Fast Mode Model Scope Narrowed / Claude Code v2.1.196

Fast mode (Opus with faster output, toggled with /fast) is now documented as available on Opus 4.8 and 4.7 only — Opus 4.6 has been removed from the list. Opus 4.7 fast mode is additionally flagged as deprecated with a removal date.

Details

Fast-mode eligibility (ig()) passes if the catalog fast_mode capability is set on the resolved model, or if the lowercase model ID contains opus-4-7 or opus-4-8; the previous opus-4-6 string match has been removed.
Fast mode is restricted to the first-party Anthropic API (uc() returns false for Bedrock, Vertex, and other providers); toggling on any other provider returns "Fast mode is only available when using the Anthropic API directly".
When toggled ON, the active fast-mode model resolves via alias "opus" (or "opus[1m]" for 1M context); iW() returns the display name "Opus 4.8" for the confirmation message.
The Opus 4.7 deprecation notice fires only when the currently active model resolves to claude-opus-4-7. The removal date is read from the tengu_sunset_penguin_opus47 GrowthBook flag (default "2026-07-25"); if the date has already passed or is unparseable, no notice is shown.
The deprecation notice (SGo()) carries priority: "immediate" and color: "warning", surfacing immediately on the next fast-mode toggle rather than as a background notification.

Evidence

Updated fast mode tip (search for "available on Opus 4.8/4.7.") and deprecation logic (search for "opus47-fast-mode-deprecation" and "tengu_sunset_penguin_opus47")

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

Read from

Feature flag

tengu_sunset_penguin_opus47 Not enough to say

Nothing here resolved what this flag was doing on this version, so nothing here should be read as on or off.

This account: no value returned · anonymous baseline: no value returned · compiled default in v2.1.196: not a boolean we can read

These values were read against a different version of Claude Code, so treat them as the nearest reading available instead of one taken on this release.

Read once, for one account on one subscription tier, against v2.1.196. It isn't a statement about your account. What a flag value here can and cannot tell you

How sure we are

One source agreesOne thing we can check says the same as this entry.

The name it cites is new in this buildNew in this build: tengu_sunset_penguin_opus47

See this entry in the whole of v2.1.196 →

The build it came inv2.1.196

29 Jun 2026 · 21 entries, this one is #17.

Either side of it

v2.1.195Older
v2.1.197Newer

Open the release →

Names in this entry

slash/fast
Toggle fast mode on or off. Run it while Claude is responding and Claude Code toggles fast mode without waiting for the turn to end, though the running turn finishes at its original speed. Before v2.1.242, Claude Code decided from a feature flag it fetched from Anthropic whether to run the command mid-turn or queue it until the turn finished, and always queued it in a session that doesn't fetch feature flags. Availability in non-interactive mode with -p is limited; see Toggle fast mode. Requires Claude Code v2.1.205 or later
settingopus
Opus 5 is now the default Opus, with a 1M-context option in the model picker.
modelclaude-opus-4-7
Opus 5 is now the default Opus, with a 1M-context option in the model picker.
flagtengu_sunset_penguin_opus47
Default "2026-07-25". Removal date for Opus 4.7 fast mode: when fast mode is turned on (via /fast or the picker) while the current model is claude-opus-4-7 and the date is still in the future, a warning notice Opus 4.7 fast mode is deprecated and will be removed on <date> appears, with the date shown like Jul 25 in UTC. An unparseable or past date shows no notice.

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