diff --git a/backend/Cargo.lock b/backend/Cargo.lock
index fe500a9..abd821a 100644
--- a/backend/Cargo.lock
+++ b/backend/Cargo.lock
@@ -1558,7 +1558,7 @@ checksum = "c41e0c4fef86961ac6d6f8a82609f55f31b05e4fce149ac5710e439df7619ba4"
 
 [[package]]
 name = "mangalord"
-version = "0.125.0"
+version = "0.125.1"
 dependencies = [
  "anyhow",
  "argon2",
diff --git a/backend/Cargo.toml b/backend/Cargo.toml
index 8827010..26e9647 100644
--- a/backend/Cargo.toml
+++ b/backend/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "mangalord"
-version = "0.125.0"
+version = "0.125.1"
 edition = "2021"
 default-run = "mangalord"
 
diff --git a/frontend/e2e/admin-users.spec.ts b/frontend/e2e/admin-users.spec.ts
new file mode 100644
index 0000000..0433d31
--- /dev/null
+++ b/frontend/e2e/admin-users.spec.ts
@@ -0,0 +1,132 @@
+import { test, expect, type Page } from './fixtures';
+
+// E2E for the admin Users page role toggle: flipping the Admin checkbox is a
+// one-click privilege change, so it must confirm first, and the checkbox must
+// never show a state the server didn't actually apply (cancel or failure keeps
+// it on the true value).
+
+const DESKTOP = { width: 1280, height: 720 } as const;
+
+const adminUser = {
+    id: 'u11111111-1111-1111-1111-111111111111',
+    username: 'admin',
+    created_at: '2026-01-01T00:00:00Z',
+    is_admin: true
+};
+
+const bob = {
+    id: 'b22222222-2222-2222-2222-222222222222',
+    username: 'bob',
+    created_at: '2026-02-01T00:00:00Z',
+    is_admin: false
+};
+
+type Captured = { patched: boolean };
+
+async function mockAdmin(page: Page, cap: Captured, opts: { patchStatus: number }) {
+    await page.route('**/api/v1/auth/config', (r) =>
+        r.fulfill({
+            status: 200,
+            contentType: 'application/json',
+            body: JSON.stringify({ self_register_enabled: true, private_mode: false })
+        })
+    );
+    await page.route('**/api/v1/auth/me', (r) =>
+        r.fulfill({
+            status: 200,
+            contentType: 'application/json',
+            body: JSON.stringify({ user: adminUser })
+        })
+    );
+    await page.route('**/api/v1/auth/me/preferences', (r) =>
+        r.fulfill({
+            status: 200,
+            contentType: 'application/json',
+            body: JSON.stringify({ reader_mode: 'single', reader_page_gap: 'small' })
+        })
+    );
+    await page.route('**/api/v1/me/bookmarks*', (r) =>
+        r.fulfill({
+            status: 200,
+            contentType: 'application/json',
+            body: JSON.stringify({ items: [], page: { limit: 50, offset: 0, total: 0 } })
+        })
+    );
+    await page.route('**/api/v1/admin/system', (r) =>
+        r.fulfill({
+            status: 200,
+            contentType: 'application/json',
+            body: JSON.stringify({
+                disk: null,
+                memory: { total_bytes: 1, used_bytes: 0, percent_used: 0 },
+                cpu: { percent_used: 0 },
+                alerts: []
+            })
+        })
+    );
+    // The PATCH toggle — record whether it was ever sent.
+    await page.route('**/api/v1/admin/users/*', async (r) => {
+        cap.patched = true;
+        await r.fulfill({
+            status: opts.patchStatus,
+            contentType: 'application/json',
+            body:
+                opts.patchStatus < 400
+                    ? JSON.stringify({ ...bob, is_admin: true })
+                    : JSON.stringify({ error: { code: 'internal_error', message: 'boom' } })
+        });
+    });
+    // The user list (registered after the specific PATCH glob; list is GET).
+    await page.route('**/api/v1/admin/users**', async (r) => {
+        if (r.request().method() !== 'GET') return r.fallback();
+        await r.fulfill({
+            status: 200,
+            contentType: 'application/json',
+            body: JSON.stringify({
+                items: [adminUser, bob],
+                page: { limit: 100, offset: 0, total: 2 }
+            })
+        });
+    });
+}
+
+test.describe('/admin/users role toggle', () => {
+    test('cancelling the confirm leaves the checkbox unchanged and sends no request', async ({
+        page
+    }) => {
+        const cap: Captured = { patched: false };
+        await mockAdmin(page, cap, { patchStatus: 200 });
+        page.on('dialog', (d) => d.dismiss());
+        await page.setViewportSize(DESKTOP);
+        await page.goto('/admin/users');
+
+        const bobRow = page.locator('tr', { hasText: 'bob' });
+        const checkbox = bobRow.getByLabel('admin');
+        await expect(checkbox).not.toBeChecked();
+
+        await checkbox.click();
+
+        // Cancelled → no PATCH, and the box still reflects the server state.
+        await expect(checkbox).not.toBeChecked();
+        expect(cap.patched).toBe(false);
+    });
+
+    test('a failed toggle reverts the checkbox to the server state', async ({ page }) => {
+        const cap: Captured = { patched: false };
+        await mockAdmin(page, cap, { patchStatus: 500 });
+        page.on('dialog', (d) => d.accept());
+        await page.setViewportSize(DESKTOP);
+        await page.goto('/admin/users');
+
+        const bobRow = page.locator('tr', { hasText: 'bob' });
+        const checkbox = bobRow.getByLabel('admin');
+        await expect(checkbox).not.toBeChecked();
+
+        await checkbox.click();
+
+        // The PATCH was attempted and failed → the checkbox must snap back to
+        // the actual (still non-admin) server state rather than stay flipped.
+        await expect.poll(() => cap.patched).toBe(true);
+        await expect(checkbox).not.toBeChecked();
+    });
+});
diff --git a/frontend/package.json b/frontend/package.json
index d6441aa..1a63e12 100644
--- a/frontend/package.json
+++ b/frontend/package.json
@@ -1,6 +1,6 @@
 {
   "name": "mangalord-frontend",
-  "version": "0.125.0",
+  "version": "0.125.1",
   "private": true,
   "type": "module",
   "scripts": {
diff --git a/frontend/src/routes/admin/users/+page.svelte b/frontend/src/routes/admin/users/+page.svelte
index 9e1e836..162c1c0 100644
--- a/frontend/src/routes/admin/users/+page.svelte
+++ b/frontend/src/routes/admin/users/+page.svelte
@@ -51,12 +51,19 @@
     }
 
     async function onToggleAdmin(id: string, next: boolean) {
+        // Privilege changes are one-click and consequential — confirm first,
+        // like Delete. The checkbox is kept controlled by `u.is_admin` (see the
+        // onchange handler), so a cancel here leaves it showing the true state.
+        const verb = next ? 'grant admin rights to' : 'revoke admin rights from';
+        if (!confirm(`Are you sure you want to ${verb} this user?`)) return;
         busyId = id;
         try {
             await setUserAdmin(id, next);
             await load();
         } catch (e) {
             error = e instanceof ApiError ? e.message : 'update failed';
+            // The checkbox was reverted in onchange and `u.is_admin` is
+            // unchanged, so it correctly still reflects the server state.
         } finally {
             busyId = null;
         }
@@ -187,7 +194,15 @@
                             type="checkbox"
                             checked={u.is_admin}
                             disabled={busyId === u.id || isSelf}
-                            onchange={(e) => onToggleAdmin(u.id, e.currentTarget.checked)}
+                            onchange={(e) => {
+                                const desired = e.currentTarget.checked;
+                                // Keep the box controlled by `u.is_admin`: undo the
+                                // optimistic flip so it only changes once the server
+                                // confirms — and never lies if the change is
+                                // cancelled or the request fails.
+                                e.currentTarget.checked = u.is_admin;
+                                onToggleAdmin(u.id, desired);
+                            }}
                             aria-label="admin"
                         />
                     </td>