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API quickstart

Call the Radium API. Anthropic-compatible Messages endpoint, authentication, model names, production and staging base URLs, and OpenAI-compatible Chat Completions.

Quickstart

Radium serves an Anthropic-compatible Messages API. If your application already speaks that shape, or you use Anthropic-style tool calling, or you run Claude Code, this is the endpoint you want and the change is a base URL and a model name.

An OpenAI-compatible Chat Completions endpoint is available as well, and it is covered further down for applications that expect it.

Your first request

Set your key once:

export RADIUM_API_KEY="YOUR_RADIUM_API_KEY"

Then send this:

curl -s https://api.radium.cloud/v1/messages \
  -H "content-type: application/json" \
  -H "anthropic-version: 2023-06-01" \
  -H "x-api-key: $RADIUM_API_KEY" \
  -d '{
    "model": "hal-1.0",
    "max_tokens": 2048,
    "messages": [
      { "role": "user", "content": "Say only: radium hal connected." }
    ]
  }'

That is the whole integration. Everything below is detail.

Authentication

Every request needs a key. The default header is x-api-key:

x-api-key: $RADIUM_API_KEY

Some deployments use a bearer token instead:

Authorization: Bearer $RADIUM_API_KEY

Use the mode Radium supplied with your key. If nobody specified one, start with x-api-key and you will almost certainly be right.

Models

Model Built for
hal-1.0 Higher-capability coding and agentic work. Used in the examples on this page.
clarke-1.0 General-purpose and structured work
tycho-1.0 Faster, lighter-weight tasks

Swap the identifier in the request body, or in your Claude Code configuration, and nothing else changes.

The Messages API

Base URL:

https://api.radium.cloud

Full endpoint:

POST https://api.radium.cloud/v1/messages

The request body is the standard Anthropic Messages shape.

curl

curl -s https://api.radium.cloud/v1/messages \
  -H "content-type: application/json" \
  -H "anthropic-version: 2023-06-01" \
  -H "x-api-key: $RADIUM_API_KEY" \
  -d '{
    "model": "hal-1.0",
    "max_tokens": 2048,
    "messages": [
      { "role": "user", "content": "Hello, Radium!" }
    ]
  }'

Python

import anthropic

client = anthropic.Anthropic(
    api_key="YOUR_RADIUM_API_KEY",
    base_url="https://api.radium.cloud",
)

message = client.messages.create(
    model="hal-1.0",
    max_tokens=1024,
    messages=[
        {"role": "user", "content": "Hello, Radium!"}
    ],
)

print(message.content[0].text)

TypeScript

import Anthropic from "@anthropic-ai/sdk";

const client = new Anthropic({
  apiKey: "YOUR_RADIUM_API_KEY",
  baseURL: "https://api.radium.cloud",
});

const message: Anthropic.Message = await client.messages.create({
  model: "hal-1.0",
  max_tokens: 1024,
  messages: [{ role: "user", content: "Hello, Radium!" }],
});

console.log(message.content[0].text);

Tool calling works through the same endpoint, and it has its own page. See tool calling.

Production and staging

Messages API base URLs

Environment Base URL Endpoint
Production https://api.radium.cloud POST /v1/messages
Staging https://stage.api.radium.cloud POST /v1/messages

Credentials do not cross over Staging needs staging credentials. A production key will not authenticate against the staging endpoint, and that is deliberate.

Dedicated deployments

Organisations running on a dedicated Radium deployment use the host supplied to them, and every endpoint pattern on this page applies unchanged. If you need one, talk to us.

OpenAI-compatible Chat Completions

Use this only when your application expects an OpenAI-compatible Chat Completions API. Anthropic-compatible clients should use POST /v1/messages above.

The base URL for this path includes /v1:

https://api.radium.cloud/v1

curl -s https://api.radium.cloud/v1/chat/completions \
  -H "content-type: application/json" \
  -H "x-api-key: $RADIUM_API_KEY" \
  -d '{
    "model": "hal-1.0",
    "max_tokens": 2048,
    "temperature": 0,
    "messages": [
      { "role": "user", "content": "Hello, Radium!" }
    ]
  }'

Bearer authentication works here too, and the model identifiers are the same three.

Every endpoint

Endpoint summary

Use case Method Endpoint
Messages, production POST https://api.radium.cloud/v1/messages
Messages, staging POST https://stage.api.radium.cloud/v1/messages
Chat Completions, production POST https://api.radium.cloud/v1/chat/completions
Chat Completions, staging POST https://stage.api.radium.cloud/v1/chat/completions

Claude Code

Claude Code points at the Anthropic-compatible base URL and adds the request path itself, so configure it with the base URL alone:

export ANTHROPIC_BASE_URL="https://api.radium.cloud"
export ANTHROPIC_MODEL="hal-1.0"
export ANTHROPIC_API_KEY="$RADIUM_API_KEY"

Check it:

claude --print --model hal-1.0 "Say only: radium hal connected."

The one that catches everybody Do not put /v1/messages into ANTHROPIC_BASE_URL. Claude Code appends it, and a base URL with the path already on it returns a 404 on every request.

The full setup, including the scripted install, model selection, and troubleshooting, is on Run Claude Code on Radium.

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