ModeBench comprises questions with multiple valid solutions across five domains: graph coloring, normalized computation trees, executable Python code, algebraic problems, and constraint optimization. Each task includes an executable verifier that determines both correctness and unique solution-mode identity.
Scoring uses pairwise correct-mode diversity (PCMD) to measure diversity conditional on correctness, alongside standard accuracy metrics. Experiments show RLVR post-training reduces solution diversity even as accuracy improves, while the proposed Re:Max method mitigates this collapse.