@pot-sdk2/x402

Decision verification hook for x402 payments — verifies whether an agent's payment decision is well-justified before settlement executes.

The Problem

x402 enables AI agents to pay for services autonomously. The facilitator verifies that the payment is valid (correct signature, sufficient balance, right network).

But nobody verifies whether the decision to pay was well-justified.

An agent can authorize a perfectly valid payment for a service it doesn't need, at a price it shouldn't accept, based on reasoning that wouldn't survive scrutiny.

The Solution

@pot-sdk2/x402 adds a beforeSettle hook to the x402 facilitator that runs ThoughtProof decision verification before settlement executes.

• Payment valid + decision strong → settle
• Payment valid + decision weak → hold

Install

npm install @pot-sdk2/x402 pot-sdk @x402/core

Quick Start

import { createThoughtProofHook } from '@pot-sdk2/x402';
import { x402Facilitator } from '@x402/core/facilitator';
import { registerExactEvmScheme } from '@x402/evm/exact/facilitator';

const facilitator = new x402Facilitator();

// Register your payment scheme
registerExactEvmScheme(facilitator, {
  signer: evmSigner,
  networks: 'eip155:8453', // Base
});

// Add ThoughtProof decision verification before settlement
facilitator.onBeforeSettle(createThoughtProofHook({
  providers: [
    { name: 'anthropic', model: 'claude-sonnet-4-20250514', apiKey: process.env.ANTHROPIC_API_KEY! },
    { name: 'deepseek', model: 'deepseek-chat', apiKey: process.env.DEEPSEEK_API_KEY! },
  ],
  stakeLevel: 'medium',      // micro | low | medium | high | critical
  classifyMateriality: true,  // only block on material defects
  debug: true,
}));

// Now settlement includes decision verification
const verifyResult = await facilitator.verify(paymentPayload, requirements);
if (verifyResult.isValid) {
  // This will run ThoughtProof verification before settling
  const settleResult = await facilitator.settle(paymentPayload, requirements);
}

Auto-Stake Detection

Don't want to set stake levels manually? Use createAutoStakeHook — it detects the payment amount and adjusts skepticism automatically:

import { createAutoStakeHook } from '@pot-sdk2/x402';

facilitator.onBeforeSettle(createAutoStakeHook({
  providers: [...],
  classifyMateriality: true,
}));

// $2.50 → micro (threshold 0.40, only material defects block)
// $149  → medium (threshold 0.60, proportional review)
// $5000 → critical (threshold 0.85, full adversarial)

Stake Levels

| Level | Threshold | Critic Mode | Example | |-------|-----------|-------------|---------| | micro | 0.40 | Proportional — material defects only | $2.50 API batch | | low | 0.50 | Proportional — material defects + basic logic | $50 data purchase | | medium | 0.60 | Proportional — reasoning quality + evidence | $500 vendor selection | | high | 0.75 | Adversarial — full skepticism | $5K settlement | | critical | 0.85 | Adversarial — maximum scrutiny | $50K+ / regulated |

How It Works

Agent decides to pay
        ↓
x402 facilitator.verify() — payment valid?
        ↓
x402 facilitator.settle() — execute payment
        ↓
    [beforeSettle hook]
        ↓
ThoughtProof runs multi-model adversarial verification:
  - Is the payment amount proportional to the service?
  - Is there a material defect in the decision reasoning?
  - Would a competent reviewer change this decision?
        ↓
  confidence >= threshold → SETTLE (payment executes)
  confidence < threshold  → HOLD (payment blocked with reason)

Monitoring

facilitator.onBeforeSettle(createThoughtProofHook({
  providers: [...],
  onVerification: (result) => {
    console.log(`Decision: ${result.allowed ? 'ALLOW' : 'HOLD'}`);
    console.log(`Confidence: ${result.confidence}`);
    console.log(`Duration: ${result.durationMs}ms`);
    if (result.materiality) {
      console.log(`Material defects: ${result.materiality.materialCount}`);
    }
    // Send to your monitoring / analytics
  },
}));

The Payment Trust Stack

Identity      → Visa TAP / ERC-8004
Authorization → Mastercard Verifiable Intent
Risk          → t54 / fraud scoring
Decision      → ThoughtProof (@pot-sdk2/x402)  ← you are here
Execution     → x402 facilitator / settlement

Requirements

• @x402/core >= 2.0.0
• pot-sdk >= 1.1.0
• At least 2 LLM provider API keys (for multi-model verification)

License

MIT — ThoughtProof Protocol