OpenRouter Fusion is basically ask N models + synthesizer step.

This is ask a special orchestrator they built, which is in front of a bunch of models, which model would suit the request best.

Regular Fugu seems to be just "pick the best model and route the request there"

Fugu Ultra can generate like a little mini workflow/plan instead to achieve a result

1. Ask GPT to derive the math. 2. Ask Opus to check for implementation/security issues. 3. Ask Gemini to synthesize or resolve disagreement. 4. Return final answer.

I could be wrong but seems to be that at a glance, so I think it's more dynamic than OpenRouter Fusion.