So you want to use OpenRouter?
Simon Willison highlights OpenRouter pitfalls: provider routing makes the same model endpoint behave inconsistently across backends.
Simon Willison discusses problems, raised by Mohamed Moustafa, with relying on OpenRouter's single API endpoint that automatically routes to the most cost-effective provider. Different backend providers run different serving software with different optimizations and settings, so requests to the same endpoint can behave in different ways. Some providers lack vision capability for vision models, and the reasoning effort option can be processed differently across providers.
- OpenRouter routes requests to cost-effective backend providers via a single API endpoint
- Different providers run different serving software with different optimizations and settings
- Some providers lack vision capability even for vision-capable models
- Reasoning effort option handling differs between providers
- Vendors
- OpenRouter
- Products
- OpenRouter
From the original article
So you want to use OpenRouter? One of OpenRouter's selling points is that it "handles fallbacks automatically and picks the most cost-effective option for each request", so you can call a single API endpoint for a model and get routed to the best available backend provider. Mohamed Moustafa points out a whole set of ways that this can cause you problems.
simonwillison.net
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