EvoLM: Self-Evolving Language Models through Co-Evolved Discriminative Rubrics
- URL: http://arxiv.org/abs/2605.03871v1
- Date: Tue, 05 May 2026 15:31:00 GMT
- Title: EvoLM: Self-Evolving Language Models through Co-Evolved Discriminative Rubrics
- Abstract summary: Language models encode substantial evaluative knowledge from pretraining.<n>Current post-training methods rely on external supervision to produce reward signals.<n>We introduce EVOLM, a method that structures a model's evaluative capacity into explicit discriminative rubrics.
- Score: 86.49781345669436
- License: http://creativecommons.org/licenses/by/4.0/
- Abstract: Language models encode substantial evaluative knowledge from pretraining, yet current post-training methods rely on external supervision (human annotations, proprietary models, or scalar reward models) to produce reward signals. Each imposes a ceiling. Human judgment cannot supervise capabilities beyond its own, proprietary APIs create dependencies, and verifiable rewards cover only domains with ground-truth answers. Self-improvement from a model's own evaluative capacity is a reward source that scales with the model itself, yet remains largely untapped by current methods. We introduce EVOLM, a post-training method that structures this capacity into explicit discriminative rubrics and uses them as training signal. EVOLM trains two capabilities within a single language model in alternation: (1) a rubric generator producing instance-specific evaluation criteria optimized for discriminative utility, which maximizes a small frozen judge's ability to distinguish preferred from dispreferred responses; and (2) a policy trained using those rubric-conditioned scores as reward. All preference signals are constructed from the policy's own outputs via temporal contrast with earlier checkpoints, requiring no human annotation or external supervision. EVOLM trains a Qwen3-8B model to generate rubrics that outperform GPT-4.1 on RewardBench-2 by 25.7%. The co-trained policy achieves 69.3% average on the OLMo3-Adapt suite, outperforming policies trained with GPT-4.1 prompted rubrics by 3.9% and with the state-of-the-art 8B reward model SkyWork-RM by 16%. Overall, EVOLM demonstrates that structuring a model's evaluative capacity into co-evolving discriminative rubrics enables self-improvement without external supervision.
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