Looking for Shop Pay delegated payment client_id for UCP

Agentic Commerce
1

We’re working on a buyer-present UCP commerce flow through our customer-service platform. A customer would build a cart, then use Shop Pay to review and authorize payment. The Shopify merchant remains the merchant of record, and we don’t handle raw card
data.

We already have Shopify Global API credentials, Token tier authentication working, a hosted UCP agent profile, and a submitted Universal Cart access request.

The Shop Pay documentation says Path A requires a separate platform client_id for the one-time Payment Request flow. Shopify Support confirmed that self service registration isn’t open yet and told me to post our use case here.

What do we need to do next to obtain the Shop Pay platform client_id? Is there a sandbox for testing, and does the client_id work across participating Shopify merchants?

I’m happy to share our company, Partner ID, Global API client ID, agent profile, and test store details privately with the appropriate Shopify team.

Thanks!

2

Not directly answering your Shop Pay client_id question (following that with interest, since it’ll be relevant to us eventually too) — but wanted to ask about something you mentioned in passing: you said you already have “Token tier authentication working” and “a hosted UCP agent profile.”

We’re building a multi-brand marketplace checkout on Shopify (posted about the multi-merchant cart side of it separately here: Multi-merchant cart/checkout in UCP) and got stuck exactly at that step. Our agent profile was never hosted at a public URL — ucp doctor flagged this early on (“profile has no profile_url, managed upload may not be configured yet”), and we didn’t think much of it until we hit a hard wall trying to call complete_checkout:

403 AuthenticationRequired: A valid JWT is required to call complete_checkout.

Since you’ve clearly gotten past this part:

  1. How did you actually host the agent profile — self-hosted at your own URL, or is there a managed/Shopify-provided hosting path we missed?
  2. What does “token tier” mean in practice here — is this the same trust-tier system mentioned in Shopify’s docs (where higher tiers unlock direct checkout completion), or a separate mechanism specific to authentication?
  3. Once the profile was hosted, did checkout completion start working without the JWT error, or was there a separate approval/registration step beyond just hosting the profile?

Any detail you can share on this specific piece would save us a lot of trial and error — happy to compare notes on the broader UCP integration too, since it sounds like we’re both fairly early and hitting similar walls.