Announcing the LocalStack 4.3 Release

Introduction

LocalStack 4.3 delivers a rich set of enhancements across AWS service emulation, continuing our commitment to improving the local cloud development experience. This release includes key improvements such as expanded language support and better accuracy in Transcribe, application mode integration for Managed Service for Apache Flink, and advanced features in Step Functions like aliasing and enhanced MapRun execution. We’re also introducing an experimental CloudFront Lambda@Edge implementation, allowing developers to emulate edge computing behavior and modify request/response headers dynamically. Additional enhancements like stack output visibility in CloudFormation, auto-layout in the Step Functions Resource Browser, and updates to SQS, IAM, and the Replicator tool continue to push LocalStack toward deeper AWS parity and smoother developer workflows.

Get your free LocalStack account to access the latest features and enhancements in LocalStack 4.3!

How to upgrade?

To upgrade to LocalStack 4.3 using the LocalStack CLI, run the following command to update both the LocalStack Docker image and CLI to the latest version:

localstack update all

If using LocalStack with Docker CLI or Docker Compose, update the Docker image by running:

docker pull localstack/localstack:4.3.0 # Community Edition
docker pull localstack/localstack-pro:4.3.0 # Pro Edition

Pin the LocalStack version in your docker run command or Docker Compose file to 4.3.0.

What’s new in LocalStack 4.3?

• Introduction
• How to upgrade?
• What’s new in LocalStack 4.3?
  • New CloudFront Lambda@Edge implementation
  • New Language Support and Improved Accuracy in Transcribe
  • Managed Service for Apache Flink now uses Application Mode
  • New enhancements in the Step Functions provider
  • New enhancements in the SQS provider
  • New enhancements in the IAM provider
  • View Stack outputs in the CloudFormation Resource Browser
  • Auto-Layout and Enhanced Parsing in the Step Functions Resource Browser
  • Miscellaneous
• Conclusion

New CloudFront Lambda@Edge implementation

We’re introducing an experimental feature that emulates AWS CloudFront Lambda@Edge. This feature is still under development, and functionality is limited. You can enable this feature by setting CLOUDFRONT_LAMBDA_EDGE=1 in your LocalStack configuration.

The features include:

• Support for CreateDistribution API to set up CloudFront distributions with Lambda@Edge.
• Support for modifying request and response headers dynamically.

The known limitations are:

• Lack of full support for viewer-request and viewer-response event types. Please expect inconsistencies and missing functionality.
• Include Body option is also currently not supported.

The UpdateDistribution and DeleteDistribution APIs are not yet supported for Lambda@Edge. Persistence of Lambda@Edge functions across LocalStack restarts is also not supported.

Learn more about the CloudFront Lambda@Edge provider in the LocalStack documentation.

New Language Support and Improved Accuracy in Transcribe

LocalStack 4.3 introduces support for the following languages in the Transcribe provider:

• Catalan
• Czech
• Gujarati
• Kazakh
• Korean
• Polish
• Telugu
• Uzbek
• Ukrainian

The Transcribe provider also uses updated language models for the following languages:

• Chinese
• Farsi
• Spanish
• Italian
• Russian
• Vietnamese

Learn more about the Transcribe provider in the LocalStack documentation.

Managed Service for Apache Flink now uses Application Mode

LocalStack’s Managed Service for Apache Flink (MSF) implementation now runs Flink in application mode. The previous implementation used the session mode. The switch is made to more closely replicate how Flink clusters run on AWS.

Learn more about the MSF provider in the LocalStack documentation.

New enhancements in the Step Functions provider

LocalStack’s Step Functions provider now includes the following enhancements:

• Step Functions nested MapRun execution now works correctly by making map run components stateless and ensuring proper worker creation for all nested map runs.
• Support for AWS Step Functions aliasing features are now available.
• Step Functions interpreter now supports JSONata object templates as ItemSelector declaration bodies, ensuring correct evaluation in both JSONPath and JSONata modes.

New enhancements in the SQS provider

LocalStack’s SQS provider now includes the following enhancements:

• Messages with an empty body are now rejected, ensuring that only valid messages are processed.
• Support for pagination in SQS ListQueues API, implementing MaxResults parameter functionality and NextToken generation.

New enhancements in the IAM provider

LocalStack’s IAM provider now includes the following enhancements:

• Basic CRUD functionality for IAM service-specific credentials is now supported.
• Service linked role naming to match AWS pattern (AWSServiceRoleFor<service>) has been improved with added proper policy attachment for greater parity with AWS.

View Stack outputs in the CloudFormation Resource Browser

You can now view the stack outputs in the CloudFormation Resource Browser. This feature allows you to view the outputs of a stack in the LocalStack Web Application.

Auto-Layout and Enhanced Parsing in the Step Functions Resource Browser

Step Functions Resource Browser now supports rendering graphs with auto-layouts along with improved StateFunction parsing, and has replaced the previous mermaid renderer.

Miscellaneous

• Support for resource tagging in the EKS provider.
• LocalStack’s Event Source Mapping (ESM) implementation now validates the existence of different event source resources.
• LocalStack now supports on-demand key rotation for KMS symmetric keys without imported key material, allowing up to 10 rotations per key that don’t affect automatic rotation schedules.
• Support for EKS_K3S_FLAGS configuration variable to customize the k3s cluster created by LocalStack to emulate EKS clusters.
• Support for ListTagsForResource API in the SSO Admin provider.
• Support for filters in the DescribeInstanceInformation API in the SSM provider.
• Replication support for AWS::ECR::Repository is now available for the AWS Replicator tool.
• Support for AppSync Lambda data source batch processing is now available to reduce cold starts by combining queries based on batch size or time window.
• Support for schema enforcement to the Timestream provider in LocalStack, requiring dimensions marked as REQUIRED for record insertion. Records will be rejected if they’re missing required dimension keys, ensuring compliance with Timestream schema rules.
• Support for batching of records in Stream Pollers (DynamoDB Streams/Kinesis) based on BatchSize and MaximumBatchingWindowInSeconds.

Conclusion

LocalStack 4.3 reinforces our mission to provide high-fidelity local AWS environments by enhancing developer workflows, improving service parity, and introducing smarter defaults across the platform. From better visual tooling to stronger service behavior alignment, this release represents another step toward making LocalStack a powerful, high-fidelity foundation for building and testing modern cloud applications.

Upgrade to LocalStack 4.3 today and experience these latest improvements in action!