bug: appconfigdata GetLatestConfiguration endpoint doesn't match AWS for Feature Flags #13316
Description
Is there an existing issue for this?
- I have searched the existing issues
Current Behavior
When setting up an AppConfig "Feature Flags" configuration profile, the appconfigdata.GetLatestConfiguration endpoint returns different data than that returned by AWS. In particular it essentially regurgitates the input configuration (which, I believe, matches a "Freeform" AppConfig configuration) where AWS transforms it.
Unfortunately, this means AWS's suggested AppConfig Agent doesn't work with LocalStack, as it expects the data to be in the transformed AWS format to be able to query feature flag values.
Expected Behavior
Match AWS output.
How are you starting LocalStack?
With the localstack script
Steps To Reproduce
How are you starting localstack (e.g., bin/localstack command, arguments, or docker-compose.yml)
localstack start -d
Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)
Setup:
awslocal appconfig create-application --name "Testing"
# Take application-id from output of command above
awslocal appconfig create-environment --application-id 0226a44 --name "Testing"
awslocal appconfig create-configuration-profile --application-id 0226a44 --name "Testing" --location-uri hosted --type AWS.AppConfig.FeatureFlags
awslocal appconfig create-hosted-configuration-version --application-id 0226a44 --configuration-profile-id 13f663c --content $(echo '{"flags":{"debug":{"description": "Enable debug logging", "name": "Debug Mode"}},"values":{"debug":{"enabled":true}}}' | base64) --content-type application/json appconfig-local-out.json
awslocal appconfig create-deployment-strategy --name "Testing" --deployment-duration-in-minutes 0 --growth-factor 100
awslocal appconfig start-deployment --application-id 0226a44 --environment-id e142d97 --deployment-strategy-id bb8778c --configuration-profile-id 13f663c --configuration-version 1
Start AppConfig configuration session:
awslocal appconfigdata start-configuration-session --application-id 0226a44 --environment-id e142d97 --configuration-profile-id 13f663c
awslocal appconfigdata get-latest-configuration --configuration-token a99f5cf7 appconfig-local.json
The contents of the outfile will be:
{"flags":{"debug":{"description": "Enable debug logging", "name": "Debug Mode"}},"values":{"debug":{"enabled":true}}}
Following the same set of steps on AWS nets you the following outfile:
{"debug":{"enabled":true}}
Environment
- OS: MacOS Sequoia 15.6
- LocalStack:
LocalStack version: 4.8.1
LocalStack Docker image sha: d496c653c36ff6d52f40d3282f8fd27fe0f10b5edd28e14a209430a03e65aae3 tag: 4.8.1-bigdata
LocalStack build date: 2025-09-16
LocalStack build git hash: 7aa409536Anything else?
Happy to help and provide more information. I'm currently using AppConfig Agent as an ECS sidecar, which otherwise works within LocalStack - it just returns 404 not found messages when the configuration is queried because the data it gets isn't in the format expected.