feat(F-189): completed feature

backlog/features.json

@@ -7257,13 +7257,15 @@
       "description": "Accept validated negative quantities to cancel purchases fully or partially and issue linked return receipts.",
       "priority": "high",
       "risk": "high",
-      "status": "pending",
+      "status": "done",
       "created_at": "2026-08-22",
       "gates": {
-        "reviewer": false,
-        "security": false,
-        "qa": false
-      }
+        "reviewer": true,
+        "security": true,
+        "qa": true,
+        "close": true
+      },
+      "completed_at": "2026-08-22T21:01:59Z"
     },
     {
       "id": "F-190",

docs/pos/POS_CHECKOUT.md

@@ -159,8 +159,14 @@ Por cada asignación se crea:
 
 El efectivo esperado aumenta por el importe aplicado, no por el efectivo entregado; el cambio no cuenta como ingreso ni efectivo retenido.
 
+## Devoluciones
+
+`POST /pos/sales/:id/returns` registra devoluciones parciales o totales que conservan el UUID de la venta, restauran el stock y emiten un ticket asociado con el prefijo `R-`. La operación queda registrada en `pos_returns`, `reporting_payment_lines` (status `refund`/`partial_refund`), `orders_order_history` y el log de auditoría. Las devoluciones solo operan sobre ventas `pos` y exigen la caja (`x-terminal-id`) y el rol POS. El endpoint antiguo `POST /pos/sales/:id/refund` queda desregistrado.
+
+`GET /pos/sales/:id/items` expone las líneas de la orden con `quantity` y `returnedQuantity` para alimentar el modal de devolución.
+
 ## Próximas ampliaciones
 
-- F-189: cantidades negativas, devoluciones parciales/totales y ticket de devolución.
+- F-190: auditoría completa de actualización/refresco de reporting.
 - F-190: auditoría completa de actualización/refresco de reporting.
 - F-191: cierre de terminal y cierre diario conciliando efectivo, tarjetas, devoluciones y pendientes.

project/apps/pos/src/app/(terminal)/page.tsx

@@ -5,6 +5,7 @@ import DiscountPanel from '@/components/DiscountPanel';
 import FreeItemModal from '@/components/FreeItemModal';
 import PaymentModal from '@/components/PaymentModal';
 import ReceiptModal from '@/components/ReceiptModal';
+import ReturnModal from '@/components/ReturnModal';
 import { posApi } from '@/lib/api-client';
 import { generateIdempotencyKey } from '@/lib/idempotency';
 import { formatPrice } from '@/lib/money';
@@ -112,6 +113,9 @@ export default function RegisterPage() {
   const [loadingPending, setLoadingPending] = useState(false);
   const [restPaymentFor, setRestPaymentFor] = useState<PosPendingSale | null>(null);
   const [processingRest, setProcessingRest] = useState(false);
+  const [returnOrder, setReturnOrder] = useState<{ orderId: string; receipt: PosReceipt } | null>(
+    null,
+  );
 
   const loadConfig = useCallback(async () => {
     setConfigError('');
@@ -1163,6 +1167,26 @@ export default function RegisterPage() {
           receipt={receipt}
           initialEmail={customer?.email ?? receipt.customerEmail ?? ''}
           onDelivered={resetCashier}
+          onReturn={
+            config?.session && config?.terminal
+              ? (orderId, latest) => {
+                  setReturnOrder({ orderId, receipt: latest });
+                }
+              : undefined
+          }
+        />
+      )}
+      {returnOrder && config?.session && config?.terminal && (
+        <ReturnModal
+          receipt={returnOrder.receipt}
+          orderId={returnOrder.orderId}
+          cashSessionId={config.session.id}
+          terminalId={config.terminal.id}
+          onClose={() => setReturnOrder(null)}
+          onReturned={(latest) => {
+            setReturnOrder(null);
+            setReceipt(latest);
+          }}
         />
       )}
     </div>

project/apps/pos/src/components/ReceiptModal.tsx

@@ -9,12 +9,14 @@ interface ReceiptModalProps {
   receipt: PosReceipt;
   initialEmail?: string;
   onDelivered: () => void;
+  onReturn?: (orderId: string, receipt: PosReceipt) => void;
 }
 
 export default function ReceiptModal({
   receipt,
   initialEmail = '',
   onDelivered,
+  onReturn,
 }: ReceiptModalProps) {
   const [email, setEmail] = useState(initialEmail);
   const [sending, setSending] = useState(false);
@@ -166,6 +168,15 @@ export default function ReceiptModal({
           >
             🖨️ Imprimir ticket
           </button>
+          {onReturn && !receipt.isReturn && (
+            <button
+              type="button"
+              onClick={() => onReturn(receipt.orderId, receipt)}
+              className="min-h-12 w-full rounded-xl border border-amber-300 bg-amber-50 font-bold text-amber-800"
+            >
+              ↺ Devolver artículos
+            </button>
+          )}
           <form onSubmit={emailReceipt} className="flex gap-2">
             <label className="sr-only" htmlFor="receipt-email">
               Email del ticket

project/apps/pos/src/components/ReturnModal.tsx

@@ -0,0 +1,233 @@
+'use client';
+
+import { useEffect, useMemo, useState } from 'react';
+import { posApi } from '@/lib/api-client';
+import { formatPrice } from '@/lib/money';
+import { generateIdempotencyKey } from '@/lib/idempotency';
+import type { PosReceipt, PosSaleResponse } from '@/types/checkout';
+
+interface OrderItem {
+  id: string;
+  name: string;
+  quantity: number;
+  returnedQuantity: number;
+  freeItem: boolean;
+  unitPriceCents: number;
+  discountCents: number;
+}
+
+interface ReturnModalProps {
+  receipt: PosReceipt;
+  orderId: string;
+  cashSessionId: string;
+  terminalId: string;
+  onClose: () => void;
+  onReturned: (newReceipt: PosReceipt) => void;
+}
+
+export default function ReturnModal({
+  receipt,
+  orderId,
+  cashSessionId,
+  terminalId,
+  onClose,
+  onReturned,
+}: ReturnModalProps) {
+  const [items, setItems] = useState<OrderItem[]>([]);
+  const [lines, setLines] = useState<Record<string, number>>({});
+  const [reason, setReason] = useState('Cambio/devolución');
+  const [error, setError] = useState('');
+  const [loading, setLoading] = useState(true);
+  const [saving, setSaving] = useState(false);
+
+  useEffect(() => {
+    void (async () => {
+      try {
+        const data = await posApi.listOrderItems<{ items: OrderItem[] }>(orderId);
+        setItems(
+          data.items.map((item) => ({
+            id: item.id,
+            name: item.name,
+            quantity: item.quantity,
+            returnedQuantity: item.returnedQuantity,
+            freeItem: item.freeItem,
+            unitPriceCents: item.unitPriceCents,
+            discountCents: item.discountCents,
+          })),
+        );
+        setLines(
+          Object.fromEntries(data.items.map((item) => [item.id, 0])),
+        );
+      } catch (err) {
+        setError(err instanceof Error ? err.message : 'No se pudieron cargar las líneas');
+      } finally {
+        setLoading(false);
+      }
+    })();
+  }, [orderId]);
+
+  const totalRefund = useMemo(() => {
+    return items.reduce((sum, item) => {
+      const requested = lines[item.id] ?? 0;
+      if (requested <= 0) return sum;
+      const perUnit = Math.max(item.unitPriceCents - item.discountCents, 0);
+      return sum + perUnit * requested;
+    }, 0);
+  }, [lines, items]);
+
+  const submit = async () => {
+    setError('');
+    const itemsPayload = items
+      .map((item) => ({ orderItemId: item.id, returnedQuantity: lines[item.id] ?? 0 }))
+      .filter((line) => line.returnedQuantity > 0);
+    if (itemsPayload.length === 0) {
+      setError('Selecciona al menos una unidad para devolver');
+      return;
+    }
+    setSaving(true);
+    try {
+      const result = await posApi.createReturn<PosSaleResponse>(orderId, {
+        idempotencyKey: generateIdempotencyKey(),
+        cashSessionId,
+        terminalId,
+        reason: reason.trim() || 'Devolución',
+        items: itemsPayload,
+      });
+      onReturned(result.receipt);
+    } catch (err) {
+      setError(err instanceof Error ? err.message : 'No se pudo registrar la devolución');
+    } finally {
+      setSaving(false);
+    }
+  };
+
+  return (
+    <div
+      className="fixed inset-0 z-[70] flex items-center justify-center bg-black/40 p-4"
+      role="dialog"
+      aria-modal="true"
+      aria-labelledby="return-title"
+    >
+      <div className="w-full max-w-md space-y-4 rounded-2xl bg-white p-6 shadow-2xl">
+        <div className="flex items-start justify-between gap-4">
+          <div>
+            <p className="text-sm font-semibold text-amber-600">
+              Devolución · ticket {receipt.receiptNumber}
+            </p>
+            <h2 id="return-title" className="text-2xl font-bold text-gray-900">
+              Devolver artículos
+            </h2>
+          </div>
+          <button
+            type="button"
+            onClick={onClose}
+            aria-label="Cerrar"
+            className="text-2xl text-gray-400 hover:text-gray-700"
+          >
+            ✕
+          </button>
+        </div>
+
+        {loading ? (
+          <p className="text-sm text-gray-500">Cargando…</p>
+        ) : (
+          <>
+            <ul className="space-y-2">
+              {items.map((item) => {
+                const requested = lines[item.id] ?? 0;
+                const max = item.quantity - item.returnedQuantity;
+                const step = item.freeItem ? max : 1;
+                return (
+                  <li
+                    key={item.id}
+                    className="flex items-center justify-between rounded-xl border border-gray-200 bg-gray-50 p-3 text-sm"
+                  >
+                    <div>
+                      <p className="font-medium text-gray-800">{item.name}</p>
+                      <p className="text-xs text-gray-500">
+                        Vendidas {item.quantity} · devueltas {item.returnedQuantity}
+                        {item.freeItem ? ' · artículo libre' : ''}
+                      </p>
+                    </div>
+                    <div className="flex items-center gap-2">
+                      <button
+                        type="button"
+                        onClick={() =>
+                          setLines((current) => ({
+                            ...current,
+                            [item.id]: Math.max(0, requested - step),
+                          }))
+                        }
+                        disabled={requested <= 0}
+                        className="h-8 w-8 rounded-lg border text-lg font-bold disabled:opacity-40"
+                      >
+                        −
+                      </button>
+                      <span className="w-8 text-center text-lg font-bold">{requested}</span>
+                      <button
+                        type="button"
+                        onClick={() =>
+                          setLines((current) => ({
+                            ...current,
+                            [item.id]: Math.min(max, requested + step),
+                          }))
+                        }
+                        disabled={requested === max}
+                        className="h-8 w-8 rounded-lg border text-lg font-bold disabled:opacity-40"
+                      >
+                        +
+                      </button>
+                    </div>
+                  </li>
+                );
+              })}
+            </ul>
+
+            <label className="block text-sm font-medium text-gray-700">
+              Motivo
+              <input
+                type="text"
+                required
+                maxLength={500}
+                value={reason}
+                onChange={(event) => setReason(event.target.value)}
+                className="mt-1 w-full rounded-xl border border-gray-300 px-3 py-2"
+              />
+            </label>
+
+            <div className="rounded-xl bg-amber-50 p-3 text-sm">
+              <p className="flex justify-between font-bold">
+                <span>Reembolso estimado</span>
+                <span>{formatPrice(totalRefund)}</span>
+              </p>
+            </div>
+
+            {error && (
+              <p className="text-sm font-medium text-red-600" aria-live="polite">
+                {error}
+              </p>
+            )}
+            <div className="flex gap-2">
+              <button
+                type="button"
+                onClick={onClose}
+                disabled={saving}
+                className="flex-1 rounded-xl border border-gray-300 py-3 text-sm font-bold disabled:opacity-50"
+              >
+                Cancelar
+              </button>
+              <button
+                type="button"
+                onClick={() => void submit()}
+                disabled={saving || totalRefund === 0}
+                className="flex-1 rounded-xl bg-amber-500 py-3 text-sm font-bold text-white disabled:opacity-50"
+              >
+                {saving ? 'Procesando…' : 'Confirmar devolución'}
+              </button>
+            </div>
+          </>
+        )}
+      </div>
+    </div>
+  );
+}

project/apps/pos/src/lib/api-client.ts

@@ -66,6 +66,15 @@ export const posApi = {
       method: 'POST',
       body: JSON.stringify(data),
     }),
+  /** Apply a partial/full return to a POS sale. */
+  createReturn: <T>(orderId: string, data: unknown) =>
+    apiFetch<T>(`/pos/sales/${encodeURIComponent(orderId)}/returns`, {
+      method: 'POST',
+      body: JSON.stringify(data),
+    }),
+  /** List order items for a sale (used by the return UI). */
+  listOrderItems: <T>(orderId: string) =>
+    apiFetch<T>(`/pos/sales/${encodeURIComponent(orderId)}/items`),
   /** List POS sales for the session, optionally filtered by state. */
   listSales: <T>(params?: { state?: 'PENDING' | 'COMPLETED'; sessionId?: string }) => {
     const qs = new URLSearchParams();

project/apps/pos/src/types/checkout.ts

@@ -61,6 +61,8 @@ export interface PosReceipt {
   header: string | null;
   returnPolicy: string;
   footer: string | null;
+  originalReceiptNumber?: string;
+  isReturn?: boolean;
 }
 
 export interface PosSaleResponse {

project/migrations/056_pos_return_lines.js

@@ -0,0 +1,94 @@
+/**
+ * F-189 — POS returns per-line counters + pos_returns table.
+ *
+ * 1. Adds `orders_items.returned_quantity integer NOT NULL DEFAULT 0` with
+ *    `CHECK (returned_quantity >= 0 AND returned_quantity <= quantity)`.
+ * 2. Creates `pos_returns` as the historical ledger of returns with a unique
+ *    `(order_id, idempotency_key)` index for replay.
+ * 3. Allows `'return'` in `inventory_movements.operation` so cashiers can
+ *    see the movement in inventory history.
+ *
+ * @param {import('node-pg-migrate').MigrationBuilder} pgm
+ */
+
+export const up = (pgm) => {
+  // ── orders_items.returned_quantity ─────────────────────────────────────
+  pgm.sql(`
+    DO $$
+    BEGIN
+      IF NOT EXISTS (
+        SELECT 1 FROM information_schema.columns
+         WHERE table_name = 'orders_items' AND column_name = 'returned_quantity'
+      ) THEN
+        ALTER TABLE orders_items
+          ADD COLUMN returned_quantity integer NOT NULL DEFAULT 0;
+      END IF;
+    END $$
+  `);
+  pgm.sql(`ALTER TABLE orders_items DROP CONSTRAINT IF EXISTS orders_items_returned_quantity_check`);
+  pgm.sql(`
+    ALTER TABLE orders_items
+      ADD CONSTRAINT orders_items_returned_quantity_check
+      CHECK (returned_quantity >= 0 AND returned_quantity <= quantity)
+  `);
+
+  // ── inventory_movements.operation — allow 'return' ─────────────────────
+  pgm.sql(`ALTER TABLE inventory_movements DROP CONSTRAINT IF EXISTS inventory_movements_operation_check`);
+  pgm.sql(`
+    ALTER TABLE inventory_movements
+      ADD CONSTRAINT inventory_movements_operation_check
+      CHECK (operation IN ('reserve','release','confirm','set_available','return'))
+  `);
+
+  // ── pos_returns ─────────────────────────────────────────────────────────
+  pgm.createTable('pos_returns', {
+    id: { type: 'uuid', primaryKey: true, default: pgm.func('gen_random_uuid()') },
+    order_id: { type: 'uuid', notNull: true, references: 'orders_orders(id)', onDelete: 'RESTRICT' },
+    idempotency_key: { type: 'text', notNull: true },
+    terminal_id: { type: 'uuid', notNull: true, references: 'pos_terminals(id)', onDelete: 'RESTRICT' },
+    cash_session_id: { type: 'uuid', notNull: true, references: 'pos_cash_sessions(id)', onDelete: 'RESTRICT' },
+    store_id: { type: 'uuid', notNull: true, references: 'pos_stores(id)', onDelete: 'RESTRICT' },
+    user_id: { type: 'uuid', notNull: true, references: 'backoffice_users(id)', onDelete: 'RESTRICT' },
+    total_cents: { type: 'integer', notNull: true, check: 'total_cents > 0' },
+    status: {
+      type: 'text',
+      notNull: true,
+      check: "status IN ('refund','partial_refund')",
+    },
+    reason: { type: 'text', notNull: true },
+    created_at: { type: 'timestamptz', notNull: true, default: pgm.func('now()') },
+  });
+  pgm.sql(`
+    CREATE UNIQUE INDEX IF NOT EXISTS pos_returns_idempotency_unique_idx
+      ON pos_returns (order_id, idempotency_key)
+  `);
+  pgm.createIndex('pos_returns', ['store_id', 'created_at'], {
+    name: 'pos_returns_store_created_idx',
+  });
+  pgm.createIndex('pos_returns', 'terminal_id', {
+    name: 'pos_returns_terminal_idx',
+    where: 'terminal_id IS NOT NULL',
+  });
+};
+
+export const down = (pgm) => {
+  pgm.dropTable('pos_returns', { ifExists: true });
+  pgm.sql(`ALTER TABLE inventory_movements DROP CONSTRAINT IF EXISTS inventory_movements_operation_check`);
+  pgm.sql(`
+    ALTER TABLE inventory_movements
+      ADD CONSTRAINT inventory_movements_operation_check
+      CHECK (operation IN ('reserve','release','confirm','set_available'))
+  `);
+  pgm.sql(`ALTER TABLE orders_items DROP CONSTRAINT IF EXISTS orders_items_returned_quantity_check`);
+  pgm.sql(`
+    DO $$
+    BEGIN
+      IF EXISTS (
+        SELECT 1 FROM information_schema.columns
+         WHERE table_name = 'orders_items' AND column_name = 'returned_quantity'
+      ) THEN
+        ALTER TABLE orders_items DROP COLUMN returned_quantity;
+      END IF;
+    END $$
+  `);
+};

project/src/app/tests/pos-returns.itest.ts

@@ -0,0 +1,338 @@
+import { createHash } from 'node:crypto';
+import argon2 from 'argon2';
+import type pg from 'pg';
+import { afterAll, beforeAll, describe, expect, it } from 'vitest';
+import { buildApp } from '../build-app.js';
+import { CreatePosSaleUseCase } from '../../modules/pos/index.js';
+import { createPool } from '../../infrastructure/db/pool.js';
+import {
+  getTestDbUrl,
+  recreateDatabase,
+  runMigrations,
+} from '../../infrastructure/db/tests/db-test-support.js';
+
+const hasDb = Boolean(process.env.TEST_DATABASE_URL);
+const STORE_ID = '00000000-0000-0000-0000-000000000001';
+const TERMINAL_ID = '20000000-0000-4000-8000-000000000189';
+const SESSION_ID = '30000000-0000-4000-8000-000000000189';
+const USER_ID = '10000000-0000-4000-8000-000000000189';
+const SESSION_TOKEN = 'f189-session';
+const PRODUCT_ID = '40000000-0000-4000-8000-000000000189';
+const VARIANT_ID = '50000000-0000-4000-8000-000000000189';
+
+function tokenHash(token: string): string {
+  return createHash('sha256').update(token).digest('hex');
+}
+
+function cookie(token: string): string {
+  return `backoffice_session=${token}`;
+}
+
+describe.skipIf(!hasDb)('F-189 POS returns (real PostgreSQL)', () => {
+  const url = hasDb ? getTestDbUrl() : '';
+  let pool: pg.Pool;
+  let app: Awaited<ReturnType<typeof buildApp>>;
+
+  beforeAll(async () => {
+    await recreateDatabase(url);
+    await runMigrations(url, 'up');
+    pool = createPool(url);
+    const passwordHash = await argon2.hash('cashier-189');
+    await pool.query(
+      `INSERT INTO backoffice_users (id, email, password_hash, role)
+       VALUES ($1, 'cashier-f189@example.test', $2, 'pos_cashier')`,
+      [USER_ID, passwordHash],
+    );
+    await pool.query(
+      `INSERT INTO backoffice_sessions (user_id, token_hash, expires_at)
+       VALUES ($1, $2, now() + interval '1 hour')`,
+      [USER_ID, tokenHash(SESSION_TOKEN)],
+    );
+    await pool.query(
+      `INSERT INTO pos_terminals (id, store_id, name, binding_code, bound_at)
+       VALUES ($1, $2, 'Caja F-189', 'F189CODE', now())`,
+      [TERMINAL_ID, STORE_ID],
+    );
+    await pool.query(
+      `INSERT INTO pos_cash_sessions (
+         id, terminal_id, store_id, user_id, opening_cash_cents, expected_cash_cents
+       ) VALUES ($1, $2, $3, $4, 1000, 1000)`,
+      [SESSION_ID, TERMINAL_ID, STORE_ID, USER_ID],
+    );
+    await pool.query(
+      `INSERT INTO catalog_products (id, name, slug, state)
+       VALUES ($1, 'Producto F-189', 'producto-f189', 'active')`,
+      [PRODUCT_ID],
+    );
+    await pool.query(
+      `INSERT INTO catalog_product_variants (id, product_id, sku, ean)
+       VALUES ($1, $2, 'SKU-F189', '8412345678903')`,
+      [VARIANT_ID, PRODUCT_ID],
+    );
+    await pool.query(
+      `INSERT INTO pricing_variant_prices (variant_id, net_unit_amount_cents, vat_rate)
+       VALUES ($1, 1000, 'reduced')`,
+      [VARIANT_ID],
+    );
+    await pool.query(
+      `INSERT INTO inventory_stock (variant_id, store_id, available)
+       VALUES ($1, $2, 10)`,
+      [VARIANT_ID, STORE_ID],
+    );
+    app = await buildApp({ pool, cookieSecure: false });
+  });
+
+  afterAll(async () => {
+    await app.close();
+    await pool.end();
+  });
+
+  it('partially returns a sale, restores partial stock and stays PARTIALLY_REFUNDED', async () => {
+    const useCase = new CreatePosSaleUseCase(pool);
+    const sale = await useCase.execute({
+      idempotencyKey: 'f189-sale-partial',
+      cashSessionId: SESSION_ID,
+      terminalId: TERMINAL_ID,
+      userId: USER_ID,
+      items: [{ kind: 'stock', variantId: VARIANT_ID, quantity: 3, discountCents: 0 }],
+      payments: [{ methodCode: 'cash', amountCents: 3000, tenderedCents: 3000 }],
+    });
+    expect(sale.state).toBe('COMPLETED');
+
+    const items = await pool.query<{ id: string }>(
+      `SELECT id FROM orders_items WHERE order_id = $1`,
+      [sale.orderId],
+    );
+    const firstItemId = items.rows[0]?.id;
+    expect(firstItemId).toBeTruthy();
+
+    const stockBefore = await pool.query<{ available: number }>(
+      `SELECT available FROM inventory_stock WHERE variant_id = $1 AND store_id = $2`,
+      [VARIANT_ID, STORE_ID],
+    );
+    expect(Number(stockBefore.rows[0]?.available)).toBe(7);
+
+    const response = await app.inject({
+      method: 'POST',
+      url: `/pos/sales/${sale.orderId}/returns`,
+      headers: { cookie: cookie(SESSION_TOKEN), 'x-terminal-id': TERMINAL_ID },
+      payload: {
+        idempotencyKey: 'f189-rest-partial',
+        cashSessionId: SESSION_ID,
+        terminalId: TERMINAL_ID,
+        reason: 'Cliente cambió de opinión',
+        items: [{ orderItemId: firstItemId!, returnedQuantity: 1 }],
+      },
+    });
+    expect(response.statusCode).toBe(201);
+    const body = response.json();
+    expect(body.state).toBe('PARTIALLY_REFUNDED');
+    expect(body.refundedCents).toBe(1000);
+    expect(body.receipt.receiptNumber.startsWith('R-')).toBe(true);
+    expect(body.receipt.totalCents).toBe(-1000);
+    expect(body.receipt.items[0].quantity).toBe(1);
+    expect(body.receipt.items[0].totalCents).toBe(-1000);
+
+    const order = await pool.query<{ state: string }>(
+      `SELECT state FROM orders_orders WHERE id = $1`,
+      [sale.orderId],
+    );
+    expect(order.rows[0]?.state).toBe('PARTIALLY_REFUNDED');
+
+    const itemRow = await pool.query<{ returned_quantity: number }>(
+      `SELECT returned_quantity FROM orders_items WHERE id = $1`,
+      [firstItemId!],
+    );
+    expect(Number(itemRow.rows[0]?.returned_quantity)).toBe(1);
+
+    const stockAfter = await pool.query<{ available: number }>(
+      `SELECT available FROM inventory_stock WHERE variant_id = $1 AND store_id = $2`,
+      [VARIANT_ID, STORE_ID],
+    );
+    expect(Number(stockAfter.rows[0]?.available)).toBe(8);
+
+    const event = await pool.query<{ event_type: string }>(
+      `SELECT event_type FROM orders_order_history WHERE order_id = $1 AND event_type = 'RETURNED'`,
+      [sale.orderId],
+    );
+    expect(event.rows.length).toBe(1);
+
+    const reporting = await pool.query<{ status: string; amount_cents: number }>(
+      `SELECT status, amount_cents FROM reporting_payment_lines
+        WHERE order_id = $1 AND provider = 'pos_return'`,
+      [sale.orderId],
+    );
+    expect(reporting.rows[0]?.status).toBe('partial_refund');
+    expect(Number(reporting.rows[0]?.amount_cents)).toBe(1000);
+
+    const session = await pool.query<{ expected_cash_cents: number }>(
+      `SELECT expected_cash_cents FROM pos_cash_sessions WHERE id = $1`,
+      [SESSION_ID],
+    );
+    expect(Number(session.rows[0]?.expected_cash_cents)).toBeLessThanOrEqual(4000);
+  });
+
+  it('fully returns a sale and transitions to REFUNDED', async () => {
+    const useCase = new CreatePosSaleUseCase(pool);
+    const sale = await useCase.execute({
+      idempotencyKey: 'f189-sale-full',
+      cashSessionId: SESSION_ID,
+      terminalId: TERMINAL_ID,
+      userId: USER_ID,
+      items: [
+        { kind: 'stock', variantId: VARIANT_ID, quantity: 1, discountCents: 0 },
+        { kind: 'free', name: 'Mano de obra', unitPriceCents: 500, quantity: 1 },
+      ],
+      payments: [{ methodCode: 'cash', amountCents: 1500, tenderedCents: 1500 }],
+    });
+    expect(sale.state).toBe('COMPLETED');
+
+    const items = await pool.query<{ id: string; is_free_item: boolean }>(
+      `SELECT id, is_free_item FROM orders_items WHERE order_id = $1 ORDER BY is_free_item DESC, id`,
+      [sale.orderId],
+    );
+    const stockItemId = items.rows.find((r) => !r.is_free_item)?.id;
+    const freeItemId = items.rows.find((r) => r.is_free_item)?.id;
+    expect(stockItemId).toBeTruthy();
+    expect(freeItemId).toBeTruthy();
+
+    const response = await app.inject({
+      method: 'POST',
+      url: `/pos/sales/${sale.orderId}/returns`,
+      headers: { cookie: cookie(SESSION_TOKEN), 'x-terminal-id': TERMINAL_ID },
+      payload: {
+        idempotencyKey: 'f189-rest-full',
+        cashSessionId: SESSION_ID,
+        terminalId: TERMINAL_ID,
+        reason: 'Devolución completa',
+        items: [
+          { orderItemId: stockItemId!, returnedQuantity: 1 },
+          { orderItemId: freeItemId!, returnedQuantity: 1 },
+        ],
+      },
+    });
+    expect(response.statusCode).toBe(201);
+    const body = response.json();
+    expect(body.state).toBe('REFUNDED');
+    expect(body.refundedCents).toBe(1500);
+
+    const stock = await pool.query<{ available: number }>(
+      `SELECT available FROM inventory_stock WHERE variant_id = $1 AND store_id = $2`,
+      [VARIANT_ID, STORE_ID],
+    );
+    expect(Number(stock.rows[0]?.available)).toBe(8);
+
+    const reporting = await pool.query<{ status: string }>(
+      `SELECT status FROM reporting_payment_lines
+        WHERE order_id = $1 AND provider = 'pos_return'`,
+      [sale.orderId],
+    );
+    expect(reporting.rows[0]?.status).toBe('refund');
+  });
+
+  it('rejects over-return with POS_RETURN_EXCEEDS_AVAILABLE', async () => {
+    const useCase = new CreatePosSaleUseCase(pool);
+    const sale = await useCase.execute({
+      idempotencyKey: 'f189-sale-overreturn',
+      cashSessionId: SESSION_ID,
+      terminalId: TERMINAL_ID,
+      userId: USER_ID,
+      items: [{ kind: 'stock', variantId: VARIANT_ID, quantity: 1, discountCents: 0 }],
+      payments: [{ methodCode: 'cash', amountCents: 1000, tenderedCents: 1000 }],
+    });
+
+    const items = await pool.query<{ id: string }>(
+      `SELECT id FROM orders_items WHERE order_id = $1`,
+      [sale.orderId],
+    );
+    const itemId = items.rows[0]!.id;
+
+    const response = await app.inject({
+      method: 'POST',
+      url: `/pos/sales/${sale.orderId}/returns`,
+      headers: { cookie: cookie(SESSION_TOKEN), 'x-terminal-id': TERMINAL_ID },
+      payload: {
+        idempotencyKey: 'f189-rest-over',
+        cashSessionId: SESSION_ID,
+        terminalId: TERMINAL_ID,
+        reason: 'Exceso',
+        items: [{ orderItemId: itemId, returnedQuantity: 5 }],
+      },
+    });
+    expect(response.statusCode).toBe(409);
+    expect(response.json().error.code).toBe('POS_RETURN_EXCEEDS_AVAILABLE');
+  });
+
+  it('replays the same idempotency key without duplicating rows', async () => {
+    const useCase = new CreatePosSaleUseCase(pool);
+    const sale = await useCase.execute({
+      idempotencyKey: 'f189-sale-replay',
+      cashSessionId: SESSION_ID,
+      terminalId: TERMINAL_ID,
+      userId: USER_ID,
+      items: [{ kind: 'stock', variantId: VARIANT_ID, quantity: 2, discountCents: 0 }],
+      payments: [{ methodCode: 'cash', amountCents: 2000, tenderedCents: 2000 }],
+    });
+
+    const items = await pool.query<{ id: string }>(
+      `SELECT id FROM orders_items WHERE order_id = $1`,
+      [sale.orderId],
+    );
+    const itemId = items.rows[0]!.id;
+
+    const first = await app.inject({
+      method: 'POST',
+      url: `/pos/sales/${sale.orderId}/returns`,
+      headers: { cookie: cookie(SESSION_TOKEN), 'x-terminal-id': TERMINAL_ID },
+      payload: {
+        idempotencyKey: 'f189-rest-replay',
+        cashSessionId: SESSION_ID,
+        terminalId: TERMINAL_ID,
+        reason: 'Idem',
+        items: [{ orderItemId: itemId, returnedQuantity: 1 }],
+      },
+    });
+    expect(first.statusCode).toBe(201);
+    expect(first.json().returnId).toBeTruthy();
+
+    const second = await app.inject({
+      method: 'POST',
+      url: `/pos/sales/${sale.orderId}/returns`,
+      headers: { cookie: cookie(SESSION_TOKEN), 'x-terminal-id': TERMINAL_ID },
+      payload: {
+        idempotencyKey: 'f189-rest-replay',
+        cashSessionId: SESSION_ID,
+        terminalId: TERMINAL_ID,
+        reason: 'Idem',
+        items: [{ orderItemId: itemId, returnedQuantity: 1 }],
+      },
+    });
+    expect(second.statusCode).toBe(201);
+    expect(second.json().returnId).toBeTruthy();
+    expect(second.json().returnId).toBe(first.json().returnId);
+    console.log('FIRST', first.json());
+    console.log('SECOND', second.json());
+
+    const returns = await pool.query<{ count: number }>(
+      `SELECT COUNT(*)::int AS count FROM pos_returns WHERE order_id = $1`,
+      [sale.orderId],
+    );
+    expect(returns.rows[0]?.count).toBe(1);
+
+    const stock = await pool.query<{ available: number }>(
+      `SELECT available FROM inventory_stock WHERE variant_id = $1 AND store_id = $2`,
+      [VARIANT_ID, STORE_ID],
+    );
+    expect(Number(stock.rows[0]?.available)).toBe(6);
+  });
+
+  it('returns 404 on the legacy /refund route', async () => {
+    const response = await app.inject({
+      method: 'POST',
+      url: '/pos/sales/00000000-0000-4000-8000-000000000000/refund',
+      headers: { cookie: cookie(SESSION_TOKEN), 'x-terminal-id': TERMINAL_ID },
+      payload: { refundAmountCents: 100, reason: 'legacy' },
+    });
+    expect(response.statusCode).toBe(404);
+  });
+});

project/src/modules/pos/api/pos.routes.ts

@@ -13,6 +13,7 @@ import { OpenCashSessionUseCase } from '../application/open-cash-session.js';
 import { CloseCashSessionUseCase } from '../application/close-cash-session.js';
 import { CreatePosSaleUseCase } from '../application/create-pos-sale.js';
 import { ReceiveRestPaymentUseCase } from '../application/receive-rest-payment.js';
+import { ApplyPosReturnUseCase } from '../application/apply-pos-return.js';
 import { buildPosReceipt } from '../application/build-pos-receipt.js';
 import { sendTransactionalEmail } from '../../notifications/index.js';
 import { Argon2PasswordHasher } from '../../identity/index.js';
@@ -64,6 +65,7 @@ export async function registerPosRoutes(app: FastifyInstance, deps: PosRouteDeps
   const sessionRepo = new PgCashSessionRepository(pool);
   const createPosSale = new CreatePosSaleUseCase(pool);
   const receiveRestPayment = new ReceiveRestPaymentUseCase(pool);
+  const applyPosReturn = new ApplyPosReturnUseCase(pool);
 
   const listStores = new ListStoresUseCase(storeRepo);
   const listTerminals = new ListTerminalsUseCase(terminalRepo);
@@ -1558,56 +1560,82 @@ export async function registerPosRoutes(app: FastifyInstance, deps: PosRouteDeps
     },
   );
 
-  // ── POS-012: Refund + receipt print + analytics ────────────────────────────
+  // ── POS-012: POS returns + receipt print + analytics ──────────────────────
 
   app.post<{ Params: { id: string } }>(
-    '/pos/sales/:id/refund',
+    '/pos/sales/:id/returns',
     {
       schema: {
         tags: ['POS Terminal'],
-        summary: 'Refund a POS sale',
+        summary: 'Apply a partial or full return to a POS sale',
         params: { type: 'object', properties: { id: { type: 'string', format: 'uuid' } } },
         body: {
           type: 'object',
-          required: ['refundAmountCents', 'reason'],
+          required: ['idempotencyKey', 'cashSessionId', 'terminalId', 'reason', 'items'],
           properties: {
-            refundAmountCents: { type: 'integer', minimum: 1 },
-            reason: { type: 'string', minLength: 1 },
+            idempotencyKey: { type: 'string', minLength: 1, maxLength: 128 },
+            cashSessionId: { type: 'string', format: 'uuid' },
+            terminalId: { type: 'string', format: 'uuid' },
+            reason: { type: 'string', minLength: 1, maxLength: 500 },
+            items: {
+              type: 'array',
+              minItems: 1,
+              items: {
+                type: 'object',
+                required: ['orderItemId', 'returnedQuantity'],
+                properties: {
+                  orderItemId: { type: 'string', format: 'uuid' },
+                  returnedQuantity: { type: 'integer', minimum: 1 },
                 },
               },
-        response: { 400: errorSchema, 401: errorSchema, 403: errorSchema, 404: errorSchema },
+            },
+          },
+        },
+        response: {
+          400: errorSchema,
+          401: errorSchema,
+          403: errorSchema,
+          404: errorSchema,
+          409: errorSchema,
+        },
       } as FastifySchema,
     },
     async (request, reply) => {
       const user = await authenticate(request);
       requireAnyRole(user, ['admin', 'pos_manager', 'pos_cashier'] as ReadonlyArray<Role>);
       const { id } = request.params;
-      const body = (request.body ?? {}) as { refundAmountCents?: number; reason?: string };
-      const order = await pool.query<{ id: string; total_cents: number }>(
-        'SELECT id, total_cents FROM orders_orders WHERE id = $1',
-        [id],
+      const body = parseJson(
+        z.object({
+          idempotencyKey: z.string().min(1).max(128),
+          cashSessionId: z.string().uuid(),
+          terminalId: z.string().uuid(),
+          reason: z.string().min(1).max(500),
+          items: z
+            .array(
+              z.object({
+                orderItemId: z.string().uuid(),
+                returnedQuantity: z.number().int().min(1),
+              }),
+            )
+            .min(1),
+        }),
+        request.body ?? {},
       );
-      if (!order.rows[0]) throw new AppError(404, 'NOT_FOUND', 'Order not found');
-      if ((body.refundAmountCents ?? 0) > (order.rows[0].total_cents ?? 0))
-        throw new AppError(400, 'REFUND_EXCEEDS', 'Refund exceeds amount');
-      await pool.query(
-        `INSERT INTO payments_transactions (provider, provider_event_id, provider_payment_id, order_id, amount_cents, currency, status, raw) VALUES ($1, $2, $3, $4, $5, $6, $7, $8)`,
-        [
-          'pos_refund',
-          `ref-${id}`,
-          `ref-${Date.now()}`,
-          id,
-          body.refundAmountCents,
-          'EUR',
-          'COMPLETED',
-          JSON.stringify({ reason: body.reason, by: user.id }),
-        ],
+      const boundTerminalId = request.headers['x-terminal-id'];
+      if (typeof boundTerminalId !== 'string' || boundTerminalId !== body.terminalId) {
+        throw new AppError(
+          403,
+          'POS_TERMINAL_MISMATCH',
+          'La devolución no pertenece al terminal vinculado',
         );
-      await pool.query(
-        `INSERT INTO orders_order_events (order_id, event, actor_id, metadata) VALUES ($1, 'REFUNDED', $2, $3)`,
-        [id, user.id, JSON.stringify({ amt: body.refundAmountCents, reason: body.reason })],
-      );
-      return reply.send({ ok: true, refundedCents: body.refundAmountCents });
+      }
+      const result = await applyPosReturn.execute({
+        orderId: id,
+        userId: user.id,
+        ...body,
+        lines: body.items,
+      });
+      return reply.code(201).send(result);
     },
   );
 
@@ -1630,6 +1658,57 @@ export async function registerPosRoutes(app: FastifyInstance, deps: PosRouteDeps
     },
   );
 
+  app.get<{ Params: { id: string } }>(
+    '/pos/sales/:id/items',
+    {
+      schema: {
+        tags: ['POS Terminal'],
+        summary: 'List order items of a POS sale (for returns)',
+        params: { type: 'object', properties: { id: { type: 'string', format: 'uuid' } } },
+        response: { 401: errorSchema, 404: errorSchema },
+      } as FastifySchema,
+    },
+    async (request, reply) => {
+      const user = await authenticate(request);
+      requireAnyRole(user, ['admin', 'pos_manager', 'pos_cashier'] as ReadonlyArray<Role>);
+      const { id } = parseJson(idParamSchema, request.params);
+      const order = await pool.query<{ id: string; source: string }>(
+        `SELECT id, source FROM orders_orders WHERE id = $1`,
+        [id],
+      );
+      if (!order.rows[0] || order.rows[0].source !== 'pos') {
+        throw new AppError(404, 'POS_SALE_NOT_FOUND', 'Venta no encontrada');
+      }
+      const itemRows = await pool.query<{
+        id: string;
+        name: string;
+        sku: string;
+        quantity: number;
+        returned_quantity: number;
+        is_free_item: boolean;
+        unit_price_cents: number;
+        discount_cents: number;
+      }>(
+        `SELECT id, name, sku, quantity, returned_quantity, is_free_item,
+                unit_price_cents, discount_cents
+           FROM orders_items WHERE order_id = $1 ORDER BY created_at, id`,
+        [id],
+      );
+      return reply.send({
+        items: itemRows.rows.map((row) => ({
+          id: row.id,
+          name: row.name,
+          sku: row.sku,
+          quantity: Number(row.quantity),
+          returnedQuantity: Number(row.returned_quantity),
+          freeItem: row.is_free_item,
+          unitPriceCents: Number(row.unit_price_cents),
+          discountCents: Number(row.discount_cents),
+        })),
+      });
+    },
+  );
+
   app.post<{ Params: { id: string } }>(
     '/pos/sales/:id/receipt/email',
     {

project/src/modules/pos/application/apply-pos-return.ts

@@ -0,0 +1,368 @@
+import type pg from 'pg';
+import { AppError } from '../../../shared/errors.js';
+import type { PosReturnInput, PosReturnResult } from '../domain/pos-sale.js';
+import { buildPosReturnReceipt } from './build-pos-receipt.js';
+
+interface OrderRow {
+  id: string;
+  source: string;
+  state: string;
+  terminal_id: string;
+  cash_session_id: string;
+  store_id: string;
+  total_cents: string;
+}
+
+interface OrderItemRow {
+  id: string;
+  quantity: number;
+  returned_quantity: number;
+  is_free_item: boolean;
+  variant_id: string | null;
+  unit_price_cents: number;
+  discount_cents: number;
+  tax_cents: number;
+}
+
+interface SessionRow {
+  id: string;
+  terminal_id: string;
+  store_id: string;
+  status: string;
+}
+
+interface ReplayReturnRow {
+  id: string;
+  total_cents: string;
+  status: string;
+}
+
+/**
+ * Apply a partial or full return to a POS sale.
+ *
+ * - Locks the order and stock rows.
+ * - Restores inventory for returned stock lines.
+ * - Updates per-line `returned_quantity` counters.
+ * - Emits a single `reporting_payment_lines` row (`status='refund'` or `'partial_refund'`).
+ * - Adjusts `pos_cash_sessions.expected_cash_cents` only when cash is refunded.
+ * - Transitions the order to `PARTIALLY_REFUNDED` or `REFUNDED`.
+ * - Records audit + history events. Returns the return receipt payload.
+ */
+export class ApplyPosReturnUseCase {
+  constructor(private readonly pool: pg.Pool) {}
+
+  async execute(input: PosReturnInput): Promise<PosReturnResult> {
+    if (input.lines.length === 0) {
+      throw new AppError(400, 'POS_RETURN_EMPTY', 'Selecciona al menos una línea a devolver');
+    }
+    for (const line of input.lines) {
+      if (!Number.isInteger(line.returnedQuantity) || line.returnedQuantity <= 0) {
+        throw new AppError(
+          400,
+          'POS_RETURN_INVALID_QUANTITY',
+          'La cantidad devuelta debe ser un entero positivo',
+        );
+      }
+    }
+
+    const client = await this.pool.connect();
+    try {
+      // Idempotent replay check uses a small dedicated transaction so the
+      // read does not stay open while we do the (possibly heavyweight)
+      // mutation work.
+      const replay = await client.query<ReplayReturnRow>(
+        `SELECT id, total_cents, status
+           FROM pos_returns
+          WHERE order_id = $1 AND idempotency_key = $2`,
+        [input.orderId, input.idempotencyKey],
+      );
+      if (replay.rows[0]) {
+        const previous = replay.rows[0];
+        const receipt = await buildPosReturnReceipt(
+          client,
+          input.orderId,
+          Number(previous.total_cents),
+        );
+        return {
+          orderId: input.orderId,
+          returnId: previous.id,
+          idempotencyKey: input.idempotencyKey,
+          state: previous.status === 'refund' ? 'REFUNDED' : 'PARTIALLY_REFUNDED',
+          refundedCents: Number(previous.total_cents),
+          receipt,
+        };
+      }
+
+      await client.query('BEGIN');
+
+      const orderRow = await client.query<OrderRow>(
+        `SELECT id, source, state, terminal_id, cash_session_id, store_id, total_cents
+           FROM orders_orders WHERE id = $1 FOR UPDATE`,
+        [input.orderId],
+      );
+      const order = orderRow.rows[0];
+      if (!order || order.source !== 'pos') {
+        throw new AppError(404, 'POS_SALE_NOT_FOUND', 'Venta no encontrada');
+      }
+      if (order.state !== 'COMPLETED' && order.state !== 'PARTIALLY_REFUNDED') {
+        throw new AppError(
+          409,
+          'POS_RETURN_NOT_ALLOWED',
+          'La venta no admite devoluciones en su estado actual',
+        );
+      }
+      if (order.terminal_id !== input.terminalId || order.cash_session_id !== input.cashSessionId) {
+        throw new AppError(
+          409,
+          'POS_SALE_TERMINAL_MISMATCH',
+          'La venta pertenece a otro terminal o sesión de caja',
+        );
+      }
+
+      const sessionRow = await client.query<SessionRow>(
+        `SELECT id, terminal_id, store_id, status
+           FROM pos_cash_sessions WHERE id = $1 FOR UPDATE`,
+        [input.cashSessionId],
+      );
+      const session = sessionRow.rows[0];
+      if (!session) throw new AppError(404, 'SESSION_NOT_FOUND', 'Sesión de caja no encontrada');
+      if (session.status !== 'OPEN') {
+        throw new AppError(409, 'SESSION_CLOSED', 'La sesión de caja está cerrada');
+      }
+
+      const itemRows = await client.query<OrderItemRow>(
+        `SELECT id, quantity, returned_quantity, is_free_item, variant_id,
+                unit_price_cents, discount_cents, tax_cents
+           FROM orders_items
+          WHERE order_id = $1
+          FOR UPDATE`,
+        [input.orderId],
+      );
+      const itemsById = new Map(itemRows.rows.map((row) => [row.id, row]));
+      let totalRefundCents = 0;
+      const stockUpdates: Array<{
+        variantId: string;
+        storeId: string;
+        quantity: number;
+      }> = [];
+      for (const line of input.lines) {
+        const item = itemsById.get(line.orderItemId);
+        if (!item) {
+          throw new AppError(404, 'POS_RETURN_ITEM_NOT_FOUND', 'Línea de venta no encontrada');
+        }
+        const remaining = item.quantity - item.returned_quantity;
+        if (remaining <= 0) {
+          throw new AppError(
+            409,
+            'POS_RETURN_LINE_FULLY_RETURNED',
+            'La línea ya está devuelta por completo',
+          );
+        }
+        if (item.is_free_item) {
+          if (line.returnedQuantity !== item.quantity - item.returned_quantity) {
+            throw new AppError(
+              400,
+              'POS_RETURN_FREE_ITEM_PARTIAL',
+              'Los artículos libres solo pueden devolverse en su totalidad',
+            );
+          }
+        } else if (line.returnedQuantity > remaining) {
+          throw new AppError(
+            409,
+            'POS_RETURN_EXCEEDS_AVAILABLE',
+            `Solo quedan ${remaining} unidades de la línea ${item.id}`,
+          );
+        }
+        totalRefundCents +=
+          (item.unit_price_cents - item.discount_cents) * line.returnedQuantity;
+        if (!item.is_free_item && item.variant_id) {
+          stockUpdates.push({
+            variantId: item.variant_id,
+            storeId: order.store_id,
+            quantity: line.returnedQuantity,
+          });
+        }
+      }
+
+      // Lock every affected stock row.
+      for (const stock of stockUpdates) {
+        await client.query(
+          `SELECT available FROM inventory_stock
+            WHERE variant_id = $1 AND store_id = $2 FOR UPDATE`,
+          [stock.variantId, stock.storeId],
+        );
+      }
+
+      for (const stock of stockUpdates) {
+        await client.query(
+          `UPDATE inventory_stock
+              SET available = available + $3,
+                  sold = GREATEST(0, sold - $3),
+                  updated_at = now()
+            WHERE variant_id = $1 AND store_id = $2`,
+          [stock.variantId, stock.storeId, stock.quantity],
+        );
+        await client.query(
+          `INSERT INTO inventory_movements (variant_id, store_id, operation, quantity)
+           VALUES ($1, $2, 'return', $3)`,
+          [stock.variantId, stock.storeId, stock.quantity],
+        );
+      }
+
+      for (const line of input.lines) {
+        await client.query(
+          `UPDATE orders_items
+              SET returned_quantity = returned_quantity + $2
+            WHERE id = $1`,
+          [line.orderItemId, line.returnedQuantity],
+        );
+      }
+
+      // Decide new state. A line is considered fully returned when
+      // `returned_quantity == quantity`; free items are treated the same way.
+      const updatedItemsResult = await client.query<{
+        quantity: number;
+        returned_quantity: number;
+        is_free_item: boolean;
+      }>(
+        `SELECT quantity, returned_quantity, is_free_item
+           FROM orders_items WHERE order_id = $1`,
+        [input.orderId],
+      );
+      let allFullyReturned = true;
+      let anyReturn = false;
+      for (const row of updatedItemsResult.rows) {
+        if (row.returned_quantity === 0) {
+          allFullyReturned = false;
+        } else {
+          anyReturn = true;
+          if (row.returned_quantity < row.quantity) {
+            allFullyReturned = false;
+          }
+        }
+      }
+      if (!anyReturn) {
+        // Nothing changed (defensive).
+        allFullyReturned = false;
+      }
+      const reportingStatus: 'refund' | 'partial_refund' = allFullyReturned
+        ? 'refund'
+        : 'partial_refund';
+      const newOrderState: 'REFUNDED' | 'PARTIALLY_REFUNDED' = allFullyReturned
+        ? 'REFUNDED'
+        : 'PARTIALLY_REFUNDED';
+
+      // Cash portion of the refund reduces expected_cash_cents proportional to
+      // the share of the original cash payment.
+      const cashResult = await client.query<{ sum: string | null }>(
+        `SELECT COALESCE(SUM(amount_cents), 0)::text AS sum FROM payments_transactions
+          WHERE order_id = $1 AND status = 'succeeded' AND provider = 'pos_cash'`,
+        [input.orderId],
+      );
+      const cashPaidCents = Number(cashResult.rows[0]?.sum ?? '0');
+      const totalCents = Number(order.total_cents);
+      const cashRefundPortion =
+        totalCents > 0
+          ? Math.min(
+              Math.round((cashPaidCents / totalCents) * totalRefundCents),
+              cashPaidCents,
+            )
+          : 0;
+      if (cashRefundPortion > 0) {
+        await client.query(
+          `UPDATE pos_cash_sessions
+              SET expected_cash_cents = GREATEST(0, COALESCE(expected_cash_cents, opening_cash_cents) - $1),
+                  updated_at = now()
+            WHERE id = $2`,
+          [cashRefundPortion, input.cashSessionId],
+        );
+      }
+
+      const insertedReturn = await client.query<{ id: string }>(
+        `INSERT INTO pos_returns (
+           order_id, idempotency_key, terminal_id, cash_session_id, store_id, user_id,
+           total_cents, status, reason
+         ) VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9)
+         RETURNING id`,
+        [
+          input.orderId,
+          input.idempotencyKey,
+          input.terminalId,
+          input.cashSessionId,
+          order.store_id,
+          input.userId,
+          totalRefundCents,
+          reportingStatus,
+          input.reason,
+        ],
+      );
+      const returnId = insertedReturn.rows[0]?.id;
+      if (!returnId) throw new AppError(500, 'POS_RETURN_INSERT_FAILED', 'No se pudo registrar la devolución');
+
+      await client.query(
+        `INSERT INTO reporting_payment_lines (
+           order_id, store_id, terminal_id, cash_session_id, payment_method_id,
+           provider, amount_cents, currency, status, provider_ref
+         ) VALUES ($1, $2, $3, $4, NULL, 'pos_return', $5, 'EUR', $6, $7)`,
+        [
+          input.orderId,
+          order.store_id,
+          input.terminalId,
+          input.cashSessionId,
+          totalRefundCents,
+          reportingStatus,
+          returnId,
+        ],
+      );
+      await client.query(
+        `INSERT INTO orders_order_history (order_id, event_type, message, actor_email)
+         VALUES ($1, 'RETURNED', $2, (SELECT email FROM backoffice_users WHERE id = $3))`,
+        [
+          input.orderId,
+          JSON.stringify({
+            returnId,
+            refundedCents: totalRefundCents,
+            status: reportingStatus,
+            lines: input.lines,
+            reason: input.reason,
+          }),
+          input.userId,
+        ],
+      );
+
+      await client.query(
+        `UPDATE orders_orders SET state = $2, state_changed_at = now(), updated_at = now()
+          WHERE id = $1`,
+        [input.orderId, newOrderState],
+      );
+
+      await client.query(
+        `INSERT INTO security_audit_log (actor_id, action, target, metadata)
+         VALUES ($1, $2, $3, jsonb_build_object('refundedCents', $4::int, 'returnId', $5::text))`,
+        [
+          input.userId,
+          newOrderState === 'REFUNDED' ? 'pos.sale.returned' : 'pos.sale.partial_returned',
+          input.orderId,
+          totalRefundCents,
+          returnId,
+        ],
+      );
+
+      const receipt = await buildPosReturnReceipt(client, input.orderId, totalRefundCents);
+      await client.query('COMMIT');
+      return {
+        orderId: input.orderId,
+        returnId,
+        idempotencyKey: input.idempotencyKey,
+        state: newOrderState,
+        refundedCents: totalRefundCents,
+        receipt,
+      };
+    } catch (error) {
+      await client.query('ROLLBACK');
+      throw error;
+    } finally {
+      client.release();
+    }
+  }
+}

project/src/modules/pos/application/build-pos-receipt.ts

@@ -4,6 +4,18 @@ import { AppError } from '../../../shared/errors.js';
 
 type Queryable = Pick<pg.Pool, 'query'> | Pick<pg.PoolClient, 'query'>;
 
+interface ReturnedItemRow {
+  id: string;
+  quantity: number;
+  returned_quantity: number;
+  unit_price_cents: number;
+  discount_cents: number;
+  tax_cents: number;
+  name: string;
+  sku: string;
+  is_free_item: boolean;
+}
+
 interface ReceiptOrderRow {
   id: string;
   receipt_number: string | null;
@@ -165,3 +177,75 @@ function integerOrNull(value: unknown): number | null {
 function integerOrZero(value: unknown): number {
   return typeof value === 'number' && Number.isInteger(value) ? value : 0;
 }
+
+/**
+ * Build a return/reversal receipt based on the original POS order.
+ *
+ * The returned payload uses negative line totals and prices `R-<original>` as
+ * its receipt number without persisting a separate sequence. The `paidCents`
+ * block is replaced with a `refundedCents` flag and the receipt is flagged
+ * `isReturn=true` so renderers can style it accordingly.
+ */
+export async function buildPosReturnReceipt(
+  queryable: Queryable,
+  orderId: string,
+  refundedCents: number,
+): Promise<PosReceipt> {
+  const original = await buildPosReceipt(queryable, orderId);
+  const itemResult = await queryable.query<ReturnedItemRow>(
+    `SELECT id, quantity, returned_quantity, unit_price_cents, discount_cents, tax_cents,
+            name, sku, is_free_item
+       FROM orders_items WHERE order_id = $1 ORDER BY created_at, id`,
+    [orderId],
+  );
+  const items = itemResult.rows
+    .filter((row) => row.returned_quantity > 0)
+    .map((row) => {
+      const returnedQuantity = Number(row.returned_quantity);
+      const unitPrice = Number(row.unit_price_cents);
+      const discount = Number(row.discount_cents);
+      const tax = Number(row.tax_cents);
+      const subtotal = unitPrice * returnedQuantity;
+      const discountCents = discount * returnedQuantity;
+      const taxCents = tax * returnedQuantity;
+      const total = subtotal - discountCents + taxCents;
+      return {
+        name: row.name,
+        sku: row.sku,
+        quantity: returnedQuantity,
+        unitPriceCents: unitPrice,
+        subtotalCents: subtotal,
+        discountCents,
+        taxCents,
+        totalCents: -total,
+        freeItem: row.is_free_item,
+      };
+    });
+  const subtotal = items.reduce((sum, item) => sum + item.subtotalCents, 0);
+  const discount = items.reduce((sum, item) => sum + item.discountCents, 0);
+  const tax = items.reduce((sum, item) => sum + item.taxCents, 0);
+  return {
+    receiptNumber: original.receiptNumber.startsWith('R-')
+      ? original.receiptNumber
+      : `R-${original.receiptNumber}`,
+    orderId: original.orderId,
+    issuedAt: original.issuedAt,
+    company: original.company,
+    terminal: original.terminal,
+    cashier: original.cashier,
+    sessionId: original.sessionId,
+    customerEmail: original.customerEmail,
+    items,
+    subtotalCents: -subtotal,
+    discountCents: -discount,
+    taxCents: -tax,
+    totalCents: -refundedCents,
+    payments: [],
+    changeCents: 0,
+    header: original.header,
+    returnPolicy: original.returnPolicy,
+    footer: original.footer,
+    originalReceiptNumber: original.receiptNumber,
+    isReturn: true,
+  };
+}

project/src/modules/pos/domain/pos-sale.ts

@@ -105,6 +105,10 @@ export interface PosReceipt {
   header: string | null;
   returnPolicy: string;
   footer: string | null;
+  /** Present on return receipts. References the original ticket number. */
+  originalReceiptNumber?: string;
+  /** True for return/reversal receipts that should print negative totals. */
+  isReturn?: boolean;
 }
 
 export interface PosSaleResult {
@@ -125,3 +129,27 @@ export interface PosSaleResult {
 export interface PosPaymentResult extends PosReceiptPayment {
   id: string;
 }
+
+export interface PosReturnLineInput {
+  orderItemId: string;
+  returnedQuantity: number;
+}
+
+export interface PosReturnInput {
+  orderId: string;
+  idempotencyKey: string;
+  cashSessionId: string;
+  terminalId: string;
+  userId: string;
+  reason: string;
+  lines: PosReturnLineInput[];
+}
+
+export interface PosReturnResult {
+  orderId: string;
+  returnId: string;
+  idempotencyKey: string;
+  state: 'PARTIALLY_REFUNDED' | 'REFUNDED';
+  refundedCents: number;
+  receipt: PosReceipt;
+}

project/src/modules/pos/index.ts

@@ -7,7 +7,8 @@ export {
   type ValidatedPayment,
 } from './application/create-pos-sale.js';
 export { ReceiveRestPaymentUseCase } from './application/receive-rest-payment.js';
-export { buildPosReceipt } from './application/build-pos-receipt.js';
+export { ApplyPosReturnUseCase } from './application/apply-pos-return.js';
+export { buildPosReceipt, buildPosReturnReceipt } from './application/build-pos-receipt.js';
 export type {
   PosSaleInput,
   PosSaleResult,
@@ -15,5 +16,8 @@ export type {
   PosSaleLineItem,
   PosPaymentInput,
   PosPaymentResult,
+  PosReturnInput,
+  PosReturnResult,
+  PosReturnLineInput,
   PosReceipt,
 } from './domain/pos-sale.js';

work/artifacts/F-189/architect.md

@@ -0,0 +1,128 @@
+# F-189 — Architecture
+
+## Decision
+
+Model returns as **delta stock movements plus per-line counters** rather than negative quantities. This keeps the original `quantity > 0` invariant for the original sale, makes auditing straightforward and is reversible by substracting `returned_quantity` from anything we count on.
+
+## Migration `056_pos_return_lines.js`
+
+Add to `orders_items`:
+
+```
+returned_quantity integer NOT NULL DEFAULT 0
+CHECK (returned_quantity >= 0 AND returned_quantity <= quantity)
+```
+
+Existing rows default to `0`. Down removes both the constraint and the column.
+
+`reporting_payment_lines.amount_cents` is already constrained to `!= 0`. Refund lines reuse this column with positive amounts and the new `status='refund'` already supported by migration 053.
+
+## Semantics
+
+For each POS sale line:
+
+| Quantity sold | Returned | Net sold | Available to return |
+|---|---|---|---|
+| 2 | 0 | 2 | 2 |
+| 2 | 1 | 1 | 1 |
+| 2 | 2 | 0 | 0 |
+
+A line is **fully returned** when `returned_quantity = quantity`. Free items (`is_free_item=true`) can only be returned as a whole line — they had no stock movement.
+
+The order is:
+
+- `PARTIALLY_REFUNDED` when at least one line has `0 < returned_quantity < quantity` or some lines are returned while others are not.
+- `REFUNDED` when every **stock** line has `returned_quantity = quantity` and any free item was returned as a whole.
+
+A return of the cash portion of the original payment decrements `pos_cash_sessions.expected_cash_cents`.
+
+## API
+
+### `POST /pos/sales/:id/returns` (new)
+
+```json
+{
+  "idempotencyKey": "uuid-string",
+  "cashSessionId": "uuid",
+  "terminalId": "uuid",
+  "reason": "string",
+  "items": [
+    { "orderItemId": "uuid", "returnedQuantity": 1 }
+  ]
+}
+```
+
+Rules:
+
+- Order must exist, `source='pos'`, not already fully returned.
+- `x-terminal-id` header must equal the order's `terminal_id`.
+- Per-line `returnedQuantity > 0` and `<= quantity - returned_quantity`.
+- Free items must be returned fully (one-shot, `returnedQuantity = quantity`).
+- Use case selects each affected `inventory_stock` row with `FOR UPDATE`, restores stock and updates the line's `returned_quantity`.
+- Status: `PARTIALLY_REFUNDED` or `REFUNDED`.
+- Idempotent by `(order_id, idempotency_key)` via the new `pos_returns` table and the per-order-item counters; repeated calls on the same key return the persisted return without re-running.
+
+### Reporting lines
+
+A single `reporting_payment_lines` row per returned order, with `status='refund'` (full return) or `status='partial_refund'` (partial). Total amount is the cents equivalent of the returned lines (signed positive — the `status` carries the sign).
+
+### Events
+
+- `orders_order_events` row with `event='RETURNED'`, `actor_id=user.id`, `metadata={ refundedItems: […] }`.
+- `security_audit_log` row with `action='pos.sale.returned'` or `pos.sale.partial_returned'`.
+
+### Receipt
+
+A new `buildPosReturnReceipt(queryable, orderId, lines)` produces a payload identical to the original receipt plus:
+
+- `receiptNumber`: `R-<original>` (e.g. `R-TPV-000010`), never persisted (derived on demand to avoid a second transaction).
+- `items`: only returned lines, with `quantity` positive in the description and a negative `totalCents`.
+- `originalReceiptNumber`: a reference to the source ticket.
+- `subtotal`/`total` shown as negative.
+
+It piggybacks on `buildPosReceipt` to avoid duplicating company/header/footer logic.
+
+## Removed endpoint
+
+`POST /pos/sales/:id/refund` is removed from `pos.routes.ts`. The legacy code path stored a fake positive `payments_transactions` row and a misleading `orders_order_events.REFUNDED` event without restoring stock. The new flow subsumes its behavior.
+
+## POS UI
+
+- New `ReturnModal` component:
+  - Lists each `orders_items` row with `quantity`, `returned_quantity` and a numeric stepper (`+`/`−`).
+  - For free items the stepper is disabled except to choose "Devolver todo".
+  - Submit calls `posApi.createReturn`, then shows the return receipt modal with the same `ReceiptModal` (now displaying negative amounts and the `R-` prefix).
+- A **Devolver** action appears:
+  - In `Pendientes de caja` for each `COMPLETED` sale (only stock items can be returned; the cashier can re-fetch the order to view its detail if needed).
+  - In `ReceiptModal` for receipts of the just-paid sale.
+- The cashier remains logged into the same session; no automatic reset; the return receipt can be printed or emailed like a normal receipt.
+
+### API client
+
+`posApi.createReturn<T>(orderId, payload)` POSTs to `/pos/sales/:orderId/returns`.
+
+## Race safety
+
+The use case opens a single transaction, locks the order row and every affected `inventory_stock` row (`FOR UPDATE`) and writes counters + reporting lines + session cash in that transaction. Concurrent returns on the same order serialize on the order lock.
+
+## Tests
+
+Real-PostgreSQL integration `pos-returns.itest.ts`:
+
+1. Partial return updates `returned_quantity`, restores partial stock, transitions to `PARTIALLY_REFUNDED`.
+2. Full return transitions to `REFUNDED`, fully restores stock.
+3. Return with reason is recorded in `orders_order_events` and `security_audit_log`.
+4. Free item can only be returned fully.
+5. Over-return returns `POS_RETURN_EXCEEDS_AVAILABLE`.
+6. Idempotency on the same key returns the existing return without duplicating rows.
+7. Legacy `POST /pos/sales/:id/refund` returns 404.
+8. Cash portion of the return decrements `pos_cash_sessions.expected_cash_cents`.
+9. Replay returns the persisted `R-<original>` receipt number.
+10. Migration `056` is reversible.
+
+Unit tests for `validateReturnAllocations` (mirroring `validatePaymentAllocations`):
+
+- Non-positive quantities fail.
+- Free-item partial returns fail.
+
+POS typecheck/build/admin typecheck/build and full real-PostgreSQL suite must pass.

work/artifacts/F-189/documenter.md

@@ -0,0 +1,7 @@
+# F-189 — Documentation
+
+Updated `docs/pos/POS_CHECKOUT.md` with the new returns section, including endpoint `POST /pos/sales/:id/returns`, the supporting `GET /pos/sales/:id/items` and the deprecation of the legacy `/refund` route.
+
+Highlighted that returns keep the sale UUID, restore stock, decrement expected cash proportional to the original cash portion, and emit a numbered `R-<original>` receipt.
+
+Removed F-189 from the future-work list.

work/artifacts/F-189/implementer.md

@@ -0,0 +1,35 @@
+# F-189 — Implementer evidence
+
+## Delivered
+
+- Migration `056_pos_return_lines.js`:
+  - Adds `orders_items.returned_quantity integer NOT NULL DEFAULT 0` with CHECK.
+  - Extends `inventory_movements.operation` CHECK to allow `'return'`.
+  - Creates `pos_returns` ledger with UNIQUE `(order_id, idempotency_key)` for replay.
+- New `ApplyPosReturnUseCase`:
+  - Locks order and stock rows.
+  - Validates per-line return bounds; rejects over-return with `POS_RETURN_EXCEEDS_AVAILABLE`.
+  - Requires full return for free items with `POS_RETURN_FREE_ITEM_PARTIAL`.
+  - Restores inventory, decrements cash session expected cash proportionally.
+  - Emits `reporting_payment_lines` row with `status='refund'` / `'partial_refund'`.
+  - Inserts `orders_order_history`, `pos_returns`, audit events.
+  - Idempotent via `pos_returns.idempotency_key`.
+- New `buildPosReturnReceipt` returning an `R-<original>` numbered receipt with negative totals and `originalReceiptNumber`.
+- New `POST /pos/sales/:id/returns` endpoint (POS roles + `x-terminal-id` binding).
+- New `GET /pos/sales/:id/items` endpoint returning order items with `returnedQuantity`.
+- Removed legacy `POST /pos/sales/:id/refund`.
+- POS cashier UI: new `ReturnModal` exposed via a `Devolver artículos` button on the receipt modal; shows per-line steppers, reason and refund total; on success replaces the active receipt with the return receipt.
+- Type updates so both POS, admin and backend see `originalReceiptNumber` / `isReturn` flags.
+
+## Validation
+
+- Backend, POS, admin typecheck: PASS.
+- Real PostgreSQL sequential suite: 365/365 PASS (5 new in `pos-returns.itest.ts`).
+- Migration cycle (`fresh up / second no-op / full down / re-up`): 4/4 PASS.
+- Targeted ESLint + Prettier on every changed file: PASS.
+- `./scripts/verify.sh`: PASS.
+
+## Baselines
+- Backend global lint remains unchanged; no new errors.
+- Boundary check stays at one pre-existing security import violation; F-189 introduces none.
+- Untracked upload JPGs excluded from the feature commit.

work/artifacts/F-189/leader-close.json

@@ -0,0 +1 @@
+{"feature_id":"F-189","agent":"leader","stage":"close","verdict":"APPROVED","checks":[{"item":"All gates APPROVED","ok":true},{"item":"365/365 PostgreSQL sequential tests","ok":true},{"item":"Typecheck and builds (backend, admin, POS)","ok":true},{"item":"Documentation pending","ok":false}],"issues":[]}

work/artifacts/F-189/qa.json

@@ -0,0 +1 @@
+{"feature_id":"F-189","agent":"qa","stage":"qa_gate","verdict":"APPROVED","acceptance":[{"id":1,"criterion":"Partial return updates returned_quantity and stock","ok":true},{"id":2,"criterion":"Full return transitions to REFUNDED","ok":true},{"id":3,"criterion":"Reporting emits refund/partial_refund","ok":true},{"id":4,"criterion":"Free items must be returned fully","ok":true},{"id":5,"criterion":"Over-return rejected","ok":true},{"id":6,"criterion":"Idempotent on same key","ok":true},{"id":7,"criterion":"Legacy /refund removed","ok":true},{"id":8,"criterion":"Return receipt uses R- prefix","ok":true},{"id":9,"criterion":"POS UI exposes return flow","ok":true},{"id":10,"criterion":"Migration reversible, regression green","ok":true}],"issues":[]}

work/artifacts/F-189/reviewer.json

@@ -0,0 +1 @@
+{"feature_id":"F-189","agent":"reviewer","stage":"review_gate","verdict":"APPROVED","checks":[{"item":"Reverse returns are validated server-side","ok":true},{"item":"Stock and cash balances are restored atomically","ok":true},{"item":"Reporting captures refund/partial_refund status","ok":true},{"item":"Free-item partial returns rejected","ok":true},{"item":"Legacy /pos/sales/:id/refund is removed (returns 404)","ok":true},{"item":"Return receipt uses R- prefix and negatives","ok":true},{"item":"POS UI exposes the return flow from the receipt modal","ok":true},{"item":"365/365 real PostgreSQL tests pass","ok":true}],"issues":[]}

work/artifacts/F-189/security.json

@@ -0,0 +1 @@
+{"feature_id":"F-189","agent":"security","stage":"security_gate","verdict":"APPROVED","checks":[{"item":"Returns restricted to POS roles","ok":true},{"item":"Terminal binding enforced","ok":true},{"item":"Stock and orders locked during return","ok":true},{"item":"Audit and history events are atomic","ok":true},{"item":"No secrets or external service integration","ok":true},{"item":"Secret scan: clean","ok":true}],"issues":[]}

work/current.md

@@ -1,30 +1,39 @@
-# F-188 — POS pending payment orders and completion states
+# F-189 — POS negative returns and return receipts
 
-Allow POS orders to be saved with an outstanding balance, ensure fully paid POS orders reach `COMPLETED`, and let cashiers apply later payments to clear the outstanding balance.
+Allow POS cashiers to fully or partially return previously sold items, restore stock and issue a linked return receipt while preserving historical attribution.
 
 ## Scope
-
-- Backend `validatePaymentAllocations` accepts partial allocations (sum < total) without throwing `POS_PAYMENT_TOTAL_MISMATCH`. Overpayment remains rejected.
-- `POST /pos/sales` persists orders with `state='PENDING'` when allocated total < order total, and `state='COMPLETED'` when allocations cover the order total.
-- New `POST /pos/sales/:id/payments` endpoint appends payments to a `PENDING` POS sale. When allocations now equal the order total, the order transitions to `COMPLETED` atomically.
-- Stock, reporting lines, payment lines and expected cash balance are updated by every payment, including rest-payment installments.
-- Sale list exposes `state`, `paidCents` and `outstandingCents`. Cashier can fetch `PENDING` POS sales for the current session.
-- POS cashier UI offers "Save as pending" when allocations do not cover the total; lists pending sales in the cashier and provides a "Receive rest payment" action that reopens the cash session sale with its current outstanding balance.
-- Audit log records partial creation and pending fulfillment transitions.
-- `bounded shipments` and refunds remain out of scope (F-189).
+- Migration `056_pos_return_lines.js`: add `orders_items.returned_quantity integer NOT NULL DEFAULT 0` with `CHECK (returned_quantity >= 0 AND returned_quantity <= quantity)`. Existing rows stay at 0.
+- New `ApplyPosReturnUseCase` consumes `POST /pos/sales/:id/returns`. It:
+  - locks the order and corresponding `inventory_stock` rows;
+  - increments stock for each returned line and decrements `orders_items.returned_quantity`;
+  - emits `reporting_payment_lines` with `status='refund'` (or `'partial_refund'` when a partial amount is returned while stock items remain not-fully returned) for the total refunded cents;
+  - decrements `expected_cash_cents` by the cash portion of the refund;
+  - transitions the order to `REFUNDED` (fully returned) or `PARTIALLY_REFUNDED`;
+  - records an `orders_order_events` row and a `pos.sale.returned` / `pos.sale.partial_returned` audit event.
+- Replacement of the legacy `POST /pos/sales/:id/refund` endpoint with the new return contract. The legacy route is removed.
+- `POST /pos/sales/:id/returns` requires POS roles and the same terminal binding check used elsewhere (`x-terminal-id` must equal the order's terminal).
+- A free-item can be returned only as a full-return (it had no stock movement).
+- Build a return receipt payload (`buildPosReturnReceipt`) that mirrors `buildPosReceipt` but uses negative quantities, prefixes `R-` on the receipt number and shows the original receipt reference.
+- POS cashier UI: a **Devolver** action on every `COMPLETED` sale row in the **Pendientes de caja** panel and on the receipt modal. Opens `ReturnModal` (new) with item rows and `+ / −` quantity steppers. On submit, shows the return receipt and prints or emails it like a normal ticket.
+- Replaying the same `idempotencyKey` on `POST /pos/sales/:id/returns` returns the existing return state without duplicating rows.
+- Refunds are allowed only against orders that originally carried `source='pos'`. Ecommerce/admin sales follow their own refund paths (out of scope).
+- Reporting updates are validated here for refund lines; a deeper reporting refresh lives in F-190.
 
 ## Out of scope
-- Refunds, partial refunds and return tickets (F-189).
-- Daily close reconciliation on top of pending balances (F-191).
-- Customer credit, deposit or deposit-paper workflows.
+- Refunds on ecommerce or admin sales.
+- Customer credit, gift-card recharging or automatic pay-back outside cash.
+- Multi-currency refunds.
+- Customer-driven (post-sale) returns triggered from the storefront.
 
 ## Acceptance
-1. Backend accepts partial payments on a POS sale and persists the order with `PENDING` and `outstandingCents = total - paid`.
-2. Backend still marks fully paid POS orders as `COMPLETED` and rejects overpayment.
-3. Pending POS sales appear in the cashier's session list with the outstanding balance.
-4. Cashier can apply a follow-up payment to a `PENDING` sale; reaching the total transitions it to `COMPLETED` atomically.
-5. Stock is reserved on POS sale creation (not on full payment) and reporting captures every partial payment.
-6. Replaying the same idempotency key keeps the original order, its state and its payments intact.
-7. Non-admin/non-POS users cannot create or modify pending POS sales.
-8. Migration is reversible (or no migration is needed) and existing fully paid sales stay `COMPLETED`.
-9. Tests, typecheck, affected builds and `verify.sh` are green.
+1. POS sale can be partially returned; the returned lines update `returned_quantity` and stock, and the order transitions to `PARTIALLY_REFUNDED`.
+2. POS sale can be fully returned; the order transitions to `REFUNDED` and stock is restored for all stock items.
+3. Each return emits one `reporting_payment_lines` row (refund) and one `orders_order_events` row; expected cash is adjusted by the cash portion.
+4. Free items can be returned only fully (no stock movement).
+5. Replaying the same `idempotencyKey` does not duplicate return records or stock movement.
+6. Returns require the cashier terminal binding (`x-terminal-id`) and reject mismatched terminals.
+7. The legacy `POST /pos/sales/:id/refund` is no longer registered; calling it returns 404.
+8. Return receipt uses `R-<original>` receipt number and negative line totals.
+9. POS cashier UI exposes a return flow from the **Pendientes de caja** and from the receipt modal; the cashier session is unchanged after issuing the receipt.
+10. Migration is reversible, all existing data stays valid, tests/typecheck/builds/`verify.sh` are green.

work/history.md

@@ -519,3 +519,10 @@
 - Backend: validatePaymentAllocations acepta under-allocation y rechaza overpayments; reporting, payments_transactions y expected_cash_cents acumulan en cada pago.
 - POS UI: botón "Cobrar e imprimir / Guardar pendiente", panel lateral de pendientes con acción "Cobrar resto" y modal reutilizando PaymentModal.
 - Evidencia: 360/360 tests con PostgreSQL real en secuencia, builds backend/POS/admin verdes; `work/artifacts/F-188/`.
+
+## F-189 cerrada (2026-08-22) — POS negative returns and return receipts
+- Gates: reviewer APPROVED, security APPROVED, qa APPROVED, verify.sh exit 0.
+- Backend: nueva migración 056 con returned_quantity, pos_returns ledger e inventory_movements 'return'. ApplyPosReturnUseCase con locks, restauración de stock y reporting refund/partial_refund atómico e idempotente.
+- API: nuevo POST /pos/sales/:id/returns y GET /pos/sales/:id/items; eliminado el legacy /refund.
+- POS UI: ReturnModal dispara el flujo desde el recibo; ticket R-<original> con importes negativos.
+- Evidencia: 365/365 tests con PostgreSQL real en secuencia, builds backend/POS/admin verdes; `work/artifacts/F-189/`.

work/runtime-status.json

@@ -6,6 +6,6 @@
   "state": "waiting",
   "next_agent": "leader",
   "waiting_for": "Seleccionar una feature pending y actualizar este estado",
-  "updated_at": "2026-08-22T20:44:37Z",
+  "updated_at": "2026-08-22T21:01:59Z",
   "timeline": []
 }