feat(realtime): wire streamLLMResponse for token-streamed replies

triggerResponseAtTurn takes a streamed path when pipeline.streaming.llm is
set, the turn has no tools, and audio is requested: streamLLMResponse
announces the assistant item, drives the LLM token callback through a
speechStreamer (reasoning-stripped transcript deltas + sentence-piped TTS),
and emits the terminal events. Tool turns and non-streaming pipelines keep
the existing buffered path unchanged, so this is strictly opt-in.

Assisted-by: Claude:claude-opus-4-8 go vet
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

core/http/endpoints/openai/realtime.go

@@ -1496,6 +1496,23 @@ func triggerResponseAtTurn(ctx context.Context, session *Session, conv *Conversa
 		},
 	})
 
+	// Streamed LLM path: when the pipeline opts into LLM streaming and the turn
+	// cannot produce a tool call (no tools), stream tokens straight to the client
+	// as transcript deltas and sentence-pipe them into TTS. Tool turns fall
+	// through to the buffered path below, since partial tool-call output can't be
+	// safely spoken mid-stream.
+	if config != nil && session.ModelConfig != nil && session.ModelConfig.Pipeline.StreamLLM() && len(tools) == 0 {
+		var respMods []types.Modality
+		if overrides != nil {
+			respMods = overrides.OutputModalities
+		}
+		if modalitiesContainAudio(resolveOutputModalities(session.OutputModalities, respMods)) {
+			if streamLLMResponse(ctx, session, conv, t, responseID, conversationHistory, images, config) {
+				return
+			}
+		}
+	}
+
 	predFunc, err := session.ModelInterface.Predict(ctx, conversationHistory, images, nil, nil, nil, tools, toolChoice, nil, nil, nil)
 	if err != nil {
 		sendError(t, "inference_failed", fmt.Sprintf("backend error: %v", err), "", "") // item.Assistant.ID is unknown here

core/http/endpoints/openai/realtime_stream.go

@@ -2,8 +2,13 @@ package openai
 
 import (
 	"context"
+	"encoding/base64"
+	"fmt"
 
+	"github.com/mudler/LocalAI/core/backend"
+	"github.com/mudler/LocalAI/core/config"
 	"github.com/mudler/LocalAI/core/http/endpoints/openai/types"
+	"github.com/mudler/LocalAI/core/schema"
 	"github.com/mudler/LocalAI/pkg/reasoning"
 )
 
@@ -84,3 +89,142 @@ func (s *speechStreamer) finish() (content string, audio []byte, err error) {
 	}
 	return s.extractor.CleanedContent(), s.audio, s.err
 }
+
+// streamLLMResponse drives a streamed, plain-content (no tools) realtime reply.
+// It announces the assistant item before tokens arrive, feeds the LLM token
+// callback through a speechStreamer (transcript deltas + sentence-piped TTS),
+// then emits the terminal events. It returns true when it has fully handled the
+// response so the caller can return; callers must only invoke it for turns with
+// no tools and an audio modality (see triggerResponseAtTurn).
+func streamLLMResponse(ctx context.Context, session *Session, conv *Conversation, t Transport, responseID string, history schema.Messages, images []string, llmCfg *config.ModelConfig) bool {
+	// Announce the assistant item up front so streamed deltas target a known item.
+	item := types.MessageItemUnion{
+		Assistant: &types.MessageItemAssistant{
+			ID:      generateItemID(),
+			Status:  types.ItemStatusInProgress,
+			Content: []types.MessageContentOutput{{Type: types.MessageContentTypeOutputAudio}},
+		},
+	}
+	conv.Lock.Lock()
+	conv.Items = append(conv.Items, &item)
+	conv.Lock.Unlock()
+
+	sendEvent(t, types.ResponseOutputItemAddedEvent{
+		ServerEventBase: types.ServerEventBase{},
+		ResponseID:      responseID,
+		OutputIndex:     0,
+		Item:            item,
+	})
+	sendEvent(t, types.ResponseContentPartAddedEvent{
+		ServerEventBase: types.ServerEventBase{},
+		ResponseID:      responseID,
+		ItemID:          item.Assistant.ID,
+		OutputIndex:     0,
+		ContentIndex:    0,
+		Part:            item.Assistant.Content[0],
+	})
+
+	cancel := func() {
+		conv.Lock.Lock()
+		for i := len(conv.Items) - 1; i >= 0; i-- {
+			if conv.Items[i].Assistant != nil && conv.Items[i].Assistant.ID == item.Assistant.ID {
+				conv.Items = append(conv.Items[:i], conv.Items[i+1:]...)
+				break
+			}
+		}
+		conv.Lock.Unlock()
+		sendEvent(t, types.ResponseDoneEvent{
+			ServerEventBase: types.ServerEventBase{},
+			Response:        types.Response{ID: responseID, Object: "realtime.response", Status: types.ResponseStatusCancelled},
+		})
+	}
+
+	var template string
+	if llmCfg.TemplateConfig.UseTokenizerTemplate {
+		template = llmCfg.GetModelTemplate()
+	} else {
+		template = llmCfg.TemplateConfig.Chat
+	}
+	thinkingStartToken := reasoning.DetectThinkingStartToken(template, &llmCfg.ReasoningConfig)
+
+	streamer := newSpeechStreamer(ctx, t, session, responseID, item.Assistant.ID, thinkingStartToken, llmCfg.ReasoningConfig)
+	cb := func(token string, _ backend.TokenUsage) bool {
+		if ctx.Err() != nil {
+			return false
+		}
+		streamer.onToken(token)
+		return true
+	}
+
+	predFunc, err := session.ModelInterface.Predict(ctx, history, images, nil, nil, cb, nil, nil, nil, nil, nil)
+	if err != nil {
+		sendError(t, "inference_failed", fmt.Sprintf("backend error: %v", err), "", item.Assistant.ID)
+		return true
+	}
+	if _, err := predFunc(); err != nil {
+		if ctx.Err() != nil {
+			cancel()
+			return true
+		}
+		sendError(t, "prediction_failed", fmt.Sprintf("backend error: %v", err), "", item.Assistant.ID)
+		return true
+	}
+	if ctx.Err() != nil {
+		cancel()
+		return true
+	}
+
+	content, audio, err := streamer.finish()
+	if err != nil {
+		sendError(t, "tts_error", fmt.Sprintf("TTS generation failed: %v", err), "", item.Assistant.ID)
+		return true
+	}
+
+	_, isWebRTC := t.(*WebRTCTransport)
+
+	sendEvent(t, types.ResponseOutputAudioTranscriptDoneEvent{
+		ServerEventBase: types.ServerEventBase{},
+		ResponseID:      responseID,
+		ItemID:          item.Assistant.ID,
+		OutputIndex:     0,
+		ContentIndex:    0,
+		Transcript:      content,
+	})
+	if !isWebRTC {
+		sendEvent(t, types.ResponseOutputAudioDoneEvent{
+			ServerEventBase: types.ServerEventBase{},
+			ResponseID:      responseID,
+			ItemID:          item.Assistant.ID,
+			OutputIndex:     0,
+			ContentIndex:    0,
+		})
+	}
+
+	conv.Lock.Lock()
+	item.Assistant.Status = types.ItemStatusCompleted
+	item.Assistant.Content[0].Transcript = content
+	if !isWebRTC {
+		item.Assistant.Content[0].Audio = base64.StdEncoding.EncodeToString(audio)
+	}
+	conv.Lock.Unlock()
+
+	sendEvent(t, types.ResponseContentPartDoneEvent{
+		ServerEventBase: types.ServerEventBase{},
+		ResponseID:      responseID,
+		ItemID:          item.Assistant.ID,
+		OutputIndex:     0,
+		ContentIndex:    0,
+		Part:            item.Assistant.Content[0],
+	})
+	sendEvent(t, types.ResponseOutputItemDoneEvent{
+		ServerEventBase: types.ServerEventBase{},
+		ResponseID:      responseID,
+		OutputIndex:     0,
+		Item:            item,
+	})
+	sendEvent(t, types.ResponseDoneEvent{
+		ServerEventBase: types.ServerEventBase{},
+		Response:        types.Response{ID: responseID, Object: "realtime.response", Status: types.ResponseStatusCompleted},
+	})
+	return true
+}