🎙️ Voice Agents - Complete Implementation Guide

🎉 Current Status: Voice System with Clean State Machine ✅

✅ What's Working Now

Clean State Machine - NEW: Eliminates race conditions with single source of truth
Hybrid Voice Mode - NEW: Voice input works with ANY model (preserves user selection)
Push-to-talk voice input - Tap microphone to record
Real-time transcription - Speech converted to text via OpenAI
Agent interaction - Agents receive and respond to voice input
Visual feedback - Enhanced recording states with proper state machine
Model preservation - NEW: No forced switching to expensive realtime models
Voice responses - Nova speaks responses with smart truncation
Smart audio truncation - Length-aware responses (75 words max spoken)
Response cancellation - Stop Nova mid-speech functionality
Audio playback system - PCM16 streaming with queue management
Enhanced debugging - NEW: VoiceDebugPanelV2 with state machine diagnostics
Interrupt capability - NEW: Interrupt AI speech to respond immediately

🧪 Ready for Testing

Full bidirectional voice - Complete voice input → voice output flow
Content-aware speaking - Different strategies for code, lists, and text
Audio controls - Volume, pause, resume, stop functionality

🎯 Immediate Priorities

1. Production Voice Testing

Voice implementation is complete and ready for full testing:

# Complete Test Checklist:
Click mic → Green connected state (not spinning)
Say "Hello Nova, tell me a joke"
Nova should SPEAK her response immediately
Test truncation: Ask for long explanations
Test code requests: "Write a Python function"
Test lists: "Give me 10 productivity tips"
Test cancellation: Stop Nova mid-speech

2. Hybrid Voice Mode ✅ IMPLEMENTED

Previous: Forced switch to expensive realtime model for ANY voice use
Current: ✅ Voice input on ANY model with smart voice output

// NEW: Hybrid Mode Implementation
<VoiceRecordButtonHybrid
  model={userSelectedModel}  // Preserves user choice!
  enableHybridMode={true}    // NEW: Smart voice handling
  onTranscript={(text) => {
    // Transcription sent to user's chosen model
    // No forced model switching
  }}
/>

// NEW: Smart Voice System
const hybridVoice = useHybridVoice({
  currentModel: userSelectedModel,
  config: {
    preserveCurrentModel: true,  // KEY: No automatic switching
    inputMode: 'whisper',        // Cheaper for transcription
    outputMode: 'tts',           // Smart voice responses
  }
});

Status: ✅ COMPLETED - Voice works with any model!

3. Smart Silence Detection

2-4 second silence threshold
Visual countdown indicator
Configurable per user preference
"Still listening..." for long pauses

🏗️ Architecture Overview

Voice Infrastructure Layers ✅ UPDATED

graph TD
    A[Voice UI Layer] --> B[State Machine Layer] 
    B --> C[Audio Processing]
    C --> D[WebSocket Layer]
    D --> E[Backend Handlers]
    E --> F[OpenAI Realtime API]
    
    A1[VoiceRecordButtonHybrid] --> A
    A2[VoiceDebugPanelV2] --> A
    A3[VoiceStateMachineTest] --> A
    
    B1[useVoiceV2 Hook] --> B
    B2[useVoiceStateMachine] --> B
    B3[VoiceState Enum] --> B
    B4[Transition Validation] --> B
    
    C1[audioEncoder.ts] --> C
    C2[audioDecoder.ts] --> C
    C3[AudioStreamProcessor] --> C
    
    D1[Voice Actions] --> D
    D2[Session Management] --> D
    D3[WebSocket Handlers] --> D
    
    E1[voice.session.start] --> E
    E2[voice.audio.chunk] --> E
    E3[voice.text.input] --> E
    E4[voice.response.cancel] --> E
    
    F1[Speech-to-Text] --> F
    F2[Text-to-Speech] --> F

NEW: State Machine Architecture ✅

The core improvement is a clean state machine that eliminates race conditions:

// OLD: Problematic dual-state approach
const [isRecording, setIsRecording] = useState(false);  // Source 1
const [isSpeaking, setIsSpeaking] = useState(false);    // Source 2  
const [state, setState] = useState(VoiceSessionState.IDLE); // Source 3
// Could become inconsistent: state=CONNECTED, isRecording=true, isSpeaking=true 😱

// NEW: Single source of truth
enum VoiceState {
  IDLE = 'idle',           // No session, ready to start
  CONNECTING = 'connecting', // Establishing session  
  READY = 'ready',         // Session active, ready for interaction
  LISTENING = 'listening',  // Recording user audio
  PROCESSING = 'processing', // Processing user input
  SPEAKING = 'speaking',   // AI is speaking
  DISCONNECTING = 'disconnecting', // Ending session
  ERROR = 'error',         // Error state
}

// UI state derived from main state - always consistent! ✅
const isRecording = state === VoiceState.LISTENING;
const isSpeaking = state === VoiceState.SPEAKING;
const canRecord = state === VoiceState.READY || state === VoiceState.SPEAKING;
const canInterrupt = state === VoiceState.SPEAKING;

Backend Voice Handlers

Handler	Purpose	Timeout	Status
`voice.session.start`	Initialize OpenAI connection	30s	✅ Production Ready
`voice.session.end`	Cleanup connection	30s	✅ Production Ready
`voice.audio.chunk`	Stream audio data	30s	✅ Production Ready
`voice.audio.commit`	Commit audio buffer	30s	✅ Production Ready
`voice.config.update`	Update session config	30s	✅ Production Ready
`voice.text.input`	Send text for voice response	30s	✅ Production Ready
`voice.response.cancel`	Stop audio playback	30s	✅ Production Ready

Frontend Components

Component	Purpose	Location	Status
`VoiceRecordButtonRealtime`	Main voice UI with all states	`/components/common/`	✅ Production Ready
`useVoice`	Complete voice state management	`/hooks/`	✅ Production Ready
`audioEncoder.ts`	Float32 → PCM16 conversion	`/utils/audio/`	✅ Production Ready
`audioDecoder.ts`	PCM16 → Audio playback	`/utils/audio/`	✅ Production Ready
`AudioStreamProcessor`	Real-time audio capture	`/utils/audio/`	✅ Production Ready
`AudioStreamPlayer`	Queue-based audio playback	`/utils/audio/`	✅ Production Ready

🎯 Voice UX Patterns

Current: Push-to-Talk

[Tap] → [Recording...] → [Tap] → [Processing...] → [Response]

Future: Smart Detection

[Tap] → [Recording...] → [2s silence] → [Auto-stop] → [Response]
         ↳ [Visual countdown during silence]

Future: Wake Word

"Hey Nova" → [Listening...] → [Auto-detect end] → [Response]

🔊 Voice Response Intelligence

Smart Truncation Rules

function getVoiceResponseStrategy(text: string, context: Context) {
  const wordCount = text.split(' ').length;
  
  // Short responses: Speak everything
  if (wordCount < 100) {
    return { speak: text, display: text };
  }
  
  // Medium responses: Speak intro
  if (wordCount < 500) {
    const intro = text.split('.').slice(0, 3).join('.'); 
    return { 
      speak: intro + "... I've written more details below.",
      display: text 
    };
  }
  
  // Long responses: Summary only
  const summary = generateSummary(text, 75); // 75 words max
  return {
    speak: summary + " Check the full response below.",
    display: text
  };
}

Context-Aware Speaking

Context	Behavior
Driving Mode	Always speak full responses, auto-continue
Headphones	Longer responses OK, user can control
Speaker	Brief responses, respect surroundings
Silent Mode	Text only, no audio
Code/Lists	"I've written code for you" + text display

🐛 Known Issues & Edge Cases

The Silence Detection Challenge

Too aggressive: Cuts off thoughtful pauses → Frustration
Too passive: User has to manually stop → Tedious
Solution: Adaptive threshold based on speaking patterns

The Model Switching Problem

Current: Forces expensive GPT-4O Realtime for ANY voice
Impact: 10x cost increase even for simple transcription
Solution: Hybrid mode with smart model selection

The Interruption Problem

Scenario: User wants to correct mid-sentence
Current: Must wait for processing
Solution: Cancel button during recording

📊 Implementation Roadmap

✅ Phase 1: Foundation (COMPLETE)

✅ Phase 2: Voice Responses (COMPLETE)

Response infrastructure built
Audio playback with Nova implemented
Smart truncation verified and working
Response cancellation implemented
Full bidirectional voice communication

📅 Phase 3: Hybrid Mode (THIS WEEK)

Implement Whisper fallback for non-realtime models
Smart model switching only for responses
Cost optimization logic
User preference system

🔮 Phase 4: Advanced Features (NEXT SPRINT)

🎬 Testing Scenarios

Scenario 1: Basic Voice Chat

User: "Hey Nova, what's the weather like?"
Nova: [SPEAKS] "I don't have access to real-time weather data, but I'd be happy to help you with other questions!"

Scenario 2: Long Response Truncation

User: "Explain quantum computing"
Nova: [SPEAKS] "Quantum computing uses quantum bits or 'qubits' that can exist in multiple states simultaneously... I've written a detailed explanation below."
[DISPLAYS] [Full 500+ word explanation]

Scenario 3: Code Request

User: "Write a Python function to sort a list"
Nova: [SPEAKS] "I've written a Python sorting function for you to review."
[DISPLAYS] [Complete code with syntax highlighting]

🚨 Emergency Procedures

If Voice Goes Haywire

Global Kill Switch: Admin panel → Disable voice features
Per-User Toggle: Settings → Voice → Disabled
Model Fallback: Force text-only mode
Credit Circuit Breaker: Auto-stop if burning credits

Monitoring Commands

# Check voice session count
aws logs tail /aws/lambda/voice-session-start --follow

# Monitor credit burn
aws cloudwatch get-metric-statistics \
  --namespace "Bike4Mind" \
  --metric-name "VoiceCreditsPerMinute"

# Emergency stop all voice
aws ssm put-parameter \
  --name "/sst/app/VoiceEnabled" \
  --value "false"

🎯 Success Metrics

Current Achievement

✅ Voice input accuracy: >95%
✅ User can talk to Nova
✅ Real-time transcription working
✅ Voice response: Fully implemented
✅ Smart truncation: Content-aware strategies
✅ Audio controls: Volume, pause, resume, stop
✅ Bidirectional communication: Complete flow

Target Metrics (Ready for Measurement)

Voice response satisfaction: >4.5/5
Silence detection accuracy: >90%
Response truncation relevance: >85%
Credit efficiency: <2x text-only cost

🔗 Technical References

Key Files

Backend: server/websocket/voice/*.ts
Frontend: hooks/useVoice.ts, components/common/VoiceRecordButtonRealtime.tsx
Types: types/voice.ts
Audio: utils/audio/audioEncoder.ts, utils/audio/audioDecoder.ts

Environment Variables

OPENAI_API_KEY=<required for realtime>
VOICE_SESSION_TIMEOUT=60
VOICE_MAX_DURATION=300
VOICE_MODEL=gpt-4o-realtime-preview-2024-12-17

Last Updated: June 2025
Status: Voice Input ✅ | Voice Output ✅ | Hybrid Mode 📅

🎉 Current Status: Voice System with Clean State Machine ✅​

✅ What's Working Now​

🧪 Ready for Testing​

🎯 Immediate Priorities​

1. Production Voice Testing​

2. Hybrid Voice Mode ✅ IMPLEMENTED​

3. Smart Silence Detection​

🏗️ Architecture Overview​

Voice Infrastructure Layers ✅ UPDATED​

NEW: State Machine Architecture ✅​

Backend Voice Handlers​

Frontend Components​

🎯 Voice UX Patterns​

Current: Push-to-Talk​

Future: Smart Detection​

Future: Wake Word​

🔊 Voice Response Intelligence​

Smart Truncation Rules​

Context-Aware Speaking​

🐛 Known Issues & Edge Cases​

The Silence Detection Challenge​

The Model Switching Problem​

The Interruption Problem​

📊 Implementation Roadmap​

✅ Phase 1: Foundation (COMPLETE)​

✅ Phase 2: Voice Responses (COMPLETE)​

📅 Phase 3: Hybrid Mode (THIS WEEK)​

🔮 Phase 4: Advanced Features (NEXT SPRINT)​

🎬 Testing Scenarios​

Scenario 1: Basic Voice Chat​

Scenario 2: Long Response Truncation​

Scenario 3: Code Request​

🚨 Emergency Procedures​

If Voice Goes Haywire​

Monitoring Commands​

🎯 Success Metrics​

Current Achievement​

Target Metrics (Ready for Measurement)​

🔗 Technical References​

Key Files​

Environment Variables​