Explain build error: The option setting ‘android.defaults.buildfeatures.buildconfig=true’ is deprecated.

That error is coming from Gradle / Android Gradle Plugin (AGP).
Let’s break it down:

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The error

The option setting 'android.defaults.buildfeatures.buildconfig=true' is deprecated.

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Meaning

• In your gradle.properties (or sometimes in build.gradle), there’s a setting: android.defaults.buildfeatures.buildconfig=true
• This was an old way to enable/disable the generation of the BuildConfig.java file.
• Newer versions of the Android Gradle Plugin (AGP 8.0+) deprecated this android.defaults.buildfeatures.* syntax.

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How to fix

Instead of putting it in gradle.properties, you should configure it directly in your module’s build.gradle (app/build.gradle):

android {
    buildFeatures {
        buildConfig = true
    }
}

• If you don’t actually need the BuildConfig class, you can just remove the deprecated line from gradle.properties and leave it disabled.
• If you do need it, add the above block in build.gradle.

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Why this change?

Google is moving away from global settings in gradle.properties (android.defaults.buildfeatures...) because they want all build feature configurations to be module-specific.
This makes multi-module projects easier to configure and avoids confusion.