ACP Delegate Authentication (3DS)

Before writing code

Fetch live spec — this API arrived in the 2026-04-17 release:

1. Fetch https://github.com/agentic-commerce-protocol/agentic-commerce-protocol/releases for the current spec version.
2. Fetch spec/<version>/openapi/openapi.delegate_authentication.yaml — authoritative for paths, request fields, statuses, and headers.
3. Fetch spec/<version>/json-schema/schema.delegate_authentication.json for the schemas.
4. Read acp-delegated-payment alongside this — authentication and payment delegation are separate but adjacent flows.

This API handles card data and authentication outcomes. Implement it from the live spec, never from memory or an example found elsewhere.

Conceptual Architecture

What it delegates

Consumer authentication — specifically 3D Secure 2 browser-based flows — to a merchant-specified authentication provider. The agent does not perform 3DS itself; it drives a provider that does, and carries the result back into checkout.