diff --git a/prisma/migrations/20260304104214_initial_schema/migration.sql b/prisma/migrations/20260304104214_initial_schema/migration.sql
new file mode 100644
index 0000000..66b4fe5
--- /dev/null
+++ b/prisma/migrations/20260304104214_initial_schema/migration.sql
@@ -0,0 +1,60 @@
+-- =============================================================================
+-- Initial Schema Migration
+-- Created as a baseline to capture the state created by `prisma db push`
+-- during project initialization (01-01-PLAN.md).
+--
+-- This migration is marked as applied without running it (baseline approach)
+-- since the schema already exists in the database from the initial db push.
+-- =============================================================================
+
+-- CreateEnum
+CREATE TYPE "TenantStatus" AS ENUM ('ACTIVE', 'PENDING_SUSPENSION', 'SUSPENDED');
+
+-- CreateEnum
+CREATE TYPE "Role" AS ENUM ('ADMIN', 'OFFICE_STAFF', 'COLLECTOR', 'TECHNICIAN', 'CLIENT');
+
+-- CreateTable
+CREATE TABLE "Tenant" (
+    "id" TEXT NOT NULL,
+    "name" TEXT NOT NULL,
+    "slug" TEXT NOT NULL,
+    "ownerEmail" TEXT NOT NULL,
+    "businessAddress" TEXT,
+    "contactPhone" TEXT,
+    "status" "TenantStatus" NOT NULL DEFAULT 'ACTIVE',
+    "suspendedAt" TIMESTAMP(3),
+    "gracePeriodEndsAt" TIMESTAMP(3),
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" TIMESTAMP(3) NOT NULL,
+
+    CONSTRAINT "Tenant_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateTable
+CREATE TABLE "User" (
+    "id" TEXT NOT NULL,
+    "email" TEXT NOT NULL,
+    "passwordHash" TEXT NOT NULL,
+    "firstName" TEXT NOT NULL,
+    "lastName" TEXT NOT NULL,
+    "tenantId" TEXT,
+    "roles" "Role"[],
+    "isActive" BOOLEAN NOT NULL DEFAULT true,
+    "isSuperAdmin" BOOLEAN NOT NULL DEFAULT false,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" TIMESTAMP(3) NOT NULL,
+
+    CONSTRAINT "User_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE UNIQUE INDEX "Tenant_slug_key" ON "Tenant"("slug");
+
+-- CreateIndex
+CREATE INDEX "User_tenantId_idx" ON "User"("tenantId");
+
+-- CreateIndex
+CREATE UNIQUE INDEX "User_email_tenantId_key" ON "User"("email", "tenantId");
+
+-- AddForeignKey
+ALTER TABLE "User" ADD CONSTRAINT "User_tenantId_fkey" FOREIGN KEY ("tenantId") REFERENCES "Tenant"("id") ON DELETE CASCADE ON UPDATE CASCADE;
diff --git a/prisma/migrations/20260304104245_add_rls_policies/migration.sql b/prisma/migrations/20260304104245_add_rls_policies/migration.sql
new file mode 100644
index 0000000..3be8ae8
--- /dev/null
+++ b/prisma/migrations/20260304104245_add_rls_policies/migration.sql
@@ -0,0 +1,41 @@
+-- =============================================================================
+-- PostgreSQL Row-Level Security (RLS) Policies
+-- Defense-in-depth tenant isolation for NetForge
+-- =============================================================================
+--
+-- ARCHITECTURE NOTE:
+-- The primary multi-tenancy enforcement is at the application layer via
+-- Prisma query extensions in src/lib/prisma-tenant.ts (withTenantContext).
+--
+-- RLS policies here serve as DEFENSE-IN-DEPTH:
+-- - They catch bugs where application code bypasses the Prisma middleware
+-- - They provide an independent enforcement layer at the database level
+-- - They document data isolation intent in the database schema itself
+--
+-- IMPORTANT: The Prisma client connects as the database OWNER, which by
+-- default bypasses RLS (PostgreSQL superusers and table owners bypass RLS
+-- unless FORCE ROW LEVEL SECURITY is set on the table). This means these
+-- policies will NOT block queries from the standard Prisma client unless
+-- FORCE ROW LEVEL SECURITY is enabled, or a non-owner role is used.
+--
+-- To enforce RLS for a query, use setTenantRLS() from src/lib/prisma-tenant.ts
+-- within a transaction before executing queries. This sets the session variable
+-- app.current_tenant_id which the policy USING clause reads.
+-- =============================================================================
+
+-- Enable RLS on the User table
+ALTER TABLE "User" ENABLE ROW LEVEL SECURITY;
+
+-- Policy: tenant_isolation_user
+-- Restricts access to rows matching the current tenant context.
+-- The app.current_tenant_id session variable is set by setTenantRLS().
+-- When no tenant context is set (super-admin operations), all rows are visible.
+CREATE POLICY tenant_isolation_user ON "User"
+  USING (
+    "tenantId" = current_setting('app.current_tenant_id', true)::text
+    OR current_setting('app.current_tenant_id', true) IS NULL
+    OR current_setting('app.current_tenant_id', true) = ''
+  )
+  WITH CHECK (
+    "tenantId" = current_setting('app.current_tenant_id', true)::text
+  );
\ No newline at end of file
diff --git a/prisma/migrations/migration_lock.toml b/prisma/migrations/migration_lock.toml
new file mode 100644
index 0000000..044d57c
--- /dev/null
+++ b/prisma/migrations/migration_lock.toml
@@ -0,0 +1,3 @@
+# Please do not edit this file manually
+# It should be added in your version-control system (e.g., Git)
+provider = "postgresql"
diff --git a/src/lib/__tests__/tenant-isolation.test.ts b/src/lib/__tests__/tenant-isolation.test.ts
new file mode 100644
index 0000000..738888b
--- /dev/null
+++ b/src/lib/__tests__/tenant-isolation.test.ts
@@ -0,0 +1,241 @@
+/**
+ * Tenant Isolation Integration Tests
+ *
+ * These tests require a live PostgreSQL database connection.
+ * They verify that withTenantContext() prevents cross-tenant data leakage.
+ *
+ * WHAT IS TESTED:
+ * - Queries scoped to Tenant A return ZERO rows from Tenant B
+ * - Queries scoped to Tenant B return ZERO rows from Tenant A
+ * - createUser under Tenant A context auto-sets tenantId to Tenant A
+ * - Reading a specific Tenant B user by ID under Tenant A context returns null
+ *
+ * ISOLATION STRATEGY:
+ * Each test run creates fresh tenants/users with unique IDs.
+ * afterAll() cleans up all test data by deleting the test tenants
+ * (cascade deletes Users through the FK constraint).
+ */
+
+import { prisma } from "@/lib/prisma";
+import { withTenantContext } from "@/lib/prisma-tenant";
+import { TenantStatus } from "@prisma/client";
+
+// ---------------------------------------------------------------------------
+// Test data: created in beforeAll, cleaned up in afterAll
+// ---------------------------------------------------------------------------
+
+let tenantAId: string;
+let tenantBId: string;
+let userAId: string;
+let userBId: string;
+
+const TENANT_A_SLUG = `test-tenant-a-${Date.now()}`;
+const TENANT_B_SLUG = `test-tenant-b-${Date.now()}`;
+const USER_A_EMAIL = `user-a-${Date.now()}@test.example`;
+const USER_B_EMAIL = `user-b-${Date.now()}@test.example`;
+
+describe("Tenant Isolation (integration)", () => {
+  beforeAll(async () => {
+    // Create Tenant A with one admin user
+    const tenantA = await prisma.tenant.create({
+      data: {
+        name: "Test Tenant A",
+        slug: TENANT_A_SLUG,
+        ownerEmail: USER_A_EMAIL,
+        status: TenantStatus.ACTIVE,
+      },
+    });
+    tenantAId = tenantA.id;
+
+    const userA = await prisma.user.create({
+      data: {
+        email: USER_A_EMAIL,
+        passwordHash: "hashed-password-a",
+        firstName: "Alice",
+        lastName: "Tenant",
+        tenantId: tenantAId,
+        roles: ["ADMIN"],
+        isActive: true,
+      },
+    });
+    userAId = userA.id;
+
+    // Create Tenant B with one admin user
+    const tenantB = await prisma.tenant.create({
+      data: {
+        name: "Test Tenant B",
+        slug: TENANT_B_SLUG,
+        ownerEmail: USER_B_EMAIL,
+        status: TenantStatus.ACTIVE,
+      },
+    });
+    tenantBId = tenantB.id;
+
+    const userB = await prisma.user.create({
+      data: {
+        email: USER_B_EMAIL,
+        passwordHash: "hashed-password-b",
+        firstName: "Bob",
+        lastName: "Tenant",
+        tenantId: tenantBId,
+        roles: ["ADMIN"],
+        isActive: true,
+      },
+    });
+    userBId = userB.id;
+  });
+
+  afterAll(async () => {
+    // Delete tenants (cascade deletes their users via FK)
+    if (tenantAId) {
+      await prisma.tenant.delete({ where: { id: tenantAId } }).catch(() => {});
+    }
+    if (tenantBId) {
+      await prisma.tenant.delete({ where: { id: tenantBId } }).catch(() => {});
+    }
+    await prisma.$disconnect();
+  });
+
+  // -------------------------------------------------------------------------
+  // Test 1: Tenant A context returns only Tenant A's users
+  // -------------------------------------------------------------------------
+  it("Test 1: Tenant A context returns only Tenant A's user (zero from Tenant B)", async () => {
+    const tenantAPrisma = withTenantContext(tenantAId);
+
+    const users = await tenantAPrisma.user.findMany();
+
+    // Should find at least the one user we created for Tenant A
+    const tenantAUsers = users.filter((u) => u.tenantId === tenantAId);
+    const tenantBUsers = users.filter((u) => u.tenantId === tenantBId);
+
+    expect(tenantAUsers.length).toBeGreaterThanOrEqual(1);
+    expect(tenantBUsers.length).toBe(0);
+
+    // Specifically verify User A is returned
+    const foundUserA = users.find((u) => u.id === userAId);
+    expect(foundUserA).toBeDefined();
+    expect(foundUserA?.email).toBe(USER_A_EMAIL);
+
+    // Verify User B is NOT in the results
+    const foundUserB = users.find((u) => u.id === userBId);
+    expect(foundUserB).toBeUndefined();
+  });
+
+  // -------------------------------------------------------------------------
+  // Test 2: Tenant B context returns only Tenant B's users
+  // -------------------------------------------------------------------------
+  it("Test 2: Tenant B context returns only Tenant B's user (zero from Tenant A)", async () => {
+    const tenantBPrisma = withTenantContext(tenantBId);
+
+    const users = await tenantBPrisma.user.findMany();
+
+    const tenantAUsers = users.filter((u) => u.tenantId === tenantAId);
+    const tenantBUsers = users.filter((u) => u.tenantId === tenantBId);
+
+    expect(tenantBUsers.length).toBeGreaterThanOrEqual(1);
+    expect(tenantAUsers.length).toBe(0);
+
+    // Specifically verify User B is returned
+    const foundUserB = users.find((u) => u.id === userBId);
+    expect(foundUserB).toBeDefined();
+    expect(foundUserB?.email).toBe(USER_B_EMAIL);
+
+    // Verify User A is NOT in the results
+    const foundUserA = users.find((u) => u.id === userAId);
+    expect(foundUserA).toBeUndefined();
+  });
+
+  // -------------------------------------------------------------------------
+  // Test 3: Creating a user under Tenant A context auto-sets tenantId
+  // -------------------------------------------------------------------------
+  it("Test 3: Creating a user with Tenant A context auto-sets tenantId to Tenant A", async () => {
+    const tenantAPrisma = withTenantContext(tenantAId);
+
+    const AUTO_EMAIL = `auto-${Date.now()}@test.example`;
+
+    const newUser = await tenantAPrisma.user.create({
+      data: {
+        email: AUTO_EMAIL,
+        passwordHash: "hashed-auto",
+        firstName: "Auto",
+        lastName: "Created",
+        roles: ["OFFICE_STAFF"],
+        isActive: true,
+        // NOTE: tenantId is intentionally NOT provided here
+        // The middleware should inject it automatically
+      },
+    });
+
+    // Verify the tenantId was automatically set to Tenant A
+    expect(newUser.tenantId).toBe(tenantAId);
+    expect(newUser.email).toBe(AUTO_EMAIL);
+
+    // Verify this user is visible through Tenant A's context
+    const foundViaA = await tenantAPrisma.user.findFirst({
+      where: { email: AUTO_EMAIL },
+    });
+    expect(foundViaA).not.toBeNull();
+    expect(foundViaA?.tenantId).toBe(tenantAId);
+
+    // Verify this user is NOT visible through Tenant B's context
+    const tenantBPrisma = withTenantContext(tenantBId);
+    const foundViaB = await tenantBPrisma.user.findFirst({
+      where: { email: AUTO_EMAIL },
+    });
+    expect(foundViaB).toBeNull();
+
+    // Cleanup the auto-created user
+    await prisma.user.delete({ where: { id: newUser.id } }).catch(() => {});
+  });
+
+  // -------------------------------------------------------------------------
+  // Test 4: Reading Tenant B's user by ID with Tenant A context returns null
+  // -------------------------------------------------------------------------
+  it("Test 4: Reading Tenant B's user by ID with Tenant A context returns null (not found)", async () => {
+    const tenantAPrisma = withTenantContext(tenantAId);
+
+    // Attempt to read Tenant B's user (userBId) through Tenant A's context
+    const result = await tenantAPrisma.user.findUnique({
+      where: { id: userBId },
+    });
+
+    // Must be null — cross-tenant access is blocked
+    expect(result).toBeNull();
+  });
+
+  // -------------------------------------------------------------------------
+  // Additional: findFirst cross-tenant access is blocked
+  // -------------------------------------------------------------------------
+  it("findFirst with Tenant A context cannot find Tenant B users by email", async () => {
+    const tenantAPrisma = withTenantContext(tenantAId);
+
+    const result = await tenantAPrisma.user.findFirst({
+      where: { email: USER_B_EMAIL },
+    });
+
+    expect(result).toBeNull();
+  });
+
+  // -------------------------------------------------------------------------
+  // Additional: count is tenant-scoped
+  // -------------------------------------------------------------------------
+  it("count() under Tenant A context only counts Tenant A's users", async () => {
+    const tenantAPrisma = withTenantContext(tenantAId);
+    const tenantBPrisma = withTenantContext(tenantBId);
+
+    const countA = await tenantAPrisma.user.count();
+    const countB = await tenantBPrisma.user.count();
+
+    // Each tenant should have exactly 1 user (the one we created in beforeAll)
+    expect(countA).toBe(1);
+    expect(countB).toBe(1);
+
+    // Total without tenant context should be 2 (both tenants' users)
+    const totalCount = await prisma.user.count({
+      where: {
+        id: { in: [userAId, userBId] },
+      },
+    });
+    expect(totalCount).toBe(2);
+  });
+});
diff --git a/src/lib/prisma-tenant.ts b/src/lib/prisma-tenant.ts
new file mode 100644
index 0000000..3fdd88f
--- /dev/null
+++ b/src/lib/prisma-tenant.ts
@@ -0,0 +1,207 @@
+import { prisma } from "@/lib/prisma";
+
+// =============================================================================
+// Tenant-Scoped Prisma Client
+// =============================================================================
+//
+// ARCHITECTURE:
+// This module provides a Prisma client extended with query-level extensions
+// that automatically inject the current tenant's ID into all reads, writes,
+// and deletes on tenant-scoped models.
+//
+// This is the PRIMARY enforcement layer for multi-tenancy.
+// PostgreSQL RLS (see migration: add-rls-policies) is DEFENSE-IN-DEPTH —
+// it catches application bugs if this middleware is somehow bypassed.
+//
+// USAGE:
+//   const tenantPrisma = withTenantContext(tenantId);
+//   const users = await tenantPrisma.user.findMany(); // auto-filters by tenantId
+//
+// EXTENDING:
+// When adding new tenant-scoped models (Subscriber, Invoice, Plan, etc.),
+// add the model name to TENANT_SCOPED_MODELS below and extend the $extends
+// block in withTenantContext() following the same pattern.
+// =============================================================================
+
+/**
+ * List of Prisma model names that are scoped to a tenant.
+ * Models NOT in this list (like Tenant itself) bypass tenant filtering.
+ *
+ * Extend this list as new models are added in later phases:
+ * e.g., "subscriber", "invoice", "servicePlan", "payment"
+ */
+export const TENANT_SCOPED_MODELS = ["user"] as const;
+
+export type TenantScopedModel = (typeof TENANT_SCOPED_MODELS)[number];
+
+/**
+ * Returns a Prisma client extended with tenant-scoped query filtering.
+ *
+ * All operations on tenant-scoped models automatically include the tenantId:
+ * - findMany / findFirst: where clause gets tenantId injected
+ * - findUnique: converted to findFirst with tenantId guard
+ * - create: data gets tenantId set
+ * - update / updateMany: where clause gets tenantId added
+ * - delete / deleteMany: where clause gets tenantId added
+ * - upsert: where clause gets tenantId added, create data gets tenantId set
+ *
+ * @param tenantId - The tenant UUID to scope all queries to
+ */
+export function withTenantContext(tenantId: string) {
+  return prisma.$extends({
+    query: {
+      user: {
+        async findMany({ args, query }) {
+          args.where = { ...args.where, tenantId };
+          return query(args);
+        },
+
+        async findFirst({ args, query }) {
+          args.where = { ...args.where, tenantId };
+          return query(args);
+        },
+
+        async findFirstOrThrow({ args, query }) {
+          args.where = { ...args.where, tenantId };
+          return query(args);
+        },
+
+        // findUnique requires an exact unique key — we can't simply inject
+        // tenantId there. Route through findFirst to enforce tenant scoping.
+        async findUnique({ args, query }) {
+          // Check if tenantId is already part of a compound unique key
+          // If so, let Prisma handle it. Otherwise, use findFirst with tenant guard.
+          if (args.where && "id" in args.where && !("tenantId" in (args.where as object))) {
+            // Use findFirst to enforce tenant boundary
+            return prisma.user.findFirst({
+              ...args,
+              where: { ...args.where, tenantId },
+            });
+          }
+          return query(args);
+        },
+
+        async findUniqueOrThrow({ args, query }) {
+          if (args.where && "id" in args.where && !("tenantId" in (args.where as object))) {
+            const result = await prisma.user.findFirst({
+              ...args,
+              where: { ...args.where, tenantId },
+            });
+            if (!result) {
+              throw new Error("Record not found");
+            }
+            return result;
+          }
+          return query(args);
+        },
+
+        async create({ args, query }) {
+          // Remove the nested `tenant` relation object when injecting tenantId
+          // (they are mutually exclusive in Prisma's UncheckedCreateInput)
+          // eslint-disable-next-line @typescript-eslint/no-unused-vars
+          const { tenant: _tenant, ...rest } = args.data as typeof args.data & { tenant?: unknown };
+          args.data = { ...rest, tenantId } as typeof args.data;
+          return query(args);
+        },
+
+        async createMany({ args, query }) {
+          if (Array.isArray(args.data)) {
+            args.data = args.data.map((item) => {
+              // eslint-disable-next-line @typescript-eslint/no-unused-vars
+              const { tenant: _t, ...rest } = item as typeof item & { tenant?: unknown };
+              return { ...rest, tenantId } as typeof item;
+            });
+          } else {
+            // eslint-disable-next-line @typescript-eslint/no-unused-vars
+            const { tenant: _t, ...rest } = args.data as typeof args.data & { tenant?: unknown };
+            args.data = { ...rest, tenantId } as typeof args.data;
+          }
+          return query(args);
+        },
+
+        async update({ args, query }) {
+          args.where = { ...args.where, tenantId };
+          return query(args);
+        },
+
+        async updateMany({ args, query }) {
+          args.where = { ...args.where, tenantId };
+          return query(args);
+        },
+
+        async delete({ args, query }) {
+          args.where = { ...args.where, tenantId };
+          return query(args);
+        },
+
+        async deleteMany({ args, query }) {
+          args.where = { ...args.where, tenantId };
+          return query(args);
+        },
+
+        async upsert({ args, query }) {
+          args.where = { ...args.where, tenantId } as typeof args.where;
+          // eslint-disable-next-line @typescript-eslint/no-unused-vars
+          const { tenant: _t, ...createRest } = args.create as typeof args.create & { tenant?: unknown };
+          args.create = { ...createRest, tenantId } as typeof args.create;
+          return query(args);
+        },
+
+        async count({ args, query }) {
+          args.where = { ...args.where, tenantId };
+          return query(args);
+        },
+
+        async aggregate({ args, query }) {
+          args.where = { ...args.where, tenantId };
+          return query(args);
+        },
+
+        async groupBy({ args, query }) {
+          args.where = { ...args.where, tenantId };
+          return query(args);
+        },
+      },
+    },
+  });
+}
+
+/**
+ * Alias for withTenantContext — exported under both names as per plan spec.
+ * Use either name; they are identical.
+ */
+export const createTenantPrisma = withTenantContext;
+
+/**
+ * Sets the PostgreSQL session variable used by RLS policies for the duration
+ * of the provided transaction or connection.
+ *
+ * RLS ARCHITECTURE NOTE:
+ * The Prisma client connects as the database OWNER, which bypasses RLS
+ * by default (PostgreSQL superusers and table owners bypass RLS unless
+ * FORCE ROW LEVEL SECURITY is set). This means RLS is NOT the primary
+ * enforcement — withTenantContext() (application-level Prisma extensions)
+ * is the primary enforcement layer.
+ *
+ * This function enables RLS enforcement for code paths that explicitly opt in,
+ * or in future scenarios where a non-owner role is used for queries.
+ *
+ * Usage (inside a Prisma transaction):
+ *   await prisma.$transaction(async (tx) => {
+ *     await setTenantRLS(tx, tenantId);
+ *     // ... queries here will be RLS-enforced
+ *   });
+ *
+ * @param tx - A Prisma client or transaction client
+ * @param tenantId - The tenant UUID to set as the current RLS context
+ */
+export async function setTenantRLS(
+  tx: { $executeRawUnsafe: (query: string, ...args: unknown[]) => Promise<unknown> },
+  tenantId: string
+): Promise<void> {
+  // SET LOCAL scopes the variable to the current transaction
+  await tx.$executeRawUnsafe(
+    `SET LOCAL "app.current_tenant_id" = $1`,
+    tenantId
+  );
+}