diff --git a/apps/web/src/pages/home-page.tsx b/apps/web/src/pages/home-page.tsx
index dd1121d0..c070cbff 100644
--- a/apps/web/src/pages/home-page.tsx
+++ b/apps/web/src/pages/home-page.tsx
@@ -13,6 +13,8 @@ import { useSettingsStore } from "@/stores/settings-store";
 // Tools shown prominently as "quick actions" at the top
 const QUICK_ACTION_IDS = ["resize", "compress", "convert", "remove-background"];
 
+let hasAppliedDefaultRedirect = false;
+
 export function HomePage() {
   const {
     setFiles,
@@ -37,7 +39,13 @@ export function HomePage() {
   }, [fetchSettings, fetchFeatures]);
 
   useEffect(() => {
-    if (settingsLoaded && defaultToolView === "fullscreen" && files.length === 0) {
+    if (
+      !hasAppliedDefaultRedirect &&
+      settingsLoaded &&
+      defaultToolView === "fullscreen" &&
+      files.length === 0
+    ) {
+      hasAppliedDefaultRedirect = true;
       navigate("/fullscreen", { replace: true });
     }
   }, [settingsLoaded, defaultToolView, files.length, navigate]);
diff --git a/tests/unit/web/home-page-redirect.test.tsx b/tests/unit/web/home-page-redirect.test.tsx
new file mode 100644
index 00000000..3992340c
--- /dev/null
+++ b/tests/unit/web/home-page-redirect.test.tsx
@@ -0,0 +1,158 @@
+// @vitest-environment jsdom
+import type React from "react";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+
+let settingsState = {
+  fetch: vi.fn(),
+  defaultToolView: "sidebar" as "sidebar" | "fullscreen",
+  loaded: false,
+};
+
+vi.mock("@/stores/settings-store", () => ({
+  useSettingsStore: () => settingsState,
+}));
+
+let fileState = {
+  setFiles: vi.fn(),
+  files: [] as File[],
+  reset: vi.fn(),
+  originalBlobUrl: null as string | null,
+  selectedFileName: null as string | null,
+  selectedFileSize: 0,
+  currentEntry: null,
+};
+
+vi.mock("@/stores/file-store", () => ({
+  useFileStore: () => fileState,
+}));
+
+vi.mock("@/stores/features-store", () => ({
+  useFeaturesStore: () => ({
+    fetch: vi.fn(),
+    bundles: [],
+    installing: {},
+    queued: [],
+  }),
+}));
+
+vi.mock("@/components/layout/app-layout", () => ({
+  AppLayout: ({ children }: React.PropsWithChildren) => (
+    <div data-testid="app-layout">{children}</div>
+  ),
+}));
+
+vi.mock("@/components/common/image-viewer", () => ({
+  ImageViewer: () => null,
+}));
+
+vi.mock("@/components/common/multi-image-viewer", () => ({
+  MultiImageViewer: () => null,
+}));
+
+vi.mock("@/lib/icon-map", () => ({
+  ICON_MAP: new Proxy(
+    {},
+    {
+      get: () => (props: { className?: string }) => <span {...props} />,
+    },
+  ),
+}));
+
+import { act, cleanup, render } from "@testing-library/react";
+import { MemoryRouter, Route, Routes, useLocation } from "react-router-dom";
+import { HomePage } from "@/pages/home-page";
+
+let currentPath = "/";
+
+function LocationSpy() {
+  const location = useLocation();
+  currentPath = location.pathname;
+  return null;
+}
+
+function renderInRouter(initialPath = "/") {
+  currentPath = initialPath;
+  return render(
+    <MemoryRouter initialEntries={[initialPath]}>
+      <LocationSpy />
+      <Routes>
+        <Route path="/" element={<HomePage />} />
+        <Route path="/fullscreen" element={<div data-testid="fullscreen-page" />} />
+      </Routes>
+    </MemoryRouter>,
+  );
+}
+
+afterEach(cleanup);
+
+// Tests are ordered intentionally: the module-level `hasAppliedDefaultRedirect`
+// flag starts false and is set true by the "redirects on first mount" test.
+// Tests before it verify conditions that independently prevent the redirect
+// (so the flag stays false). The final test verifies the flag prevents repeat redirects.
+describe("HomePage default view redirect", () => {
+  beforeEach(() => {
+    settingsState = {
+      fetch: vi.fn(),
+      defaultToolView: "sidebar",
+      loaded: false,
+    };
+    fileState = {
+      setFiles: vi.fn(),
+      files: [],
+      reset: vi.fn(),
+      originalBlobUrl: null,
+      selectedFileName: null,
+      selectedFileSize: 0,
+      currentEntry: null,
+    };
+  });
+
+  it("does NOT redirect when settings have not loaded yet", () => {
+    settingsState.loaded = false;
+    settingsState.defaultToolView = "fullscreen";
+
+    renderInRouter("/");
+
+    expect(currentPath).toBe("/");
+  });
+
+  it("does NOT redirect when default view is sidebar", () => {
+    settingsState.loaded = true;
+    settingsState.defaultToolView = "sidebar";
+
+    renderInRouter("/");
+
+    expect(currentPath).toBe("/");
+  });
+
+  it("does NOT redirect when files are loaded even with fullscreen default", () => {
+    settingsState.loaded = true;
+    settingsState.defaultToolView = "fullscreen";
+    fileState.files = [new File([new ArrayBuffer(1024)], "test.png", { type: "image/png" })];
+    fileState.originalBlobUrl = "blob:fake-url";
+    fileState.selectedFileName = "test.png";
+    fileState.selectedFileSize = 1024;
+
+    renderInRouter("/");
+
+    expect(currentPath).toBe("/");
+  });
+
+  it("redirects to /fullscreen on first mount when default view is fullscreen", () => {
+    settingsState.loaded = true;
+    settingsState.defaultToolView = "fullscreen";
+
+    renderInRouter("/");
+
+    expect(currentPath).toBe("/fullscreen");
+  });
+
+  it("does NOT redirect on subsequent mounts after initial redirect (issue #128)", () => {
+    settingsState.loaded = true;
+    settingsState.defaultToolView = "fullscreen";
+
+    renderInRouter("/");
+
+    expect(currentPath).toBe("/");
+  });
+});
diff --git a/vitest.config.ts b/vitest.config.ts
index 46947e4c..a9c221aa 100644
--- a/vitest.config.ts
+++ b/vitest.config.ts
@@ -108,6 +108,7 @@ export default defineConfig({
       sharp: path.join(apiNodeModules, "sharp"),
       react: path.join(webNodeModules, "react"),
       "react-dom": path.join(webNodeModules, "react-dom"),
+      "react-router-dom": path.join(webNodeModules, "react-router-dom"),
       zustand: path.join(webNodeModules, "zustand"),
       "posthog-js": path.join(webNodeModules, "posthog-js"),
       "@sentry/react": path.join(webNodeModules, "@sentry/react"),