dev-browser

name	dev-browser
description	Browser automation with persistent page state using dev-browser CLI. Use when user mentions 'browse', 'open website', 'click on', 'fill form', 'take screenshot', 'scrape', 'automate browser', 'test website', 'log into', 'navigate to', 'web page', 'dev-browser', or any browser interaction task.
allowed-tools	["Bash(dev-browser *)","Bash(/Applications/Helium.app/Contents/MacOS/Helium *)"]

dev-browser

Browser automation tool that controls browsers through sandboxed JavaScript scripts via CLI. Scripts run in QuickJS WASM sandbox - not Node.js. No require, fetch, fs, or process.

Setup

If dev-browser is not found:

npm install -g dev-browser
dev-browser install

Core Pattern

Write small, focused scripts. Each script does ONE thing. End by logging state for next decision.

dev-browser <<'EOF'
const page = await browser.getPage("main");
await page.goto("https://example.com");
console.log(JSON.stringify({ url: page.url(), title: await page.title() }, null, 2));
EOF

CLI Flags

Flag	Description
--headless	Launch Chromium in headless mode
--connect [URL]	Connect to running Chrome/Chromium via CDP (auto-discover Chrome, or use a specific CDP endpoint)
--browser <NAME>	Select named browser instance (default: "default")
--timeout <SECONDS>	Max script execution time (default: 30)

Browser API

Method	Description
browser.getPage(name)	Get/create named page (persists between scripts)
browser.newPage()	Create anonymous page (auto-cleanup after script)
browser.listPages()	List all tabs: [{id, url, title, name}]
browser.closePage(name)	Close named page

File I/O (restricted to ~/.dev-browser/tmp/)

Method	Description
await saveScreenshot(buf, name)	Save screenshot buffer, returns path
await writeFile(name, data)	Write file, returns path
await readFile(name)	Read file, returns content

Key Workflows

Discover Unknown Page

dev-browser <<'EOF'
const page = await browser.getPage("main");
await page.goto("https://example.com");
const result = await page.snapshotForAI();
console.log(result.full);
EOF

Then interact based on discovered elements:

dev-browser <<'EOF'
const page = await browser.getPage("main");
await page.getByRole("button", { name: "Continue" }).click();
const result = await page.snapshotForAI({ track: "main" });
console.log(result.full);
EOF

Take Screenshot

dev-browser <<'EOF'
const page = await browser.getPage("main");
const buf = await page.screenshot();
const path = await saveScreenshot(buf, "debug.png");
console.log(path);
EOF

Fill Form

dev-browser <<'EOF'
const page = await browser.getPage("main");
await page.fill("#email", "[e-mail]");
await page.fill("#password", "secret");
await page.click("button[type=submit]");
await page.waitForURL("**/dashboard");
console.log(JSON.stringify({ url: page.url(), title: await page.title() }, null, 2));
EOF

Connect to Running Chrome

dev-browser --connect <<'EOF'
const tabs = await browser.listPages();
console.log(JSON.stringify(tabs, null, 2));
EOF

Connect to Helium via CDP

Helium is Chromium-based and can be controlled by dev-browser when launched with remote debugging enabled. dev-browser --connect auto-discovery does not find Helium, so always pass the explicit CDP endpoint.

For a separate automation profile:

"/Applications/Helium.app/Contents/MacOS/Helium" \
  --remote-debugging-port=9334 \
  --user-data-dir=/tmp/helium-dev-browser-profile \
  --no-first-run \
  --no-default-browser-check

Then connect:

dev-browser --browser helium --connect http://127.0.0.1:9334 <<'EOF'
const tabs = await browser.listPages();
console.log(JSON.stringify(tabs, null, 2));
EOF

To automate the user's existing Helium session, Helium must be fully quit and relaunched with --remote-debugging-port; an already-running Helium instance that was started without remote debugging cannot be attached by dev-browser.

"/Applications/Helium.app/Contents/MacOS/Helium" --remote-debugging-port=9334
dev-browser --browser helium --connect http://127.0.0.1:9334

If Helium is already open without CDP and must not be restarted, use AppleScript or Computer Use for UI-level control instead of dev-browser.

Error Recovery

If a script fails, the page stays where it stopped. Reconnect and inspect:

dev-browser <<'EOF'
const page = await browser.getPage("main");
const path = await saveScreenshot(await page.screenshot(), "debug.png");
console.log(JSON.stringify({ screenshot: path, url: page.url(), title: await page.title() }, null, 2));
EOF

Tips

• Use page.snapshotForAI() for structure discovery; use screenshots for visual layout
• Keep page names stable across scripts to resume after failures
• Use console.log(JSON.stringify(...)) for structured output
• Use --timeout 10 for scripts that should fail fast
• Pages from browser.getPage("name") persist between script runs - no need to re-navigate
• Inside page.evaluate(...), use plain JavaScript only - no TypeScript

Full API Reference

For complete Playwright Page methods and advanced patterns, see references/api-reference.md.