getFeeForMessage

getFeeForMessage quotes the fee, in lamports, that the cluster will charge to land a given transaction message. You pass a compiled, base-64-encoded message (the transaction without its signatures), and the node computes the fee against a recent fee schedule and the blockhash embedded in the message.

Use this to show users an estimated cost before they sign and submit a transaction. The fee depends on the message contents (number of signatures, any compute-budget instructions) and on the network's current fee state, so quote it close to submission time rather than caching it.

The blockhash inside the message must still be valid. If it has expired, the node cannot price the message and value comes back null — re-fetch a recent blockhash, rebuild the message, and call again.

JSON-RPC params is a positional array: [message, config?].

When the message's blockhash has expired, value is null:

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "context": {
      "slot": 348392041,
      "apiVersion": "2.0.18"
    },
    "value": null
  }
}

Errors are returned in the standard JSON-RPC error envelope. See the shared errors reference for the full envelope shape and shared codes.

A successful call whose message blockhash has expired is not an error — it returns result.value: null. Always null-check value before using it.

JavaScript (fetch)

const message = "AQABAgIAAAAMAAAAAAAAAA=="; // base-64 compiled message


const res = await fetch("https://api.triport.io/v1/sol", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.TRIPORT_API_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    jsonrpc: "2.0",
    id: 1,
    method: "getFeeForMessage",
    params: [message, { commitment: "confirmed" }],
  }),
});


const { result } = await res.json();
if (result.value === null) {
  console.warn("Blockhash expired — rebuild the message with a fresh blockhash.");
} else {
  console.log(`Fee: ${result.value} lamports (${result.value / 1e9} SOL)`);
}

TypeScript SDK (@triport/sdk)

import { TriportClient } from "@triport/sdk";


const client = new TriportClient({ apiKey: process.env.TRIPORT_API_KEY });


const message = "AQABAgIAAAAMAAAAAAAAAA=="; // base-64 compiled message


const { context, value } = await client.solana.getFeeForMessage(message, {
  commitment: "confirmed",
});


if (value === null) {
  throw new Error("Message blockhash expired; fetch a fresh blockhash and retry.");
}
console.log(`Fee: ${value} lamports (slot ${context.slot})`);

Python (triport-sdk)

import os
from triport import TriportClient


client = TriportClient(api_key=os.environ["TRIPORT_API_KEY"])


message = "AQABAgIAAAAMAAAAAAAAAA=="  # base-64 compiled message


result = client.solana.get_fee_for_message(message, commitment="confirmed")


if result["value"] is None:
    raise RuntimeError("Message blockhash expired; rebuild with a fresh blockhash.")


print(f"Fee: {result['value']} lamports (slot {result['context']['slot']})")

• Message, not transaction: the input is a compiled message (base-64), not a fully signed wire-format transaction. Encode the message bytes your signing library produces before sending it.
• null means expired blockhash: a null value is the documented signal that the blockhash baked into the message is no longer recent enough to price. Re-fetch a recent blockhash, rebuild the message, and call again.
• Lamports, not SOL: value is an integer count of lamports. Divide by 1e9 to display a SOL figure.
• Quote late: fees can change with network conditions; request the quote just before signing rather than caching it.
• Related methods: pair with getLatestBlockhash to obtain a fresh blockhash for the message, and sendTransaction to submit the signed transaction once the fee is acceptable.