In the MasRouter pattern (ACL 2025), what are the three cascaded stages in order?
Answer: Mode determination → Role allocation → Model selection
MasRouter's three stages are: (1) Mode determination — is this a single-agent or multi-agent task? (2) Role allocation — which agent roles are needed? (3) Model selection — which specific model fits each role given current load and capability? Each stage prunes the decision space for the next, allowing progressive narrowing rather than a single monolithic routing decision.