Meta proposes reward transformation exploiting GRPO rollouts to equalize subgroups

nagpalchirag · x · 2026-10-20

Method details from Meta's "Aligning Language Models towards Counterfactual Invariance" thread: the team proposes a reward transformation technique that exploits the multi-rollout structure of GRPO to quantify reward discrepancy between counterfactual subgroups, plus a custom leave-one-out reward designed to match reward expectations across subgroups in L2 distance.

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