Guardrails
Guardrails are rule-based controls enforced at multiple levels to ensure AI agents cannot exceed their authorized scope. They operate across three enforcement layers:1. Mandate-Level Constraints
Every payment intent creates a mandate at the card network level. The mandate itself is a guardrail — it specifies:| Constraint | What it controls |
|---|---|
| Merchant | The merchant the mandate is scoped to |
| Amount threshold | Maximum amount for the transaction |
| Frequency | Currently one_time (recurring frequencies are planned) |
| Effective duration | When the mandate expires (expiresAt) |
| Product scope | The products in the purchase (via mandate line items) |
2. Session-Level Controls
Each session is scoped to:- A specific merchant and order
- A configured set of allowed domains (origin validation)
- A time limit — sessions expire and cannot be reused
- Idempotency — duplicate transactions within a session are detected and rejected
3. Authentication Controls
- Passkey (WebAuthn) — required for every intent mutation (register, update, delete). Prevents unauthorized agents from creating mandates.
- Device binding — passkeys are registered per browser, so a passkey on one device cannot be used on another.
- WebAuthn required — if the user’s device does not support WebAuthn (passkeys), transactions cannot be performed. There is no fallback mechanism — this ensures the highest level of authentication security.