Gives real routing-traffic numbers on cost and quality tradeoffs between open and closed models, supporting a start-open, escalate-to-closed approach for AI agentAn AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.Full definition → steps.
Key takeaways · AI-distilled
Both kinds of model grew: closed-weight volume in OpenRouter's top 50 rose from 3.4T to 33T tokenThe chunk of text a model reads and writes in — roughly three-quarters of a word — and the unit AI usage is billed in.Full definition → a week between October 2025 and September 2026, while open weightsA model whose trained parameters are published for anyone to download and run — unlike API-only models you can access but never possess.Full definition → volume rose more than 60-fold to 83.5T. The open share peaked at 77.5% in July.
OpenRouter attributes the roughly 4x price gap mainly to competition: DeepSeek V4.1 Flash had 31 providers and GLM-5.3 Flash 30, versus 2 to 5 for the closed models it sampled. Input prices for one open model spanned $0.03 to $0.60 per million tokens.
The categories overlap at the model level. Kimi K3's endpoints ranged from cheaper than Claude Sonnet 5.5 to about twice its price, while GPT-6 Luna listed at $0.10 per million input tokens, below any Kimi K3 provider.
The shares exclude stealth models, which reached 38.7T tokens in the latest week, and token counts come from each provider's own tokenizer. OpenRouter's June roundup put the quality gap at about five points on an earlier index version.
Terms in this piece · Glossary
open weights — A model whose trained parameters are published for anyone to download and run — unlike API-only models you can access but never possess.
token — The chunk of text a model reads and writes in — roughly three-quarters of a word — and the unit AI usage is billed in.
AI agent — An AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.
