[Amazon.Lambda.RuntimeSupport] RIC headers shouldn't be case sensitive

[duncanista]

Describe the bug

RIC expects to get case sensitive (capitalized kebab case) headers from the Lambda Runtime API.

aws-lambda-dotnet/Libraries/src/Amazon.Lambda.RuntimeSupport/Client/RuntimeApiHeaders.cs

Lines 22 to 28 in 3c68321

	internal const string HeaderAwsRequestId = "Lambda-Runtime-Aws-Request-Id";
	internal const string HeaderTraceId = "Lambda-Runtime-Trace-Id";
	internal const string HeaderClientContext = "Lambda-Runtime-Client-Context";
	internal const string HeaderCognitoIdentity = "Lambda-Runtime-Cognito-Identity";
	internal const string HeaderDeadlineMs = "Lambda-Runtime-Deadline-Ms";
	internal const string HeaderInvokedFunctionArn = "Lambda-Runtime-Invoked-Function-Arn";

Regression Issue

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

Expected Behavior

This should be case insensitive.

It works perfectly for NodeJS

https://github.com/aws/aws-lambda-nodejs-runtime-interface-client/blob/a5ae1c2a92708e81c9df4949c60fd9e1e6e46bed/src/InvokeContext.js#L14-L22

-- edit:

Also works perfectly for Java, Python, and Ruby

Current Behavior

When building a rust Proxy Server for the Lambda Runtime API, I get the following error when working in .NET functions.

Unhandled exception. System.Collections.Generic.KeyNotFoundException: The given key 'Lambda-Runtime-Aws-Request-Id' was not present in the dictionary.
--
  | 2025-06-17T19:10:32.131Z | at System.Collections.Generic.Dictionary`2.get_Item(TKey key)
  | 2025-06-17T19:10:32.131Z | at Amazon.Lambda.RuntimeSupport.RuntimeApiHeaders..ctor(Dictionary`2 headers) in /src/Repo/Libraries/src/Amazon.Lambda.RuntimeSupport/Client/RuntimeApiHeaders.cs:line 32
  | 2025-06-17T19:10:32.131Z | at Amazon.Lambda.RuntimeSupport.RuntimeApiClient.GetNextInvocationAsync(CancellationToken cancellationToken) in /src/Repo/Libraries/src/Amazon.Lambda.RuntimeSupport/Client/RuntimeApiClient.cs:line 112
  | 2025-06-17T19:10:32.131Z | at Amazon.Lambda.RuntimeSupport.LambdaBootstrap.InvokeOnceAsync(CancellationToken cancellationToken) in /src/Repo/Libraries/src/Amazon.Lambda.RuntimeSupport/Bootstrap/LambdaBootstrap.cs:line 261
  | 2025-06-17T19:10:32.131Z | at Amazon.Lambda.RuntimeSupport.LambdaBootstrap.RunAsync(CancellationToken cancellationToken) in /src/Repo/Libraries/src/Amazon.Lambda.RuntimeSupport/Bootstrap/LambdaBootstrap.cs:line 224
  | 2025-06-17T19:10:32.131Z | at Amazon.Lambda.RuntimeSupport.RuntimeSupportInitializer.RunLambdaBootstrap() in /src/Repo/Libraries/src/Amazon.Lambda.RuntimeSupport/RuntimeSupportInitializer.cs:line 70
  | 2025-06-17T19:10:32.131Z | at Amazon.Lambda.RuntimeSupport.Program.Main(String[] args) in /src/Repo/Libraries/src/Amazon.Lambda.RuntimeSupport/Program.cs:line 48
  | 2025-06-17T19:10:32.131Z | at Amazon.Lambda.RuntimeSupport.Program.<Main>(String[] args)

Reproduction Steps

Build a Lambda Runtime API proxy in Rust, then just do a bypass and see how it fails for .NET

Possible Solution

Making header lookup case insensitive

Additional Information/Context

No response

AWS .NET SDK and/or Package version used

n/a

Targeted .NET Platform

.NET 6 and .NET 8

Operating System and version

AWS Lambda

[duncanista]

Closing due to the release of 2025_08_01

[github-actions]

Comments on closed issues are hard for our team to see.
If you need more assistance, please either tag a team member or open a new issue that references this one.
If you wish to keep having a conversation with other community members under this issue feel free to do so.

[duncanista]

Re-opening because I'm still seeing the issue in Lambda

[duncanista]

Hey @GarrettBeatty,

Hope everything is going well! Any idea if #2094 included in latest release is now included in the runtime? 🤔

[GarrettBeatty]

hi @duncanista i will double check this tomorrow!

[duncanista]

Thanks – no rush, I was just preparing to release a Rust proxy for Datadog in our Lambda Extension, and seems like .NET is the only runtime where we cannot get a successful run. For context, Rust libraries ignore casing and lowercase all headers, so it has been out of my control try to mitigate it from my side.

I think for my release I'd have to exclude .NET users for this feature while this sorts out, let me know if you want me to provide a reproduction case or something!