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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 up to 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 with faster responses. Fast mode is supported on Opus 4.8 and Opus 4.7. It is not available on Sonnet, Haiku, or other models.
Fast mode for Opus 4.7 is deprecated as of June 25, 2026, and will be removed on July 24, 2026. After removal, fast mode requests on Opus 4.7 return an error and do not fall back to standard Opus 4.7. Migrate to Opus 4.8 to keep the speedup.
What to know:
  • Use /fast to toggle on fast mode in the Claude Code CLI. Fast mode is not supported in the VS Code extension.
  • Fast mode pricing per MTok input/output is $10/$50 on Opus 4.8 and $30/$150 on 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 usage credits only and not included in the subscription rate limits.

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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 you turn on in an interactive session persists across sessions. In non-interactive mode, with the -p flag, /fast works only in a session launched with fast mode in its --settings value, for example claude -p --settings '{"fastMode": true}'; the toggle then applies to that session only and isn’t saved as your default, and in any other non-interactive session the command reports that fast mode isn’t available. You 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 Opus
  • 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 Opus. The model does not revert to your previous model. To switch to a different model, use /model. Switching to a model that doesn’t support fast mode turns fast mode off. Switching back to a supported Opus model turns it on again when your saved fast mode preference is on, the same preference a new session starts from by default. With per-session opt-in configured, switching back doesn’t turn fast mode on again; run /fast to re-enable it. Fast mode never turns on for a session whose saved preference is off, and the ↯ icon and Fast mode ON confirmation appear whenever it activates. Before v2.1.208, fast mode stayed off after you switched back until you ran /fast again. Opus 4.8 is the fast mode default in Claude Code v2.1.154 and later. On v2.1.142 through v2.1.153, fast mode defaults to Opus 4.7.

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Understand the cost tradeoff

Fast mode has higher per-token pricing than standard Opus, with the multiplier varying by model: Fast mode pricing is flat across the full 1M token context window. For the standard Opus rate to compare against, see the Claude pricing reference. The first time you enable fast mode in a conversation, you pay the full fast mode uncached input token price for the entire conversation context. The deeper into a conversation you are, the more this costs, so enabling fast mode from the start is cheaper. The cost applies once per conversation, so toggling fast mode off and on again later does not repeat it. For the mechanism, see how fast mode interacts with the prompt cache.

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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: 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:
  • Anthropic API or subscription only: fast mode is available through the Anthropic Console API and for Claude subscription plans using usage credits. It is not available on Amazon Bedrock, Google Cloud’s Agent Platform, Microsoft Foundry, or Claude Platform on AWS.
  • Usage credits turned on: your account must have usage credits turned on, which allows billing beyond your plan’s included usage. For individual accounts, turn this on in your Console billing settings. For Team and Enterprise, an admin must turn on usage credits for the organization.
Fast mode usage draws directly from usage credits, 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.
  • Owner enablement for Team and Enterprise: fast mode is disabled by default for Team and Enterprise organizations. An Owner must explicitly enable fast mode before users can access it.
If fast mode has not been enabled for your organization, the /fast command will show “Fast mode has been disabled by your organization.” If your organization’s availableModels allowlist excludes the fast-mode Opus model, /fast is refused with “is not in your organization’s allowed models”. The exception is a session already running on an allowed Opus model that supports fast mode: /fast enables fast mode on your current model instead of switching models.

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Enable fast mode for your organization

Where you enable fast mode depends on which product your organization uses: Another option to disable fast mode entirely is to set CLAUDE_CODE_DISABLE_FAST_MODE=1. See Environment variables.

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Use fast mode behind proxies and LLM gateways

Before offering fast mode, Claude Code checks your organization’s fast mode availability with a request directly to api.anthropic.com. The check doesn’t follow ANTHROPIC_BASE_URL, so on a network that routes Claude traffic through an LLM gateway and blocks direct egress to api.anthropic.com, the check fails even though inference requests work. The check does use a configured HTTP proxy, so a network block fails the check only where api.anthropic.com is unreachable even through the proxy. When the check fails, /fast reports “Fast mode unavailable due to network connectivity issues”, and requests run at standard speed, even when your organization has fast mode enabled. A check that succeeded in the past keeps working from its cached result, so a blocked check mostly affects new installations. The same connectivity message appears on an open network when the check reaches api.anthropic.com but presents a credential Anthropic rejects. A session whose resolved key is a gateway-issued credential, held in ANTHROPIC_API_KEY or produced by an apiKeyHelper, sends the check with that key, and the rejected request is reported as a connectivity failure. To restore fast mode, allowlist direct egress to api.anthropic.com where a network block is the cause, or set whichever variable matches how the check fails:
  • CLAUDE_CODE_SKIP_FAST_MODE_NETWORK_ERRORS=1 treats a failed check as available and still honors a “disabled by your organization” response. Use it when your network refuses the connection, or when Anthropic rejects a gateway credential; allowlisting doesn’t help the credential case, since nothing is blocked.
  • CLAUDE_CODE_SKIP_FAST_MODE_ORG_CHECK=1 skips the check entirely. Use it when your network intercepts the request rather than refusing it.
Two gateway configurations report “Fast mode has been disabled by your organization” rather than the connectivity message, even when your organization has fast mode enabled:
  • A session that authenticates with ANTHROPIC_AUTH_TOKEN alone skips the check: without a claude.ai login or an Anthropic API key, and without a cached successful check, Claude Code treats fast mode as disabled by your organization without sending the request.
  • A proxy that intercepts the check and answers with its own page, for example a TLS-inspecting proxy returning an HTTP 200 block page, is read as a response saying your organization has fast mode disabled.
In both cases, set CLAUDE_CODE_SKIP_FAST_MODE_ORG_CHECK=1 to restore fast mode. CLAUDE_CODE_SKIP_FAST_MODE_NETWORK_ERRORS doesn’t apply to either case, since it only bypasses failed checks and both of these produce a disabled response instead. Allowlisting direct egress doesn’t help the bearer-token case, which never sends the request. The variables affect only the client-side check. When your organization has fast mode disabled, the API rejects fast mode requests whether or not they’re set. Setting CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC also suppresses the availability check. Without a previously cached successful check, /fast reports “Fast mode is currently unavailable”; both skip variables restore fast mode in that configuration too.

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Require per-session opt-in

By default, fast mode a user turns on in an interactive session persists across sessions: it stays on in future sessions. To change this, set fastModePerSessionOptIn to true in any settings file, which causes each session to start with fast mode off and requires users to explicitly enable it with /fast. Owners on Team or Enterprise plans can deploy it organization-wide through server-managed settings.
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 on Opus 4.8 and Opus 4.7 shares the same rate limit pool: usage on either of them draws from the same limits. When you hit the fast mode rate limit or run out of usage credits:
  1. Fast mode automatically falls back to standard speed
  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