refactor(mlkit): extract ML Kit support into a dedicated mlkit module

core/build.gradle.kts

@@ -122,7 +122,6 @@ kotlin {
         implementation(
           libs.google.auth.oauth2.http
         ) // Android compatible version or use separate for Android if needed.
-        implementation(libs.google.mlkit.genai.prompt)
         implementation(libs.androidx.room.runtime)
         implementation(libs.androidx.room.ktx)
       }

core/src/androidDeviceTest/kotlin/com/google/adk/kt/sessions/room/RoomSessionServiceInstrumentedTest.kt

@@ -20,24 +20,13 @@ import android.content.Context
 import androidx.compose.ui.test.junit4.v2.createComposeRule
 import androidx.test.ext.junit.runners.AndroidJUnit4
 import androidx.test.platform.app.InstrumentationRegistry
-import com.google.adk.kt.agents.Instruction
-import com.google.adk.kt.agents.LlmAgent
-import com.google.adk.kt.agents.RunConfig
-import com.google.adk.kt.agents.StreamingMode
 import com.google.adk.kt.annotations.FrameworkInternalApi
 import com.google.adk.kt.events.Event
-import com.google.adk.kt.models.mlkit.GenaiPrompt
-import com.google.adk.kt.runners.InMemoryRunner
 import com.google.adk.kt.sessions.SessionKey
 import com.google.adk.kt.types.Content
 import com.google.adk.kt.types.Part
 import com.google.adk.kt.types.Role
-import com.google.adk.kt.utils.mlkit.GenerativeModelHelpers
 import com.google.common.truth.Truth.assertThat
-import com.google.mlkit.genai.prompt.ModelConfig
-import com.google.mlkit.genai.prompt.ModelPreference
-import com.google.mlkit.genai.prompt.ModelReleaseStage
-import kotlinx.coroutines.flow.toList
 import kotlinx.coroutines.runBlocking
 import org.junit.After
 import org.junit.Before
@@ -49,10 +38,10 @@ import org.junit.runner.RunWith
  * On-device instrumented tests for [RoomSessionService], exercising the real Android SQLite stack
  * (the host-side `RoomSessionServiceTest` runs against a simulated DB).
  *
- * [appendEvent_persistsAcrossDatabaseReopen] is a deterministic persistence check that needs no
- * model. [runTurn_withGenaiPrompt_persistsEventsAcrossReopen] is an end-to-end check that drives a
- * real on-device Gemini Nano turn through an [InMemoryRunner] backed by [RoomSessionService],
- * mirroring the ML Kit instrumentation setup; it requires a device with AI Core / Gemini Nano.
+ * [appendEvent_persistsAcrossDatabaseReopen] and
+ * [appendEvent_partWithOpaqueData_persistsAndDropsOpaqueData] are deterministic persistence checks
+ * that need no model. The end-to-end check that drives a real on-device Gemini Nano turn through
+ * [RoomSessionService] lives in the `mlkit` module's `RoomSessionGenaiPromptInstrumentedTest`.
  */
 @RunWith(AndroidJUnit4::class)
 class RoomSessionServiceInstrumentedTest {
@@ -139,63 +128,8 @@ class RoomSessionServiceInstrumentedTest {
     }
   }
 
-  @Test
-  fun runTurn_withGenaiPrompt_persistsEventsAcrossReopen(): Unit = runBlocking {
-    // initGenerativeModel is suspend and downloads Gemini Nano if needed.
-    val generativeModel = GenerativeModelHelpers.initGenerativeModel {
-      modelConfig =
-        ModelConfig.builder()
-          .apply {
-            releaseStage = ModelReleaseStage.STABLE
-            preference = ModelPreference.FULL
-          }
-          .build()
-    }
-    val agent =
-      LlmAgent(
-        name = "room_session_agent",
-        model = GenaiPrompt.create(generativeModel, name = "gemini-nano"),
-        instruction = Instruction("You are a helpful assistant. Answer in one short sentence."),
-      )
-    val runner = InMemoryRunner(agent = agent, appName = APP_NAME, sessionService = sessionService)
-
-    val userId = "user-e2e"
-    val sessionId = "session-e2e"
-    val events =
-      runner
-        .runAsync(
-          userId = userId,
-          sessionId = sessionId,
-          newMessage = Content(role = Role.USER, parts = listOf(Part(text = QUESTION))),
-          runConfig = RunConfig(streamingMode = StreamingMode.NONE),
-        )
-        .toList()
-
-    assertThat(events).isNotEmpty()
-    assertThat(events.mapNotNull { it.errorCode }).isEmpty()
-
-    // The turn's events were persisted to the Room-backed session.
-    val key = SessionKey(APP_NAME, userId, sessionId)
-    val session = sessionService.getSession(key)
-    assertThat(session).isNotNull()
-    assertThat(session!!.events).isNotEmpty()
-
-    // And they survive a database reopen.
-    sessionService.close()
-    val reopened = RoomSessionService.fromContext(context, databaseName = TEST_DB_NAME)
-    try {
-      val persisted = reopened.getSession(key)
-      assertThat(persisted).isNotNull()
-      assertThat(persisted!!.events.map { it.id })
-        .containsAtLeastElementsIn(session.events.map { it.id })
-    } finally {
-      reopened.close()
-    }
-  }
-
   private companion object {
     const val APP_NAME = "RoomSessionServiceInstrumentedTestApp"
     const val TEST_DB_NAME = "room_session_service_instrumented_test.db"
-    const val QUESTION = "Tell me something about planet Earth."
   }
 }

examples/android/build.gradle.kts

@@ -113,6 +113,7 @@ run {
 dependencies {
   implementation(project(":google-adk-kotlin-core"))
   implementation(project(":google-adk-kotlin-firebase"))
+  implementation(project(":google-adk-kotlin-mlkit"))
   implementation(platform(libs.google.firebase.platform))
   implementation(libs.google.firebase.ai)
   implementation(libs.google.mlkit.genai.prompt)

examples/android/src/main/kotlin/com/google/adk/kt/examples/android/mlkitchat/MlKitChatActivity.kt

@@ -32,13 +32,13 @@ import com.google.adk.kt.agents.StreamingMode
 import com.google.adk.kt.examples.android.common.ScopedExampleActivity
 import com.google.adk.kt.examples.android.common.foldTextParts
 import com.google.adk.kt.examples.android.common.setExampleContentView
-import com.google.adk.kt.models.mlkit.GenaiPrompt
+import com.google.adk.kt.mlkit.GenaiPrompt
+import com.google.adk.kt.mlkit.GenerativeModelHelpers
 import com.google.adk.kt.runners.InMemoryRunner
 import com.google.adk.kt.sessions.InMemorySessionService
 import com.google.adk.kt.types.Content
 import com.google.adk.kt.types.Part
 import com.google.adk.kt.types.Role
-import com.google.adk.kt.utils.mlkit.GenerativeModelHelpers
 import kotlinx.coroutines.launch
 
 /**

examples/android/src/main/kotlin/com/google/adk/kt/examples/android/roomsession/RoomSessionActivity.kt

@@ -28,14 +28,14 @@ import com.google.adk.kt.agents.LlmAgent
 import com.google.adk.kt.examples.android.common.ScopedExampleActivity
 import com.google.adk.kt.examples.android.common.foldTextParts
 import com.google.adk.kt.examples.android.common.setExampleContentView
-import com.google.adk.kt.models.mlkit.GenaiPrompt
+import com.google.adk.kt.mlkit.GenaiPrompt
+import com.google.adk.kt.mlkit.GenerativeModelHelpers
 import com.google.adk.kt.runners.InMemoryRunner
 import com.google.adk.kt.sessions.SessionKey
 import com.google.adk.kt.sessions.room.RoomSessionService
 import com.google.adk.kt.types.Content
 import com.google.adk.kt.types.Part
 import com.google.adk.kt.types.Role
-import com.google.adk.kt.utils.mlkit.GenerativeModelHelpers
 import kotlinx.coroutines.launch
 
 /**

examples/android/src/main/kotlin/com/google/adk/kt/examples/android/skillsassetsource/WizardApprenticeAgent.kt

@@ -19,10 +19,10 @@ package com.google.adk.kt.examples.android.skillsassetsource
 import android.content.Context
 import com.google.adk.kt.agents.Instruction
 import com.google.adk.kt.agents.LlmAgent
-import com.google.adk.kt.models.mlkit.GenaiPrompt
+import com.google.adk.kt.mlkit.GenaiPrompt
+import com.google.adk.kt.mlkit.GenerativeModelHelpers
 import com.google.adk.kt.skills.AssetSkillSource
 import com.google.adk.kt.tools.SkillToolset
-import com.google.adk.kt.utils.mlkit.GenerativeModelHelpers
 
 /**
  * Builds the "wizard's apprentice" [LlmAgent] used by [SkillsAssetSourceActivity].

mlkit/build.gradle.kts

@@ -0,0 +1,121 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+plugins {
+  // Kotlin is compiled by AGP's built-in Kotlin support (no kotlin-android plugin).
+  id("com.android.library")
+  id("maven-publish")
+}
+
+// AGP's built-in Kotlin doesn't apply the kotlin.jvm/multiplatform plugins that
+// the root project pins coreLibrariesVersion on, so set it here too. Keeps the
+// published AAR on the 2.1 stdlib and consumable by Kotlin 2.1 projects.
+kotlin { coreLibrariesVersion = rootProject.extra["kotlinCoreLibrariesVersion"] as String }
+
+dependencies {
+  implementation(project(":google-adk-kotlin-core"))
+  implementation(libs.google.mlkit.genai.prompt)
+  // GenaiPromptConversions uses androidx.core.net.toUri to turn file URIs into ImageParts.
+  implementation(libs.androidx.core)
+
+  testImplementation(libs.kotlin.test.junit)
+  testImplementation(libs.androidx.test.core)
+  testImplementation(libs.androidx.test.ext.junit)
+  testImplementation(libs.androidx.test.runner)
+  testImplementation(libs.mockito.kotlin)
+  testImplementation(libs.kotlinx.coroutines.test)
+  testImplementation(libs.google.truth)
+  testImplementation(libs.robolectric)
+
+  // Instrumented tests drive the real on-device Gemini Nano model on a physical device.
+  androidTestImplementation(libs.androidx.compose.ui.test.junit4)
+  androidTestImplementation(libs.androidx.compose.ui.test.manifest)
+  // Pull espresso-core explicitly so the whole androidx.test stack resolves to the newer version
+  // that compose ui-test-junit4 alone does not force; older espresso crashes on newer Android with
+  // NoSuchMethodException android.hardware.input.InputManager.getInstance during
+  // createComposeRule().
+  androidTestImplementation(libs.androidx.test.espresso.core)
+  androidTestImplementation(libs.androidx.test.ext.junit)
+  androidTestImplementation(libs.androidx.test.rules)
+  androidTestImplementation(libs.androidx.test.runner)
+  androidTestImplementation(libs.google.truth)
+  androidTestImplementation(libs.kotlinx.coroutines.test)
+}
+
+android {
+  namespace = "com.google.adk.mlkit"
+
+  testOptions {
+    unitTests {
+      isReturnDefaultValues = true
+      isIncludeAndroidResources = true
+      all { it.systemProperty("robolectric.logging", "stderr") }
+    }
+  }
+
+  // Publishes the Android `release` variant as a single AAR with sources and
+  // javadoc jars. AGP's `withJavadocJar()` runs Gradle's `javadoc` task,
+  // which doesn't understand `.kt` sources, so the resulting jar is
+  // effectively empty - but it still satisfies Maven Central's per-module
+  // requirement. Replacing with Dokka HTML would require building the jar
+  // manually and attaching it to the AGP-created publication after
+  // evaluation; left as a follow-up.
+  publishing {
+    singleVariant("release") {
+      withSourcesJar()
+      withJavadocJar()
+    }
+  }
+
+  // The ML Kit GenAI / Gemini Nano stack pulls in androidx.core:core:1.16.0,
+  // which requires compileSdk >= 35. Pin to 36 (matching the other Android
+  // modules) even though the repo-wide default stays lower for the pure-JVM
+  // publications.
+  compileSdk { version = release(36) { minorApiLevel = 1 } }
+
+  defaultConfig {
+    minSdk = 26
+
+    testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
+  }
+
+  buildTypes {
+    release {
+      isMinifyEnabled = false
+      proguardFiles(getDefaultProguardFile("proguard-android-optimize.txt"), "proguard-rules.pro")
+    }
+  }
+}
+
+// AGP registers a software component named `release` (created by the
+// `android { publishing { singleVariant("release") { ... } } }` block above),
+// but it does NOT auto-create a `MavenPublication` for it — that's our
+// responsibility. We have to do this inside `afterEvaluate` because the
+// component itself is only registered once the Android extension finishes
+// configuring. POM metadata and GPG signing are configured in the root
+// build.gradle.kts; the root script also intentionally skips attaching the
+// Dokka javadoc jar to this publication because AGP's `withJavadocJar()`
+// above already attaches one.
+afterEvaluate {
+  publishing {
+    publications {
+      create<MavenPublication>("release") {
+        from(components["release"])
+        artifactId = "google-adk-kotlin-mlkit-android"
+      }
+    }
+  }
+}

core/src/androidDeviceTest/kotlin/com/google/adk/kt/models/mlkit/GenaiPromptInstrumentedTest.kt → mlkit/src/androidTest/kotlin/com/google/adk/kt/mlkit/GenaiPromptInstrumentedTest.kt

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package com.google.adk.kt.models.mlkit
+package com.google.adk.kt.mlkit
 
 import android.util.Log
 import androidx.compose.ui.test.junit4.v2.createComposeRule
@@ -30,7 +30,6 @@ import com.google.adk.kt.types.Blob
 import com.google.adk.kt.types.Content
 import com.google.adk.kt.types.Part
 import com.google.adk.kt.types.Role
-import com.google.adk.kt.utils.mlkit.GenerativeModelHelpers
 import com.google.common.truth.Truth.assertThat
 import com.google.mlkit.genai.prompt.ModelConfig
 import com.google.mlkit.genai.prompt.ModelPreference