Opper

Opper is an EU-hosted AI gateway: 700+ models from 50+ providers behind one OpenAI-compatible API and one API key. Token rates are the model providers' rates with no markup.

Setup

go get github.com/zendev-sh/goai@latest

import "github.com/zendev-sh/goai/provider/opper"

Set the OPPER_API_KEY environment variable, or pass WithAPIKey() directly. Create a key at platform.opper.ai.

Models

Model IDs are pool names. A pool is every provider serving that model, and Opper picks the route per request:

• claude-sonnet-4-6
• gpt-5.5
• gpt-5.4-mini
• gemini-3.8-flash
• deepseek-v4-pro

A provider/model ID such as anthropic/claude-sonnet-4-6 pins one route. See opper.ai/models for the full catalog.

Tested Models

Unit tested (mock HTTP server): claude-sonnet-4-6, anthropic/claude-sonnet-4-6

Usage

model := opper.Chat("claude-sonnet-4-6")

result, err := goai.GenerateText(ctx, model, goai.WithPrompt("Hello"))
if err != nil {
    log.Fatal(err)
}
fmt.Println(result.Text)

Options

Option	Type	Description
WithAPIKey(key)	string	Set a static API key
WithTokenSource(ts)	provider.TokenSource	Set a dynamic token source
WithBaseURL(url)	string	Override the default https://api.opper.ai/v3/compat endpoint
WithHeaders(h)	map[string]string	Set additional HTTP headers
WithHTTPClient(c)	*http.Client	Set a custom *http.Client

Notes

• Declares text-only chat capability. Image parts are sent in the standard image_url format for models that accept them.
• The package provides Chat only. Opper also serves /embeddings, which provider/compat can reach with the same base URL.
• Environment variable OPPER_BASE_URL can override the default endpoint.