Developers · Relay
The routing layer behind the tutor.
LemonSugar Ai is a study companion for students. Relay is the separate developer surface: the same model router, exposed as an API you can call from your own apps. If you're here to study, go to the student app.
Relay API
A drop-in /v1/chat/completions endpoint compatible with the OpenAI spec. Same routing and savings logic as the app, billed against your account credits.
Manage API keys →The router
How each request is scored and sent to the cheapest model that can answer it correctly, instead of defaulting to a frontier model.
How routing works →Model catalogue
The providers and models Relay can route to, with the strengths each one is picked for.
Browse models →Routing transparency
A live, anonymized audit of provider share and concentration across recent routing decisions. No prompts, no user data.
Read the audit →Terms that apply
Relay usage is governed by the Relay API section of our Terms of Service and, for business customers, a Data Processing Addendum. For Relay traffic you are the data controller for the prompts and outputs you send.