diff --git a/src/components/ContractEventFeed.test.tsx b/src/components/ContractEventFeed.test.tsx
index 1cae9e3..3a15959 100644
--- a/src/components/ContractEventFeed.test.tsx
+++ b/src/components/ContractEventFeed.test.tsx
@@ -664,4 +664,77 @@ describe("ContractEventFeed", () => {
       );
     });
   });
+
+  // ── Polling stale-closure regression (#582) ──────────────────────────────
+  // The polling interval used to close over the `load` instance captured when
+  // the effect first ran, so changing the `contractId` prop kept polling the
+  // OLD contract. These tests pin the fixed behaviour: the interval restarts
+  // with the current contractId.
+  describe("polling contractId switching (#582)", () => {
+    const NEW_ID =
+      "CBBB4TCR3TY5OJHCTJC2A4QSY6CJWJH5IAJTGKIN2ER7LBNVKOCCWNA";
+
+    it("restarts polling for the new contractId after the prop changes", async () => {
+      const getEvents = vi.fn().mockResolvedValue({ data: [], error: null });
+      vi.mocked(getClient).mockReturnValue({
+        soroban: { getEvents },
+      } as unknown as SorokitClient);
+
+      const { rerender } = render(
+        <ContractEventFeed contractId={CONTRACT_ID} pollInterval={500} />,
+      );
+      act(() => { vi.advanceTimersByTime(0); });
+      await waitFor(() => expect(getEvents).toHaveBeenCalledTimes(1));
+      expect(getEvents).toHaveBeenLastCalledWith(CONTRACT_ID, 10, undefined);
+
+      rerender(<ContractEventFeed contractId={NEW_ID} pollInterval={500} />);
+      act(() => { vi.advanceTimersByTime(0); });
+
+      // The restarted effect loads the new contract immediately, then keeps
+      // polling it. Capture the call count here so the stale-closure check
+      // only examines calls made *after* the switch.
+      await waitFor(() => {
+        expect(getEvents).toHaveBeenLastCalledWith(NEW_ID, 10, undefined);
+      });
+      const callsAfterSwitch = getEvents.mock.calls.length;
+
+      // Advance past one full poll interval. The stale-closure bug (#582)
+      // would keep calling with the OLD contractId here; the fixed code must
+      // use NEW_ID for every poll after the switch.
+      act(() => { vi.advanceTimersByTime(500); });
+      await waitFor(() => {
+        expect(getEvents.mock.calls.length).toBeGreaterThan(callsAfterSwitch);
+      });
+
+      const postSwitchIds = getEvents.mock.calls
+        .slice(callsAfterSwitch)
+        .map(([id]) => id);
+      expect(postSwitchIds).not.toContain(CONTRACT_ID);
+      expect(postSwitchIds.every((id) => id === NEW_ID)).toBe(true);
+    });
+
+    it("resumes polling for the current contract when Live is toggled back on", async () => {
+      const getEvents = vi.fn().mockResolvedValue({ data: [], error: null });
+      vi.mocked(getClient).mockReturnValue({
+        soroban: { getEvents },
+      } as unknown as SorokitClient);
+
+      render(<ContractEventFeed contractId={CONTRACT_ID} pollInterval={500} />);
+      act(() => { vi.advanceTimersByTime(0); });
+      await waitFor(() => expect(getEvents).toHaveBeenCalledTimes(1));
+
+      fireEvent.click(screen.getByRole("button", { name: /live/i }));
+      const pausedCount = getEvents.mock.calls.length;
+      act(() => { vi.advanceTimersByTime(1500); });
+      expect(getEvents).toHaveBeenCalledTimes(pausedCount);
+
+      fireEvent.click(screen.getByRole("button", { name: /paused/i }));
+      act(() => { vi.advanceTimersByTime(500); });
+
+      await waitFor(() => {
+        expect(getEvents).toHaveBeenCalledTimes(pausedCount + 1);
+      });
+      expect(getEvents).toHaveBeenLastCalledWith(CONTRACT_ID, 10, undefined);
+    });
+  });
 });
diff --git a/src/components/SorobanPanel.test.tsx b/src/components/SorobanPanel.test.tsx
index 4bb677a..8f0a9be 100644
--- a/src/components/SorobanPanel.test.tsx
+++ b/src/components/SorobanPanel.test.tsx
@@ -12,6 +12,12 @@ vi.mock("@/context/useSorokit", () => ({
   useSorokit: vi.fn(() => ({
     isConnected: true,
     address: "GAAZI4TCR3TY5OJHCTJC2A4QSY6CJWJH5IAJTGKIN2ER7LBNVKOCCWNA",
+    client: {
+      soroban: {
+        invokeContract: mockInvokeContract,
+        simulateContract: mockSimulateContract,
+      },
+    },
   })),
 }));
 
@@ -30,6 +36,12 @@ describe("SorobanPanel", () => {
     vi.mocked(useSorokit).mockReturnValue({
       isConnected: true,
       address: "GAAZI4TCR3TY5OJHCTJC2A4QSY6CJWJH5IAJTGKIN2ER7LBNVKOCCWNA",
+      client: {
+        soroban: {
+          invokeContract: mockInvokeContract,
+          simulateContract: mockSimulateContract,
+        },
+      },
     } as unknown as ReturnType<typeof useSorokit>);
   });
 
@@ -39,6 +51,32 @@ describe("SorobanPanel", () => {
       expect(screen.getByRole("button", { name: /invoke/i })).toBeDisabled();
     });
 
+    // Issue #581 — the Invoke button must submit the parent form natively
+    // (type="submit") instead of re-dispatching the FormEvent handler through
+    // an unsafe `as unknown as React.MouseEventHandler` onClick cast.
+    it("submits the form natively via type=submit linked to the form's id", async () => {
+      mockInvokeContract.mockResolvedValueOnce({
+        data: { success: true },
+        error: null,
+      });
+      render(<SorobanPanel contractId="C123" onContractIdChange={() => {}} />);
+      fireEvent.change(screen.getByLabelText("Method"), {
+        target: { value: "balance" },
+      });
+
+      const invokeButton = screen.getByRole("button", { name: /invoke/i });
+      const form = document.querySelector("form");
+      expect(invokeButton).toHaveAttribute("type", "submit");
+      expect(form).not.toBeNull();
+      expect(invokeButton).toHaveAttribute("form", form!.id);
+
+      // Clicking the button reaches the form's onSubmit handler and produces
+      // a real invocation — not "Not implemented".
+      fireEvent.click(invokeButton);
+      await screen.findByText("Result");
+      expect(mockInvokeContract).toHaveBeenCalledOnce();
+    });
+
     it("should show error when invalid JSON args are provided", async () => {
       let currentContractId = "";
       const setContractId = (id: string) => { currentContractId = id; };
diff --git a/src/components/TransactionPanel.test.tsx b/src/components/TransactionPanel.test.tsx
index d2a3066..c5fb13f 100644
--- a/src/components/TransactionPanel.test.tsx
+++ b/src/components/TransactionPanel.test.tsx
@@ -72,6 +72,20 @@ describe("TransactionPanel", () => {
     expect(dialog).toHaveTextContent("GBRPYHIL...ONXHPA");
   });
 
+  // Issue #581 — the Send Payment button submits the form natively
+  // (type="submit"), linked to the form via its `form` attribute, instead of
+  // re-dispatching a FormEvent handler through an unsafe `as unknown as`
+  // onClick cast.
+  it("renders the Send Payment button as a type=submit button tied to the form", () => {
+    render(<TransactionPanel />);
+
+    const form = document.querySelector("form");
+    expect(form).not.toBeNull();
+    const sendButton = screen.getByRole("button", { name: /^Send (XLM|USDC)/ });
+    expect(sendButton).toHaveAttribute("type", "submit");
+    expect(sendButton).toHaveAttribute("form", form!.id);
+  });
+
   it("does not submit until Confirm & Sign is clicked in the modal", async () => {
     const mockSubmit = vi.fn().mockResolvedValue({ data: { hash: "h1", ledger: 1 }, error: null });
     mockGetClient(mockSubmit);
diff --git a/src/lib/mock-client.test.ts b/src/lib/mock-client.test.ts
index a2bc66d..aa079bf 100644
--- a/src/lib/mock-client.test.ts
+++ b/src/lib/mock-client.test.ts
@@ -108,17 +108,52 @@ describe("mock-client", () => {
     expect(page1.total).toBe(MOCK_HISTORY.length);
   });
 
-  it("verifies instance isolation between multiple createMockClient invocations", async () => {
+  // Issue #573 — the Soroban screen must be functional against the mock
+  // client: invokeContract/simulateContract return real result data (never
+  // "Not implemented") and getEvents returns actual events.
+  it("verifySoroban invokeContract resolves with result data, not 'Not implemented'", async () => {
+    const { createMockClient, MOCK_ADDRESS: mockAddress } = await import("./mock-client");
+    const client = createMockClient();
+
+    const res = await client.soroban.invokeContract({
+      contractId: "C123",
+      method: "transfer",
+      args: [],
+      sourceAccount: mockAddress,
+    });
+
+    expect(res.error).toBeNull();
+    expect(res.status).toBe("success");
+    expect(res.data).not.toBeNull();
+    expect(res.data).not.toBe("Not implemented");
+    expect(res.data).toHaveProperty("success", true);
+    expect(res.data).toHaveProperty("txHash");
+  });
+
+  it("verifySoroban simulateContract resolves with result data", async () => {
     const { createMockClient } = await import("./mock-client");
-    const clientA = createMockClient("testnet");
-    const clientB = createMockClient("public");
-
-    if ("network" in clientA && "network" in clientB) {
-      const netA = await clientA.network.getNetwork();
-      const netB = await clientB.network.getNetwork();
-      expect(netA.data?.name).toBe("testnet");
-      expect(netB.data?.name).toBe("mainnet");
-    }
+    const client = createMockClient();
+
+    const res = await client.soroban.simulateContract({
+      contractId: "C123",
+      method: "balance",
+      args: [{ address: "GAAZI4TCR3TY5OJHCTJC2A4QSY6CJWJH5IAJTGKIN2ER7LBNVKOCCWNA" }],
+    });
+
+    expect(res.error).toBeNull();
+    expect(res.status).toBe("success");
+    expect(res.data).not.toBeNull();
+  });
+
+  it("verifySoroban getEvents returns event data for a contract", async () => {
+    const { createMockClient } = await import("./mock-client");
+    const client = createMockClient();
+
+    const res = await client.soroban.getEvents("C123", 10);
+
+    expect(res.error).toBeNull();
+    expect(Array.isArray(res.data)).toBe(true);
+    expect(res.data!.length).toBeGreaterThan(0);
   });
 });
 
diff --git a/src/lib/mock-client.ts b/src/lib/mock-client.ts
index ba71afb..d2cbb81 100644
--- a/src/lib/mock-client.ts
+++ b/src/lib/mock-client.ts
@@ -414,7 +414,11 @@ export function createMockClient(
     },
     soroban: {
       invokeContract: async (_params: InvokeParams) => ({
-        data: null,
+        data: {
+          success: true,
+          result: { status: "ok", output: "mock-invoke-output" },
+          txHash: deterministicMock.generateTransactionHash(),
+        },
         error: null,
         status: "success" as const,
       }),