[AI] support on-device structured output by milaGGL · Pull Request #8395 · firebase/firebase-android-sdk

milaGGL · 2026-07-06T15:42:16Z

This PR introduces Structured Output support on device, allowing developers to generate strongly-typed objects using ML Kit's backend. It defines the public API (GenerateObjectResponse and generateObject()), handles the necessary Kotlin Symbol Processing (KSP) logic for schema translation.

How to use On-Device Structured Output

Define a data class annotated with @generable (and @Guide). Note: You must provide an empty companion object so the KSP processor can generate the necessary schema extensions.
Call generateObject

import com.google.firebase.ai.annotations.Generable
@Generable
data class Recipe(
    val recipeName: String,
    @Guide(description = "A list of ingredients", minItems = 2)
    val ingredients: List<String>,
    @Guide(description = "Preparation time in minutes", minimum = 1.0)
    val prepTimeMinutes: Int
) {
    companion object
}

val schema = Recipe.firebaseAISchema()
val prompt = "Give me a recipe for chocolate chip cookies"

val response = model.generateObject(schema, prompt)
val recipe: Recipe? = response.getObject()
recipe?.let {
    println("Recipe: ${it.recipeName}")
    println("Ingredients: ${it.ingredients.joinToString()}")
    println("Prep time: ${it.prepTimeMinutes} mins")
}

github-actions · 2026-07-06T15:42:34Z

📝 PRs merging into main branch

Our main branch should always be in a releasable state. If you are working on a larger change, or if you don't want this change to see the light of the day just yet, consider using a feature branch first, and only merge into the main branch when the code complete and ready to be released.

google-oss-bot · 2026-07-06T15:42:47Z

	1 Warning
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gemini-code-assist · 2026-07-06T15:42:58Z

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google-oss-bot · 2026-07-27T21:23:42Z

The public api surface has changed for the subproject ai-logic_firebase-ai-ondevice-interop:
error: Added class com.google.firebase.ai.ondevice.interop.GenerateObjectResponse [AddedClass]
error: Added method com.google.firebase.ai.ondevice.interop.GenerativeModel.generateObject(com.google.firebase.ai.ondevice.interop.GenerateContentRequest,kotlin.reflect.KClass,kotlin.coroutines.Continuation<? super com.google.firebase.ai.ondevice.interop.GenerateObjectResponse>) [AddedAbstractMethod]

Please update the api.txt files for the subprojects being affected by this change by running ./gradlew ${subproject}:generateApiTxtFile. Also perform a major/minor bump accordingly.

milaGGL · 2026-07-28T17:52:18Z

/gemini review

gemini-code-assist

Code Review

This pull request introduces support for structured object generation (generateObject) in the on-device model interop and implementation layers, including updates to the KSP processor to generate ML Kit companion classes and support enum values in the @Guide annotation. Feedback on these changes highlights a type-safety issue in GenerateObjectResponse.kt regarding MutableList invariance, as well as an opportunity to replace unsafe non-null assertions (!!) with idiomatic safe calls in SchemaSymbolProcessorVisitor.kt.

milaGGL · 2026-07-28T20:09:41Z

/gemini review

gemini-code-assist

Code Review

This pull request introduces support for structured object generation on-device by integrating with ML Kit's schema-based generation. It updates the KSP processor to generate companion classes (_MlKitCompanion) for @Generable classes, adds the generateObject API to the on-device interop and implementation layers, and updates GenerateObjectResponse to support lazy-loading and caching of deserialized instances. The review feedback highlights several important improvements: handling nested classes correctly when resolving companion class names, refining the caching logic in GenerateObjectResponse to prevent redundant deserialization of null values, safely escaping enum values using KotlinPoet's %S specifier, and propagating KDoc-based class and property descriptions to the generated companion annotations.

milaGGL · 2026-08-04T20:07:58Z

-    assertThat(mlKitRequest.topK).isEqualTo(3)
-    assertThat(mlKitRequest.seed).isEqualTo(0)
-    assertThat(mlKitRequest.candidateCount).isEqualTo(1)
-    assertThat(mlKitRequest.maxOutputTokens).isEqualTo(256)


this is failing after the mlkit version update

what are the new values? are they similar to the values here?

maxOutputTokens is different, others are all the same. But the default value checks are completely removed as it could change in later versions and diesn't make sense to verify numbers that we did not set (default)

emilypgoogle

Gave a quick pass and left some comments

emilypgoogle · 2026-08-04T22:01:01Z

+
+  private fun isListOfGenerableClass(type: KSType): Boolean {
+    val qualifiedName = type.declaration.qualifiedName?.asString()
+    if (qualifiedName == "kotlin.collections.List" || qualifiedName == "java.util.List") {


Is it prudent to analyze hierarchy here? I can imagine weird issues if you wanted to use an immutable list or ArrayList or otherwise.

We can't safely rely on full hierarchy analysis here because we need to know exactly how to reconstruct the collection when generating the toSdk() map the MLkit response back to developer code. If a developer provided a custom list implementation and we just allowed it through, our KSP processor would generate invalid mapping code that fails to compile on their end.

However, I completely agree that we should support the common variants. I've just updated the KSP processor to explicitly support MutableList and ArrayList properties in @generable classes, along with the correct construction logic to convert them safely in the generated toSdk() method.

VinayGuthal · 2026-08-05T15:24:29Z

+
+      // 3. Save to instances list for future accesses (lazy loading) and return
+      val currentInstances =
+        insts ?: MutableList<T?>(response.candidates.size) { null }.also { instances = it }


not sure what u meant by +1.

…b.com/firebase/firebase-android-sdk into mila-support-structured-ouput-locally

initial implementation

a0ffcd5

milaGGL added 8 commits July 6, 2026 16:09

remove objectResponse from Candidate

64ef2ef

update naming, the on-device GenerateObjectResponse, and ObjectSource

35e128a

update GenerateObjectResponse

60b3c12

update the name of shadowClass property

8d670e8

update Generable

565be05

remove local dependency

b12b96d

remove debug log

e4fc45a

Merge branch 'main' into mila-support-structured-ouput-locally

f98bd5c

update api txt file

e3dbf21

milaGGL marked this pull request as ready for review July 28, 2026 14:25

milaGGL changed the title ~~initial implementation~~ [AI] support on-device structured output Jul 28, 2026

milaGGL added 2 commits July 28, 2026 12:52

Fix ConvertersTest by removing brittle ML Kit default assertions

7e1f92b

Update SchemaSymbolProcessorVisitor.kt

cda79ef

gemini-code-assist Bot reviewed Jul 28, 2026

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Comment thread ai-logic/firebase-ai/src/main/kotlin/com/google/firebase/ai/type/GenerateObjectResponse.kt Outdated

Comment thread ...-ai-ksp-processor/src/main/kotlin/com/google/firebase/ai/ksp/SchemaSymbolProcessorVisitor.kt Outdated

Address code review feedback, add dependency on genai-schema

1944371

firebase deleted a comment from google-oss-bot Jul 28, 2026

Merge branch 'main' into mila-support-structured-ouput-locally

2981a63

gemini-code-assist Bot reviewed Jul 28, 2026

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milaGGL added 4 commits August 4, 2026 11:12

Merge branch 'main' into mila-support-structured-ouput-locally

1c8e412

resolve some comments

ecd0d71

test both nested and composite Generable classes

bc0b6ff

Merge branch 'main' into mila-support-structured-ouput-locally

a665954

milaGGL commented Aug 4, 2026

View reviewed changes

Comment thread .../firebase-ai-ondevice/src/main/kotlin/com/google/firebase/ai/ondevice/GenerativeModelImpl.kt Outdated

milaGGL commented Aug 4, 2026

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Comment thread ai-logic/firebase-ai-ksp-processor/test-app/test-app.gradle.kts

milaGGL commented Aug 4, 2026

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Comment thread ai-logic/firebase-ai-ondevice/firebase-ai-ondevice.gradle.kts

milaGGL commented Aug 4, 2026

View reviewed changes

Comment thread ...ai/src/main/kotlin/com/google/firebase/ai/generativemodel/OnDeviceGenerativeModelProvider.kt

Merge branch 'main' into mila-support-structured-ouput-locally

6ea68a1

milaGGL requested a review from VinayGuthal August 4, 2026 20:17

format changelog

ca714f7

emilypgoogle reviewed Aug 4, 2026

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VinayGuthal reviewed Aug 5, 2026

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Comment thread ai-logic/firebase-ai-ksp-processor/test-app/test-app.gradle.kts Outdated

VinayGuthal reviewed Aug 5, 2026

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Comment thread ai-logic/firebase-ai/src/main/kotlin/com/google/firebase/ai/type/GenerateObjectResponse.kt Outdated

VinayGuthal reviewed Aug 5, 2026

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milaGGL added 5 commits August 7, 2026 11:39

Merge branch 'main' into mila-support-structured-ouput-locally

6c7e01b

resolve comments

69a8c59

Merge branch 'mila-support-structured-ouput-locally' of https://githu…

396f724

…b.com/firebase/firebase-android-sdk into mila-support-structured-ouput-locally

Update OnDeviceGenerativeModelProvider.kt

6794859

Update SchemaSymbolProcessorVisitor.kt

17953d2

milaGGL requested review from VinayGuthal and emilypgoogle August 7, 2026 17:54

Merge branch 'main' into mila-support-structured-ouput-locally

ef07aea

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milaGGL commented Jul 6, 2026 •

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