FA-60635 / Loyalty points ledgers / Member archive

Idempotent points event ledger: single reversal guard · case 05

The same earn can be reversed repeatedly, draining the balance.

Member previewVariant 5 · 3 implementations · 7 checks per implementation

Case contract

Input {events:[{id,ts,type:"earn"|"redeem"|"reverse",pts,ref}]}. Duplicate ids are dropped keeping the first delivery in input order; survivors are applied sorted by (ts,id). Redeem requires balance >= pts or is rejected. Reverse undoes an applied earn or redeem once; unknown, rejected, already reversed, or reverse targets are rejected. Return {balance, rejected, applied}.

Why this case matters

Member point balances, statements and the program liability depend on this ledger rule.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
double reverse	`{"applied": ["e1", "r1", "r2"], "balance": -65, "rejected": ["r3"]}`	`{"applied": ["e1", "r1"], "balance": 0, "rejected": ["r2", "r3"]}`	Failed

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