How to Build and Run MEV Plugins on Sei

Introduction

Sei’s MEV system is designed to make value extraction programmable, auditable, and operationally transparent. This guide provides a step-by-step walkthrough for experienced developers and node operators who want to implement, register, and operate MEV plugins on Sei. The approach here mirrors the technical rigor and visual clarity of Sei’s core protocol explainers.

Prerequisites

Before you begin, ensure you have:

• Proficiency with Go
• Access to the Sei node source code and build environment
• Familiarity with MEV concepts and block production

MEV Plugin Interface

A Sei MEV plugin is a Go module that implements the following interface:

// MEVPlugin defines the required methods for a plugin.
type MEVPlugin interface {
    Init(config PluginConfig) error
    OnBundleSubmission(bundle MEVBundle) (BundleResult, error)
    OnBlockProposal(ctx BlockContext, txs []Tx) ([]Tx, error)
    Shutdown() error
}

• Init: Called at plugin startup for initialization and configuration.
• OnBundleSubmission: Handles incoming MEV bundles. Use this for validation, filtering, or other custom logic.
• OnBlockProposal: Allows transaction reordering, filtering, or injection during block proposal.
• Shutdown: Cleanup logic on node shutdown.

Example: Minimal Plugin Implementation

Below is a minimal example of a plugin that accepts all bundles and does not reorder transactions. You can extend this structure to implement custom logic as needed.

package mymevplugin
 
import "github.com/sei-protocol/sei-chain/x/mev"
 
type MyPlugin struct{}
 
func (p *MyPlugin) Init(config mev.PluginConfig) error {
    // Initialization logic
    return nil
}
 
func (p *MyPlugin) OnBundleSubmission(bundle mev.MEVBundle) (mev.BundleResult, error) {
    // Accept all bundles (example)
    return mev.BundleResult{Accepted: true}, nil
}
 
func (p *MyPlugin) OnBlockProposal(ctx mev.BlockContext, txs []mev.Tx) ([]mev.Tx, error) {
    // No reordering (pass-through)
    return txs, nil
}
 
func (p *MyPlugin) Shutdown() error {
    // Cleanup logic
    return nil
}

Plugin Registration and Deployment

To register and deploy your MEV plugin:

1. Place your plugin code in the x/mev/plugins/ directory of the Sei node source.
2. Register the plugin in the node configuration file or via a CLI flag.
3. Rebuild the node binary to include your plugin.
4. Restart your node to load the new plugin.

After these steps, your plugin will be loaded and invoked as part of block production.

Submitting MEV Bundles

You can submit MEV bundles to the node using the /mev/submitBundle RPC endpoint. For example:

{
  "bundle": [{ "tx": "0xabc123...", "metadata": { "searcher": "alice" } }, { "tx": "0xdef456..." }]
}

POST this JSON to the node’s /mev/submitBundle endpoint. The plugin’s OnBundleSubmission method will process the bundle. To query plugin status, use the /mev/pluginStatus endpoint.

Security Considerations

Troubleshooting

If a plugin fails to load, verify registration and compatibility with the node version. Node crashes may indicate panics or resource exhaustion in plugin code. Rejected bundles may be due to invalid payloads or plugin logic errors. Use profiling tools to diagnose performance issues.