simulateTransaction

POSThttps://triport.io/rpc/stellar

Submits a trial contract invocation transaction through Stellar Soroban JSON-RPC.

Stellar mainnetstellar:rpcstellar_read_rpc — 15 / 20 / 100 / 250 RPS (free / basic / pro / business) (default, unmeasured)

Evaluates a base64-encoded transaction envelope without submitting it and can calculate transaction data, authorizations, resource fees, events, state changes, and restore data.

Use it before a Soroban invocation or for a read-only contract call. The result is advisory input to a separate submission workflow.

sendTransaction is unavailable on this API. Optional result fields may be absent, and result.error is an execution outcome rather than a transport error.

Parameters

JSON-RPC params is a by-name object. Only the fields below are defined by the OpenRPC catalog.

transactionstringrequired

In order for the RPC server to successfully simulate a Stellar transaction, the provided transaction must contain only a single operation of the type invokeHostFunction.

resourceConfigobjectoptional

Contains configuration for how resources will be calculated when simulating transactions.

xdrFormatstringoptional

Lets the user choose the format in which the response should be returned - either as unpacked JSON or as base64-encoded XDR strings. Note that you should not rely on any schema for the JSON, as it will change when the underlying XDR changes.

authModestringoptional

Specifies the authorization mode to use when simulating the transaction. The options are 'enforce' (default, enforces all authorization checks), 'record' (records authorization without enforcement), and 'record_allow_nonroot' (records authorization while allowing non-root invocations).

Parameter sub-fieldsobject

resourceConfig.instructionLeewaynumber

Allow this many extra instructions when budgeting resources.

Response

The response is copied unchanged from the accepted fixture.

resultobject

Method result object.

result.errorstring

(optional) - This field will include details about why the invoke host function call failed. Only present if the transaction simulation failed.

result.eventsarray of string

(optional) Array of serialized base64 strings - Array of the events emitted during the contract invocation. The events are ordered by their emission time. (an array of serialized base64 strings). Only present when simulating of InvokeHostFunction operations, note that it can be present on error, providing extra context about what failed.

result.latestLedgernumber

The sequence number of the latest ledger known to Stellar RPC at the time it handled the request.

result.minResourceFeestring

(optional) Stringified number - Recommended minimum resource fee to add when submitting the transaction. This fee is to be added on top of the Stellar network fee. Not present in case of error.

result.restorePreambleobject

(optional) - It can only be present on successful simulation (i.e. no error) of InvokeHostFunction operations. If present, it indicates that the simulation detected archived ledger entries which need to be restored before the submission of the InvokeHostFunction operation. The minResourceFee and transactionData fields should be used to submit a transaction containing a RestoreFootprint operation.

result.restorePreamble.minResourceFeestring

Stringified number - Recommended minimum resource fee to add when submitting the RestoreFootprint operation. This fee is to be added on top of the Stellar network fee.

result.restorePreamble.transactionDatastring

Serialized base64 string - The recommended Soroban Transaction Data to use when submitting the RestoreFootprint operation.

result.resultsarray of object

(optional) - This array will only have one element: the result for the Host Function invocation. Only present on successful simulation (i.e. no error) of InvokeHostFunction operations.

result.results[].autharray of string

Array of serialized base64 strings - Per-address authorizations recorded when simulating this Host Function call.

result.results[].xdrstring

Serialized base64 string - return value of the Host Function call.

result.stateChangesarray of object

(optional) - On successful simulation of InvokeHostFunction operations, this field will be an array of LedgerEntrys before and after simulation occurred. Note that at least one of before or after will be present: before and no after indicates a deletion event, the inverse is a creation event, and both present indicates an update event. Or just check the type.

result.stateChanges[].afterstring or null

Base64, if present - LedgerEntry state after simulation

result.stateChanges[].beforestring or null

Base64, if present - LedgerEntry state prior to simulation

result.stateChanges[].keystring

Base64 - the LedgerKey for this delta

result.stateChanges[].typestring

Indicates if the entry was created, updated, or deleted

result.transactionDatastring

(optional) Serialized base64 string - The recommended Soroban Transaction Data to use when submitting the simulated transaction. This data contains the refundable fee and resource usage information such as the ledger footprint and IO access data (serialized in a base64 string). Not present in case of error.

Errors

Errors use the standard JSON-RPC envelope. See Stellar errors and the shared error reference.

Code	Meaning	When it happens
`-32602`	Invalid params	the by-name object or a field has the wrong type; positional-array style params are rejected.
`-32601`	Method not found	The method is absent from the published Stellar OpenRPC catalog.
`401`	Unauthorized	The API key is missing or invalid.
`429`	Rate limited	The `stellar_read_rpc` RPS budget is exceeded.

Examples

JavaScript (fetch)

JavaScript

const request = {
  "jsonrpc": "2.0",
  "id": 1,
  "method": "simulateTransaction",
  "params": {
    "transaction": "${stellar.transaction_xdr}"
  }
};
const response = await fetch("https://triport.io/rpc/stellar", {
  method: "POST",
  headers: {
    "x-token": process.env.TRIPORT_API_KEY,
    "Content-Type": "application/json",
  },
  body: JSON.stringify(request),
});
const payload = await response.json();
if (!response.ok || payload.error) throw new Error(JSON.stringify(payload.error));
console.log(payload.result);

Notes

Simulation does not guarantee a later submission result.
Fee-like values are string encoded.
Related: getLedgerEntries and getEvents; transaction submission is unavailable.
This is a read-only surface. No write or transaction-submission method is published.

Request

cURLJavaScriptPython

curl https://triport.io/rpc/stellar \
  -H "x-token: $TRIPORT_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "simulateTransaction",
  "params": {
    "transaction": "${stellar.transaction_xdr}"
  }
}'

const res = await fetch("https://triport.io/rpc/stellar", {
  method: "POST",
  headers: {
    "x-token": "$TRIPORT_API_KEY",
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "jsonrpc": "2.0",
    "id": 1,
    "method": "simulateTransaction",
    "params": {
      "transaction": "${stellar.transaction_xdr}"
    }
  }),
});
const data = await res.json();
console.log(data);

import requests


resp = requests.post(
    "https://triport.io/rpc/stellar",
    headers={
        "x-token": "$TRIPORT_API_KEY",
        "Content-Type": "application/json",
    },
    json={
        "jsonrpc": "2.0",
        "id": 1,
        "method": "simulateTransaction",
        "params": {
            "transaction": "${stellar.transaction_xdr}",
        },
    },
)
data = resp.json()
print(data)

ResponseExample

JSON

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "latestLedger": 64234094,
    "minResourceFee": "100",
    "results": []
  }
}