diff --git a/ui/.gitignore b/ui/.gitignore
index 612bbcc..4917c73 100644
--- a/ui/.gitignore
+++ b/ui/.gitignore
@@ -1,5 +1,6 @@
 node_modules/
 dist/
+dist-e2e/
 .svelte-kit/
 *.tsbuildinfo
 test-results/
diff --git a/ui/playwright.config.ts b/ui/playwright.config.ts
index cc28f70..78e5d74 100644
--- a/ui/playwright.config.ts
+++ b/ui/playwright.config.ts
@@ -1,7 +1,11 @@
 import { defineConfig, devices } from '@playwright/test';
 
-// Hermetic e2e: Playwright boots the Vite dev server in `mock` mode (the in-memory
-// fake transport), so the smoke needs no backend/gateway/Postgres.
+// Hermetic e2e: Playwright builds the app in `mock` mode (the in-memory fake transport, so the
+// smoke needs no backend/gateway/Postgres) and serves the MINIFIED artifact via `vite preview`,
+// rather than the dev server. Running against the production-minified bundle is what the contour
+// ships, so the e2e now catches minification-only regressions — e.g. a reactive dependency the
+// minifier drops — which the unminified dev server silently hid. The build goes to dist-e2e/ so it
+// never clobbers the dist/ the bundle-size gate measures.
 export default defineConfig({
   testDir: './e2e',
   fullyParallel: true,
@@ -13,10 +17,15 @@ export default defineConfig({
     trace: 'on-first-retry',
   },
   webServer: {
-    command: 'pnpm exec vite --mode mock --port 4173 --strictPort',
+    // `--base /` overrides the production relative base (`./`, which lets the gateway serve the SPA
+    // under /app/ and /telegram/): served from the preview root, an absolute base keeps assets at
+    // /assets/ so the SPA-fallback also boots a subpath like /telegram/. Base only prefixes asset
+    // URLs, so the minified JS under test is identical to the contour's.
+    command:
+      'pnpm exec vite build --mode mock --base / --outDir dist-e2e --emptyOutDir && pnpm exec vite preview --outDir dist-e2e --port 4173 --strictPort',
     url: 'http://localhost:4173',
     reuseExistingServer: !process.env.CI,
-    timeout: 60_000,
+    timeout: 120_000,
   },
   // Run the same hermetic specs in Chromium and WebKit (Safari's engine) so the UI is
   // exercised in both rendering/JS engines. Note: desktop WebKit on Linux does not