Speculative Macro Commit pre-executes multi-action chains and cuts AppWorld wall time 44.9%.

Tool-using agents lose wall-clock to serial action-observation turns, not just inference. SMC runs a large authoritative actor producing the official trajectory while a faster drafter continuously predicts and executes future action chains on an isolated environment snapshot, matching against a macro library of recurring skeletons mined from training traces. When the actor's next call matches the first drafted action, SMC commits the remaining pre-executed steps and their observations. Qwen3.5-27B INT4 actor with Qwen3.5-4B drafter matches sequential accuracy at 18.59% lower latency on Tau^2-Bench Telecom and 44.9% lower wall time on AppWorld with a small completion drop. Code is public. arXiv 2609.03236