diff --git a/html/css/app.css b/html/css/app.css
index a72f7cb..f920023 100644
--- a/html/css/app.css
+++ b/html/css/app.css
@@ -334,6 +334,16 @@ a:hover { color: var(--accent-hover); text-decoration: underline; }
     color: #b91c1c;
 }
 
+/* Right-aligned row of buttons directly below a picker (e.g. the "Save
+   selection to favorites" affordance under the Additional groups
+   picker). Sits between the picker and its hint. */
+.fieldActions {
+    display: flex;
+    justify-content: flex-end;
+    gap: 0.5em;
+    margin-top: 0.4em;
+}
+
 /* Chip strip: compact list of removable pills used by the "Manage
    favorites" affordance below the favorite-groups picker. Chips are
    click-target friendly on touch (min 32px tall) and truncate long
diff --git a/html/sendMessage.html b/html/sendMessage.html
index e087d66..d61162a 100644
--- a/html/sendMessage.html
+++ b/html/sendMessage.html
@@ -60,13 +60,17 @@
                     <select id="favGroups" multiple name="favGroups" placeholder="Favorite groups"
                         data-silent-initial-value-set="false"></select>
                     <div id="favGroupsManager" class="chipStrip hidden" aria-label="Manage favorite groups"></div>
-                    <span class="hint">Selecting a group under <em>Additional groups</em> saves it to your favorites. Click the × on a chip to remove that favorite.</span>
+                    <span class="hint">Pick the favorites you want for this message. Click the × on a chip to remove a favorite you no longer use.</span>
                 </div>
 
                 <div class="field">
                     <label for="newGroups">Additional groups</label>
                     <select id="newGroups" multiple name="newGroups" placeholder="Search all groups"
                         data-silent-initial-value-set="false"></select>
+                    <div class="fieldActions">
+                        <button type="button" id="saveFavoritesBtn" class="btn btn-secondary" onclick="saveSelectionToFavorites()">Save selection to favorites</button>
+                    </div>
+                    <span class="hint">Pick any additional org groups for this message. They stay one-off unless you save them.</span>
                 </div>
 
                 <div class="field">
diff --git a/html/sendMessage.js b/html/sendMessage.js
index b798bd2..d318c94 100644
--- a/html/sendMessage.js
+++ b/html/sendMessage.js
@@ -159,45 +159,110 @@ function onRemoveFavorite(event) {
         });
 }
 
-// Fires when the "Additional groups" multi-select changes. For each newly
-// selected id that isn't already a favorite we POST /user/groups/add. The
-// picker itself keeps the selection (so this send still uses the group);
-// the group starts appearing in the Favorite Groups picker on the next
-// page load, and immediately in the chip strip below.
-function onNewGroupsChange(newlySelectedIds) {
-    if (!newlySelectedIds || !newlySelectedIds.length) return;
+// Explicit "Save selection to favorites" action. Reads whatever is
+// currently selected in the "Additional groups" picker, POSTs
+// /user/groups/add for each id that isn't already a favorite, and on
+// success rewires the widget state so the newly-saved groups move from
+// the Additional picker into the Favorite picker without losing this
+// message's recipient list.
+//
+// Kept explicit (button-driven) rather than firing on every change so a
+// one-off pick — the common case, since every message tends to target a
+// different set of groups — doesn't pollute favorites forever.
+function saveSelectionToFavorites() {
     var newGroupsEl = document.getElementById('newGroups');
-    var pending = 0;
-    var successes = 0;
+    var favGroupsEl = document.getElementById('favGroups');
+    var btn = document.getElementById('saveFavoritesBtn');
+    if (!newGroupsEl) return;
 
-    newlySelectedIds.forEach(function (id) {
-        if (favoriteGroups.some(function (g) { return g.id === id; })) return;
-        pending++;
+    var selectedOptions = newGroupsEl.getSelectedOptions() || [];
+    var candidates = [];
+    for (var i = 0; i < selectedOptions.length; i++) {
+        var id = selectedOptions[i].value;
+        if (favoriteGroups.some(function (g) { return g.id === id; })) continue;
+        candidates.push({ id: id, name: selectedOptions[i].label || selectedOptions[i].text });
+    }
+    if (!candidates.length) {
+        flashFavoritesStatus('Nothing new to save.');
+        return;
+    }
+
+    if (btn) btn.disabled = true;
+    var latestFavorites = favoriteGroups;
+    var successIds = [];
+    var pending = candidates.length;
+
+    candidates.forEach(function (c) {
         fetch('/CollabCentral/' + CollabCentral.appName + '/user/groups/add', {
             method: 'POST',
             headers: { 'Content-Type': 'application/json' },
-            body: JSON.stringify({ id: id })
+            body: JSON.stringify({ id: c.id })
         })
             .then(function (res) {
                 if (!res.ok) throw new Error('HTTP ' + res.status);
                 return res.json();
             })
             .then(function (updatedFavorites) {
-                favoriteGroups = updatedFavorites || favoriteGroups;
-                successes++;
-                renderFavoritesManager();
+                if (Array.isArray(updatedFavorites)) latestFavorites = updatedFavorites;
+                successIds.push(c.id);
             })
             .catch(function (err) {
-                console.error('Failed to add favorite ' + id + ':', err);
+                console.error('Failed to add favorite ' + c.id + ':', err);
                 flashFavoritesStatus('Could not save one or more favorites.', true);
             })
             .finally(function () {
                 pending--;
-                if (pending === 0 && successes > 0) {
-                    flashFavoritesStatus(successes === 1
-                        ? 'Added to favorites.'
-                        : 'Added ' + successes + ' to favorites.');
+                if (pending > 0) return;
+
+                if (btn) btn.disabled = false;
+                if (!successIds.length) return;
+
+                // Capture the current favorite selection BEFORE
+                // rebuilding the options list — setOptions can clear
+                // the selection depending on the VirtualSelect
+                // internals, and we want this message's existing
+                // favorite picks to survive.
+                var currentFavIds = [];
+                if (favGroupsEl && typeof favGroupsEl.getSelectedOptions === 'function') {
+                    var favSel = favGroupsEl.getSelectedOptions() || [];
+                    for (var j = 0; j < favSel.length; j++) currentFavIds.push(favSel[j].value);
                 }
+
+                // Adopt the freshest server view of favorites, then
+                // rebuild the favorites VirtualSelect options list so
+                // the just-saved groups become pickable there.
+                favoriteGroups = latestFavorites;
+                renderFavoritesManager();
+                if (favGroupsEl && typeof favGroupsEl.setOptions === 'function') {
+                    favGroupsEl.setOptions(favoriteGroups.map(function (g) {
+                        return { label: g.name, value: g.id };
+                    }));
+                }
+
+                // Preserve this message's recipient set: move the
+                // saved ids from the Additional picker into the
+                // Favorite picker. Users can still deselect either
+                // way manually, but the default is "you saved these,
+                // they're still going to those groups".
+                if (favGroupsEl && typeof favGroupsEl.setValue === 'function') {
+                    for (var k = 0; k < successIds.length; k++) {
+                        if (currentFavIds.indexOf(successIds[k]) === -1) currentFavIds.push(successIds[k]);
+                    }
+                    favGroupsEl.setValue(currentFavIds);
+                }
+                if (typeof newGroupsEl.setValue === 'function') {
+                    var remaining = [];
+                    var addSel = newGroupsEl.getSelectedOptions() || [];
+                    for (var m = 0; m < addSel.length; m++) {
+                        var mid = addSel[m].value;
+                        if (successIds.indexOf(mid) === -1) remaining.push(mid);
+                    }
+                    newGroupsEl.setValue(remaining);
+                }
+
+                flashFavoritesStatus(successIds.length === 1
+                    ? 'Added to favorites.'
+                    : 'Added ' + successIds.length + ' to favorites.');
             });
     });
 }
@@ -226,20 +291,9 @@ function loadNewGroups(appName) {
                 el.add(option);
             }
             VirtualSelect.init({ ele: '#newGroups' });
-
-            // VirtualSelect emits a standard 'change' event on the original
-            // <select>. We diff against the previous selection so we only
-            // fire /user/groups/add for the newly-picked ids, not the whole
-            // set on every change.
-            var previous = [];
-            el.addEventListener('change', function () {
-                var current = [];
-                var selected = el.getSelectedOptions();
-                for (var j = 0; j < selected.length; j++) current.push(selected[j].value);
-                var added = current.filter(function (id) { return previous.indexOf(id) === -1; });
-                previous = current;
-                if (added.length) onNewGroupsChange(added);
-            });
+            // Additional groups are per-message only — no auto-save on
+            // change. Users promote picks to favorites via the explicit
+            // "Save selection to favorites" button (saveSelectionToFavorites).
         });
 }