mpp-spt-lifecycle

name	mpp-spt-lifecycle
description	Implement Shared Payment Token (SPT) lifecycle management for MPP — creation, usage, deactivation, webhook events, and reconciliation. Use when building the fiat/card payment flow within MPP using Stripe SPTs.
allowed-tools	Read, Write, Edit, Bash, Grep, Glob, WebSearch, WebFetch

MPP Shared Payment Token (SPT) Lifecycle

Before writing code

Fetch live docs:

1. Fetch https://docs.stripe.com/agentic-commerce/concepts/shared-payment-tokens for the canonical SPT documentation
2. Web-search site:docs.stripe.com shared_payment granted_token API for SPT API endpoints
3. Web-search stripe shared payment token webhook events for SPT event schemas
4. Fetch https://docs.stripe.com/payments/machine/mpp for SPT usage within MPP context

Conceptual Architecture

What SPTs Are

Shared Payment Tokens are one-time payment tokens scoped to a specific merchant and exact amount. They are the mechanism by which card/fiat payments work within the MPP protocol. The agent never handles raw card data — SPTs abstract away PCI-sensitive information.

SPT Lifecycle

1. Agent → Stripe:    Create SPT (scoped to merchant + amount + expiry)
2. Stripe → Agent:    Returns spt_... token
3. Agent → Server:    Sends SPT as payment credential in 402 flow
4. Server → Stripe:   Creates PaymentIntent with SPT
5. Stripe → Server:   Payment confirmed
6. Stripe → Agent:    Webhook: shared_payment.issued_token.used
7. Stripe → Server:   Webhook: shared_payment.granted_token.used

SPT Creation (Agent-Side)

POST /v1/test_helpers/shared_payment/granted_tokens

Parameters:
  payment_method: pm_card_visa
  usage_limits[currency]: usd
  usage_limits[max_amount]: 1000           # $10.00 in cents
  usage_limits[expires_at]: <unix_ts>      # Expiration timestamp
  seller_details[network_id]: <seller_id>  # Merchant's network ID
  seller_details[external_id]: <ext_id>    # Optional external reference

SPT Consumption (Server-Side)

POST /v1/payment_intents

Parameters:
  amount: 500                              # $5.00 in cents
  currency: usd
  shared_payment_granted_token: spt_...
  confirm: true

When confirmed, Stripe clones the original PaymentMethod and processes the charge.

SPT Retrieval

GET /v1/shared_payment/granted_tokens/{id}

Returns limited payment method details (card brand, last four digits) and usage restrictions.

SPT Webhook Events

Event	Recipient	Trigger	Key Fields
shared_payment.granted_token.used	Seller (Server)	SPT successfully consumed	token_id, amount, currency
shared_payment.granted_token.deactivated	Seller (Server)	SPT revoked or expired	token_id, reason
shared_payment.issued_token.used	Agent	Seller consumed the SPT	token_id, amount
shared_payment.issued_token.deactivated	Agent	SPT no longer valid	token_id, reason

Webhook Listener (Server-Side)

app.post('/webhooks/stripe', async (c) => {
  const sig = c.req.header('stripe-signature');
  const event = stripe.webhooks.constructEvent(
    await c.req.text(),
    sig,
    process.env.STRIPE_WEBHOOK_SECRET
  );

  switch (event.type) {
    case 'shared_payment.granted_token.used':
      // SPT was successfully consumed — update records
      break;
    case 'shared_payment.granted_token.deactivated':
      // SPT expired or was revoked — clean up
      break;
  }
});

SPT Constraints

Constraint	Purpose
max_amount	Transaction cannot exceed this (minor units)
currency	Token only works in specified currency
expires_at	Token invalid after this timestamp
network_id	Only specified merchant can use it
external_id	Additional merchant scoping

Deactivation Reasons

SPTs can be deactivated for:

• Expiration — expires_at passed
• Usage — Successfully consumed (single-use)
• Revocation — Agent or platform revoked the token
• Fraud — Flagged by Stripe's fraud detection

Reconciliation

• Match SPT creation events to consumption events
• Track SPT lifecycle (created → used → settled) for accounting
• Monitor deactivation rates (high expiration rate may mean TTL is too short)
• Cross-reference SPT usage with PaymentIntent events

Best Practices

• Set max_amount to the exact payment amount — never higher
• Set short expiration times (minutes, not hours)
• Implement idempotent webhook handlers (same event may be delivered multiple times)
• Verify webhook signatures using stripe.webhooks.constructEvent()
• Log SPT lifecycle events for audit trail (token IDs only, not sensitive data)
• Handle race conditions between SPT creation and consumption
• Monitor SPT deactivation webhook for cleanup

Fetch the latest Stripe SPT API documentation for exact endpoint paths, webhook event schemas, and error codes before implementing.