Go

Standard library

package main

import (
    "bytes"
    "encoding/json"
    "fmt"
    "io"
    "net/http"
    "os"
    "time"
)

type chatReq struct {
    Model    string `json:"model"`
    Messages []msg  `json:"messages"`
}
type msg struct {
    Role    string `json:"role"`
    Content string `json:"content"`
}

func main() {
    body, _ := json.Marshal(chatReq{
        Model: "auto",
        Messages: []msg{{Role: "user", Content: "hi"}},
    })

    req, _ := http.NewRequest("POST",
        "https://api.routeur.ai/v1/chat/completions",
        bytes.NewReader(body))
    req.Header.Set("Authorization", "Bearer "+os.Getenv("ROUTEUR_KEY"))
    req.Header.Set("Content-Type", "application/json")

    client := &http.Client{Timeout: 30 * time.Second}
    res, err := client.Do(req)
    if err != nil { panic(err) }
    defer res.Body.Close()

    out, _ := io.ReadAll(res.Body)
    fmt.Println(string(out))
}

Official OpenAI Go client

The official openai-go package lets you set a base URL:

import (
    "context"
    "os"

    "github.com/openai/openai-go"
    "github.com/openai/openai-go/option"
)

client := openai.NewClient(
    option.WithAPIKey(os.Getenv("ROUTEUR_KEY")),
    option.WithBaseURL("https://api.routeur.ai/v1/"),
)

res, err := client.Chat.Completions.New(context.TODO(),
    openai.ChatCompletionNewParams{
        Model: openai.F("auto"),
        Messages: openai.F([]openai.ChatCompletionMessageParamUnion{
            openai.UserMessage("hi"),
        }),
    })

Choosing a model

Every request picks an upstream model in one of three ways — in this order of precedence:

1. Routeur-* request headers. If Routeur-Provider or Routeur-Model are set, they win, regardless of what is in the body. Useful from middleware or transports that can't change the JSON.
2. An explicit upstream id in the model field. Pass something like "gpt-4o-mini" or "claude-3-5-sonnet" to bypass routing rules and pin the request to that model.
3. "auto" (or any alias). Lets routeur.ai pick the upstream model from your routing rules. This is the recommended default.

Force a specific provider+model on a single call via headers:

req.Header.Set("Routeur-Provider", "openai")
req.Header.Set("Routeur-Model",    "gpt-4o")