diff --git a/frontend/src/styles/charts.css b/frontend/src/styles/charts.css
index e62f9e63..f63828ea 100644
--- a/frontend/src/styles/charts.css
+++ b/frontend/src/styles/charts.css
@@ -9,6 +9,9 @@
 }
 
 .chart-section canvas {
+    /* Chart.js sizes the canvas from its parent; without this a canvas that
+     * was drawn wider than the card keeps the page wide (#703). */
+    max-width: 100%;
     max-height: 300px;
     min-height: 280px;
 }
diff --git a/frontend/src/styles/components.css b/frontend/src/styles/components.css
index d9f1fe6f..f51af1a5 100644
--- a/frontend/src/styles/components.css
+++ b/frontend/src/styles/components.css
@@ -702,6 +702,7 @@ th .column-filter-btn.active {
 /* Filter-status bar (Clear-filters badge + aria-live count) above the table. */
 .recommendations-filter-status {
     display: flex;
+    flex-wrap: wrap;
     align-items: center;
     gap: 0.75rem;
     padding: 0.4rem 0;
@@ -749,7 +750,8 @@ th .column-filter-btn.active {
 .recommendations-action-box {
     position: sticky;
     bottom: 0;
-    height: var(--action-box-height);
+    min-height: var(--action-box-height);
+    flex-wrap: wrap;
     background: var(--cudly-surface);
     border-top: 1px solid var(--cudly-border);
     box-shadow: var(--cudly-shadow-md);
@@ -1235,8 +1237,10 @@ tr.rec-variant-row:hover td:not(.checkbox-col) {
 }
 
 .info-icon .tooltip-text {
-    visibility: hidden;
-    opacity: 0;
+    /* display:none, not visibility:hidden: a hidden absolutely positioned
+     * box still extends the scrollable area and widens the page (#703). */
+    display: none;
+    max-width: calc(100vw - 2rem);
     position: absolute;
     z-index: 1000;
     bottom: 125%;
@@ -1252,7 +1256,6 @@ tr.rec-variant-row:hover td:not(.checkbox-col) {
     line-height: 1.4;
     text-align: left;
     box-shadow: 0 2px 8px rgba(0,0,0,0.2);
-    transition: opacity 0.2s, visibility 0.2s;
     white-space: normal;
 }
 
@@ -1268,8 +1271,7 @@ tr.rec-variant-row:hover td:not(.checkbox-col) {
 }
 
 .info-icon:hover .tooltip-text {
-    visibility: visible;
-    opacity: 1;
+    display: block;
 }
 
 /* Role badge */
diff --git a/frontend/src/styles/responsive.css b/frontend/src/styles/responsive.css
index 4a17ab04..0fbe0ee6 100644
--- a/frontend/src/styles/responsive.css
+++ b/frontend/src/styles/responsive.css
@@ -121,11 +121,6 @@ body.sidebar-open {
         width: 100%;
     }
 
-    table {
-        display: block;
-        overflow-x: auto;
-    }
-
     .modal-content {
         width: 95%;
     }
@@ -352,3 +347,18 @@ body.sidebar-open {
         white-space: nowrap;
     }
 }
+
+/* A wide table scrolls inside its container instead of widening the page
+ * (issue #703). The container, not the table, takes the overflow so a short
+ * table keeps display:table and fills the card. The recommendations list is
+ * excluded: its sticky action box must keep sticking to the viewport, so its
+ * table scrolls itself. */
+:where(div, section, fieldset, form, article):has(> table):not(#recommendations-list) {
+    overflow-x: auto;
+}
+
+#recommendations-list > table {
+    display: block;
+    max-width: 100%;
+    overflow-x: auto;
+}
diff --git a/frontend/src/styles/settings.css b/frontend/src/styles/settings.css
index 85e573c0..ddae897a 100644
--- a/frontend/src/styles/settings.css
+++ b/frontend/src/styles/settings.css
@@ -3,11 +3,13 @@
 .settings-tabs,
 .inventory-subnav {
     display: flex;
+    overflow-x: auto;
     border-bottom: 2px solid var(--cudly-border);
     margin-bottom: 1.5rem;
 }
 
 .sub-tab-btn {
+    flex-shrink: 0;
     padding: 0.65rem 1.25rem;
     background: none;
     border: none;
@@ -66,6 +68,8 @@
 }
 
 .settings-category {
+    /* A fieldset defaults to min-width: min-content, which widens the page. */
+    min-width: 0;
     border: 1px solid var(--cudly-border);
     border-radius: 8px;
     padding: 1.5rem;
@@ -117,6 +121,13 @@
     display: flex;
     align-items: center;
     gap: 1rem;
+    /* A select sizes to its longest option; keep it inside the row. */
+    max-width: 100%;
+    min-width: 0;
+}
+
+.setting-input select {
+    max-width: 100%;
 }
 
 .setting-input input[type="text"],
@@ -451,13 +462,15 @@ select.dirty {
 }
 .group-card-header {
     display: flex;
+    flex-wrap: wrap;
+    gap: 0.5rem;
     justify-content: space-between;
     align-items: flex-start;
     margin-bottom: 0.75rem;
 }
 .group-card-header h4 { margin: 0 0 0.25rem; }
 .group-card-header .group-description { font-size: 0.85rem; color: var(--cudly-text-muted); margin: 0; }
-.group-card-actions { display: flex; gap: 0.5rem; flex-shrink: 0; align-items: center; }
+.group-card-actions { display: flex; flex-wrap: wrap; gap: 0.5rem; min-width: 0; align-items: center; }
 .permission-badge {
     display: inline-block;
     font-size: 0.8rem;
@@ -470,6 +483,9 @@ select.dirty {
 }
 .member-pill {
     display: inline-block;
+    max-width: 100%;
+    box-sizing: border-box;
+    overflow-wrap: anywhere;
     font-size: 0.8rem;
     padding: 0.15rem 0.4rem;
     border-radius: 10px;
@@ -606,3 +622,9 @@ select.dirty {
 tr.override-disabled {
     opacity: 0.55;
 }
+
+/* The matrix scrolls sideways; its absolutely positioned .sr-only cell labels
+ * need this scroller as their containing block or they extend the page. */
+#permission-matrix {
+    position: relative;
+}
diff --git a/frontend/src/users/permissionMatrix.ts b/frontend/src/users/permissionMatrix.ts
index 309a007a..8f4f7eec 100644
--- a/frontend/src/users/permissionMatrix.ts
+++ b/frontend/src/users/permissionMatrix.ts
@@ -18,6 +18,9 @@ const ACTIONS = ['view', 'create', 'update', 'delete', 'execute', 'approve', 'ad
  */
 function renderEmptyState(container: HTMLElement, message: string): void {
   container.textContent = '';
+  container.removeAttribute('tabindex');
+  container.removeAttribute('role');
+  container.removeAttribute('aria-label');
   const p = document.createElement('p');
   p.className = 'empty-state';
   p.textContent = message;
@@ -74,4 +77,9 @@ export function renderPermissionMatrix(groups: APIGroup[], container: HTMLElemen
       </tbody>
     </table>
   `;
+  // The matrix scrolls sideways on narrow screens and has no focusable
+  // content of its own, so the scroll region must be keyboard-reachable.
+  container.setAttribute('tabindex', '0');
+  container.setAttribute('role', 'region');
+  container.setAttribute('aria-label', 'Permission matrix');
 }
diff --git a/frontend/tests-e2e/page-overflow.spec.ts b/frontend/tests-e2e/page-overflow.spec.ts
new file mode 100644
index 00000000..b9cc0edb
--- /dev/null
+++ b/frontend/tests-e2e/page-overflow.spec.ts
@@ -0,0 +1,62 @@
+/**
+ * Page-level horizontal scroll guard (issue #703).
+ *
+ * A wide table, a fieldset's min-content width, a hidden-but-laid-out
+ * tooltip or a non-wrapping toolbar each push the document wider than the
+ * viewport, so the whole page scrolls sideways. jsdom has no layout, so this
+ * runs in Chromium and compares the document's scroll width to the viewport.
+ */
+
+import { test, expect } from '@playwright/test';
+import { mockApi, seedAuth } from './fixtures/recs';
+
+const GROUPS = ['Administrators', 'Purchasers', 'Read-only finance auditors', 'Platform engineering leads'].map((name, i) => ({
+  id: `00000000-0000-5000-8000-00000000000${i + 1}`,
+  name,
+  description: `${name}: a deliberately long description so the group card header has to share its row with the action buttons`,
+  permissions: [{ action: i === 0 ? 'admin' : 'view', resource: i === 0 ? '*' : 'recommendations' }],
+}));
+const USERS = [1, 2, 3].map((n) => ({
+  id: `user-${n}`,
+  email: `long.address.for.user.number.${n}@subdomain.example-company.com`,
+  groups: GROUPS.map((g) => g.id),
+  mfa_enabled: n % 2 === 0,
+  created_at: '2026-07-01T00:00:00Z',
+}));
+
+const PAGES = [
+  '/home',
+  '/opportunities',
+  '/plans',
+  '/purchases',
+  '/inventory',
+  '/admin/general',
+  '/admin/purchasing',
+  '/admin/accounts',
+  '/admin/users',
+];
+const WIDTHS = [1280, 768, 390];
+
+for (const width of WIDTHS) {
+  for (const path of PAGES) {
+    test(`${path} does not scroll horizontally at ${width}px`, async ({ page }) => {
+      await page.setViewportSize({ width, height: 900 });
+      await seedAuth(page);
+      await mockApi(page);
+      // Populated users and groups: empty lists hide the group cards, the
+      // permission matrix and the long user rows that overflow on phones.
+      await page.route('**/api/users', (route) =>
+        route.fulfill({ status: 200, contentType: 'application/json', body: JSON.stringify({ users: USERS }) }),
+      );
+      await page.route('**/api/groups', (route) =>
+        route.fulfill({ status: 200, contentType: 'application/json', body: JSON.stringify({ groups: GROUPS }) }),
+      );
+      await page.goto(path);
+      await page.waitForLoadState('networkidle');
+      const overflow = await page.evaluate(
+        () => document.documentElement.scrollWidth - window.innerWidth,
+      );
+      expect(overflow).toBeLessThanOrEqual(0);
+    });
+  }
+}