whether CLAUDE_CODE_ENABLE_OPUS_4_7_FAST_MODE is set.

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Understand the cost tradeoff

Fast mode has higher per-token pricing than standard Opus:
ModeInput (MTok)Output (MTok)
Fast mode on Opus 4.6$30$150
Fast mode on Opus 4.7$30$150
Fast mode pricing is flat across the full 1M token context window. When you switch into fast mode mid-conversation, you pay the full fast mode uncached input token price for the entire conversation context. This costs more than if you had enabled fast mode from the start.

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Decide when to use fast mode

Fast mode is best for interactive work where response latency matters more than cost:
  • Rapid iteration on code changes
  • Live debugging sessions
  • Time-sensitive work with tight deadlines
Standard mode is better for:
  • Long autonomous tasks where speed matters less
  • Batch processing or CI/CD pipelines
  • Cost-sensitive workloads

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Fast mode vs effort level

Fast mode and effort level both affect response speed, but differently:
SettingEffect
Fast modeSame model quality, lower latency, higher cost
Lower effort levelLess thinking time, faster responses, potentially lower quality on complex tasks
You can combine both: use fast mode with a lower effort level for maximum speed on straightforward tasks.

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Requirements

Fast mode requires all of the following:
  • Not available on third-party cloud providers: fast mode is not available on Amazon Bedrock, Google Vertex AI, or Microsoft Azure Foundry. Fast mode is available through the Anthropic Console API and for Claude subscription plans using extra usage.
  • Extra usage enabled: your account must have extra usage enabled, which allows billing beyond your plan’s included usage. For individual accounts, enable this in your Console billing settings. For Team and Enterprise, an admin must enable extra usage for the organization.
Fast mode usage is billed directly to extra usage, even if you have remaining usage on your plan. This means fast mode tokens do not count against your plan’s included usage and are charged at the fast mode rate from the first token.
  • Admin enablement for Team and Enterprise: fast mode is disabled by default for Team and Enterprise organizations. An admin must explicitly enable fast mode before users can access it.
If your admin has not enabled fast mode for your organization, the /fast command will show “Fast mode has been disabled by your organization.”

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Enable fast mode for your organization

Admins can enable fast mode in: Another option to disable fast mode entirely is to set CLAUDE_CODE_DISABLE_FAST_MODE=1. See Environment variables.

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Require per-session opt-in

By default, fast mode persists across sessions: if a user enables fast mode, it stays on in future sessions. Administrators on Team or Enterprise plans can prevent this by setting fastModePerSessionOptIn to true in managed settings or server-managed settings. This causes each session to start with fast mode off, requiring users to explicitly enable it with /fast. 
{
  "fastModePerSessionOptIn": true
}
This is useful for controlling costs in organizations where users run multiple concurrent sessions. Users can still enable fast mode with /fast when they need speed, but it resets at the start of each new session. The user’s fast mode preference is still saved, so removing this setting restores the default persistent behavior.

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Handle rate limits

Fast mode has separate rate limits from standard Opus. Fast mode for Opus 4.6 and Opus 4.7 share the same rate limit pool: usage on either model draws from the same limits. When you hit the fast mode rate limit or run out of extra usage:
  1. Fast mode automatically falls back to standard speed on the same Opus version
  2. The ↯ icon turns gray to indicate cooldown
  3. You continue working at standard speed and pricing
  4. When the cooldown expires, fast mode automatically re-enables
To disable fast mode manually instead of waiting for cooldown, run /fast again.

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Research preview

Fast mode is a research preview feature. This means:
  • The feature may change based on feedback
  • Availability and pricing are subject to change
  • The underlying API configuration may evolve
Report issues or feedback through your usual Anthropic support channels.

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See also