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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 Sorting the findings · 1/4 steps 470 findings $18.91 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_bg_adopt_upgrade_respawn

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 sessions stop needlessly restarting when your running build is already newer.

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

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. v2.1.219Background sessions no longer respawn when the running one is newer

    Background sessions stop needlessly restarting when your running build is already newer.

    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_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 tengu_bg_leftarrow_inprocessBackgrounding no longer claims artifact comment monitors will stop; it says they keep auto-replying here. 2.1.138

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.