Vision-language reward models fail paraphrase consistency tests in robotics
Vision-language models deployed as reward functions in robotic learning systems fail to maintain consistency across semantically equivalent instructions, a critical vulnerability for autonomous systems. Researchers introduce ROBORMBENCH, a benchmark of 2,390 real robot trajectories with 21,673 verified paraphrases, demonstrating that both proprietary and open-source VLMs exhibit severe paraphrase fragility. Identical robot behaviors flip between success and failure depending on instruction wording, exposing a fundamental gap between VLM robustness claims and real-world deployment requirements. This finding challenges the assumption that vision-language models are reliable reward arbiters for embodied AI.62










