Align rollouts assignments with split assignments#427
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dferber90 merged 9 commits intoJul 9, 2026
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AndyBitz
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Jul 9, 2026
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What & why
Splits and rollouts hashed users into buckets with opposite conventions, so the same user could get a different variant depending on whether a flag was expressed as a split or a rollout. Switching a flag between the two (or "locking in" a rollout as a split) reassigned users even though the effective distribution was unchanged.
Changes
boundaryFor) over the full2**32hash space — a rollout at promillepis now bit-for-bit identical to the equivalent split, so switching outcome type reassigns nobody.% 100_000/ float-scaling approaches: no modulo bias, and no off-by-one edge where the top-of-range hash fell through to the default.findWeightedIndex/getScaledWeightshelpers; split boundaries are precomputed once per outcome (integer, allocation-free per eval).Reassignment impact