auto-paying SaaS invoices with an AI agent under policy constraints

the wish: let an AI agent pay recurring SaaS invoices without manual approval for every $20 charge, but don't let it drain your account if something goes wrong.

the missing piece is a governance layer that enforces spending policies before the agent calls the payment API.

here's how mnemopay handles it:

1. per-vendor spending caps — set a monthly limit for each SaaS vendor (e.g. $500 for Stripe, $100 for Vercel)
2. approval thresholds — auto-approve charges under $50, require human sign-off above that
3. counterparty whitelist — the agent can only pay vendors you've pre-approved
4. auto-reconciliation — every payment gets logged with invoice metadata and matched against your accounting system
5. merkle audit trail — tamper-evident log of every proposed and executed transaction

the agent proposes a payment, the policy engine validates it against your rules, then the transaction commits or aborts. if the agent tries to pay an unknown vendor or exceed a cap, the attempt gets blocked and logged.

this isn't just convenience — it's a compliance requirement under EU AI Act Article 12 for high-risk systems. the audit bundle has to be a first-class output.

i shipped v0.5.0 of the mnemopay SDK with two-phase commit and policy enforcement built in. wraps Coinbase x402 and other payment rails with the governance layer as middleware.

if you're building agent tooling that touches money, treat policy enforcement as infrastructure, not a feature.