---
title: "Environment variables"
url: "/docs/block-builders/run-a-builder/environment-variables/index.md"
description: "Configuration reference for all environment variables used by the Signet builder."
---
# Environment Variables

The Builder is configured via environment variables. The following values are supported for configuration.

| Key                           | Required                                            | Description                                                                             |
| ----------------------------- | --------------------------------------------------- | --------------------------------------------------------------------------------------- |
| `HOST_CHAIN_ID`               | **Required**
  | Host-chain ID (e.g. 3151908)                                                            |
| `RU_CHAIN_ID`                 | **Required**
  | Rollup-chain ID (e.g. 88888)                                                            |
| `HOST_RPC_URL`                | **Required**
  | RPC endpoint for the host chain                                                         |
| `ROLLUP_RPC_URL`              | **Required**
  | RPC endpoint for the rollup chain                                                       |
| `TX_POOL_URL`                 | **Required**
  | Transaction pool URL (must end with /)                                                  |
| `FLASHBOTS_ENDPOINT`          | **Optional**
 | When configured, the Builder will send Signet blocks to this URL as transaction bundles |
| `TX_BROADCAST_URLS`           | **Optional**
 | Additional endpoints for blob txs (comma-separated, slash required)                     |
| `ZENITH_ADDRESS`              | **Required**
  | Zenith contract address                                                                 |
| `BUILDER_HELPER_ADDRESS`      | **Required**
  | Builder helper contract address                                                         |
| `QUINCEY_URL`                 | **Required**
  | Remote sequencer signing endpoint                                                       |
| `BUILDER_PORT`                | **Required**
  | HTTP port for the Builder (default: 8080)                                               |
| `SEQUENCER_KEY`               | **Required**
  | AWS KMS key ID _or_ local private key for sequencer signing                             |
| `BUILDER_KEY`                 | **Required**
  | AWS KMS key ID _or_ local private key for builder signing                               |
| `BUILDER_REWARDS_ADDRESS`     | **Required**
  | Address receiving builder rewards                                                       |
| `ROLLUP_BLOCK_GAS_LIMIT`      | **Optional**
 | Override for block gas limit                                                            |
| `CONCURRENCY_LIMIT`           | **Optional**
 | Max concurrent tasks the simulator uses                                                 |
| `OAUTH_CLIENT_ID`             | **Required**
  | Oauth client ID for the builder                                                         |
| `OAUTH_CLIENT_SECRET`         | **Required**
  | Oauth client secret for the builder                                                     |
| `OAUTH_AUTHENTICATE_URL`      | **Required**
  | Oauth authenticate URL for the builder for performing OAuth logins                      |
| `OAUTH_TOKEN_URL`             | **Required**
  | Oauth token URL for the builder to get an Oauth2 access token                           |
| `AUTH_TOKEN_REFRESH_INTERVAL` | **Required**
  | The OAuth token refresh interval in seconds.                                            |
| `CHAIN_NAME`                  | **Required**
  | The name of the chain (e.g. `parmigiana`)                                               |