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Sweep 22 Oct 2026 · 04:32Z Build v2.1.308 527 read Stable v2.1.308 Latest v2.1.308 Next v2.1.308 Feeds RSS JSON llms.txt llms-full.txt Unofficial
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Claude Code v2.1.286 ·

Fast mode handles models that reject it, with a notice when it falls back

When a model rejects fast mode, Claude Code now uses standard speed for that model for the session and shows a warning

Group of 4 You'll notice Improvements
JSON All of v2.1.286
You'll noticeTier: how much it should matter to you
3Useful: my rating, 1 to 5
1Signal: worth watching, 1 to 5
ModelsArea: what it touches
ImprovementsKind: in v2.1.286,
ImprovementsSection of the release

Unclear It is not clear what the fast mode check does once it runs.

What

Fast mode makes Claude respond faster on models that support it. This release changes what happens when the model in use does not accept it.

  • When fast mode is rejected for a fallback model (a model used in place of the one you picked), Claude Code remembers this for the session and uses standard speed for that model. The fast mode state and the labels in the model picker now check this model by model.
  • A warning appears straight away: "Using standard speed on · fast mode wasn't available". Before, the switch to standard speed was not announced.
  • In remote sessions, a report that fast mode is off because of model_not_allowed is now ignored instead of changing the fast mode state.
  • When a controlling program sets fastMode to true through apply_flag_settings and the model changes too, or the current settings disagree, a fast mode check now runs after the settings are applied. Before, it only replied to the request.

Why

If your model cannot use fast mode, you now see why Claude Code dropped to standard speed, and it stops retrying fast mode for that model during the session.

Read from
Names in the bundleapply_flag_settingsfastMode
What the documentation says
Documented inclaude-code/hooks
Since it was published

The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.

Confirmed since Anthropic's documentation has since written up fastMode, on Speed up responses with fast mode. > * **Fast mode turned off by managed settings**: if your organization deploys [managed settings](/docs/en/managed-settings) that set [`fastMode: false`](/docs/en/settings-reference#fastmode), turning fast mode on with `/fast` shows the sa… fast-mode see the edit
How sure we are
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubtIt is not clear what the fast mode check does once it runs.
Anthropic's documentation agreesAnthropic's documentation has since written up fastMode, on Speed up responses with fast mode.

See this entry in the whole of v2.1.286 →

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