diff --git a/specs/01-architecture.md b/specs/01-architecture.md
index e741187c..f676de84 100644
--- a/specs/01-architecture.md
+++ b/specs/01-architecture.md
@@ -475,6 +475,13 @@ development) from one origin; there is no separate host app.
   source `icons/og.webp`): absolute, as crawlers need, and versioned in its name because
   `/web/` is served as immutable — a new image gets a new name. The legal pages carry the
   same tags with their own `og:url` and canonical link.
+- **No Grammarly**: the apps check spelling themselves (`wonky_spellcheck`), and Grammarly's
+  overlays on Flutter's hidden text fields interfere with editing. Each app's `web/index.html`
+  opts out: `data-gramm="false" data-gramm_editor="false" data-enable-grammarly="false"` on
+  `<html>` and `<body>`, and an inline script puts the same attributes on every `input`,
+  `textarea` and `contenteditable` that Flutter adds (MutationObserver) and on the focused field
+  (capturing `focusin`, which runs before the extension's own handler). A new app's
+  `index.html` copies the attributes and the script.
 - **Development**: the apps are declared in `serverpod: flutter_apps:` in the server pubspec
   (aliases `drive`, `write`, `sheets`, `slides`; `path: ../wonky_<app>`,
   `target: lib/driver.dart`, fixed `web-port`s so the origins are stable for
diff --git a/wonky_drive/web/index.html b/wonky_drive/web/index.html
index aa7db196..9943b456 100644
--- a/wonky_drive/web/index.html
+++ b/wonky_drive/web/index.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html lang="en">
+<html lang="en" data-gramm="false" data-gramm_editor="false" data-enable-grammarly="false">
 <head>
   <!--
     If you are serving your web app in a path other than the root, change the
@@ -53,7 +53,33 @@
   <title>Wonky Drive</title>
   <link rel="manifest" href="manifest.json">
 </head>
-<body>
+<body data-gramm="false" data-gramm_editor="false" data-enable-grammarly="false">
+  <script>
+    // Keep Grammarly and similar extensions out (specs/01 §2.4): the apps
+    // have their own spelling, and the extension's overlays fight Flutter's
+    // hidden text fields. <html> and <body> opt the page out; Flutter creates
+    // the fields on demand, so each one is tagged when added and on focus.
+    (function () {
+      var fields = 'input, textarea, [contenteditable]';
+      function tag(el) {
+        el.setAttribute('data-gramm', 'false');
+        el.setAttribute('data-gramm_editor', 'false');
+        el.setAttribute('data-enable-grammarly', 'false');
+      }
+      new MutationObserver(function (records) {
+        records.forEach(function (r) {
+          r.addedNodes.forEach(function (n) {
+            if (n.nodeType !== 1) return;
+            if (n.matches(fields)) tag(n);
+            n.querySelectorAll(fields).forEach(tag);
+          });
+        });
+      }).observe(document.body, { childList: true, subtree: true });
+      window.addEventListener('focusin', function (e) {
+        if (e.target.matches && e.target.matches(fields)) tag(e.target);
+      }, true);
+    })();
+  </script>
   <!--
     You can customize the "flutter_bootstrap.js" script.
     This is useful to provide a custom configuration to the Flutter loader
diff --git a/wonky_sheets/web/index.html b/wonky_sheets/web/index.html
index 8658130b..7aa1041c 100644
--- a/wonky_sheets/web/index.html
+++ b/wonky_sheets/web/index.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html lang="en">
+<html lang="en" data-gramm="false" data-gramm_editor="false" data-enable-grammarly="false">
 <head>
   <!--
     If you are serving your web app in a path other than the root, change the
@@ -52,7 +52,33 @@
   <title>Wonky Sheets</title>
   <link rel="manifest" href="manifest.json">
 </head>
-<body>
+<body data-gramm="false" data-gramm_editor="false" data-enable-grammarly="false">
+  <script>
+    // Keep Grammarly and similar extensions out (specs/01 §2.4): the apps
+    // have their own spelling, and the extension's overlays fight Flutter's
+    // hidden text fields. <html> and <body> opt the page out; Flutter creates
+    // the fields on demand, so each one is tagged when added and on focus.
+    (function () {
+      var fields = 'input, textarea, [contenteditable]';
+      function tag(el) {
+        el.setAttribute('data-gramm', 'false');
+        el.setAttribute('data-gramm_editor', 'false');
+        el.setAttribute('data-enable-grammarly', 'false');
+      }
+      new MutationObserver(function (records) {
+        records.forEach(function (r) {
+          r.addedNodes.forEach(function (n) {
+            if (n.nodeType !== 1) return;
+            if (n.matches(fields)) tag(n);
+            n.querySelectorAll(fields).forEach(tag);
+          });
+        });
+      }).observe(document.body, { childList: true, subtree: true });
+      window.addEventListener('focusin', function (e) {
+        if (e.target.matches && e.target.matches(fields)) tag(e.target);
+      }, true);
+    })();
+  </script>
   <!--
     You can customize the "flutter_bootstrap.js" script.
     This is useful to provide a custom configuration to the Flutter loader
diff --git a/wonky_slides/web/index.html b/wonky_slides/web/index.html
index 7815ae58..18aedf0e 100644
--- a/wonky_slides/web/index.html
+++ b/wonky_slides/web/index.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html lang="en">
+<html lang="en" data-gramm="false" data-gramm_editor="false" data-enable-grammarly="false">
 <head>
   <!--
     If you are serving your web app in a path other than the root, change the
@@ -52,7 +52,33 @@
   <title>Wonky Slides</title>
   <link rel="manifest" href="manifest.json">
 </head>
-<body>
+<body data-gramm="false" data-gramm_editor="false" data-enable-grammarly="false">
+  <script>
+    // Keep Grammarly and similar extensions out (specs/01 §2.4): the apps
+    // have their own spelling, and the extension's overlays fight Flutter's
+    // hidden text fields. <html> and <body> opt the page out; Flutter creates
+    // the fields on demand, so each one is tagged when added and on focus.
+    (function () {
+      var fields = 'input, textarea, [contenteditable]';
+      function tag(el) {
+        el.setAttribute('data-gramm', 'false');
+        el.setAttribute('data-gramm_editor', 'false');
+        el.setAttribute('data-enable-grammarly', 'false');
+      }
+      new MutationObserver(function (records) {
+        records.forEach(function (r) {
+          r.addedNodes.forEach(function (n) {
+            if (n.nodeType !== 1) return;
+            if (n.matches(fields)) tag(n);
+            n.querySelectorAll(fields).forEach(tag);
+          });
+        });
+      }).observe(document.body, { childList: true, subtree: true });
+      window.addEventListener('focusin', function (e) {
+        if (e.target.matches && e.target.matches(fields)) tag(e.target);
+      }, true);
+    })();
+  </script>
   <!--
     You can customize the "flutter_bootstrap.js" script.
     This is useful to provide a custom configuration to the Flutter loader
diff --git a/wonky_write/web/index.html b/wonky_write/web/index.html
index efb58382..a3b71802 100644
--- a/wonky_write/web/index.html
+++ b/wonky_write/web/index.html
@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html lang="en">
+<html lang="en" data-gramm="false" data-gramm_editor="false" data-enable-grammarly="false">
 <head>
   <!--
     If you are serving your web app in a path other than the root, change the
@@ -68,7 +68,33 @@
     @media (prefers-reduced-motion: reduce) { #wonky-splash .tile { animation: none; } }
   </style>
 </head>
-<body>
+<body data-gramm="false" data-gramm_editor="false" data-enable-grammarly="false">
+  <script>
+    // Keep Grammarly and similar extensions out (specs/01 §2.4): the apps
+    // have their own spelling, and the extension's overlays fight Flutter's
+    // hidden text fields. <html> and <body> opt the page out; Flutter creates
+    // the fields on demand, so each one is tagged when added and on focus.
+    (function () {
+      var fields = 'input, textarea, [contenteditable]';
+      function tag(el) {
+        el.setAttribute('data-gramm', 'false');
+        el.setAttribute('data-gramm_editor', 'false');
+        el.setAttribute('data-enable-grammarly', 'false');
+      }
+      new MutationObserver(function (records) {
+        records.forEach(function (r) {
+          r.addedNodes.forEach(function (n) {
+            if (n.nodeType !== 1) return;
+            if (n.matches(fields)) tag(n);
+            n.querySelectorAll(fields).forEach(tag);
+          });
+        });
+      }).observe(document.body, { childList: true, subtree: true });
+      window.addEventListener('focusin', function (e) {
+        if (e.target.matches && e.target.matches(fields)) tag(e.target);
+      }, true);
+    })();
+  </script>
   <div id="wonky-splash" aria-label="Loading Wonky Write">
     <img class="tile" src="icons/Icon-192.png" alt="" aria-hidden="true">
     <div>Wonky Write</div>