Feature request: Request to add "InvokeMode: RESPONSE_STREAM" support for SAM "Api" events to enable Lambda response streaming through API Gateway.

AWS Lambda and API Gateway support response streaming as documented in the AWS blog post
https://aws.amazon.com/blogs/compute/building-responsive-apis-with-amazon-api-gateway-response-streaming/

However, this feature is not available through SAM "Api" events

I wish sam cli should support InvokeMode: RESPONSE_STREAM
The cloud formation and cli is already supporting this property.

Code not working:

`
  ApiHandlerFun:
    Type: AWS::Serverless::Function
    Properties:
              CodeUri: apis-lambda/src
      Handler: ApiHandlerLambda.lambda_handler
      FunctionName: !Sub "${Stage}-ApiHandlerFun"
      Environment:
        Variables:
          AGENT_ID: !Ref AgentId
          AGENT_ALIAS_NAME: !Ref AgentAliasName
      Events:
        ChatStreamEventMessage:
          Type: Api
          Properties:
            RestApiId: !Ref ChatbotRestApi
            Path: /converse-stream
            Method: POST
            InvokeMode: RESPONSE_STREAM  # Enable streaming        
`

If I add above property (InvokeMode: RESPONSE_STREAM ) and run aws sam command then getting exception:
Number of errors found: 1. Resource with id [ChatStreamEventMessage] is invalid. property InvokeMode not defined for resource of type Api

SAM CLI Version: SAM CLI, version 1.144.0
Python Version:3.13

@ajaypokale

@ajaypokale Thanks for raising this feature request. In addition to what you asked, do you like to see this feature to be supported in sam local start-api?

Hello,
Is there any tentative timeline or target release in which this feature will be available?
This currently blocking our development for streaming chat endpoints used by customers.

Hi Team,
We are also facing similar situation. This feature would help us in resolving our production issue.

Please prioritize this feature.

Hello, thank you for the request! We will prioritize getting support for response streaming in SAM API events in the next week or two. Adding support for it in sam cli (i.e in sam local start-api) might take a bit longer, we will discuss internally how to prioritize that.

Checking in to see if there’s any update..

Following up !!!

Hi Team,
Waiting for an update on this case.

Seems like the PR (aws/serverless-application-model#3881) is ready to merge, but the approval workflow started failing due to a dependency failure. After that's resolved, we should be able to merge it to SAM.

Edit: The fix has now been merged, but not released yet.

Hello,
In which sam releases this feature will be available?
Thank you!

Either 1.108.0 or 1.109.0, not too sure of the status of the release.

Also, I want to confirm that this is a feature request for the Serverless Application Model itself, not necessarily the CLI? Or are you also looking for CLI support? If it's the former I can transfer this issue to that repository.

Patch is released in v1.157.1. Closing

Hello,
I was checking whether this feature is available in today’s release, but I do not see the feature ID 8606 included.

[Stable] Nightly Release v1.157.1.dev202603310901 - 2026-03-31

@bnusunny

Hello @bnusunny , @seshubaws
This feature is not available in today’s release too :(
feature ID 8606

[Stable] Nightly Release v1.157.1.dev202604070901 - 2026-04-07

I believe this should exist in the newest SAM CLI release (1.158.0). The SAM transform PR was released in 1.109.0, and that was included in the latest release of SAM CLI (linked are the release notes, where you can see that the updated version of SAM is 1.109.0).

I'm going to close this as completed, feel free to reopen if you can't confirm that it's working.

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I'm on SAM v1.158.0 and I still get the property InvokeMode not defined for resource of type Api error when trying to deploy.

@reedham-aws

@reedham-aws forgot to tag you.

@slimbu23

Hi @slimbu23 this property is available via the ResponseTransferMode property in the API event, not through InvokeMode, so should be

Events:
        ChatStreamEventMessage:
          Type: Api
          Properties:
            RestApiId: !Ref ChatbotRestApi
            Path: /converse-stream
            Method: POST
            ResponseTransferMode: RESPONSE_STREAM

Sorry for the confusion, let us know if that works for you.

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Feature request: Request to add "InvokeMode: RESPONSE_STREAM" support for SAM "Api" events to enable Lambda response streaming through API Gateway. #8606

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Feature request: Request to add "InvokeMode: RESPONSE_STREAM" support for SAM "Api" events to enable Lambda response streaming through API Gateway. #8606

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bnusunny commented on Jan 30, 2026

ajaypokale commented on Feb 11, 2026

DigitalVisionMax commented on Feb 13, 2026

seshubaws commented on Feb 13, 2026

ajaypokale commented on Feb 23, 2026

ajaypokale commented on Feb 26, 2026

ajaypokale commented on Mar 2, 2026

reedham-aws commented on Mar 2, 2026

ajaypokale commented on Mar 3, 2026

reedham-aws commented on Mar 4, 2026

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github-actions commented on Mar 26, 2026

ajaypokale commented on Mar 31, 2026

ajaypokale commented on Apr 7, 2026

reedham-aws commented on Apr 10, 2026

github-actions commented on Apr 10, 2026

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slimbu23 commented on Apr 15, 2026

slimbu23 commented on Apr 15, 2026

seshubaws commented on Apr 15, 2026

github-actions commented on Apr 15, 2026

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