Reading EventStream header values fails with unexpected event header ... with type ...

[Madrigal]

Acknowledgements

• I have searched (https://github.com/aws/aws-sdk/issues?q=is%3Aissue) for past instances of this issue
• I have verified all of my SDK modules are up-to-date (you can perform a bulk update with go get -u github.com/aws/aws-sdk-go-v2/...)

Describe the bug

While testing #3353 I noticed that we failed reading event stream headers

2026/03/23 15:58:07 Failed to end session: unexpected event header DataType with type eventstream.StringValue:

This is because we write these values as StringValue (or really any XXXValue) https://github.com/aws/aws-sdk-go-v2/blob/main/aws/protocol/eventstream/header.go#L142

But we try to read them as *StringValue https://github.com/aws/aws-sdk-go-v2/blob/main/internal/protocoltest/awsrestjson/deserializers.go#L13733

At the time of writing, no services live on the SDK (besides sagemakerruntimehttp2) reads from eventstream headers

$ rg 'hv, ok := headerValue' service
(no results)

Since we're in the middle of a refactor of schema deserializing, I'd rather hold off making changes until we roll this out and have more extensive event stream testing

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

Expected to be able to read this value

Current Behavior

Error is returned

Reproduction Steps

On PR #3353

Possible Solution

This is already addressed on the new schema serialization aws/smithy-go#641

If we had to roll the change before migration, we would need to change the values here to be non-pointable https://github.com/aws/aws-sdk-go-v2/blob/main/codegen/smithy-aws-go-codegen/src/main/java/software/amazon/smithy/aws/go/codegen/AwsEventStreamUtils.java#L2124

Additional Information/Context

No response

AWS Go SDK V2 Module Versions Used

latest

Compiler and Version used

x

Operating System and version

x