tengu_luminous_whistle

A Claude Code feature flag, read out of the shipped bundle. It was in the build from v2.1.251 and was gone by v2.1.280.

Releases whose published page names tengu_luminous_whistle.

1. v2.1.251 28 Aug 2026
   Keeping another vendor's thinking text across a model upgrade

   Reasoning text from a non-Claude model can survive a model switch, off unless enabled.

   gate cited by this entry, found in this entry's text

No release here has a gate table behind it for this flag. Most published releases have none at all: the readings exist only for versions the pipeline captured flag state on.

One row per unbroken stretch of one reading, newest first, from snapshots taken every twenty-five minutes or so. No longer carried is not off: it means the flag server stopped returning the gate at all, which is what a retired experiment looks like. The version column is what was installed when the reading was taken, not what caused it.

The earliest release whose published evidence quoted tengu_luminous_whistle was v2.1.251, 28 Aug 2026. That is the oldest release this project wrote about it, so it is a floor on the name's age and not the release that introduced it. It is not a presence reading: which builds carried the name is the table below.

One row per release since the first build this name was read out of. Absent means the build was read and the name was not in it, never mined means no bundle for that release was ever archived, and a declared type or a default is only ever what that release's own bundle stated.

Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the feature flag does. All feature flags.