[AI] Chat history must store all the parts (streaming) (#7562)

rlazo · web-flow · commit 964dccc8fd90 · 2025-11-14T22:57:37.000Z
The chat history in streaming mode reconstructs the parts from their
contents, rather than storing the parts themselves. This causes
non-visible elements, like `thoughtSignature` to get lost.
diff --git a/firebase-ai/CHANGELOG.md b/firebase-ai/CHANGELOG.md
@@ -1,5 +1,6 @@
 # Unreleased
 
+- [fixed] Fixed an issue causing streaming chat interactions to drop thought signatures. (#7562)
 - [feature] Added support for server templates via `TemplateGenerativeModel` and
   `TemplateImagenModel`. (#7503)
 
diff --git a/firebase-ai/src/main/kotlin/com/google/firebase/ai/Chat.kt b/firebase-ai/src/main/kotlin/com/google/firebase/ai/Chat.kt
@@ -22,6 +22,7 @@ import com.google.firebase.ai.type.GenerateContentResponse
 import com.google.firebase.ai.type.ImagePart
 import com.google.firebase.ai.type.InlineDataPart
 import com.google.firebase.ai.type.InvalidStateException
+import com.google.firebase.ai.type.Part
 import com.google.firebase.ai.type.TextPart
 import com.google.firebase.ai.type.content
 import java.util.LinkedList
@@ -133,6 +134,7 @@ public class Chat(
     val bitmaps = LinkedList<Bitmap>()
     val inlineDataParts = LinkedList<InlineDataPart>()
     val text = StringBuilder()
+    val parts = mutableListOf<Part>()
 
     /**
      * TODO: revisit when images and inline data are returned. This will cause issues with how
@@ -147,22 +149,17 @@ public class Chat(
             is ImagePart -> bitmaps.add(part.image)
             is InlineDataPart -> inlineDataParts.add(part)
           }
+          parts.add(part)
         }
       }
       .onCompletion {
         lock.release()
         if (it == null) {
           val content =
             content("model") {
-              for (bitmap in bitmaps) {
-                image(bitmap)
-              }
-              for (inlineDataPart in inlineDataParts) {
-                inlineData(inlineDataPart.inlineData, inlineDataPart.mimeType)
-              }
-              if (text.isNotBlank()) {
-                text(text.toString())
-              }
+              setParts(
+                parts.filterNot { part -> part is TextPart && !part.hasContent() }.toMutableList()
+              )
             }
 
           history.add(prompt)
@@ -224,3 +221,12 @@ public class Chat(
     }
   }
 }
+
+/**
+ * Returns true if the [TextPart] contains any content, either in its [TextPart.text] property or
+ * its [TextPart.thoughtSignature] property.
+ */
+private fun TextPart.hasContent(): Boolean {
+  if (text.isNotEmpty()) return true
+  return !thoughtSignature.isNullOrBlank()
+}
diff --git a/firebase-ai/src/test/java/com/google/firebase/ai/DevAPIStreamingSnapshotTests.kt b/firebase-ai/src/test/java/com/google/firebase/ai/DevAPIStreamingSnapshotTests.kt
@@ -18,18 +18,29 @@ package com.google.firebase.ai
 
 import com.google.firebase.ai.type.BlockReason
 import com.google.firebase.ai.type.FinishReason
+import com.google.firebase.ai.type.FunctionCallPart
 import com.google.firebase.ai.type.PromptBlockedException
 import com.google.firebase.ai.type.ResponseStoppedException
 import com.google.firebase.ai.type.ServerException
+import com.google.firebase.ai.type.content
 import com.google.firebase.ai.util.goldenDevAPIStreamingFile
 import io.kotest.assertions.throwables.shouldThrow
 import io.kotest.matchers.collections.shouldBeEmpty
+import io.kotest.matchers.collections.shouldNotBeEmpty
+import io.kotest.matchers.nulls.shouldNotBeNull
 import io.kotest.matchers.shouldBe
+import io.kotest.matchers.string.shouldStartWith
+import io.ktor.client.engine.mock.toByteArray
+import io.ktor.client.request.HttpRequestData
 import io.ktor.http.HttpStatusCode
 import kotlin.time.Duration.Companion.seconds
 import kotlinx.coroutines.flow.collect
 import kotlinx.coroutines.flow.toList
 import kotlinx.coroutines.withTimeout
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.jsonArray
+import kotlinx.serialization.json.jsonObject
+import kotlinx.serialization.json.jsonPrimitive
 import org.junit.Test
 import org.junit.runner.RunWith
 import org.robolectric.RobolectricTestRunner
@@ -85,6 +96,86 @@ internal class DevAPIStreamingSnapshotTests {
       }
     }
 
+  @Test
+  fun `success call with thought summary and signature`() =
+    goldenDevAPIStreamingFile(
+      "streaming-success-thinking-function-call-thought-summary-signature.txt"
+    ) {
+      val responses = model.generateContentStream("prompt")
+
+      withTimeout(testTimeout) {
+        val responseList = responses.toList()
+        responseList.isEmpty() shouldBe false
+        val functionCallResponse = responseList.find { it.functionCalls.isNotEmpty() }
+        functionCallResponse.shouldNotBeNull()
+        functionCallResponse.functionCalls.first().let {
+          it.thoughtSignature.shouldNotBeNull()
+          it.thoughtSignature.shouldStartWith("CiIBVKhc7vB")
+        }
+      }
+    }
+
+  @Test
+  fun `chat call with history including thought summary and signature`() {
+    var capturedRequest: HttpRequestData? = null
+    goldenDevAPIStreamingFile(
+      "streaming-success-thinking-function-call-thought-summary-signature.txt",
+      requestHandler = { capturedRequest = it }
+    ) {
+      val chat = model.startChat()
+      val firstPrompt = content { text("first prompt") }
+      val secondPrompt = content { text("second prompt") }
+      val responses = chat.sendMessageStream(firstPrompt)
+
+      withTimeout(testTimeout) {
+        val responseList = responses.toList()
+        responseList.shouldNotBeEmpty()
+
+        chat.history.let { history ->
+          history.contains(firstPrompt)
+          val functionCallPart =
+            history.flatMap { it.parts }.first { it is FunctionCallPart } as FunctionCallPart
+          functionCallPart.let {
+            it.thoughtSignature.shouldNotBeNull()
+            it.thoughtSignature.shouldStartWith("CiIBVKhc7vB")
+          }
+        }
+
+        // Reset the request so we can be sure we capture the latest version
+        capturedRequest = null
+
+        // We don't care about the response, only the request
+        val unused = chat.sendMessageStream(secondPrompt).toList()
+
+        // Make sure the history contains all prompts seen so far
+        chat.history.contains(firstPrompt)
+        chat.history.contains(secondPrompt)
+
+        // Put the captured request into a `val` to enable smart casting
+        val request = capturedRequest
+        request.shouldNotBeNull()
+        val bodyAsString = request.body.toByteArray().decodeToString()
+        bodyAsString.shouldNotBeNull()
+
+        val rootElement = Json.parseToJsonElement(bodyAsString).jsonObject
+
+        // Traverse the tree: contents -> parts -> thoughtSignature
+        val contents = rootElement["contents"]?.jsonArray
+
+        val signature =
+          contents?.firstNotNullOfOrNull { content ->
+            content.jsonObject["parts"]?.jsonArray?.firstNotNullOfOrNull { part ->
+              // resulting value is a JsonPrimitive, so we use .content to get the string
+              part.jsonObject["thoughtSignature"]?.jsonPrimitive?.content
+            }
+          }
+
+        signature.shouldNotBeNull()
+        signature.shouldStartWith("CiIBVKhc7vB")
+      }
+    }
+  }
+
   @Test
   fun `prompt blocked for safety`() =
     goldenDevAPIStreamingFile("streaming-failure-prompt-blocked-safety.txt") {
diff --git a/firebase-ai/src/test/java/com/google/firebase/ai/util/tests.kt b/firebase-ai/src/test/java/com/google/firebase/ai/util/tests.kt
@@ -29,11 +29,11 @@ import io.kotest.matchers.collections.shouldNotBeEmpty
 import io.kotest.matchers.nulls.shouldNotBeNull
 import io.ktor.client.engine.mock.MockEngine
 import io.ktor.client.engine.mock.respond
+import io.ktor.client.request.HttpRequestData
 import io.ktor.http.HttpHeaders
 import io.ktor.http.HttpStatusCode
 import io.ktor.http.headersOf
 import io.ktor.utils.io.ByteChannel
-import io.ktor.utils.io.close
 import io.ktor.utils.io.writeFully
 import java.io.File
 import kotlinx.coroutines.launch
@@ -103,6 +103,7 @@ internal fun commonTest(
   status: HttpStatusCode = HttpStatusCode.OK,
   requestOptions: RequestOptions = RequestOptions(),
   backend: GenerativeBackend = GenerativeBackend.vertexAI(),
+  requestHandler: (HttpRequestData) -> Unit = {},
   block: CommonTest,
 ) = doBlocking {
   val channel = ByteChannel(autoFlush = true)
@@ -115,6 +116,7 @@ internal fun commonTest(
       "gemini-pro",
       requestOptions,
       MockEngine {
+        requestHandler(it)
         respond(channel, status, headersOf(HttpHeaders.ContentType, "application/json"))
       },
       TEST_CLIENT_ID,
@@ -144,12 +146,13 @@ internal fun goldenStreamingFile(
   name: String,
   httpStatusCode: HttpStatusCode = HttpStatusCode.OK,
   backend: GenerativeBackend = GenerativeBackend.vertexAI(),
+  requestHandler: (HttpRequestData) -> Unit,
   block: CommonTest,
 ) = doBlocking {
   val goldenFile = loadGoldenFile(name)
   val messages = goldenFile.readLines().filter { it.isNotBlank() }
 
-  commonTest(httpStatusCode, backend = backend) {
+  commonTest(httpStatusCode, backend = backend, requestHandler = requestHandler) {
     launch {
       for (message in messages) {
         channel.writeFully("$message$SSE_SEPARATOR".toByteArray())
@@ -175,8 +178,15 @@ internal fun goldenStreamingFile(
 internal fun goldenVertexStreamingFile(
   name: String,
   httpStatusCode: HttpStatusCode = HttpStatusCode.OK,
+  requestHandler: (HttpRequestData) -> Unit = {},
   block: CommonTest,
-) = goldenStreamingFile("vertexai/$name", httpStatusCode, block = block)
+) =
+  goldenStreamingFile(
+    "vertexai/$name",
+    httpStatusCode,
+    requestHandler = requestHandler,
+    block = block
+  )
 
 /**
  * A variant of [goldenStreamingFile] for testing the developer api
@@ -192,8 +202,16 @@ internal fun goldenVertexStreamingFile(
 internal fun goldenDevAPIStreamingFile(
   name: String,
   httpStatusCode: HttpStatusCode = HttpStatusCode.OK,
+  requestHandler: (HttpRequestData) -> Unit = {},
   block: CommonTest,
-) = goldenStreamingFile("googleai/$name", httpStatusCode, GenerativeBackend.googleAI(), block)
+) =
+  goldenStreamingFile(
+    "googleai/$name",
+    httpStatusCode,
+    GenerativeBackend.googleAI(),
+    requestHandler,
+    block
+  )
 
 /**
  * A variant of [commonTest] for performing snapshot tests.
