Name Space in /fast footer

Toggle fast mode

In the CLI, toggle fast mode in either of these ways:

• Run /fast, press Space to toggle on or off, then press Enter to confirm
• Set "fastMode": true in your user settings file

By default, fast mode you turn on in an interactive session persists across sessions. You can configure fast mode to reset each session. See require per-session opt-in for details.

Outside a cloud session, 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. The -p form requires Claude Code v2.1.205 or later. Elsewhere in non-interactive mode, the command reports that fast mode isn't available.

You can run /fast while Claude is working, and Claude Code toggles fast mode without waiting for the turn to end. Claude Code finishes the running turn at its original speed, so the speed change takes effect from your next turn. If your current model doesn't support fast mode, turning it on also switches your model, and Claude Code uses the new model from its next request in that turn.

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 your current model doesn't support fast mode, Claude Code 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

Opus 5.5 is the fast mode default in Claude Code v2.1.280 and later. Before v2.1.280, fast mode defaulted to Opus 5 from v2.1.219, to Opus 4.8 on v2.1.154 through v2.1.218, and to Opus 4.7 on v2.1.142 through v2.1.153.

When you disable fast mode with /fast again, you remain on Opus. To switch to a different model, use /model.

Switch models while fast mode is on

Fast mode follows your model switches in both directions:

• Switch away: when you switch to a model that doesn't support fast mode, Claude Code turns fast mode off. This includes Opus 4.7; before v2.1.221, fast mode stayed on after a switch to Opus 4.7 and the API rejected the requests.
• Switch back: switching back to a supported Opus model turns fast mode on again when your saved fast mode preference is on, the same preference a new session starts from by default. A model switch never turns fast mode on for a session whose saved preference is off, and with per-session opt-in configured, switching back doesn't turn it on either; run /fast to re-enable it.

Whenever a model switch turns fast mode on or off, Claude Code shows a Fast mode ON or Fast mode OFF confirmation, and the ↯ icon appears while fast mode is on. This holds whether you switch with /model, with /config model=<model>, or from a device connected through Remote Control.

Claude Code resends the session's fast mode status to devices connected through Remote Control after a model switch, a reconnection, or a failed availability check.

Use fast mode in cloud sessions

Fast mode works in cloud sessions when it's available on your account, whether the session runs on Anthropic-managed infrastructure or a self-hosted runner. Requires Claude Code v2.1.271 or later in the session's environment.

Type /fast on in the session to turn fast mode on. It stays on for that session only and isn't saved as your default. The requirements apply in cloud sessions too.