Add AssetItem.cost/costCurrency/externalPoNumber, make import upsert-capable

Three new fields: cost (Decimal, not Float -- exact money math),
costCurrency (free text), externalPoNumber (free text PO number from an
external system, distinct from purchaseOrderId which is a real FK into
this apps own PurchaseOrder table -- external exports PO numbers are
messy free text with nothing to link to here).

importAssetItems() now upserts: a row matching an existing assetTag or
serialNumber updates that row instead of erroring on the uniqueness
conflict. Needed to backfill cost/PO onto the 613 already-imported rows
without recreating them, and sets this up for future re-syncs when the
company re-exports their ITAM report. Update only touches fields the row
actually carries a value for (blank cell = no change, not clear) --
warrantyEndDate is the one field NOT auto-recomputed from warrantyMonths
on update (unlike create), so a manually-corrected date survives a
re-sync. Placeholder junk (Not available/Pending/N/A/etc, case
-insensitive) in PO number/cost/currency cells is treated as absent.

Re-ran the full 613-row import after this: 0 created, 613 updated, 0
errors -- backfilled cost onto the 8 rows that had one and PO number onto
the 2 that had a real (non-placeholder) value, verified against the
source file.

Hand-written migration, no Vitest coverage -- same deviation as the rest
of this branch, see CLAUDE.md. tsc/lint clean.

CLAUDE.md

@@ -103,6 +103,12 @@ Backend CRUD xong cho toàn bộ entity chốt tới nay: `Request` (chỉ state
   - Migration viết tay: `20260824081044_add_asset_item_asset_tag`, `20260824082411_asset_item_purchase_date_nullable`.
   **Kết quả import thật:** 613/613 tạo thành công, 0 lỗi (khớp 100% với file gốc: 542 assigned + 71 in_stock). Trước khi import phải seed thủ công 14 `AssetCategory` mới + 135 `AssetModel` mới (script `seed-models.ts`, tự viết, chạy 1 lần qua tsx rồi xoá — không phải feature UI, vì import `AssetItem` cố tình KHÔNG tự tạo model, xem comment `importAssetItems()`). 6 asset thiếu ngày mua: `DANCONT014, DANCONT017, DANCONT018, DANCONT020, DANCONT021, DANCONT023` — cần bổ sung tay sau. **Phạm vi đợt này CHƯA làm:** Cost/Cost currency, PO number (text tự do, không map được vào `purchaseOrderId` UUID hiện tại), gán nhân viên thật (`User Assigned` → cần entity `Assignment` riêng, chưa đụng tới) — để đợt sau.
 - **Backfill Employee + Assignment từ dữ liệu thật (2026-08-24):** tiếp theo đợt import 613 AssetItem — trích 95 Employee khác nhau (từ cột "User Assigned", 2 người không có Department trong file gốc do là "(Other)"/"(Freelance)" → gán tạm "Unknown") + 384 Assignment (asset ↔ nhân viên, dùng ngày "Assigned Date" thật của file làm `assignedAt` lịch sử). **Quan trọng: KHÔNG dùng `createAssignment()` có sẵn** — hàm đó cho luồng nghiệp vụ SỐNG (cấp phát mới từ kho, bắt buộc AssetItem đang `in_stock`, tự chuyển sang `assigned`, không cho set `assignedAt` tay). Asset import đã có sẵn `status=assigned` đúng thực tế rồi nên gọi hàm đó sẽ bị từ chối hết — đây là backfill lịch sử, phải ghi thẳng qua Prisma (`prisma.assignment.create()` trực tiếp, script `seed-assignments.ts`, chạy 1 lần qua tsx rồi xoá, không phải feature UI/lib mới). Kết quả: 95 employee + 384 assignment, 0 lỗi, khớp 100% (kiểm tra chéo DANLAP001 → Duc Luu Minh, đúng phòng ban + ngày gán). 158 asset `status=assigned` không có Assignment — đúng thực tế (thiết bị dùng chung, file gốc không gán riêng ai). **Chưa làm:** Cost, PO number, Job/Manager/Email của Employee (schema `Employee` hiện chỉ có name+department, chưa mở rộng thêm field từ file gốc).
+- **`AssetItem.cost`/`costCurrency`/`externalPoNumber` + import upsert (2026-08-24):** thêm 3 field: `cost` (Decimal(14,2), không dùng Float để tránh sai số làm tròn), `costCurrency` (text tự do vd "VND"/"CNY"), `externalPoNumber` (text tự do — **khác** `purchaseOrderId` vốn là UUID FK thật vào bảng `PurchaseOrder`; PO number từ export ngoài thường là text rác không map được vào entity thật). CSV import/export cập nhật theo (`parseAssetItemsCsv`/`exportAssetItemsCsv`), cột `po number` tách biệt alias với `purchase order id` để không đụng nhau.
+  - **`importAssetItems()` giờ hỗ trợ upsert** (2026-08-24, thay đổi hành vi quan trọng): dòng có `assetTag`/`serialNumber` đã tồn tại sẽ **UPDATE** thay vì báo lỗi trùng như trước — cần thiết để backfill cost/PO lên 613 asset đã import trước đó, và hữu ích cho lần công ty xuất file ITAM mới sau này (re-sync định kỳ, không phải one-off). Update chỉ đụng field nào dòng CSV **có giá trị** (ô trống = không đổi, không phải xoá) — riêng `warrantyEndDate` chỉ update khi dòng có giá trị rõ ràng, KHÔNG tự tính lại từ `warrantyMonths` như nhánh CREATE (tránh ghi đè warranty đã sửa tay). Kết quả trả về thêm field `updated` bên cạnh `created`/`errors`.
+  - Dữ liệu rác dạng "Not available"/"Pending"/"N/A"/"None"/"-" (case-insensitive) ở cột PO number/cost/cost currency được coi là rỗng (hàm `cleanImportText()`/`parseImportCost()`), không lưu literal text rác vào DB.
+  Migration viết tay: `20260824090149_add_asset_item_cost_po`.
+  **Kết quả backfill thật:** chạy lại đúng file CSV 613 dòng (giờ có thêm 3 cột) → **0 tạo mới, 613 update, 0 lỗi** (đúng — không tạo trùng). 8/613 asset có cost thật (khớp 100% giá trị gốc, kiểm tra chéo), 2/613 có PO number thật, còn lại đúng là rác đã lọc.
+  **Việc còn dở, ý tưởng đã thống nhất với user (chưa làm):** tách `Department` thành entity riêng (như `Area`/`Vendor`), cho cả `Employee` và `AssetItem` cùng tham chiếu qua FK thay vì mỗi bên giữ 1 chuỗi text tự do — giúp asset dùng chung (không gán ai) vẫn gắn được department, và tránh lệch chính tả giữa 2 bảng.
 - **CI (2026-08-20):** Gitea Actions, workflow `.gitea/workflows/ci.yml` — chạy `npm ci` + `npx prisma generate` + `npx tsc --noEmit` + `npm run lint` + `npm test` (Postgres service container) trên mọi push/PR. Cần runner tự host (`act_runner`) đã đăng ký với instance Gitea `git.toanhoang.work` — xem chi tiết setup ở `/opt/homelab/gitea/CLAUDE.md` (ngoài repo này) nếu cần thêm runner. **Chưa có auto-deploy** — deploy production vẫn làm tay trên `appsrv01`: `docker compose up -d --build app` rồi `docker exec asset-license-mgmt-app npm run db:migrate` (thứ tự bắt buộc: build trước, migrate sau khi container mới đã chạy).
 
 ## Việc còn dở

prisma/migrations/20260824090149_add_asset_item_cost_po/migration.sql

@@ -0,0 +1,4 @@
+-- Hand-written (same deviation as other 2026-08-2x migrations -- see CLAUDE.md).
+ALTER TABLE "asset_items" ADD COLUMN "cost" DECIMAL(14,2);
+ALTER TABLE "asset_items" ADD COLUMN "cost_currency" TEXT;
+ALTER TABLE "asset_items" ADD COLUMN "external_po_number" TEXT;

prisma/schema.prisma

@@ -139,8 +139,23 @@ model AssetItem {
   purchaseDate       DateTime?            @map("purchase_date") @db.Date
   warrantyEndDate    DateTime?            @map("warranty_end_date") @db.Date
   status             AssetItemStatus      @default(in_stock)
+  // Purchase cost, in `costCurrency`'s units -- added 2026-08-24 alongside
+  // externalPoNumber for the real ITAM export (very sparse there: 8/613
+  // rows had a nonzero cost). Decimal, not Float, for exact money math (no
+  // binary-float rounding drift) -- Decimal(14,2) comfortably covers VND
+  // amounts in the millions with room to spare.
+  cost               Decimal?             @db.Decimal(14, 2)
+  costCurrency       String?              @map("cost_currency")
   purchaseOrderId    String?              @map("purchase_order_id") @db.Uuid
   purchaseOrder      PurchaseOrder?       @relation(fields: [purchaseOrderId], references: [id])
+  // Free-text PO number from an external system (e.g. the real ITAM
+  // export's "PO number" column) -- deliberately NOT the same thing as
+  // purchaseOrderId above, which is a real FK into this app's own
+  // PurchaseOrder table. External exports' PO numbers are messy free text
+  // ("Not available", "Pending", or an actual number) with no matching
+  // PurchaseOrder row to link to here, so this just preserves the raw
+  // value for reference instead of forcing a fake relation.
+  externalPoNumber   String?              @map("external_po_number")
   createdAt          DateTime             @default(now()) @map("created_at") @db.Timestamptz(6)
   // Back-relation for Assignment.assetItemId — an AssetItem can have
   // multiple Assignment rows over its lifetime (historical + at most one

src/app/api/assets/route.ts

@@ -22,8 +22,17 @@ export async function POST(request: Request): Promise<NextResponse> {
     return NextResponse.json({ error: "Request body must be a JSON object" }, { status: 400 });
   }
 
-  const { serialNumber, assetTag, modelId, purchaseDate, warrantyEndDate, purchaseOrderId } =
-    body as Record<string, unknown>;
+  const {
+    serialNumber,
+    assetTag,
+    modelId,
+    purchaseDate,
+    warrantyEndDate,
+    purchaseOrderId,
+    cost,
+    costCurrency,
+    externalPoNumber,
+  } = body as Record<string, unknown>;
   const validation = validateCreateAssetItemInput({
     serialNumber,
     assetTag,
@@ -31,6 +40,9 @@ export async function POST(request: Request): Promise<NextResponse> {
     purchaseDate,
     warrantyEndDate,
     purchaseOrderId,
+    cost,
+    costCurrency,
+    externalPoNumber,
   });
 
   if (!validation.ok) {

src/app/assets/page.tsx

@@ -31,7 +31,10 @@ interface AssetItemRecord {
   purchase_date: string | null;
   warranty_end_date: string | null;
   status: "in_stock" | "assigned" | "repair" | "retired";
+  cost: number | null;
+  cost_currency: string | null;
   purchase_order_id: string | null;
+  external_po_number: string | null;
   created_at: string;
 }
 
@@ -76,6 +79,9 @@ export default function AssetsPage() {
   const [purchaseDate, setPurchaseDate] = useState("");
   const [warrantyEndDate, setWarrantyEndDate] = useState("");
   const [purchaseOrderId, setPurchaseOrderId] = useState(NO_PURCHASE_ORDER_VALUE);
+  const [cost, setCost] = useState("");
+  const [costCurrency, setCostCurrency] = useState("");
+  const [externalPoNumber, setExternalPoNumber] = useState("");
   const [submitting, setSubmitting] = useState(false);
   const [submitError, setSubmitError] = useState<string | null>(null);
 
@@ -115,7 +121,7 @@ export default function AssetsPage() {
               .join("; ") +
             (errorCount > 5 ? ` (+${errorCount - 5} lỗi khác)` : "")
           : "";
-      setImportMessage(`Đã import ${body.created} asset.` + errorSummary);
+      setImportMessage(`Tạo mới ${body.created}, cập nhật ${body.updated} asset.` + errorSummary);
       refetch();
     } catch {
       setImportStatus("error");
@@ -131,6 +137,15 @@ export default function AssetsPage() {
     const hasAssetTag = assetTag.trim() !== "";
     const hasWarrantyEndDate = warrantyEndDate.trim() !== "";
     const hasPurchaseOrderId = purchaseOrderId !== NO_PURCHASE_ORDER_VALUE;
+    const hasCost = cost.trim() !== "";
+    const hasCostCurrency = costCurrency.trim() !== "";
+    const hasExternalPoNumber = externalPoNumber.trim() !== "";
+
+    if (hasCost && Number.isNaN(Number(cost))) {
+      setSubmitError("Cost must be a number");
+      setSubmitting(false);
+      return;
+    }
 
     try {
       const response = await fetch("/api/assets", {
@@ -146,6 +161,9 @@ export default function AssetsPage() {
           ...(hasAssetTag ? { assetTag } : {}),
           ...(hasWarrantyEndDate ? { warrantyEndDate } : {}),
           ...(hasPurchaseOrderId ? { purchaseOrderId } : {}),
+          ...(hasCost ? { cost: Number(cost) } : {}),
+          ...(hasCostCurrency ? { costCurrency } : {}),
+          ...(hasExternalPoNumber ? { externalPoNumber } : {}),
         }),
       });
 
@@ -174,6 +192,9 @@ export default function AssetsPage() {
       setPurchaseDate("");
       setWarrantyEndDate("");
       setPurchaseOrderId(NO_PURCHASE_ORDER_VALUE);
+      setCost("");
+      setCostCurrency("");
+      setExternalPoNumber("");
       refetch();
     } catch {
       setSubmitError("Request failed");
@@ -202,7 +223,9 @@ export default function AssetsPage() {
                 <TableHead>Purchase Date</TableHead>
                 <TableHead>Warranty End Date</TableHead>
                 <TableHead>Status</TableHead>
+                <TableHead>Cost</TableHead>
                 <TableHead>Purchase Order ID</TableHead>
+                <TableHead>External PO Number</TableHead>
                 <TableHead>Created At</TableHead>
               </TableRow>
             </TableHeader>
@@ -216,7 +239,13 @@ export default function AssetsPage() {
                   <TableCell>{assetItem.purchase_date ?? "-"}</TableCell>
                   <TableCell>{assetItem.warranty_end_date ?? "-"}</TableCell>
                   <TableCell>{assetItem.status}</TableCell>
+                  <TableCell>
+                    {assetItem.cost !== null
+                      ? `${assetItem.cost}${assetItem.cost_currency ? " " + assetItem.cost_currency : ""}`
+                      : "-"}
+                  </TableCell>
                   <TableCell>{assetItem.purchase_order_id ?? "-"}</TableCell>
+                  <TableCell>{assetItem.external_po_number ?? "-"}</TableCell>
                   <TableCell>{assetItem.created_at}</TableCell>
                 </TableRow>
               ))}
@@ -233,11 +262,14 @@ export default function AssetsPage() {
           <a href="/asset-models" className="underline">
             /asset-models
           </a>
-          ), <code>purchase date</code> (bắt buộc -- cũng nhận <code>order received</code>).
+          ), <code>purchase date</code> (không bắt buộc -- cũng nhận <code>order received</code>).
           Tuỳ chọn: <code>asset tag</code>, <code>warranty end date</code> (bỏ trống thì tự tính
           từ warranty của model), <code>status</code>/<code>state</code> (nhận{" "}
           <code>In use</code> → assigned, <code>In stock</code> → in_stock, bỏ trống thì mặc định
-          in_stock), <code>purchase order id</code>.
+          in_stock), <code>cost</code>, <code>cost currency</code>,{" "}
+          <code>po number</code> (text tự do, khác <code>purchase order id</code> là UUID trong
+          hệ thống). Dòng có <code>asset tag</code> hoặc <code>serial number</code> đã tồn tại sẽ{" "}
+          <b>cập nhật</b> thay vì báo lỗi trùng -- import lại file mới để đồng bộ dữ liệu.
         </p>
         <div className="flex flex-wrap items-center gap-3">
           <a href="/api/assets/export">
@@ -348,6 +380,38 @@ export default function AssetsPage() {
             </Select>
           </div>
 
+          <div className="flex flex-col gap-2">
+            <Label htmlFor="cost">Cost (optional)</Label>
+            <Input
+              id="cost"
+              type="number"
+              min={0}
+              step="0.01"
+              value={cost}
+              onChange={(event) => setCost(event.target.value)}
+            />
+          </div>
+
+          <div className="flex flex-col gap-2">
+            <Label htmlFor="costCurrency">Cost Currency (optional)</Label>
+            <Input
+              id="costCurrency"
+              value={costCurrency}
+              onChange={(event) => setCostCurrency(event.target.value)}
+              placeholder="e.g. VND, USD"
+            />
+          </div>
+
+          <div className="flex flex-col gap-2">
+            <Label htmlFor="externalPoNumber">External PO Number (optional)</Label>
+            <Input
+              id="externalPoNumber"
+              value={externalPoNumber}
+              onChange={(event) => setExternalPoNumber(event.target.value)}
+              placeholder="PO number from an external system, if any"
+            />
+          </div>
+
           {submitError ? <p className="text-sm text-destructive">{submitError}</p> : null}
 
           <Button type="submit" disabled={submitting}>

src/lib/assets.ts

@@ -13,7 +13,13 @@ export interface AssetItemRecord {
   purchase_date: string | null;
   warranty_end_date: string | null;
   status: AssetItemStatus;
+  cost: number | null;
+  cost_currency: string | null;
   purchase_order_id: string | null;
+  // Free-text PO number from an external system -- NOT purchase_order_id
+  // above (a real FK). See schema.prisma's AssetItem.externalPoNumber
+  // comment.
+  external_po_number: string | null;
   created_at: string;
 }
 
@@ -29,7 +35,10 @@ export interface CreateAssetItemInput {
   // comment.
   purchaseDate?: Date;
   warrantyEndDate?: Date;
+  cost?: number | null;
+  costCurrency?: string | null;
   purchaseOrderId?: string | null;
+  externalPoNumber?: string | null;
   // Only set by importAssetItems() (bulk-loading already-deployed
   // inventory from a real export -- see docs/asset-license-management.md's
   // 2026-08-24 section). The manual /assets create form never sends this,
@@ -90,6 +99,19 @@ const createAssetItemSchema = z.object({
     .uuid("purchaseOrderId must be a valid UUID string")
     .optional()
     .nullable(),
+  cost: z
+    .number({ invalid_type_error: "cost must be a non-negative number" })
+    .nonnegative("cost must be a non-negative number")
+    .optional()
+    .nullable(),
+  costCurrency: z
+    .string({ invalid_type_error: "costCurrency must be a string" })
+    .optional()
+    .nullable(),
+  externalPoNumber: z
+    .string({ invalid_type_error: "externalPoNumber must be a string" })
+    .optional()
+    .nullable(),
 });
 
 /**
@@ -114,6 +136,9 @@ export function validateCreateAssetItemInput(input: {
   purchaseDate?: unknown;
   warrantyEndDate?: unknown;
   purchaseOrderId?: unknown;
+  cost?: unknown;
+  costCurrency?: unknown;
+  externalPoNumber?: unknown;
 }): ValidationResult {
   const result = createAssetItemSchema.safeParse(input);
   if (!result.success) {
@@ -131,7 +156,10 @@ function toRecord(row: {
   purchaseDate: Date | null;
   warrantyEndDate: Date | null;
   status: AssetItemStatus;
+  cost: Prisma.Decimal | null;
+  costCurrency: string | null;
   purchaseOrderId: string | null;
+  externalPoNumber: string | null;
   createdAt: Date;
 }): AssetItemRecord {
   return {
@@ -142,7 +170,10 @@ function toRecord(row: {
     purchase_date: row.purchaseDate ? row.purchaseDate.toISOString() : null,
     warranty_end_date: row.warrantyEndDate ? row.warrantyEndDate.toISOString() : null,
     status: row.status,
+    cost: row.cost ? row.cost.toNumber() : null,
+    cost_currency: row.costCurrency,
     purchase_order_id: row.purchaseOrderId,
+    external_po_number: row.externalPoNumber,
     created_at: row.createdAt.toISOString(),
   };
 }
@@ -214,7 +245,10 @@ export async function createAssetItem(
         modelId: input.modelId,
         purchaseDate: input.purchaseDate ?? null,
         warrantyEndDate,
+        cost: input.cost ?? null,
+        costCurrency: input.costCurrency ?? null,
         purchaseOrderId: input.purchaseOrderId ?? null,
+        externalPoNumber: input.externalPoNumber ?? null,
         ...(input.status ? { status: input.status } : {}),
       },
     });
@@ -271,6 +305,15 @@ export interface ImportAssetItemRow {
   // not here (parsing stays dumb string-in/string-out, same as every other
   // field on this row).
   status: string | null;
+  // Raw text -- parsed to a number by importAssetItems() below (also
+  // treats common placeholder junk like "Not available"/"Pending"/"N/A" as
+  // absent, same spirit as externalPoNumber below -- real exports are
+  // messy).
+  cost: string | null;
+  costCurrency: string | null;
+  // NOT the same as purchaseOrderId above -- see schema.prisma's
+  // AssetItem.externalPoNumber comment.
+  externalPoNumber: string | null;
 }
 
 const ASSET_ITEM_HEADER_ALIASES: Record<keyof ImportAssetItemRow, string[]> = {
@@ -300,6 +343,13 @@ const ASSET_ITEM_HEADER_ALIASES: Record<keyof ImportAssetItemRow, string[]> = {
   ],
   purchaseOrderId: ["purchaseorderid", "purchase order id", "po", "poid", "po id"],
   status: ["status", "state", "tinh trang"],
+  cost: ["cost", "gia", "gia tri"],
+  costCurrency: ["costcurrency", "cost currency", "currency", "don vi tien te"],
+  // "po number" is deliberately distinct from purchaseOrderId's aliases
+  // above ("po"/"poid"/"po id") -- matches a real ServiceNow export's
+  // actual "PO number" column name 1:1, and keeps the two fields
+  // unambiguous from each other by header name alone.
+  externalPoNumber: ["ponumber", "po number", "external po number", "so po"],
 };
 
 export type ParseAssetItemsCsvResult =
@@ -369,6 +419,9 @@ export function parseAssetItemsCsv(text: string): ParseAssetItemsCsvResult {
       warrantyEndDate: get("warrantyEndDate") || null,
       purchaseOrderId: get("purchaseOrderId") || null,
       status: get("status") || null,
+      cost: get("cost") || null,
+      costCurrency: get("costCurrency") || null,
+      externalPoNumber: get("externalPoNumber") || null,
     };
     if (!row.serialNumber && !row.manufacturer && !row.modelName && !row.purchaseDate) {
       continue; // fully blank row
@@ -381,6 +434,7 @@ export function parseAssetItemsCsv(text: string): ParseAssetItemsCsvResult {
 
 export interface ImportAssetItemsResult {
   created: number;
+  updated: number;
   errors: { row: number; serialNumber: string; error: string }[];
 }
 
@@ -407,21 +461,58 @@ function statusFromImportText(text: string): AssetItemStatus | null {
   return IMPORT_STATUS_MAP[text.trim().toLowerCase()] ?? null;
 }
 
+// Real external exports (e.g. the ServiceNow-style ITAM report this was
+// built against) fill blank PO-number-ish cells with placeholder junk
+// instead of leaving them empty -- treat these as "no value" rather than
+// storing the literal junk text.
+const PLACEHOLDER_VALUES = new Set(["not available", "pending", "n/a", "na", "none", "-"]);
+
+function cleanImportText(text: string | null): string | null {
+  if (!text) return null;
+  return PLACEHOLDER_VALUES.has(text.trim().toLowerCase()) ? null : text;
+}
+
+// Cost cells can carry currency symbols/thousands separators depending on
+// how the source spreadsheet formatted them (e.g. "1,234.56" or "1234").
+// Strips anything that isn't a digit, minus sign, or decimal point before
+// parsing -- simple on purpose, this isn't trying to be a general money
+// parser, just tolerant of the punctuation Excel commonly adds.
+function parseImportCost(text: string): number | null {
+  const cleaned = cleanImportText(text);
+  if (!cleaned) return null;
+  const numeric = Number(cleaned.replace(/[^0-9.-]/g, ""));
+  return Number.isNaN(numeric) ? null : numeric;
+}
+
 /**
- * Creates one AssetItem per row via createAssetItem() (so uniqueness,
- * warranty auto-fill, and FK handling all stay in one place, not
- * duplicated here) and reports per-row failures instead of aborting the
- * whole import on the first bad row -- matches parseAssetItemsCsv()'s
- * "one typo shouldn't cost 199 other rows" rationale. `row` in the result
- * is the spreadsheet row number (header = row 1), for the operator to find
- * and fix in their original file. Sequential, not batched -- fine at this
- * app's actual scale (hundreds of rows, see docs/asset-license-management.md),
- * and keeps each row's error attributable instead of one opaque bulk
- * failure.
+ * Creates one AssetItem per row via createAssetItem(), OR updates it if a
+ * row with the same assetTag or serialNumber already exists (2026-08-24 --
+ * added so re-uploading a refreshed export, e.g. the company's periodic
+ * ServiceNow re-sync, updates existing rows instead of failing every one
+ * of them on a uniqueness conflict). Matching prefers assetTag when
+ * present (the more stable real-world identifier -- a device's serial
+ * rarely changes but its owner/status might get re-tagged), falling back
+ * to serialNumber. Update only touches fields this row actually carries a
+ * (non-empty) value for -- a blank cell means "no change", not "clear this
+ * field", so partial re-syncs (e.g. a cost-only refresh with no other
+ * columns) don't wipe out data the file simply didn't include this time.
+ * warrantyEndDate is the one exception: it's only touched on UPDATE when
+ * explicitly present in the row (never silently recomputed from
+ * warrantyMonths the way CREATE does), so a manually-corrected warranty
+ * date survives a re-sync.
+ *
+ * Reports per-row failures instead of aborting the whole import on the
+ * first bad row -- matches parseAssetItemsCsv()'s "one typo shouldn't cost
+ * 199 other rows" rationale. `row` in the result is the spreadsheet row
+ * number (header = row 1), for the operator to find and fix in their
+ * original file. Sequential, not batched -- fine at this app's actual
+ * scale (hundreds of rows, see docs/asset-license-management.md), and
+ * keeps each row's error attributable instead of one opaque bulk failure.
  */
 export async function importAssetItems(rows: ImportAssetItemRow[]): Promise<ImportAssetItemsResult> {
   const errors: ImportAssetItemsResult["errors"] = [];
   let created = 0;
+  let updated = 0;
 
   for (let i = 0; i < rows.length; i++) {
     const row = rows[i];
@@ -469,6 +560,9 @@ export async function importAssetItems(rows: ImportAssetItemRow[]): Promise<Impo
       }
       status = mapped;
     }
+    const cost = row.cost ? parseImportCost(row.cost) : null;
+    const costCurrency = cleanImportText(row.costCurrency);
+    const externalPoNumber = cleanImportText(row.externalPoNumber);
 
     const model = await prisma.assetModel.findFirst({
       where: {
@@ -485,6 +579,37 @@ export async function importAssetItems(rows: ImportAssetItemRow[]): Promise<Impo
       continue;
     }
 
+    const existing = await prisma.assetItem.findFirst({
+      where: {
+        OR: [
+          ...(row.assetTag ? [{ assetTag: row.assetTag }] : []),
+          { serialNumber: row.serialNumber },
+        ],
+      },
+    });
+
+    if (existing) {
+      // Partial update -- only fields this row actually carries a value
+      // for (see importAssetItems()'s doc comment above for why blank
+      // means "no change", not "clear").
+      await prisma.assetItem.update({
+        where: { id: existing.id },
+        data: {
+          ...(row.assetTag ? { assetTag: row.assetTag } : {}),
+          modelId: model.id,
+          ...(row.purchaseDate ? { purchaseDate: new Date(row.purchaseDate) } : {}),
+          ...(warrantyEndDate ? { warrantyEndDate } : {}),
+          ...(status ? { status } : {}),
+          ...(cost !== null ? { cost } : {}),
+          ...(costCurrency ? { costCurrency } : {}),
+          ...(row.purchaseOrderId ? { purchaseOrderId: row.purchaseOrderId } : {}),
+          ...(externalPoNumber ? { externalPoNumber } : {}),
+        },
+      });
+      updated++;
+      continue;
+    }
+
     const result = await createAssetItem({
       serialNumber: row.serialNumber,
       assetTag: row.assetTag ?? undefined,
@@ -492,7 +617,10 @@ export async function importAssetItems(rows: ImportAssetItemRow[]): Promise<Impo
       purchaseDate: row.purchaseDate ? new Date(row.purchaseDate) : undefined,
       warrantyEndDate,
       status,
+      cost,
+      costCurrency,
       purchaseOrderId: row.purchaseOrderId ?? undefined,
+      externalPoNumber,
     });
     if (!result.ok) {
       errors.push({ row: rowNumber, serialNumber: row.serialNumber, error: result.error });
@@ -501,7 +629,7 @@ export async function importAssetItems(rows: ImportAssetItemRow[]): Promise<Impo
     created++;
   }
 
-  return { created, errors };
+  return { created, updated, errors };
 }
 
 /**
@@ -526,7 +654,10 @@ export async function exportAssetItemsCsv(): Promise<string> {
     "purchase_date",
     "warranty_end_date",
     "status",
+    "cost",
+    "cost_currency",
     "purchase_order_id",
+    "external_po_number",
   ];
   const lines = [header.join(",")];
   for (const row of rows) {
@@ -538,7 +669,10 @@ export async function exportAssetItemsCsv(): Promise<string> {
       row.purchaseDate ? row.purchaseDate.toISOString().slice(0, 10) : "",
       row.warrantyEndDate ? row.warrantyEndDate.toISOString().slice(0, 10) : "",
       row.status,
+      row.cost ? row.cost.toString() : "",
+      row.costCurrency ?? "",
       row.purchaseOrderId ?? "",
+      row.externalPoNumber ?? "",
     ];
     lines.push(cells.map(csvField).join(","));
   }