diff --git a/playwright.config.ts b/playwright.config.ts
index b5c1d24..96b9a2f 100644
--- a/playwright.config.ts
+++ b/playwright.config.ts
@@ -5,6 +5,7 @@ const port = Number(process.env.PW_PORT ?? 5179);
 
 export default defineConfig({
   testDir: "tests/e2e",
+  globalSetup: "./tests/e2e/warm-up.ts",
   retries: process.env.CI ? 2 : 0,
   reporter: process.env.CI ? [["dot"], ["html", { open: "never" }]] : "list",
   use: {
@@ -16,5 +17,6 @@ export default defineConfig({
     command: `npm run dev -- --port ${port} --strictPort`,
     url: `http://localhost:${port}`,
     reuseExistingServer: !process.env.CI,
+    env: { PW_E2E: "1" },
   },
 });
diff --git a/tests/e2e/warm-up.ts b/tests/e2e/warm-up.ts
new file mode 100644
index 0000000..c87cb9f
--- /dev/null
+++ b/tests/e2e/warm-up.ts
@@ -0,0 +1,23 @@
+import { chromium, type FullConfig } from "@playwright/test";
+
+// A route's first request makes the dev server transform its whole module
+// graph; under load that outlasts a spec's 5 s expect, so it is paid here once.
+const ROUTES = [
+  ["/", "Dashboard"],
+  ["/servo", "Pick a servo in the left pane."],
+  ["/table", "Control table"],
+  ["/live", "Live"],
+] as const;
+
+export default async function warmUp(config: FullConfig): Promise<void> {
+  const browser = await chromium.launch();
+  try {
+    const page = await browser.newPage({ baseURL: config.projects[0]?.use.baseURL });
+    for (const [path, text] of ROUTES) {
+      await page.goto(`${path}?sim=1`);
+      await page.getByRole("main").getByText(text, { exact: true }).waitFor({ timeout: 60_000 });
+    }
+  } finally {
+    await browser.close();
+  }
+}
diff --git a/vite.config.ts b/vite.config.ts
index 0d028ce..1be308c 100644
--- a/vite.config.ts
+++ b/vite.config.ts
@@ -37,6 +37,8 @@ export default defineConfig({
   server: {
     // The file: dependency lives outside this repo, so dev must be allowed to serve its wasm.
     fs: { allow: [".", "../open-servo-core/client/web"] },
+    // A rebuild of the shared wasm package mid-run hot-swaps the session out from under a spec.
+    watch: process.env.PW_E2E === "1" ? null : undefined,
   },
   plugins: [
     localDescriptors(),