Export the bucket name as a CloudFormation output with the StackVariables namespace and deploy using StackVariables.BucketName

Why the Answer Is Correct

The pipeline already contains a CloudFormation deploy action that creates the bucket and an S3 deploy action that must target that bucket, so the bucket name has to travel from the template to the later action. Adding an output named BucketName to the CloudFormation template whose value refers to the S3 bucket, and then setting the CloudFormation action's namespace to StackVariables in the pipeline, makes that output available to subsequent actions under the name StackVariables.BucketName (B). Changwha described exactly this two-part configuration, defining the BucketName output and setting the CloudFormation action's namespace to StackVariables. The S3 deploy action is then configured to take the build artifact from the build action as its input and to deploy to the bucket identified by the StackVariables.BucketName variable, which is what ties the two actions together without any hard-coded bucket name (D). f4b18ba confirmed that adding the output lets the pipeline extract the bucket name created during the stack deployment and that setting the namespace exposes it as StackVariables.BucketName. B and D are the correct combination.

Why the Other Options Are Wrong

A adds a BucketName output but sets the output's value to export to an AWS::SSM::Parameter resource named Stackvariables. An Output in a CloudFormation template exports a value from the stack to the pipeline's variable namespace; an AWS::SSM::Parameter is an entirely separate resource type that must be declared and populated explicitly. Conflating the two means the bucket name is never surfaced to the pipeline in the way the namespace mechanism provides, so the later action would have no value to consume. C configures the output artifacts of the CloudFormation action to be an AWS Systems Manager Parameter Store parameter named StackVariables with the artifact named BucketName. Pipeline output artifacts are files produced by an action, not Parameter Store parameters, so this does not deliver the bucket name as the pipeline variable the deploy action expects; it mixes up two unrelated concepts. E configures both the build artifact and the SSM parameter as inputs to the deploy action and deploys using StackVariables.BucketName. This rests on the same conflation as option C, and it is also redundant: once the CloudFormation action's namespace is set as in option B, the output is carried in the pipeline variables, so an additional Parameter Store input is neither needed nor correctly specified. B and D are correct.

Community Comment Notes

Community voted B,D unanimously. Changwha gave the two steps explicitly, defining a BucketName output in the template and setting the CloudFormation action's namespace to StackVariables, then using the StackVariables.BucketName variable in the S3 deploy action. f4b18ba explained that adding the output allows the pipeline to extract the S3 bucket name created during the stack deployment and that setting the namespace exposes it as StackVariables.BucketName. uncledana described the same dynamic deployment pattern. No alternative received support.