diff --git a/tests/server/api/free-signup-flow.test.js b/tests/server/api/free-signup-flow.test.js
new file mode 100644
index 0000000..c7789ad
--- /dev/null
+++ b/tests/server/api/free-signup-flow.test.js
@@ -0,0 +1,156 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+
+import Member from '../../../server/models/member.js'
+import { createHelcimCustomer } from '../../../server/utils/helcim.js'
+import customerHandler from '../../../server/api/helcim/customer.post.js'
+import subscriptionHandler from '../../../server/api/helcim/subscription.post.js'
+import { resetRateLimit } from '../../../server/utils/rateLimit.js'
+import { sendWelcomeEmail } from '../../../server/utils/resend.js'
+import { createMockEvent } from '../helpers/createMockEvent.js'
+
+// IMPORTANT: do NOT mock server/utils/auth.js. This test exists to verify the
+// real bridge-cookie hand-off between the two handlers. Mocking auth would
+// hide the exact regression we're guarding against (setPaymentBridgeCookie
+// being skipped for $0 signups while subscription.post.js still requires
+// either a bridge cookie or a verified session).
+
+vi.mock('../../../server/models/member.js', () => ({
+  default: {
+    findOne: vi.fn(),
+    create: vi.fn(),
+    findByIdAndUpdate: vi.fn(),
+    findById: vi.fn(),
+    findOneAndUpdate: vi.fn()
+  }
+}))
+vi.mock('../../../server/utils/mongoose.js', () => ({ connectDB: vi.fn() }))
+vi.mock('../../../server/utils/helcim.js', () => ({
+  createHelcimCustomer: vi.fn(),
+  createHelcimSubscription: vi.fn(),
+  generateIdempotencyKey: vi.fn().mockReturnValue('idem-1'),
+  listHelcimCustomerTransactions: vi.fn().mockResolvedValue([])
+}))
+vi.mock('../../../server/utils/magicLink.js', () => ({
+  sendMagicLink: vi.fn().mockResolvedValue(undefined)
+}))
+vi.mock('../../../server/utils/resend.js', () => ({
+  sendWelcomeEmail: vi.fn().mockResolvedValue({ success: true })
+}))
+vi.mock('../../../server/utils/slack.ts', () => ({
+  getSlackService: vi.fn().mockReturnValue(null)
+}))
+vi.mock('../../../server/utils/payments.js', () => ({
+  upsertPaymentFromHelcim: vi.fn().mockResolvedValue({ created: true })
+}))
+
+vi.stubGlobal('helcimCustomerSchema', {})
+vi.stubGlobal('helcimSubscriptionSchema', {})
+
+const ALLOWED_ORIGIN = 'https://ghostguild.test'
+const MEMBER_ID = '69f231152939bf109ac79d83'
+
+function extractBridgeCookie(event) {
+  const setCookie = event.node.res.getHeader('set-cookie')
+  const cookies = Array.isArray(setCookie) ? setCookie : [setCookie].filter(Boolean)
+  const match = cookies.find(c => typeof c === 'string' && c.startsWith('payment-bridge='))
+  if (!match) return null
+  return match.match(/payment-bridge=([^;]+)/)[1]
+}
+
+describe('signup → subscription bridge-cookie hand-off', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+    resetRateLimit()
+    process.env.BASE_URL = ALLOWED_ORIGIN
+
+    createHelcimCustomer.mockResolvedValue({ id: 999, customerCode: 'CST999' })
+    Member.findOne.mockResolvedValue(null)
+    Member.create.mockResolvedValue({
+      _id: MEMBER_ID,
+      email: 'free@example.com',
+      name: 'Free User',
+      circle: 'community',
+      contributionAmount: 0,
+      status: 'pending_payment'
+    })
+  })
+
+  it('$0 signup: customer endpoint issues a bridge cookie that subscription endpoint accepts', async () => {
+    // --- Step 1: POST /api/helcim/customer (free tier) ---
+    const customerEvent = createMockEvent({
+      method: 'POST',
+      path: '/api/helcim/customer',
+      headers: { origin: ALLOWED_ORIGIN },
+      body: {
+        name: 'Free User',
+        email: 'free@example.com',
+        circle: 'community',
+        contributionAmount: 0,
+        agreedToGuidelines: true,
+        billingAddress: { country: 'CA' }
+      }
+    })
+
+    const result1 = await customerHandler(customerEvent)
+    expect(result1.success).toBe(true)
+    expect(result1.member.status).toBe('pending_payment')
+
+    // The regression: prior code skipped setPaymentBridgeCookie when
+    // contributionAmount === 0, leaving the user unable to complete
+    // subscription activation in the same flow.
+    const bridgeToken = extractBridgeCookie(customerEvent)
+    expect(bridgeToken, 'payment-bridge cookie missing on $0 signup').toBeTruthy()
+
+    // --- Step 2: POST /api/helcim/subscription (free tier) ---
+    Member.findOneAndUpdate.mockResolvedValue({ _id: MEMBER_ID, status: 'pending_payment' })
+    Member.findById.mockResolvedValue({
+      _id: MEMBER_ID,
+      email: 'free@example.com',
+      name: 'Free User',
+      circle: 'community',
+      contributionAmount: 0,
+      status: 'active'
+    })
+
+    const subscriptionEvent = createMockEvent({
+      method: 'POST',
+      path: '/api/helcim/subscription',
+      headers: { origin: ALLOWED_ORIGIN },
+      cookies: { 'payment-bridge': bridgeToken },
+      body: {
+        customerId: 999,
+        customerCode: 'CST999',
+        contributionAmount: 0,
+        cadence: 'monthly',
+        cardToken: null
+      }
+    })
+
+    const result2 = await subscriptionHandler(subscriptionEvent)
+    expect(result2.success).toBe(true)
+    expect(result2.member.status).toBe('active')
+    expect(sendWelcomeEmail).toHaveBeenCalledTimes(1)
+  })
+
+  it('$0 signup with no bridge cookie carried forward → subscription returns 401', async () => {
+    // Sanity check: confirms the auth gate still rejects fresh, unauthenticated
+    // calls to /api/helcim/subscription. If this ever stops failing, the
+    // bridge cookie has stopped being load-bearing and the gate is open.
+    const subscriptionEvent = createMockEvent({
+      method: 'POST',
+      path: '/api/helcim/subscription',
+      headers: { origin: ALLOWED_ORIGIN },
+      body: {
+        customerId: 999,
+        customerCode: 'CST999',
+        contributionAmount: 0,
+        cadence: 'monthly',
+        cardToken: null
+      }
+    })
+
+    await expect(subscriptionHandler(subscriptionEvent)).rejects.toMatchObject({
+      statusCode: 401
+    })
+  })
+})