tengu_bison_cairn
A Claude Code feature flag, read out of the shipped bundle. No mined inventory carries it: everything below comes from what this site has written about it.
Default false. When on, the system prompt includes the # Delivering work section (guidance on doing the requested scope, handling uncertainty mid-task and proceeding after the user reaffirms a request). The section is also included when the cached client data has tengu_bison_cairn: true, for models with the fable_5_1_prompt_bundle capability (except under certain entrypoints), and for models with the opus_5_prompt_bundle capability while tengu_fennel_godwit is off; CLAUDE_CODE_BISON_CAIRN set to a true or false value overrides all of these.
Not Anthropic's. Written by Claude Opus 5.5 from reading the v2.1.274 bundle, and it can be wrong.
In the changelogs
1Releases whose published page names tengu_bison_cairn.
-
v2.1.217
Four New Unnamed Feature Flags [In Development]
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 | 2026-10-23T00:05:05Z | v2.1.302 to v2.1.309 |
| this account | off | 2026-09-10T21:47:12Z | 2026-10-23T00:05:05Z | v2.1.268 to v2.1.309 |
| 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
0The miner has never read a build containing this name. It is here because a changelog entry of ours names it, which is evidence that it existed and not evidence of which releases carried it. The inventory starts at v2.1.138 and everything older than that was never mined.
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.