Gateways

Create a purchase transaction

Charges the payment method immediately (authorize and capture in a single step) for amount_cents on the gateway. Creates a purchase transaction and returns it with 201. A 201 means the request was processed, not that funds moved — read the outcome from data.status (success, declined, or error). Pass an Idempotency-Key header to make retries safe — a replay returns the original result with X-Idempotent-Replayed: true. Returns 404 when the gateway is not found, or a referenced payment_method_id is unknown or owned by a different merchant, 409 when a request with the same key is still in flight, and 422 when the request fails validation. On success, API-key-authenticated requests emit a payment.completed webhook (declines emit payment.declined, processing failures payment.error).

POST

api

payment

v2026-04

gateways

{id}

purchase

curl --request POST \
  --url https://api.fluid.app/api/payment/v2026-04/gateways/{id}/purchase \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "transaction": {
    "amount_cents": 4999,
    "currency_code": "USD",
    "payment_method_id": "pm_9f8e7d6c"
  }
}
'

{
  "data": {
    "id": "fpi_01hxyzabc123",
    "gateway_id": "stripe-usd",
    "payment_method_id": "018f2c1a-9c4b-7e6d-9f10-3b4c5d6e7f80",
    "card_network": "visa",
    "parent_transaction_id": null,
    "action": "purchase",
    "status": "success",
    "amount_cents": 4999,
    "currency_code": "USD",
    "payment_source": "CreditCard",
    "gateway_transaction_id": "ch_3PQr7s2eZvKYlo2C",
    "reference_token": "order_12345",
    "description": null,
    "processing_fee_cents": 175,
    "platform_fee_cents": 130,
    "credited_amount_cents": 0,
    "retain_on_success": false,
    "metadata": {},
    "created_at": "2026-04-01T12:00:00Z",
    "updated_at": "2026-04-01T12:00:00Z"
  },
  "meta": {
    "request_id": "018f2c1a-8b3a-7e6d-9f10-2a3b4c5d6e7f",
    "timestamp": "2026-04-01T12:00:00Z"
  }
}

Authorizations

Authorization

string

header

required

Merchant API key (fp_live_* for live, fp_test_* for sandbox) or an admin-tier JWT (company admin or root admin). Non-admin JWTs are rejected with 403; live API keys additionally require the merchant's API access to be enabled.

Headers

Idempotency-Key

string

Optional client-generated key (UUID recommended) used to deduplicate retries. The first request with a given key executes normally; a retry with the same key replays that first response with X-Idempotent-Replayed: true for up to 24 hours. A concurrent retry while the first request is still in flight returns 409.

The response cache is keyed on the authenticated merchant and this key ONLY — not on the operation, path, or request body. Use a fresh, unique key per logical request: reusing one key across different operations (for example a purchase and then a capture) replays the first operation's cached status and body instead of performing the second.

Idempotency applies to API-key-authenticated requests only. On JWT-authenticated requests the header is accepted but ignored — no deduplication, no 409, no replay. The cache stores whatever the first execution returned, including error responses such as 404 or 422. Keys longer than 255 characters are rejected with an unhandled 500.

Maximum string length: 255

Path Parameters

string

required

Gateway slug

Body

application/json

transaction

object

required

Show child attributes

Response

Purchase created

data

object

required

Show child attributes

meta

object

required

Show child attributes

curl --request POST \
  --url https://api.fluid.app/api/payment/v2026-04/gateways/{id}/purchase \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "transaction": {
    "amount_cents": 4999,
    "currency_code": "USD",
    "payment_method_id": "pm_9f8e7d6c"
  }
}
'

{
  "data": {
    "id": "fpi_01hxyzabc123",
    "gateway_id": "stripe-usd",
    "payment_method_id": "018f2c1a-9c4b-7e6d-9f10-3b4c5d6e7f80",
    "card_network": "visa",
    "parent_transaction_id": null,
    "action": "purchase",
    "status": "success",
    "amount_cents": 4999,
    "currency_code": "USD",
    "payment_source": "CreditCard",
    "gateway_transaction_id": "ch_3PQr7s2eZvKYlo2C",
    "reference_token": "order_12345",
    "description": null,
    "processing_fee_cents": 175,
    "platform_fee_cents": 130,
    "credited_amount_cents": 0,
    "retain_on_success": false,
    "metadata": {},
    "created_at": "2026-04-01T12:00:00Z",
    "updated_at": "2026-04-01T12:00:00Z"
  },
  "meta": {
    "request_id": "018f2c1a-8b3a-7e6d-9f10-2a3b4c5d6e7f",
    "timestamp": "2026-04-01T12:00:00Z"
  }
}

Overview

Task guides

Portal & Widgets

Endpoints

Auth endpoints

Checkout endpoints

Public SDK endpoints

Member endpoints

Payment gateway endpoints

Cart payment endpoints

Commerce endpoints

Webhooks endpoints

Company admin endpoints (v0)

Analytics

Create a purchase transaction

Authorizations

Headers

Path Parameters

Body

Response