SBERT2S1 turns biomedical retrieval encoders into calibrated one-pass typed decision models

Pritam Deka · hf · 2026-10-05

New work asks whether biomedical sentence encoders trained for retrieval make good starting points for typed decision models that answer schema-constrained questions in one forward pass. Releases include SBERT2S1 (bi-encoder, cross-head C and prior-fused residual PFR heads), the BIODECIDE benchmark, and MEDLINE-S1 with 243k training decisions. Key findings: retrieval training helps PFR in 10 of 15 comparisons but hurts the C head; C beats PFR under every objective; the open RLCD recipe trails cross-entropy by 2.5–3.0 points due to reward normalization inflating the noisy score-function term 3.6–15×, largely recoverable with an unbiased leave-one-out estimator; after temperature scaling, no objective is clearly better calibrated than cross-entropy. Code, labels and a model are released.

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