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

# Customer Cluster

> The Stack deploys into a Kubernetes cluster the customer already runs.

## Deploying an Example App

If you're still designing your BYOC architecture, it is helpful to deploy a sample app. For the Customer Cluster architecture, see [`byo-eks`](https://github.com/nuonco/example-app-configs/tree/main/byo-eks) in `nuonco/example-app-configs`.

## Overview

[Custom nested stacks](/guides/custom-nested-stacks) wire the Runner into the cluster.

Common when the app is an agent or operator that needs in-cluster access, or when the customer requires a single shared cluster for all vendor apps.

## App config

Start from the [Customer VPC](/concepts/stacks/customer-vpc) pattern, then add [custom nested stacks](/guides/custom-nested-stacks) to wire the Runner into the existing cluster.

Customer Cluster is natively supported via the Nuon-generated CloudFormation template. Terraform deployments are also possible but require forking the published modules at [`install-stacks`](https://github.com/nuonco/install-stacks) — see the Terraform section below.

### CloudFormation

The vendor's `stack.toml` references CloudFormation nested templates plus the custom nested stacks that wire the Runner into the cluster:

```toml stack.toml theme={null}
vpc_nested_template_url    = "https://nuon-artifacts.s3.us-west-2.amazonaws.com/aws-cloudformation-templates/v0.4.0/byo-vpc/default/stack.yaml"
runner_nested_template_url = "https://nuon-artifacts.s3.us-west-2.amazonaws.com/aws-cloudformation-templates/v0.4.0/runner/asg/stack.yaml"

[[custom_nested_stacks]]
name         = "runner_sg_eks_access"   # grant the Runner SG access to the cluster
template_url = "CUSTOMER_CLOUD_DEPENDENT"
index        = 0

[[custom_nested_stacks]]
name         = "k8s_namespaces"         # create namespaces for the app
template_url = "CUSTOMER_CLOUD_DEPENDENT"
index        = 1

[[custom_nested_stacks]]
name         = "eks_access_entries"     # add EKS access entries for Runner roles
template_url = "CUSTOMER_CLOUD_DEPENDENT"
index        = 2
```

The customer enters the VPC and subnet IDs (plus the cluster name) when deploying the stack.

### Terraform

<Warning>
  Custom nested stacks are CloudFormation-only. To support Terraform deployments for this pattern, fork [`install-stacks`](https://github.com/nuonco/install-stacks) and add equivalent resources (BYO-VPC inputs, cluster security-group access, namespaces, EKS access entries) directly in the Terraform module — see [Customizing Terraform Stack Templates](/guides/customizing-terraform-stack-templates).
</Warning>

### Sandbox

The Sandbox skips cluster provisioning and consumes the customer's cluster name plus the subnet IDs from install stack outputs:

```toml sandbox.toml theme={null}
[vars]
cluster_name       = "{{.nuon.inputs.inputs.cluster_name}}"
public_subnet_ids  = "{{.nuon.install_stack.outputs.public_subnets}}"
private_subnet_ids = "{{.nuon.install_stack.outputs.private_subnets}}"
runner_subnet_id   = "{{.nuon.install_stack.outputs.runner_subnet}}"
```