Speed up responses with fast mode changedfast-mode
Nearest release: v2.1.319, published 2 hours before upstream edited the page. Shown because the two are within 24 hours of each other. Nothing here says the release caused the edit.
Upstream edited this page at 6 Nov 2026 03:39 UTC, give or take a minute or two: the time comes from Anthropic’s own sitemap rather than from a commit. This site recorded the change at 6 Nov 2026 04:07 UTC.
Upstream edited
Recorded here
Lines+6added
Lines−6removed
From line
31
where the diff opens
First seen
14 Aug 2026
this site's first read of the page
Recorded edits28to this page, all time
The whole hunk
from line 31, old and new numbered
/
from line 31
3131In the CLI, toggle fast mode in either of these ways:
3232
3333* Run `/fast`, press Space to toggle on or off, then press Enter to confirm
34* Set `"fastMode": true` in your [user settings file](https://code.claude.com/docs/en/settings.md)
34* On a model that supports fast mode, set `"fastMode": true` in your [user settings file](https://code.claude.com/docs/en/settings.md). If you set it on any other model, you stay on that model with fast mode off.
3535
36By 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](#require-per-session-opt-in) for details.
36By default, fast mode you turn on in an interactive session persists across sessions on a supported model. You can configure fast mode to reset each session. See [require per-session opt-in](#require-per-session-opt-in) for details.
3737
3838Outside a [cloud session](#use-fast-mode-in-cloud-sessions), in [non-interactive mode](https://code.claude.com/docs/en/headless.md) with the `-p` flag, `/fast` works only in a session launched with fast mode in its [`--settings`](https://code.claude.com/docs/en/cli-reference#cli-flags) 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.
3939
from line 41
4141
4242For the best cost efficiency, enable fast mode at the start of a session rather than switching mid-conversation. See [understand the cost tradeoff](#understand-the-cost-tradeoff) for details.
4343
44When you enable fast mode:
44When you enable fast mode with `/fast`:
4545
4646* If your current model doesn't support fast mode, Claude Code switches to Opus
4747* You'll see a confirmation message: "Fast mode ON"
from line 192
192192
193193### Require per-session opt-in
194194
195By default, fast mode a user turns on in an interactive session persists across sessions. To change this, set `fastModePerSessionOptIn` to `true` in any [settings file](https://code.claude.com/docs/en/settings.md#where-settings-live), which causes each session to start with fast mode off and requires users to explicitly enable it with `/fast`. Owners on [Team](https://claude.com/pricing?utm_source=claude_code\&utm_medium=docs\&utm_content=fast_mode_teams#team-&-enterprise) or [Enterprise](https://anthropic.com/contact-sales?utm_source=claude_code\&utm_medium=docs\&utm_content=fast_mode_enterprise) plans can deploy it organization-wide through [server-managed settings](https://code.claude.com/docs/en/server-managed-settings.md).
195By default, fast mode a user turns on in an interactive session persists across sessions on a supported model. To change this, set `fastModePerSessionOptIn` to `true` in any [settings file](https://code.claude.com/docs/en/settings.md#where-settings-live), which causes each session to start with fast mode off and requires users to explicitly enable it with `/fast`. Owners on [Team](https://claude.com/pricing?utm_source=claude_code\&utm_medium=docs\&utm_content=fast_mode_teams#team-&-enterprise) or [Enterprise](https://anthropic.com/contact-sales?utm_source=claude_code\&utm_medium=docs\&utm_content=fast_mode_enterprise) plans can deploy it organization-wide through [server-managed settings](https://code.claude.com/docs/en/server-managed-settings.md).
196196
197197```json theme={null}
198198{
from line 217
217217
218218If you run out of usage credits mid-session, Claude Code retries each rejected fast mode request at standard speed and pricing, so you keep working, and there is no cooldown. How you see the rejection depends on the session type:
219219
220* In an interactive session, Claude Code shows a "Fast mode disabled · usage credits exhausted" notification and turns fast mode off for the rest of the session. Your saved fast mode preference doesn't change; run `/fast` to turn fast mode back on.
220* In an interactive session, Claude Code shows a "Fast mode disabled · Out of usage credits" notification and turns fast mode off. Your saved fast mode preference doesn't change; run `/fast` to turn fast mode back on.
221221* In [non-interactive mode](https://code.claude.com/docs/en/headless.md) with `--output-format stream-json`, and through the Agent SDK, Claude Code emits the same text on the message stream as a `system` message with subtype `notification`, once per turn while you're out of usage credits. Fast mode stays on. Requires Claude Code v2.1.221 or later.
222222
223223## Research preview
No line in this hunk matches that.