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Exponential

Render A2UI in Compose

Install

Section titled “Install”

One Maven artifact, at.exponential:eui-compose (minSdk 26). Its POM brings the primitives, Compose, coroutines and JNA, and the AAR carries the Rust core for arm64-v8a, armeabi-v7a and x86_64. R8 needs no extra rules.

dependencies {
    implementation("at.exponential:eui-compose:0.12.0")
}

It resolves from mavenCentral(). The whole dependency block of the guide’s app:

guides/compose/app/build.gradle.kts
import org.jetbrains.kotlin.gradle.dsl.JvmTarget


plugins {
    id("com.android.application")
    id("org.jetbrains.kotlin.android")
    id("org.jetbrains.kotlin.plugin.compose")
}


android {
    namespace = "at.exponential.guide"
    compileSdk = 36


    defaultConfig {
        applicationId = "at.exponential.guide"
        minSdk = 26
        targetSdk = 36
        versionCode = 1
        versionName = "0.1.0"
    }


    buildFeatures {
        compose = true
    }


    compileOptions {
        sourceCompatibility = JavaVersion.VERSION_17
        targetCompatibility = JavaVersion.VERSION_17
    }
}


kotlin {
    compilerOptions {
        jvmTarget = JvmTarget.JVM_17
    }
}


dependencies {
    // The SDK: the painter + host runtime (its POM brings the primitives,
    // Compose, coroutines and JNA with the native core).
    implementation("at.exponential:eui-compose:0.12.0")


    implementation("androidx.activity:activity-compose:1.12.4")
    implementation(platform("androidx.compose:compose-bom:2024.12.01"))
    implementation("androidx.compose.foundation:foundation")
    implementation("androidx.compose.material3:material3")
}

Paint a surface

Section titled “Paint a surface”

One ExponentialHost per activity, connected in onCreate and disposed in onDestroy; HostSurface paints a surface by id. The emulator reaches the host machine’s server at 10.0.2.2.

guides/compose/app/src/main/kotlin/at/exponential/guide/MainActivity.kt
package at.exponential.guide


import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.safeDrawingPadding
import androidx.compose.foundation.rememberScrollState
import androidx.compose.foundation.verticalScroll
import androidx.compose.material3.Text
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.dp
import at.exponential.ui.ExponentialUi
import at.exponential.ui.host.ExponentialHost
import at.exponential.ui.host.HostOptions
import at.exponential.ui.host.HostSurface
import at.exponential.ui.host.JsonlStreamTransport
import at.exponential.ui.theme.Mode
import at.exponential.ui.theme.ThemeHandle


class MainActivity : ComponentActivity() {
    // One host per app: A2UI messages in over a transport, actions back out.
    private val host = ExponentialHost(
        HostOptions(
            transport = JsonlStreamTransport(url = "http://10.0.2.2:4300/a2ui.jsonl", postUrl = "http://10.0.2.2:4300/action"),
            theme = ThemeHandle.builtin("exponential"),
            mode = Mode.Dark,
        ),
    )


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        ExponentialUi.appContext = applicationContext // links open through it
        host.connect()
        setContent {
            // The surface the agent creates, as tall as its content: you own the scroller.
            Column(Modifier.safeDrawingPadding().verticalScroll(rememberScrollState()).padding(16.dp)) {
                HostSurface(host, "main", fallback = { Text("Waiting for the agent…") })
            }
        }
    }


    override fun onDestroy() {
        host.dispose()
        super.onDestroy()
    }
}

Host plugin

Section titled “Host plugin”

The lower-level SurfaceModel + ExponentialSurface take a HostPlugin (every member has a default; ClosureHost builds one from lambdas): icons painted under LocalContentColor, onAction, onInput (Change debounced with a revision, Commit on blur or IME Done), openUrl, fontFamily, markdown. Register theme fonts with ExponentialUi.registerFont(family, FontFamily). Details in the Compose library’s README.

Compiled in CI

Section titled “Compiled in CI”

bun packages/exponential-ui/guides/check.ts compose builds guides/compose in an empty directory against locally published Maven artifacts.