diff --git a/src/app/api/mcp/route.test.ts b/src/app/api/mcp/route.test.ts
index 4929800..5aa56a6 100644
--- a/src/app/api/mcp/route.test.ts
+++ b/src/app/api/mcp/route.test.ts
@@ -125,6 +125,7 @@ describe("POST /api/mcp", () => {
       "orders.create_from_quote",
       "collection_pool.list",
       "order_items.update_status",
+      "order_items.update",
       "orders.add_attachment",
       "orders.list_attachments",
       "order_items.list",
@@ -702,6 +703,140 @@ describe("POST /api/mcp", () => {
     expect(body.error.message).toMatch(/Missing id/);
   });
 
+  it("tools/call quotes.update with regenerate_pdf:true persists the patch AND re-renders the PDF in one call", async () => {
+    // End-to-end: switching letterhead from CNL → ISHERWOOD and
+    // getting the new PDF back, all in one MCP call. Verifies the
+    // patch is saved FIRST, then the PDF endpoint is called using
+    // the freshly-persisted letterhead.
+    update.mockResolvedValueOnce({
+      id: "q1",
+      company_letterhead: "ISHERWOOD",
+      quote_number: "Q-2026-06-001",
+    });
+    const fetchMock = vi.fn(async () =>
+      new Response(
+        JSON.stringify({
+          ok: true,
+          attachmentId: "att-pdf-1",
+          status: "approval_pending",
+          pdfGeneratedAt: "2026-08-05T01:23:45Z",
+          filename: "Quote-ISHERWOOD-Q-2026-06-001.pdf",
+          skippedItemIds: [],
+          readyItemCount: 3,
+          totalItemCount: 3,
+          isPartial: false,
+        }),
+        { status: 200, headers: { "content-type": "application/json" } },
+      ),
+    );
+    const origFetch = globalThis.fetch;
+    (globalThis as { fetch: unknown }).fetch = fetchMock;
+    try {
+      const res = await POST(
+        mcpRequest({
+          method: "tools/call",
+          id: 54,
+          params: {
+            name: "quotes.update",
+            arguments: {
+              id: "q1",
+              patch: { company_letterhead: "ISHERWOOD" },
+              regenerate_pdf: true,
+            },
+          },
+        }),
+      );
+      expect(res.status).toBe(200);
+      // Patch is saved first
+      expect(update).toHaveBeenCalledWith("q1", { company_letterhead: "ISHERWOOD" });
+      // Then the PDF endpoint is called with the persisted letterhead
+      expect(fetchMock).toHaveBeenCalledTimes(1);
+      const [url, init] = fetchMock.mock.calls[0];
+      expect(String(url)).toMatch(/\/api\/v1\/quotes\/q1\/pdf/);
+      const body = JSON.parse((init as RequestInit).body as string);
+      expect(body.letterhead).toBe("ISHERWOOD");
+      // Response includes both the updated quote AND the rendered PDF
+      const respBody = await res.json();
+      const payload = JSON.parse(respBody.result.content[0].text);
+      expect(payload.quote.company_letterhead).toBe("ISHERWOOD");
+      expect(payload.pdf.attachmentId).toBe("att-pdf-1");
+      expect(payload.pdf.filename).toBe("Quote-ISHERWOOD-Q-2026-06-001.pdf");
+    } finally {
+      (globalThis as { fetch: unknown }).fetch = origFetch;
+    }
+  });
+
+  it("tools/call order_items.update patches whitelisted fields for invoice reconciliation (gap fix 2026-08-05)", async () => {
+    // The agent's reconciliation workflow: read what was collected
+    // (qty_collected), compare to what the supplier invoiced
+    // (qty_invoiced + supplier_invoice_number + cost_price), and patch
+    // the differences. We verify the tool calls the update with only
+    // the whitelisted fields.
+    update.mockResolvedValueOnce({
+      id: "oi1",
+      cost_price: 42.5,
+      qty_invoiced: 9,
+      qty_collected: 10,
+      supplier_invoice_number: "INV-2026-8876",
+    });
+    const res = await POST(
+      mcpRequest({
+        method: "tools/call",
+        id: 70,
+        params: {
+          name: "order_items.update",
+          arguments: {
+            id: "oi1",
+            patch: {
+              cost_price: 42.5,
+              qty_invoiced: 9,
+              supplier_invoice_number: "INV-2026-8876",
+            },
+          },
+        },
+      }),
+    );
+    expect(res.status).toBe(200);
+    expect(update).toHaveBeenCalledTimes(1);
+    expect(update).toHaveBeenCalledWith("oi1", {
+      cost_price: 42.5,
+      qty_invoiced: 9,
+      supplier_invoice_number: "INV-2026-8876",
+    });
+    const body = await res.json();
+    const payload = JSON.parse(body.result.content[0].text);
+    expect(payload.item.cost_price).toBe(42.5);
+    expect(payload.item.qty_invoiced).toBe(9);
+  });
+
+  it("tools/call order_items.update rejects system-controlled fields (order, purchase_order, quote_item, product)", async () => {
+    // Relations must not be patchable via this tool — the agent
+    // should never reassign an order_item to a different order or PO.
+    const res = await POST(
+      mcpRequest({
+        method: "tools/call",
+        id: 71,
+        params: {
+          name: "order_items.update",
+          arguments: {
+            id: "oi1",
+            patch: {
+              order: "o2",              // relation — system-controlled
+              purchase_order: "po2",     // relation — system-controlled
+              quote_item: "qi2",        // relation — system-controlled
+              id: "different-id",       // immutable
+            },
+          },
+        },
+      }),
+    );
+    expect(res.status).toBe(500);
+    const body = await res.json();
+    expect(body.error.message).toMatch(/forbidden_field/);
+    expect(body.error.message).toMatch(/order/);
+    expect(update).not.toHaveBeenCalled();
+  });
+
   it("tools/call quotes.append_reply delegates to the service and surfaces matched_by", async () => {
     appendReplyToQuote.mockResolvedValueOnce({
       quote: { id: "q1", quote_number: "Q-2026-06-001" },