Source Intelligence
Follow Discord
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_bg_attach_outcome

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.

What it is

Background attach events now record cold starts, surface and first frame details.

Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.221.

Presence across releases

The 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.

Gate readings

No release here has a gate table behind it for this flag. Most published releases have none at all: the readings exist only for versions the pipeline captured flag state on.

Changelog entries naming it

  1. v2.1.227Recovered background attaches report the same way on both code paths

    Recovered background attaches report identically whether found by the old or new sweep.

    gate cited by this entry

  2. v2.1.221Background attach telemetry gets cold-start and surface dimensions

    Background attach events now record cold starts, surface and first frame details.

    gate cited by this entry

  3. v2.1.221Background-attach outcomes are journaled to disk and recovered later

    Background session attaches now write a small journal file so crashed attaches still report what happened later.

    gate cited by this entry

  4. v2.1.221Much richer background-attach timing telemetry

    Attaching to a background session now records detailed timing, including a 30-second timeout flag.

    gate cited by this entry

  5. v2.1.221claude attach now measures time-to-interactive

    Attaching to a background session now times how long it takes to paint and reach an idle prompt.

    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_bg_attach, up to twelve of them.

tengu_bg_attach_stall_msNo description from anybody. 2.1.138 tengu_bg_attach_upgradeNo description from anybody. 2.1.162

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.