diff --git a/src/lib/server/orders-service-review.test.ts b/src/lib/server/orders-service-review.test.ts
index 9a3d81f..b2dfd2e 100644
--- a/src/lib/server/orders-service-review.test.ts
+++ b/src/lib/server/orders-service-review.test.ts
@@ -188,6 +188,88 @@ describe("updateOrderReviewFields", () => {
     expect(result.order_number).toBe("ORD-2026-07-001");
     expect(result.customer).toBe("cust-1");
   });
+
+  it("escapes embedded quotes in order_number before building the collision filter", async () => {
+    // An order_number containing `"` would break the filter
+    // expression unless we escape embedded quotes before
+    // interpolating. Spy on getList to capture the filter
+    // the service actually sends.
+    const order = await pbMock.collection("orders").create({
+      order_number: "ORD-2026-07-001",
+      customer: "cust-1",
+    });
+
+    const originalCollection = pbMock.collection;
+    const captured: string[] = [];
+    pbMock.collection = (name: string) => {
+      const col = originalCollection(name);
+      if (name === "orders") {
+        const originalGetList = col.getList;
+        col.getList = vi.fn(async (...args: unknown[]) => {
+          const opts = (args[2] as { filter?: string } | undefined) || {};
+          if (opts.filter) captured.push(opts.filter);
+          return originalGetList(...(args as Parameters<typeof col.getList>));
+        });
+      }
+      return col;
+    };
+
+    try {
+      // Pick an order_number that contains a literal quote. The
+      // unescaped filter would be `order_number = "ORD "foo" && id != "..."`,
+      // which would either fail to parse or match the wrong rows.
+      await updateOrderReviewFields(order.id, {
+        order_number: 'ORD "weird"',
+      });
+
+      expect(captured.length).toBeGreaterThan(0);
+      // The filter MUST escape the `"` inside the literal — look for
+      // the backslash-escaped quote in the captured string.
+      const filter = captured[captured.length - 1];
+      expect(filter).toContain('ORD \\"weird\\"');
+    } finally {
+      pbMock.collection = originalCollection;
+    }
+  });
+
+  it("maps a PB unique-constraint write error back to OrderNumberCollisionError", async () => {
+    // Two callers race past the pre-write check; the loser's update
+    // then throws on the unique index. The service should catch that
+    // and surface a structured collision error (with the colliding
+    // row's id) rather than letting it bubble up as a 500.
+    const order = await pbMock.collection("orders").create({
+      order_number: "ORD-2026-07-001",
+      customer: "cust-1",
+    });
+    await pbMock.collection("orders").create({
+      order_number: "ORD-2026-07-002",
+      customer: "cust-2",
+    });
+
+    const originalCollection = pbMock.collection;
+    pbMock.collection = (name: string) => {
+      const col = originalCollection(name);
+      if (name === "orders") {
+        col.update = vi.fn(async () => {
+          const err = new Error(
+            "UNIQUE constraint failed: orders.order_number",
+          );
+          throw err;
+        });
+      }
+      return col;
+    };
+
+    try {
+      await expect(
+        updateOrderReviewFields(order.id, {
+          order_number: "ORD-2026-07-002",
+        }),
+      ).rejects.toBeInstanceOf(OrderNumberCollisionError);
+    } finally {
+      pbMock.collection = originalCollection;
+    }
+  });
 });
 
 describe("updateOrderItemsPrices", () => {
@@ -394,4 +476,49 @@ describe("updateOrderItemsPrices", () => {
     // markup_percent must mirror markup — the two fields stay in lock-step.
     expect(item.markup_percent).toBe(140);
   });
+
+  it("rejects items that belong to a different order", async () => {
+    // Two orders, each with its own item.
+    const orderA = await pbMock.collection("orders").create({
+      order_number: "ORD-2026-07-001",
+    });
+    const orderB = await pbMock.collection("orders").create({
+      order_number: "ORD-2026-07-002",
+    });
+    await pbMock.collection("order_items").create({
+      id: "item-a",
+      order: orderA.id,
+      description: "A's drill",
+      quantity: 2,
+      selling_price: 50,
+      cost_price: 25,
+      markup: 100,
+    });
+    await pbMock.collection("order_items").create({
+      id: "item-b",
+      order: orderB.id,
+      description: "B's bit",
+      quantity: 1,
+      selling_price: 10,
+      cost_price: 5,
+      markup: 100,
+    });
+
+    // Caller targets order A but slips in order B's item — the cross-
+    // order check must catch it and not modify item-b.
+    const result = await updateOrderItemsPrices(orderA.id, [
+      { id: "item-a", quantity: 7 },
+      { id: "item-b", quantity: 99 },
+    ]);
+
+    expect(result.updated).toBe(1);
+    expect(result.failed).toEqual([
+      { id: "item-b", error: "Item does not belong to this order" },
+    ]);
+
+    const itemA = await pbMock.collection("order_items").getOne("item-a");
+    expect(itemA.quantity).toBe(7);
+    const itemB = await pbMock.collection("order_items").getOne("item-b");
+    expect(itemB.quantity).toBe(1); // unchanged
+  });
 });