diff --git a/backend/scripts/seed-skills/building-apps.md b/backend/scripts/seed-skills/building-apps.md
index 673445999..12b74d610 100644
--- a/backend/scripts/seed-skills/building-apps.md
+++ b/backend/scripts/seed-skills/building-apps.md
@@ -825,6 +825,26 @@ cleans sessions up on navigation. Never probe or fall back to the blocked
 browser API from the opaque frame. The complete contract lives in the platform
 `CAPABILITIES.md`.
 
+## Local zoom surfaces
+
+The Möbius shell keeps its toolbar, drawer, chat, and app frame at one stable
+page scale on touch devices. An app that genuinely needs zoom—a map, image,
+canvas, diagram, or document—owns it **inside that specific surface**:
+
+- put `touch-action: none` on the zoomable content surface, not on the app root;
+- use Pointer Events to track a two-pointer distance and transform only the
+  content inside that surface;
+- keep surrounding controls and ordinary reading regions on native pan/tap
+  behavior;
+- provide visible zoom-in, zoom-out, and reset controls (plus keyboard
+  equivalents where relevant), so pinch is never the only way to enlarge
+  content.
+
+Do not add `user-scalable=no` or a maximum scale to the app frame, and do not
+try to zoom the parent document. The shared frame intentionally leaves that
+policy out: each app decides whether it needs a local zoom interaction, while
+the shell chrome remains fixed.
+
 ---
 
 ## Agent-powered mini-apps
diff --git a/frontend/index.html b/frontend/index.html
index 7262ff52a..88ccfa73b 100644
--- a/frontend/index.html
+++ b/frontend/index.html
@@ -2,7 +2,10 @@
 <html lang="en">
   <head>
     <meta charset="UTF-8" />
-    <meta name="viewport" content="width=device-width, initial-scale=1.0, viewport-fit=cover, interactive-widget=resizes-content" />
+    <!-- Möbius chrome is a fixed application surface. Browser page zoom would
+         scale the toolbar and drawer with the active app; zoomable content owns
+         its gesture locally so it can transform without moving the shell. -->
+    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1, user-scalable=no, viewport-fit=cover, interactive-widget=resizes-content" />
     <!-- Default theme-color; applyTheme updates this to the active theme's --bg. -->
     <meta name="theme-color" content="#0d0d0d" />
     <!-- Android/Chrome consults color-scheme before JS/CSS fully applies.
diff --git a/frontend/public/app-frame.html b/frontend/public/app-frame.html
index b934f914d..e927abfa6 100644
--- a/frontend/public/app-frame.html
+++ b/frontend/public/app-frame.html
@@ -329,8 +329,9 @@
        News report renders in its own iframe, so its body text is unaffected. */
     body { -webkit-user-select: none; user-select: none; }
     input, textarea, [contenteditable], [contenteditable] * { -webkit-user-select: text; user-select: text; }
-    /* Keep taps responsive while preserving the browser's native pinch zoom.
-       Custom gesture surfaces can still opt into touch-action:none locally. */
+    /* Keep ordinary taps and pans responsive. The parent shell owns the page
+       viewport; a map, image, canvas, or document that needs zoom opts its own
+       surface into touch-action:none and transforms only that content. */
     html, body { touch-action: manipulation; }
     html, body, #root { height: 100%; }
     /* The shell keeps the selected app painted behind its drawer scrim, but the
diff --git a/frontend/src/components/Shell/Shell.css b/frontend/src/components/Shell/Shell.css
index accab1997..6ff5fc31e 100644
--- a/frontend/src/components/Shell/Shell.css
+++ b/frontend/src/components/Shell/Shell.css
@@ -87,11 +87,12 @@
   /* The rAF-written hold progress [0..1]; the hold ring reads it via the cascade
      (builder-mode control below). */
   --hold-progress: 0;
-  /* Suppress the double-tap zoom on the logo while KEEPING vertical scroll and
-     pinch zoom — only the horizontal swipe is owned here; viewport zoom is never
-     disabled globally. The callout/selection is suppressed so a press-and-hold
-     activates builder mode instead of raising a menu (the JS also preventDefaults
-     contextmenu during a hold). */
+  /* Suppress double-tap zoom on the logo while keeping this component's gesture
+     declaration local: vertical pan and pinch remain allowed here, then the
+     shell root applies the page-level pinch policy once for the whole document.
+     The callout/selection is suppressed so a press-and-hold activates builder
+     mode instead of raising a menu (the JS also preventDefaults contextmenu
+     during a hold). */
   touch-action: pan-y pinch-zoom;
   -webkit-touch-callout: none;
 }
diff --git a/frontend/src/components/Shell/__tests__/workspaceUi.test.js b/frontend/src/components/Shell/__tests__/workspaceUi.test.js
index 63856a6ab..a35fdaa6f 100644
--- a/frontend/src/components/Shell/__tests__/workspaceUi.test.js
+++ b/frontend/src/components/Shell/__tests__/workspaceUi.test.js
@@ -623,7 +623,7 @@ test('the logo keeps the stable "Toggle navigation" name; gesture rides aria-des
   assert.match(shellBrand, /builderModeActive \? 'Builder mode' : 'Single screen'/)
 })
 
-test('mobile tab bodies pan while preserving pinch zoom and the kind icon owns either-axis dragging', () => {
+test('tab gesture rules stay local while the shell root owns page zoom', () => {
   assert.match(shellCss, /\.shell__tabstrip\s*\{[\s\S]*?touch-action:\s*pan-x pinch-zoom/)
   assert.match(shellCss, /\.shell__tab-open\[data-drag-key\]\s*\{[\s\S]*?touch-action:\s*pan-x pinch-zoom/)
   assert.match(shellCss, /\.shell__tab-kind\[data-touch-drag-handle\]\s*\{[\s\S]*?touch-action:\s*none/)
diff --git a/frontend/src/index.css b/frontend/src/index.css
index 21a27728c..84d814a1e 100644
--- a/frontend/src/index.css
+++ b/frontend/src/index.css
@@ -259,10 +259,13 @@ html {
   background-color: var(--bg, #0d0d0d);
 }
 
-/* Keep taps responsive while preserving native pinch zoom. Elements that own
-   a custom gesture (for example the image lightbox) override this locally. */
+/* The shell is fixed chrome: pan normally, but never let page-level pinch zoom
+   scale the toolbar, drawer, chat, and active app as one document. The viewport
+   meta is the primary lock; this closes the iOS gap where user-scalable=no may
+   be ignored. Local zoom surfaces still own their gesture with touch-action:none
+   and transform only their content. */
 html, body {
-  touch-action: manipulation;
+  touch-action: pan-x pan-y;
 }
 
 /* Accessibility: respect prefers-reduced-motion. Collapses all
diff --git a/frontend/src/lib/__tests__/shellViewportZoom.test.js b/frontend/src/lib/__tests__/shellViewportZoom.test.js
index ea31c7d83..2ed0ce997 100644
--- a/frontend/src/lib/__tests__/shellViewportZoom.test.js
+++ b/frontend/src/lib/__tests__/shellViewportZoom.test.js
@@ -1,20 +1,51 @@
-/* The top-level Möbius viewport preserves native accessibility zoom. */
+/* Browser zoom never scales the Möbius shell chrome; each app owns local zoom. */
 import test from 'node:test'
 import assert from 'node:assert/strict'
 import { readFileSync } from 'node:fs'
 
 const indexHtml = readFileSync(new URL('../../../index.html', import.meta.url), 'utf8')
 const indexCss = readFileSync(new URL('../../index.css', import.meta.url), 'utf8')
+const appFrameHtml = readFileSync(new URL('../../../public/app-frame.html', import.meta.url), 'utf8')
+const buildingApps = readFileSync(
+  new URL('../../../../backend/scripts/seed-skills/building-apps.md', import.meta.url),
+  'utf8',
+)
 
-test('the shell viewport preserves native pinch zoom', () => {
-  const viewport = indexHtml.match(/<meta name="viewport" content="([^"]+)"/)?.[1] || ''
+function viewportContent(html) {
+  return html.match(/<meta name="viewport" content="([^"]+)"/)?.[1] || ''
+}
+
+test('browser pinch cannot scale the shell chrome and active app together', () => {
+  const viewport = viewportContent(indexHtml)
   assert.match(viewport, /width=device-width/)
   assert.match(viewport, /initial-scale=1(?:\.0)?/)
-  assert.doesNotMatch(viewport, /maximum-scale/)
-  assert.doesNotMatch(viewport, /user-scalable/)
+  assert.match(viewport, /maximum-scale=1/)
+  assert.match(viewport, /user-scalable=no/)
   assert.match(viewport, /viewport-fit=cover/)
   assert.match(viewport, /interactive-widget=resizes-content/)
 
   const rootTouchRule = indexCss.match(/html,\s*body\s*\{[\s\S]*?\}/)?.[0] || ''
-  assert.match(rootTouchRule, /touch-action:\s*manipulation/)
+  assert.match(rootTouchRule, /touch-action:\s*pan-x pan-y/)
+  assert.doesNotMatch(rootTouchRule, /pinch-zoom|manipulation/)
+})
+
+test('the app frame adds no second viewport lock and leaves local zoom to the app', () => {
+  const viewport = viewportContent(appFrameHtml)
+  assert.match(viewport, /width=device-width/)
+  assert.match(viewport, /initial-scale=1(?:\.0)?/)
+  // The shared app frame must NOT globally forbid zoom — that choice belongs to
+  // each app's own surface (touch-action:none + transform on its own content).
+  assert.doesNotMatch(viewport, /user-scalable=no/)
+  assert.doesNotMatch(viewport, /maximum-scale=1/)
+
+  const frameRootTouchRule = appFrameHtml.match(/html,\s*body\s*\{\s*touch-action:[^}]+\}/)?.[0] || ''
+  assert.doesNotMatch(frameRootTouchRule, /touch-action:\s*pan-x pan-y/)
+})
+
+test('app authors are told to zoom content locally, with an accessible control path', () => {
+  assert.match(buildingApps, /## Local zoom surfaces/)
+  assert.match(buildingApps, /touch-action: none/)
+  assert.match(buildingApps, /transform only the\s+content/)
+  assert.match(buildingApps, /zoom-in, zoom-out, and reset controls/)
+  assert.match(buildingApps, /Do not add `user-scalable=no`/)
 })
