tengu_mossy_wirth
A Claude Code feature flag, read out of the shipped bundle. It has been in the build since v2.1.299, including the newest one read.
Reading project files can return an uploaded PDF or Word file itself, and writes can check a version first; both are off unless switched on remotely
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.299.
In the changelogs
2Releases whose published page names tengu_mossy_wirth.
-
v2.1.299
Project files can be read as original documents and written with a version check
Reading project files can return an uploaded PDF or Word file itself, and writes can check a version first; both are off unless switched on remotely
gate cited by this entry
-
v2.1.299
Project tools can fetch original uploads and refuse writes to changed documents
Project tools gain an option to read an upload's original file and a version check that refuses outdated writes, behind a remote switch
gate cited by this entry
Gate readings
1| Release | Resolved | This account | Anonymous | Compiled default |
|---|---|---|---|---|
| v2.1.299 read on another version | Off in both readings | off | off | 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 |
|---|---|---|---|---|
| anonymous | off | 2026-10-17T05:30:04Z | 2026-10-22T05:30:05Z | v2.1.302 to v2.1.308 |
| this account | off | 2026-10-09T17:21:03Z | 2026-10-22T05:30:05Z | v2.1.296 to v2.1.308 |
| anonymous | no longer carried | 2026-10-17T05:25:57Z | 2026-10-17T05:25:57Z | v2.1.302 |
| anonymous | off | 2026-10-09T17:00:07Z | 2026-10-17T05:10:04Z | v2.1.295 to v2.1.302 |
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_mossy_wirth was v2.1.299, 14 Oct 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
10One 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.