LocalStack team,

Like the CloudWatch protocol update last year, more AWS services will add support for additional wire protocols starting as early as May 2026. We will not be able to communicate every protocol update in advance. Therefore, it will be both safer and easier for LocalStack to adjust to reactive protocol identification.

We recently published a guide on identifying and selecting wire protocols to aid in this. This guide defines how services and tools like yours that act as a service should identify which protocol a client is using to handle it appropriately. Each wire protocol definition supported in the AWS SDKs has also been updated to include a section titled "Identification for claiming" (see Smithy RPC v2 CBOR and AWS JSON 1.0 as examples).

Thank you again for maintaining these tools and please let us know if you have any related questions or encounter issues along the way.