Flashbots MEV-REPL CLI Tool

This command-line tool provides an interactive REPL-style interface for testing and demonstrating various Flashbots MEV-Share workflows.
It is intended as a reference implementation and experimentation tool for developers exploring MEV flows such as hint decoding, backrunning, and private transaction submission

Supported Commands

send-private-tx

Sends a test private transaction using the Flashbots Protect RPC endpoint.
Demonstrates how to submit transactions privately to avoid frontrunning and failed tx.

Available tx-types flags:

weth-wrap - sends deposit on WETH contract

fake-tx - sends fake tx which does not pass simulation using CheckAndSend contract with the fake calldata.

eip7702-tx - illustrates Pectra update test workflow. The command does in 3 steps:

• construct and send SetCode transaction
• get tx_receipt and verify that auth was set correctly
• use EOA account to execute tx batchcall using BatchCallAndSponsor contract.

eth-amount - sets value for tx. By default sets to 1 wei.

hints-stream

Connects to the MEV-Share Server-Sent Events (SSE) stream and listens for real-time hint messages.
Useful for observing and debugging MEV-Share hint flows.

backrun

Illustrates a basic MEV backrun flow:

1. Sends a private transaction
2. Listens to the hint stream
3. Sends a backrun transaction when a matching hintHash is detected

tx-status

This command calls Flashbots Protect Transaction Status API and logs info txStatus.

For details, see: https://docs.flashbots.net/flashbots-protect/additional-documentation/status-api

📁 Structure

• mev/client.go: Implements a Flashbots client with methods for:

  • SendBundle
  • SimulateBundle
  • SendPrivateTx
  • GetTxStatus

• mev/stream.go: Implements the HintsStream

• cmd/mevrepl/main.go includes reference implementations for backrun, hints-streamand send-private-tx flows

Helper Contracts

Contract	Mainnet	Sepolia
WETH	0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2	0xfFf9976782d46CC05630D1f6eBAb18b2324d6B14
CheckAndSend	0xC4595E3966e0Ce6E3c46854647611940A09448d3	0xB0D90094d296DA87485C623a7f42d245A74036a0
BatchCallAndSponsor	0x775c8D470CC8d4530b8F233322480649f4FAb758	0x33ACD5b112a17c863beb2f37f785bAEf8a8f8369

Note: The following contracts, except WETH, are for testing purposes only. These contracts are not intended for production use.

🚀 Getting Started

export FLASHBOTS_ETH_PRIVATE_KEY=$1; export FLASHBOTS_ETH_PRIVATE_KEY_2=$2
NETWORK={mainnet/sepolia} go run main.go <command>

Examples

NETWORK=sepolia go run main.go backrun --eth-amount 200000000000000000 

NETWORK=mainnet go run main.go hints-stream

HintsStream

The example shows init subscription on MEV-Share hints stream. SubscriptionOpts is available to customize ping and retry timeouts, and max retries to establish connection.

ch := make(chan mev.Hint)
stream, err := mev.SubscribeHints(context.Background(), "https://mev-share.flashbots.net", ch, nil)
if err != nil {
    panic(err)
}

go func () {
    <-time.After(time.Second * 5)
    close(ch)
}()

for hint := range ch {
    fmt.Println("Parsed hint", hint)
}

if err := stream.Error(); err!=nil {
    panic("error returned from stream connection: "+err.Error())
}

Please note: This project is a WIP and not intended for production use.