Chain of Code

LMulator: The LM generates pseudocode programs and explicitly annotates sub-tasks that can't be executed; a "LMulator" simulates those sub-tasks with the LM while the interpreter handles the rest.

Undefined-behavior handling: The interpreter catches undefined behavior and cleanly hands off to the LM, sidestepping the brittleness of code-first approaches that fail silently on hard ops.

84% on BIG-Bench Hard: Achieves 84% on BIG-Bench Hard - a 12-point gain over Chain of Thought and a clean demonstration that mixing exact execution with LM simulation beats either alone.

Broad applicability: Works across math, logic, and commonsense reasoning, positioning Chain of Code as a general-purpose CoT upgrade.