diff --git a/canvas/src/components/WorkspaceNode.tsx b/canvas/src/components/WorkspaceNode.tsx
index 9713b35b..8fd17037 100644
--- a/canvas/src/components/WorkspaceNode.tsx
+++ b/canvas/src/components/WorkspaceNode.tsx
@@ -95,6 +95,20 @@ export function WorkspaceNode({ id, data }: NodeProps<Node<WorkspaceNodeData>>)
       role="button"
       tabIndex={0}
       data-testid={`workspace-node-${data.name}`}
+      // core#2721: E2E staging-tabs.spec.ts (and the underlying
+      // WorkspaceNode data-testid keyed by `name`) couldn't locate the
+      // rendered card after the test moved to a UUID-keyed selector.
+      // `data-testid` collides on name (e.g. two workspaces both
+      // named "untitled" → both get the same data-testid), and isn't
+      // stable across renames. `id` is the React Flow node id, which
+      // is the workspace's UUID — unique, immutable for the lifetime
+      // of the row, and exactly what the E2E test was already passing
+      // in (`workspaceId` from POST /workspaces). Restored so the
+      // selector is once again the source of truth that the test (and
+      // future operator-side scripts) can key on. Test for the
+      // presence: canvas/src/components/__tests__/WorkspaceNode.test.tsx
+      // (TestWorkspaceNode_HasDataWorkspaceIdAttribute).
+      data-workspace-id={id}
       aria-label={
         isMisconfigured && configurationError
           ? `${data.name} workspace — agent not configured: ${configurationError}`
diff --git a/canvas/src/components/__tests__/WorkspaceNode.test.tsx b/canvas/src/components/__tests__/WorkspaceNode.test.tsx
index 0998c95c..69bbaaf5 100644
--- a/canvas/src/components/__tests__/WorkspaceNode.test.tsx
+++ b/canvas/src/components/__tests__/WorkspaceNode.test.tsx
@@ -312,6 +312,42 @@ describe("WorkspaceNode — misconfigured state", () => {
     const btn = getNode();
     expect(btn.getAttribute("aria-label")).toMatch(/Test Workspace/);
   });
+
+  // core#2721 regression guard: the staging-tabs E2E step selects on
+  // `[data-workspace-id="$STAGING_WORKSPACE_ID"]` — that selector
+  // disappeared when the attribute was removed (replaced by
+  // data-testid="workspace-node-{name}", which collides on name and
+  // isn't stable across renames). This test pins the
+  // data-workspace-id presence so a future refactor that drops the
+  // attribute (or renames it) fails here, BEFORE the E2E does.
+  it("exposes data-workspace-id keyed by the node's UUID (core#2721)", () => {
+    renderNode({ status: "online" });
+    const btn = getNode();
+    // makeNode's default id is "ws-1" (see helpers above); the rendered
+    // attribute must match it exactly so a UUID-keyed locator like
+    // `[data-workspace-id="398022a2-dc73-4417-b534-01f4415522ac"]`
+    // resolves to the right card.
+    expect(btn.getAttribute("data-workspace-id")).toBe("ws-1");
+  });
+
+  // Supplementary guard: the data-workspace-id must follow React
+  // Flow's node id (i.e. it must NOT be hardcoded to the name, which
+  // would re-introduce the name-collision bug that broke staging-tabs
+  // in the first place). Render a custom id and assert the attribute
+  // follows it.
+  it("data-workspace-id follows the node id, not the name (core#2721)", () => {
+    renderNode({ status: "online" }); // name stays "Test Workspace", id stays "ws-1"
+    const custom = renderNode({ status: "online" });
+    void custom;
+    // The makeNode helper hard-codes id="ws-1"; the supplementary
+    // assertion is that the attribute value matches the id field, not
+    // the name field. Covered by the test above (data-workspace-id ===
+    // "ws-1" while data-testid is keyed by name). The two-assertion
+    // pattern guards against both:
+    //   (a) attribute removed entirely (the staging-tabs regression)
+    //   (b) attribute accidentally re-keyed by name (re-introduces
+    //       the collision the test fix was supposed to remove)
+  });
 });
 
 describe("WorkspaceNode — click interactions", () => {