[Birfy]

Fixes #1665

Written-by: Dev-1
Owner: Dev
Reviewer: Reviewer
Tip: f6e8180
Tree: 289dc6f41e504a5f658e7ca5593b87210a7761f0

What changed

Before: a busy Bot answered a new message with a template that quoted a truncated piece of it inside a fixed phrase (「「那些 needs-human 的i...」记下了，马上接着处理。」, #1630).
After: the host publishes the ack at once with an empty text (the client draws avatar + blinking dots, #1657) and asks one short model call — config.flybot.modelFor['busy-ack'] when set, else the chat's own model, reasoning off, 80 output tokens — for one natural sentence in the message's language about what the message asks and what the turn is doing, with no quoting and no stock phrases. Hard 3 s timeout; a timeout, error, empty/overlong answer or missing route leaves the text empty, so nothing is sent and the dots clear with the turn. A late answer never revives a cleared ack. The template generator, topicOf truncation and tool-word tables are removed. Tests mock the model; docs/subsystems/core-host.md and a changelog fragment updated.

Verification at the tip

Tip SHA: f6e8180
Ran: TZ=UTC npm run verify (exit 0; core 1949 pass / 0 fail), node scripts/ds-bot-patches.mjs generate + check, node .github/scripts/changelog.mjs check.
Not run (and why): live/LIVE deployment (out of scope, not touched); no real-model latency measurement.

Checkpoint

{
  "pr": 1667,
  "claim": "Dev",
  "issue": 1665,
  "summary": "The busy-ack is written by one short model call instead of templates. It is published pending at once (dots), filled by the model in the user's language, bounded by a 3 s hard timeout. On timeout or error no text is sent and the pending ack clears with the turn. Template and truncation code removed.",
  "files": ["core/src/host/busy-ack.js", "core/test/busy-ack.test.js", "docs/subsystems/core-host.md", "changelog.d/1665-busy-ack-model.changed.md", "patches/ds-bot/files/src/host/busy-ack.js", "patches/ds-bot/files/test/busy-ack.test.js"],
  "checks": { "ran": "npm run verify", "result": "green", "at": "f6e8180a269b23e6d4b6bce4ab053716a6981a39" },
  "next": "none — ready for review"
}

[Birfy]

Verdict: PASS at f6e8180
Written-by: Reviewer
Attestation: f6e8180 role=Reviewer

Reviewed the diff at this tip: template/truncation generator removed; ack published pending (empty text → client dots) and filled by one model call with ACK_SYSTEM (user's language, actual content + current work, no quoting, no stock phrases); route = modelFor['busy-ack'] or the chat's own, reasoning off, maxTokens 80; hard 3 s bound via AbortSignal.timeout plus a race timer; errors/timeouts/empty/overlong → no text; late answer cannot revive a cleared ack. Room path keeps the relay header out of the prompt.

Ran at this tip:

$ TZ=UTC npm run verify
# exit 0 — core: tests 1949 pass 0 fail; plugins/social, tree, timeline, workflow, .github scripts, interop, live-e2e lint/tests all 0 fail
$ cd core && node --import ./test/harness-resolve.mjs --test test/busy-ack.test.js test/busy-ack-client.test.js
# tests 20 pass 20 fail 0