diff --git a/.gitignore b/.gitignore
index 6329e49..e64f658 100644
--- a/.gitignore
+++ b/.gitignore
@@ -152,3 +152,8 @@ site/SPECIFICATION.md
 site/DESIGN.md
 site/ARCHITECTURE.md .claude/settings.json
 tmp
+
+# Playwright
+test-results/
+playwright-report/
+playwright/.cache/
diff --git a/site/e2e/homepage.spec.ts b/site/e2e/homepage.spec.ts
index 1a85af2..00d94dd 100644
--- a/site/e2e/homepage.spec.ts
+++ b/site/e2e/homepage.spec.ts
@@ -114,6 +114,42 @@ test.describe("Homepage", () => {
       expect(newState).toBe(!initialState);
     });
 
+    test("preset toggle updates preview without console errors", async ({
+      page,
+    }) => {
+      const errors: string[] = [];
+      page.on("console", (msg) => {
+        if (msg.type() === "error") {
+          errors.push(msg.text());
+        }
+      });
+
+      const previewBefore = await page
+        .locator("[class*='font-mono']")
+        .first()
+        .innerHTML();
+
+      const checkbox = page
+        .locator("input[type='checkbox']")
+        .filter({ hasText: /log levels/i })
+        .or(page.locator("input[type='checkbox']").first());
+      await checkbox.first().click();
+
+      await page.waitForTimeout(500);
+
+      const previewAfter = await page
+        .locator("[class*='font-mono']")
+        .first()
+        .innerHTML();
+
+      const criticalErrors = errors.filter(
+        (e) =>
+          !e.includes("Download the React DevTools") &&
+          !e.includes("hydration"),
+      );
+      expect(criticalErrors).toHaveLength(0);
+    });
+
     test("live preview shows log output", async ({ page }) => {
       const preview = page.locator("[class*='font-mono']").first();
       await expect(preview).toBeVisible();
diff --git a/site/test-results/.last-run.json b/site/test-results/.last-run.json
index f740f7c..cbcc1fb 100644
--- a/site/test-results/.last-run.json
+++ b/site/test-results/.last-run.json
@@ -1,4 +1,4 @@
 {
   "status": "passed",
   "failedTests": []
-}
+}
\ No newline at end of file