tengu_tool_detach
A Claude Code feature flag, read out of the shipped bundle. It has been in the build since v2.1.277, including the newest one read.
A long-running tool call can now be moved to the background instead of blocking when a new message comes in
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.277.
In the changelogs
3Releases whose published page names tengu_tool_detach.
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v2.1.287
Tool calls moved to the background can no longer stop to ask you questions
A tool call moved to the background can no longer ask you a question later, and headless sessions can move tool calls to the background
gate cited by this entry
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v2.1.277
Long-running tool calls can now detach to the background when a new message arrives
A long-running tool call can now be moved to the background instead of blocking when a new message comes in
gate cited by this entry
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v2.1.277
Tool calls can now be 'detached' to background mid-flight to let queued messages through
A running tool call can now be detached to the background so a queued message can go through, tracked via telemetry
gate cited by this entry
Gate readings
2| Release | Resolved | This account | Anonymous | Compiled default |
|---|---|---|---|---|
| v2.1.287 read on another version | Not enough to say | no value returned | no value returned | on |
| v2.1.277 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
1The earliest release whose published evidence quoted tengu_tool_detach was v2.1.277, 18 Sep 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
41One 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.