AFFIXIO
SPT gates
Shared Payment Token verification layer
Shared Payment Token models let agents initiate spend without merchants handling raw card numbers. Tokens still need a permission layer that proves the agent was authorised under policy before the token is presented. AffixIO verifies that boundary with signed allow or deny, spent-proof anti-replay, and Merkle audit references.
Definition
Shared Payment Token verification confirms, via signed allow or deny, that an agent may present a payment token under stated policy before authorisation proceeds.
Field note. Tokens issued without a verify layer at redemption invite double-spend when agents retry failed checkouts.
Permission before token presentation
Issue an AffixIO permission proof when the user grants agent spend authority. Before the agent presents the Shared Payment Token, verify and gate. Deny blocks presentation. Allow proceeds with Merkle metadata stored alongside the capture record.
Card and account data remain in the payment stack. AffixIO never replaces token vaults. It adds a verifier-checkable decision at the agent boundary.
Spent-proof for agent sessions
Agent sessions that initiate multiple purchases need clear replay rules. Spent-proof marks a permission as consumed when used. Nonce binding offers alternatives where partial reuse is valid within a session window.
Combine with short TTLs on permission proofs so revoked agent authority stops new authorisations quickly without waiting for token rotation.
Operational detail for Shared Payment Token gates
For Shared Payment Token gates, provision sandbox circuits that mirror production predicates before you expose live agent traffic. Capture sample allow and deny payloads for regression tests.
Keep identity and rich attributes with the issuer. Verifiers receive outcomes and Merkle metadata only. Sync audit refs to your SIEM or order store after the gate returns.
Recovery blind spot
Tokens move money. They do not prove agent permission.
A valid token can be presented by any caller that holds it. Agentic commerce needs evidence that policy permitted this presentation at this time.
Token possession equals authorisation
Holding a Shared Payment Token is treated as permission without an independent verify step.
Double presentation
Without spent-proof, the same permission can authorise multiple captures.
Weak agent binding
Tokens are not naturally bound to the agent identity that requested spend.
Audit gaps
Token logs show usage, not the signed policy decision that allowed usage.
Tool-call gate
Shared Payment Token gates before token redemption
Shared Payment Token flows need verify at redemption, not just at issuance. Wire spent-proof on first presentation so tokens cannot pay twice across agent sessions.
Define token presentation edges
List where agents attach Shared Payment Tokens to checkout or capture calls.
Issue agent-bound permissions
Mint proofs tied to agent identity, amount policy, and expiry.
Verify before presentation
Gate on allow or deny immediately before token use.
Enable spent-proof
Block replay where a single permission must not fund two captures.
Policy review
Readiness checks for Shared Payment Token gates
- Map SPT paths in your agentic commerce stack.
- Bind permissions to agent identity, not only user session.
- Configure spent-proof for one-shot checkout permissions.
- Store Merkle refs with capture records.
- Test deny when consent is revoked mid-session.
Straight answers
Questions on Shared Payment Token gates
Does AffixIO store payment tokens?
No. AffixIO verifies permission outcomes. Tokens stay in your payment infrastructure.
What is spent-proof?
A pattern that marks a credential as consumed at verify so it cannot authorise twice.
Works with AP2 and UCP?
Yes. The verify endpoint sits beside whichever orchestration presents the token.
Sandbox available?
Use the live sandbox to exercise payment-policy circuits before production.
Compare paths
Pages that support Shared Payment Token gates
Agentic payments
More agentic payments briefs
Build Shared Payment Token gates
Issue and verify tokens in sandbox, then wire redemption verify to your agent payment boundary.