Gradle 9.x, AGP 8.5+ & Kotlin 2.x Migration Guide for Capacitor Android — Kerweb Blog

Modernizing Your Android Build Pipeline

With the release of Kotlin 2.0 (K2 compiler) and recent Android Studio versions, Android build pipelines have evolved significantly. Many Capacitor developers encounter Namespace not specified errors or Java 21 compatibility conflicts.

4-Step Upgrade Guide

1. Update the Gradle Wrapper

In android/gradle/wrapper/gradle-wrapper.properties:

distributionUrl=https://services.gradle.org/distributions/gradle-8.9-all.zip

2. Configure Android Gradle Plugin (AGP)

In android/build.gradle:

dependencies {
    classpath 'com.android.tools.build:gradle:8.5.2'
    classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:2.0.20"
}

3. Set Java 17 / Java 21 Compatibility

In android/app/build.gradle:

android {
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_17
        targetCompatibility JavaVersion.VERSION_17
    }
    kotlinOptions {
        jvmTarget = '17'
    }
}

4. Clean and Sync Project

Run in your terminal:

cd android
./gradlew clean