diff --git a/services/platform-service/src/lib/auto-register.test.ts b/services/platform-service/src/lib/auto-register.test.ts
new file mode 100644
index 00000000..c9e37b70
--- /dev/null
+++ b/services/platform-service/src/lib/auto-register.test.ts
@@ -0,0 +1,109 @@
+/**
+ * Auto-Registration tests — zero-touch product provisioning.
+ */
+
+import { describe, it, expect, beforeEach } from 'vitest';
+import { autoRegisterProduct, resetRateLimiter } from './auto-register.js';
+import { loadProductCache, isValidProduct } from '../modules/products/cache.js';
+import * as productRepo from '../modules/products/repository.js';
+
+// Seed a known product so cache isn't empty
+async function seedProduct(id: string): Promise<void> {
+  await productRepo.create({
+    id,
+    productId: id,
+    displayName: id.charAt(0).toUpperCase() + id.slice(1),
+    licensePrefix: id.slice(0, 4).toUpperCase(),
+    packageName: '',
+    defaultPlan: 'free',
+    trialDays: 14,
+    deviceLimits: { free: 1, pro: 3, enterprise: 10 },
+    websiteUrl: '',
+    status: 'active',
+    createdAt: new Date().toISOString(),
+    updatedAt: new Date().toISOString(),
+  });
+  await loadProductCache();
+}
+
+describe('autoRegisterProduct', () => {
+  beforeEach(async () => {
+    resetRateLimiter();
+    // Ensure cache is loaded (even if empty)
+    await loadProductCache();
+  });
+
+  it('should auto-register an unknown productId', async () => {
+    const result = await autoRegisterProduct('new-test-product', 'user-123');
+
+    expect(result.registered).toBe(true);
+    expect(result.product).toBeDefined();
+    expect(result.product!.productId).toBe('new-test-product');
+    expect(result.product!.status).toBe('active');
+    expect(result.product!.displayName).toBe('New Test Product');
+    expect(result.product!.defaultPlan).toBe('free');
+    expect(result.product!.trialDays).toBe(14);
+
+    // Cache should now include the new product
+    expect(isValidProduct('new-test-product')).toBe(true);
+  });
+
+  it('should return already exists for a known product', async () => {
+    await seedProduct('existing-prod');
+
+    const result = await autoRegisterProduct('existing-prod', 'user-456');
+
+    expect(result.registered).toBe(false);
+    expect(result.reason).toBe('Already exists');
+    expect(result.product).toBeDefined();
+  });
+
+  it('should reject invalid productId format — uppercase', async () => {
+    const result = await autoRegisterProduct('BadProduct', 'user-123');
+
+    expect(result.registered).toBe(false);
+    expect(result.reason).toBe('Invalid productId format');
+  });
+
+  it('should reject invalid productId format — special characters', async () => {
+    const result = await autoRegisterProduct('bad.product!', 'user-123');
+
+    expect(result.registered).toBe(false);
+    expect(result.reason).toBe('Invalid productId format');
+  });
+
+  it('should reject empty productId', async () => {
+    const result = await autoRegisterProduct('', 'user-123');
+
+    expect(result.registered).toBe(false);
+    expect(result.reason).toBe('Invalid productId format');
+  });
+
+  it('should reject productId exceeding max length', async () => {
+    const longId = 'a'.repeat(65);
+    const result = await autoRegisterProduct(longId, 'user-123');
+
+    expect(result.registered).toBe(false);
+    expect(result.reason).toBe('Invalid productId format');
+  });
+
+  it('should rate limit after max registrations', async () => {
+    // Register 10 products (the max)
+    for (let i = 0; i < 10; i++) {
+      const result = await autoRegisterProduct(`rate-limit-test-${i}`, 'user-123');
+      expect(result.registered).toBe(true);
+    }
+
+    // 11th should be rate limited
+    const result = await autoRegisterProduct('rate-limit-test-overflow', 'user-123');
+    expect(result.registered).toBe(false);
+    expect(result.reason).toBe('Auto-registration rate limit exceeded');
+  });
+
+  it('should generate correct licensePrefix from productId', async () => {
+    const result = await autoRegisterProduct('my-cool-app', 'user-123');
+
+    expect(result.registered).toBe(true);
+    expect(result.product!.licensePrefix).toBe('MYCOOLAP');
+  });
+});
diff --git a/services/platform-service/src/lib/auto-register.ts b/services/platform-service/src/lib/auto-register.ts
new file mode 100644
index 00000000..370c1bdb
--- /dev/null
+++ b/services/platform-service/src/lib/auto-register.ts
@@ -0,0 +1,146 @@
+/**
+ * Auto-Registration — zero-touch product provisioning.
+ *
+ * When a request arrives with an unknown productId AND a valid JWT,
+ * auto-create a minimal ProductDoc instead of rejecting the request.
+ * This enables new products to start using platform-service immediately
+ * without manual admin setup.
+ *
+ * Security:
+ *  - Requires valid JWT (unauthenticated requests still rejected)
+ *  - Rate-limited: max 10 auto-registrations per minute
+ *  - productId must match /^[a-z0-9_-]+$/ (same as CreateProductSchema)
+ *  - Audit-logged as `product.auto_registered`
+ */
+
+import * as productRepo from '../modules/products/repository.js';
+import { loadProductCache } from '../modules/products/cache.js';
+import * as auditRepo from '../modules/audit/repository.js';
+import type { ProductDoc } from '../modules/products/types.js';
+
+const PRODUCT_ID_PATTERN = /^[a-z0-9_-]+$/;
+const MAX_PRODUCT_ID_LENGTH = 64;
+
+// ── Rate limiter (sliding window, in-process) ───────────────────
+
+const RATE_LIMIT_WINDOW_MS = 60_000; // 1 minute
+const RATE_LIMIT_MAX = 10;
+const registrationTimestamps: number[] = [];
+
+function isRateLimited(): boolean {
+  const now = Date.now();
+  // Prune expired entries
+  while (
+    registrationTimestamps.length > 0 &&
+    registrationTimestamps[0]! < now - RATE_LIMIT_WINDOW_MS
+  ) {
+    registrationTimestamps.shift();
+  }
+  return registrationTimestamps.length >= RATE_LIMIT_MAX;
+}
+
+function recordRegistration(): void {
+  registrationTimestamps.push(Date.now());
+}
+
+/** Reset rate limiter (for testing). */
+export function resetRateLimiter(): void {
+  registrationTimestamps.length = 0;
+}
+
+// ── Auto-Registration ───────────────────────────────────────────
+
+export interface AutoRegisterResult {
+  registered: boolean;
+  product?: ProductDoc;
+  reason?: string;
+}
+
+/**
+ * Attempt to auto-register an unknown productId.
+ *
+ * @param productId  The unknown product identifier
+ * @param userId     The authenticated user's ID (from JWT)
+ * @returns Result indicating whether registration succeeded
+ */
+export async function autoRegisterProduct(
+  productId: string,
+  userId: string
+): Promise<AutoRegisterResult> {
+  // Validate productId format
+  if (
+    !productId ||
+    productId.length > MAX_PRODUCT_ID_LENGTH ||
+    !PRODUCT_ID_PATTERN.test(productId)
+  ) {
+    return { registered: false, reason: 'Invalid productId format' };
+  }
+
+  // Rate limit check
+  if (isRateLimited()) {
+    return { registered: false, reason: 'Auto-registration rate limit exceeded' };
+  }
+
+  // Double-check it doesn't already exist (race condition guard)
+  const existing = await productRepo.getById(productId);
+  if (existing) {
+    // Already exists — just refresh cache and proceed
+    await loadProductCache();
+    return { registered: false, product: existing, reason: 'Already exists' };
+  }
+
+  // Build minimal product doc
+  const now = new Date().toISOString();
+  const displayName = productId.replace(/[-_]/g, ' ').replace(/\b\w/g, c => c.toUpperCase());
+  const licensePrefix = productId.replace(/[-_]/g, '').slice(0, 8).toUpperCase() || 'PROD';
+
+  const doc: ProductDoc = {
+    id: productId,
+    productId,
+    displayName,
+    licensePrefix,
+    packageName: '',
+    defaultPlan: 'free',
+    trialDays: 14,
+    deviceLimits: { free: 1, pro: 3, enterprise: 10 },
+    websiteUrl: '',
+    status: 'active',
+    createdAt: now,
+    updatedAt: now,
+  };
+
+  try {
+    const created = await productRepo.create(doc);
+    await loadProductCache();
+    recordRegistration();
+
+    // Audit log (best-effort — don't fail if audit write fails)
+    try {
+      await auditRepo.create({
+        id: `audit_${Date.now()}_${Math.random().toString(36).slice(2, 8)}`,
+        productId,
+        userId,
+        action: 'product.auto_registered',
+        category: 'product',
+        details: {
+          displayName: created.displayName,
+          registeredBy: userId,
+          method: 'auto-registration',
+        },
+        createdAt: now,
+      });
+    } catch {
+      // Best-effort audit
+    }
+
+    return { registered: true, product: created };
+  } catch (err) {
+    // If create fails due to conflict (race), treat as success
+    const message = err instanceof Error ? err.message : 'Unknown error';
+    if (message.includes('Conflict') || message.includes('409')) {
+      await loadProductCache();
+      return { registered: false, reason: 'Concurrent registration' };
+    }
+    return { registered: false, reason: message };
+  }
+}
diff --git a/services/platform-service/src/lib/request-context.ts b/services/platform-service/src/lib/request-context.ts
index 29c24548..ff39d7f6 100644
--- a/services/platform-service/src/lib/request-context.ts
+++ b/services/platform-service/src/lib/request-context.ts
@@ -13,6 +13,7 @@ import type { FastifyRequest } from 'fastify';
 import { BadRequestError } from './errors.js';
 import { isValidProduct, getProduct } from '../modules/products/cache.js';
 import type { ProductDoc } from '../modules/products/types.js';
+import { autoRegisterProduct } from './auto-register.js';
 
 /** JWT payload shape attached to req by the onRequest hook (see Commit 3). */
 export interface JwtPayload {
@@ -35,6 +36,44 @@ declare module 'fastify' {
  * Priority: JWT token > X-Product-Id header > env fallback (dev only).
  * Validates the product exists in the registry but does NOT check status.
  */
+export async function extractProductIdAsync(req: FastifyRequest): Promise<string> {
+  // 1. From JWT (set during login/register, attached by onRequest hook)
+  let id = req.jwtPayload?.productId;
+
+  // 2. From header (unauthenticated requests like license activation)
+  if (!id) {
+    const header = req.headers['x-product-id'];
+    if (typeof header === 'string' && header.length > 0) id = header;
+  }
+
+  // 3. Fallback to env var (backward compat during migration, dev only)
+  if (!id) {
+    const envFallback = process.env.PRODUCT_ID;
+    if (envFallback) id = envFallback;
+  }
+
+  if (!id) throw new BadRequestError('productId is required (via JWT or X-Product-Id header)');
+
+  // Auto-register unknown products when requester has a valid JWT
+  if (!isValidProduct(id) && req.jwtPayload?.sub) {
+    const result = await autoRegisterProduct(id, req.jwtPayload.sub);
+    if (
+      !result.registered &&
+      result.reason !== 'Already exists' &&
+      result.reason !== 'Concurrent registration'
+    ) {
+      throw new BadRequestError(
+        `Unknown product: ${id} (auto-registration failed: ${result.reason})`
+      );
+    }
+  } else if (!isValidProduct(id)) {
+    throw new BadRequestError(`Unknown product: ${id}`);
+  }
+
+  return id;
+}
+
+/** Synchronous wrapper kept for backward compatibility on hot paths. */
 function extractProductId(req: FastifyRequest): string {
   // 1. From JWT (set during login/register, attached by onRequest hook)
   let id = req.jwtPayload?.productId;