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Sweep 22 Oct 2026 · 04:32Z Build v2.1.308 527 read Stable v2.1.308 Latest v2.1.308 Next v2.1.308 Feeds RSS JSON llms.txt llms-full.txt Unofficial

Claude Code v2.1.221 ·

Much richer background-attach timing telemetry

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

Under the hood Internal Changes
JSON All of v2.1.221
Under the hoodTier: how much it should matter to you
2Useful: my rating, 1 to 5
0Signal: worth watching, 1 to 5
SessionsArea: what it touches
Internal ChangesKind: in v2.1.221,
Internal ChangesSection of the release
What

tengu_bg_attach_outcome gains a large set of timing and content fields, purely observational.

Details
  • New fields: attach_ms, content_paint_ms, prompt_idle_ms, timed_out, attach_censored, marks_expected, first_frame_kind ("real", "dimhint", "unknown"), surface, daemon_booted, attach_cold, msgs_loaded, msgs_in_jsonl and msgs_rendered_at_first_paint.
  • Measured from a caller-supplied t0, with a 30s watchdog that flags a timeout when no paint marks arrive.
  • The same fields are now attached to the connect-throw error path, failure_class connect_throw, and to detach and error results.
  • None of these field names exist in 2.1.220.
Evidence

attach_censored

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

See this entry in the whole of v2.1.221 →

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