Title: CONCUR: A Framework for Continual Constrained and Unconstrained Routing
Primary area: foundation or frontier models, including LLMs
Keywords: model routing, continual routing, constrained routing, unconstrained routing

Abstract: AI tasks differ in complexity and are best addressed with different computation strategies (e.g., combinations of models and decoding methods). Hence, an effective routing system that maps tasks to the appropriate strategies is crucial.
Most prior methods build the routing framework by training a *single* model across *all* strategies, which demands full retraining whenever new strategies appear and leads to high overhead. Attempts at such continual routing, however, often face difficulties with generalization.
Prior models also typically use a *single* input representation, limiting their ability to capture the full complexity of the routing problem and leading to sub-optimal routing decisions.
To address these gaps, we propose CONCUR, a **con**tinual routing framework that supports both **c**onstrained and **u**nconstrained **r**outing (i.e., routing with or without a budget).
Our *modular* design trains a separate predictor model for each strategy, enabling seamless incorporation of new strategies with low additional training cost.
Our predictors also leverage *multiple* representations of both tasks and computation strategies to better capture overall problem complexity.
Experiments on both in-distribution and out-of-distribution, knowledge- and reasoning-intensive tasks show that our method outperforms the best single strategy and strong existing routing techniques with higher end-to-end accuracy and lower inference cost in both continual and non-continual settings, while also reducing training cost in the continual setting.