FA-100692 / Speculative decoding bookkeeping / Member archive

Decoding: Layered cache commit preserves only positions before rejection · case 02

Layered cache commit preserves only positions before rejection.

Member previewVariant 2 · 3 implementations · 7 checks per implementation

Case contract

Cache records are [layer, absolute_position, payload] in arbitrary order. Given proposal start position p and accepted count k, retain every layer record at positions before p+k, preserving history and accepted positions; discard the rejected position and all later speculative positions.

Why this case matters

A self-contained bookkeeping model makes prefix and token-count semantics observable without a model runtime.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
both layers through verified prefix	`[[0, 12, "a"], [1, 12, "A"]]`	`[[0, 12, "a"], [1, 12, "A"], [0, 13, "b"], [1, 13, "B"]]`	Failed

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