diff --git a/tests/e2e/viewport-quad-layout.e2e.ts b/tests/e2e/viewport-quad-layout.e2e.ts
new file mode 100644
index 00000000..04fa2c57
--- /dev/null
+++ b/tests/e2e/viewport-quad-layout.e2e.ts
@@ -0,0 +1,59 @@
+import { expect, test } from "@playwright/test";
+
+import { clickViewport } from "./viewport-test-helpers";
+
+test("quad viewport layout shows four linked panels with shared selection and active panel state", async ({ page }) => {
+  const pageErrors: string[] = [];
+  const consoleErrors: string[] = [];
+
+  page.on("pageerror", (error) => {
+    pageErrors.push(error.message);
+  });
+
+  page.on("console", (message) => {
+    if (message.type() === "error") {
+      consoleErrors.push(message.text());
+    }
+  });
+
+  await page.goto("/");
+  await page.evaluate((storageKey) => {
+    window.localStorage.removeItem(storageKey);
+  }, "webeditor3d.scene-document-draft");
+  await page.reload();
+
+  await page.getByRole("button", { name: "Box Create" }).click();
+  await clickViewport(page, "topLeft");
+  await expect(page.getByRole("button", { name: /Box Brush 1/ })).toBeVisible();
+  await expect(page.getByText("1 brush selected (Box Brush 1)")).toBeVisible();
+
+  await page.getByTestId("viewport-layout-quad").click();
+
+  await expect(page.getByTestId("viewport-panel-topLeft")).toBeVisible();
+  await expect(page.getByTestId("viewport-panel-topRight")).toBeVisible();
+  await expect(page.getByTestId("viewport-panel-bottomLeft")).toBeVisible();
+  await expect(page.getByTestId("viewport-panel-bottomRight")).toBeVisible();
+
+  await expect(page.getByTestId("viewport-panel-topLeft-view-perspective")).toHaveAttribute("aria-pressed", "true");
+  await expect(page.getByTestId("viewport-panel-topLeft-display-normal")).toHaveAttribute("aria-pressed", "true");
+  await expect(page.getByTestId("viewport-panel-topRight-view-top")).toHaveAttribute("aria-pressed", "true");
+  await expect(page.getByTestId("viewport-panel-topRight-display-authoring")).toHaveAttribute("aria-pressed", "true");
+  await expect(page.getByTestId("viewport-panel-bottomLeft-view-front")).toHaveAttribute("aria-pressed", "true");
+  await expect(page.getByTestId("viewport-panel-bottomLeft-display-authoring")).toHaveAttribute("aria-pressed", "true");
+  await expect(page.getByTestId("viewport-panel-bottomRight-view-side")).toHaveAttribute("aria-pressed", "true");
+  await expect(page.getByTestId("viewport-panel-bottomRight-display-authoring")).toHaveAttribute("aria-pressed", "true");
+
+  await page.getByTestId("viewport-panel-topRight-view-side").click();
+  await expect(page.getByTestId("viewport-active-panel")).toContainText("Top Right");
+  await expect(page.getByTestId("viewport-panel-topRight-view-side")).toHaveAttribute("aria-pressed", "true");
+  await expect(page.getByRole("button", { name: /Box Brush 1/ })).toBeVisible();
+
+  await page.getByTestId("viewport-panel-topLeft-display-authoring").click();
+  await expect(page.getByTestId("viewport-active-panel")).toContainText("Top Left");
+  await expect(page.getByTestId("viewport-panel-topLeft-display-authoring")).toHaveAttribute("aria-pressed", "true");
+  await expect(page.getByTestId("viewport-canvas-topLeft")).toHaveCSS("background-color", "rgb(0, 0, 0)");
+  await expect(page.getByText("1 brush selected (Box Brush 1)")).toBeVisible();
+
+  expect(pageErrors).toEqual([]);
+  expect(consoleErrors).toEqual([]);
+});