diff --git a/src/app/layouts/tasks-executor/tasks-executor.css b/src/app/layouts/tasks-executor/tasks-executor.css
index 3d0995e..301f544 100644
--- a/src/app/layouts/tasks-executor/tasks-executor.css
+++ b/src/app/layouts/tasks-executor/tasks-executor.css
@@ -40,8 +40,11 @@
  */
 .tasks-executor-tree-panel-floating {
   position: fixed;
-  top: 12px;
+  /* Anchored to the bottom: the top-left corner is where the run's own title and toolbar sit. */
+  bottom: 12px;
   left: 12px;
+  /* Growing upward from the toggle keeps that toggle in the same place as the tree gets longer. */
+  justify-content: flex-end;
   z-index: calc(var(--z-modal) + 1);
   width: 280px;
   max-height: calc(100vh - 24px);
diff --git a/src/app/layouts/tasks-executor/tasks-executor.html b/src/app/layouts/tasks-executor/tasks-executor.html
index f550c56..fdf071a 100644
--- a/src/app/layouts/tasks-executor/tasks-executor.html
+++ b/src/app/layouts/tasks-executor/tasks-executor.html
@@ -11,23 +11,21 @@
       </app-tasks-executions-list>
 
       @if (selectedExecution(); as run) {
+      @if (executionTreeAvailable()) {
+      <!-- Only rendered for a run that has a subtree, so nothing inside needs to handle its absence. -->
       <section class="tasks-executor-tree-panel"
-        [class.tasks-executor-tree-panel-collapsed]="!executionTreeAvailable() || !executionTreeOpen()"
+        [class.tasks-executor-tree-panel-collapsed]="!executionTreeOpen()"
         [class.tasks-executor-tree-panel-floating]="treeFloating()">
         <button
           type="button"
           class="tasks-executor-tree-toggle"
-          [disabled]="!executionTreeAvailable()"
-          [attr.aria-expanded]="executionTreeAvailable() && executionTreeOpen()"
-          [matTooltip]="executionTreeAvailable() ? '' : 'This run has no container steps, so there is no subtree to show.'"
+          [attr.aria-expanded]="executionTreeOpen()"
           (click)="toggleExecutionTree()">
           <span>Execution tree</span>
-          @if (executionTreeAvailable()) {
           <span class="tasks-executor-tree-toggle-icon" [class.tasks-executor-tree-toggle-icon-open]="executionTreeOpen()">⌃</span>
-          }
         </button>
 
-        @if (executionTreeAvailable() && executionTreeOpen()) {
+        @if (executionTreeOpen()) {
         <app-execution-tree
           class="tasks-executor-rail-tree"
           [rootExecution]="run"
@@ -37,6 +35,7 @@
         }
       </section>
       }
+      }
     </div>
 
     <mat-card class="tasks-executor-viewer flex w-full flex-col overflow-hidden !rounded-md !bg-gray-100">
diff --git a/src/app/layouts/tasks-executor/tasks-executor.spec.ts b/src/app/layouts/tasks-executor/tasks-executor.spec.ts
index b92fa67..6f248a2 100644
--- a/src/app/layouts/tasks-executor/tasks-executor.spec.ts
+++ b/src/app/layouts/tasks-executor/tasks-executor.spec.ts
@@ -69,7 +69,8 @@ describe('TasksExecutor', () => {
             init: vi.fn(),
             retrieveExecution: vi.fn().mockReturnValue(of(null)),
             deleteExecution: vi.fn().mockReturnValue(of(null)),
-            rerunExecution: vi.fn().mockReturnValue(of(null))
+            rerunExecution: vi.fn().mockReturnValue(of(null)),
+            retrieveExecutionEvents: vi.fn().mockReturnValue(of([]))
           }
         },
         {
@@ -81,13 +82,15 @@ describe('TasksExecutor', () => {
         {
           provide: BlocksService,
           useValue: {
-            getAllBlocksTypes: vi.fn().mockResolvedValue(signal([]))
+            getAllBlocksTypes: vi.fn().mockResolvedValue(signal([])),
+            hasLoadedBlockTypes: vi.fn().mockReturnValue(false)
           }
         },
         {
           provide: ContainersService,
           useValue: {
-            getAllContainerTypes: vi.fn().mockResolvedValue(signal([]))
+            getAllContainerTypes: vi.fn().mockResolvedValue(signal([])),
+            peekContainerType: vi.fn().mockReturnValue(null)
           }
         },
         {
@@ -182,8 +185,10 @@ describe('TasksExecutor', () => {
         }
       }
     } as any]);
+    fixture.detectChanges();
     expect(component.executionTreeAvailable()).toBe(true);
     expect(component.treeFloating()).toBe(false);
+    expect(fixture.nativeElement.querySelector('.tasks-executor-tree-panel')).not.toBeNull();
 
     component.viewerFullscreen.set(true);
     expect(component.treeFloating()).toBe(true);
@@ -206,9 +211,12 @@ describe('TasksExecutor', () => {
       }
     } as any]);
     component.viewerFullscreen.set(true);
+    fixture.detectChanges();
 
     expect(component.executionTreeAvailable()).toBe(false);
     expect(component.treeFloating()).toBe(false);
+    // Not merely un-floated: a run with no subflow has no tree to offer, so the panel is absent.
+    expect(fixture.nativeElement.querySelector('.tasks-executor-tree-panel')).toBeNull();
   });
 
   it('follows only container steps waiting for a child subflow', () => {