diff --git a/src/app/api/v1/orders/[id]/review-save/route.test.ts b/src/app/api/v1/orders/[id]/review-save/route.test.ts
new file mode 100644
index 0000000..fa79a37
--- /dev/null
+++ b/src/app/api/v1/orders/[id]/review-save/route.test.ts
@@ -0,0 +1,154 @@
+import { describe, it, expect, beforeEach, vi } from "vitest";
+import { NextRequest } from "next/server";
+
+const updateOrderReviewFields = vi.fn();
+const updateOrderItemsPrices = vi.fn();
+const collisionError: Error & { collidingOrderId?: string; attemptedNumber?: string } =
+  new Error("collision");
+collisionError.name = "OrderNumberCollisionError";
+collisionError.collidingOrderId = "order-collide";
+collisionError.attemptedNumber = "ORD-2026-07-014";
+
+vi.mock("@/lib/server/orders-service", () => ({
+  updateOrderReviewFields: (...args: unknown[]) =>
+    updateOrderReviewFields(...args),
+  updateOrderItemsPrices: (...args: unknown[]) =>
+    updateOrderItemsPrices(...args),
+  OrderNumberCollisionError: class extends Error {
+    collidingOrderId: string;
+    attemptedNumber: string;
+    constructor(id: string, num: string) {
+      super(`Order number "${num}" is already in use by another order.`);
+      this.name = "OrderNumberCollisionError";
+      this.collidingOrderId = id;
+      this.attemptedNumber = num;
+    }
+  },
+}));
+
+import { POST } from "./route";
+
+function postJSON(body: unknown) {
+  return new NextRequest(
+    "http://localhost/api/v1/orders/order-1/review-save",
+    {
+      method: "POST",
+      body: JSON.stringify(body),
+    },
+  );
+}
+
+describe("POST /api/v1/orders/[id]/review-save", () => {
+  beforeEach(() => {
+    updateOrderReviewFields.mockReset();
+    updateOrderItemsPrices.mockReset();
+  });
+
+  it("400s when body is not JSON", async () => {
+    const req = new NextRequest(
+      "http://localhost/api/v1/orders/order-1/review-save",
+      { method: "POST", body: "not json" },
+    );
+    const res = await POST(req, { params: Promise.resolve({ id: "order-1" }) });
+    expect(res.status).toBe(400);
+  });
+
+  it("400s when body is null", async () => {
+    const res = await POST(postJSON(null), {
+      params: Promise.resolve({ id: "order-1" }),
+    });
+    expect(res.status).toBe(400);
+  });
+
+  it("200s with empty body (no-op)", async () => {
+    updateOrderReviewFields.mockResolvedValueOnce({
+      id: "order-1",
+      order_number: "ORD-2026-07-001",
+      customer: "cust-1",
+    });
+    const res = await POST(postJSON({}), {
+      params: Promise.resolve({ id: "order-1" }),
+    });
+    expect(res.status).toBe(200);
+    expect(updateOrderReviewFields).toHaveBeenCalledWith("order-1", {});
+    const body = await res.json();
+    expect(body.order.id).toBe("order-1");
+    expect(body.items.updated).toBe(0);
+  });
+
+  it("calls updateOrderReviewFields with order_number when supplied", async () => {
+    updateOrderReviewFields.mockResolvedValueOnce({
+      id: "order-1",
+      order_number: "ORD-2026-07-014",
+      customer: "cust-1",
+    });
+    updateOrderItemsPrices.mockResolvedValueOnce({ updated: 0, failed: [] });
+
+    const res = await POST(
+      postJSON({ order_number: "ORD-2026-07-014" }),
+      { params: Promise.resolve({ id: "order-1" }) },
+    );
+
+    expect(res.status).toBe(200);
+    expect(updateOrderReviewFields).toHaveBeenCalledWith("order-1", {
+      order_number: "ORD-2026-07-014",
+    });
+  });
+
+  it("returns 409 on OrderNumberCollisionError with collidingOrderId", async () => {
+    updateOrderReviewFields.mockRejectedValueOnce(collisionError);
+
+    const res = await POST(
+      postJSON({ order_number: "ORD-2026-07-014" }),
+      { params: Promise.resolve({ id: "order-1" }) },
+    );
+
+    expect(res.status).toBe(409);
+    const body = await res.json();
+    expect(body.error).toBe("order_number_collision");
+    expect(body.collidingOrderId).toBe("order-collide");
+    expect(body.attemptedNumber).toBe("ORD-2026-07-014");
+  });
+
+  it("calls updateOrderItemsPrices when items are supplied", async () => {
+    updateOrderReviewFields.mockResolvedValueOnce({
+      id: "order-1",
+      order_number: "ORD-2026-07-014",
+      customer: "cust-1",
+    });
+    updateOrderItemsPrices.mockResolvedValueOnce({
+      updated: 2,
+      failed: [],
+    });
+
+    const res = await POST(
+      postJSON({
+        order_number: "ORD-2026-07-014",
+        items: [
+          { id: "item-1", quantity: 5 },
+          { id: "item-2", selling_price: 99 },
+        ],
+      }),
+      { params: Promise.resolve({ id: "order-1" }) },
+    );
+
+    expect(res.status).toBe(200);
+    expect(updateOrderItemsPrices).toHaveBeenCalledWith("order-1", [
+      { id: "item-1", quantity: 5 },
+      { id: "item-2", selling_price: 99 },
+    ]);
+    const body = await res.json();
+    expect(body.items.updated).toBe(2);
+    expect(body.items.failed).toEqual([]);
+  });
+
+  it("returns 500 on unexpected service error", async () => {
+    updateOrderReviewFields.mockRejectedValueOnce(new Error("boom"));
+    const res = await POST(postJSON({ order_number: "X" }), {
+      params: Promise.resolve({ id: "order-1" }),
+    });
+    expect(res.status).toBe(500);
+    const body = await res.json();
+    expect(body.error).toMatch(/boom/);
+  });
+});
\ No newline at end of file
diff --git a/src/app/api/v1/orders/[id]/review-save/route.ts b/src/app/api/v1/orders/[id]/review-save/route.ts
new file mode 100644
index 0000000..7bc6854
--- /dev/null
+++ b/src/app/api/v1/orders/[id]/review-save/route.ts
@@ -0,0 +1,108 @@
+import { NextRequest, NextResponse } from "next/server";
+import {
+  OrderNumberCollisionError,
+  updateOrderItemsPrices,
+  updateOrderReviewFields,
+} from "@/lib/server/orders-service";
+
+/**
+ * POST /api/v1/orders/[id]/review-save
+ *
+ * Atomically commits the operator's review-time edits to the order
+ * header (order_number, customer) and any line-item price/qty
+ * patches. The "atomic" guarantee is partial: order_number collision
+ * is checked up-front so a 409 aborts before any field is touched,
+ * but item updates are best-effort per-row (per the
+ * `updateOrderItemsPrices` contract).
+ *
+ * Request body:
+ *   {
+ *     order_number?: string;
+ *     customer?: string;
+ *     items?: Array<{
+ *       id: string;
+ *       quantity?: number | null;
+ *       selling_price?: number | null;
+ *       cost_price?: number | null;
+ *     }>;
+ *   }
+ *
+ * Responses:
+ *   200 — saved. Body: { order: Order, items: { updated, failed } }
+ *   400 — body is missing or not JSON
+ *   404 — order not found (PB throws; caught and mapped)
+ *   409 — order_number collision. Body: { error, collidingOrderId, attemptedNumber }
+ *   500 — anything else
+ */
+export async function POST(
+  req: NextRequest,
+  ctx: { params: Promise<{ id: string }> },
+) {
+  const { id: orderId } = await ctx.params;
+
+  let body: unknown;
+  try {
+    body = await req.json();
+  } catch {
+    return NextResponse.json({ error: "Body must be JSON" }, { status: 400 });
+  }
+  if (body === null || typeof body !== "object") {
+    return NextResponse.json({ error: "Body must be an object" }, { status: 400 });
+  }
+
+  const { order_number, customer, items } = body as {
+    order_number?: string;
+    customer?: string;
+    items?: Array<{
+      id: string;
+      quantity?: number | null;
+      selling_price?: number | null;
+      cost_price?: number | null;
+    }>;
+  };
+
+  try {
+    // Header patch — order_number + customer are bundled because the
+    // collision check needs to fire BEFORE any items[] work runs.
+    // We always go through `updateOrderReviewFields` — even when the
+    // patch is empty — so the no-op path returns the current row and
+    // the route doesn't need a second PB import branch.
+    const headerPatch: { order_number?: string; customer?: string } = {};
+    if (typeof order_number === "string") headerPatch.order_number = order_number;
+    if (typeof customer === "string") headerPatch.customer = customer;
+
+    const order = await updateOrderReviewFields(orderId, headerPatch);
+
+    const itemResult =
+      Array.isArray(items) && items.length > 0
+        ? await updateOrderItemsPrices(orderId, items)
+        : { updated: 0, failed: [] };
+
+    return NextResponse.json({ order, items: itemResult });
+  } catch (err) {
+    // Detect collision by instanceof OR by name — the name check
+    // keeps the route working with mocks that throw a plain Error
+    // stamped with `.name = "OrderNumberCollisionError"`.
+    if (
+      err instanceof OrderNumberCollisionError ||
+      (err instanceof Error && err.name === "OrderNumberCollisionError")
+    ) {
+      const collidingOrderId =
+        (err as Error & { collidingOrderId?: string }).collidingOrderId ?? "";
+      const attemptedNumber =
+        (err as Error & { attemptedNumber?: string }).attemptedNumber ?? "";
+      return NextResponse.json(
+        {
+          error: "order_number_collision",
+          collidingOrderId,
+          attemptedNumber,
+        },
+        { status: 409 },
+      );
+    }
+    const message = err instanceof Error ? err.message : "Save failed";
+    const status =
+      (err as Error & { status?: number }).status === 404 ? 404 : 500;
+    return NextResponse.json({ error: message }, { status });
+  }
+}
\ No newline at end of file