Agent Skill · Pulumi

pulumi-best-practices

Load when the user is writing, reviewing, or debugging Pulumi TypeScript/Python programs; asks about Output or apply() usage; wants to create ComponentResource classes; needs to refactor resources without destroying them (aliases); is setting up secrets or config; or is configuring a pulumi preview/up CI workflow. Also load for questions about resource dependency order, parent/child resource relationships, or pulumi.interpolate.

View SKILL.md on GitHub → Source repository Provider profile
Provider: Pulumi Path in repo: authoring/skills/pulumi-best-practices/SKILL.md

Skill body

Pulumi Best Practices

When to Use This Skill

Invoke this skill when:

Practices

1. Never Create Resources Inside apply()

Why: Resources created inside apply() don’t appear in pulumi preview, making changes unpredictable. Pulumi cannot properly track dependencies, leading to race conditions and deployment failures.

Detection signals:

Wrong:

const bucket = new aws.s3.Bucket("bucket");

bucket.id.apply(bucketId => {
    // WRONG: This resource won't appear in preview
    new aws.s3.BucketObject("object", {
        bucket: bucketId,
        content: "hello",
    });
});

Right:

const bucket = new aws.s3.Bucket("bucket");

// Pass the output directly - Pulumi handles the dependency
const object = new aws.s3.BucketObject("object", {
    bucket: bucket.id,  // Output<string> works here
    content: "hello",
});

When apply is appropriate:

Reference: https://www.pulumi.com/docs/concepts/inputs-outputs/

2. Pass Outputs Directly as Inputs

Why: Pulumi builds a directed acyclic graph (DAG) based on input/output relationships. Passing outputs directly ensures correct creation order. Unwrapping values manually breaks the dependency chain, causing resources to deploy in wrong order or reference values that don’t exist yet.

Detection signals:

Wrong:

const vpc = new aws.ec2.Vpc("vpc", { cidrBlock: "10.0.0.0/16" });

// WRONG: Extracting the value breaks the dependency chain
let vpcId: string;
vpc.id.apply(id => { vpcId = id; });

const subnet = new aws.ec2.Subnet("subnet", {
    vpcId: vpcId,  // May be undefined, no tracked dependency
    cidrBlock: "10.0.1.0/24",
});

Right:

const vpc = new aws.ec2.Vpc("vpc", { cidrBlock: "10.0.0.0/16" });

const subnet = new aws.ec2.Subnet("subnet", {
    vpcId: vpc.id,  // Pass the Output directly
    cidrBlock: "10.0.1.0/24",
});

For string interpolation:

// WRONG
const name = bucket.id.apply(id => `prefix-${id}-suffix`);

// RIGHT - use pulumi.interpolate for template literals
const name = pulumi.interpolate`prefix-${bucket.id}-suffix`;

// RIGHT - use pulumi.concat for simple concatenation
const name = pulumi.concat("prefix-", bucket.id, "-suffix");

Reference: https://www.pulumi.com/docs/concepts/inputs-outputs/

Why: ComponentResource classes group related resources into reusable, logical units. Without components, your resource graph is flat, making it hard to understand which resources belong together, reuse patterns across stacks, or reason about your infrastructure at a higher level.

Detection signals:

Wrong:

// Flat structure - no logical grouping, hard to reuse
const bucket = new aws.s3.Bucket("app-bucket");
const bucketPolicy = new aws.s3.BucketPolicy("app-bucket-policy", {
    bucket: bucket.id,
    policy: policyDoc,
});
const originAccessIdentity = new aws.cloudfront.OriginAccessIdentity("app-oai");
const distribution = new aws.cloudfront.Distribution("app-cdn", { /* ... */ });

Right:

interface StaticSiteArgs {
    domain: string;
    content: pulumi.asset.AssetArchive;
}

class StaticSite extends pulumi.ComponentResource {
    public readonly url: pulumi.Output<string>;

    constructor(name: string, args: StaticSiteArgs, opts?: pulumi.ComponentResourceOptions) {
        super("myorg:components:StaticSite", name, args, opts);

        // Resources created here - see practice 4 for parent setup
        const bucket = new aws.s3.Bucket(`${name}-bucket`, {}, { parent: this });
        // ...

        this.url = distribution.domainName;
        this.registerOutputs({ url: this.url });
    }
}

// Reusable across stacks
const site = new StaticSite("marketing", {
    domain: "marketing.example.com",
    content: new pulumi.asset.FileArchive("./dist"),
});

Component best practices:

For in-depth component authoring guidance (args design, multi-language support, testing, distribution), use skill pulumi-component.

Reference: https://www.pulumi.com/docs/concepts/resources/components/

4. Always Set parent: this in Components

Why: When you create resources inside a ComponentResource without setting parent: this, those resources appear at the root level of your stack’s state. This breaks the logical hierarchy, makes the Pulumi console hard to navigate, and can cause issues with aliases and refactoring. The parent relationship is what makes the component actually group its children.

Detection signals:

Wrong:

class MyComponent extends pulumi.ComponentResource {
    constructor(name: string, opts?: pulumi.ComponentResourceOptions) {
        super("myorg:components:MyComponent", name, {}, opts);

        // WRONG: No parent set - this bucket appears at root level
        const bucket = new aws.s3.Bucket(`${name}-bucket`);
    }
}

Right:

class MyComponent extends pulumi.ComponentResource {
    constructor(name: string, opts?: pulumi.ComponentResourceOptions) {
        super("myorg:components:MyComponent", name, {}, opts);

        // RIGHT: Parent establishes hierarchy
        const bucket = new aws.s3.Bucket(`${name}-bucket`, {}, {
            parent: this
        });

        const policy = new aws.s3.BucketPolicy(`${name}-policy`, {
            bucket: bucket.id,
            policy: policyDoc,
        }, {
            parent: this
        });
    }
}

What parent: this provides:

Reference: https://www.pulumi.com/docs/concepts/resources/components/

5. Encrypt Secrets from Day One

Why: Secrets marked with --secret are encrypted in state files, masked in CLI output, and tracked through transformations. Starting with plaintext config and converting later requires credential rotation, reference updates, and audit of leaked values in logs and state history.

Detection signals:

Wrong:

# Plaintext - will be visible in state and logs
pulumi config set databasePassword hunter2
pulumi config set apiKey sk-1234567890

Right:

# Encrypted from the start
pulumi config set --secret databasePassword hunter2
pulumi config set --secret apiKey sk-1234567890

In code:

const config = new pulumi.Config();

// This retrieves a secret - the value stays encrypted
const dbPassword = config.requireSecret("databasePassword");

// Creating outputs from secrets preserves secrecy
const connectionString = pulumi.interpolate`postgres://user:${dbPassword}@host/db`;
// connectionString is also a secret Output

// Explicitly mark values as secret
const computed = pulumi.secret(someValue);

Use Pulumi ESC for centralized secrets:

# Pulumi.yaml
environment:
  - production-secrets  # Pull from ESC environment

# ESC manages secrets centrally across stacks
esc env set production-secrets db.password --secret "hunter2"

What qualifies as a secret:

References:

6. Use Aliases When Refactoring

Why: Renaming resources, moving them into components, or changing parents causes Pulumi to see them as new resources. Without aliases, refactoring destroys and recreates resources, potentially causing downtime or data loss. Aliases preserve resource identity through refactors.

Detection signals:

Wrong:

// Before: resource named "my-bucket"
const bucket = new aws.s3.Bucket("my-bucket");

// After: renamed without alias - DESTROYS THE BUCKET
const bucket = new aws.s3.Bucket("application-bucket");

Right:

// After: renamed with alias - preserves the existing bucket
const bucket = new aws.s3.Bucket("application-bucket", {}, {
    aliases: [{ name: "my-bucket" }],
});

Moving into a component:

// Before: top-level resource
const bucket = new aws.s3.Bucket("my-bucket");

// After: inside a component - needs alias with old parent
class MyComponent extends pulumi.ComponentResource {
    constructor(name: string, opts?: pulumi.ComponentResourceOptions) {
        super("myorg:components:MyComponent", name, {}, opts);

        const bucket = new aws.s3.Bucket("bucket", {}, {
            parent: this,
            aliases: [{
                name: "my-bucket",
                parent: pulumi.rootStackResource,  // Was at root
            }],
        });
    }
}

Alias types:

// Simple name change
aliases: [{ name: "old-name" }]

// Parent change
aliases: [{ name: "resource-name", parent: oldParent }]

// Full URN (when you know the exact previous URN)
aliases: ["urn:pulumi:stack::project::aws:s3/bucket:Bucket::old-name"]

Lifecycle:

  1. Add alias during refactor
  2. Run pulumi up on all stacks
  3. Remove alias after all stacks updated (optional, but keeps code clean)

Reference: https://www.pulumi.com/docs/iac/concepts/resources/options/aliases/

7. Preview Before Every Deployment

Why: pulumi preview shows exactly what will be created, updated, or destroyed. Surprises in production come from skipping preview. A resource showing “replace” when you expected “update” means imminent destruction and recreation.

Detection signals:

Wrong:

# Deploying blind
pulumi up --yes

Right:

# Always preview first
pulumi preview

# Review the output, then deploy
pulumi up

What to look for in preview:

Warning signs:

CI/CD integration:

# GitHub Actions example
jobs:
  preview:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - name: Pulumi Preview
        uses: pulumi/actions@v5
        with:
          command: preview
          stack-name: production
        env:
          PULUMI_ACCESS_TOKEN: ${{ secrets.PULUMI_ACCESS_TOKEN }}

  deploy:
    needs: preview
    runs-on: ubuntu-latest
    if: github.ref == 'refs/heads/main'
    steps:
      - name: Pulumi Up
        uses: pulumi/actions@v5
        with:
          command: up
          stack-name: production

PR workflow:

References:

Quick Reference

Practice Key Signal Fix
No resources in apply new Resource() inside .apply() Move resource outside, pass Output directly
Pass outputs directly Extracted values used as inputs Use Output objects, pulumi.interpolate
Use components Flat structure, repeated patterns Create ComponentResource classes
Set parent: this Component children at root level Pass { parent: this } to all child resources
Secrets from day one Plaintext passwords/keys in config Use --secret flag, ESC
Aliases when refactoring Delete+create in preview Add alias with old name/parent
Preview before deploy pulumi up --yes Always run pulumi preview first

Validation Checklist

When reviewing Pulumi code, verify:

Skill frontmatter

version: 1.0.0