Module simulation 

Transaction simulation for pre-flight validation.

This module provides utilities for simulating transactions before submission to predict outcomes, estimate gas costs, and catch errors early.

Overview

Transaction simulation allows you to:

• Predict success/failure before spending gas
• Estimate gas costs more accurately than the gas estimator
• Debug transactions by examining execution details
• Validate payloads before committing to transactions

Multi-agent and fee-payer transactions can be simulated without collecting signatures first: use crate::Aptos::simulate_multi_agent and crate::Aptos::simulate_fee_payer with a raw multi-agent or fee-payer transaction. These use SimulateQueryOptions when you need gas estimation query parameters (e.g. estimate_gas_unit_price, estimate_max_gas_amount) on the simulate endpoint.

crate::api::FullnodeClient::simulate_transaction rewrites authenticators (see crate::transaction::types::SignedTransaction::for_simulate_endpoint) before sending so the fullnode never receives a cryptographically valid signature on the simulate path.

Example

use aptos_sdk::{Aptos, AptosConfig};
use aptos_sdk::account::{Account, Ed25519Account};

let aptos = Aptos::new(AptosConfig::testnet())?;
let account = Ed25519Account::generate();
let payload = aptos_sdk::transaction::EntryFunction::apt_transfer(
    Ed25519Account::generate().address(),
    1_000_000,
)?.into();

let result = aptos.simulate(&account, payload).await?;
if result.success() {
    println!("Estimated gas: {}", result.gas_used());
} else {
    println!("Would fail: {}", result.vm_status());
}

Structs

SimulateQueryOptions

Query options for the fullnode /transactions/simulate endpoint.

SimulatedEvent

An event from a simulated transaction.

SimulationOptions

Options for simulation.

SimulationResult

Result of a transaction simulation.

StateChange

A state change from a simulated transaction.

VmError

Detailed VM error information.

Enums

VmErrorCategory

Categories of VM errors.