FA-59908 / Inventory cost layering / Member archive

Moving average perpetual costing: half-cent rounding · case 03

Averages that land exactly on half a cent are truncated, drifting unit cost down over many receipts.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Input {onhand, avg (cents, integer), events}. On receipt the average becomes round-half-up((onhand*avg + qty*cost)/(onhand+qty)) to whole cents; an issue is costed at qty*avg with the current average and never changes it; an issue exceeding on-hand returns "short". When on-hand reaches zero the average is kept as the last value (not reset). Return {cogs, onhand, avg}.

Why this case matters

Inventory valuation and cost-of-goods decisions depend on this rule.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
receipt reprices	`{"avg": 116, "cogs": [580], "onhand": 15}`	`{"avg": 117, "cogs": [585], "onhand": 15}`	Failed

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