tengu_heron_tallow
A Claude Code feature flag, read out of the shipped bundle. It was in the build from v2.1.217 and was gone by v2.1.229.
Default false. Changes the hint added when the model calls a tool that is not available: for a known tool it reads <tool> is disabled for this session, in subagents as well as here. instead of exists but is not enabled in this context, and for Glob or Grep when Bash is also unavailable it reads <tool> is disabled for this session. CLAUDE_CODE_HERON_TALLOW turns on the same wording.
Not Anthropic's. Written by Claude Opus 5.5 from reading the v2.1.228 bundle, and it can be wrong.
In the changelogs
1Releases whose published page names tengu_heron_tallow.
-
v2.1.217
tengu_heron_tallow— New Feature Gate [Feature-Flagged]gate cited by this entry, found in this entry's text
Gate readings
1| Release | Resolved | This account | Anonymous | Compiled default |
|---|---|---|---|---|
| v2.1.217 read on another version | Off in both readings | off | off | not a boolean we can read |
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
12| Read as | Reading | From | Until | Version installed |
|---|---|---|---|---|
| anonymous | off | 2026-10-17T05:30:04Z | 2026-10-22T09:55:05Z | v2.1.302 to v2.1.308 |
| this account | off | 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 | off | 2026-08-19T04:25:04Z | 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 | 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 | 2026-08-14T22:10:05Z | 2026-09-06T01:55:04Z | v2.1.232 to v2.1.261 |
| anonymous | no longer carried | 2026-08-19T04:20:14Z | 2026-08-19T04:20:14Z | v2.1.233 |
| anonymous | off | 2026-08-14T22:10:05Z | 2026-08-19T03:45:04Z | v2.1.232 to 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
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
4Build by build
80One 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.