Spent this weekend building a one-file OpenRouter client — figured I'd open-source it.

We deal with a lot of dynamic structured data, where different LLM calls have different priorities — speed, latency, cost. After a year using OpenRouter heavily in production, I hit a bunch of real-world problems — bad providers, unreliable fallbacks, weird edge cases with schemas — so I baked all of that into this. We needed strong guarantees on output and simple, reliable handling around it.

The primary motivations:

Explicit structure enforcement (Zod + JSON Schema)

Fine-tune per call — optimize for speed, latency, or price

Ignore bad providers (beyond account settings)

Fallback cleanly to JSON mode (180+ models)

Add new models declaratively, no client changes needed

It handles:

Strict structured outputs (zod-to-json-schema)

Fallback to JSON if needed

Provider sorting and fallback models

Unified one-line abstraction (makeLLMCall)

Real error handling and dynamic model swapping

We run over 50k OpenRouter requests/day through this in production. Tried to make it stupid simple to read and extend - coming up with the best API abstractions I could.

(On a personal note, as an overworked founder, it felt great to step away from growth and customer support for a bit and spend a day building clean APIs again — reminded me of the simpler days at CMU, grinding through Joshua Bloch’s API design classes. Honestly feels like this could make a good assignment problem.)