diff --git a/CHANGELOG.md b/CHANGELOG.md
index 443dcc3..a249395 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Frontend uses `@cryptgeon/shared` for crypto + payload codec (replacing the previous local `cryptgeon/shared`); heavy pack/unpack runs in a web worker.
 - CLI rebuilt with `vite-plus` (bundles all deps) and imports from `@cryptgeon/shared`.
 
+### Fixed
+
+- SPA fallback now serves the app (200) for client-side routes such as `/about` and `/note/<id>`, while unmatched `/api/*` paths still return 404.
+
 ### Breaking changes
 
 - Endpoints moved to `/api/v3/notes/` and `/api/v3/status`; health check to `/healthz`.
diff --git a/packages/backend/src/main.rs b/packages/backend/src/main.rs
index ff27313..bbab6ec 100644
--- a/packages/backend/src/main.rs
+++ b/packages/backend/src/main.rs
@@ -20,6 +20,10 @@ mod note;
 mod status;
 mod store;
 
+async fn api_not_found() -> axum::http::StatusCode {
+    axum::http::StatusCode::NOT_FOUND
+}
+
 #[tokio::main]
 async fn main() {
     dotenv().ok();
@@ -39,11 +43,13 @@ async fn main() {
         .nest("/notes", notes_routes)
         .merge(status_routes);
 
-    let api_routes = Router::new().nest("/v3", v3_routes);
+    let api_routes = Router::new()
+        .nest("/v3", v3_routes)
+        .fallback(api_not_found);
 
     let index = format!("{}{}", config::FRONTEND_PATH.to_string(), "/index.html");
     let serve_dir =
-        ServeDir::new(config::FRONTEND_PATH.to_string()).not_found_service(ServeFile::new(index));
+        ServeDir::new(config::FRONTEND_PATH.to_string()).fallback(ServeFile::new(index));
     let app = Router::new()
         .nest("/api", api_routes)
         .merge(health_routes)
@@ -66,4 +72,4 @@ async fn main() {
     axum::serve(listener, ServiceExt::<Request>::into_make_service(app))
         .await
         .unwrap();
-}
\ No newline at end of file
+}
diff --git a/test/web/spa-fallback.spec.ts b/test/web/spa-fallback.spec.ts
new file mode 100644
index 0000000..28a2c51
--- /dev/null
+++ b/test/web/spa-fallback.spec.ts
@@ -0,0 +1,15 @@
+import { expect, test } from "@playwright/test";
+
+test.describe("@web", () => {
+  for (const path of ["/", "/about", "/note/does-not-exist"]) {
+    test(`serves ${path} with status 200`, async ({ request }) => {
+      const response = await request.get(path);
+      expect(response.status()).toBe(200);
+    });
+  }
+
+  test("api still reports a missing note as 404", async ({ request }) => {
+    const response = await request.get("/api/notes/does-not-exist");
+    expect(response.status()).toBe(404);
+  });
+});