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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_bg_retire_grace_bridged_min

A Claude Code feature flag, read out of the shipped bundle. It has been in the build since v2.1.149, including the newest one read.

What it is

A prompt-and-context experiment switch was renamed and four other switches disappeared entirely.

Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.246.

Presence across releases

ReleasesReadingDeclared typeDefault
2.1.245 – 2.1.250 5 releases never mined — —
2.1.149 – 2.1.243 84 releases in the build — number

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

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. v2.1.246Prompt and context experiment renamed to tengu_expressive_whistle, four other switches retired

    A prompt-and-context experiment switch was renamed and four other switches disappeared entirely.

    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, up to twelve of them.

tengu_bg_adopt_upgrade_respawnBackground sessions stop needlessly restarting when your running build is already newer. never mined tengu_bg_attach_outcomeBackground attach events now record cold starts, surface and first frame details. never mined tengu_bg_attach_stall_msNo description from anybody. 2.1.138 tengu_bg_attach_upgradeNo description from anybody. 2.1.162 tengu_bg_binary_takeoverThe background daemon can now retire a same-version instance; build is 2.1.248. 2.1.152 tengu_bg_classifier_configNo description from anybody. 2.1.138 tengu_bg_daemon_binary_takeoverThe background daemon can now retire a same-version instance; build is 2.1.248. never mined tengu_bg_daemon_spawn_failedNo description from anybody. 2.1.138 tengu_bg_daemon_spawn_reinstall_waitStarting the background helper during an npm reinstall now waits and retries instead of failing. never mined tengu_bg_dispatch_fallbackBackground dispatch failures now distinguish a daemon that started but couldn't launch Claude Code. never mined tengu_bg_dispatch_rejectedThe background daemon now records why it refused a queued dispatch file. never mined tengu_bg_imark_malformedBackground sessions now send readiness marks so attaching knows when a session is actually interactive. never mined

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.