diff --git a/app/assets/javascripts/discourse/app/instance-initializers/viewport-setup.js b/app/assets/javascripts/discourse/app/instance-initializers/viewport-setup.js
index 55b727809e1..7e2d3f312f9 100644
--- a/app/assets/javascripts/discourse/app/instance-initializers/viewport-setup.js
+++ b/app/assets/javascripts/discourse/app/instance-initializers/viewport-setup.js
@@ -14,11 +14,6 @@ export default {
     }
 
     let value = viewport.getAttribute("content");
-    if (caps.isIOS) {
-      // In iOS Safari, setting user-scalable=no doesn't actually prevent the user from zooming in.
-      // But, it does prevent the annoying 'auto zoom' when focussing input fields with small font-sizes.
-      value += ", user-scalable=no";
-    }
 
     if (!caps.isSafari) {
       // Safari prints a big red warning because it doesn't support this property.
@@ -26,6 +21,39 @@ export default {
       value += ", interactive-widget=resizes-content";
     }
 
+    if (caps.isIOS) {
+      // iOS 'auto-zooms' into inputs with font sizes smaller than 16px. To prevent this,
+      // we use two different strategies.
+      if (caps.isiOSPWA || caps.isAppWebview) {
+        // For PWA/Hub, we lock the viewport zoom temporarily during `focusin` events.
+        // Unfortunately this doesn't catch the case when an input is already autofocussed, but the
+        // keyboard isn't open yet. But it's better than nothing.
+        this.lockViewportDuringFocus(viewport, value);
+      } else {
+        // In the full Safari browser, user-scalable=no doesn't actually prevent the user from zooming in.
+        // So we can keep it in place all the time to prevent the auto-zoom.
+        value += ", user-scalable=no";
+      }
+    }
+
     viewport.setAttribute("content", value);
   },
+
+  lockViewportDuringFocus(viewport, initialValue) {
+    let timer;
+
+    window.addEventListener("focusin", (event) => {
+      if (!["INPUT", "TEXTAREA"].includes(event.target.tagName)) {
+        return;
+      }
+
+      viewport.setAttribute("content", `${initialValue}, user-scalable=no`);
+
+      clearTimeout(timer);
+      timer = setTimeout(
+        () => viewport.setAttribute("content", initialValue),
+        100
+      );
+    });
+  },
 };