tengu_nimble_wren
A Claude Code feature flag, read out of the shipped bundle. It has been in the build since v2.1.300, including the newest one read.
The built-in web-fetch helper now uses Haiku when certain model and provider checks pass, and is told not to retry sites that refuse it
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.300.
In the changelogs
2Releases whose published page names tengu_nimble_wren.
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v2.1.302
The exploring subagent can now use Haiku in remote sessions
A built-in exploring agent can now run on the smaller Haiku model in remote sessions, not just in the situations it could before
gate cited by this entry
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v2.1.300
The built-in web-fetch helper can run on the Haiku model
The built-in web-fetch helper now uses Haiku when certain model and provider checks pass, and is told not to retry sites that refuse it
gate cited by this entry
Gate readings
2| Release | Resolved | This account | Anonymous | Compiled default |
|---|---|---|---|---|
| v2.1.302 read on another version | Not enough to say | no value returned | no value returned | on |
| v2.1.300 read on another version | Not enough to say | no value returned | no value returned | on |
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.
First cited
3The earliest release whose published evidence quoted tengu_nimble_wren was v2.1.300, 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
9One 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.