diff --git a/e2e/invoice-detail.spec.ts b/e2e/invoice-detail.spec.ts
index afaa803..165b09e 100644
--- a/e2e/invoice-detail.spec.ts
+++ b/e2e/invoice-detail.spec.ts
@@ -43,4 +43,10 @@ test.describe("invoice detail 3-pane shell", () => {
     await expect(page).toHaveURL(/\/invoices\/inv-/);
     await expect(page.getByTestId("invoice-document-viewer")).toBeVisible();
   });
+
+  test("unknown invoice id shows not-found warning", async ({ page }) => {
+    await page.goto("/invoices/missing-invoice");
+    await expect(page.getByTestId("invoice-not-found")).toBeVisible();
+    await expect(page.getByTestId("invoice-document-viewer")).toHaveCount(0);
+  });
 });
diff --git a/src/domain/invoices/use-invoices.ts b/src/domain/invoices/use-invoices.ts
index d888bec..e5ad475 100644
--- a/src/domain/invoices/use-invoices.ts
+++ b/src/domain/invoices/use-invoices.ts
@@ -13,6 +13,7 @@ import {
   type MockInvoiceLine,
   type MockInvoiceStatus,
 } from "@/mocks";
+import { approvalQueryKeys } from "@/domain/approvals/query-keys";
 import { invoiceQueryKeys } from "@/domain/invoices/query-keys";
 
 async function invalidateInvoiceQueries(
@@ -37,9 +38,9 @@ export function useInvoice(id: string | undefined) {
     queryKey: invoiceQueryKeys.detail(id ?? ""),
     queryFn: () => {
       if (!id) {
-        return undefined;
+        return null;
       }
-      return getMockInvoice(id);
+      return getMockInvoice(id) ?? null;
     },
     enabled: Boolean(id),
   });
@@ -117,6 +118,7 @@ export function useTransitionInvoiceStatus() {
     }) => Promise.resolve(transitionMockInvoiceStatus(id, status, activity)),
     onSuccess: async (_data, variables) => {
       await invalidateInvoiceQueries(queryClient, variables.id);
+      await queryClient.invalidateQueries({ queryKey: approvalQueryKeys.all });
     },
   });
 }
diff --git a/src/mocks/approvals.ts b/src/mocks/approvals.ts
index 6a114b9..2040ca7 100644
--- a/src/mocks/approvals.ts
+++ b/src/mocks/approvals.ts
@@ -69,6 +69,23 @@ export function updateMockApprovalStatus(
   return { ...updated };
 }
 
+/** Keep inbox rows aligned when invoice detail stubs transition status. */
+export function syncMockApprovalsForInvoice(
+  invoiceId: string,
+  status: MockApprovalStatus,
+): MockApprovalItem[] {
+  const updated: MockApprovalItem[] = [];
+  approvalStore = approvalStore.map((item) => {
+    if (item.invoiceId !== invoiceId) {
+      return item;
+    }
+    const next = { ...item, status };
+    updated.push({ ...next });
+    return next;
+  });
+  return updated;
+}
+
 export function resetMockApprovals(): void {
   approvalStore = seedApprovals.map((item) => ({ ...item }));
 }
diff --git a/src/mocks/index.test.ts b/src/mocks/index.test.ts
index 946d8db..f3e8692 100644
--- a/src/mocks/index.test.ts
+++ b/src/mocks/index.test.ts
@@ -124,6 +124,12 @@ describe("mocks module", () => {
     });
     expect(approved.status).toBe("approved");
     expect(approved.activity.some((entry) => entry.message === "Approved")).toBe(true);
+    expect(getMockPendingApprovals().some((item) => item.invoiceId === "inv-2")).toBe(false);
+    expect(getMockApprovals().find((item) => item.invoiceId === "inv-2")?.status).toBe("approved");
+  });
+
+  it("returns undefined for unknown invoice ids", () => {
+    expect(getMockInvoice("missing-invoice")).toBeUndefined();
   });
 
   it("switches mock session user", () => {
diff --git a/src/mocks/index.ts b/src/mocks/index.ts
index d38baea..fa79186 100644
--- a/src/mocks/index.ts
+++ b/src/mocks/index.ts
@@ -64,6 +64,7 @@ export {
   getMockApprovals,
   getMockPendingApprovals,
   resetMockApprovals,
+  syncMockApprovalsForInvoice,
   updateMockApprovalStatus,
   type MockApprovalItem,
   type MockApprovalStatus,
diff --git a/src/mocks/invoices.ts b/src/mocks/invoices.ts
index e3b33f9..c324ad7 100644
--- a/src/mocks/invoices.ts
+++ b/src/mocks/invoices.ts
@@ -1,3 +1,4 @@
+import { syncMockApprovalsForInvoice } from "@/mocks/approvals";
 import { areMocksEnabled } from "@/mocks/env";
 
 export type MockInvoiceStatus = "pending_approval" | "approved" | "scheduled" | "paid" | "rejected";
@@ -515,11 +516,19 @@ export function transitionMockInvoiceStatus(
     createdAt: activity.createdAt ?? new Date().toISOString(),
   };
 
-  return replaceInvoice(index, {
+  const updated = replaceInvoice(index, {
     ...current,
     status,
     activity: [...current.activity, nextActivity],
   });
+
+  if (status === "approved" || status === "rejected") {
+    syncMockApprovalsForInvoice(id, status);
+  } else if (status === "pending_approval") {
+    syncMockApprovalsForInvoice(id, "pending");
+  }
+
+  return updated;
 }
 
 /** Test helper to restore seed data between unit tests. */