feat: capture audio tokens usage metadata in live models

core/src/main/java/com/google/adk/models/GeminiLlmConnection.java

@@ -127,6 +127,7 @@ private void handleServerMessage(LiveServerMessage message) {
   /** Converts a server message into the standardized LlmResponse format. */
   static Optional<LlmResponse> convertToServerResponse(LiveServerMessage message) {
     LlmResponse.Builder builder = LlmResponse.builder();
+    boolean hasRelevantData = false;
 
     if (message.serverContent().isPresent()) {
       LiveServerContent serverContent = message.serverContent().get();
@@ -140,6 +141,7 @@ static Optional<LlmResponse> convertToServerResponse(LiveServerMessage message)
       // overwrite the audio modelTurn content.
       serverContent.outputTranscription().ifPresent(builder::outputTranscription);
       serverContent.inputTranscription().ifPresent(builder::inputTranscription);
+      hasRelevantData = true;
     } else if (message.toolCall().isPresent()) {
       LiveServerToolCall toolCall = message.toolCall().get();
       toolCall
@@ -154,24 +156,37 @@ static Optional<LlmResponse> convertToServerResponse(LiveServerMessage message)
                 }
               });
       builder.partial(false).turnComplete(false);
-    } else if (message.usageMetadata().isPresent()) {
-      logger.debug("Received usage metadata: {}", message.usageMetadata().get());
-      return Optional.empty();
+      hasRelevantData = true;
     } else if (message.toolCallCancellation().isPresent()) {
       logger.debug("Received tool call cancellation: {}", message.toolCallCancellation().get());
       builder.interrupted(true).turnComplete(true);
-      return Optional.of(builder.build());
+      hasRelevantData = true;
     } else if (message.setupComplete().isPresent()) {
       logger.debug("Received setup complete.");
       return Optional.empty();
-    } else {
+    } else if (message.usageMetadata().isEmpty()) {
       logger.warn("Received unknown or empty server message: {}", message.toJson());
       builder
           .errorCode(new FinishReason("Unknown server message."))
           .errorMessage("Received unknown server message.");
+      hasRelevantData = true;
+    }
+
+    if (message.usageMetadata().isPresent()) {
+      logger.debug("Received usage metadata: {}", message.usageMetadata().get());
+      builder.usageMetadata(
+          GeminiUtil.toGenerateContentResponseUsageMetadata(message.usageMetadata().get()));
+      if (!hasRelevantData) {
+        builder.partial(false).turnComplete(false);
+      }
+      hasRelevantData = true;
+    }
+
+    if (hasRelevantData) {
+      return Optional.of(builder.build());
     }
 
-    return Optional.of(builder.build());
+    return Optional.empty();
   }
 
   /** Handles errors that occur *during* the initial connection attempt. */

core/src/main/java/com/google/adk/models/azure/AzureRealtimeLlmConnection.java

@@ -7,6 +7,8 @@
 import com.google.genai.types.Blob;
 import com.google.genai.types.Content;
 import com.google.genai.types.FunctionCall;
+import com.google.genai.types.GenerateContentResponseUsageMetadata;
+import com.google.genai.types.ModalityTokenCount;
 import com.google.genai.types.Part;
 import com.google.genai.types.Transcription;
 import io.reactivex.rxjava3.core.Completable;
@@ -548,6 +550,33 @@ private void handleResponseDone(JSONObject event) {
             "Realtime token usage — input: {}, output: {}",
             usage.optInt("input_tokens", 0),
             usage.optInt("output_tokens", 0));
+
+        GenerateContentResponseUsageMetadata.Builder usageBuilder =
+            GenerateContentResponseUsageMetadata.builder()
+                .promptTokenCount(usage.optInt("input_tokens", 0))
+                .candidatesTokenCount(usage.optInt("output_tokens", 0))
+                .totalTokenCount(usage.optInt("total_tokens", 0));
+
+        JSONObject inputDetails = usage.optJSONObject("input_token_details");
+        if (inputDetails != null && inputDetails.has("audio_tokens")) {
+          usageBuilder.promptTokensDetails(
+              ImmutableList.of(
+                  ModalityTokenCount.builder()
+                      .modality(com.google.genai.types.MediaModality.Known.AUDIO)
+                      .tokenCount(inputDetails.optInt("audio_tokens", 0))
+                      .build()));
+        }
+
+        JSONObject outputDetails = usage.optJSONObject("output_token_details");
+        if (outputDetails != null && outputDetails.has("audio_tokens")) {
+          usageBuilder.candidatesTokensDetails(
+              ImmutableList.of(
+                  ModalityTokenCount.builder()
+                      .modality(com.google.genai.types.MediaModality.Known.AUDIO)
+                      .tokenCount(outputDetails.optInt("audio_tokens", 0))
+                      .build()));
+        }
+        responseProcessor.onNext(LlmResponse.builder().usageMetadata(usageBuilder.build()).build());
       }
     }
   }

core/src/test/java/com/google/adk/models/GeminiLlmConnectionTest.java

@@ -152,13 +152,15 @@ public void convertToServerResponse_withToolCall_mapsContentWithFunctionCall() {
   }
 
   @Test
-  public void convertToServerResponse_withUsageMetadata_returnsEmpty() {
-    LiveServerMessage message =
-        LiveServerMessage.builder().usageMetadata(UsageMetadata.builder().build()).build();
+  public void convertToServerResponse_withUsageMetadata_returnsResponseWithUsage() {
+    UsageMetadata usageMetadata = UsageMetadata.builder().promptTokenCount(10).build();
+    LiveServerMessage message = LiveServerMessage.builder().usageMetadata(usageMetadata).build();
 
     Optional<LlmResponse> result = GeminiLlmConnection.convertToServerResponse(message);
 
-    assertThat(result.isPresent()).isFalse();
+    assertThat(result.isPresent()).isTrue();
+    assertThat(result.get().usageMetadata()).isPresent();
+    assertThat(result.get().usageMetadata().get().promptTokenCount()).hasValue(10);
   }
 
   @Test