Runa announced on March 31, 2026 that it was open-sourcing the Terraform module behind Tweety, its internal release manager for AWS Step Functions. The company developed the tool for its payout platform to introduce changes gradually while monitoring their effect in production.

Tweety is itself implemented as a Step Function. Runa says a Terraform-triggered deployment starts two parallel processes: one adjusts traffic weights between workflow versions, while the other evaluates health signals against thresholds defined by the engineering team.

If monitoring detects a problem, the process stops the rollout, initiates a rollback and alerts the team. Runa describes the approach as a way to bring a deployment model familiar from Lambda’s CodeDeploy support into its Step Functions and Terraform environment.

The company identifies three design rules: pin downstream dependencies to specific versions, shift traffic at the top-level workflow entry point, and keep permission changes compatible with versions that still receive traffic. It notes that shared IAM permissions require particular care because older workflows may continue running during a release.

Runa wrapped the required resources in a Terraform module so engineers can supply rollout settings without managing each underlying step. The module also coordinates notifications and uses Step Functions’ execution views and logs to help teams understand a deployment.

The company says it adopted the process across its engineering teams before publishing it for others to adapt. The module is available in the Terraform Registry under wegift/tweety-sfn/aws.