Known limitations

• Direct x402 and MPP facilitator settlement is enabled on Stacks mainnet with confirmation-gated delivery and payer-approved transactions.
• Controlled mainnet STX/x402 and USDCx/MPP settlement-and-delivery canaries completed on 2026-09-03. These team-operated payments demonstrate operation, not independent adoption or revenue.
• Transaction sponsorship is disabled.
• Earned 2% escrow fees are implemented by the active STX v6/sBTC v5 contracts. The contracts are deployed and the source defaults are promoted; controlled mainnet STX/sBTC consumer E2E and each runtime deployment still require separate receipts before external onboarding. One supervised internal fee lifecycle passed on testnet. Optional paid appeal analysis is not implemented. See fee policy.
• Partner OAuth/MCP enrollment remains invite-only.
• Production OAuth uses mainnet wallet claims with controlled enrollment verified. Partner access remains invite-only and does not confer payment-signing authority.
• The direct-payment evidence panel requires the facilitator's opt-in public feed; until enabled, it reports unavailable independently of escrow data. Its latest-payment window is not a lifetime total.
• MPP uses USDCx; the hosted x402 resource currently exercises the STX profile.
• Browser signing requires a compatible Stacks wallet such as Leather.
• Headless custody requires an application-owned secret manager, KMS, HSM or isolated signer.
• Indexer availability can delay observations even when chain state is correct.
• A transaction broadcast or pending status is not confirmed settlement.
• The API schema is a versioned snapshot and displays its last verification date; runtime challenges remain authoritative for price, recipient and payment requirements.

These limitations are deliberate rollout and security boundaries, not instructions to bypass checks. Consult deployments and payment safety before an integration moves beyond read-only evaluation.