AGP 9.0 has been out for a while, but I haven't really looked into what's changed and how it differs from before. After all, it's a major version upgrade. So, in this article, let's take a look at AGP 9.0 together.

Version Compatibility Comparison

First, you need to know that if you want to upgrade AGP to 9.0, some of your other components must meet the following requirements:

• Gradle: Minimum version must be 9.1.0
• SDK build tools: Minimum version 36.0.0
• NDK: Corresponding version is 28.2.13676358
• Maximum supported API Level: Cannot exceed 36.1

DSL Classes Only Implement New Public Interfaces

This is a major change in AGP 9.0. In previous AGP versions, such as 7.x or 8.x, both new interfaces and the old DSL type BaseExtension were included. This approach is like server-side interfaces: every time new features are added, the old interfaces are retained for compatibility with older online versions. The same logic applies to AGP. The result was that we kept using the old DSL types, and few people used the new interfaces. So, in version 9.0, a kind of forced update operation was performed, requiring all developers who upgrade to 9.0 to use the new interfaces. At the same time, the old Variant API access will also change. The alternatives are as follows:

Deprecated API (8.x)	Replacement (9.0)
applicationVariants, libraryVariants, testVariants, unitTestVariants	androidComponents.onVariants
variantFilter	androidComponents.beforeVariants
deviceProvider, testServer	Gradle Managed Devices
Path access like sdkDirectory, ndkDirectory, bootClasspath	androidComponents.sdkComponents
dexOptions	No direct replacement (dx has been replaced by d8)
generatePureSplits	Built-in distribution via Android App Bundle

Migration Requirements

When you decide to migrate your project's AGP to 9.0, you must pay attention to the following points:

1. Ensure the project is compatible with built-in Kotlin (no longer use org.jetbrains.kotlin.android)
2. KMP projects need to switch to the com.android.kotlin.multiplatform.library plugin
3. All internal DSL references in custom build logic must be replaced with public DSL interfaces
4. Third-party plugins must be upgraded to AGP 9.0 compatible versions

Opt-out Mechanism

Of course, whenever Google has a major update, it inevitably provides a switch for a smooth transition, for example, to handle compatibility issues caused by some third-party libraries using older AGP versions. The method is simple: set the newDsl switch to false in gradle.properties.

Of course, this convenience will be removed in AGP 10.0, which will completely eliminate the opt-out mechanism. This version is said to be released in mid-2026. Before that, in AGP 9.4, per-module opt-out will also be allowed by adding the following configuration in gradle.properties:

Built-in Kotlin Support

Another major update is that Kotlin support is built-in and enabled by default in 9.0. This means we no longer need to manually manage the KGP version in Gradle files. AGP 9.0 will automatically depend on KGP version 2.2.10 for you. However, if your project's KGP version is higher than 2.2.10, you still need to manually upgrade the built-in KGP or KSP version.

If there's an upgrade, there's also a downgrade. If the project's required KGP version is lower than the built-in version, we can only downgrade. However, before downgrading, one thing must be done: disable the built-in Kotlin feature. Otherwise, the default built-in version 2.2.10 will still be used. The way to disable it is also simple: add the following configuration in gradle.properties.

The downgrade method is slightly different from the upgrade and requires using a strict version.

However, this downgrade also has a bottom line: the minimum version that can be downgraded to is 2.0.0.

Default Value Changes

Below are the properties whose default values flipped from AGP 8.13 to 9.0. This allows you to evaluate which old version behaviors to retain during the upgrade.

Gradle Property	8.13 Default	9.0 Default	Impact
android.newDsl	false	true	New DSL enabled by default
android.builtInKotlin	false	true	Built-in Kotlin enabled by default
android.uniquePackageNames	false	true	All libraries must use unique package names
android.useAndroidx	false	true	Mandatory use of AndroidX
android.default.androidx.test.runner	false	true	Default use of AndroidJUnitRunner
android.dependency.useConstraints	true	false	Affects dependency import optimization
android.enableAppCompileTimeRClass	false	true	R class constants need refactoring (switch → if chain)
android.sdk.defaultTargetSdkToCompileSdkIfUnset	false	true	When targetSdk is not set, it defaults to compileSdk
android.onlyEnableUnitTestForTheTestedBuildType	false	true	Only enable unit tests for the tested build type
android.proguard.failOnMissingFiles	false	true	Missing ProGuard files will cause an error
android.r8.optimizedResourceShrinking	false	true	Resource shrinking optimized by default
android.r8.strictFullModeForKeepRules	false	true	Keep rules are stricter (constructors must be explicitly kept)
android.defaults.buildfeatures.resvalues	true	false	Only enable in subprojects that need resValues
android.defaults.buildfeatures.shaders	true	false	Only enable in subprojects that need shaders
android.r8.proguardAndroidTxt.disallowed	false	true	Only supports proguard-android-optimize.txt
android.r8.globalOptionsInConsumerRules.disallowed	false	true	Prohibits global options in keep files when publishing libraries
android.sourceset.disallowProvider	false	true	Must use Sources API to register generated source code
android.custom.shader.path.required	false	true	Must configure glslc.dir

Removed Features

Feature	8.x Status	9.0
Wear OS Embedded App Support	Available	Removed (wearApp configuration deleted)
androidDependencies Task	Available	Removed
sourceSets Reporting Task	Available	Removed
Density Split APK Support	Available	Removed (Use App Bundle instead)

Removed DSL Items

• AndroidSourceSet.jni (feature never worked properly)
• AndroidSourceSet.wearAppConfigurationName
• BuildType.isRenderscriptDebuggable (feature never worked properly)
• DependencyVariantSelection → Replaced by DependencySelection, which is exposed as kotlin.android.localDependencySelection
• Installation.installOptions(String), replaced by the mutable property of Installation.installOptions
• The experimental but never stabilized PostProcessing block
• ProductFlavor.setDimension → Replaced by the dimension property
• LanguageSplitOptions, only useful for the deprecated Google Play Instant experience
• DensitySplit, because the feature is no longer supported. The alternative is to use App Bundle

Removed APIs

8.x API	9.0 Replacement
AndroidComponentsExtension.finalizeDSl	finalizeDsl (case correction)
Component.transformClassesWith	Instrumentation.transformClassesWith
Component.setAsmFramesComputationMode	Instrumentation.setAsmFramesComputationMode
ComponentBuilder.enabled	ComponentBuilder.enable
DependenciesInfoBuilder.includedInApk	includedInApk
DependenciesInfoBuilder.includedInBundle	includedInBundle
GeneratesApk.targetSdkVersion	targetSdk
Variant.minSdkVersion / maxSdkVersion / targetSdkVersion	minSdk / maxSdk / targetSdk
VariantBuilder.targetSdk or targetSdkPreview	GeneratesApkBuilder.targetSdk or GeneratesApkBuilder.targetSdkPreview
VariantOutput.enable	enabled
Removed VariantBuilder.unitTestEnabled	Replaced by the more consistently named enableUnitTest on VariantBuilder subtypes that extend HasUnitTestBuilder
FeaturePlugin, FeatureExtension	Deprecated and stopped
BaseExtension.registerTransform	Deprecated and disabled

Removed Gradle Properties

• android.defaults.buildfeatures.aidl : Configure buildFeatures { aidl = true } individually in each subproject instead
• android.defaults.buildfeatures.renderscript : Configure individually in each subproject instead

Enforced Gradle Properties

• android.r8.integratedResourceShrinking : Enforced, using it will cause an error
• android.enableNewResourceShrinker.preciseShrinking : Enforced

DSL Change: CommonExtension Parameterization Removed

This is a source-level breaking change aimed at helping avoid major source-level changes in the future, but it also means that block methods need to be moved from CommonExtension to ApplicationExtension, LibraryExtension, DynamicFeatureExtension, and TestExtension.

AGP 8.13

AGP 9.0

R8 Changes

New Option: -processkotlinnullchecks

Configures how R8 handles Kotlin null checks:

Parameter Value	Behavior
keep	Make no changes
remove_message (default)	Rewrite to call getClass(), keep null check but remove message
remove	Completely remove null checks

Keep Rules No Longer Propagate to Companion Methods

• Before: Keep rules matching interface methods were automatically propagated to synthetic companion methods.
• 9.0: No longer propagates, affecting interface desugaring when minSdk < 24.

Default SourceFile Change

Changed from SourceFile to r8-map-id-<MAP_ID>, supporting automatic stack trace deobfuscation in Logcat.

Synthetic Class Name Minimization

The j$ classes in DEX generated by L8 desugaring use short name formats (like $1), no longer containing long encoded names like $$ExternalSynthetic.

Removals

• -addconfigurationdebugging support removed (using it will cause a compilation warning)
• D8Command.builder.setDesugaredLibraryKeepRuleConsumer removed
• R8Command.Builder.setDesugaredLibraryKeepRuleConsumer removed

Finally

As expected of a major version update, it has changed significantly from previous versions. Personally, I feel that for most projects, upgrading to this version requires careful planning. This might be the most troublesome upgrade ever. However, from another perspective, once you cross this hurdle, the project's build scripts will become cleaner and more maintainable. So, better to endure short-term pain than long-term discomfort—get this done sooner rather than later.