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Guarded progressive ramp: History lags one stage behind · case 04

Audit history shows the percentage before each advance, hiding when the ramp reached full traffic.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

stages is an increasing list of percentages; the ramp starts at stages[0]. Each check [error_rate, sample] is processed in order: after a rollback everything stays at 0; a sample below 100 holds the current stage; an error rate above 0.02 rolls back to 0 permanently; otherwise advance one stage (staying at the last). State is complete at the last stage, rolled_back after a rollback, else ramping. Return [final percent, state, percent after each check].

Why this case matters

Automated ramps with guardrails must neither overreact to noise nor resume after a rollback.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
history records the stage after advancing	`[25, "ramping", [1, 5]]`	`[25, "ramping", [5, 25]]`	Failed

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