Stack Outputs

Stack outputs let resources share deployed values - within a single stack or across multiple stacks.

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How it works

Every provider resource exposes typed Output<T> fields. An Output<T> is a lazy promise: it resolves the moment the resource finishes deploying, and anything awaiting it unblocks automatically.

Resource A deploys  →  output.resolve("10.8.10.50")
                    →  Resource B (awaiting that output) unblocks and continues

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Within a stack

Resources in the same stack deploy sequentially in declaration order, so earlier outputs are always resolved by the time a later resource needs them.

@Deploy({ proxmox: CONFIG.STAGING, token: process.env.DO_TOKEN })
class Infra extends Stack {
  server = Proxmox.VM("ix-app01")
    .cores(4)
    .memory(8192)
    .ip("1.1.1.1")
    .vlan(2010);

  // server.out.ip is an Output<string> - resolves once the VM is up
  dns = DO.Domain("example.com").pointer("app", this.server.out.ip);
}

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Across stacks

Use Stack.from(TargetStack) to get a reference to another stack's instance and access its resource outputs. The target stack must be decorated with @Deploy and its module must be imported first.

// infra-stack.ts
@Deploy({ proxmox: CONFIG.STAGING })
export class InfraStack extends Stack {
  db  = Proxmox.VM("ix-db01").cores(2).memory(4096).ip("1.1.1.1").vlan(2010);
  app = Proxmox.VM("ix-app01").cores(4).memory(8192).ip("2.2.2.2").vlan(2010);
}

// dns-stack.ts
import "./infra-stack.ts"; // ensure InfraStack is registered first
import { InfraStack } from "./infra-stack.ts";

@Deploy({ token: process.env.DO_TOKEN })
class DNSStack extends Stack {
  private infra = Stack.from(InfraStack);

  dns = DO.Domain("example.com")
    .pointer("db",  this.infra.db.out.ip)   // Output<string>
    .pointer("app", this.infra.app.out.ip); // Output<string>
}

Both stacks deploy concurrently. DNSStack will wait for each Output<string> to resolve before creating the DNS records - no manual coordination needed.

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Output fields by provider

All outputs live under .out on each builder - this avoids conflicts with the builder's own configuration methods.

Provider	Builder	Output	Type
Proxmox	VMBuilder	.out.ip	Output<string>
Proxmox	VMBuilder	.out.vmid	Output<number>
DigitalOcean	DropletBuilder	.out.ip	Output<string>
DigitalOcean	DropletBuilder	.out.id	Output<number>
AWS	Route53Builder	.out.zone	Output<{ name: string; id: string }>
GCP	VMBuilder	.out.ip	Output<string>
GCP	VMBuilder	.out.id	Output<string>
Azure	AzureVMBuilder	.out.ip	Output<string>
Azure	AzureVMBuilder	.out.id	Output<string>

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Transforming outputs

Use .apply() to derive a new Output<U> from an existing one without awaiting it yourself:

const host = this.server.out.ip.apply(ip => `https://${ip}`);

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Contributing new providers

Every provider that creates a cloud resource should expose an out object with Output<T> fields for its primary identifiers (ARN, ID, IP, hostname). Resolve each field in every code path of deploy() - including existing-resource and dry-run branches - so downstream resources never hang.

import { Output } from '../../core/output.ts';

export class MyBuilder extends BaseBuilder {
  readonly out = {
    id: new Output<string>(),
  };

  async deploy() {
    if (existing) {
      this.out.id.resolve(existing.id);
      return existing;
    }
    if (dryRun) {
      this.out.id.resolve('PENDING');
      return { ... };
    }
    const result = await createResource();
    this.out.id.resolve(result.id);
    return result;
  }
}