> ## Documentation Index
> Fetch the complete documentation index at: https://docs.polygon.technology/llms.txt
> Use this file to discover all available pages before exploring further.

# Introduction

> What Heimdall-v2 is, what it does in the Polygon PoS architecture, and how it differs from the original Heimdall.

Heimdall-v2 is the consensus client at the core of the Polygon PoS network. It is a complete rewrite of the original Heimdall, built on a fork of [Cosmos SDK](https://github.com/0xPolygon/cosmos-sdk) (`v0.50.13`) and a fork of [CometBFT](https://github.com/0xPolygon/cometbft/) (`v0.38.17`).

Heimdall-v2 performs the following functions:

* Manages validators and their stake.
* Handles block producer selection for the Bor layer.
* Facilitates span management.
* Orchestrates the state sync mechanism between Ethereum and Polygon PoS.
* Handles checkpoints: periodic Merkle root submissions of Bor block data to Ethereum.
* Handles milestones: fast deterministic finality within 2 to 5 seconds, using vote extensions.

## Modules

Heimdall-v2 uses modified versions of some Cosmos SDK modules and a set of fully custom modules:

* **Modified Cosmos SDK modules**: `auth`, `bank`, `gov`
* **Custom modules**: `bor`, `chainmanager`, `checkpoint`, `clerk`, `milestone`, `stake`, `topup`

## GitHub repository

For setup instructions and configuration details, see the [Heimdall-v2 README](https://github.com/0xPolygon/heimdall-v2/blob/develop/README.md).