add openai realtime streaming adapter with reconnection logic

internal/transcriber/adapter_openai_realtime.go

@@ -0,0 +1,535 @@
+package transcriber
+
+import (
+	"context"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"net/url"
+	"sync"
+	"time"
+
+	"github.com/gorilla/websocket"
+	"github.com/leonardotrapani/hyprvoice/internal/provider"
+)
+
+// OpenAIRealtimeAdapter implements StreamingAdapter for OpenAI Realtime API transcription
+type OpenAIRealtimeAdapter struct {
+	endpoint  *provider.EndpointConfig
+	apiKey    string
+	model     string
+	language  string
+	conn      *websocket.Conn
+	resultsCh chan TranscriptionResult
+	mu        sync.Mutex
+	ctx       context.Context
+	cancel    context.CancelFunc
+	wg        sync.WaitGroup
+	started   bool
+
+	// reconnection config
+	maxRetries  int
+	retryDelays []time.Duration
+
+	// track current item for transcription
+	currentItemID string
+}
+
+// OpenAI Realtime WebSocket message types (outgoing)
+type openaiRealtimeSessionUpdate struct {
+	Type    string                      `json:"type"`
+	Session openaiRealtimeSessionConfig `json:"session"`
+}
+
+type openaiRealtimeSessionConfig struct {
+	Modalities              []string                     `json:"modalities,omitempty"`
+	InputAudioFormat        string                       `json:"input_audio_format,omitempty"`
+	InputAudioTranscription *openaiRealtimeTranscription `json:"input_audio_transcription,omitempty"`
+	TurnDetection           *openaiRealtimeTurnDetection `json:"turn_detection,omitempty"`
+}
+
+type openaiRealtimeTranscription struct {
+	Model    string `json:"model,omitempty"`
+	Language string `json:"language,omitempty"`
+}
+
+type openaiRealtimeTurnDetection struct {
+	Type              string  `json:"type"`
+	Threshold         float64 `json:"threshold,omitempty"`
+	PrefixPaddingMs   int     `json:"prefix_padding_ms,omitempty"`
+	SilenceDurationMs int     `json:"silence_duration_ms,omitempty"`
+	CreateResponse    bool    `json:"create_response,omitempty"`
+}
+
+type openaiRealtimeInputAudioAppend struct {
+	Type  string `json:"type"`
+	Audio string `json:"audio"`
+}
+
+type openaiRealtimeInputAudioCommit struct {
+	Type string `json:"type"`
+}
+
+// OpenAI Realtime WebSocket response types (incoming)
+type openaiRealtimeServerEvent struct {
+	Type         string                     `json:"type"`
+	EventID      string                     `json:"event_id,omitempty"`
+	Session      *openaiRealtimeSessionInfo `json:"session,omitempty"`
+	Error        *openaiRealtimeError       `json:"error,omitempty"`
+	ItemID       string                     `json:"item_id,omitempty"`
+	ContentIndex int                        `json:"content_index,omitempty"`
+	Transcript   string                     `json:"transcript,omitempty"`
+	Delta        string                     `json:"delta,omitempty"`
+}
+
+type openaiRealtimeSessionInfo struct {
+	ID    string `json:"id"`
+	Model string `json:"model"`
+}
+
+type openaiRealtimeError struct {
+	Type    string `json:"type"`
+	Code    string `json:"code,omitempty"`
+	Message string `json:"message"`
+	Param   string `json:"param,omitempty"`
+}
+
+// NewOpenAIRealtimeAdapter creates a new streaming adapter for OpenAI Realtime API
+// endpoint: the WebSocket endpoint config (e.g., wss://api.openai.com, /v1/realtime)
+// apiKey: OpenAI API key
+// model: model ID (e.g., "gpt-4o-realtime-preview")
+// lang: canonical language code (will be used for transcription config)
+func NewOpenAIRealtimeAdapter(endpoint *provider.EndpointConfig, apiKey, model, lang string) *OpenAIRealtimeAdapter {
+	return &OpenAIRealtimeAdapter{
+		endpoint:    endpoint,
+		apiKey:      apiKey,
+		model:       model,
+		language:    lang,
+		resultsCh:   make(chan TranscriptionResult, 100),
+		maxRetries:  3,
+		retryDelays: defaultRetryDelays,
+	}
+}
+
+// Start initiates the WebSocket connection to OpenAI Realtime API
+func (a *OpenAIRealtimeAdapter) Start(ctx context.Context, lang string) error {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+
+	if a.started {
+		return fmt.Errorf("adapter already started")
+	}
+
+	// use lang param if provided, otherwise use constructor lang
+	if lang != "" {
+		a.language = lang
+	}
+
+	// create cancelable context
+	a.ctx, a.cancel = context.WithCancel(ctx)
+
+	// connect to WebSocket
+	if err := a.connectLocked(); err != nil {
+		return err
+	}
+	a.started = true
+
+	// start reader goroutine
+	a.wg.Add(1)
+	go a.readLoop()
+
+	log.Printf("openai-realtime: connected, model=%s, language=%s", a.model, a.language)
+	return nil
+}
+
+// connectLocked establishes WebSocket connection and configures session. Must be called with mu held.
+func (a *OpenAIRealtimeAdapter) connectLocked() error {
+	wsURL, err := a.buildURL()
+	if err != nil {
+		return fmt.Errorf("build websocket url: %w", err)
+	}
+
+	headers := http.Header{}
+	headers.Set("Authorization", "Bearer "+a.apiKey)
+	headers.Set("OpenAI-Beta", "realtime=v1")
+
+	log.Printf("openai-realtime: connecting to %s", wsURL)
+	conn, resp, err := websocket.DefaultDialer.DialContext(a.ctx, wsURL, headers)
+	if err != nil {
+		if resp != nil {
+			log.Printf("openai-realtime: dial failed with status %d", resp.StatusCode)
+		}
+		return fmt.Errorf("websocket dial: %w", err)
+	}
+	a.conn = conn
+
+	// configure session for transcription-only mode
+	if err := a.configureSession(); err != nil {
+		conn.Close()
+		a.conn = nil
+		return fmt.Errorf("configure session: %w", err)
+	}
+
+	return nil
+}
+
+// configureSession sends session.update to configure transcription mode
+func (a *OpenAIRealtimeAdapter) configureSession() error {
+	// configure for transcription-only mode
+	// use server VAD to automatically detect speech and commit audio
+	sessionUpdate := openaiRealtimeSessionUpdate{
+		Type: "session.update",
+		Session: openaiRealtimeSessionConfig{
+			Modalities:       []string{"text"}, // text only, no audio output
+			InputAudioFormat: "pcm16",          // we send 16-bit PCM
+			InputAudioTranscription: &openaiRealtimeTranscription{
+				Model: "gpt-4o-transcribe", // use gpt-4o for input transcription
+			},
+			TurnDetection: &openaiRealtimeTurnDetection{
+				Type:              "server_vad",
+				Threshold:         0.5,
+				PrefixPaddingMs:   300,
+				SilenceDurationMs: 500,
+				CreateResponse:    false, // we don't want responses, just transcription
+			},
+		},
+	}
+
+	// add language if specified
+	if a.language != "" {
+		sessionUpdate.Session.InputAudioTranscription.Language = a.language
+	}
+
+	return a.conn.WriteJSON(sessionUpdate)
+}
+
+// reconnect attempts to re-establish the WebSocket connection with exponential backoff.
+// Returns true if reconnection succeeded.
+func (a *OpenAIRealtimeAdapter) reconnect() bool {
+	for attempt := 0; attempt < a.maxRetries; attempt++ {
+		// check if context cancelled
+		select {
+		case <-a.ctx.Done():
+			return false
+		default:
+		}
+
+		// wait before retry (skip wait on first attempt)
+		if attempt > 0 {
+			delay := a.retryDelays[attempt-1]
+			if attempt-1 >= len(a.retryDelays) {
+				delay = a.retryDelays[len(a.retryDelays)-1]
+			}
+			log.Printf("openai-realtime: reconnect attempt %d/%d after %v", attempt+1, a.maxRetries, delay)
+
+			select {
+			case <-a.ctx.Done():
+				return false
+			case <-time.After(delay):
+			}
+		} else {
+			log.Printf("openai-realtime: reconnect attempt %d/%d", attempt+1, a.maxRetries)
+		}
+
+		a.mu.Lock()
+		// close old connection if exists
+		if a.conn != nil {
+			a.conn.Close()
+			a.conn = nil
+		}
+
+		err := a.connectLocked()
+		a.mu.Unlock()
+
+		if err == nil {
+			log.Printf("openai-realtime: reconnected successfully")
+			// notify caller of brief interruption
+			select {
+			case a.resultsCh <- TranscriptionResult{Error: fmt.Errorf("connection interrupted, reconnected"), IsFinal: false}:
+			default:
+			}
+			return true
+		}
+
+		log.Printf("openai-realtime: reconnect failed: %v", err)
+	}
+
+	return false
+}
+
+// buildURL constructs the WebSocket URL with query parameters
+func (a *OpenAIRealtimeAdapter) buildURL() (string, error) {
+	// parse base URL and path
+	baseURL := a.endpoint.BaseURL + a.endpoint.Path
+
+	u, err := url.Parse(baseURL)
+	if err != nil {
+		return "", fmt.Errorf("parse base url: %w", err)
+	}
+
+	// add model as query parameter
+	q := u.Query()
+	q.Set("model", a.model)
+	u.RawQuery = q.Encode()
+
+	return u.String(), nil
+}
+
+// readLoop reads messages from the WebSocket and sends results to the channel
+func (a *OpenAIRealtimeAdapter) readLoop() {
+	defer a.wg.Done()
+	defer close(a.resultsCh)
+
+	for {
+		select {
+		case <-a.ctx.Done():
+			return
+		default:
+		}
+
+		a.mu.Lock()
+		conn := a.conn
+		a.mu.Unlock()
+
+		if conn == nil {
+			// no connection, try to reconnect
+			if !a.reconnect() {
+				a.resultsCh <- TranscriptionResult{Error: fmt.Errorf("connection lost, reconnection failed after %d attempts", a.maxRetries)}
+				return
+			}
+			continue
+		}
+
+		_, message, err := conn.ReadMessage()
+		if err != nil {
+			// check if context was cancelled (normal shutdown)
+			select {
+			case <-a.ctx.Done():
+				return
+			default:
+			}
+
+			// attempt reconnection
+			log.Printf("openai-realtime: read error: %v, attempting reconnection", err)
+			if !a.reconnect() {
+				a.resultsCh <- TranscriptionResult{Error: fmt.Errorf("websocket read: %w, reconnection failed", err)}
+				return
+			}
+			continue
+		}
+
+		// parse message
+		var event openaiRealtimeServerEvent
+		if err := json.Unmarshal(message, &event); err != nil {
+			log.Printf("openai-realtime: parse error: %v", err)
+			continue
+		}
+
+		// handle different event types
+		a.handleEvent(event)
+	}
+}
+
+// handleEvent processes incoming server events
+func (a *OpenAIRealtimeAdapter) handleEvent(event openaiRealtimeServerEvent) {
+	switch event.Type {
+	case "session.created":
+		if event.Session != nil {
+			log.Printf("openai-realtime: session created, id=%s, model=%s", event.Session.ID, event.Session.Model)
+		}
+
+	case "session.updated":
+		log.Printf("openai-realtime: session updated")
+
+	case "error":
+		if event.Error != nil {
+			errMsg := event.Error.Message
+			if event.Error.Code != "" {
+				errMsg = fmt.Sprintf("%s: %s", event.Error.Code, errMsg)
+			}
+			log.Printf("openai-realtime: error: %s", errMsg)
+			a.resultsCh <- TranscriptionResult{Error: fmt.Errorf("openai: %s", errMsg)}
+		}
+
+	case "input_audio_buffer.speech_started":
+		log.Printf("openai-realtime: speech started")
+
+	case "input_audio_buffer.speech_stopped":
+		log.Printf("openai-realtime: speech stopped, item_id=%s", event.ItemID)
+		a.currentItemID = event.ItemID
+
+	case "input_audio_buffer.committed":
+		log.Printf("openai-realtime: audio committed, item_id=%s", event.ItemID)
+		a.currentItemID = event.ItemID
+
+	case "conversation.item.input_audio_transcription.delta":
+		// partial transcription result
+		if event.Delta != "" {
+			a.resultsCh <- TranscriptionResult{Text: event.Delta, IsFinal: false}
+		}
+
+	case "conversation.item.input_audio_transcription.completed":
+		// final transcription result
+		if event.Transcript != "" {
+			log.Printf("openai-realtime: transcription completed: %q", event.Transcript)
+			a.resultsCh <- TranscriptionResult{Text: event.Transcript, IsFinal: true}
+		}
+
+	case "conversation.item.input_audio_transcription.failed":
+		log.Printf("openai-realtime: transcription failed for item %s", event.ItemID)
+		if event.Error != nil {
+			a.resultsCh <- TranscriptionResult{Error: fmt.Errorf("transcription failed: %s", event.Error.Message)}
+		}
+
+	case "conversation.item.created", "conversation.item.added":
+		log.Printf("openai-realtime: conversation item created/added")
+
+	case "rate_limits.updated":
+		// ignore rate limit updates
+
+	default:
+		log.Printf("openai-realtime: unhandled event type: %s", event.Type)
+	}
+}
+
+// SendChunk sends audio data to the WebSocket
+// OpenAI Realtime API expects base64-encoded PCM16 audio at 24kHz
+// We receive 16kHz audio, so we need to resample
+func (a *OpenAIRealtimeAdapter) SendChunk(audio []byte) error {
+	a.mu.Lock()
+	if !a.started {
+		a.mu.Unlock()
+		return fmt.Errorf("adapter not started")
+	}
+	conn := a.conn
+	a.mu.Unlock()
+
+	// check context
+	select {
+	case <-a.ctx.Done():
+		return a.ctx.Err()
+	default:
+	}
+
+	if conn == nil {
+		return fmt.Errorf("no connection")
+	}
+
+	// resample from 16kHz to 24kHz (OpenAI expects 24kHz)
+	resampled := resample16to24(audio)
+
+	// encode audio as base64
+	audioB64 := base64.StdEncoding.EncodeToString(resampled)
+
+	// create message
+	msg := openaiRealtimeInputAudioAppend{
+		Type:  "input_audio_buffer.append",
+		Audio: audioB64,
+	}
+
+	// send as JSON
+	a.mu.Lock()
+	err := a.conn.WriteJSON(msg)
+	a.mu.Unlock()
+
+	if err != nil {
+		// attempt reconnection
+		log.Printf("openai-realtime: write error: %v, attempting reconnection", err)
+		if a.reconnect() {
+			// retry the chunk after reconnection
+			a.mu.Lock()
+			err = a.conn.WriteJSON(msg)
+			a.mu.Unlock()
+			if err == nil {
+				return nil
+			}
+		}
+		return fmt.Errorf("websocket write: %w", err)
+	}
+
+	return nil
+}
+
+// resample16to24 converts 16kHz PCM16 audio to 24kHz using linear interpolation
+// Input: 16-bit PCM samples at 16kHz
+// Output: 16-bit PCM samples at 24kHz
+func resample16to24(input []byte) []byte {
+	if len(input) < 2 {
+		return input
+	}
+
+	// input has 16kHz samples (2 bytes each)
+	// output needs 24kHz samples (ratio 24/16 = 1.5)
+	numInputSamples := len(input) / 2
+	numOutputSamples := (numInputSamples * 3) / 2
+
+	output := make([]byte, numOutputSamples*2)
+
+	for i := 0; i < numOutputSamples; i++ {
+		// calculate position in input
+		srcPos := float64(i) * 16.0 / 24.0
+		srcIdx := int(srcPos)
+		frac := srcPos - float64(srcIdx)
+
+		// get source samples
+		var sample1, sample2 int16
+		if srcIdx*2+1 < len(input) {
+			sample1 = int16(input[srcIdx*2]) | (int16(input[srcIdx*2+1]) << 8)
+		}
+		if (srcIdx+1)*2+1 < len(input) {
+			sample2 = int16(input[(srcIdx+1)*2]) | (int16(input[(srcIdx+1)*2+1]) << 8)
+		} else {
+			sample2 = sample1
+		}
+
+		// linear interpolation
+		outSample := int16(float64(sample1)*(1-frac) + float64(sample2)*frac)
+
+		// write output sample (little-endian)
+		output[i*2] = byte(outSample)
+		output[i*2+1] = byte(outSample >> 8)
+	}
+
+	return output
+}
+
+// Results returns the channel for receiving transcription results
+func (a *OpenAIRealtimeAdapter) Results() <-chan TranscriptionResult {
+	return a.resultsCh
+}
+
+// Close gracefully closes the WebSocket connection
+func (a *OpenAIRealtimeAdapter) Close() error {
+	a.mu.Lock()
+
+	if !a.started {
+		a.mu.Unlock()
+		return nil
+	}
+
+	// cancel context first to signal reader to stop
+	if a.cancel != nil {
+		a.cancel()
+	}
+
+	// get conn ref while holding lock
+	conn := a.conn
+
+	a.started = false
+	a.mu.Unlock()
+
+	// close websocket outside of lock (readLoop may be blocked on read)
+	if conn != nil {
+		// send close frame (best effort)
+		_ = conn.WriteMessage(websocket.CloseMessage, websocket.FormatCloseMessage(websocket.CloseNormalClosure, ""))
+		conn.Close()
+	}
+
+	// wait for reader to finish
+	a.wg.Wait()
+
+	log.Printf("openai-realtime: closed")
+	return nil
+}

internal/transcriber/adapter_openai_realtime_test.go

@@ -0,0 +1,544 @@
+package transcriber
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/gorilla/websocket"
+	"github.com/leonardotrapani/hyprvoice/internal/provider"
+)
+
+// mockOpenAIRealtimeServer creates a mock WebSocket server for OpenAI Realtime API
+func mockOpenAIRealtimeServer(t *testing.T, handler func(*websocket.Conn)) *httptest.Server {
+	upgrader := websocket.Upgrader{
+		CheckOrigin: func(r *http.Request) bool { return true },
+	}
+
+	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// verify auth header
+		auth := r.Header.Get("Authorization")
+		if !strings.HasPrefix(auth, "Bearer ") {
+			t.Errorf("expected Bearer auth header, got: %s", auth)
+			http.Error(w, "Unauthorized", http.StatusUnauthorized)
+			return
+		}
+
+		// verify model in query
+		model := r.URL.Query().Get("model")
+		if model == "" {
+			t.Error("expected model query parameter")
+		}
+
+		conn, err := upgrader.Upgrade(w, r, nil)
+		if err != nil {
+			t.Errorf("upgrade failed: %v", err)
+			return
+		}
+		defer conn.Close()
+
+		handler(conn)
+	}))
+}
+
+func TestOpenAIRealtimeAdapter_ImplementsInterface(t *testing.T) {
+	var _ StreamingAdapter = (*OpenAIRealtimeAdapter)(nil)
+}
+
+func TestOpenAIRealtimeAdapter_Start(t *testing.T) {
+	var mu sync.Mutex
+	sessionCreated := false
+	sessionUpdated := false
+
+	server := mockOpenAIRealtimeServer(t, func(conn *websocket.Conn) {
+		// send session.created event
+		sessionCreatedEvent := map[string]interface{}{
+			"type":     "session.created",
+			"event_id": "event_123",
+			"session": map[string]interface{}{
+				"id":    "sess_123",
+				"model": "gpt-4o-realtime-preview",
+			},
+		}
+		if err := conn.WriteJSON(sessionCreatedEvent); err != nil {
+			t.Errorf("write session.created: %v", err)
+		}
+		mu.Lock()
+		sessionCreated = true
+		mu.Unlock()
+
+		// read session.update from client
+		_, msg, err := conn.ReadMessage()
+		if err != nil {
+			return
+		}
+
+		var update map[string]interface{}
+		if err := json.Unmarshal(msg, &update); err != nil {
+			t.Errorf("unmarshal session.update: %v", err)
+			return
+		}
+
+		if update["type"] != "session.update" {
+			t.Errorf("expected session.update, got %s", update["type"])
+		}
+		mu.Lock()
+		sessionUpdated = true
+		mu.Unlock()
+
+		// send session.updated response
+		sessionUpdatedEvent := map[string]interface{}{
+			"type":     "session.updated",
+			"event_id": "event_124",
+		}
+		if err := conn.WriteJSON(sessionUpdatedEvent); err != nil {
+			t.Errorf("write session.updated: %v", err)
+		}
+
+		// keep connection open until client closes
+		for {
+			_, _, err := conn.ReadMessage()
+			if err != nil {
+				return
+			}
+		}
+	})
+	defer server.Close()
+
+	// extract host for endpoint
+	wsURL := "ws" + strings.TrimPrefix(server.URL, "http")
+
+	endpoint := &provider.EndpointConfig{
+		BaseURL: wsURL,
+		Path:    "",
+	}
+
+	adapter := NewOpenAIRealtimeAdapter(endpoint, "sk-test-key", "gpt-4o-realtime-preview", "en")
+
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+	defer cancel()
+
+	err := adapter.Start(ctx, "")
+	if err != nil {
+		t.Fatalf("Start failed: %v", err)
+	}
+	defer adapter.Close()
+
+	// give time for events to process
+	time.Sleep(100 * time.Millisecond)
+
+	mu.Lock()
+	created := sessionCreated
+	updated := sessionUpdated
+	mu.Unlock()
+
+	if !created {
+		t.Error("session.created was not sent")
+	}
+	if !updated {
+		t.Error("session.update was not received by server")
+	}
+}
+
+func TestOpenAIRealtimeAdapter_SendChunk(t *testing.T) {
+	var mu sync.Mutex
+	receivedAudio := false
+
+	server := mockOpenAIRealtimeServer(t, func(conn *websocket.Conn) {
+		// send session.created
+		sessionCreatedEvent := map[string]interface{}{
+			"type": "session.created",
+			"session": map[string]interface{}{
+				"id": "sess_123",
+			},
+		}
+		conn.WriteJSON(sessionCreatedEvent)
+
+		// read session.update
+		conn.ReadMessage()
+
+		// send session.updated
+		conn.WriteJSON(map[string]interface{}{"type": "session.updated"})
+
+		// read audio chunk
+		_, msg, err := conn.ReadMessage()
+		if err != nil {
+			return
+		}
+
+		var audioMsg map[string]interface{}
+		if err := json.Unmarshal(msg, &audioMsg); err != nil {
+			t.Errorf("unmarshal audio: %v", err)
+			return
+		}
+
+		if audioMsg["type"] == "input_audio_buffer.append" {
+			audio, ok := audioMsg["audio"].(string)
+			if ok && len(audio) > 0 {
+				mu.Lock()
+				receivedAudio = true
+				mu.Unlock()
+			}
+		}
+
+		// keep connection open
+		for {
+			_, _, err := conn.ReadMessage()
+			if err != nil {
+				return
+			}
+		}
+	})
+	defer server.Close()
+
+	wsURL := "ws" + strings.TrimPrefix(server.URL, "http")
+	endpoint := &provider.EndpointConfig{BaseURL: wsURL, Path: ""}
+	adapter := NewOpenAIRealtimeAdapter(endpoint, "sk-test", "gpt-4o-realtime-preview", "")
+
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+	defer cancel()
+
+	if err := adapter.Start(ctx, ""); err != nil {
+		t.Fatalf("Start failed: %v", err)
+	}
+	defer adapter.Close()
+
+	// give time for connection setup
+	time.Sleep(100 * time.Millisecond)
+
+	// send audio chunk (16kHz PCM16)
+	audio := make([]byte, 320) // 10ms of 16kHz audio
+	for i := range audio {
+		audio[i] = byte(i % 256)
+	}
+
+	if err := adapter.SendChunk(audio); err != nil {
+		t.Fatalf("SendChunk failed: %v", err)
+	}
+
+	// give time for message to be sent
+	time.Sleep(100 * time.Millisecond)
+
+	mu.Lock()
+	received := receivedAudio
+	mu.Unlock()
+
+	if !received {
+		t.Error("server did not receive audio chunk")
+	}
+}
+
+func TestOpenAIRealtimeAdapter_TranscriptionResults(t *testing.T) {
+	server := mockOpenAIRealtimeServer(t, func(conn *websocket.Conn) {
+		// send session.created
+		conn.WriteJSON(map[string]interface{}{"type": "session.created", "session": map[string]interface{}{"id": "sess_123"}})
+
+		// read session.update
+		conn.ReadMessage()
+
+		// send session.updated
+		conn.WriteJSON(map[string]interface{}{"type": "session.updated"})
+
+		// simulate transcription events
+		time.Sleep(50 * time.Millisecond)
+
+		// speech started
+		conn.WriteJSON(map[string]interface{}{
+			"type": "input_audio_buffer.speech_started",
+		})
+
+		// partial transcription
+		conn.WriteJSON(map[string]interface{}{
+			"type":  "conversation.item.input_audio_transcription.delta",
+			"delta": "Hello",
+		})
+
+		// more partial
+		conn.WriteJSON(map[string]interface{}{
+			"type":  "conversation.item.input_audio_transcription.delta",
+			"delta": " world",
+		})
+
+		// final transcription
+		conn.WriteJSON(map[string]interface{}{
+			"type":       "conversation.item.input_audio_transcription.completed",
+			"transcript": "Hello world",
+		})
+
+		// keep connection open
+		for {
+			_, _, err := conn.ReadMessage()
+			if err != nil {
+				return
+			}
+		}
+	})
+	defer server.Close()
+
+	wsURL := "ws" + strings.TrimPrefix(server.URL, "http")
+	endpoint := &provider.EndpointConfig{BaseURL: wsURL, Path: ""}
+	adapter := NewOpenAIRealtimeAdapter(endpoint, "sk-test", "gpt-4o-realtime-preview", "en")
+
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+
+	if err := adapter.Start(ctx, ""); err != nil {
+		t.Fatalf("Start failed: %v", err)
+	}
+	defer adapter.Close()
+
+	results := adapter.Results()
+
+	// collect results
+	var partials []string
+	var finals []string
+	timeout := time.After(2 * time.Second)
+
+	for {
+		select {
+		case result, ok := <-results:
+			if !ok {
+				goto done
+			}
+			if result.Error != nil {
+				continue
+			}
+			if result.IsFinal {
+				finals = append(finals, result.Text)
+			} else {
+				partials = append(partials, result.Text)
+			}
+			if len(finals) > 0 {
+				goto done
+			}
+		case <-timeout:
+			goto done
+		}
+	}
+done:
+
+	if len(partials) != 2 {
+		t.Errorf("expected 2 partial results, got %d: %v", len(partials), partials)
+	}
+
+	if len(finals) != 1 {
+		t.Errorf("expected 1 final result, got %d: %v", len(finals), finals)
+	}
+
+	if len(finals) > 0 && finals[0] != "Hello world" {
+		t.Errorf("expected final 'Hello world', got %q", finals[0])
+	}
+}
+
+func TestOpenAIRealtimeAdapter_ErrorHandling(t *testing.T) {
+	server := mockOpenAIRealtimeServer(t, func(conn *websocket.Conn) {
+		// send session.created
+		conn.WriteJSON(map[string]interface{}{"type": "session.created", "session": map[string]interface{}{"id": "sess_123"}})
+
+		// read session.update
+		conn.ReadMessage()
+
+		// send session.updated
+		conn.WriteJSON(map[string]interface{}{"type": "session.updated"})
+
+		// send error event
+		time.Sleep(50 * time.Millisecond)
+		conn.WriteJSON(map[string]interface{}{
+			"type": "error",
+			"error": map[string]interface{}{
+				"type":    "invalid_request_error",
+				"code":    "invalid_audio",
+				"message": "Audio format is invalid",
+			},
+		})
+
+		// keep connection open
+		for {
+			_, _, err := conn.ReadMessage()
+			if err != nil {
+				return
+			}
+		}
+	})
+	defer server.Close()
+
+	wsURL := "ws" + strings.TrimPrefix(server.URL, "http")
+	endpoint := &provider.EndpointConfig{BaseURL: wsURL, Path: ""}
+	adapter := NewOpenAIRealtimeAdapter(endpoint, "sk-test", "gpt-4o-realtime-preview", "")
+
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+	defer cancel()
+
+	if err := adapter.Start(ctx, ""); err != nil {
+		t.Fatalf("Start failed: %v", err)
+	}
+	defer adapter.Close()
+
+	results := adapter.Results()
+
+	// wait for error
+	select {
+	case result := <-results:
+		if result.Error == nil {
+			t.Error("expected error result")
+		}
+		if !strings.Contains(result.Error.Error(), "invalid_audio") {
+			t.Errorf("expected error containing 'invalid_audio', got: %v", result.Error)
+		}
+	case <-time.After(2 * time.Second):
+		t.Error("timeout waiting for error result")
+	}
+}
+
+func TestOpenAIRealtimeAdapter_Reconnection(t *testing.T) {
+	connectCount := 0
+	var mu sync.Mutex
+
+	server := mockOpenAIRealtimeServer(t, func(conn *websocket.Conn) {
+		mu.Lock()
+		connectCount++
+		count := connectCount
+		mu.Unlock()
+
+		// send session.created
+		conn.WriteJSON(map[string]interface{}{"type": "session.created", "session": map[string]interface{}{"id": "sess_" + string(rune('0'+count))}})
+
+		// read session.update
+		conn.ReadMessage()
+
+		// send session.updated
+		conn.WriteJSON(map[string]interface{}{"type": "session.updated"})
+
+		// first connection: close immediately to trigger reconnect
+		if count == 1 {
+			time.Sleep(50 * time.Millisecond)
+			conn.Close()
+			return
+		}
+
+		// second connection: stay open
+		for {
+			_, _, err := conn.ReadMessage()
+			if err != nil {
+				return
+			}
+		}
+	})
+	defer server.Close()
+
+	wsURL := "ws" + strings.TrimPrefix(server.URL, "http")
+	endpoint := &provider.EndpointConfig{BaseURL: wsURL, Path: ""}
+	adapter := NewOpenAIRealtimeAdapter(endpoint, "sk-test", "gpt-4o-realtime-preview", "")
+	adapter.retryDelays = []time.Duration{10 * time.Millisecond, 20 * time.Millisecond, 40 * time.Millisecond}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	if err := adapter.Start(ctx, ""); err != nil {
+		t.Fatalf("Start failed: %v", err)
+	}
+	defer adapter.Close()
+
+	// wait for reconnection
+	time.Sleep(500 * time.Millisecond)
+
+	mu.Lock()
+	finalCount := connectCount
+	mu.Unlock()
+
+	if finalCount < 2 {
+		t.Errorf("expected at least 2 connections (reconnection), got %d", finalCount)
+	}
+}
+
+func TestOpenAIRealtimeAdapter_Close(t *testing.T) {
+	server := mockOpenAIRealtimeServer(t, func(conn *websocket.Conn) {
+		conn.WriteJSON(map[string]interface{}{"type": "session.created", "session": map[string]interface{}{"id": "sess_123"}})
+		conn.ReadMessage()
+		conn.WriteJSON(map[string]interface{}{"type": "session.updated"})
+
+		for {
+			_, _, err := conn.ReadMessage()
+			if err != nil {
+				return
+			}
+		}
+	})
+	defer server.Close()
+
+	wsURL := "ws" + strings.TrimPrefix(server.URL, "http")
+	endpoint := &provider.EndpointConfig{BaseURL: wsURL, Path: ""}
+	adapter := NewOpenAIRealtimeAdapter(endpoint, "sk-test", "gpt-4o-realtime-preview", "")
+
+	ctx := context.Background()
+
+	if err := adapter.Start(ctx, ""); err != nil {
+		t.Fatalf("Start failed: %v", err)
+	}
+
+	// close should not block or panic
+	err := adapter.Close()
+	if err != nil {
+		t.Errorf("Close returned error: %v", err)
+	}
+
+	// results channel should be closed
+	select {
+	case _, ok := <-adapter.Results():
+		if ok {
+			// drain any remaining results
+			for range adapter.Results() {
+			}
+		}
+	case <-time.After(time.Second):
+		t.Error("results channel not closed after Close()")
+	}
+}
+
+func TestResample16to24(t *testing.T) {
+	// test with simple audio data
+	input := make([]byte, 32) // 16 samples at 16kHz
+	for i := 0; i < 16; i++ {
+		// write sample value (little-endian)
+		sample := int16(i * 1000)
+		input[i*2] = byte(sample)
+		input[i*2+1] = byte(sample >> 8)
+	}
+
+	output := resample16to24(input)
+
+	// 16 samples at 16kHz = 24 samples at 24kHz (ratio 1.5)
+	expectedSamples := 24
+	if len(output) != expectedSamples*2 {
+		t.Errorf("expected %d bytes, got %d", expectedSamples*2, len(output))
+	}
+
+	// output should have reasonable values (interpolated)
+	for i := 0; i < expectedSamples; i++ {
+		sample := int16(output[i*2]) | (int16(output[i*2+1]) << 8)
+		if sample < -32768 || sample > 32767 {
+			t.Errorf("sample %d out of range: %d", i, sample)
+		}
+	}
+}
+
+func TestResample16to24_EmptyInput(t *testing.T) {
+	output := resample16to24([]byte{})
+	if len(output) != 0 {
+		t.Errorf("expected empty output for empty input, got %d bytes", len(output))
+	}
+}
+
+func TestResample16to24_SingleSample(t *testing.T) {
+	input := []byte{0x00, 0x10} // single sample
+	output := resample16to24(input)
+	// with only 1 sample, output should be minimal
+	if len(output) == 0 {
+		t.Error("expected non-empty output for single sample")
+	}
+}

progress.txt

@@ -379,3 +379,19 @@ Started: Sun Feb  1 12:22:47 AM CET 2026
 - Added TestOpenAIRealtimeModel test verifying all properties
 - Updated TestModelsOfType to expect 4 transcription models for OpenAI
 - All tests passing, typecheck passes
+
+### Task 37: Create OpenAI Realtime StreamingAdapter
+- Created `internal/transcriber/adapter_openai_realtime.go`
+- OpenAIRealtimeAdapter struct: endpoint, apiKey, model, language, conn, resultsCh, mu, ctx/cancel, WaitGroup
+- Start(): connects to wss://api.openai.com/v1/realtime?model=X with Bearer auth and OpenAI-Beta header
+- Sends session.update to configure transcription-only mode (modalities=['text'], input_audio_format='pcm16')
+- Enables input_audio_transcription with gpt-4o-transcribe model
+- Uses server_vad turn detection for automatic speech detection
+- SendChunk(): resamples audio from 16kHz to 24kHz, sends input_audio_buffer.append with base64 audio
+- readLoop goroutine: parses conversation.item.input_audio_transcription.delta (partial) and .completed (final)
+- Handles error events, speech_started, speech_stopped, session events
+- Close(): cancels context, sends close frame, waits for reader goroutine
+- Added resample16to24() for 16kHz to 24kHz PCM conversion using linear interpolation
+- Added reconnection logic (maxRetries=3, exponential backoff 1s, 2s, 4s) - same pattern as ElevenLabs/Deepgram
+- Comprehensive tests with mock WebSocket server
+- All tests passing with -race flag, typecheck passes

tasks/prd.jsonc

@@ -869,7 +869,7 @@
 				"Close() terminates cleanly",
 				"Typecheck passes"
 			],
-			"passes": false
+			"passes": true
 		},
 		{
 			"title": "Add reconnection logic to OpenAI Realtime StreamingAdapter",