Mastra and Pydantic AI both made per-request model routing a core primitive on September 25.

Mastra core 1.70.0 added ModelSelectionProcessor, which uses a built-in classifier to pick the best or cheapest model per run, with a first-step scope and a minProbability control. Pydantic AI 2.50.0 reworked its DecisionModel so routes carry one label each and added an opt-in decision_route_threshold. (Mastra release) Pydantic also fixed Anthropic one-hour cache writes being priced at the five-minute rate, which is a real refund if you use long caches. Mastra 1.71.0 followed minutes later with eager tool execution: a tool call starts as soon as its own arguments finish streaming instead of waiting for the whole step, disableable per run. Hand-rolled router layers are now framework features in two ecosystems.