test(app): align pane journeys with measured workspace chrome

Give rail-specific split journeys enough column width, assert launched Diff content independently of header shape, and retain pane identity across compact transitions. Expect the compact selector in the half-screen Explorer workflow.

Co-authored-by: Elsa Granger <zeyugao@outlook.com>

packages/app/e2e/browser/composer-diff-stat.spec.ts

@@ -78,7 +78,8 @@ test("composer diff stat reveals Changes, then opens the diff in the configured
   const workspace = await seedChangedAgent("composer-diff-stat-side-");
 
   try {
-    await page.setViewportSize({ width: 1400, height: 900 });
+    // Keep both workspace rails visible alongside app navigation and Explorer.
+    await page.setViewportSize({ width: 1900, height: 900 });
     await openAgentRoute(page, {
       workspaceId: workspace.workspaceId,
       agentId: workspace.agentId,

packages/app/e2e/browser/empty-pane-keyboard.spec.ts

@@ -56,9 +56,9 @@ test.describe("New tab keyboard launcher", () => {
       await expectLauncherSelection(launcher, "Diff");
       await page.keyboard.press("Enter");
 
-      await expect(
-        page.getByTestId("workspace-tab-working_diff").filter({ visible: true }),
-      ).toBeVisible({ timeout: 30_000 });
+      await expect(page.getByTestId("working-diff-panel").filter({ visible: true })).toBeVisible({
+        timeout: 30_000,
+      });
     } finally {
       await workspace.cleanup();
     }

packages/app/e2e/browser/explorer-pane-placement.spec.ts

@@ -105,6 +105,9 @@ function collectConsoleErrors(page: Page): string[] {
   return errors;
 }
 
+// These drag and tab-menu journeys need full rails beside the docked Explorer.
+test.use({ viewport: { width: 1900, height: 900 } });
+
 test.describe("explorer pane tab placement", () => {
   test("agents open in the main pane and New-tab splits keep the app usable", async ({
     page,

packages/app/e2e/browser/file-editing.spec.ts

@@ -435,7 +435,8 @@ test.describe("CodeMirror workspace file editing", () => {
     });
 
     try {
-      await page.setViewportSize({ width: 1280, height: 900 });
+      // Keep both tab rails available alongside the docked Explorer.
+      await page.setViewportSize({ width: 1900, height: 900 });
       await openAgentRoute(page, session);
 
       await openWorkspaceFile(page, "target.ts");

packages/app/e2e/browser/sidebar-workspace.spec.ts

@@ -645,6 +645,9 @@ test.describe("Half-screen desktop layout", () => {
           .locator('[data-testid^="workspace-pane-"]')
           .getByTestId("workspace-tabs-row")
           .filter({ visible: true }),
+      ).toHaveCount(0);
+      await expect(
+        page.getByTestId("workspace-tab-switcher-trigger").filter({ visible: true }),
       ).toHaveCount(1);
 
       await explorerToggle.click();

packages/app/e2e/browser/subagent-origin-pane.spec.ts

@@ -38,8 +38,12 @@ async function openParentInRightPane(page: Page, parentId: string, workspaceId:
   await expect(left).toBeVisible();
   await expect(right).toBeVisible();
   await expect(right).not.toHaveAttribute("data-testid", "workspace-pane-main");
+  // A later split can replace the parent pane's rail with compact chrome.
+  // Keep the pane identity instead of finding it again through that rail.
+  const rightPaneId = await right.getAttribute("data-testid");
+  expect(rightPaneId).not.toBeNull();
   await left.locator('[data-testid^="workspace-tab-draft_"]').click();
-  return { left, right };
+  return { left, right: page.getByTestId(rightPaneId!) };
 }
 
 test.beforeEach(async ({ page }) => {

packages/app/e2e/browser/terminal-find.spec.ts

@@ -413,6 +413,8 @@ test("searches retained output without sending Find input to the shell", async (
 test("keeps terminal Find owned by retained tabs and the focused split pane", async ({
   page,
 }, testInfo) => {
+  // This journey selects tabs from the full rails in both split panes.
+  await page.setViewportSize({ width: 1600, height: 900 });
   const first = await harness.createTerminal({
     name: "First search",
     command: "bash",

packages/app/e2e/browser/viewed-agent-timelines.spec.ts

@@ -357,6 +357,8 @@ test.describe("Viewed agent timelines", () => {
   });
 
   test("two visible split chats both stay current", async ({ page }) => {
+    // Keep both split panes wide enough for the tab-rail interactions below.
+    await page.setViewportSize({ width: 1600, height: 900 });
     const scenario = await seedViewedTimelineScenario();
     try {
       await enableMoveTabShortcut(page);

packages/app/e2e/browser/workspace-pane-remount.spec.ts

@@ -52,6 +52,8 @@ async function waitForWorkspaceRoute(page: Page, route: string) {
 test.describe("Workspace pane mounting", () => {
   test("workspace navigation keeps the existing agent composer mounted", async ({ page }) => {
     test.setTimeout(90_000);
+    // Keep both split panes wide enough for the tab-rail interactions below.
+    await page.setViewportSize({ width: 1600, height: 900 });
     const serverId = getServerId();
 
     const workspace = await seedWorkspace({ repoPrefix: "pane-remount-" });