frontend/packages/dashboard/src/dashboard.css

@@ -2520,4 +2520,6 @@ body.dashboard-shell.has-selection { padding-bottom: 4.5em; }
   opacity: 0.5;
   cursor: default;
 }
-
+.move-picker .btn-move {
+  margin-left: 0;
+}

frontend/packages/dashboard/src/tabs.js

@@ -933,49 +933,80 @@ window.marked = marked;
       disabledTitle: why('PURG3', managerNames.map((n) => `\`${n}\` is the manager`)),
     });
 
-    // Move agent(s) in the topology tree — selecting an option in the
+    // Move agent(s) in the topology tree — see
-    // M0V3 dropdown immediately confirms + executes the move. "(no parent)"
+    // docs/web-ui.md::Selection bar for the two affordances:
-    // promotes to root (empty new_parent on the backend). Cycle-safe:
-    // dropdown filters out self and descendants on the client side; the
-    // backend rechecks via `topology::set_parent`.
     //
-    // Backend: POST /api/topology/set-parent (dashboard.rs),
+    //   ⇡ M0V3 → ROOT   promote selected agent(s) to top-level (parent=null)
-    // form-encoded `child=<name>&new_parent=<target-or-empty>`. Re-emits
+    //   ⇢ M0V3 → [sel]  reparent the single selected agent under a picked
-    // container snapshots on success so the tree repaints without a
+    //                   parent (cycle-safe — the dropdown filters out self
-    // separate refresh.
+    //                   and own descendants on the client side; the
+    //                   backend rechecks via `topology::set_parent`).
+    //
+    // Backend lives at POST /api/topology/set-parent (dashboard.rs),
+    // form-encoded `child=<name>&new_parent=<target-or-empty>`. The
+    // backend re-emits container snapshots on success, so the tree
+    // repaints without a separate refresh.
     addMoveActions(actions, selected, containers);
   }
 
-  // Render the M0V3 picker in the selection bar. Selecting any real option
+  // Render the M0V3 affordances inside the selection bar — separate
-  // (including "(no parent)") immediately fires a confirm + POST — no
+  // helper because the picker variant needs a select + button pair,
-  // separate button. Backend `topology::set_parent` refuses invalid moves
+  // not the single-button shape addBulkButton ships. Backend
-  // and the refusal surfaces in the alert roll-up.
+  // `topology::set_parent` refuses moves it can't satisfy (manager
+  // included) and the refusal surfaces in the bulk-action error
+  // roll-up.
   function addMoveActions(parent, selected, containers) {
+    // M0V3 → ROOT: parent=null for every selected agent. Only meaningful
+    // when at least one selected agent currently has a non-null parent;
+    // otherwise it's a no-op for everything.
+    const someNotAtRoot = selected.some((c) => c.parent);
+    addBulkButton(parent, 'btn-move', '⇡ M0V3 → ROOT', someNotAtRoot, selected, {
+      action: '/api/topology/set-parent',
+      perAgentBodyFor: (name) => ({ child: name, new_parent: '' }),
+      confirm: (names) => `promote ${names.length} agent${names.length === 1 ? '' : 's'} (${names.join(', ')}) to top-level (parent → root)?`,
+      disabledTitle: !someNotAtRoot
+        ? '⇡ M0V3 → ROOT not available — all selected agents are already at root'
+        : null,
+    });
+
+    // M0V3 → <pick>: inline `<select>` of candidate parents + submit
+    // button. Available for any selection size. Picker omits each
+    // selected agent itself plus the union of every selected agent's
+    // descendants (cycle-safe; backend `topology::set_parent`
+    // re-checks). Empty candidate list ⇒ disable the picker.
     const candidates = validReparentCandidates(selected, containers);
     const wrap = el('span', { class: 'move-picker' });
     const selectTitle = selected.length === 1
       ? `change ${selected[0].name}'s parent`
       : `change ${selected.length} agents' parent`;
     const sel = el('select', { class: 'move-picker-select', title: selectTitle });
-    sel.append(el('option', { value: '' }, '⇢ M0V3 →'));
+    sel.append(el('option', { value: '' }, '— pick parent —'));
-    // "(no parent)" → empty new_parent on the backend (promotes to root).
-    sel.append(el('option', { value: '__root__' }, '(no parent)'));
     for (const name of candidates) {
       sel.append(el('option', { value: name }, name));
     }
-    sel.addEventListener('change', async () => {
+    if (!candidates.length) {
-      if (sel.selectedIndex === 0) return;
+      sel.disabled = true;
-      const newParent = sel.value === '__root__' ? '' : sel.value;
+      sel.title = selected.length === 1
-      const newParentLabel = sel.value === '__root__' ? '(no parent)' : sel.value;
+        ? `no valid parents for ${selected[0].name} (every other agent is its descendant)`
+        : `no valid parents — every other agent is a descendant of one of the selected`;
+    }
+    const btn = el('button', { type: 'button', class: 'btn btn-move' }, '⇢ M0V3');
+    btn.disabled = true;
+    sel.addEventListener('change', () => { btn.disabled = !sel.value; });
+    btn.addEventListener('click', async () => {
+      const newParent = sel.value;
+      if (!newParent) return;
       const names = selected.map((c) => c.name);
       const promptMsg = names.length === 1
-        ? `move ${names[0]} → ${newParentLabel}?`
+        ? `move ${names[0]} under ${newParent}?`
-        : `move ${names.length} agents (${names.join(', ')}) → ${newParentLabel}?`;
+        : `move ${names.length} agents (${names.join(', ')}) under ${newParent}?`;
-      if (!confirm(promptMsg)) {
+      if (!confirm(promptMsg)) return;
-        sel.selectedIndex = 0;
+      btn.disabled = true;
-        return;
+      const original = btn.innerHTML;
-      }
+      btn.innerHTML = '<span class="spinner">◐</span> ⇢ M0V3';
-      sel.disabled = true;
+      // Sequential POSTs — same shape as the bulk-button loop. Each
+      // call is small + backend serialises topology writes via the
+      // file-lock anyway.
       const failures = [];
       for (const name of names) {
         try {
@@ -996,13 +1027,13 @@ window.marked = marked;
           failures.push(`${name}: ${err}`);
         }
       }
-      sel.disabled = false;
+      btn.innerHTML = original;
-      sel.selectedIndex = 0;
+      btn.disabled = !sel.value;
       if (failures.length) {
-        alert(`M0V3 completed with ${failures.length} failure${failures.length === 1 ? '' : 's'}:\n\n` + failures.join('\n'));
+        alert(`⇢ M0V3 completed with ${failures.length} failure${failures.length === 1 ? '' : 's'}:\n\n` + failures.join('\n'));
       }
     });
-    wrap.append(sel);
+    wrap.append(sel, btn);
     parent.append(wrap);
   }