FA-74044 / Feature flag rollout bucketing / Member archive

Sticky variant persistence: Records from older experiment versions stay sticky · case 04

After an experiment restart users keep the arm from the previous version.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

stored is None or {variant, version}. A stored record is honoured (reason sticky, record unchanged) only if its version equals the current experiment version and its variant is still active; this takes precedence over traffic exclusion. Otherwise a None bucket_variant means excluded and the stored record is kept untouched; else the bucketed variant is assigned and a new record {variant, version} is returned. Return [variant, reason, record].

Why this case matters

Sticky bucketing keeps users on one arm across sessions; stale or retired records must not leak.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
record from a newer version is reassigned	`["b", "sticky", {"variant": "b", "version": 3}]`	`["a", "assigned", {"variant": "a", "version": 2}]`	Failed

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