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Overview

Koog is built with Kotlin Multiplatform from the ground up, enabling you to write AI agents once and deploy them across multiple platforms. The framework supports JVM, JavaScript (JS), WebAssembly (WasmJS), Android, and iOS targets.

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Supported Platforms

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Platform Tiers

Koog follows Kotlin’s native target support tiers: Tier 1 (Fully Supported)
  • iosSimulatorArm64 - iOS Simulator on Apple Silicon
  • iosArm64 - iOS devices (iPhone, iPad)
Tier 2 (Supported)
  • androidTarget - Android devices and emulators
Tier 3 (Community Supported)
  • iosX64 - iOS Simulator on Intel Macs
Cross-platform Targets
  • jvm - JVM-based platforms (Java 17+)
  • js(IR) - JavaScript with IR compiler
  • wasmJs - WebAssembly for browser and Node.js

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Build Configuration

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Multiplatform Module Setup

Koog uses convention plugins to standardize multiplatform configuration: 
// build.gradle.kts
plugins {
    id("ai.kotlin.multiplatform")
    alias(libs.plugins.kotlin.serialization)
}

kotlin {
    jvmToolchain(17)
    
    sourceSets {
        commonMain {
            dependencies {
                api("ai.koog:agents-core:$koogVersion")
                api("ai.koog:prompt-executor-openai-client:$koogVersion")
            }
        }
        
        commonTest {
            dependencies {
                implementation(kotlin("test"))
            }
        }
    }
}

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Source Set Hierarchy

Koog organizes code using a hierarchical source set structure: 
commonMain
├── jvmCommonMain (JVM + Android)
│   ├── jvmMain
│   └── androidMain
└── nonJvmCommonMain (JS + WasmJS + iOS)
    ├── jsMain
    ├── wasmJsMain
    └── appleMain (iOS targets)

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Platform-Specific Considerations

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JVM Platform

Features Available:
  • All core agent functionality
  • OpenTelemetry integration (agents-features-opentelemetry)
  • Redis caching (prompt-cache-redis)
  • All LLM provider clients
  • Spring Boot integration (koog-spring-boot-starter)
  • Ktor integration (koog-ktor)
Requirements:
  • JDK 17 or higher
  • Kotlin 2.1.21 or higher
// JVM-specific configuration
java {
    toolchain {
        languageVersion = JavaLanguageVersion.of(17)
    }
}

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Android Platform

Features Available:
  • Core agent functionality
  • All LLM provider clients
  • File-based caching
  • Ktor HTTP client
Configuration: 
android {
    compileSdk = 36
    namespace = "com.example.myagent"
    
    compileOptions {
        sourceCompatibility = JavaVersion.VERSION_17
        targetCompatibility = JavaVersion.VERSION_17
    }
}
Limitations:
  • OpenTelemetry feature requires JVM (not available on Android)
  • Use OkHttp client for better Android compatibility

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iOS Platform

Features Available:
  • Core agent functionality
  • All LLM provider clients
  • In-memory and file-based caching
  • Ktor HTTP client
XCFramework Generation: 
# Enable XCFramework build
./gradlew build -Pkoog.build.xcframework=true
Swift Integration Example: 
import KoogAgents

let agent = AIAgentBuilder()
    .withPrompt("You are a helpful assistant")
    .withModel(OpenAIModel.gpt4)
    .build()

Task {
    let response = try await agent.execute(input: "Hello")
    print(response)
}

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JavaScript (JS) Platform

Features Available:
  • Core agent functionality
  • All LLM provider clients
  • Browser and Node.js support
  • In-memory caching
Browser Usage: 
import ai.koog.agents.core.agent.AIAgent
import kotlinx.browser.window

fun main() {
    window.onload = {
        val agent = AIAgent("my-agent") {
            // Configure agent
        }
        
        GlobalScope.launch {
            val result = agent.execute("Hello")
            console.log(result)
        }
    }
}
Node.js Usage: 
import ai.koog.agents.core.agent.AIAgent

fun main() {
    runBlocking {
        val agent = AIAgent("my-agent") {
            // Configure agent
        }
        
        val result = agent.execute("Hello")
        println(result)
    }
}

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WebAssembly (WasmJS) Platform

Features Available:
  • Core agent functionality
  • All LLM provider clients
  • Browser support
  • Optimized binary size
Configuration: 
wasmJs {
    browser()
    nodejs()
    binaries.library()
}
Performance Characteristics:
  • Faster startup than JS
  • Smaller binary size with tree shaking
  • Near-native execution speed
  • Limited third-party library support

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Platform Abstractions

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Expect/Actual Pattern

Use Kotlin’s expect/actual mechanism for platform-specific implementations: 
// commonMain/Platform.kt
expect fun getPlatform(): Platform

interface Platform {
    val name: String
}

// jvmMain/Platform.kt
actual fun getPlatform(): Platform = JvmPlatform()

class JvmPlatform : Platform {
    override val name: String = "JVM ${System.getProperty("java.version")}"
}

// jsMain/Platform.kt
actual fun getPlatform(): Platform = JsPlatform()

class JsPlatform : Platform {
    override val name: String = "JavaScript"
}

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HTTP Client Selection

Koog provides multiple HTTP client implementations: 
// JVM: Use OkHttp (recommended)
dependencies {
    implementation("ai.koog:http-client-okhttp:$version")
}

// JVM: Use Java HTTP Client
dependencies {
    implementation("ai.koog:http-client-java:$version")
}

// Multiplatform: Use Ktor (all platforms)
dependencies {
    implementation("ai.koog:http-client-ktor:$version")
}

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Feature Availability Matrix

FeatureJVMAndroidiOSJSWasmJS
Core Agents✅✅✅✅✅
Graph Strategies✅✅✅✅✅
Tool Execution✅✅✅✅✅
Memory Features✅✅✅✅✅
Tracing✅✅✅✅✅
OpenTelemetry✅❌❌❌❌
Redis Cache✅❌❌❌❌
File Cache✅✅✅❌❌
In-Memory Cache✅✅✅✅✅
Spring Boot✅❌❌❌❌
Ktor✅✅✅✅✅

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Testing Across Platforms

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Run Tests on All Platforms

# All JVM tests
./gradlew jvmTest

# All JS tests
./gradlew jsTest

# All Wasm tests
./gradlew wasmJsTest

# iOS simulator tests
./gradlew iosSimulatorArm64Test

# All tests on all platforms
./gradlew allTests

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Platform-Specific Tests

// commonTest/AgentTest.kt
class AgentTest {
    @Test
    fun testBasicExecution() = runTest {
        val agent = AIAgent("test") { /* ... */ }
        val result = agent.execute("input")
        assertNotNull(result)
    }
}

// jvmTest/AgentJvmTest.kt
class AgentJvmTest {
    @Test
    fun testOpenTelemetry() {
        val agent = AIAgent("test") {
            install(OpenTelemetry) { /* JVM only */ }
        }
    }
}

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Best Practices

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1. Use Common Code First

Maximize code sharing by implementing in commonMain: 
// ✅ Good: Common implementation
class MyAgent(private val config: Config) {
    suspend fun execute(input: String): String {
        // Works on all platforms
        return llm.complete(input)
    }
}

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2. Platform-Specific Only When Needed

Use platform-specific code only for unavoidable differences: 
// ❌ Avoid: Unnecessary platform-specific code
expect fun formatDate(timestamp: Long): String

// ✅ Better: Use kotlinx-datetime (multiplatform)
import kotlinx.datetime.Instant
fun formatDate(timestamp: Long): String {
    return Instant.fromEpochMilliseconds(timestamp).toString()
}

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3. Test on Target Platforms

Always test on your deployment targets: 
# Before deploying to iOS
./gradlew iosSimulatorArm64Test

# Before deploying to browser
./gradlew jsBrowserTest

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4. Handle Platform Capabilities

// Gracefully handle platform limitations
val cache = when {
    isJvm() -> RedisPromptCache(redis)
    supportsFileSystem() -> FilePromptCache(path)
    else -> InMemoryPromptCache()
}

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Migration Guide

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Adding iOS Support to Existing Project

// 1. Add iOS targets to build.gradle.kts
kotlin {
    iosSimulatorArm64()
    iosArm64()
    iosX64()
}

// 2. Move platform-specific code
// Move: src/main/kotlin → src/jvmMain/kotlin
// Keep: Common code in src/commonMain/kotlin

// 3. Test compilation
./gradlew compileKotlinIosArm64

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Converting JVM-Only Dependencies

// Before: JVM-only dependency
dependencies {
    implementation("com.squareup.okhttp3:okhttp:4.12.0")
}

// After: Multiplatform alternative
dependencies {
    implementation("io.ktor:ktor-client-core:2.3.0")
    implementation("io.ktor:ktor-client-okhttp:2.3.0") // JVM
    implementation("io.ktor:ktor-client-darwin:2.3.0") // iOS
    implementation("io.ktor:ktor-client-js:2.3.0")     // JS
}

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