(< 3.14.0) Cluster and AMI creation will fail due to Python 3.9 Lambda runtime deprecation

[hgreebe]

The issue

Starting Aug 31, 2026, AWS Lambda will prevent creation of new Lambda functions using the Python 3.9 runtime.
This affects ParallelCluster's ability to create clusters and custom AMIs because these operations rely on Lambda functions that run the custom resources defined in the cluster and build image CloudFormation stacks.

Users attempting to create clusters or build images after Aug 31, 2026 will encounter CloudFormation stack deployment failures due to the inability to deploy the underlying Lambda functions. Existing clusters will
continue to operate normally.

See official documentation for further details about Lambda runtime deprecations.

Affected ParallelCluster versions, OSes and schedulers

ParallelCluster < 3.14.0.

Mitigation

You can find a detailed explanation and the mitigation of the problem here.