Meta-Ctrl: Guaranteed Plan Generation by Decoupling Syntactic and Semantic Constraints
A constrained-decoding framework that guarantees LLM-generated robot plans satisfy syntactic and semantic constraints while preserving the base LM's plan quality. Meta-Ctrl introduces meta-tokens—a compact vocabulary of grounded actions—enforcing syntax at the token level and semantics (preconditions, goals, ordering) at the action level, an exact factorization that cuts constrained-decoding memory from over 107 TB to under 2 GB. Lifts small open-weight LMs above frontier models like GPT-4o and o1-preview on embodied planning benchmarks, and is demonstrated on a real tabletop robot. Project page