tengu_cobalt_plinth_alder
A Claude Code feature flag, read out of the shipped bundle. It has been in the build since v2.1.239, including the newest one read.
Claude can now read back a published artifact's contents; browsing, multi-file publishing and deletion are built but off.
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.239.
In the changelogs
4Releases whose published page names tengu_cobalt_plinth_alder.
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v2.1.285
Artifact pinning no longer waits on a remote switch
Artifact pinning is now on by default in local sessions, and
CLAUDE_CODE_ARTIFACT_PINstill overrides itgate cited by this entry
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v2.1.247
Artifact delete rewritten around session relaying
Artifact deletes now go through a relay and report unverified responses as unconfirmed rather than deleted.
gate cited by this entry, found in this entry's text
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v2.1.247
Artifact deletion goes through the relay and can refuse in cloud sessions
Artifact deletion now uses a verified relay route and still needs the delete environment variable.
named in this entry, gate cited by this entry, found in this entry's text
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v2.1.239
Artifact tool gains a
readaction, with multi-file browsing and delete built but gated offClaude can now read back a published artifact's contents; browsing, multi-file publishing and deletion are built but off.
gate cited by this entry, found in this entry's text
Gate readings
3| Release | Resolved | This account | Anonymous | Compiled default |
|---|---|---|---|---|
| v2.1.285 read on another version | Off by default, switched on for this account | on | on | off |
| v2.1.247 | Off in both readings | off | off | off |
| v2.1.239 | Not enough to say | no value returned | no value returned | 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 | 2026-10-07T18:00:12Z | 2026-10-22T06:25:04Z | v2.1.292 to v2.1.308 |
| anonymous | no longer carried | 2026-10-17T05:25:57Z | 2026-10-17T05:25:57Z | v2.1.302 |
| anonymous | on | 2026-09-11T15:11:43Z | 2026-10-17T05:10:04Z | v2.1.268 to v2.1.302 |
| this account | off | 2026-10-07T17:59:34Z | 2026-10-07T17:59:34Z | v2.1.293 |
| this account | on | 2026-09-11T15:16:18Z | 2026-10-07T17:10:05Z | v2.1.268 to v2.1.292 |
| this account | off | 2026-09-10T21:47:12Z | 2026-09-11T15:11:43Z | v2.1.268 |
| anonymous | off | 2026-08-25T17:25:05Z | 2026-09-11T14:55:04Z | v2.1.233 to v2.1.268 |
| this account | no longer carried | 2026-09-10T21:46:45Z | 2026-09-10T21:46:45Z | v2.1.268 |
| this account | off | 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 | off | 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 | off | 2026-08-25T19:25:04Z | 2026-09-06T01:55:04Z | v2.1.233 to v2.1.261 |
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_cobalt_plinth_alder was v2.1.247, 26 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
1Build by build
59One 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.