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So you want to use OpenRouter?

Blog · Watch/Read · (gathered 2026-09-13)

  • Simon Willison highlights a critical issue with OpenRouter’s selling point of automatic fallbacks and cost-effective routing: it can lead to inconsistent model behavior.
  • This inconsistency arises because different backend providers use varied serving software, optimizations, and settings, meaning the same OpenRouter endpoint can deliver different results, including varying vision capabilities or reasoning effort processing.
  • To ensure consistent behavior, users can explicitly control which provider is used with the provider.only option, and the /endpoints method can list available providers for a given model ID.