Executes what Part 1 only measured: Phase 0, the re-key migration, a live Square
import, and a full recompute through sales-summaries-v2, with every window
re-cut to end 08-13 so the backup's partial final day stops skewing the numbers.
Reportable error falls from 542 days off / $30,982.11 to 71 days off / $405.79,
a 98.7% reduction, with 5 material days left — three of them the ones the plan
predicted. 107,815 entities were re-keyed with refund and charge counts
unchanged, which is what proves the expand step resolves legacy keys instead of
duplicating under the new scheme. NGCD 2026-07-23, off by exactly $71.94 with no
refund line, now carries the line and balances to 9.1e-13.
Records two defects that only executing could surface:
Re-keying a charge with two parent orders duplicates the tender. The migration
scoped such charges through whichever order it saw first, so the other client's
import found neither the scoped nor the legacy key and created a second charge,
which cardinality-many then added beside the first. Contended clients' error was
$441,045 until 15,961 stale refs were retracted. §4.3 warned about this and the
migration under-weighted it; it must split shared charges before shipping.
dirty-sales-summaries index-pulls from the client's start point with no :end and
filters lazily, so it scans every later client's summaries too — O(n²), and the
recompute degraded from ~180 to ~3 client-days per minute as summaries piled up.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Bryce
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