Source Intelligence

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.

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Claude Code v2.1.174

Opus 4.6 Sunset Date Notification

Feature flag
tengu_sunset_penguin_opus46 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 v2.1.174: 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 v2.1.174. It isn't a statement about your account. What a flag value here can and cannot tell you

A new function checks whether the active model is claude-opus-4-6 and, if so, reads the sunset date from the tengu_sunset_penguin_opus46 feature flag (default: June 29, 2026). If the date has not yet passed, users will see a notification about the upcoming model retirement.

Evidence

Sunset date string (search for "2026-06-29" and "tengu_sunset_penguin_opus46")

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

See this entry in the whole of v2.1.174 →