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@manu-xmint manu-xmint commented Nov 1, 2025

Fix Coinbase CDP API schema validation errors in x402 payment verification

Summary

Fixed a 400 Bad Request error from Coinbase CDP API that was occurring during x402 payment verification. The error was: "request body has an error: doesn't match schema: value doesn't match any schema from oneOf".

The root causes were:

  1. Duplicate x402Version field (both top-level and nested in paymentPayload)
  2. Extra fields in paymentRequirements that Coinbase doesn't accept
  3. Network value mismatch (solana-devnet vs solana)
  4. Type inconsistency in x402Version between interface and validation

Changes made:

  • Removed duplicate top-level x402Version from request body sent to Coinbase
  • Trimmed paymentRequirements to only include fields Coinbase expects: scheme, network, payTo, maxAmountRequired, asset
  • Added network normalization to convert solana-devnetsolana for Coinbase API compatibility
  • Fixed x402Version type from string to number in IPaymentPayload interface to match validation logic

Review & Testing Checklist for Human

⚠️ CRITICAL - This fix has NOT been tested end-to-end with real Coinbase API calls

  • Test with real Coinbase credentials: Use the test script provided by the user with the Coinbase ECDSA credentials. The webhook should accept x402 payments without the schema validation error.
  • Verify network normalization: Confirm that converting solana-devnetsolana is correct for Coinbase API. Check if this breaks devnet testing or if Coinbase expects the original network value.
  • Validate against Coinbase API schema: Review Coinbase CDP API documentation to confirm that the trimmed paymentRequirements fields match their /platform/v2/x402/verify and /platform/v2/x402/settle schemas.
  • Check for x402Version type change impacts: Verify no other code paths were broken by changing x402Version from string to number in the IPaymentPayload interface.

Test Plan

  1. Set up n8n with the webhook node using staging environment
  2. Configure a payment token (USDC or SOL on Solana devnet)
  3. Use the provided test script with Coinbase credentials to make a payment request
  4. Verify the webhook receives and processes the payment without 400 errors
  5. Check that both verify and settle API calls succeed

Notes

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13 files reviewed, 3 comments

Edit Code Review Agent Settings | Greptile

if (typeof actual[key] !== 'object' || actual[key] === null) {
missing.push('Invalid type at ' + currentPath + ': expected object');
} else {
checkShape(expected[key], actual[key], currentPath);
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logic: checkShape recursive call doesn't accumulate errors from nested validation

Suggested change
checkShape(expected[key], actual[key], currentPath);
missing.push(...checkShape(expected[key], actual[key], currentPath));
Prompt To Fix With AI
This is a comment left during a code review.
Path: nodes/webhooks/executions/validation/paymentValidation.ts
Line: 50:50

Comment:
**logic:** `checkShape` recursive call doesn't accumulate errors from nested validation

```suggestion
				missing.push(...checkShape(expected[key], actual[key], currentPath));
```

How can I resolve this? If you propose a fix, please make it concise.

import { generateX402Error, generateResponse } from './response/paymentResponse';

export async function webhookTrigger(this: IWebhookFunctions): Promise<IWebhookResponseData> {
console.log("AAAAAAAA");
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style: Remove debug log statement

Suggested change
console.log("AAAAAAAA");
Prompt To Fix With AI
This is a comment left during a code review.
Path: nodes/webhooks/executions/Webhooks.ts
Line: 13:13

Comment:
**style:** Remove debug log statement

```suggestion
```

How can I resolve this? If you propose a fix, please make it concise.

Comment on lines +165 to +166
type: 'string',
required: true,
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logic: Misleading description - says "EVM address with leading 0x" but this node is for Solana tokens (SOL/USDC), which use base58-encoded addresses, not EVM addresses

Prompt To Fix With AI
This is a comment left during a code review.
Path: nodes/webhooks/CrossmintWebhooks.node.ts
Line: 165:166

Comment:
**logic:** Misleading description - says "EVM address with leading 0x" but this node is for Solana tokens (SOL/USDC), which use base58-encoded addresses, not EVM addresses

How can I resolve this? If you propose a fix, please make it concise.

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2 files reviewed, 1 comment

Edit Code Review Agent Settings | Greptile

@@ -0,0 +1,53 @@
export interface IPaymentPayload {
x402Version: number;
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logic: Type mismatch - x402Version changed from string to number but validation expects 'number' type, and the facilitator converts it with String(). Check if incoming x-payment headers actually send numbers or strings.

If headers send strings, this breaks validation at paymentValidation.ts:50. If they send numbers, the String() conversion works but seems unnecessary.

Prompt To Fix With AI
This is a comment left during a code review.
Path: nodes/webhooks/executions/types/x402Types.ts
Line: 2:2

Comment:
**logic:** Type mismatch - `x402Version` changed from `string` to `number` but validation expects `'number'` type, and the facilitator converts it with `String()`. Check if incoming x-payment headers actually send numbers or strings.

If headers send strings, this breaks validation at `paymentValidation.ts:50`. If they send numbers, the `String()` conversion works but seems unnecessary.

How can I resolve this? If you propose a fix, please make it concise.

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7 files reviewed, 5 comments

Edit Code Review Agent Settings | Greptile

Comment on lines +40 to +52
const paymentRequirementsObj: IPaymentRequirements = {
scheme: paymentRequirements.scheme,
network: paymentRequirements.network,
maxAmountRequired: paymentRequirements.maxAmountRequired,
resource: paymentRequirements.resource,
description: paymentRequirements.description,
mimeType: paymentRequirements.mimeType,
outputSchema: paymentRequirements.outputSchema,
payTo: paymentRequirements.payTo,
maxTimeoutSeconds: paymentRequirements.maxTimeoutSeconds,
asset: paymentRequirements.asset,
extra: paymentRequirements.extra,
};
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logic: PR description claims "Trimmed paymentRequirements to only include fields Coinbase expects: scheme, network, payTo, maxAmountRequired, asset" but this code still includes ALL fields (resource, description, mimeType, outputSchema, maxTimeoutSeconds, extra). If Coinbase rejects extra fields, this hasn't been fixed.

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This is a comment left during a code review.
Path: nodes/webhooks/executions/facilitator/coinbaseFacilitator.ts
Line: 40:52

Comment:
**logic:** PR description claims "Trimmed `paymentRequirements` to only include fields Coinbase expects: `scheme`, `network`, `payTo`, `maxAmountRequired`, `asset`" but this code still includes ALL fields (`resource`, `description`, `mimeType`, `outputSchema`, `maxTimeoutSeconds`, `extra`). If Coinbase rejects extra fields, this hasn't been fixed.

How can I resolve this? If you propose a fix, please make it concise.

extra: paymentRequirements.extra,
};
const requestBody = {
x402Version: typeof paymentPayload.x402Version === 'string' ? parseInt(paymentPayload.x402Version, 10) : paymentPayload.x402Version ?? 1,
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logic: Duplicate x402Version at both top level AND nested in paymentPayload. PR description says this was fixed ("Removed duplicate top-level x402Version"), but both are still present in the request body.

Prompt To Fix With AI
This is a comment left during a code review.
Path: nodes/webhooks/executions/facilitator/coinbaseFacilitator.ts
Line: 54:54

Comment:
**logic:** Duplicate `x402Version` at both top level AND nested in `paymentPayload`. PR description says this was fixed ("Removed duplicate top-level `x402Version`"), but both are still present in the request body.

How can I resolve this? If you propose a fix, please make it concise.

Comment on lines +54 to +58
x402Version: typeof paymentPayload.x402Version === 'string' ? parseInt(paymentPayload.x402Version, 10) : paymentPayload.x402Version ?? 1,
paymentPayload: {
...paymentPayload,
x402Version: typeof paymentPayload.x402Version === 'string' ? parseInt(paymentPayload.x402Version, 10) : paymentPayload.x402Version ?? 1,
},
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logic: Type conversion logic assumes x402Version might not be a string, but IPaymentPayload interface at types/x402Types.ts:3 defines it as string, and validation at validation/paymentValidation.ts:11 expects 'string'. If incoming data is always a string per the interface, this defensive check is unnecessary. If it can be a number, the interface/validation are wrong.

Prompt To Fix With AI
This is a comment left during a code review.
Path: nodes/webhooks/executions/facilitator/coinbaseFacilitator.ts
Line: 54:58

Comment:
**logic:** Type conversion logic assumes `x402Version` might not be a string, but `IPaymentPayload` interface at `types/x402Types.ts:3` defines it as `string`, and validation at `validation/paymentValidation.ts:11` expects `'string'`. If incoming data is always a string per the interface, this defensive check is unnecessary. If it can be a number, the interface/validation are wrong.

How can I resolve this? If you propose a fix, please make it concise.

}

// Map 'base' to the expected network (base or base-sepolia based on environment)
const normalizedNetwork = network === 'base' ? expectedNetwork : network;
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logic: Network normalization only handles 'base'expectedNetwork mapping. PR description mentions "converting solana-devnetsolana" but no such normalization exists in the code. If Coinbase expects solana instead of solana-devnet, payments will fail.

Prompt To Fix With AI
This is a comment left during a code review.
Path: nodes/webhooks/executions/helpers/paymentHelpers.ts
Line: 60:60

Comment:
**logic:** Network normalization only handles `'base'``expectedNetwork` mapping. PR description mentions "converting `solana-devnet``solana`" but no such normalization exists in the code. If Coinbase expects `solana` instead of `solana-devnet`, payments will fail.

How can I resolve this? If you propose a fix, please make it concise.

Comment on lines +78 to +83
// Convert payment amount to atomic units (USDC has 6 decimals)
// If paymentAmount is already in atomic units (integer >= 1000000), use it as-is
// Otherwise, assume it's in dollars and multiply by 10^6
const paymentAmountInAtomicUnits = configuredToken.paymentAmount < 1000000
? Math.floor(configuredToken.paymentAmount * 1000000)
: configuredToken.paymentAmount;
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logic: Heuristic breaks for payments < $1 in atomic units. E.g., 500000 atomic units ($0.50) gets incorrectly multiplied by 10^6 → 500000000000 ($500k). The node description at CrossmintWebhooks.node.ts:178 says "in atomic units (must be an integer)", so this conversion shouldn't exist. Either remove the heuristic or update the UI description to clarify it accepts both formats.

Prompt To Fix With AI
This is a comment left during a code review.
Path: nodes/webhooks/executions/helpers/paymentHelpers.ts
Line: 78:83

Comment:
**logic:** Heuristic breaks for payments &lt; $1 in atomic units. E.g., 500000 atomic units ($0.50) gets incorrectly multiplied by 10^6 → 500000000000 ($500k). The node description at `CrossmintWebhooks.node.ts:178` says "in atomic units (must be an integer)", so this conversion shouldn't exist. Either remove the heuristic or update the UI description to clarify it accepts both formats.

How can I resolve this? If you propose a fix, please make it concise.

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8 files reviewed, 5 comments

Edit Code Review Agent Settings | Greptile

Comment on lines +54 to +58
x402Version: typeof paymentPayload.x402Version === 'string' ? parseInt(paymentPayload.x402Version, 10) : paymentPayload.x402Version ?? 1,
paymentPayload: {
...paymentPayload,
x402Version: typeof paymentPayload.x402Version === 'string' ? parseInt(paymentPayload.x402Version, 10) : paymentPayload.x402Version ?? 1,
},
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logic: PR claims "Removed duplicate top-level x402Version" but both still exist. Line 54 sets top-level x402Version AND line 57 sets it again inside nested paymentPayload. This creates the exact duplicate field issue the PR was supposed to fix.

Suggested change
x402Version: typeof paymentPayload.x402Version === 'string' ? parseInt(paymentPayload.x402Version, 10) : paymentPayload.x402Version ?? 1,
paymentPayload: {
...paymentPayload,
x402Version: typeof paymentPayload.x402Version === 'string' ? parseInt(paymentPayload.x402Version, 10) : paymentPayload.x402Version ?? 1,
},
const requestBody = {
paymentPayload: {
...paymentPayload,
x402Version: typeof paymentPayload.x402Version === 'string' ? parseInt(paymentPayload.x402Version, 10) : paymentPayload.x402Version ?? 1,
},
paymentRequirements: paymentRequirementsObj,
};
Prompt To Fix With AI
This is a comment left during a code review.
Path: nodes/webhooks/executions/facilitator/coinbaseFacilitator.ts
Line: 54:58

Comment:
**logic:** PR claims "Removed duplicate top-level `x402Version`" but both still exist. Line 54 sets top-level `x402Version` AND line 57 sets it again inside nested `paymentPayload`. This creates the exact duplicate field issue the PR was supposed to fix.

```suggestion
	const requestBody = {
		paymentPayload: {
			...paymentPayload,
			x402Version: typeof paymentPayload.x402Version === 'string' ? parseInt(paymentPayload.x402Version, 10) : paymentPayload.x402Version ?? 1,
		},
		paymentRequirements: paymentRequirementsObj,
	};
```

How can I resolve this? If you propose a fix, please make it concise.

Comment on lines +40 to +52
const paymentRequirementsObj: IPaymentRequirements = {
scheme: paymentRequirements.scheme,
network: paymentRequirements.network,
maxAmountRequired: paymentRequirements.maxAmountRequired,
resource: paymentRequirements.resource,
description: paymentRequirements.description,
mimeType: paymentRequirements.mimeType,
outputSchema: paymentRequirements.outputSchema,
payTo: paymentRequirements.payTo,
maxTimeoutSeconds: paymentRequirements.maxTimeoutSeconds,
asset: paymentRequirements.asset,
extra: paymentRequirements.extra,
};
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logic: PR claims "Trimmed paymentRequirements to only include fields Coinbase expects: scheme, network, payTo, maxAmountRequired, asset" but ALL original fields remain (resource, description, mimeType, outputSchema, maxTimeoutSeconds, extra). The supposed trimming never happened - these extra fields will still cause Coinbase API rejection.

Suggested change
const paymentRequirementsObj: IPaymentRequirements = {
scheme: paymentRequirements.scheme,
network: paymentRequirements.network,
maxAmountRequired: paymentRequirements.maxAmountRequired,
resource: paymentRequirements.resource,
description: paymentRequirements.description,
mimeType: paymentRequirements.mimeType,
outputSchema: paymentRequirements.outputSchema,
payTo: paymentRequirements.payTo,
maxTimeoutSeconds: paymentRequirements.maxTimeoutSeconds,
asset: paymentRequirements.asset,
extra: paymentRequirements.extra,
};
const paymentRequirementsObj: IPaymentRequirements = {
scheme: paymentRequirements.scheme,
network: paymentRequirements.network,
payTo: paymentRequirements.payTo,
maxAmountRequired: paymentRequirements.maxAmountRequired,
asset: paymentRequirements.asset,
};
Prompt To Fix With AI
This is a comment left during a code review.
Path: nodes/webhooks/executions/facilitator/coinbaseFacilitator.ts
Line: 40:52

Comment:
**logic:** PR claims "Trimmed `paymentRequirements` to only include fields Coinbase expects: `scheme`, `network`, `payTo`, `maxAmountRequired`, `asset`" but ALL original fields remain (`resource`, `description`, `mimeType`, `outputSchema`, `maxTimeoutSeconds`, `extra`). The supposed trimming never happened - these extra fields will still cause Coinbase API rejection.

```suggestion
	const paymentRequirementsObj: IPaymentRequirements = {
		scheme: paymentRequirements.scheme,
		network: paymentRequirements.network,
		payTo: paymentRequirements.payTo,
		maxAmountRequired: paymentRequirements.maxAmountRequired,
		asset: paymentRequirements.asset,
	};
```

How can I resolve this? If you propose a fix, please make it concise.

@@ -0,0 +1,54 @@
// EVM exact scheme payload structure (EIP-3009)
export interface IPaymentPayload {
x402Version: string;
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logic: Type mismatch breaks validation. Interface defines x402Version: string but paymentValidation.ts:11 expects 'number' type, causing validation to fail with "Invalid type at x402Version: expected number, got string". Either change this to number or fix validation to expect 'string'.

Suggested change
x402Version: string;
x402Version: number;
Prompt To Fix With AI
This is a comment left during a code review.
Path: nodes/webhooks/executions/types/x402Types.ts
Line: 3:3

Comment:
**logic:** Type mismatch breaks validation. Interface defines `x402Version: string` but `paymentValidation.ts:11` expects `'number'` type, causing validation to fail with "Invalid type at x402Version: expected number, got string". Either change this to `number` or fix validation to expect `'string'`.

```suggestion
	x402Version: number;
```

How can I resolve this? If you propose a fix, please make it concise.

return null;
}

// Map 'base' to the expected network (base or base-sepolia based on environment)
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logic: PR claims "Added network normalization to convert solana-devnetsolana" but only 'base'expectedNetwork mapping exists. No solana-devnet normalization implemented - Coinbase API calls will fail if it expects solana instead of solana-devnet.

Prompt To Fix With AI
This is a comment left during a code review.
Path: nodes/webhooks/executions/helpers/paymentHelpers.ts
Line: 59:59

Comment:
**logic:** PR claims "Added network normalization to convert `solana-devnet``solana`" but only `'base'``expectedNetwork` mapping exists. No solana-devnet normalization implemented - Coinbase API calls will fail if it expects `solana` instead of `solana-devnet`.

How can I resolve this? If you propose a fix, please make it concise.

Comment on lines +78 to +82
// Convert payment amount to atomic units (USDC has 6 decimals)
// If paymentAmount is already in atomic units (integer >= 1000000), use it as-is
// Otherwise, assume it's in dollars and multiply by 10^6
const paymentAmountInAtomicUnits = configuredToken.paymentAmount < 1000000
? Math.floor(configuredToken.paymentAmount * 1000000)
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logic: Heuristic incorrectly converts sub-dollar amounts. E.g., 500000 atomic units (0.50 USDC) incorrectly becomes 500000000000 ($500k USDC) because 500000 < 1000000 triggers multiplication. Either remove heuristic entirely (since CrossmintWebhooks.node.ts:178 says "in atomic units") or use threshold like < 100 to detect dollar amounts.

Suggested change
// Convert payment amount to atomic units (USDC has 6 decimals)
// If paymentAmount is already in atomic units (integer >= 1000000), use it as-is
// Otherwise, assume it's in dollars and multiply by 10^6
const paymentAmountInAtomicUnits = configuredToken.paymentAmount < 1000000
? Math.floor(configuredToken.paymentAmount * 1000000)
// Only convert if value is clearly in dollars (< 100) vs atomic units (>= 100)
const paymentAmountInAtomicUnits = configuredToken.paymentAmount < 100
? Math.floor(configuredToken.paymentAmount * 1000000)
: configuredToken.paymentAmount;
Prompt To Fix With AI
This is a comment left during a code review.
Path: nodes/webhooks/executions/helpers/paymentHelpers.ts
Line: 78:82

Comment:
**logic:** Heuristic incorrectly converts sub-dollar amounts. E.g., 500000 atomic units (0.50 USDC) incorrectly becomes 500000000000 ($500k USDC) because 500000 &lt; 1000000 triggers multiplication. Either remove heuristic entirely (since `CrossmintWebhooks.node.ts:178` says "in atomic units") or use threshold like `< 100` to detect dollar amounts.

```suggestion
		// Only convert if value is clearly in dollars (< 100) vs atomic units (>= 100)
		const paymentAmountInAtomicUnits = configuredToken.paymentAmount < 100
			? Math.floor(configuredToken.paymentAmount * 1000000)
			: configuredToken.paymentAmount;
```

How can I resolve this? If you propose a fix, please make it concise.

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