Agent Skills: Dev Browser Skill

Dev Browser Skill

Browser automation that maintains page state across script executions. Write small, focused scripts to accomplish tasks incrementally.

Choosing Your Approach

• Local/source-available sites: Read the source code first to write selectors directly
• Unknown page layouts: Use getAISnapshot() to discover elements and selectSnapshotRef() to interact with them
• Visual feedback: Take screenshots to see what the user sees

Setup

IMPORTANT: Always use Standalone Mode for browser automation.

Standalone Mode (Default)

Launches a Chromium browser with a persistent profile. Login sessions, cookies, and local storage persist across browser restarts.

Start the server:

~/.config/opencode/skill/dev-browser/server.sh &

Wait for the Ready message before running scripts. Add --headless flag if user requests headless mode.

Key points:

• Profile stored at ~/.config/opencode/skill/dev-browser/profiles/browser-data
• Once logged in, future sessions remain authenticated
• Use this mode for local dev testing with auth (localhost:3000, etc.)

Writing Scripts

Run all scripts from the dev-browser directory.

Execute scripts inline using heredocs:

cd ~/.config/opencode/skill/dev-browser && npx tsx <<'EOF'
import { connect, waitForPageLoad } from "@/client.js";

const client = await connect();
const page = await client.page("example");
await page.setViewportSize({ width: 1280, height: 800 });

await page.goto("https://example.com");
await waitForPageLoad(page);

console.log({ title: await page.title(), url: page.url() });
await client.disconnect();
EOF

Key Principles

1. Small scripts: Each script does ONE thing (navigate, click, fill, check)
2. Evaluate state: Log/return state at the end to decide next steps
3. Descriptive page names: Use "checkout", "login", not "main"
4. Disconnect to exit: await client.disconnect() - pages persist on server
5. Plain JS in evaluate: page.evaluate() runs in browser - no TypeScript syntax

Workflow Loop

1. Write a script to perform one action
2. Run it and observe the output
3. Evaluate - did it work? What's the current state?
4. Decide - is the task complete or do we need another script?
5. Repeat until task is done

Client API

const client = await connect();
const page = await client.page("name"); // Get or create named page
const pages = await client.list(); // List all page names
await client.close("name"); // Close a page
await client.disconnect(); // Disconnect (pages persist)

// ARIA Snapshot methods
const snapshot = await client.getAISnapshot("name"); // Get accessibility tree
const element = await client.selectSnapshotRef("name", "e5"); // Get element by ref

// Token-efficient content extraction
const outline = await client.getOutline("name"); // Tree of all elements
const interactive = await client.getInteractiveOutline("name"); // Only interactive elements
const text = await client.getVisibleText("name"); // Visible text only

Token-Efficient Content Extraction

| Method | Use case | Token efficiency | |--------|----------|------------------| | getInteractiveOutline() | Discover clickable elements | Most efficient | | getOutline() | Understand page structure | Very efficient | | getVisibleText() | Extract readable content | Very efficient | | getAISnapshot() | Need ref-based clicking | Full ARIA tree | | screenshot() | Visual debugging | Uses vision tokens |

Screenshots

await page.screenshot({ path: "tmp/screenshot.png" });
await page.screenshot({ path: "tmp/full.png", fullPage: true });

ARIA Snapshot (Element Discovery)

Use getAISnapshot() to discover page elements. Returns YAML-formatted accessibility tree with [ref=eN] references for interaction:

const snapshot = await client.getAISnapshot("hackernews");
console.log(snapshot); // Find the ref you need

const element = await client.selectSnapshotRef("hackernews", "e2");
await element.click();

Error Recovery

Page state persists after failures. Debug with:

cd ~/.config/opencode/skill/dev-browser && npx tsx <<'EOF'
import { connect } from "@/client.js";

const client = await connect();
const page = await client.page("hackernews");

await page.screenshot({ path: "tmp/debug.png" });
console.log({
  url: page.url(),
  title: await page.title(),
  bodyText: await page.textContent("body").then((t) => t?.slice(0, 200)),
});

await client.disconnect();
EOF