Fix the frontend dev server 404ing every route after the SSR migration

apps/dashboard/playwright.config.ts

@@ -7,7 +7,9 @@ export default defineConfig({
   forbidOnly: !!process.env.CI,
   fullyParallel: true,
   projects: [{ name: "chromium", use: { ...devices["Desktop Chrome"] } }],
-  reporter: process.env.CI ? [["list"], ["github"]] : [["list"]],
+  // "html" writes playwright-report/, which the e2e workflow uploads as an artifact on
+  // failure — without it a red nightly run leaves nothing to debug from.
+  reporter: process.env.CI ? [["list"], ["github"], ["html", { open: "never" }]] : [["list"]],
   retries: process.env.CI ? 2 : 0,
   testDir: "./e2e",
   timeout: 60_000,

apps/frontend/package.json

@@ -111,6 +111,7 @@
     "eslint-plugin-storybook": "^9.1.4",
     "husky": ">=6",
     "jsdom": "26",
+    "lightningcss": "^1.32.0",
     "lint-staged": ">=10",
     "msw": "^2.14.6",
     "prettier": "catalog:",

apps/frontend/playwright.config.ts

@@ -7,7 +7,9 @@ export default defineConfig({
   forbidOnly: !!process.env.CI,
   fullyParallel: true,
   projects: [{ name: "chromium", use: { ...devices["Desktop Chrome"] } }],
-  reporter: process.env.CI ? [["list"], ["github"]] : [["list"]],
+  // "html" writes playwright-report/, which the e2e workflow uploads as an artifact on
+  // failure — without it a red nightly run leaves nothing to debug from.
+  reporter: process.env.CI ? [["list"], ["github"], ["html", { open: "never" }]] : [["list"]],
   retries: process.env.CI ? 2 : 0,
   testDir: "./e2e",
   timeout: 60_000,

apps/frontend/src/tests/vite-single-instance.test.ts

@@ -0,0 +1,29 @@
+import { realpathSync } from "node:fs";
+import { createRequire } from "node:module";
+import { describe, expect, it } from "vitest";
+
+// TanStack Start decides whether to install its SSR dev middleware with
+// `isRunnableDevEnvironment(env)`, which is an `instanceof` check. If the plugin resolves a
+// different copy of Vite than the one that created the dev server, that check silently fails,
+// the middleware is never installed and every dev route falls through to a 404 — the app is
+// unreachable locally and the Playwright webServer never becomes ready.
+//
+// Bun installs a separate copy of Vite per resolved optional-peer set, so this breaks as soon
+// as the app and the plugin disagree on one of them (`lightningcss` is why the frontend depends
+// on it directly). Compare the resolved module paths rather than trusting the version alone.
+const require = createRequire(import.meta.url);
+
+function resolveViteFrom(requirer: NodeRequire): string {
+  return realpathSync(requirer.resolve("vite"));
+}
+
+describe("Vite module identity", () => {
+  it("resolves the same Vite copy for the app and for the TanStack Start plugin", () => {
+    const appVite = resolveViteFrom(require);
+
+    const reactStart = createRequire(require.resolve("@tanstack/react-start/package.json"));
+    const startPlugin = createRequire(reactStart.resolve("@tanstack/start-plugin-core/package.json"));
+
+    expect(resolveViteFrom(startPlugin)).toBe(appVite);
+  });
+});