feat(firebaseai): deprecate totalBillableCharacters

packages/firebase_ai/firebase_ai/example/lib/pages/token_count_page.dart

@@ -87,8 +87,7 @@ class _TokenCountPageState extends State<TokenCountPage> {
     const prompt = 'tell a short story';
     final content = Content.text(prompt);
     final tokenResponse = await widget.model.countTokens([content]);
-    final tokenResult = 'Count token: ${tokenResponse.totalTokens}, billable '
-        'characters: ${tokenResponse.totalBillableCharacters}';
+    final tokenResult = 'Count token: ${tokenResponse.totalTokens}';
     _messages.add(MessageData(text: tokenResult, fromUser: false));
 
     final contentResponse = await widget.model.generateContent([content]);

packages/firebase_ai/firebase_ai/lib/src/api.dart

@@ -31,6 +31,9 @@ final class CountTokensResponse {
   /// The number of characters that the `model` could bill at.
   ///
   /// Always non-negative.
+  @Deprecated(
+    'Use `totalTokens` instead; Gemini 2.0 series models and newer are always billed by token count.',
+  )
   final int? totalBillableCharacters;
 
   /// List of modalities that were processed in the request input.

packages/firebase_ai/firebase_ai/test/api_test.dart

@@ -25,17 +25,14 @@ void main() {
   group('CountTokensResponse', () {
     test('constructor initializes fields correctly', () {
       final details = [ModalityTokenCount(ContentModality.text, 10)];
-      final response = CountTokensResponse(100,
-          totalBillableCharacters: 50, promptTokensDetails: details);
+      final response = CountTokensResponse(100, promptTokensDetails: details);
       expect(response.totalTokens, 100);
-      expect(response.totalBillableCharacters, 50);
       expect(response.promptTokensDetails, same(details));
     });
 
     test('constructor with null optional fields', () {
       final response = CountTokensResponse(100);
       expect(response.totalTokens, 100);
-      expect(response.totalBillableCharacters, isNull);
       expect(response.promptTokensDetails, isNull);
     });
   });
@@ -445,7 +442,6 @@ void main() {
       test('parses valid full JSON correctly', () {
         final json = {
           'totalTokens': 120,
-          'totalBillableCharacters': 240,
           'promptTokensDetails': [
             {
               'modality': 'TEXT',
@@ -455,7 +451,6 @@ void main() {
         };
         final response = VertexSerialization().parseCountTokensResponse(json);
         expect(response.totalTokens, 120);
-        expect(response.totalBillableCharacters, 240);
         expect(response.promptTokensDetails, isNotNull);
         expect(response.promptTokensDetails, hasLength(2));
         expect(response.promptTokensDetails![0].modality, ContentModality.text);
@@ -469,7 +464,6 @@ void main() {
         final json = {'totalTokens': 50};
         final response = VertexSerialization().parseCountTokensResponse(json);
         expect(response.totalTokens, 50);
-        expect(response.totalBillableCharacters, isNull);
         expect(response.promptTokensDetails, isNull);
       });
 

packages/firebase_vertexai/firebase_vertexai/example/lib/pages/token_count_page.dart

@@ -87,8 +87,7 @@ class _TokenCountPageState extends State<TokenCountPage> {
     const prompt = 'tell a short story';
     final content = Content.text(prompt);
     final tokenResponse = await widget.model.countTokens([content]);
-    final tokenResult = 'Count token: ${tokenResponse.totalTokens}, billable '
-        'characters: ${tokenResponse.totalBillableCharacters}';
+    final tokenResult = 'Count token: ${tokenResponse.totalTokens}';
     _messages.add(MessageData(text: tokenResult, fromUser: false));
 
     final contentResponse = await widget.model.generateContent([content]);

packages/firebase_vertexai/firebase_vertexai/test/api_test.dart

@@ -25,17 +25,14 @@ void main() {
   group('CountTokensResponse', () {
     test('constructor initializes fields correctly', () {
       final details = [ModalityTokenCount(ContentModality.text, 10)];
-      final response = CountTokensResponse(100,
-          totalBillableCharacters: 50, promptTokensDetails: details);
+      final response = CountTokensResponse(100, promptTokensDetails: details);
       expect(response.totalTokens, 100);
-      expect(response.totalBillableCharacters, 50);
       expect(response.promptTokensDetails, same(details));
     });
 
     test('constructor with null optional fields', () {
       final response = CountTokensResponse(100);
       expect(response.totalTokens, 100);
-      expect(response.totalBillableCharacters, isNull);
       expect(response.promptTokensDetails, isNull);
     });
   });
@@ -445,7 +442,6 @@ void main() {
       test('parses valid full JSON correctly', () {
         final json = {
           'totalTokens': 120,
-          'totalBillableCharacters': 240,
           'promptTokensDetails': [
             {
               'modality': 'TEXT',
@@ -455,7 +451,6 @@ void main() {
         };
         final response = VertexSerialization().parseCountTokensResponse(json);
         expect(response.totalTokens, 120);
-        expect(response.totalBillableCharacters, 240);
         expect(response.promptTokensDetails, isNotNull);
         expect(response.promptTokensDetails, hasLength(2));
         expect(response.promptTokensDetails![0].modality, ContentModality.text);
@@ -469,7 +464,6 @@ void main() {
         final json = {'totalTokens': 50};
         final response = VertexSerialization().parseCountTokensResponse(json);
         expect(response.totalTokens, 50);
-        expect(response.totalBillableCharacters, isNull);
         expect(response.promptTokensDetails, isNull);
       });