OpenRouter has launched an API built around a simple bet: that a panel of cheap AI models, combined the right way, can match a single expensive one. And by “expensive,” they mean Claude Fable 5.
Introducing the Fusion API, the smartest compound model in the market.
Fusion achieves Fable-level intelligence at half the price.
How to get a cheap FableWhen you send a prompt to Fusion, OpenRouter fires it off to a panel of models in parallel. Each one gets web search and bash tools.
Then, a judge model extracts consensus points, contradictions, and blind spots from every response. After this phase is over, a synthesizer—Claude Opus 4.8 by default—writes the final answer grounded in that analysis.
The whole thing happens server-side. You can swap your model string to "openrouter/fusion" for a default panel, add a fusion tool so your own model calls it selectively, or build a custom panel in the Fusion chatroom with no code.
The cheaper combination is the one OpenRouter wants remembered: The cheap Gemini 3 Flash combined with the open-source Chinese models Kimi K2.6 and DeepSeek V4 Pro, fused and synthesized by Opus, hit 64.7%—beating solo GPT-5.5 (60%) and solo Opus 4.8 (58.8%) outright and landing within a point of Fable at roughly half the cost.
Even pairing Opus 4.8 with a separate instance itself scored 65.5%, a 6.7-point jump over solo Opus; OpenRouter says roughly three quarters of that lift comes from the synthesis step itself, the rest from genuine model diversity.
One wrinkle: giving the panel live web access lets models surface DRACO's own grading rubric in search results, a contamination risk that OpenRouter calls coincidental rather than deliberate. The fix took one config line to exclude the benchmark's hosting domains from the search tools, and every published number reflects that cleaned-up run.
Worth a try?The regular model still handles the day-to-day stuff. Fusion is there for the questions where one model might miss something important, and having a few perspectives cross-check each other actually moves the needle.
For deep research, complex planning, or anything where contradictions matter, the room seems to help.
The charts make the basic point clear enough: On this kind of work, the expensive solo model is no longer the only way to get strong synthesis. A group of models that are still easy to get, fused together, can sit right next to it on the results while delivering a much smaller bill.
