tengu_mossy_lantern
A Claude Code feature flag, read out of the shipped bundle. It was in the build from v2.1.257 and was gone by v2.1.269.
Tools added or removed mid-conversation can be surfaced to the model, but the beta capability is gated off by default.
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.257.
In the changelogs
1Releases whose published page names tengu_mossy_lantern.
-
v2.1.257
Mid-conversation tool-change surfacing to the model, gated off by default
Tools added or removed mid-conversation can be surfaced to the model, but the beta capability is gated off by default.
gate cited by this entry
Gate readings
0No 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.
Flag server, over time
12| Read as | Reading | From | Until | Version installed |
|---|---|---|---|---|
| anonymous | on | 2026-10-17T05:30:04Z | 2026-10-22T09:55:05Z | v2.1.302 to v2.1.308 |
| this account | on | 2026-09-10T21:47:12Z | 2026-10-22T09:55:05Z | 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 | 2026-09-08T20:34:58Z | 2026-10-17T05:10:04Z | v2.1.265 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 | 2026-09-08T20:55:05Z | 2026-09-10T17:40:05Z | v2.1.265 to v2.1.267 |
| this account | off | 2026-09-08T20:36:15Z | 2026-09-08T20:45:05Z | v2.1.263 to v2.1.265 |
| 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 |
| anonymous | off | 2026-09-02T23:25:05Z | 2026-09-08T18:45:05Z | v2.1.259 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 | 2026-09-02T23:35:04Z | 2026-09-06T01:55:04Z | v2.1.259 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
0No release's published evidence quotes this name. The ledger indexes the Evidence lines of every changelog on this site, so this says nobody here has ever quoted it; it says nothing about how old the name is.
Presence across releases
2Build by build
47One 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.