diff --git a/packages/block-editor/package.json b/packages/block-editor/package.json
index b53feaad..6b3824c1 100644
--- a/packages/block-editor/package.json
+++ b/packages/block-editor/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@wrnexus/block-editor",
-  "version": "0.1.3",
+  "version": "0.1.4",
   "type": "module",
   "description": "Hydrated accessible editor runtime for WRNexus block documents.",
   "exports": {
diff --git a/packages/block-editor/src/index.ts b/packages/block-editor/src/index.ts
index 8789eccf..0395521a 100644
--- a/packages/block-editor/src/index.ts
+++ b/packages/block-editor/src/index.ts
@@ -1,2 +1,3 @@
 export * from "./state.ts";
 export * from "./runtime.ts";
+export * from "./unsaved.ts";
diff --git a/packages/block-editor/src/unsaved.ts b/packages/block-editor/src/unsaved.ts
new file mode 100644
index 00000000..09dba011
--- /dev/null
+++ b/packages/block-editor/src/unsaved.ts
@@ -0,0 +1,40 @@
+export function mountUnsavedChangesGuard(
+  root: HTMLElement,
+  options: { hasUnsavedChanges(): boolean; confirmLeave(): boolean },
+): { destroy(): void } {
+  const document = root.ownerDocument;
+  const view = document.defaultView!;
+  let destroyed = false;
+  const dirty = () => !destroyed && root.isConnected && options.hasUnsavedChanges();
+  const beforeUnload = (event: BeforeUnloadEvent) => {
+    if (!dirty()) return;
+    event.preventDefault();
+    event.returnValue = "";
+  };
+  const click = (event: MouseEvent) => {
+    if (event.defaultPrevented || event.button !== 0 || event.ctrlKey || event.metaKey || event.shiftKey || event.altKey) return;
+    const target = event.target as Element | null;
+    const link = target?.closest?.("a[href]") as HTMLAnchorElement | null;
+    if (!link || link.hasAttribute("download") || (link.target && link.target !== "_self")) return;
+    const url = new URL(link.href, document.baseURI);
+    if (!["http:", "https:"].includes(url.protocol)) return;
+    const current = new URL(view.location.href);
+    if (url.origin === current.origin && url.pathname === current.pathname && url.search === current.search && url.hash) return;
+    if (dirty() && !options.confirmLeave()) {
+      event.preventDefault();
+      event.stopImmediatePropagation();
+    }
+  };
+  const observer = new view.MutationObserver(() => { if (!root.isConnected) destroy(); });
+  function destroy() {
+    if (destroyed) return;
+    destroyed = true;
+    view.removeEventListener("beforeunload", beforeUnload);
+    document.removeEventListener("click", click, true);
+    observer.disconnect();
+  }
+  view.addEventListener("beforeunload", beforeUnload);
+  document.addEventListener("click", click, true);
+  observer.observe(document.documentElement, { childList: true, subtree: true });
+  return { destroy };
+}
diff --git a/packages/block-editor/test/unsaved.test.ts b/packages/block-editor/test/unsaved.test.ts
new file mode 100644
index 00000000..2b457ce1
--- /dev/null
+++ b/packages/block-editor/test/unsaved.test.ts
@@ -0,0 +1,28 @@
+import { expect, test } from "bun:test";
+import { Window } from "happy-dom";
+import { mountUnsavedChangesGuard } from "../src/unsaved.ts";
+
+test("unsaved guard protects unload and ordinary navigation, permits safe links, and cleans up", () => {
+  const window = new Window({ url: "https://email.example.com/builder/one" });
+  const root = window.document.createElement("main");
+  window.document.body.append(root);
+  let dirty = true, allow = false, confirmations = 0;
+  const guard = mountUnsavedChangesGuard(root as unknown as HTMLElement, { hasUnsavedChanges: () => dirty, confirmLeave: () => { confirmations++; return allow; } });
+  const unload = () => { const event = new window.Event("beforeunload", { cancelable: true }); window.dispatchEvent(event); return event.defaultPrevented; };
+  const click = (href: string, target = "") => {
+    const link = window.document.createElement("a"); link.href = href; link.target = target; root.append(link);
+    const event = new window.MouseEvent("click", { bubbles: true, cancelable: true });
+    link.dispatchEvent(event); return event.defaultPrevented;
+  };
+  expect(unload()).toBe(true);
+  expect(click("/builder/two")).toBe(true);
+  expect(click("#content")).toBe(false);
+  expect(click("/builder/two", "_blank")).toBe(false);
+  expect(confirmations).toBe(1);
+  allow = true;
+  expect(click("/builder/two")).toBe(false);
+  dirty = false;
+  expect(unload()).toBe(false);
+  guard.destroy(); guard.destroy(); dirty = true;
+  expect(unload()).toBe(false);
+});