@inproceedings{peng-etal-2026-beyond-sampled,
title = "Beyond the Sampled Token: Preserving Candidate Support in {RLVR}",
author = "Peng, Ruotian and
Ren, Yi and
Yu, Zhouliang and
Liu, Weiyang and
Wen, Yandong",
editor = "Lee, Hung-Yi and
Dev, Sunipa and
Li, Jessy and
Elliott, Desmond",
booktitle = "Findings of the {A}ssociation for {C}omputational {L}inguistics: {EMNLP} 2026",
month = oct,
year = "2026",
address = "Budapest, Hungary",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.findings-emnlp.635/",
pages = "13318--13340",
ISBN = "979-8-89176-462-0",
abstract = "We revisit exploration collapse in reinforcement learning with verifiable rewards (RLVR), from the perspective of the candidate distribution for next-token prediction. We formally show that as probability concentrates on the top-1 candidate, the expected number of distinct responses collapses to one regardless of the sampling budget $K$. This theoretical implication is further verified by our empirical tracking of top-$N$ candidate probabilities during training, where the top-1 candidate progressively dominates while plausible alternatives are suppressed. These findings suggest a key desideratum for effective exploration: preserving non-negligible probability mass on the top-$N$ candidates. To this end, we propose Candidate-aware Support Preservation (CaSP), with two complementary designs. Specifically, CaSP redistributes positive gradients among top-$N$ candidates for correct responses, and applies a stronger penalty to the top-1 candidate for incorrect responses. Unlike many exploration-oriented methods that improve pass@$K$ at the cost of pass@1, CaSP improves pass@$K$ across the full $K$ spectrum. These gains generalize to 6 math, 2 logical-reasoning, and 2 coding benchmarks, and scales to 32B-parameter models and sampling budgets up to $K=1024$, positioning it as a principled, candidate-level approach for RLVR exploration."
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<abstract>We revisit exploration collapse in reinforcement learning with verifiable rewards (RLVR), from the perspective of the candidate distribution for next-token prediction. We formally show that as probability concentrates on the top-1 candidate, the expected number of distinct responses collapses to one regardless of the sampling budget K. This theoretical implication is further verified by our empirical tracking of top-N candidate probabilities during training, where the top-1 candidate progressively dominates while plausible alternatives are suppressed. These findings suggest a key desideratum for effective exploration: preserving non-negligible probability mass on the top-N candidates. To this end, we propose Candidate-aware Support Preservation (CaSP), with two complementary designs. Specifically, CaSP redistributes positive gradients among top-N candidates for correct responses, and applies a stronger penalty to the top-1 candidate for incorrect responses. Unlike many exploration-oriented methods that improve pass@K at the cost of pass@1, CaSP improves pass@K across the full K spectrum. These gains generalize to 6 math, 2 logical-reasoning, and 2 coding benchmarks, and scales to 32B-parameter models and sampling budgets up to K=1024, positioning it as a principled, candidate-level approach for RLVR exploration.</abstract>
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%0 Conference Proceedings
%T Beyond the Sampled Token: Preserving Candidate Support in RLVR
%A Peng, Ruotian
%A Ren, Yi
%A Yu, Zhouliang
%A Liu, Weiyang
%A Wen, Yandong
%Y Lee, Hung-Yi
%Y Dev, Sunipa
%Y Li, Jessy
%Y Elliott, Desmond
%S Findings of the Association for Computational Linguistics: EMNLP 2026
%D 2026
%8 October
%I Association for Computational Linguistics
%C Budapest, Hungary
%@ 979-8-89176-462-0
%F peng-etal-2026-beyond-sampled
%X We revisit exploration collapse in reinforcement learning with verifiable rewards (RLVR), from the perspective of the candidate distribution for next-token prediction. We formally show that as probability concentrates on the top-1 candidate, the expected number of distinct responses collapses to one regardless of the sampling budget K. This theoretical implication is further verified by our empirical tracking of top-N candidate probabilities during training, where the top-1 candidate progressively dominates while plausible alternatives are suppressed. These findings suggest a key desideratum for effective exploration: preserving non-negligible probability mass on the top-N candidates. To this end, we propose Candidate-aware Support Preservation (CaSP), with two complementary designs. Specifically, CaSP redistributes positive gradients among top-N candidates for correct responses, and applies a stronger penalty to the top-1 candidate for incorrect responses. Unlike many exploration-oriented methods that improve pass@K at the cost of pass@1, CaSP improves pass@K across the full K spectrum. These gains generalize to 6 math, 2 logical-reasoning, and 2 coding benchmarks, and scales to 32B-parameter models and sampling budgets up to K=1024, positioning it as a principled, candidate-level approach for RLVR exploration.
%U https://aclanthology.org/2026.findings-emnlp.635/
%P 13318-13340
Markdown (Informal)
[Beyond the Sampled Token: Preserving Candidate Support in RLVR](https://aclanthology.org/2026.findings-emnlp.635/) (Peng et al., Findings 2026)
ACL