feat(firebaseai): live session resumption

[cynthiajoan]

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[cynthiajoan]

/gemini review

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Code Review

This pull request refactors the Gemini Live implementation to support session resumption and context window compression. It introduces a BidiMediaManager and BidiSessionController to better separate hardware management, business logic, and UI concerns. Key feedback includes addressing a potential runtime error on Flutter Web when decoding WebSocket messages, restoring echo cancellation to prevent audio feedback loops, and correcting several JSON keys to use snake_case to align with the Gemini Live API. Additionally, a typo in a tool response key was identified that could prevent correct model interaction.

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packages/firebase_ai/firebase_ai/lib/src/live_session.dart (144)

Calling utf8.decode(message) directly will cause a runtime error on Flutter Web because the message emitted by the WebSocketChannel is already a String on that platform. You should check the type of the message before decoding.

          final String jsonString = message is String ? message : utf8.decode(message as List<int>);

packages/firebase_ai/firebase_ai/example/lib/utils/audio_input.dart (113-114)

The removal of echoCancel and noiseSuppress from the RecordConfig is concerning for a bidirectional (Bidi) session. Without echo cancellation, the model's audio output played through the speakers will likely be picked up by the microphone and sent back to the model, creating a feedback loop or causing the model to 'hear' itself.

packages/firebase_ai/firebase_ai/lib/src/live_api.dart (558-561)

The keys used to parse the SessionResumptionUpdate message are in camelCase, but the Gemini Live API typically returns snake_case keys (e.g., new_handle, last_consumed_client_message_index). This will likely result in null values being parsed even when the data is present.

      newHandle: sessionResumptionUpdateJson['new_handle'] as String?,
      resumable: sessionResumptionUpdateJson['resumable'] as bool?,
      lastConsumedClientMessageIndex:
          sessionResumptionUpdateJson['last_consumed_client_message_index'] as int?,

packages/firebase_ai/firebase_ai/example/lib/pages/bidi_page.dart (511-512)

The key 'colorTemprature' contains a typo. While the comment mentions preserving the original typo, the tool definition at line 545 uses the correct spelling 'colorTemperature'. To ensure the model correctly interprets the tool response, the key must match the definition exactly.

          'colorTemperature': color,

packages/firebase_ai/firebase_ai/lib/src/live_api.dart (94)

The JSON key should use snake_case to align with the Gemini Live API naming conventions.

      {if (targetTokens case final targetTokens?) 'target_tokens': targetTokens};

packages/firebase_ai/firebase_ai/lib/src/live_api.dart (117-120)

The JSON keys should use snake_case to align with the Gemini Live API naming conventions.

        if (triggerTokens case final triggerTokens?)
          'trigger_tokens': triggerTokens,
        if (slidingWindow case final slidingWindow?)
          'sliding_window': slidingWindow.toJson()

packages/firebase_ai/firebase_ai/lib/src/live_session.dart (126)

The JSON key 'contextWindowCompression' should be 'context_window_compression' to maintain consistency with other snake_case keys in the setup message.

            'context_window_compression': contextWindowCompression.toJson()