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Cloudformation To Pulumi

PulumiOfficialPublished by Pulumi

  • Skill
  • Workflow
  • Cloud and DevOps
  • Apache-2.0
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From the author

Convert, migrate, or import AWS CloudFormation stacks or templates into Pulumi programs. Load this skill whenever a user wants to move from CloudFormation to Pulumi, convert a CFN template, import existing CloudFormation-managed resources into Pulumi, or asks about CloudFormation-to-Pulumi migration in any form. Also load when the user mentions cdk-importer in a migration context.
— the description by Pulumi

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

This skill provides a rigorous, step-by-step procedure for converting AWS CloudFormation templates into Pulumi programs. It emphasizes the use of the aws-native provider and strict adherence to CloudFormation Logical IDs to facilitate automated resource imports. The process covers information gathering, manual code conversion, handling of intrinsic functions, and post-import validation to ensure a zero-diff state between the existing stack and the new Pulumi-managed infrastructure.

What it does

  • Extracts resource inventories and templates from existing AWS CloudFormation stacks.
  • Maps CloudFormation intrinsic functions and parameters to their Pulumi TypeScript equivalents.
  • Enforces the use of CloudFormation Logical IDs as Pulumi resource names for automated import compatibility.
  • Prioritizes the aws-native provider to ensure structural alignment with CloudFormation types.
  • Provides a template for a formal migration report suitable for pull requests.
  • Guides users through the post-import validation process to ensure no unexpected infrastructure changes occur.

When to use it

  • When you need to migrate existing AWS CloudFormation stacks to Pulumi.
  • When you have a CloudFormation template and need to generate equivalent Pulumi code.
  • When you need to import existing AWS resources managed by CloudFormation into a Pulumi project.
  • When you are using cdk-importer and need to ensure your Pulumi code is correctly structured for automated matching.

Advantages

  • Ensures structural consistency between legacy CloudFormation and new Pulumi code.
  • Reduces manual effort during the import phase by leveraging Logical ID naming conventions.
  • Provides a clear, repeatable workflow for complex infrastructure migrations.
  • Minimizes the risk of drift or unintended resource replacement during the transition.

Usage examples

“I want to migrate my production CloudFormation stack named 'web-app-prod' to Pulumi. How do I start?”
The agent will guide you through verifying your AWS credentials, fetching the template, building a resource inventory, and beginning the manual conversion process using the required naming conventions.
“How do I map my CloudFormation !Sub and !GetAtt functions to Pulumi?”
The agent will provide specific TypeScript patterns, such as using pulumi.interpolate for !Sub and direct property access for !GetAtt, ensuring your code is ready for import.

Install

  1. Download the skill as a ZIP:

    https://autogineer.com/agent-skills/pulumi/cloudformation-to-pulumi/download
  2. Unzip it into the cross-client skills folder of your project:

    mkdir -p .agents/skills && unzip cloudformation-to-pulumi.zip -d .agents/skills

Documentation by Pulumi

IMPORTANT: PLAN ADJUSTMENT REQUIRED

If you have already generated a migration plan before loading this skill, you MUST:

  1. Review your existing plan against the workflows and requirements in this skill

  2. Identify any gaps, missing steps, or incorrect assumptions

  3. Update and revise your plan to align with this skill's guidance

  4. Communicate the adjusted plan to the user before proceeding

CRITICAL SUCCESS REQUIREMENTS

The migration output MUST meet all of the following:

  1. Complete Resource Coverage

    • Every CloudFormation resource MUST be represented in the Pulumi program OR explicitly justified in the final report.

  2. CloudFormation Logical ID as Resource Name

    • CRITICAL: Every Pulumi resource MUST use the CloudFormation Logical ID as its resource name.

    • This enables the cdk-importer tool to automatically find import IDs.

    • DO NOT rename resources. Automated import will FAIL if you change the logical IDs.

  3. Successful Deployment

    • The produced Pulumi program must be structurally valid and capable of a successful pulumi preview (assuming proper config).

  4. Zero-Diff Import Validation (if importing existing resources)

    • After import, pulumi preview must show NO updates, replaces, creates, or deletes.

  5. Final Migration Report

    • Always output a formal migration report suitable for a Pull Request.

WHEN INFORMATION IS MISSING

If the user has not provided a CloudFormation template, you MUST fetch it from AWS using the stack name.

MIGRATION WORKFLOW

Follow this workflow exactly and in this order:

1. INFORMATION GATHERING
1.1 Verify AWS Credentials (ESC)

Running AWS commands requires credentials loaded via Pulumi ESC.

  • If the user has already provided an ESC environment, use it.

  • If no ESC environment is specified, ask the user which ESC environment to use before proceeding.

For detailed ESC information: Use skill pulumi-esc.

You MUST confirm the AWS region with the user.

1.2 Get the CloudFormation Template

If user provided a template file: Read the template directly.

If user only provided a stack name: Fetch the template from AWS:

aws cloudformation get-template \
  --region <region> \
  --stack-name <stack-name> \
  --query 'TemplateBody' \
  --output json > template.json
1.3 Build Resource Inventory

List all resources in the stack:

aws cloudformation list-stack-resources \
  --region <region> \
  --stack-name <stack-name> \
  --output json

This provides:

  • LogicalResourceId - Use this as the Pulumi resource name

  • PhysicalResourceId - The actual AWS resource ID

  • ResourceType - The CloudFormation resource type

1.4 Analyze Template Structure

Extract from the template:

  • Parameters and their defaults

  • Mappings

  • Conditions

  • Outputs

  • Resource dependencies (Ref, GetAtt, DependsOn)

2. CODE CONVERSION (CloudFormation → Pulumi)

IMPORTANT: There is NO automated conversion tool for CloudFormation. You MUST convert each resource manually.

2.1 Resource Name Convention (CRITICAL)

Every Pulumi resource MUST use the CloudFormation Logical ID as its name.

// CloudFormation:
// "MyAppBucketABC123": { "Type": "AWS::S3::Bucket", ... }

// Pulumi - CORRECT:
const myAppBucket = new aws.s3.Bucket("MyAppBucketABC123", { ... });

// Pulumi - WRONG (DO NOT do this - import will fail):
const myAppBucket = new aws.s3.Bucket("my-app-bucket", { ... });

This naming convention is REQUIRED because the cdk-importer tool matches resources by name.

2.2 Provider Strategy

⚠️ CRITICAL: ALWAYS USE aws-native BY DEFAULT ⚠️

  • Use aws-native for all resources unless there's a specific reason to use aws.

  • CloudFormation types map directly to aws-native (e.g., AWS::S3::Bucket → aws-native.s3.Bucket).

  • Only use aws (classic) when aws-native doesn't support a required feature.

This is MANDATORY for successful imports with cdk-importer. The cdk-importer works by matching CloudFormation resources to Pulumi resources, and CloudFormation maps 1:1 to aws-native. Using the classic aws provider will cause import failures.

2.3 CloudFormation Intrinsic Functions

Map CloudFormation intrinsic functions to Pulumi equivalents:

CloudFormationPulumi Equivalent
!Ref (resource)Resource output (e.g., bucket.id)
!Ref (parameter)Pulumi config
!GetAtt Resource.AttrResource property output
!Sub "..."pulumi.interpolate
!Join [delim, [...]]pulumi.interpolate or .apply()
!If [cond, true, false]Ternary operator
!Equals [a, b]=== comparison
!Select [idx, list]Array indexing with .apply()
!Split [delim, str].apply(v => v.split(...))
Fn::ImportValueStack references or config
Example: !Sub
// CloudFormation: !Sub "arn:aws:s3:::${MyBucket}/*"
// Pulumi:
const bucketArn = pulumi.interpolate`arn:aws:s3:::${myBucket.bucket}/*`;
Example: !GetAtt
// CloudFormation: !GetAtt MyFunction.Arn
// Pulumi:
const functionArn = myFunction.arn;
2.4 CloudFormation Conditions

Convert CloudFormation conditions to TypeScript logic:

// CloudFormation:
// "Conditions": {
//   "CreateProdResources": { "Fn::Equals": [{ "Ref": "Environment" }, "prod"] }
// }

// Pulumi:
const config = new pulumi.Config();
const environment = config.require("environment");
const createProdResources = environment === "prod";

if (createProdResources) {
  // Create production-only resources
}
2.5 CloudFormation Parameters

Convert parameters to Pulumi config:

// CloudFormation:
// "Parameters": {
//   "InstanceType": { "Type": "String", "Default": "t3.micro" }
// }

// Pulumi:
const config = new pulumi.Config();
const instanceType = config.get("instanceType") || "t3.micro";
2.6 CloudFormation Mappings

Convert mappings to TypeScript objects:

// CloudFormation:
// "Mappings": {
//   "RegionMap": {
//     "us-east-1": { "AMI": "ami-12345" },
//     "us-west-2": { "AMI": "ami-67890" }
//   }
// }

// Pulumi:
const regionMap: Record<string, { ami: string }> = {
  "us-east-1": { ami: "ami-12345" },
  "us-west-2": { ami: "ami-67890" },
};
const ami = regionMap[aws.config.region!].ami;
2.7 Custom Resources

CloudFormation Custom Resources (AWS::CloudFormation::CustomResource or Custom::*) require special handling:

  1. Identify the purpose: Read the Lambda function code to understand what it does

  2. Find native replacement: Check if Pulumi has a native resource that provides the same functionality

  3. If no replacement: Document in the migration report that manual implementation is needed

2.8 TypeScript Output Handling

aws-native outputs often include undefined. Avoid ! non-null assertions. Always safely unwrap with .apply():

// WRONG
functionName: lambdaFunction.functionName!,

// CORRECT
functionName: lambdaFunction.functionName.apply(name => name || ""),
3. RESOURCE IMPORT

After conversion, import existing resources to be managed by Pulumi.

3.0 Pre-Import Validation (REQUIRED)

Before proceeding with import, verify your code:

  1. Check Provider Usage: Scan your code to ensure all resources use aws-native

  2. Document Exceptions: Any use of aws (classic) provider must be justified

  3. Verify Resource Names: Confirm all resources use CloudFormation Logical IDs as names

3.1 Automated Import with cdk-importer

Because you used CloudFormation Logical IDs as resource names, you can use the cdk-importer tool to automatically import resources.

Follow cfn-importer.md for detailed import procedures.

3.2 Manual Import for Failed Resources

For resources that fail automatic import:

  1. Follow cloudformation-id-lookup.md to find the import ID format

  2. Use pulumi import:

pulumi import <pulumi-resource-type> <logical-id> <import-id>
3.3 Running Preview After Import

After import, run pulumi preview. There must be:

  • NO updates

  • NO replaces

  • NO creates

  • NO deletes

If there are changes, investigate and update the program until preview is clean.

OUTPUT FORMAT (REQUIRED)

When performing a migration, always produce:

  1. Overview (high-level description)

  2. Migration Plan Summary

  3. Pulumi Code Outputs (TypeScript; organized by file)

  4. Resource Mapping Table:

CloudFormation Logical IDCFN TypePulumi TypeProvider
MyAppBucketABC123AWS::S3::Bucketaws-native.s3.Bucketaws-native
MyLambdaFunction456AWS::Lambda::Functionaws-native.lambda.Functionaws-native
  1. Custom Resources Summary (if any)

  2. Final Migration Report (PR-ready)

  3. Next Steps (import instructions)

FOR DETAILED DOCUMENTATION

Fetch content from official Pulumi documentation:

Files

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Requirements and compatibility

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Needs: Needs a command-line tool

Security

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Attribution and licence

Published by
Pulumi
Publisher
Pulumi (Official)
Source
pulumi/agent-skills · migration/skills/cloudformation-to-pulumi · commit 82f222a
Licence
Apache License 2.0 (redistribution allowed)
  • LICENSE (added by AutoGineer from LICENSE)
  • ATTRIBUTION.md (written by AutoGineer)
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