Create Payment Session

Create a new Payment Session based on a Payment Link. This step instantiates the link into a specific transaction bound to a user, a chain, and a token.

POST /payment/session/create

EIP-712 Authorization

This endpoint requires an EIP-712 signature with the purpose create_payment_session. The user must sign the specific payment parameters (Amount, Token, Chain) to authorize the session creation.

• Domain Name: aipay.gstable.io
• Version: 1
• Chain ID: The chain ID selected for payment.

Request Parameters

Field	Type	Required	Description
message	Object	✅	The EIP-712 message object signed by the user.
message.purpose	String	✅	Must be create_payment_session.
message.linkId	String	✅	The ID of the Payment Link.
message.linkVersion	String	✅	The version of the Payment Link.
message.merchantId	String	✅	The Merchant ID.
message.payer	Address	✅	The wallet address of the payer.
message.paymentChainId	String	✅	The chain ID where payment will occur.
message.paymentToken	Address	✅	The token address for payment.
message.amount	String	✅	The payment amount in the smallest token unit.
message.authorizationNonce	Bytes32	✅	A random 32-byte hex string to prevent replay attacks.
message.authorizationExpiresAt	Timestamp	✅	Expiration time for this signature (seconds).
signature	Bytes	✅	The resulting EIP-712 signature string (0x...).

Request Example

{
  "message": {
    "purpose": "create_payment_session",
    "linkId": "lnk_example_premium_plan_01",
    "linkVersion": "ver_example_03",
    "merchantId": "f7d65b193454db46fb2d6277e2f5e593bffcf6adde5064a2bb5dee6fd9b0fb7a",
    "payer": "0x1234567890123456789012345678901234567890",
    "paymentChainId": "137",
    "paymentToken": "0x3c499c542cef5e3811e1192ce70d8cc03d5c3359",
    "amount": "3009000",
    "authorizationNonce": "0xc6086627cff7f653c382d6e75b7f5afa239125f69887ac63516afce9fd0f8345",
    "authorizationExpiresAt": "1769486386"
  },
  "signature": "0xa6be9f1cdfcbb534d61ad327dadf3aefa3e6ca52889890dbb2318f949061c7f42e2dce8c7a7e6b5007ccdf8e484ef2b6c282eaa16889978b2278c53fa37b07ab1c"
}

Response Structure

Returns the created sessionId and the next stage of the AI View.

Response Example

{
  "code": 0,
  "message": "success",
  "data": {
    "sessionId": "sess_example_payment_04",
    "sessionType": "ai_checkout",
    "sessionExpiresAt": 1769484586,
    "aiView": {
      "pricingModel": { "type": "fixed" },
      "workflow": {
        "stage": "session_ready",
        "nextAction": {
          "action": "prepare_payment",
          "authorizationRequired": true
        }
      },
      "preparePaymentRequirement": {
        "authorizationRequired": true,
        "authorizationSpec": {
          "type": "eip712",
          "purpose": "prepare_payment",
          // ... EIP-712 types for prepare_payment ...
        }
      }
    }
  }
}

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Error Handling

This endpoint follows the Unified Error Handling standard. Business errors return HTTP 200 with a non-zero code.