What Should Remain After Forgetting? Rethinking LLM Unlearning as Predictive Posterior Correction

LLM unlearning is often implemented by assigning surrogate targets, such as refusal, uniformity, or likelihood suppression, to forget-related prompts. We argue that this surrogate assignment view is misaligned with the counterfactual goal of unlearning: recovering the retain-only predictive posterior. This mismatch is especially problematic in mixed-evidence regimes, where a response may be associated with forgotten evidence while still being partially supported by retained evidence. We propose EASE: Evidence Attribution and Subtraction Estimator, a logit-space posterior-correction method that estimates the forget-induced component of the deployed model's predictive support and subtracts it at inference time. EASE uses lightweight deletion and compensation assistants to remove forget-neighbour evidence while restoring nearby retain-supported evidence. We formalize the suppression-scope dilemma and provide guarantees showing when posterior correction recovers the retain-only posterior. Experiments on TOFU and MUSE show that EASE improves forgetting–retention trade-offs over strong baselines, achieving the best aggregate score in 5/6 main TOFU settings, reducing mixed-query semantic leakage by 22.2%, and matching or exceeding full-retain baselines with 9 times fewer retain examples. Our code is available at: https://anonymous.4open.science/r/EASE-9675.