Open weights become much more consequential once the model can reliably operate tools.
And now Kimi K3 （Max） leads open-weight models in Agent Arena with a +9.75% net-improvement score.
Agent Arena tests if selecting K3 as the orchestrator improve outcomes when the model has to choose tools and sustain a real workflow
Kimi K3 ranks 3rd across all 42 models （open and close）， behind Claude Fable 5 （High） and GPT 5.6 Sol （xHigh）， while GLM 5.2 （Max） is the next open-weight model at +7.12%.
Arena randomly assigns sessions to models， allowing it to estimate each orchestrator's causal effect against an average model.
The combined score averages five signals： confirmed success， user reactions， correction handling， bash recovery， and nonexistent-tool calls.