Base URL eval mode

Evaluation path

Base URL mode points an official provider SDK at Varsten. It is useful for low-risk evaluations, traffic checks, and demo workloads. Your Varsten vk_ key replaces the provider key in the client; the real provider key stays vaulted with Varsten.

import OpenAI from "openai";

const client = new OpenAI({
  apiKey: process.env.VARSTEN_API_KEY,
  baseURL: "https://api.varsten.ai/v1",
});

import os
from openai import OpenAI

client = OpenAI(
    api_key=os.environ["VARSTEN_API_KEY"],
    base_url="https://api.varsten.ai/v1",
)

Base URL per provider

Each official SDK appends its own version segment, so the base URL differs per provider:

| Provider SDK | Base URL | | --- | --- | | OpenAI | https://api.varsten.ai/v1 | | Anthropic | https://api.varsten.ai (no /v1 — the SDK appends /v1/messages) | | Gemini (google-genai) | https://api.varsten.ai with api_version: "v1beta" |

The in-app setup at app.varsten.ai generates the exact client construction for your provider and language.

Important boundary

Base URL mode does not provide direct-to-provider fallback if Varsten is unavailable. Use the production SDK path for workloads that need local provider fallback.

Good fits

• A staging route with representative prompts.
• A low-risk internal tool.
• A temporary evaluation that checks attribution and pricing coverage.