StellarNotherc DocsProtocol
MPP Architecture
How StellarNotherc implements the Machine Payment Protocol with dual payment intents for agent commerce.
Machine Payment Protocol
The Machine Payment Protocol (MPP) is Stellar's standard for agent-to-service payments. StellarNotherc uses MPP with two complementary intents: charge for per-request micropayments and channel (sessions) for high-frequency agent workflows.
Sessions allow an agent to authorize a spending limit upfront, then stream micropayments against that session without a separate on-chain transaction for each call. The mppx SDK powers the portfolio-worker middleware, while the web app implements MPP natively for full control over challenge HMAC binding and hash memo verification.
Charge vs. Channel
| Feature | Charge Intent | Channel Intent (Sessions) |
|---|---|---|
| Settlement | Per-request, on-chain on Stellar | Session-based, single funding tx + refund |
| Throughput | 1 tx per tool call | Thousands of calls per session |
| Best for | One-off queries, external callers | Agent chat workflows, batch analytics |
| Auth header | Authorization: Payment <credential> | x-mpp-session: <session-id> |
| Proof | SP1 purchase receipt per call | SP1 purchase receipt per debited marketplace execution |
Existing Architecture Alignment
StellarNotherc's session lifecycle implements the core primitives that MPP channel intent requires:
| MPP Concept | Implementation |
|---|---|
| Session with spending limit | mpp-session.ts — budget allocation, funding verification, 24h TTL |
| Per-call charges | chargeMppSession() — atomic charge with rollback on failure |
| Refunds | refundMppSessionCharge() — automatic refund on tool failure |
| Charge intent | mpp-charge.ts — WWW-Authenticate challenge + Authorization credential verification |
| Proof of payment | SP1 purchase receipt proofs reconciled against durable marketplace executions |
Wire Format
Challenge: WWW-Authenticate: Payment id="...", realm="...", method="stellar", intent="charge", request="<base64url>"
Credential: Authorization: Payment <base64url({"challenge":{...}, "payload":{"transactionHash":"..."}})>
Hash Memo: Stellar tx memo = SHA-256(challenge.id), binding payment to specific challenge