Error Handling Pattern

import {
  SigningStargateClient,
  GasPrice,
  TimeoutError,
  BroadcastTxError,
  isDeliverTxSuccess,
  Coin,
} from "@cosmjs/stargate";

async function sendTokens(
  client: SigningStargateClient,
  sender: string,
  recipient: string,
  amount: readonly Coin[],
): Promise<string> {
  try {
    const result = await client.sendTokens(sender, recipient, amount, "auto");

    if (isDeliverTxSuccess(result)) {
      return result.transactionHash;
    }

    // Execution failed (out of gas, insufficient funds, etc.)
    throw new Error(
      `Transaction ${result.transactionHash} failed with code ${result.code}: ${result.rawLog}`,
    );
  } catch (error) {
    if (error instanceof BroadcastTxError) {
      // CheckTx rejection — do not retry without fixing the issue
      throw error;
    }

    if (error instanceof TimeoutError) {
      // Transaction may still succeed — query later
      console.warn("Transaction submitted but not yet confirmed:", error.txId);
      throw error;
    }

    throw error;
  }
}