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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 v2.1.251 Feeds RSS JSON llms.txt
Reading a new release v2.1.251 Analysing changes · 2/5 Deeper second pass · 0/5 agents 427 findings $12.75 so far

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_copper_fox

A Claude Code feature flag, read out of the shipped bundle. It was in the build from v2.1.138 and was gone by v2.1.232.

What it is

Forked subagents are on by default in interactive sessions; set CLAUDE_CODE_FORK_SUBAGENT to false to opt out.

Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.232.

Presence across releases

ReleasesReadingDeclared typeDefault
2.1.245 – 2.1.250 5 releases never mined — —
2.1.232 – 2.1.243 12 releases not in the build — —
2.1.157 – 2.1.231 66 releases in the build — unknown
2.1.138 – 2.1.156 17 releases in the build — bool:false

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
v2.1.232 read on another version Off in both readings off off not a boolean we can read
v2.1.213 read on another version Off in both readings off off not a boolean we can read
v2.1.117 read on another version Off in both readings off off no gate table built for this version

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. v2.1.232Forked subagents are on by default

    Forked subagents are on by default in interactive sessions; set CLAUDE_CODE_FORK_SUBAGENT to false to opt out.

    gate cited by this entry

  2. v2.1.213SessionStart Hook: fork Source Value

    gate cited by this entry

  3. v2.1.117/fork Command

    gate cited by this entry

  4. v2.1.117Fork Subagent Feature Gate [Gradual Rollout]

    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_copper, up to twelve of them.

tengu_copper_kestrelNo description from anybody. 2.1.234 tengu_copper_lanternNo description from anybody. 2.1.138 tengu_copper_thistleThe status line always calls MCP background work a "task" instead of sometimes saying "job". 2.1.161

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.