Searcher Bundle Simulation Tool

WHAT IT DOES

The Searcher Bundle Simulation Tool enables MEV searchers and developers to simulate transaction bundles before submission. It reads pending block state, current block number, gas price, base fee, user address, wallet balance, and bundle transactions including calldata, to, value, and gas. The tool processes bundle order and simulation parameters, and reads Flashbots relay state, mev-geth state, chain ID, block timestamp, and transaction nonce. It supports simulateBundle for standard bundle simulation, bundleSimulation for dedicated simulation endpoints, and simulateWithMevGeth for mev-geth compatible simulation. The tool estimates whether a bundle will succeed without actually submitting it to the mempool.

HOW TO USE

Connect your wallet and select the target network. Enter the bundle transaction details: target addresses, calldata (hex), values in wei, and gas limits—one per line for each transaction in the bundle. Optionally set a block number override for simulation at a specific block. Choose the simulation method (simulateBundle, bundleSimulation, or simulateWithMevGeth). The tool fetches the current gas price and base fee from the pending state. Once confirmed, it runs the simulation using eth_call against the pending block (or a specified block) and reports whether each transaction succeeds. The results show which transactions pass or fail, helping you refine your bundle before submission.

TECHNICAL MECHANISM

Unlike simple transaction simulators, this executor is purpose-built for searcher bundle workflows. It reads the pending block state via eth_call with blockTag 'pending' to get the current execution context. The tool fetches fee data using getFeeData() to display current gas price and base fee for context. It builds transaction objects from user inputs, validating that calldata, targets, values, and gas limits are consistent in length. The simulation uses eth_call with optional block override, applying all transactions sequentially in the bundle order to mimic execution on the pending state. The tool supports block number overrides to simulate against historical or future block states. For MEV-specific workflows, it provides method selection for simulateBundle, bundleSimulation, and simulateWithMevGeth to match different relay endpoints. Gas costs are not incurred during simulation—only estimation. The tool reports transaction-level success or failure, with detailed error messages for debugging.

WHAT IT CANNOT SEE

This tool cannot guarantee that simulation results match actual execution due to block state changes and MEV competition. It cannot predict the exact timing of bundles or the behavior of other participants in the mempool. It also cannot detect if the bundle will be front-run or if the simulation environment differs from the real chain state. The tool cannot account for transient state changes between simulation and submission, or for bundles that depend on transactions not included in the simulation. It also cannot detect if the pending state changes between simulation and actual execution.

PLEASE NOTE

This tool supports EVM-compatible chains. Simulation does not submit the bundle to the mempool—it only estimates success. The bundle order matters; transactions are executed in the order provided. Ensure calldata, values, and gas limits are correctly formatted. Block override may produce results that differ from the current pending state. This tool is for testing and development purposes only. For production bundle submission, use the Flashbots Protect or mev-geth endpoints.