diff --git a/mail_ux/__manifest__.py b/mail_ux/__manifest__.py
index 9980c4cb..228404f0 100644
--- a/mail_ux/__manifest__.py
+++ b/mail_ux/__manifest__.py
@@ -30,6 +30,7 @@
     "assets": {
         "web.assets_backend": [
             "mail_ux/static/src/core/common/**/*",
+            "mail_ux/static/src/views/composer_onchange.js",
         ],
     },
     "depends": [
diff --git a/mail_ux/static/src/views/composer_onchange.js b/mail_ux/static/src/views/composer_onchange.js
new file mode 100644
index 00000000..86a71d54
--- /dev/null
+++ b/mail_ux/static/src/views/composer_onchange.js
@@ -0,0 +1,27 @@
+import { ORM } from "@web/core/orm_service";
+import { patch } from "@web/core/utils/patch";
+
+// The composer dialog is rebuilt when an overlay (e.g. a tooltip) changes while it loads,
+// which sends the same initial onchange again: reuse the pending one.
+const pendingComposerOnchanges = new Map();
+
+patch(ORM.prototype, {
+    call(model, method, args = [], kwargs = {}) {
+        const isInitialComposerOnchange =
+            model === "mail.compose.message" &&
+            method === "onchange" &&
+            Array.isArray(args[2]) &&
+            !args[2].length;
+        if (!isInitialComposerOnchange) {
+            return super.call(...arguments);
+        }
+        const key = JSON.stringify([args, kwargs]);
+        let prom = pendingComposerOnchanges.get(key);
+        if (!prom) {
+            prom = super.call(...arguments);
+            pendingComposerOnchanges.set(key, prom);
+            prom.finally(() => pendingComposerOnchanges.delete(key)).catch(() => {});
+        }
+        return prom.then((result) => structuredClone(result));
+    },
+});