What needed a frontier model last year runs on a more efficient one today, yet AI costs keep climbing. A higher token bill doesn't mean more work is getting done. Engineers default to the most powerful model out of fear of losing performance, so routine work runs the same premium path as the work that genuinely needs the expensive model. Factory Router cuts token spend by 20-25% while maintaining frontier performance. It automatically selects the right model for each task, and routes across providers for reliability. Designed for agents, it switches models only when the gain is worth rebuilding the prompt cache. We mapped the cost/performance Pareto frontier across benchmarks. Near the top it's nearly flat: cost drops sharply while performance barely moves. Then it bends hard: the most aggressive routing we measured cut Terminal-Bench 2 to 56% of Opus cost but dropped pass rate to 81%. Factory Router operates on the flat stretch, right before the bend. As efficient models improve, more work crosses into what they handle just as well. With automatic routing, users will see growing savings at frontier performance.