tengu_functional_flute
A Claude Code feature flag, read out of the shipped bundle. It has been in the build since v2.1.323, including the newest one read.
When fetching attachments ahead of time in remote sessions, Claude Code can also download a second copy meant for the model, behind a remote switch
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.323.
In the changelogs
1Releases whose published page names tengu_functional_flute.
-
v2.1.323
Remote attachments can also be downloaded as a separate copy for Claude
When fetching attachments ahead of time in remote sessions, Claude Code can also download a second copy meant for the model, behind a remote switch
gate cited by this entry
Gate readings
1| Release | Resolved | This account | Anonymous | Compiled default |
|---|---|---|---|---|
| v2.1.323 read on another version | Off by default, switched on for this account | on | on | off |
Two arms, because they disagree: this account is the one account this site reads and anonymous is a baseline with no identity attached. A reading says nothing about your account, and off cannot rule out a rollout both readings sit outside of. What these readings can and cannot show.
Flag server, over time
4| Read as | Reading | From | Until | Version installed |
|---|---|---|---|---|
| this account | on | 2026-11-12T16:55:05Z | 2026-11-13T02:10:04Z | v2.1.322 to v2.1.323 |
| anonymous | on | 2026-11-12T16:35:04Z | 2026-11-13T02:10:04Z | v2.1.322 to v2.1.323 |
| this account | off | 2026-11-10T18:40:05Z | 2026-11-12T16:40:06Z | v2.1.322 |
| anonymous | off | 2026-11-10T16:40:04Z | 2026-11-12T16:30:06Z | v2.1.322 |
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.
First cited
1The earliest release whose published evidence quoted tengu_functional_flute was v2.1.323, 12 Nov 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.
Presence across releases
1Build by build
1One 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.