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Sweep 28 Aug 2026 · 00:00Z Build v2.1.250 478 read Stable v2.1.236 Latest v2.1.250 Next v2.1.250 Feeds RSS JSON llms.txt

DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

Reference / Feature flags

tengu_heron_brook

A Claude Code feature flag, read out of the shipped bundle. It has been in the build since v2.1.150, including the newest one read.

What it is

On some models Claude will stop spinning up subagents or research workflows unless you actually ask for it.

Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.219.

Presence across releases

ReleasesReadingDeclared typeDefault
2.1.245 – 2.1.250 5 releases never mined — —
2.1.150 – 2.1.243 83 releases in the build — string

A row reading never mined is a release with no archived bundle behind it. Nothing was read out of it, so nothing here says whether the name was in it. A declared type or a default is only ever what that release's own bundle stated.

Gate readings

ReleaseResolvedThis accountAnonymousCompiled default
v2.1.219 read on another version Not enough to say no value returned no value returned 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.

Changelog entries naming it

  1. v2.1.219Opus 5 carries an extra system-prompt block and suppresses subagent nudges

    On some models Claude will stop spinning up subagents or research workflows unless you actually ask for it.

    gate cited by this entry

  2. v2.1.219Opus 5 gets an extra system-prompt instruction restricting AgentTool, workflows and deep-research

    On Opus 5, Claude is told not to spawn subagents, workflows or deep research unless you ask.

    gate cited by this entry

Documentation pages

None of Anthropic's documentation pages this site has a copy of carries this name.

Names beside it

Every feature flag in the inventory starting tengu_heron, up to twelve of them.

tengu_heron_brook_appliedOn some models Claude will stop spinning up subagents or research workflows unless you actually ask for it. never mined tengu_heron_tallowNo description from anybody. 2.1.217

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.