Summary & Key Takeaways ​

• OpenRouter's automatic fallback can lead to inconsistent model behavior across providers.
• Different providers may use varying serving software, optimizations, or settings.
• Some providers might lack specific capabilities, like vision for vision models.
• The provider.only option allows explicit control over which provider is used.
• The /endpoints method can list available providers for a given model ID.

Our Commentary ​

This is a vital heads-up for anyone diving into multi-provider LLM APIs. The promise of "automatic fallbacks" sounds great on paper, but the reality of inconsistent behavior across providers is a real headache. I've seen this kind of issue pop up in other abstracted services too. Simon's advice on using provider.only is a lifesaver. It's a good reminder that abstractions always leak.