OpenRouter launches Fusion API, matching Claude Fable 5 at half the cost

OpenRouter, a global AI API aggregation platform, has announced the launch of Fusion API, a composite AI model service. It sends user inputs to multiple models, analyzes their responses, and produces a unified answer. The goal is to achieve high performance at a lower cost.

In official tests, Fusion's multi-model setups scored well. For instance, combining Claude Opus 4.8 and GPT-5.5 scored 67.6%, beating Claude Fable 5's 65.3%. Adding Gemini 3.1 Pro pushed the score to 68.3%.

On cost, Fusion stands out. The combo of Gemini 3 Flash, Kimi K2.6, and DeepSeek V4 Pro delivers performance within 1% of Claude Fable 5, but at roughly half the cost. This gives developers a cost-effective AI model option.