Facilitators

Settlement services that verify and submit x402 agent payments on Stable so you do not run your own infrastructure.

A facilitator verifies a signed x402 payment and submits the on-chain call that settles it in USDT0 on Stable. Using a hosted facilitator means you do not run settlement infrastructure or manage gas tokens. For the rail-level context, see Agent settlement.

Overview table

Provider	Category	Docs / Get Started	Notes
Semantic Pay	x402 facilitator	https://docs.semanticpay.io/supported-chains#stable	Public x402 facilitator for Stable; verifies and settles USDT0 payments via ERC-3009
Heurist	x402 facilitator	https://docs.heurist.ai/x402-products/facilitator#supported-networks	Multi-chain x402 facilitator supporting Stable; high-throughput verification and settlement with OFAC screening

Semantic Pay

Payment infrastructure for AI agents: trustless, P2P, and permissionless. Semantic Pay operates as an x402-compatible payment facilitator on Stable, settling USDT0 payments via ERC-3009 (transferWithAuthorization). Agents do not need a separate gas token in their wallets.

Developers integrating x402 on Stable point their middleware to https://x402.semanticpay.io. No custom settlement infrastructure is required.

Capabilities

• Payment payload verification (/verify) and on-chain settlement (/settle) via USDT0
• Gasless transfers using ERC-3009 transferWithAuthorization
• Spend limits, approval flows, and kill switches for agent oversight
• End-to-end traceability with full audit logging from intent through settlement
• Event callbacks for real-time payment lifecycle updates

Facilitator endpoint: https://x402.semanticpay.io

Docs: https://docs.semanticpay.io/supported-chains#stable

Heurist

Heurist operates a multi-chain x402 facilitator that supports Stable alongside Base, Base Sepolia, and X Layer. It targets high-frequency agent workloads with throughput tuned for thousands of payment verifications and settlements per second.

Point your middleware at https://facilitator.heurist.xyz. No API key is required to get started.

Capabilities

• Payment verification and on-chain settlement across multiple networks from one endpoint
• Throughput sized for high-frequency agent traffic
• Automatic OFAC screening of sender addresses
• Real-time observability over verification and settlement activity

Facilitator endpoint: https://facilitator.heurist.xyz

Docs: https://docs.heurist.ai/x402-products/facilitator#supported-networks

How to choose

• Use a hosted facilitator (Semantic Pay or Heurist) to start fast. No infrastructure to run, no gas tokens to manage.
• Pick by what matters most for your workload: Semantic Pay if you want Stable-native tooling with lifecycle callbacks and agent oversight controls; Heurist if you need a single endpoint that spans Stable plus other EVM networks, or if OFAC screening is a hard requirement.
• Self-host if you need full control over settlement policy, want to keep payment data in your own environment, or expect volume that justifies the operational overhead.
• Both facilitators settle x402 on Stable today. The same /settle endpoint can also serve as the on-chain submission target for an MPP server, since MPP’s wire format only differs from x402 on the client ↔ resource-server hop. See Build an MPP endpoint on Stable.

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Have an agentic payments integration with Stable? Reach out at [e-mail].