chore: add global setup to warm up dev server and limit playwright concurrency to prevent flaky tests

Author: la-niina

www/e2e/global-setup.ts

@@ -0,0 +1,29 @@
+import { chromium } from '@playwright/test'
+
+const baseURL = 'http://127.0.0.1:3000'
+
+/**
+ * Warm up the dev server before the tests run. A cold `vite dev` boot
+ * recompiles the whole app (SSR + client) on first request, and the first
+ * browser to load the client modules also triggers dependency re-optimization,
+ * which can take well over a minute and stall the first test. Loading both
+ * surfaces here (real browser, real module requests) absorbs that cost once,
+ * up front, instead of inside a test.
+ */
+export default async function globalSetup() {
+	const browser = await chromium.launch()
+	const page = await browser.newPage()
+
+	await page.goto(`${baseURL}/`, { waitUntil: 'domcontentloaded' })
+	await page
+		.getByRole('heading', { level: 1 })
+		.first()
+		.waitFor({ state: 'visible', timeout: 120_000 })
+
+	await page.goto(`${baseURL}/admin`, { waitUntil: 'domcontentloaded' })
+	await page
+		.getByRole('heading', { name: 'Sign in' })
+		.waitFor({ state: 'visible', timeout: 120_000 })
+
+	await browser.close()
+}

www/playwright.config.ts

@@ -2,7 +2,13 @@ import { defineConfig } from '@playwright/test'
 
 export default defineConfig({
 	testDir: './e2e',
-	fullyParallel: true,
+	// Serial, single worker: the first page load after a cold `vite dev` boot
+	// recompiles the whole app (SSR + client) and the Cloudflare module
+	// runner is fragile under concurrent cold loads, so hitting it with
+	// parallel workers makes the first run flaky.
+	workers: 1,
+	retries: 1,
+	globalSetup: './e2e/global-setup',
 	reporter: 'list',
 	use: {
 		baseURL: 'http://127.0.0.1:3000',