diff --git a/src/gui/src/IPC.js b/src/gui/src/IPC.js
index 7991bd817..2475e9582 100644
--- a/src/gui/src/IPC.js
+++ b/src/gui/src/IPC.js
@@ -1314,8 +1314,10 @@ const ipc_listener = async (event, handled) => {
     else if ( event.data.msg === 'requestPermission' ) {
         // Always respond, even on validation/auth failure, so the SDK's
         // promise settles instead of hanging forever.
+        // The app can close its own window while the dialog is up, which
+        // tears down the iframe — posting into it must not throw.
         const respond = (granted) => {
-            target_iframe.contentWindow.postMessage({
+            target_iframe?.contentWindow?.postMessage({
                 msg: 'permissionGranted',
                 granted: granted,
                 original_msg_id: msg_id,
@@ -1351,7 +1353,7 @@ const ipc_listener = async (event, handled) => {
 
         // report the user's decision to the requester window
         respond(granted === true);
-        $(target_iframe).get(0).focus({ preventScroll: true });
+        $(target_iframe).get(0)?.focus({ preventScroll: true });
     }
     //--------------------------------------------------------
     // showFontPicker
diff --git a/src/gui/src/initgui.js b/src/gui/src/initgui.js
index a02fa8b6b..629509499 100644
--- a/src/gui/src/initgui.js
+++ b/src/gui/src/initgui.js
@@ -465,15 +465,17 @@ const postAuthActions = async (action) => {
         // promise pending until the user closes it by hand.
         let granted = false;
         try {
-            // Identify the requesting app by its origin rather than trusting a
-            // caller-supplied uid, falling back to the query param otherwise.
-            let app_uid = window.url_query_params.get('app_uid') ?? undefined;
+            // The requesting app is identified by its origin only. A uid from
+            // the query string is never trusted: it is chosen by whoever
+            // opened this page, so honouring it would let a link grant a
+            // permission to an app the dialog never named. When the origin
+            // can't be resolved here, the uid is left unset and the server
+            // resolves it from the same origin the dialog displayed.
+            let app_uid;
             if ( origin ) {
-                try {
-                    app_uid = window.host_app_uid ?? await window.getAppUIDFromOrigin(origin);
-                } catch (e) {
-                    // Keep the query-param fallback.
-                }
+                app_uid = window.host_app_uid
+                    ?? await window.getAppUIDFromOrigin(origin)
+                    ?? undefined;
             }
 
             granted = await UIPermissionDialog({
diff --git a/src/puter-js/src/modules/PuterDialog.js b/src/puter-js/src/modules/PuterDialog.js
index 1236366cd..c97ecc4ca 100644
--- a/src/puter-js/src/modules/PuterDialog.js
+++ b/src/puter-js/src/modules/PuterDialog.js
@@ -16,6 +16,10 @@ class PuterDialog extends (globalThis.HTMLElement || Object) { // It will fall b
      *   implicit-auth URL), skips the `puter.token` message handling and
      *   `puterAuthState` bookkeeping (the caller owns the auth result), and
      *   reports cancellation through `options.onCancel`.
+     * @param {string} [options.popupName] - Window name for the popup. Give
+     *   each concurrent launcher a distinct name: `window.open()` reuses a
+     *   window that already carries the requested name, so sharing one name
+     *   navigates (and hijacks) a popup another pending flow is waiting on.
      * @param {Function} [options.onLaunch] - Called with the opened popup
      *   window (or null if the browser blocked it) right after launch.
      * @param {Function} [options.onCancel] - Called when the user dismisses
@@ -528,7 +532,7 @@ class PuterDialog extends (globalThis.HTMLElement || Object) { // It will fall b
         // Wire the "Continue" button to open the auth popup. Opening here is
         // safe from being popup-blocked because it happens inside a click.
         this.shadowRoot.querySelector('#launch-auth-popup')?.addEventListener('click', () => {
-            const popup = openAuthPopup(this.#popupURL());
+            const popup = this.#openPopup();
             // Pinned as the expected event.source in messageListener.
             this.authPopup = popup;
 
@@ -553,9 +557,20 @@ class PuterDialog extends (globalThis.HTMLElement || Object) { // It will fall b
         this.shadowRoot.querySelector('.close-btn')?.addEventListener('click', this.cancelListener);
     }
 
+    /**
+     * Opens the popup under the caller's window name when one was given, so
+     * concurrent launchers don't reuse (and steal) each other's window.
+     * @returns {Window|null}
+     */
+    #openPopup () {
+        return this.options.popupName
+            ? openAuthPopup(this.#popupURL(), this.options.popupName)
+            : openAuthPopup(this.#popupURL());
+    }
+
     open () {
         if ( hasUserActivation() ) {
-            const popup = openAuthPopup(this.#popupURL());
+            const popup = this.#openPopup();
             // Pinned as the expected event.source in messageListener.
             this.authPopup = popup;
             if ( this.options.popupURL && typeof this.options.onLaunch === 'function' ) {
diff --git a/src/puter-js/src/modules/UI.js b/src/puter-js/src/modules/UI.js
index d8671e287..6b0e4edd0 100644
--- a/src/puter-js/src/modules/UI.js
+++ b/src/puter-js/src/modules/UI.js
@@ -1245,6 +1245,8 @@ class UI extends EventListener {
                 // the gesture the browser requires.
                 const dialog = new PuterDialog(() => {}, () => {}, {
                     popupURL: url,
+                    // Same unique-name reasoning as the direct path above.
+                    popupName: `puter-permission-${msg_id}`,
                     onLaunch: (popup) => watchPopup(popup),
                     onCancel: () => settle(false),
                 });
diff --git a/src/puter-js/tests/e2e/specs/requestPermission.spec.js b/src/puter-js/tests/e2e/specs/requestPermission.spec.js
index ca942279c..e49d391fa 100644
--- a/src/puter-js/tests/e2e/specs/requestPermission.spec.js
+++ b/src/puter-js/tests/e2e/specs/requestPermission.spec.js
@@ -209,3 +209,20 @@ test.describe('puter.ui.requestPermission (env=web popup)', () => {
         await expect(page.locator('#log [data-entry="perm:driver:false"]')).toBeVisible();
     });
 });
+
+test.describe('request-permission action hardening', () => {
+    test('an app_uid in the URL never produces a prompt on its own', async ({ page }) => {
+        // The uid identifies who receives the grant, so it must come from the
+        // requesting origin — never from the link. A link carrying only a uid
+        // would otherwise prompt for an unnamed requester and grant to an app
+        // the dialog never showed the user.
+        await page.goto(
+            '/action/request-permission?permission=driver%3Aputer-image-generation%3Agenerate' +
+                '&app_uid=app-00000000-0000-4000-8000-000000000000',
+        );
+        await page.waitForFunction(() => !!window.puter?.authToken, null, { timeout: 60_000 });
+        // Give the post-auth action a chance to run before asserting absence.
+        await page.locator('.desktop').waitFor({ timeout: 60_000 });
+        await expect(page.locator('dialog.perm-dialog')).toHaveCount(0);
+    });
+});