diff --git a/canvas/src/components/canvas/__tests__/A2AEdge.test.tsx b/canvas/src/components/canvas/__tests__/A2AEdge.test.tsx
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+++ b/canvas/src/components/canvas/__tests__/A2AEdge.test.tsx
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+// @vitest-environment jsdom
+/**
+ * Tests for A2AEdge — the custom React Flow edge that renders the
+ * delegation count between two workspaces and routes a click into the
+ * source workspace's Activity feed.
+ *
+ * Behavioural coverage for the four contracts the component owns:
+ *   1. No label → render only the BaseEdge SVG, NO portaled HTML pill
+ *      (renders nothing visible at the label layer)
+ *   2. Click the pill → selectNode(source) AND setPanelTab("activity")
+ *      when this is a *fresh* selection
+ *   3. Click the pill on an already-selected source → selectNode(source)
+ *      runs but setPanelTab is NOT called (preserves the user's current
+ *      tab so they don't get yanked off Chat / Memory)
+ *   4. isHot toggles the violet vs. blue accent classes — locks the
+ *      buildA2AEdges output → A2AEdge styling contract
+ *   5. ARIA label pluralizes correctly (1 delegation vs N delegations)
+ *
+ * Issue: #2071 (Canvas test gaps follow-up).
+ */
+import {
+  describe,
+  it,
+  expect,
+  vi,
+  beforeEach,
+  afterEach,
+  type Mock,
+} from "vitest";
+import {
+  render,
+  screen,
+  cleanup,
+  fireEvent,
+} from "@testing-library/react";
+
+// ── Hoisted mocks ────────────────────────────────────────────────────────────
+
+// @xyflow/react is mocked end-to-end so the test doesn't need a
+// ReactFlow provider / Pane / canvas. EdgeLabelRenderer normally
+// portals into the canvas root; here it just renders children inline
+// so screen.queryByRole picks up the pill.
+vi.mock("@xyflow/react", () => ({
+  BaseEdge: ({ id }: { id: string }) => <g data-testid={`base-edge-${id}`} />,
+  EdgeLabelRenderer: ({ children }: { children: React.ReactNode }) => (
+    <>{children}</>
+  ),
+  getBezierPath: () => ["M0,0 L1,1", 50, 50],
+}));
+
+// Canvas store mock — simulates selectNode + setPanelTab + the
+// selectedNodeId state the click handler reads via getState().
+const { mockSelectNode, mockSetPanelTab, mockState } = vi.hoisted(() => ({
+  mockSelectNode: vi.fn(),
+  mockSetPanelTab: vi.fn(),
+  mockState: {
+    selectedNodeId: null as string | null,
+    selectNode: vi.fn(),
+    setPanelTab: vi.fn(),
+  },
+}));
+
+// Wire the hoisted mock fns onto the store-state object (vi.hoisted
+// returns referentially-stable objects, so this assignment after
+// hoisting is observed by every consumer).
+mockState.selectNode = mockSelectNode;
+mockState.setPanelTab = mockSetPanelTab;
+
+vi.mock("@/store/canvas", () => ({
+  useCanvasStore: Object.assign(
+    (selector: (s: typeof mockState) => unknown) => selector(mockState),
+    { getState: () => mockState },
+  ),
+}));
+
+// Import the SUT after the mocks are declared.
+import { A2AEdge } from "../A2AEdge";
+
+// ── Helpers ──────────────────────────────────────────────────────────────────
+
+function defaultEdgeProps(over: Record<string, unknown> = {}) {
+  return {
+    id: "edge-1",
+    source: "ws-source",
+    target: "ws-target",
+    sourceX: 0,
+    sourceY: 0,
+    targetX: 100,
+    targetY: 100,
+    sourcePosition: "right",
+    targetPosition: "left",
+    style: {},
+    ...over,
+  } as never; // EdgeProps is a discriminated union; cast simplifies the test fixture
+}
+
+beforeEach(() => {
+  mockSelectNode.mockReset();
+  mockSetPanelTab.mockReset();
+  mockState.selectedNodeId = null;
+});
+
+afterEach(() => {
+  cleanup();
+});
+
+// ── Tests ────────────────────────────────────────────────────────────────────
+
+describe("A2AEdge — render", () => {
+  it("renders the BaseEdge but no pill when data.label is empty", () => {
+    render(
+      <A2AEdge
+        {...defaultEdgeProps({
+          data: { count: 0, lastAt: 0, isHot: false, label: "" },
+        })}
+      />,
+    );
+    expect(screen.getByTestId("base-edge-edge-1")).toBeTruthy();
+    // No clickable pill rendered.
+    expect(screen.queryByRole("button")).toBeNull();
+  });
+
+  it("renders the pill with the label text when data.label is present", () => {
+    render(
+      <A2AEdge
+        {...defaultEdgeProps({
+          data: {
+            count: 5,
+            lastAt: 0,
+            isHot: false,
+            label: "5 calls · 2m ago",
+          },
+        })}
+      />,
+    );
+    const btn = screen.getByRole("button");
+    expect(btn.textContent).toBe("5 calls · 2m ago");
+  });
+
+  it("applies the violet accent classes when isHot is true", () => {
+    render(
+      <A2AEdge
+        {...defaultEdgeProps({
+          data: { count: 12, lastAt: 0, isHot: true, label: "12 calls · 1m ago" },
+        })}
+      />,
+    );
+    const btn = screen.getByRole("button");
+    expect(btn.className).toContain("border-violet-500/60");
+    expect(btn.className).toContain("text-violet-200");
+    // Negative: blue accent must NOT appear when hot
+    expect(btn.className).not.toContain("border-blue-500/60");
+  });
+
+  it("applies the blue accent classes when isHot is false", () => {
+    render(
+      <A2AEdge
+        {...defaultEdgeProps({
+          data: { count: 2, lastAt: 0, isHot: false, label: "2 calls · 8m ago" },
+        })}
+      />,
+    );
+    const btn = screen.getByRole("button");
+    expect(btn.className).toContain("border-blue-500/60");
+    expect(btn.className).toContain("text-blue-200");
+  });
+
+  it("ARIA label pluralizes (singular)", () => {
+    render(
+      <A2AEdge
+        {...defaultEdgeProps({
+          data: { count: 1, lastAt: 0, isHot: false, label: "1 call · 30s ago" },
+        })}
+      />,
+    );
+    const btn = screen.getByRole("button");
+    // count=1 → "1 delegation from <when>." (no trailing s)
+    expect(btn.getAttribute("aria-label")).toMatch(/^1 delegation from/);
+    expect(btn.getAttribute("aria-label")).not.toMatch(/^1 delegations/);
+  });
+
+  it("ARIA label pluralizes (plural)", () => {
+    render(
+      <A2AEdge
+        {...defaultEdgeProps({
+          data: { count: 7, lastAt: 0, isHot: false, label: "7 calls · 1m ago" },
+        })}
+      />,
+    );
+    const btn = screen.getByRole("button");
+    expect(btn.getAttribute("aria-label")).toMatch(/^7 delegations from/);
+  });
+});
+
+describe("A2AEdge — click behaviour", () => {
+  it("click on the pill selects the source workspace", () => {
+    render(
+      <A2AEdge
+        {...defaultEdgeProps({
+          source: "ws-alpha",
+          data: { count: 4, lastAt: 0, isHot: false, label: "4 calls · 1m ago" },
+        })}
+      />,
+    );
+    fireEvent.click(screen.getByRole("button"));
+    expect(mockSelectNode).toHaveBeenCalledWith("ws-alpha");
+  });
+
+  it("on FRESH selection, also switches the panel tab to Activity", () => {
+    // Pre-state: nothing selected. The click should yank the user
+    // into Activity to expose the discovery affordance.
+    mockState.selectedNodeId = null;
+    render(
+      <A2AEdge
+        {...defaultEdgeProps({
+          source: "ws-alpha",
+          data: { count: 4, lastAt: 0, isHot: false, label: "4 calls" },
+        })}
+      />,
+    );
+    fireEvent.click(screen.getByRole("button"));
+    expect(mockSetPanelTab).toHaveBeenCalledWith("activity");
+  });
+
+  it("on RE-CLICK of an already-selected source, does NOT switch the tab", () => {
+    // Pre-state: source is already selected; user may have intentionally
+    // switched to Chat / Memory. Re-clicking the edge must NOT yank them
+    // back to Activity. (Selector-store getState() returns mockState.)
+    mockState.selectedNodeId = "ws-alpha";
+    render(
+      <A2AEdge
+        {...defaultEdgeProps({
+          source: "ws-alpha",
+          data: { count: 4, lastAt: 0, isHot: false, label: "4 calls" },
+        })}
+      />,
+    );
+    fireEvent.click(screen.getByRole("button"));
+    // selectNode still fires (cheap, idempotent on the same id).
+    expect(mockSelectNode).toHaveBeenCalledWith("ws-alpha");
+    // setPanelTab MUST NOT — that's the regression-locked guarantee.
+    expect(mockSetPanelTab).not.toHaveBeenCalled();
+  });
+
+  it("click stops propagation so the canvas pane doesn't deselect", () => {
+    // Without stopPropagation, clicking the edge label would bubble
+    // to the canvas Pane and (per existing handlers) clear the
+    // selection — exactly the opposite of what the click is meant to do.
+    const paneClick = vi.fn();
+    render(
+      <div onClick={paneClick}>
+        <A2AEdge
+          {...defaultEdgeProps({
+            source: "ws-alpha",
+            data: { count: 4, lastAt: 0, isHot: false, label: "4 calls" },
+          })}
+        />
+      </div>,
+    );
+    fireEvent.click(screen.getByRole("button"));
+    expect(paneClick).not.toHaveBeenCalled();
+    expect(mockSelectNode).toHaveBeenCalledWith("ws-alpha");
+  });
+});