Best AI model for complex reasoning
Ranked on LMArena's hard prompts board: the subset of real user prompts judged most demanding, with several constraints, specialist knowledge or long chains of logic.
Ratings from LMArena, snapshot 2026-10-19, used under its licence with attribution. Prices are what Rapid Router bills per request.
Compare the leaders
How this is ranked
The rating is an Elo-style score from LMArena's hard, multi-step problems board. A 40-point gap means the higher model wins roughly 56% of head-to-head votes, so models within a few points of each other are, for practical purposes, tied.
Only models that are live and paid on Rapid Router are listed; free-tier and preview models are on the catalog. For your own monthly cost on any of them, use the cost calculator.
Common questions
What is the best ai model for complex reasoning?
Gemini 4 Argon by Google ranks first on LMArena's hard, multi-step problems board as of October 2026.
Which model gives the best value for hard, multi-step problems?
MiMo-V2.6-Pro rates within 40 points of the top model on the same board and costs ₹42.25 per million input tokens, against ₹197 for Gemini 4 Argon.
How do I use these models?
Every model here is callable at https://rapidrouter.ai/api/v1 with one Rapid Router key and the OpenAI SDK; switching between them is a one-string change. Each model's page has a ready request.
How often does this ranking change?
It is read from the latest LMArena snapshot (2026-10-19) and the live catalog every time the page loads, so new models and new votes show up without anyone editing the page.