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DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

← All of v2.1.68 Home All releases ←olderv2.1.67 v2.1.69newer→
Claude Code v2.1.68

Ultrathink keyword re-enabled as effort boost

Feature flag
tengu_turtle_carbon On for this account, and not off by default

The flag server returned on for the one account this site reads, and nothing in this release compiles it off by default. The compiled default is shown below, and says which it is when we cannot read one: a fifth of gates compile in a string or a number rather than on or off, and most published releases have no gate table behind them at all. No client can see what the server returns for your account.

This account: on · anonymous baseline: on · compiled default in v2.1.68: no gate table built for this version

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 v2.1.68. It isn't a statement about your account. What a flag value here can and cannot tell you

What

Typing "ultrathink" in a message now sets reasoning effort to "high" for that turn. In the previous version, ultrathink was deprecated and showed a dismissive message — it now has real functionality again.

Usage
ultrathink about the architecture of this codebase and suggest improvements
Details
  • When "ultrathink" appears anywhere in your message, effort is automatically set to high for that turn
  • A notification briefly displays: "Effort set to high for this turn"
  • The word "ultrathink" is rendered with a rainbow color shimmer effect in the terminal (cycling through red, orange, yellow, green, blue, indigo, and violet)
  • Controlled by the tengu_turtle_carbon feature flag (defaults to enabled)
  • Replaces the old "Ultrathink no longer does anything. Thinking budget is now max by default." deprecation message
Evidence

Ultrathink effort injection (search for "ultrathink_effort") — rqY() at line ~290076 checks jd() ("tengu_turtle_carbon") and Vf7() (/\bultrathink\b/i)

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

Related

Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.

See this entry in the whole of v2.1.68 →