# Developers

- [Quickstart](/developers/quickstart.md): Your one-stop shop to start building cross-chain applications (xApps).
- [Send Messages](/developers/quickstart/send-messages.md): The on-chain API for sending cross-chain messages
- [Receive Messages](/developers/quickstart/receive-messages.md): The on-chain API for receiving cross-chain messages
- [Environments](/developers/environments.md): Interact with Nomad across testnet and mainnet environments
- [Domain (Chain) IDs](/developers/environments/domain-chain-ids.md)
- [Application Developers](/developers/application-developers.md)
- [Building xApps](/developers/application-developers/building-xapps.md)
- [SDK](/developers/application-developers/sdk.md)
- [Contracts SDK](/developers/application-developers/sdk/contracts-sdk.md)
- [Typescript SDK](/developers/application-developers/sdk/typescript-sdk.md)
- [Examples](/developers/application-developers/examples.md)
- [Ping Pong](/developers/application-developers/examples/ping-pong.md)
- [Advanced](/developers/application-developers/advanced.md)
- [Router Pattern](/developers/application-developers/advanced/router-pattern.md)
- [Node Operators](/developers/node-operators.md)
- [Running Agents Guide](/developers/node-operators/running-agents-guide.md)
- [Troubleshooting](/developers/node-operators/running-agents-guide/troubleshooting.md): Hints for dealing with common (and not so common) Agent failures.
- [Running a Watcher](/developers/node-operators/running-a-watcher.md)
- [Agent Operations](/developers/node-operators/agent-operations.md)
- [Agent Gas Values](/developers/node-operators/agent-gas-values.md)
- [The Keymaster](/developers/node-operators/the-keymaster.md)
- [Core Developers](/developers/core-developers.md)
- [Upgrade Setup](/developers/core-developers/upgrade-setup.md)
- [Deploying Contracts](/developers/core-developers/deploying-contracts.md)
- [Development](/developers/core-developers/deploying-contracts/development.md)
- [Production](/developers/core-developers/deploying-contracts/production.md)