dev-browser-nix

name	dev-browser-nix
description	Use dev-browser for browser automation on NixOS. Invoke when user asks to test UI, automate browser interactions, take screenshots, or verify web app behavior.

Dev-Browser on NixOS

This skill wraps the dev-browser plugin with NixOS-specific setup.

Prerequisites

The project flake.nix must include:

packages = with pkgs; [
  nodejs_22
  playwright-driver.browsers
];

shellHook = ''
  export PLAYWRIGHT_BROWSERS_PATH=${pkgs.playwright-driver.browsers}
  export PLAYWRIGHT_SKIP_BROWSER_DOWNLOAD=1
'';

Chromium Version Symlink

Playwright in dev-browser may expect a different chromium version than nixpkgs provides. Create a symlink:

mkdir -p ~/.cache/playwright-nix/chromium-1200
ln -sf /nix/store/*/playwright-browsers/chromium-*/chrome-linux ~/.cache/playwright-nix/chromium-1200/chrome-linux64

Then use PLAYWRIGHT_BROWSERS_PATH=~/.cache/playwright-nix when starting the server.

Starting the Server

eval "$(direnv export bash)" && \
cd ~/.claude/plugins/cache/dev-browser-marketplace/dev-browser/*/skills/dev-browser && \
PLAYWRIGHT_BROWSERS_PATH=~/.cache/playwright-nix HEADLESS=false \
npx tsx scripts/start-server.ts &

Wait for "Ready" message before running scripts.

Running Scripts

Always run from the dev-browser skills directory with direnv loaded:

eval "$(direnv export bash)" && \
cd ~/.claude/plugins/cache/dev-browser-marketplace/dev-browser/*/skills/dev-browser && \
npx tsx <<'EOF'
import { connect, waitForPageLoad } from "@/client.js";

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

// Your automation here
await page.goto("http://localhost:5173");
await waitForPageLoad(page);
await page.screenshot({ path: "tmp/screenshot.png" });

await client.disconnect();
EOF

Common Patterns

Handling Results Overlay

Sessions in etude end quickly and show a results overlay that blocks clicks:

// Dismiss overlay before interacting
await page.evaluate(() => {
  document.querySelectorAll('[class*="overlay"]').forEach(el => el.remove());
});

Capturing Console Logs

const logs = [];
page.on('console', msg => {
  if (msg.text().includes('DEBUG')) logs.push(msg.text());
});

Checking Element Colors (for note coloring verification)

const colors = await page.evaluate(() => {
  const notes = document.querySelectorAll('.note use');
  return Array.from(notes).map(use => ({
    id: use.closest('.note')?.id,
    fill: getComputedStyle(use).fill
  }));
});

Starting Fresh

When state is polluted, navigate from home:

await page.goto('http://localhost:5173/');
await waitForPageLoad(page);
await page.click('text=C Major Scale');
await page.waitForTimeout(2000);

Troubleshooting

"npx: command not found"

Ensure nodejs is in flake and direnv is loaded:

eval "$(direnv export bash)"
which npx  # Should show nix store path

"chromium-XXXX not found"

Create symlink from available version to expected version in ~/.cache/playwright-nix/

Overlay blocking clicks

The error <div class="_overlay_...">…</div> intercepts pointer events means a modal is open. Dismiss it with Escape or remove via evaluate.

HMR not updating code

Restart vite dev server:

pkill -f vite
cd packages/client && bun run dev &

Session ends too quickly

The playhead runs fast on short pieces. For testing note coloring, capture console logs to verify the coloring code runs, rather than relying on visual screenshots.