Steel

Move a Steel automation to Kernel

Steel and Kernel both hand you a hosted Chromium over CDP, so the connection swap is one line. The differences worth planning for are what happens around the session.

Concept mapping

Concept	Steel	Kernel
Create a session	client.sessions.create()	kernel.browsers.create()
CDP endpoint	Session websocketUrl	browser.cdp_ws_url
Release a session	client.sessions.release(id)	kernel.browsers.deleteByID(session_id), or let timeout_seconds expire
Live session viewer	Session viewer URL	browser.browser_live_view_url, returned on create
Persisted state	Session context / credentials	Profiles, populated and maintained by managed auth
Stealth	Stealth session flag	Anti-detection by default; stealth: true adds the managed proxy and CAPTCHA solver
CAPTCHA solving	Session solver option	Included with stealth mode
Proxies	Session proxy, billed per GB	Proxies, unmetered on Kernel-provided types
Files	Session files API	File I/O
Extensions	Session extensions	Extensions
Warm sessions	—	Browser pools
Run code beside the browser	—	Playwright execution, App Platform
Self-hosting	Open-source Steel server	Not applicable — see migrating from self-hosted if that’s what you run today

The connection change

import Kernel from '@onkernel/sdk';
import { chromium } from 'playwright-core';

const kernel = new Kernel();
const kernelBrowser = await kernel.browsers.create({ stealth: true, timeout_seconds: 600 });

const browser = await chromium.connectOverCDP(kernelBrowser.cdp_ws_url);
const page = browser.contexts()[0].pages()[0];
await page.goto('https://example.com');
await browser.close();

await kernel.browsers.deleteByID(kernelBrowser.session_id);

What to change next

• Stop connecting over CDP for the hot path. Playwright execution runs your code inside the browser’s VM and returns values, with no connection to manage and no CDP fingerprint on the wire. See how you drive the browser.
• Replace credential handling with managed auth. Kernel performs the login, keeps the session warm with health checks, and writes the result into a profile your browsers attach.
• Use a pool for repeated work. Pool acquisition skips both browser creation and the per-plan create rate.

If you were self-hosting Steel to control cost or data residency, read zero data retention and security practices before you plan the move.