[AI] Ignore, and log, unknown parts.

firebase-ai/src/main/kotlin/com/google/firebase/ai/type/Content.kt

@@ -94,7 +94,7 @@ constructor(public val role: String? = "user", public val parts: List<Part>) {
   ) {
     internal fun toPublic(): Content {
       val returnedParts =
-        parts.map { it.toPublic() }.filterNot { it is TextPart && it.text.isEmpty() }
+        parts.filterNot { it is UnknownPart.Internal }.map { it.toPublic() }.filterNot { it is TextPart && it.text.isEmpty() }
       // If all returned parts were text and empty, we coalesce them into a single one-character
       // string
       // part so the backend doesn't fail if we send this back as part of a multi-turn interaction.

firebase-ai/src/main/kotlin/com/google/firebase/ai/type/Part.kt

@@ -18,6 +18,7 @@ package com.google.firebase.ai.type
 
 import android.graphics.Bitmap
 import android.graphics.BitmapFactory
+import android.util.Log
 import java.io.ByteArrayOutputStream
 import kotlinx.serialization.DeserializationStrategy
 import kotlinx.serialization.SerialName
@@ -270,6 +271,12 @@ internal constructor(
   }
 }
 
+
+internal data class UnknownPart(public override val isThought: Boolean = false): Part {
+  @Serializable
+  internal data class Internal(val thought: Boolean? = null): InternalPart
+}
+
 /** Returns the part as a [String] if it represents text, and null otherwise */
 public fun Part.asTextOrNull(): String? = (this as? TextPart)?.text
 
@@ -300,7 +307,10 @@ internal object PartSerializer :
       "functionResponse" in jsonObject -> FunctionResponsePart.Internal.serializer()
       "inlineData" in jsonObject -> InlineDataPart.Internal.serializer()
       "fileData" in jsonObject -> FileDataPart.Internal.serializer()
-      else -> throw SerializationException("Unknown Part type")
+      else -> {
+        Log.w("PartSerializer", "Unknown part type received, ignoring.")
+        UnknownPart.Internal.serializer()
+      }
     }
   }
 }
@@ -410,6 +420,7 @@ internal fun InternalPart.toPublic(): Part {
         thought ?: false,
         thoughtSignature
       )
+    is UnknownPart.Internal -> UnknownPart()
     else ->
       throw com.google.firebase.ai.type.SerializationException(
         "Unsupported part type \"${javaClass.simpleName}\" provided. This model may not be supported by this SDK."

firebase-ai/src/test/java/com/google/firebase/ai/VertexAIUnarySnapshotTests.kt

@@ -90,6 +90,19 @@ internal class VertexAIUnarySnapshotTests {
       }
     }
 
+  @Test
+  fun `reply including an empty part`() =
+    goldenVertexUnaryFile("unary-success-empty-part.json") {
+      withTimeout(testTimeout) {
+        val response = model.generateContent("prompt")
+
+        response.candidates.isEmpty() shouldBe false
+        response.text.shouldNotBeEmpty()
+        response.candidates.first().finishReason shouldBe FinishReason.STOP
+        response.candidates.first().content.parts.isEmpty() shouldBe false
+      }
+    }
+
   @Test
   fun `response with detailed token-based usageMetadata`() =
     goldenVertexUnaryFile("unary-success-basic-response-long-usage-metadata.json") {