diff --git a/src/components/orders-review-modal.test.tsx b/src/components/orders-review-modal.test.tsx
new file mode 100644
index 0000000..4f5c545
--- /dev/null
+++ b/src/components/orders-review-modal.test.tsx
@@ -0,0 +1,191 @@
+import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
+import { render, screen, fireEvent, waitFor, cleanup } from "@testing-library/react";
+
+vi.mock("@/components/ui/customer-search", () => ({
+  CustomerSearch: ({
+    onValueChange,
+    value,
+  }: {
+    onValueChange: (v: string) => void;
+    value: string;
+    customers: unknown[];
+  }) => (
+    <button
+      type="button"
+      data-testid="customer-search-mock"
+      onClick={() => onValueChange("cust-new")}
+    >
+      {value || "(unset)"}
+    </button>
+  ),
+}));
+
+vi.mock("sonner", () => ({
+  toast: { success: vi.fn(), error: vi.fn() },
+}));
+
+import { OrdersReviewModal } from "./orders-review-modal";
+import type { Order, OrderItem, Customer, Company } from "@/lib/types";
+
+const baseOrder: Order = {
+  id: "order-1",
+  created: "2026-07-28T00:00:00Z",
+  updated: "2026-07-28T00:00:00Z",
+  collectionId: "c1",
+  collectionName: "orders",
+  order_number: "ORD-2026-07-001",
+  company: "comp-1",
+  customer: "cust-1",
+  quote: "quote-1",
+  notes: "",
+  quote_matching_attempted: true,
+  quote_match_confidence: 1,
+  potential_quote: "",
+  potential_quote_confidence: 0,
+  is_repair_order: false,
+  rep: "Maria",
+  invoiced: false,
+  quote_reference_text: "",
+  quote_match_method: "",
+};
+
+const baseCustomer: Customer = {
+  id: "cust-1",
+  created: "",
+  updated: "",
+  collectionId: "",
+  collectionName: "",
+  customer: "J. Smith",
+  email: "",
+  alternative_email: "",
+  buyer_email: "",
+  number: "",
+  company: "comp-1",
+  dateadded: "",
+  lastvisiteddate: "",
+  rep: "",
+  description: "",
+};
+
+const baseCompany: Company = {
+  id: "comp-1",
+  created: "",
+  updated: "",
+  collectionId: "",
+  collectionName: "",
+  company: "Acme (Pty) Ltd",
+  address: "",
+  vendor: "",
+  company_email: "",
+  company_tel: "",
+};
+
+const baseItems: OrderItem[] = [
+  {
+    id: "item-1",
+    created: "",
+    updated: "",
+    collectionId: "",
+    collectionName: "",
+    description: "HSS drill 6mm",
+    po_description: "",
+    quantity: 2,
+    order_qty: 2,
+    selling_price: 50,
+    supplier: "",
+    cost_price: 25,
+    markup: 100,
+    purchase_order: "",
+    item_status: "pending",
+    in_stock: false,
+    notes: "",
+  },
+];
+
+const baseProps = () => ({
+  open: true,
+  onClose: vi.fn(),
+  onSaved: vi.fn(),
+  order: baseOrder,
+  items: baseItems,
+  customers: [baseCustomer],
+  customer: baseCustomer,
+  company: baseCompany,
+  quoteEmail: { subject: "Re: RFQ", body: "Hi team..." },
+  attachments: [],
+});
+
+describe("OrdersReviewModal", () => {
+  beforeEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  afterEach(() => {
+    cleanup();
+  });
+
+  it("renders order number and customer in the header", () => {
+    render(<OrdersReviewModal {...baseProps()} />);
+    expect(
+      screen.getByDisplayValue("ORD-2026-07-001"),
+    ).toBeInTheDocument();
+    expect(screen.getByText("J. Smith")).toBeInTheDocument();
+    expect(screen.getByText("Acme (Pty) Ltd")).toBeInTheDocument();
+  });
+
+  it("renders one row per line item", () => {
+    render(<OrdersReviewModal {...baseProps()} />);
+    expect(screen.getByText("HSS drill 6mm")).toBeInTheDocument();
+    expect(screen.getByDisplayValue("2")).toBeInTheDocument();
+    expect(screen.getByDisplayValue("50")).toBeInTheDocument();
+  });
+
+  it("Save button is disabled until a field is changed", () => {
+    render(<OrdersReviewModal {...baseProps()} />);
+    const save = screen.getByRole("button", { name: /save/i });
+    expect(save).toBeDisabled();
+  });
+
+  it("Save button becomes enabled after editing the order number", () => {
+    render(<OrdersReviewModal {...baseProps()} />);
+    const numberInput = screen.getByDisplayValue("ORD-2026-07-001");
+    fireEvent.change(numberInput, {
+      target: { value: "ORD-2026-07-014" },
+    });
+    const save = screen.getByRole("button", { name: /save/i });
+    expect(save).not.toBeDisabled();
+  });
+
+  it("renders inline error from the API on 409", async () => {
+    const fetchMock = vi
+      .spyOn(global, "fetch")
+      .mockResolvedValueOnce(
+        new Response(
+          JSON.stringify({
+            error: "order_number_collision",
+            collidingOrderId: "order-other",
+            attemptedNumber: "ORD-2026-07-014",
+          }),
+          { status: 409 },
+        ),
+      );
+
+    render(<OrdersReviewModal {...baseProps()} />);
+    const numberInput = screen.getByDisplayValue("ORD-2026-07-001");
+    fireEvent.change(numberInput, {
+      target: { value: "ORD-2026-07-014" },
+    });
+    fireEvent.click(screen.getByRole("button", { name: /save/i }));
+
+    await waitFor(() => {
+      expect(
+        screen.getByText(/ORD-2026-07-014 is already used by another order/i),
+      ).toBeInTheDocument();
+    });
+
+    expect(fetchMock).toHaveBeenCalledWith(
+      "/api/v1/orders/order-1/review-save",
+      expect.objectContaining({ method: "POST" }),
+    );
+  });
+});
diff --git a/src/components/orders-review-modal.tsx b/src/components/orders-review-modal.tsx
new file mode 100644
index 0000000..417b118
--- /dev/null
+++ b/src/components/orders-review-modal.tsx
@@ -0,0 +1,550 @@
+"use client";
+
+import { useCallback, useEffect, useMemo, useState } from "react";
+import {
+  AlertTriangle,
+  Check,
+  ExternalLink,
+  Loader2,
+  Mail,
+  Paperclip,
+  X,
+} from "lucide-react";
+import { Button } from "@/components/ui/button";
+import { Card, CardContent, CardHeader, CardTitle } from "@/components/ui/card";
+import { Input } from "@/components/ui/input";
+import { Label } from "@/components/ui/label";
+import { CustomerSearch } from "@/components/ui/customer-search";
+import { toast } from "sonner";
+import { cn } from "@/lib/utils";
+import type {
+  Company,
+  Customer,
+  Order,
+  OrderItem,
+  QuoteAttachment,
+} from "@/lib/types";
+
+/**
+ * Orders review modal — Task 4 scaffold.
+ *
+ * Renders an order's header (order_number, customer, company, rep) and
+ * editable line items on the left, with the source-of-truth panel on
+ * the right. The preview chain (email body + attachments) lands in
+ * Task 5; this version ships the header + items + dirty-state gate +
+ * save flow (with inline 409 collision error rendering).
+ *
+ * The save flow posts a single patch to `/api/v1/orders/{id}/review-save`
+ * — see the route for the request shape and error envelope.
+ */
+
+const round2 = (n: number) => Math.round(n * 100) / 100;
+
+type Lock = "cost" | "selling";
+
+export interface OrdersReviewModalProps {
+  open: boolean;
+  onClose: () => void;
+  onSaved: () => void;
+  order: Order;
+  items: OrderItem[];
+  customers: Customer[];
+  customer: Customer;
+  company: Company;
+  quoteEmail: { subject: string; body: string };
+  attachments: QuoteAttachment[];
+}
+
+interface ItemDraft {
+  quantity: number | null;
+  selling_price: number | null;
+  cost_price: number | null;
+  markup: number | null;
+  lock: Lock;
+}
+
+function initialItemDraft(it: OrderItem): ItemDraft {
+  return {
+    quantity: it.quantity,
+    selling_price: it.selling_price,
+    cost_price: it.cost_price,
+    markup: it.markup ?? null,
+    lock:
+      it.cost_price && it.cost_price > 0 ? "cost" : "selling",
+  };
+}
+
+export function OrdersReviewModal({
+  open,
+  onClose,
+  onSaved,
+  order,
+  items,
+  customers,
+  customer,
+  company,
+  quoteEmail,
+  attachments,
+}: OrdersReviewModalProps) {
+  const [orderNumber, setOrderNumber] = useState(order.order_number);
+  const [customerId, setCustomerId] = useState(order.customer);
+  const [itemDrafts, setItemDrafts] = useState<Record<string, ItemDraft>>(
+    () =>
+      Object.fromEntries(
+        items.map((it) => [it.id, initialItemDraft(it)]),
+      ),
+  );
+  const [numberError, setNumberError] = useState<string | null>(null);
+  const [collidingOrderId, setCollidingOrderId] = useState<string | null>(null);
+  const [saving, setSaving] = useState(false);
+
+  // Re-seed local state when the modal opens for a different order.
+  // Parent already remounts via `key={order.id}`, but defensively
+  // re-seed here too in case anyone forgets the key.
+  useEffect(() => {
+    if (!open) return;
+    setOrderNumber(order.order_number);
+    setCustomerId(order.customer);
+    setItemDrafts(
+      Object.fromEntries(items.map((it) => [it.id, initialItemDraft(it)])),
+    );
+    setNumberError(null);
+    setCollidingOrderId(null);
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [open, order.id]);
+
+  const dirty = useMemo(() => {
+    if (orderNumber !== order.order_number) return true;
+    if (customerId !== order.customer) return true;
+    for (const it of items) {
+      const d = itemDrafts[it.id];
+      if (!d) continue;
+      if (d.quantity !== it.quantity) return true;
+      if (d.selling_price !== it.selling_price) return true;
+      if (d.cost_price !== it.cost_price) return true;
+      if ((d.markup ?? null) !== (it.markup ?? null)) return true;
+    }
+    return false;
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [orderNumber, customerId, itemDrafts, order.id]);
+
+  const updateItemDraft = useCallback(
+    (id: string, patch: Partial<ItemDraft>) => {
+      setItemDrafts((prev) => ({ ...prev, [id]: { ...prev[id], ...patch } }));
+    },
+    [],
+  );
+
+  const onCostChange = (id: string, raw: string) => {
+    const value = Number(raw) || 0;
+    const d = itemDrafts[id];
+    if (!d) return;
+    const newSelling = round2(value * (1 + (d.markup ?? 0) / 100));
+    updateItemDraft(id, {
+      cost_price: value,
+      selling_price: newSelling,
+      lock: "cost",
+    });
+  };
+
+  const onSellingChange = (id: string, raw: string) => {
+    const value = Number(raw) || 0;
+    const d = itemDrafts[id];
+    if (!d) return;
+    const newCost =
+      (d.markup ?? 0) > -100 ? round2(value / (1 + (d.markup ?? 0) / 100)) : 0;
+    updateItemDraft(id, {
+      selling_price: value,
+      cost_price: newCost,
+      lock: "selling",
+    });
+  };
+
+  const onMarkupChange = (id: string, raw: string) => {
+    const value = Number(raw) || 0;
+    const d = itemDrafts[id];
+    if (!d) return;
+    if (d.lock === "cost") {
+      const newSelling = round2((d.cost_price ?? 0) * (1 + value / 100));
+      updateItemDraft(id, { markup: value, selling_price: newSelling });
+    } else {
+      const newCost =
+        value > -100 ? round2((d.selling_price ?? 0) / (1 + value / 100)) : 0;
+      updateItemDraft(id, { markup: value, cost_price: newCost });
+    }
+  };
+
+  const onQuantityChange = (id: string, raw: string) => {
+    const value = raw === "" ? null : Number(raw);
+    updateItemDraft(id, { quantity: value });
+  };
+
+  const handleSave = async () => {
+    setSaving(true);
+    setNumberError(null);
+    setCollidingOrderId(null);
+
+    const body: {
+      order_number?: string;
+      customer?: string;
+      items?: Array<{
+        id: string;
+        quantity?: number | null;
+        selling_price?: number | null;
+        cost_price?: number | null;
+      }>;
+    } = {};
+
+    if (orderNumber !== order.order_number) body.order_number = orderNumber;
+    if (customerId !== order.customer) body.customer = customerId;
+
+    const dirtyItems = items
+      .map((it) => {
+        const d = itemDrafts[it.id];
+        if (!d) return null;
+        const changed: {
+          id: string;
+          quantity?: number | null;
+          selling_price?: number | null;
+          cost_price?: number | null;
+        } = { id: it.id };
+        let isDirty = false;
+        if (d.quantity !== it.quantity) {
+          changed.quantity = d.quantity;
+          isDirty = true;
+        }
+        if (d.selling_price !== it.selling_price) {
+          changed.selling_price = d.selling_price;
+          isDirty = true;
+        }
+        if (d.cost_price !== it.cost_price) {
+          changed.cost_price = d.cost_price;
+          isDirty = true;
+        }
+        return isDirty ? changed : null;
+      })
+      .filter((x): x is NonNullable<typeof x> => x !== null);
+
+    if (dirtyItems.length > 0) body.items = dirtyItems;
+
+    try {
+      const res = await fetch(
+        `/api/v1/orders/${order.id}/review-save`,
+        {
+          method: "POST",
+          headers: { "Content-Type": "application/json" },
+          body: JSON.stringify(body),
+        },
+      );
+
+      if (res.status === 409) {
+        const err = await res.json();
+        setNumberError(
+          `${err.attemptedNumber} is already used by another order.`,
+        );
+        setCollidingOrderId(err.collidingOrderId);
+        return;
+      }
+
+      if (!res.ok) {
+        const err = await res.json().catch(() => ({}));
+        throw new Error(err.error || `Save failed (HTTP ${res.status})`);
+      }
+
+      const result = await res.json();
+      if (result.items?.failed?.length > 0) {
+        toast.error(
+          `Saved ${result.items.updated} items, ${result.items.failed.length} failed`,
+        );
+        return;
+      }
+
+      toast.success("Saved");
+      onSaved();
+      onClose();
+    } catch (err) {
+      toast.error(err instanceof Error ? err.message : "Save failed");
+    } finally {
+      setSaving(false);
+    }
+  };
+
+  // Esc closes without saving (no confirm-discard in v1; dirty work is
+  // small and the operator can re-open to retry).
+  useEffect(() => {
+    if (!open) return;
+    const onKey = (e: KeyboardEvent) => {
+      if (e.key === "Escape" && !saving) onClose();
+    };
+    window.addEventListener("keydown", onKey);
+    return () => window.removeEventListener("keydown", onKey);
+  }, [open, saving, onClose]);
+
+  if (!open) return null;
+
+  return (
+    <div
+      className="fixed inset-0 z-50 flex items-center justify-center bg-black/50 p-4"
+      role="dialog"
+      aria-modal="true"
+      aria-labelledby="orders-review-title"
+      onClick={(e) => {
+        if (e.target === e.currentTarget && !saving) onClose();
+      }}
+    >
+      <Card className="w-full max-w-5xl max-h-[90vh] flex flex-col">
+        <CardHeader className="flex flex-row items-start justify-between gap-4 space-y-0 border-b">
+          <div className="min-w-0 flex-1">
+            <CardTitle
+              id="orders-review-title"
+              className="text-sm flex items-center gap-2"
+            >
+              <AlertTriangle className="h-4 w-4 text-warn-foreground" />
+              Review order
+            </CardTitle>
+            <p className="mt-1 text-xs text-muted-foreground">
+              Verify AI-populated fields against the source email &amp;
+              attachments.
+            </p>
+          </div>
+          <button
+            type="button"
+            onClick={onClose}
+            disabled={saving}
+            aria-label="Close"
+            className="inline-flex items-center justify-center rounded-md p-1 text-muted-foreground hover:bg-accent hover:text-foreground disabled:opacity-50"
+          >
+            <X className="h-4 w-4" />
+          </button>
+        </CardHeader>
+
+        <CardContent className="flex-1 overflow-y-auto space-y-4 p-4">
+          {/* Header strip */}
+          <div className="grid grid-cols-1 md:grid-cols-2 gap-3">
+            <div className="space-y-1.5">
+              <Label className="text-xs">Order number</Label>
+              <Input
+                value={orderNumber}
+                onChange={(e) => {
+                  setOrderNumber(e.target.value);
+                  setNumberError(null);
+                  setCollidingOrderId(null);
+                }}
+                className={cn(
+                  "h-9 font-mono text-sm",
+                  numberError && "border-destructive focus-visible:ring-destructive/40",
+                )}
+                data-testid="review-order-number"
+              />
+              {numberError && (
+                <p
+                  className="text-[11px] text-destructive flex items-center gap-1"
+                  data-testid="review-order-number-error"
+                >
+                  <AlertTriangle className="h-3 w-3" />
+                  {numberError}
+                  {collidingOrderId && (
+                    <a
+                      href={`/orders/${collidingOrderId}`}
+                      className="underline hover:no-underline inline-flex items-center gap-0.5"
+                    >
+                      open existing <ExternalLink className="h-2.5 w-2.5" />
+                    </a>
+                  )}
+                </p>
+              )}
+            </div>
+
+            <div className="space-y-1.5">
+              <Label className="text-xs">Customer</Label>
+              <CustomerSearch
+                value={customerId}
+                onValueChange={setCustomerId}
+                customers={customers}
+                placeholder="Pick a customer…"
+              />
+              <p className="text-[11px] text-muted-foreground">
+                {customer.customer || "(no customer name)"}
+              </p>
+            </div>
+
+            <div className="space-y-1.5">
+              <Label className="text-xs">Company</Label>
+              <p className="h-9 inline-flex items-center px-3 rounded-md border bg-muted/30 text-sm">
+                {company.company}
+              </p>
+            </div>
+
+            <div className="space-y-1.5">
+              <Label className="text-xs">Rep</Label>
+              <p className="h-9 inline-flex items-center px-3 rounded-md border bg-muted/30 text-sm">
+                {order.rep || "—"}
+              </p>
+            </div>
+          </div>
+
+          {/* Items table (left side) + preview placeholder (right side).
+              The preview region is filled in by Task 5. */}
+          <div className="grid grid-cols-1 lg:grid-cols-2 gap-4">
+            <div>
+              <h3 className="text-xs font-semibold uppercase tracking-wide text-muted-foreground mb-2">
+                Order items
+              </h3>
+              {items.length === 0 ? (
+                <p className="text-xs text-muted-foreground italic">
+                  No line items on this order.
+                </p>
+              ) : (
+                <ul className="divide-y rounded-md border bg-card">
+                  {items.map((it) => {
+                    const d = itemDrafts[it.id];
+                    if (!d) return null;
+                    return (
+                      <li key={it.id} className="p-3 space-y-2">
+                        <p className="text-sm font-medium truncate">
+                          {it.description || "(no description)"}
+                        </p>
+                        <div className="grid grid-cols-4 gap-2">
+                          <div className="space-y-1">
+                            <Label className="text-[10px] text-muted-foreground">
+                              Qty
+                            </Label>
+                            <Input
+                              type="number"
+                              value={d.quantity ?? ""}
+                              onChange={(e) =>
+                                onQuantityChange(it.id, e.target.value)
+                              }
+                              className="h-8 text-xs tabular-nums"
+                            />
+                          </div>
+                          <div className="space-y-1">
+                            <Label className="text-[10px] text-muted-foreground">
+                              Cost
+                            </Label>
+                            <Input
+                              type="number"
+                              value={d.cost_price ?? ""}
+                              onChange={(e) => onCostChange(it.id, e.target.value)}
+                              className={cn(
+                                "h-8 text-xs tabular-nums",
+                                d.lock === "cost" && "border-warn/40 bg-warn/10",
+                              )}
+                            />
+                          </div>
+                          <div className="space-y-1">
+                            <Label className="text-[10px] text-muted-foreground">
+                              Markup %
+                            </Label>
+                            <Input
+                              type="number"
+                              value={d.markup ?? ""}
+                              onChange={(e) =>
+                                onMarkupChange(it.id, e.target.value)
+                              }
+                              className="h-8 text-xs tabular-nums"
+                            />
+                          </div>
+                          <div className="space-y-1">
+                            <Label className="text-[10px] text-muted-foreground">
+                              Selling
+                            </Label>
+                            <Input
+                              type="number"
+                              value={d.selling_price ?? ""}
+                              onChange={(e) =>
+                                onSellingChange(it.id, e.target.value)
+                              }
+                              className={cn(
+                                "h-8 text-xs tabular-nums",
+                                d.lock === "selling" && "border-warn/40 bg-warn/10",
+                              )}
+                            />
+                          </div>
+                        </div>
+                      </li>
+                    );
+                  })}
+                </ul>
+              )}
+            </div>
+
+            <div>
+              <h3 className="text-xs font-semibold uppercase tracking-wide text-muted-foreground mb-2">
+                Source of truth
+              </h3>
+              {/* Task 5 fills this in. */}
+              <SourceOfTruth
+                quoteEmail={quoteEmail}
+                attachments={attachments}
+              />
+            </div>
+          </div>
+        </CardContent>
+
+        <div className="flex items-center justify-end gap-2 border-t p-4">
+          <Button
+            variant="outline"
+            size="sm"
+            onClick={onClose}
+            disabled={saving}
+          >
+            Cancel
+          </Button>
+          <Button
+            size="sm"
+            onClick={handleSave}
+            disabled={!dirty || saving}
+            data-testid="review-save-button"
+          >
+            {saving ? (
+              <Loader2 className="h-3 w-3 mr-1 animate-spin" />
+            ) : (
+              <Check className="h-3 w-3 mr-1" />
+            )}
+            Save
+          </Button>
+        </div>
+      </Card>
+    </div>
+  );
+}
+
+// --- Source-of-truth panel (filled out in Task 5) -------------------------
+function SourceOfTruth({
+  quoteEmail,
+  attachments,
+}: {
+  quoteEmail: { subject: string; body: string };
+  attachments: QuoteAttachment[];
+}) {
+  if (attachments.length === 0) {
+    return (
+      <div className="rounded-md border bg-muted/30 p-3 text-xs space-y-2">
+        <div className="flex items-center gap-1.5 font-semibold uppercase tracking-wide text-muted-foreground">
+          <Mail className="h-3 w-3" />
+          Email
+        </div>
+        <p className="text-foreground font-medium">{quoteEmail.subject || "(no subject)"}</p>
+        <pre className="whitespace-pre-wrap font-sans text-muted-foreground max-h-64 overflow-y-auto">
+          {quoteEmail.body || "(no body)"}
+        </pre>
+      </div>
+    );
+  }
+  return (
+    <div className="rounded-md border bg-muted/30 p-3 text-xs space-y-2">
+      <div className="flex items-center gap-1.5 font-semibold uppercase tracking-wide text-muted-foreground">
+        <Paperclip className="h-3 w-3" />
+        Attachments ({attachments.length}) — preview added in Task 5
+      </div>
+      <ul className="space-y-1">
+        {attachments.map((a) => (
+          <li key={a.id} className="text-muted-foreground truncate">
+            {a.filename}
+          </li>
+        ))}
+      </ul>
+    </div>
+  );
+}