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A cache evicts the entry it most recently served · case 04

Insertion order is mistaken for recency, or updating an existing value fails to refresh that recency.

Member previewVariant 4 · 3 implementations · 7 checks per implementation

Case contract

Events are ['put',key,value] or ['get',key]; keys are strings and capacity is nonnegative. A get returns value or None, and only hits refresh recency. Every put refreshes its key. Capacity zero retains nothing. Return [read results,keys ordered least to most recent].

Why this case matters

Models cache bookkeeping independently of expiration or concurrent locking, covering the difference between recency after a read and recency after replacing an existing value.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
hit moves oldest before eviction	`[[4], ["k1", "k2", "k3", "k4", "new"]]`	`[[4], ["k2", "k3", "k4", "k0", "new"]]`	Failed

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