Last updated September 11, 2026
Features added through Heroku Labs are experimental and may change without notice. These features are non-SFDC applications. Refer to your Main Services Agreement for additional information.
By default for apps that use Cloud Native Buildpacks, the app’s config vars aren’t available during CNB build. To make variables available during both build time and runtime, you can enable the Build Time Config Vars Heroku Labs feature, in the app’s project.toml:
[com.heroku.build.labs]
build_config_vars = true
To disable the feature, set build_config_vars to false in the file, or remove it from the file entirely.