FA-41144 / Heap invariants / Member archive

Heap merge frontier refreshes each head from its post-pop cursor · case 04

The bounded run frontier certificate reports an incorrect heads.

Member previewVariant 4 · 3 implementations · 7 checks per implementation

Case contract

A k-way heap merge frontier stores one cursor per sorted run. A frontier item identifies run r and its current offset. Pop run r current item, advance only its offset, omit exhausted runs, and report next head candidates sorted by (value,run). Return emitted value, cursor vector, heads, exhausted runs, remaining item count, and next run.

Why this case matters

This isolates an internal heap representation or priority-structure invariant using deterministic finite records.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression certificate 2	`{"emitted": 1, "exhausted": [], "heads": [[1, 0], [2, 1]], "next_run": 1, "offsets": [1, 0], "remaining": 3}`	`{"emitted": 1, "exhausted": [], "heads": [[2, 1], [3, 0]], "next_run": 1, "offsets": [1, 0], "remaining": 3}`	Failed

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