Arena's Max router launches with Fable 5 and Kimi K3 at lower cost than single models

AIArena says its Max routing method, paired with Fable 5 and Kimi K3, achieves a +10.7% net improvement at a median cost of $1.06 per task. That outperforms Fable 5 (High) by 0.6 percentage points while cutting cost 54%. Arena says the same approach can work across other model combinations.

AIArena says its Max system moves the performance-cost Pareto frontier in Agent Arena's Code, Chat, and Work categories. By routing between Fable 5.1 and GPT 6 Astra, Max delivers stronger results at lower cost than any single frontier model.

AIArena says Max routes 67% of code sessions to Astra (Medium), while chat favors Astra (Max) at 49% and Fable 5.1 (Max) at 42%. Work sessions split mostly between Fable 5.1 (Max) at 49% and Astra (Medium) at 43%. Max also learns which costly coding sessions Astra (Medium) can likely solve, routing those to it to save money.

AIArena introduces Max, an agentic version of its model router that selects the best model for each task. Trained on 2.5M real-world sessions from Agent Arena, Max achieves a +14.7% net improvement score at a median cost of $3.27 per task. Arena says this matches Claude Fable 5.1 (Max) performance at 37% lower cost, and offers Max free for a limited time.