acp-orders-webhooks

name	acp-orders-webhooks
description	Implement ACP order lifecycle management and webhook event delivery. Use when building order creation, status tracking, fulfillment updates, post-purchase adjustments, and HMAC-signed webhook emission.
allowed-tools	Read, Write, Edit, Bash, Grep, Glob, WebSearch, WebFetch

ACP Orders & Webhooks

Before writing code

Fetch live docs:

1. Web-search site:github.com agentic-commerce-protocol rfcs orders for the orders RFC
2. Fetch https://developers.openai.com/commerce/guides/key-concepts/ for order lifecycle details
3. Web-search site:github.com agentic-commerce-protocol examples orders for order webhook examples
4. Web-search site:docs.stripe.com agentic-commerce webhook for Stripe webhook guidance

Conceptual Architecture

Order Lifecycle

After checkout completion, the order moves through these statuses:

created → confirmed → manual_review → processing → shipped → delivered
    |         |            |              |            |          |
    +─────────+────────────+──────────────+────────────+──────────+→ canceled

7 statuses:

• created — Order placed, payment captured
• confirmed — Merchant acknowledged the order
• manual_review — Requires human review (fraud, compliance)
• processing — Being prepared for fulfillment
• shipped — Handed to carrier (physical) or access granted (digital)
• delivered — Buyer received the goods
• canceled — Order canceled at any stage

Webhook Events

Merchants emit two event types to the agent platform:

• order_created — Fired after successful checkout completion
• order_updated — Fired on any order status change or update

Webhook Payload

Each webhook event contains:

• Order ID
• Checkout session ID
• Current order status
• Order permalink URL (for buyer to view)
• Fulfillment details (tracking, carrier, delivery windows)
• Line items
• Totals
• Timestamps

HMAC Webhook Signatures

All webhook events MUST be signed:

• Algorithm: HMAC-SHA256
• Header: Merchant-Signature (or as specified in the latest spec)
• Key: Shared secret obtained during onboarding
• Payload: Raw request body (canonical JSON)
• Verification: Timing-safe comparison to prevent timing attacks

Post-Purchase Order Adjustments

ACP supports adjustments after order creation:

Type	Description
refund	Full refund
partial_refund	Partial amount refund
store_credit	Refund as store credit
return	Buyer returns goods
exchange	Swap for different item
cancellation	Order cancellation
dispute	Buyer disputes charge
chargeback	PSP-initiated chargeback

Each adjustment has its own status: pending, completed, failed.

Order Object

The order contains:

• id — Unique order identifier
• checkout_session_id — Links back to the checkout session
• permalink_url — Buyer-facing order page

Best Practices

• Emit order_created immediately after payment capture
• Emit order_updated for every status transition
• Include all current fulfillment details in each webhook
• Use idempotent webhook delivery (include event ID for deduplication)
• Implement retry logic for failed webhook deliveries (exponential backoff)
• Sign EVERY webhook — never send unsigned events
• Use timing-safe comparison when verifying signatures on the receiving end
• Store webhook delivery status for debugging

Fetch the orders RFC and webhook examples from the GitHub repo for exact event shapes, signature format, and field definitions before implementing.