Magnitude

Magnitude is a TypeScript browser-agent framework that turns natural-language prompts into typed actions. The Steel integration runs Magnitude's planning loop on a Steel cloud browser, so you can drive a real session from prompts and end with structured outputs validated against a schema.

Good fit for research-style flows that mix navigation and extraction.

Requirements

• Steel API Key: Active Steel subscription
• Anthropic API Key: Magnitude's default planning model
• Node.js: v20+

Connect Steel to Magnitude

Pass Steel's CDP URL into Magnitude's startBrowserAgent config:

import { startBrowserAgent } from "magnitude-core";
import { Steel } from "steel-sdk";

const client = new Steel({ steelAPIKey: STEEL_API_KEY });
const session = await client.sessions.create({});

const agent = await startBrowserAgent({
  url: "https://github.com/steel-dev/leaderboard",
  llm: {
    provider: "anthropic",
    options: { model: "claude-sonnet-4-6", apiKey: ANTHROPIC_API_KEY },
  },
  browser: { cdp: `${session.websocketUrl}&apiKey=${STEEL_API_KEY}` },
});

Full runnable starter: Steel + Magnitude recipe →

Resources

• Magnitude documentation – Concepts, agent APIs, and examples
• Steel Sessions API reference – Programmatic session control for Steel browsers
• Steel Discord – Get help and share what you build