test(e2e): keep developer toasts out of concurrent app assertions

Concurrent layout measurements could invoke the same Playwright locator handler before its first dismissal finished, leaving checks waiting for a removed button. Hide only the Expo toast host through test styling while retaining console error capture.

packages/app/e2e/browser/sidebar-nav-settings.spec.ts

@@ -1,4 +1,5 @@
 import { expect, test } from "../support/fixtures";
+import type { Page } from "@playwright/test";
 import { openAddProjectFlow, addProjectFlow } from "../support/helpers/add-project-flow";
 import { installUsageReportsFixture } from "../support/helpers/usage-reports";
 import {
@@ -31,6 +32,28 @@ import {
   setSidebarNavItemVisible,
 } from "../support/helpers/sidebar-nav-settings";
 
+async function showDeveloperToast(page: Page): Promise<void> {
+  await page.evaluate(() => {
+    document.getElementById("error-toast")?.remove();
+    const toast = document.createElement("div");
+    toast.id = "error-toast";
+    toast.style.cssText = "position:fixed;inset:0;z-index:2147483647;background:white";
+    // Expo renders its unnamed dismiss button in an open shadow root.
+    const button = document.createElement("button");
+    button.style.cssText = "width:24px;height:24px";
+    button.addEventListener("click", () => toast.remove());
+    toast.attachShadow({ mode: "open" }).appendChild(button);
+    document.body.appendChild(toast);
+  });
+}
+
+test("developer toasts leave concurrent sidebar layout checks uninterrupted", async ({ page }) => {
+  await gotoAppShell(page);
+  await showDeveloperToast(page);
+  await expectSidebarOrder(page, ["new-workspace", "history", "search", "schedules"]);
+  await expect(page.locator("#error-toast")).toBeHidden();
+});
+
 test("fixed footer line keeps its five icons, Help and Settings at the end", async ({ page }) => {
   test.setTimeout(120_000);
   await installUsageReportsFixture(page, { lists: [() => claudeAndCodexReports()] });

packages/app/e2e/support/developer-ui.mjs

@@ -1,10 +1,21 @@
 /** @param {import('@playwright/test').Page} page */
-export async function installDeveloperToastDismissal(page) {
-  // Developer chrome must not cover app actions or move the test's pointer/focus.
+export async function hideDeveloperToasts(page) {
+  // Keep developer chrome out of app interactions without Playwright locator
+  // handlers: parallel app assertions can race while dismissing the same toast.
   // Console errors remain in the runner's logs.
-  const dismiss = page.locator("#error-toast").getByRole("button", { name: "", exact: true });
-  await page.addLocatorHandler(dismiss, () => dismiss.dispatchEvent("click"), {
-    // A new logged error can replace the toast before the old one disappears.
-    noWaitAfter: true,
-  });
+  function hideToasts() {
+    const installStyle = () => {
+      const style = document.createElement("style");
+      style.textContent = "#error-toast { display: none !important; }";
+      document.head.appendChild(style);
+    };
+    if (document.readyState === "loading") {
+      document.addEventListener("DOMContentLoaded", installStyle, { once: true });
+    } else {
+      installStyle();
+    }
+  }
+  await page.addInitScript(hideToasts);
+  // Electron connects to an already loaded page; apply there as well.
+  await page.evaluate(hideToasts);
 }

packages/app/e2e/support/fixtures.ts

@@ -1,5 +1,5 @@
 import { test as base, expect, type Page } from "@playwright/test";
-import { installDeveloperToastDismissal } from "./developer-ui.mjs";
+import { hideDeveloperToasts } from "./developer-ui.mjs";
 import { startOutdatedDaemon, type OutdatedDaemon } from "./helpers/daemon-update";
 import { startE2EWorker } from "./helpers/e2e-worker";
 import { getE2EDaemonPort } from "./helpers/daemon-port";
@@ -131,7 +131,7 @@ const test = daemonTest.extend<{
         await ws.close({ code: 1008, reason: "Blocked connection to localhost:6767 during e2e." });
       });
 
-      await installDeveloperToastDismissal(page);
+      await hideDeveloperToasts(page);
 
       const entries: string[] = [];
 

packages/desktop/e2e/browser-tabs.e2e.mjs

@@ -12,7 +12,7 @@ import { fileURLToPath } from "node:url";
 import { experimental_createMCPClient } from "ai";
 import { StreamableHTTPClientTransport } from "@modelcontextprotocol/sdk/client/streamableHttp.js";
 import { chromium } from "playwright";
-import { installDeveloperToastDismissal } from "../../app/e2e/support/developer-ui.mjs";
+import { hideDeveloperToasts } from "../../app/e2e/support/developer-ui.mjs";
 import { runAppearanceFontSizeRegression } from "./appearance-font-size.electron.mjs";
 import { runSettingsMemoryRegression } from "./settings-memory.electron.mjs";
 
@@ -1189,7 +1189,7 @@ async function main() {
 
     browser = await chromium.connectOverCDP(`http://127.0.0.1:${cdpPort}`);
     const page = await waitForAppPage(browser, expoPort);
-    await installDeveloperToastDismissal(page);
+    await hideDeveloperToasts(page);
     const status = await waitForDesktopStatus(page);
 
     const checkPluginLinks = () =>