Outputs

Kyku provides type-safe output proxies that resolve at apply time to cloud-computed values.

How Outputs Work

Every BaseResource has an outputs property — a Proxy that returns OutputValue placeholder objects:

const vm = new Vm({ ... });
const placeholder = vm.outputs.instanceId;
// → OutputValue { resourceId: "vm-web", key: "instanceId" }
// → toString() → "${output:vm-web:instanceId}"

These placeholders are resolved to real cloud values when the resource is created (during apply).

Using Outputs

Outputs are commonly used in load balancer targets:

const webServer = new Vm({
  id: 'vm-web',
  name: 'web-server',
  // ...
});

new LoadBalancer({
  id: 'lb-web',
  name: 'web-lb',
  vpc: vpc,
  listeners: [{
    port: 80,
    protocol: 'http',
    targets: [{ vm: webServer.outputs.instanceId, port: 80 }],
  }],
});

The engine resolves webServer.outputs.instanceId to the actual instance ID after the VM is provisioned.

Per-Resource Outputs

VpcOutputs

Output	Type	Description
vpcId	string	Cloud provider VPC ID
cidr	string	VPC CIDR block
subnetIds	string[]	Auto-created subnet IDs

VmOutputs

Output	Type	Description
instanceId	string	Cloud provider instance ID
publicIp	string	Public IP address
privateIp	string	Private IP address
availabilityZone	string	AZ where instance is deployed

DatabaseOutputs

Output	Type	Description
endpoint	string	Database connection endpoint
port	number	Database listener port
databaseName	string	Initial database name

LoadBalancerOutputs

Output	Type	Description
dnsName	string	LB DNS name for CNAME records
listenerPorts	number[]	Active listener ports

BucketOutputs

Output	Type	Description
bucketName	string	Bucket name
endpoint	string	S3-compatible endpoint
arn	string	AWS ARN

DnsZoneOutputs

Output	Type	Description
zoneId	string	Zone ID
nameServers	string[]	Delegation name servers

Output Propagation

The OutputPropagator resolves output references before resources are created:

Parse config → Extract output placeholders ({output:id:key})
→ Look up placeholder in state → If found, substitute real value
→ If not found yet, resolve after resource creation

Custom Resources

Custom resources can return arbitrary outputs from their handler:

handler.apply(async (ctx) => ({
  providerId: '...',
  outputs: {
    apiKey: ctx.setSecret('sk-...'),
    endpoint: 'https://api.example.com',
  },
}));