tengu_sable_thrush
A Claude Code feature flag, read out of the shipped bundle. It was in the build from v2.1.240 and was gone by v2.1.251.
Claude Code now spots server-tagged narration thinking, but the display change stays off by default.
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.240.
In the changelogs
5Releases whose published page names tengu_sable_thrush.
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v2.1.251
Startup telemetry reports Remote Control availability, drops an old experiment
Startup telemetry now reports Remote Control availability and an old experiment field was dropped.
gate cited by this entry, found in this entry's text
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v2.1.248
VSCode gate snapshot loads one gate lazily
The VSCode extension's gate summary resolves one check later; reported gates are unchanged.
gate cited by this entry, found in this entry's text
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v2.1.241
Narration gate state now reported to the VS Code extension
A narration-summary feature can be forced on with an env var, but it's off by default here.
gate cited by this entry, found in this entry's text
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v2.1.240
Server-tagged "narration" thinking blocks, counted now and rendered as "(summarized)" later
Claude Code now spots server-tagged narration thinking, but the display change stays off by default.
gate cited by this entry, found in this entry's text
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v2.1.240
Thinking display modes gated behind a server-side model capability
Claude Code can present thinking as connector text only, but nothing enables it here.
gate cited by this entry, found in this entry's text
Gate readings
4| Release | Resolved | This account | Anonymous | Compiled default |
|---|---|---|---|---|
| v2.1.251 | On for this account, and not off by default | on | on | not a boolean we can read |
| v2.1.248 | Off by default, switched on for this account | on | on | off |
| v2.1.241 | Off by default, switched on for this account | on | on | off |
| v2.1.240 | 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
14| Read as | Reading | From | Until | Version installed |
|---|---|---|---|---|
| anonymous | on | 2026-10-17T05:30:04Z | 2026-10-22T06:25:04Z | v2.1.302 to v2.1.308 |
| this account | on | 2026-09-10T21:47:12Z | 2026-10-22T06:25:04Z | v2.1.268 to v2.1.308 |
| anonymous | no longer carried | 2026-10-17T05:25:57Z | 2026-10-17T05:25:57Z | v2.1.302 |
| anonymous | on | 2026-08-21T21:35:04Z | 2026-10-17T05:10:04Z | v2.1.233 to v2.1.302 |
| this account | no longer carried | 2026-09-10T21:46:45Z | 2026-09-10T21:46:45Z | v2.1.268 |
| this account | on | 2026-09-08T20:36:15Z | 2026-09-10T17:40:05Z | v2.1.263 to v2.1.267 |
| this account | no longer carried | 2026-09-08T20:34:58Z | 2026-09-08T20:34:58Z | v2.1.265 |
| this account | on | 2026-09-06T02:40:05Z | 2026-09-08T18:45:05Z | v2.1.261 to v2.1.263 |
| this account | no longer carried | 2026-09-06T02:36:19Z | 2026-09-06T02:36:19Z | v2.1.263 |
| this account | on | 2026-08-21T21:40:04Z | 2026-09-06T01:55:04Z | v2.1.233 to v2.1.261 |
| this account | off | 2026-08-16T19:25:05Z | 2026-08-21T21:35:04Z | v2.1.233 |
| anonymous | off | 2026-08-19T04:25:04Z | 2026-08-21T21:15:04Z | v2.1.233 |
| anonymous | no longer carried | 2026-08-19T04:20:14Z | 2026-08-19T04:20:14Z | v2.1.233 |
| anonymous | off | 2026-08-16T19:05:05Z | 2026-08-19T03:45:04Z | v2.1.233 |
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
3The earliest release whose published evidence quoted tengu_sable_thrush was v2.1.241, 22 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.
Presence across releases
2Build by build
58One 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.