diff --git a/prisma/migrations/20260802232754_add_vendor/migration.sql b/prisma/migrations/20260802232754_add_vendor/migration.sql
new file mode 100644
index 0000000..b30f4f5
--- /dev/null
+++ b/prisma/migrations/20260802232754_add_vendor/migration.sql
@@ -0,0 +1,13 @@
+-- CreateTable
+CREATE TABLE "vendors" (
+    "id" UUID NOT NULL,
+    "name" TEXT NOT NULL,
+    "contact_email" TEXT NOT NULL,
+    "contact_phone" TEXT NOT NULL,
+    "address" TEXT NOT NULL,
+    "tax_code" TEXT,
+    "notes" TEXT,
+    "created_at" TIMESTAMPTZ(6) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+
+    CONSTRAINT "vendors_pkey" PRIMARY KEY ("id")
+);
diff --git a/prisma/schema.prisma b/prisma/schema.prisma
index 63c54fa..02d35a0 100644
--- a/prisma/schema.prisma
+++ b/prisma/schema.prisma
@@ -122,6 +122,28 @@ model License {
   @@map("licenses")
 }
 
+// Purchasing counterparty — see docs/asset-license-management.md's "## Vendor
+// (chốt 2026-08-02)". Deliberately independent of AssetModel.manufacturer
+// (OEM, e.g. "Dell") — Vendor is the reseller/distributor actually bought
+// from (e.g. "FPT Trading"), a different concept that isn't always the same
+// company. No FKs on this entity yet: it's the starting point for later
+// FKs from PurchaseOrder/License (License.vendor string -> License.vendorId
+// FK retrofit is noted in the doc as a separate follow-up, not done here).
+// taxCode/notes are nullable — not every vendor record has a known VN tax
+// code or extra notes at creation time.
+model Vendor {
+  id           String   @id @default(uuid()) @db.Uuid
+  name         String
+  contactEmail String   @map("contact_email")
+  contactPhone String   @map("contact_phone")
+  address      String
+  taxCode      String?  @map("tax_code")
+  notes        String?
+  createdAt    DateTime @default(now()) @map("created_at") @db.Timestamptz(6)
+
+  @@map("vendors")
+}
+
 // Minimal internal auth accounts — NOT company SSO (deliberately ruled out,
 // see CLAUDE.md / auth decision notes). A handful of trusted IT staff
 // accounts, created by hand via scripts/create-user.ts, no self-registration.
diff --git a/src/app/api/vendors/route.ts b/src/app/api/vendors/route.ts
new file mode 100644
index 0000000..fcb5130
--- /dev/null
+++ b/src/app/api/vendors/route.ts
@@ -0,0 +1,52 @@
+import { NextResponse } from "next/server";
+import { auth } from "@/auth";
+import { createVendor, listVendors, validateCreateVendorInput } from "@/lib/vendors";
+
+// Mirrors src/app/api/licenses/route.ts's pattern — middleware.ts excludes
+// /api from route protection, so this checks the session itself. Flat
+// permission model (CLAUDE.md): only "logged in or not", no role check.
+export async function POST(request: Request): Promise<NextResponse> {
+  const session = await auth();
+  if (!session) {
+    return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+  }
+
+  let body: unknown;
+  try {
+    body = await request.json();
+  } catch {
+    return NextResponse.json({ error: "Request body must be valid JSON" }, { status: 400 });
+  }
+
+  if (typeof body !== "object" || body === null) {
+    return NextResponse.json({ error: "Request body must be a JSON object" }, { status: 400 });
+  }
+
+  const { name, contactEmail, contactPhone, address, taxCode, notes } =
+    body as Record<string, unknown>;
+  const validation = validateCreateVendorInput({
+    name,
+    contactEmail,
+    contactPhone,
+    address,
+    taxCode,
+    notes,
+  });
+
+  if (!validation.ok) {
+    return NextResponse.json({ error: validation.error }, { status: 400 });
+  }
+
+  const created = await createVendor(validation.value);
+  return NextResponse.json(created, { status: 201 });
+}
+
+export async function GET(): Promise<NextResponse> {
+  const session = await auth();
+  if (!session) {
+    return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+  }
+
+  const vendors = await listVendors();
+  return NextResponse.json(vendors, { status: 200 });
+}
diff --git a/src/lib/vendors.ts b/src/lib/vendors.ts
new file mode 100644
index 0000000..1763603
--- /dev/null
+++ b/src/lib/vendors.ts
@@ -0,0 +1,123 @@
+import { z } from "zod";
+import { prisma } from "./prisma";
+
+export interface VendorRecord {
+  id: string;
+  name: string;
+  contact_email: string;
+  contact_phone: string;
+  address: string;
+  tax_code: string | null;
+  notes: string | null;
+  created_at: string;
+}
+
+export interface CreateVendorInput {
+  name: string;
+  contactEmail: string;
+  contactPhone: string;
+  address: string;
+  taxCode?: string | null;
+  notes?: string | null;
+}
+
+export type ValidationResult =
+  | { ok: true; value: CreateVendorInput }
+  | { ok: false; error: string };
+
+// Mirrors src/lib/licenses.ts's nonEmptyString helper.
+function nonEmptyString(message: string) {
+  return z.string({ required_error: message, invalid_type_error: message }).refine(
+    (value) => value.trim() !== "",
+    { message }
+  );
+}
+
+const createVendorSchema = z.object({
+  name: nonEmptyString("name is required and must be a non-empty string"),
+  contactEmail: z
+    .string({
+      required_error: "contactEmail is required and must be a valid email",
+      invalid_type_error: "contactEmail is required and must be a valid email",
+    })
+    .email("contactEmail is required and must be a valid email"),
+  contactPhone: nonEmptyString("contactPhone is required and must be a non-empty string"),
+  address: nonEmptyString("address is required and must be a non-empty string"),
+  // Nullable, per docs/asset-license-management.md's "## Vendor" spec — not
+  // every vendor record has a known VN tax code at creation time.
+  taxCode: nonEmptyString("taxCode must be a non-empty string").optional().nullable(),
+  notes: nonEmptyString("notes must be a non-empty string").optional().nullable(),
+});
+
+/**
+ * Validates raw (untyped) vendor-creation input. name/contactPhone/address
+ * must be non-empty strings, contactEmail must be a valid email string,
+ * taxCode/notes are optional/nullable (per the "## Vendor" spec in
+ * docs/asset-license-management.md) but must be non-empty strings if
+ * present.
+ */
+export function validateCreateVendorInput(input: {
+  name?: unknown;
+  contactEmail?: unknown;
+  contactPhone?: unknown;
+  address?: unknown;
+  taxCode?: unknown;
+  notes?: unknown;
+}): ValidationResult {
+  const result = createVendorSchema.safeParse(input);
+  if (!result.success) {
+    const message = result.error.issues[0]?.message ?? "Invalid input";
+    return { ok: false, error: message };
+  }
+  return { ok: true, value: result.data };
+}
+
+function toRecord(row: {
+  id: string;
+  name: string;
+  contactEmail: string;
+  contactPhone: string;
+  address: string;
+  taxCode: string | null;
+  notes: string | null;
+  createdAt: Date;
+}): VendorRecord {
+  return {
+    id: row.id,
+    name: row.name,
+    contact_email: row.contactEmail,
+    contact_phone: row.contactPhone,
+    address: row.address,
+    tax_code: row.taxCode,
+    notes: row.notes,
+    created_at: row.createdAt.toISOString(),
+  };
+}
+
+/**
+ * Creates a Vendor. No unique constraint exists on any field, no FKs
+ * either (see docs/asset-license-management.md's "## Vendor" spec — this
+ * is a standalone entity, same starting shape as Employee/License before
+ * they grew relations) — so unlike createAssetItem()/createEmployee()
+ * there's no known Prisma error code to catch/translate here.
+ */
+export async function createVendor(input: CreateVendorInput): Promise<VendorRecord> {
+  const created = await prisma.vendor.create({
+    data: {
+      name: input.name,
+      contactEmail: input.contactEmail,
+      contactPhone: input.contactPhone,
+      address: input.address,
+      taxCode: input.taxCode ?? null,
+      notes: input.notes ?? null,
+    },
+  });
+  return toRecord(created);
+}
+
+export async function listVendors(): Promise<VendorRecord[]> {
+  const rows = await prisma.vendor.findMany({
+    orderBy: [{ createdAt: "desc" }, { id: "desc" }],
+  });
+  return rows.map(toRecord);
+}
diff --git a/tests/vendors.test.ts b/tests/vendors.test.ts
new file mode 100644
index 0000000..98b315b
--- /dev/null
+++ b/tests/vendors.test.ts
@@ -0,0 +1,476 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import type { Mock } from "vitest";
+import type { Session } from "next-auth";
+import {
+  createVendor,
+  listVendors,
+  validateCreateVendorInput,
+} from "@/lib/vendors";
+import { prisma } from "@/lib/prisma";
+
+// Note: this file has two layers of coverage, mirroring tests/licenses.test.ts:
+// - lib-level tests below exercise src/lib/vendors.ts directly (validation,
+//   nullable taxCode/notes, list ordering).
+// - route-level tests (further down) exercise src/app/api/vendors/route.ts
+//   over HTTP, including the auth() gate — mirrors tests/licenses.test.ts's
+//   @/auth mocking pattern.
+vi.mock("@/auth", () => ({ auth: vi.fn() }));
+
+import { GET, POST } from "@/app/api/vendors/route";
+import { auth } from "@/auth";
+
+const mockedAuth = auth as unknown as Mock<() => Promise<Session | null>>;
+
+const testSession: Session = {
+  user: { id: "test-user-id" },
+  expires: new Date(Date.now() + 60 * 60 * 1000).toISOString(),
+};
+
+function postRequest(body: unknown): Request {
+  return new Request("http://localhost/api/vendors", {
+    method: "POST",
+    headers: { "content-type": "application/json" },
+    body: JSON.stringify(body),
+  });
+}
+
+beforeEach(async () => {
+  // Each test starts from an empty table so listing/order assertions are
+  // deterministic.
+  await prisma.vendor.deleteMany();
+  // Default to a logged-in session — the lib-level tests below don't go
+  // through the route at all (so this is a no-op for them), and the
+  // route-level tests exercise business logic, not auth gating (that's
+  // covered by the "auth gating" describe block further down).
+  mockedAuth.mockResolvedValue(testSession);
+});
+
+describe("validateCreateVendorInput", () => {
+  it("accepts valid input with taxCode and notes", () => {
+    const result = validateCreateVendorInput({
+      name: "FPT Trading",
+      contactEmail: "sales@fpt.com.vn",
+      contactPhone: "0281234567",
+      address: "123 Nguyen Van Linh, Q7, HCMC",
+      taxCode: "0301234567",
+      notes: "Preferred reseller for Dell laptops",
+    });
+
+    expect(result.ok).toBe(true);
+    if (result.ok) {
+      expect(result.value).toMatchObject({
+        name: "FPT Trading",
+        contactEmail: "sales@fpt.com.vn",
+        contactPhone: "0281234567",
+        address: "123 Nguyen Van Linh, Q7, HCMC",
+        taxCode: "0301234567",
+        notes: "Preferred reseller for Dell laptops",
+      });
+    }
+  });
+
+  it("accepts valid input with no taxCode/notes", () => {
+    const result = validateCreateVendorInput({
+      name: "Synnex FPT",
+      contactEmail: "contact@synnexfpt.com",
+      contactPhone: "0287654321",
+      address: "456 Le Van Viet, Q9, HCMC",
+    });
+
+    expect(result.ok).toBe(true);
+    if (result.ok) {
+      expect(result.value.taxCode).toBeUndefined();
+      expect(result.value.notes).toBeUndefined();
+    }
+  });
+
+  it("rejects an empty name", () => {
+    const result = validateCreateVendorInput({
+      name: "",
+      contactEmail: "sales@fpt.com.vn",
+      contactPhone: "0281234567",
+      address: "123 Nguyen Van Linh, Q7, HCMC",
+    });
+
+    expect(result.ok).toBe(false);
+    if (!result.ok) {
+      expect(result.error).toMatch(/name/i);
+    }
+  });
+
+  it("rejects an invalid contactEmail", () => {
+    const result = validateCreateVendorInput({
+      name: "FPT Trading",
+      contactEmail: "not-an-email",
+      contactPhone: "0281234567",
+      address: "123 Nguyen Van Linh, Q7, HCMC",
+    });
+
+    expect(result.ok).toBe(false);
+    if (!result.ok) {
+      expect(result.error).toMatch(/contactEmail/i);
+    }
+  });
+
+  it("rejects a missing contactEmail", () => {
+    const result = validateCreateVendorInput({
+      name: "FPT Trading",
+      contactPhone: "0281234567",
+      address: "123 Nguyen Van Linh, Q7, HCMC",
+    });
+
+    expect(result.ok).toBe(false);
+    if (!result.ok) {
+      expect(result.error).toMatch(/contactEmail/i);
+    }
+  });
+
+  it("rejects an empty contactPhone", () => {
+    const result = validateCreateVendorInput({
+      name: "FPT Trading",
+      contactEmail: "sales@fpt.com.vn",
+      contactPhone: "",
+      address: "123 Nguyen Van Linh, Q7, HCMC",
+    });
+
+    expect(result.ok).toBe(false);
+    if (!result.ok) {
+      expect(result.error).toMatch(/contactPhone/i);
+    }
+  });
+
+  it("rejects an empty address", () => {
+    const result = validateCreateVendorInput({
+      name: "FPT Trading",
+      contactEmail: "sales@fpt.com.vn",
+      contactPhone: "0281234567",
+      address: "",
+    });
+
+    expect(result.ok).toBe(false);
+    if (!result.ok) {
+      expect(result.error).toMatch(/address/i);
+    }
+  });
+
+  it("rejects an empty taxCode when provided", () => {
+    const result = validateCreateVendorInput({
+      name: "FPT Trading",
+      contactEmail: "sales@fpt.com.vn",
+      contactPhone: "0281234567",
+      address: "123 Nguyen Van Linh, Q7, HCMC",
+      taxCode: "",
+    });
+
+    expect(result.ok).toBe(false);
+    if (!result.ok) {
+      expect(result.error).toMatch(/taxCode/i);
+    }
+  });
+
+  it("accepts a null taxCode/notes explicitly", () => {
+    const result = validateCreateVendorInput({
+      name: "FPT Trading",
+      contactEmail: "sales@fpt.com.vn",
+      contactPhone: "0281234567",
+      address: "123 Nguyen Van Linh, Q7, HCMC",
+      taxCode: null,
+      notes: null,
+    });
+
+    expect(result.ok).toBe(true);
+    if (result.ok) {
+      expect(result.value.taxCode).toBeNull();
+      expect(result.value.notes).toBeNull();
+    }
+  });
+});
+
+describe("createVendor", () => {
+  it("creates a vendor with taxCode and notes", async () => {
+    const result = validateCreateVendorInput({
+      name: "FPT Trading",
+      contactEmail: "sales@fpt.com.vn",
+      contactPhone: "0281234567",
+      address: "123 Nguyen Van Linh, Q7, HCMC",
+      taxCode: "0301234567",
+      notes: "Preferred reseller for Dell laptops",
+    });
+    expect(result.ok).toBe(true);
+    if (!result.ok) return;
+
+    const record = await createVendor(result.value);
+
+    expect(record).toMatchObject({
+      name: "FPT Trading",
+      contact_email: "sales@fpt.com.vn",
+      contact_phone: "0281234567",
+      address: "123 Nguyen Van Linh, Q7, HCMC",
+      tax_code: "0301234567",
+      notes: "Preferred reseller for Dell laptops",
+    });
+    expect(typeof record.id).toBe("string");
+    expect(record.id.length).toBeGreaterThan(0);
+    expect(Number.isNaN(Date.parse(record.created_at))).toBe(false);
+  });
+
+  it("creates a vendor with no taxCode/notes (both null)", async () => {
+    const result = validateCreateVendorInput({
+      name: "Synnex FPT",
+      contactEmail: "contact@synnexfpt.com",
+      contactPhone: "0287654321",
+      address: "456 Le Van Viet, Q9, HCMC",
+    });
+    expect(result.ok).toBe(true);
+    if (!result.ok) return;
+
+    const record = await createVendor(result.value);
+
+    expect(record.tax_code).toBeNull();
+    expect(record.notes).toBeNull();
+  });
+});
+
+describe("listVendors", () => {
+  it("lists created vendors, newest first", async () => {
+    const first = validateCreateVendorInput({
+      name: "Synnex FPT",
+      contactEmail: "contact@synnexfpt.com",
+      contactPhone: "0287654321",
+      address: "456 Le Van Viet, Q9, HCMC",
+    });
+    expect(first.ok).toBe(true);
+    if (first.ok) await createVendor(first.value);
+
+    // Ensure a distinct created_at ordering even on fast filesystems/clocks.
+    await new Promise((resolve) => setTimeout(resolve, 5));
+
+    const second = validateCreateVendorInput({
+      name: "FPT Trading",
+      contactEmail: "sales@fpt.com.vn",
+      contactPhone: "0281234567",
+      address: "123 Nguyen Van Linh, Q7, HCMC",
+    });
+    expect(second.ok).toBe(true);
+    if (second.ok) await createVendor(second.value);
+
+    const records = await listVendors();
+
+    expect(records).toHaveLength(2);
+    // newest first
+    expect(records[0]).toMatchObject({ name: "FPT Trading" });
+    expect(records[1]).toMatchObject({ name: "Synnex FPT" });
+  });
+
+  it("returns an empty list when there are no vendors", async () => {
+    const records = await listVendors();
+    expect(records).toEqual([]);
+  });
+});
+
+describe("POST /api/vendors", () => {
+  it("creates a vendor on valid input", async () => {
+    const res = await POST(
+      postRequest({
+        name: "FPT Trading",
+        contactEmail: "sales@fpt.com.vn",
+        contactPhone: "0281234567",
+        address: "123 Nguyen Van Linh, Q7, HCMC",
+        taxCode: "0301234567",
+        notes: "Preferred reseller for Dell laptops",
+      })
+    );
+
+    expect(res.status).toBe(201);
+    const body = await res.json();
+
+    expect(body).toMatchObject({
+      name: "FPT Trading",
+      contact_email: "sales@fpt.com.vn",
+      contact_phone: "0281234567",
+      address: "123 Nguyen Van Linh, Q7, HCMC",
+      tax_code: "0301234567",
+      notes: "Preferred reseller for Dell laptops",
+    });
+    expect(typeof body.id).toBe("string");
+    expect(body.id.length).toBeGreaterThan(0);
+    expect(Number.isNaN(Date.parse(body.created_at))).toBe(false);
+  });
+
+  it("creates a vendor with no taxCode/notes", async () => {
+    const res = await POST(
+      postRequest({
+        name: "Synnex FPT",
+        contactEmail: "contact@synnexfpt.com",
+        contactPhone: "0287654321",
+        address: "456 Le Van Viet, Q9, HCMC",
+      })
+    );
+
+    expect(res.status).toBe(201);
+    const body = await res.json();
+    expect(body.tax_code).toBeNull();
+    expect(body.notes).toBeNull();
+  });
+
+  it("rejects an empty name", async () => {
+    const res = await POST(
+      postRequest({
+        name: "",
+        contactEmail: "sales@fpt.com.vn",
+        contactPhone: "0281234567",
+        address: "123 Nguyen Van Linh, Q7, HCMC",
+      })
+    );
+
+    expect(res.status).toBe(400);
+    const body = await res.json();
+    expect(body.error).toMatch(/name/i);
+  });
+
+  it("rejects an invalid contactEmail", async () => {
+    const res = await POST(
+      postRequest({
+        name: "FPT Trading",
+        contactEmail: "not-an-email",
+        contactPhone: "0281234567",
+        address: "123 Nguyen Van Linh, Q7, HCMC",
+      })
+    );
+
+    expect(res.status).toBe(400);
+    const body = await res.json();
+    expect(body.error).toMatch(/contactEmail/i);
+  });
+
+  it("rejects an empty contactPhone", async () => {
+    const res = await POST(
+      postRequest({
+        name: "FPT Trading",
+        contactEmail: "sales@fpt.com.vn",
+        contactPhone: "",
+        address: "123 Nguyen Van Linh, Q7, HCMC",
+      })
+    );
+
+    expect(res.status).toBe(400);
+    const body = await res.json();
+    expect(body.error).toMatch(/contactPhone/i);
+  });
+
+  it("rejects an empty address", async () => {
+    const res = await POST(
+      postRequest({
+        name: "FPT Trading",
+        contactEmail: "sales@fpt.com.vn",
+        contactPhone: "0281234567",
+        address: "",
+      })
+    );
+
+    expect(res.status).toBe(400);
+    const body = await res.json();
+    expect(body.error).toMatch(/address/i);
+  });
+
+  it("rejects an invalid JSON body", async () => {
+    const req = new Request("http://localhost/api/vendors", {
+      method: "POST",
+      headers: { "content-type": "application/json" },
+      body: "not json",
+    });
+
+    const res = await POST(req);
+    expect(res.status).toBe(400);
+    const body = await res.json();
+    expect(body.error).toMatch(/JSON/i);
+  });
+
+  it("rejects a non-object JSON body", async () => {
+    // Note: arrays are `typeof "object"` in JS, so they pass the route's
+    // object check (same behavior as /api/licenses) — use a JSON string
+    // primitive here to actually exercise the "not an object" branch.
+    const res = await POST(postRequest("not an object"));
+
+    expect(res.status).toBe(400);
+    const body = await res.json();
+    expect(body.error).toMatch(/JSON object/i);
+  });
+});
+
+describe("GET /api/vendors", () => {
+  it("lists created vendors, newest first", async () => {
+    await POST(
+      postRequest({
+        name: "Synnex FPT",
+        contactEmail: "contact@synnexfpt.com",
+        contactPhone: "0287654321",
+        address: "456 Le Van Viet, Q9, HCMC",
+      })
+    );
+    // Ensure a distinct created_at ordering even on fast filesystems/clocks.
+    await new Promise((resolve) => setTimeout(resolve, 5));
+    await POST(
+      postRequest({
+        name: "FPT Trading",
+        contactEmail: "sales@fpt.com.vn",
+        contactPhone: "0281234567",
+        address: "123 Nguyen Van Linh, Q7, HCMC",
+      })
+    );
+
+    const res = await GET();
+    expect(res.status).toBe(200);
+
+    const body = await res.json();
+    expect(Array.isArray(body)).toBe(true);
+    expect(body).toHaveLength(2);
+
+    // newest first
+    expect(body[0]).toMatchObject({ name: "FPT Trading" });
+    expect(body[1]).toMatchObject({ name: "Synnex FPT" });
+  });
+
+  it("returns an empty list when there are no vendors", async () => {
+    const res = await GET();
+    expect(res.status).toBe(200);
+    const body = await res.json();
+    expect(body).toEqual([]);
+  });
+});
+
+describe("auth gating on /api/vendors", () => {
+  // Mirrors tests/licenses.test.ts's "auth gating" block — only checks
+  // session presence, per the flat permission model (no role/permission
+  // logic).
+  it("POST /api/vendors returns 401 without a session", async () => {
+    mockedAuth.mockResolvedValue(null);
+
+    const res = await POST(
+      postRequest({
+        name: "FPT Trading",
+        contactEmail: "sales@fpt.com.vn",
+        contactPhone: "0281234567",
+        address: "123 Nguyen Van Linh, Q7, HCMC",
+      })
+    );
+
+    expect(res.status).toBe(401);
+    const body = await res.json();
+    expect(body).toEqual({ error: "Unauthorized" });
+
+    // And it must not have created anything.
+    const remaining = await prisma.vendor.findMany();
+    expect(remaining).toHaveLength(0);
+  });
+
+  it("GET /api/vendors returns 401 without a session", async () => {
+    mockedAuth.mockResolvedValue(null);
+
+    const res = await GET();
+
+    expect(res.status).toBe(401);
+    const body = await res.json();
+    expect(body).toEqual({ error: "Unauthorized" });
+  });
+});