OpenAI-Compatible API Gateway for SaaS: Tenant Metering and Model Routing

TL;DR: A SaaS can put Claude, GPT and Gemini behind one OpenAI-compatible server-side integration, while keeping tenant authorization and spending controls in its own backend. Start with explicit task routes, a validator for each route, and a record for every model attempt. A shared endpoint simplifies credentials and protocol handling; it does not define which customer may spend money or what counts as a usable result. With cocodot, the OpenAI-compatible base URL is https://cocodot.co/api/ai/v1 and one key can call different listed models, billed by tokens. For an Anthropic-compatible integration, use https://cocodot.co/api/ai as the base URL. New users must complete identity verification before calling the API, and free trial credit covers only selected budget models. Before sending sustained traffic, test output validation, interrupted requests, key rotation and your fallback policy. The architecture below is a suggested implementation in your application. It gives a product engineer a concrete way to connect usage to tenants without placing a gateway credential in a browser or treating a shared balance as a customer budget.

const response = await fetch("https://cocodot.co/api/ai/v1/chat/completions", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.COCODOT_API_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    model: "mcs-7", // Claude Sonnet 5.5
    max_tokens: 1000,
    messages: [{ role: "user", content: "Draft a short product title." }]
  })
});
if (!response.ok) throw new Error(`HTTP ${response.status}`);
const result = await response.json();
// Validate result and record usage inside your application.