diff --git a/main.cpp b/main.cpp
index 23e1c46..7de09a1 100644
--- a/main.cpp
+++ b/main.cpp
@@ -216,11 +216,13 @@ static bool load_input() {
     g_app.types_dirty = false;
     g_app.types_save_error.clear();
 
-    // Restablecer viewport state (preserva camara user-visible)
+    // Restablecer viewport state (preserva camara user-visible). Physics
+    // arrancan en pausa para que las posiciones guardadas no se pierdan;
+    // el usuario las activa con el boton Physics de la toolbar.
     g_viewport.selection.clear();
     g_viewport.hovered_node = -1;
     g_viewport.selected_node = -1;
-    g_viewport.layout_running = true;
+    g_viewport.layout_running = false;
     g_viewport.layout_energy  = 0.0f;
 
     // Posicionar nodos: si todos tienen (x,y)=0, aplicar layout circular como
diff --git a/views.cpp b/views.cpp
index d45f204..d0fb5a7 100644
--- a/views.cpp
+++ b/views.cpp
@@ -458,14 +458,46 @@ void views_toolbar(AppState& app) {
         }
         toolbar_separator();
 
-        ImGui::TextUnformatted("Layout:");
+        // Layout: <name> ▾ — dropdown con todos los layouts + acciones.
+        {
+            char btn[96];
+            std::snprintf(btn, sizeof(btn), TI_LAYOUT_GRID " Layout: %s",
+                           k_layout_names[app.layout_mode % k_layout_count]);
+            if (button(btn, ButtonVariant::Secondary)) {
+                ImGui::OpenPopup("##layout_menu");
+            }
+            if (ImGui::BeginPopup("##layout_menu")) {
+                ImGui::TextDisabled("Apply layout");
+                ImGui::Separator();
+                for (int i = 0; i < k_layout_count; ++i) {
+                    bool is_cur = (i == app.layout_mode);
+                    if (ImGui::MenuItem(k_layout_names[i], nullptr, is_cur)) {
+                        app.layout_mode = i;
+                        ++app.apply_layout_tick;
+                    }
+                }
+                ImGui::Separator();
+                if (ImGui::MenuItem(TI_LAYOUT_GRID " Reset positions (unpin + restart)")) {
+                    app.want_unpin_all = true;
+                    ++app.apply_layout_tick;
+                }
+                if (ImGui::MenuItem(TI_DEVICE_FLOPPY " Save current layout")) {
+                    app.want_save_layout = true;
+                }
+                ImGui::EndPopup();
+            }
+        }
         ImGui::SameLine();
-        ImGui::SetNextItemWidth(140);
-        int idx = app.layout_mode;
-        if (ImGui::Combo("##layout", &idx, k_layout_names, k_layout_count)) {
-            if (idx != app.layout_mode) {
-                app.layout_mode = idx;
-                ++app.apply_layout_tick;
+
+        // Physics ▶ / ⏸ — toggle visible. Solo afecta a layout 'force'.
+        if (app.viewport) {
+            const bool running = app.viewport->layout_running;
+            const char* lbl = running ? TI_PLAYER_PAUSE " Physics: ON"
+                                       : TI_PLAYER_PLAY  " Physics: OFF";
+            ButtonVariant var = running ? ButtonVariant::Primary
+                                          : ButtonVariant::Subtle;
+            if (button(lbl, var)) {
+                app.viewport->layout_running = !running;
             }
         }
         toolbar_separator();
@@ -476,25 +508,14 @@ void views_toolbar(AppState& app) {
         if (button(TI_ARROWS_MAXIMIZE " Fit view", ButtonVariant::Subtle)) {
             app.want_fit = true;
         }
-        if (button(TI_DEVICE_FLOPPY " Save layout", ButtonVariant::Subtle)) {
-            app.want_save_layout = true;
-        }
         if (button(TI_REFRESH " Reload", ButtonVariant::Subtle)) {
             app.want_reload = true;
         }
-        if (button(TI_LAYOUT_GRID " Reset layout", ButtonVariant::Subtle)) {
-            app.want_unpin_all = true;
-            ++app.apply_layout_tick;
-        }
         toolbar_separator();
 
         ImGui::Checkbox("GPU layout", &app.use_gpu);
         ImGui::SameLine();
         ImGui::Checkbox("Labels", &app.labels_enabled);
-        if (app.viewport) {
-            ImGui::SameLine();
-            ImGui::Checkbox("Run layout", &app.viewport->layout_running);
-        }
     toolbar_end();
 }
 
diff --git a/views.h b/views.h
index 41c2663..62d4024 100644
--- a/views.h
+++ b/views.h
@@ -24,7 +24,10 @@ struct AppState {
 
     // Layout activo — default grid (1) para que los grafos cargados de
     // operations.db se distribuyan ordenadamente al abrir.
-    int                  layout_mode = 1;           // 0=force, 1=grid, 2=circular, 3=radial, 4=hierarchical, 5=fixed
+    // Default: fixed (5) — respeta posiciones guardadas y physics off por
+    // defecto. El usuario activa fisicas con el boton Physics y/o cambia
+    // layout desde el dropdown Layout en la toolbar.
+    int                  layout_mode = 5;           // 0=force, 1=grid, 2=circular, 3=radial, 4=hierarchical, 5=fixed
     int                  apply_layout_tick = 0;     // se incrementa cuando hay que reaplicar layout
     bool                 want_unpin_all  = false;   // Reset layout: limpia NF_PINNED y reaplica