fix(openai): ignore empty websocket frames

pkg/model/provider/openai/ws_stream.go

@@ -1,6 +1,7 @@
 package openai
 
 import (
+	"bytes"
 	"context"
 	"encoding/json"
 	"fmt"
@@ -124,30 +125,39 @@ func (s *wsStream) Next() bool {
 		return false
 	}
 
-	_, data, err := s.conn.ReadMessage()
-	if err != nil {
-		if websocket.IsCloseError(err,
-			websocket.CloseNormalClosure,
-			websocket.CloseGoingAway,
-			websocket.CloseNoStatusReceived,
-		) {
+	for {
+		_, data, err := s.conn.ReadMessage()
+		if err != nil {
+			if websocket.IsCloseError(err,
+				websocket.CloseNormalClosure,
+				websocket.CloseGoingAway,
+				websocket.CloseNoStatusReceived,
+			) {
+				s.done = true
+				return false
+			}
+			s.err = fmt.Errorf("websocket read: %w", err)
 			s.done = true
 			return false
 		}
-		s.err = fmt.Errorf("websocket read: %w", err)
-		s.done = true
-		return false
-	}
 
-	var event responses.ResponseStreamEventUnion
-	if err := json.Unmarshal(data, &event); err != nil {
-		s.err = fmt.Errorf("websocket unmarshal event: %w", err)
-		s.done = true
-		return false
-	}
+		if len(bytes.TrimSpace(data)) == 0 {
+			slog.Debug("Ignoring empty WebSocket frame")
+			continue
+		}
 
-	s.current = event
+		var event responses.ResponseStreamEventUnion
+		if err := json.Unmarshal(data, &event); err != nil {
+			s.err = fmt.Errorf("websocket unmarshal event: %w", err)
+			s.done = true
+			return false
+		}
+
+		s.current = event
+		break
+	}
 
+	event := s.current
 	slog.Debug("WebSocket event received", "type", event.Type)
 
 	// Check for server-side error events.

pkg/model/provider/openai/ws_stream_test.go

@@ -134,6 +134,70 @@ func TestWSStream_TextDelta(t *testing.T) {
 	assert.ErrorIs(t, err, io.EOF)
 }
 
+func TestWSStream_IgnoresEmptyFrames(t *testing.T) {
+	t.Parallel()
+
+	upgrader := websocket.Upgrader{CheckOrigin: func(*http.Request) bool { return true }}
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		conn, err := upgrader.Upgrade(w, r, nil)
+		if err != nil {
+			t.Errorf("WebSocket upgrade failed: %v", err)
+			return
+		}
+		defer conn.Close()
+
+		_, _, err = conn.ReadMessage()
+		if err != nil {
+			t.Errorf("Failed to read response.create: %v", err)
+			return
+		}
+
+		assert.NoError(t, conn.WriteMessage(websocket.TextMessage, []byte("   ")))
+		assert.NoError(t, conn.WriteJSON(map[string]any{
+			"type":    "response.output_text.delta",
+			"delta":   "Hi from OVH",
+			"item_id": "item_1",
+		}))
+		assert.NoError(t, conn.WriteJSON(map[string]any{
+			"type": "response.completed",
+			"response": map[string]any{
+				"id":     "resp_ovh",
+				"output": []any{},
+				"usage": map[string]any{
+					"input_tokens":          4,
+					"output_tokens":         3,
+					"total_tokens":          7,
+					"input_tokens_details":  map[string]any{"cached_tokens": 0},
+					"output_tokens_details": map[string]any{"reasoning_tokens": 0},
+				},
+			},
+		}))
+	}))
+	defer srv.Close()
+
+	wsURL := "ws" + strings.TrimPrefix(srv.URL, "http")
+	stream, err := dialWebSocket(t.Context(), wsURL, http.Header{}, defaultTestParams())
+	require.NoError(t, err)
+	defer stream.Close()
+
+	adapter := newResponseStreamAdapter(stream, true)
+
+	resp, err := adapter.Recv()
+	require.NoError(t, err)
+	require.Len(t, resp.Choices, 1)
+	assert.Equal(t, "Hi from OVH", resp.Choices[0].Delta.Content)
+
+	resp, err = adapter.Recv()
+	require.NoError(t, err)
+	require.Len(t, resp.Choices, 1)
+	assert.Equal(t, chat.FinishReasonStop, resp.Choices[0].FinishReason)
+	assert.NotNil(t, resp.Usage)
+	assert.Equal(t, int64(3), resp.Usage.OutputTokens)
+
+	_, err = adapter.Recv()
+	assert.ErrorIs(t, err, io.EOF)
+}
+
 func TestWSStream_ToolCall(t *testing.T) {
 	t.Parallel()