Paper Detail
Jiacheng Xu, Feng Chen, Xiuneng Xu, Bo An
Existing methods for test-time reinforcement learning (TTRL) derive rewards from answer-level self-voting on unlabeled test-time tasks with canonical answers, but this breaks down for code generation because programs cannot be compared by surface form and therefore do not directly provide a usable training signal. To make TTRL applicable to code generation, we propose probe-driven TTRL, which constructs output-free probe inputs from the problem statement, executes candidate programs on these probes, and defines a Probe Consensus Reward (PCR) from the resulting behavioral agreement. PCR provides a behavioral training signal for open-vocabulary programs, but it is not a fully reliable verifier and remains susceptible to reward hacking through spurious consensus. We therefore introduce Entropy-Regularized Rank-Masked Policy Optimization (ERPO), which converts low PCR into conservative negative updates through rank masking and controls policy drift with an entropy ceiling. On coding benchmarks, ERPO substantially improves pass@1 and pass@k in both in-domain adaptation and zero-shot transfer.
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@article{xu2026entropy,
title = {Entropy-Regularized Rank-Masked Policy Optimization for Test-Time Reinforcement Learning in Code Generation},
author = {Jiacheng Xu and Feng Chen and Xiuneng Xu and Bo An},
year = {2026},
abstract = {Existing methods for test-time reinforcement learning (TTRL) derive rewards from answer-level self-voting on unlabeled test-time tasks with canonical answers, but this breaks down for code generation because programs cannot be compared by surface form and therefore do not directly provide a usable training signal. To make TTRL applicable to code generation, we propose probe-driven TTRL, which constructs output-free probe inputs from the problem statement, executes candidate programs on these pro},
url = {https://arxiv.org/abs/2609.09135},
keywords = {cs.LG, cs.CL},
eprint = {2609.09135},
archiveprefix = {arXiv},
}
{}