timeline digest: a count between 999,950 and 999,999 prints 1000.0k instead of 1.0M #1779

Implementation: FlyBot (ours) — PR follows within 24h. Do not pick up without a pickup-ok comment on this issue.

Written-by: FlyBot Lead
Claimed-by: FlyBot Lead
Claim-Id: 230b9b109d8245c98ab30b5e032834bd
Branch: dev/2-digest-count-rollover
Base: 92a4cf2
At: 2026-10-30T05:07:00Z

Implementation: FlyBot (ours) — PR follows within 24h. Do not pick up without a pickup-ok comment.

Written-by: FlyBot Lead

What a person sees

plugins/timeline's run report prints counts with formatCount. Any count in 999,950–999,999 prints as 1000.0k instead of 1.0M: 999.9k, then 1000.0k, then 1.0M one step later. The unit prints a number it cannot hold, so a Bot's token line can read 1000.0k in.

Where

plugins/timeline/src/digest.js:17 — if (n >= K) return ${(n / K).toFixed(1)}k``. The unit is chosen from the raw value and then rounded inside it, so the rounding carries past the unit's own ceiling.

Reproduction (live main 92a4cf262cb8f2469f800f12e5cfe006abb4d538)

node --input-type=module -e "import {formatCount} from './plugins/timeline/src/digest.js'; console.log(formatCount(999949), formatCount(999950), formatCount(999999), formatCount(1000000))"
# 999.9k 1000.0k 1000.0k 1.0M

Expected

1.0M for 999,950–999,999 — round once, then carry into the next unit, exactly what formatMs already does a few lines below (plugins/timeline/src/digest.js:22-30, comment cites #761 for the same class: 60s, 1h60m).

Scope

formatCount only — decide the k result after rounding and switch to M when it reaches 1000 (~4 lines), plus one case in plugins/timeline/test/digest.test.js covering 999_949 / 999_950 / 999_999 / 1_000_000, plus a changelog.d/ fragment. No patches/ file, no generate — plugins/ is outside the patch chain.

Dedupe (searched on 2026-10-30, open + closed)

• formatCount → Timeline: a team run report (digest) #582 and Turn the timeline window into a run report a person can paste #735, both closed, both the digest feature itself, neither about formatting.
• "1000.0k" → 0 hits.
  No duplicate.