Merge pull request #3855 from pipecat-ai/mb/context-summarization-improvements

Improve context summarization with dedicated LLM, timeout, and observability

changelog/3855.added.2.md

@@ -0,0 +1 @@
+- Added optional `llm` field to `LLMContextSummarizationConfig` for routing summarization to a dedicated LLM service (e.g., a cheaper/faster model) instead of the pipeline's primary model.

changelog/3855.added.3.md

@@ -0,0 +1 @@
+- Added `summarization_timeout` to `LLMContextSummarizationConfig` (default 120s) to prevent hung LLM calls from permanently blocking future summarizations.

changelog/3855.added.4.md

@@ -0,0 +1 @@
+- Added `on_summary_applied` event to `LLMContextSummarizer` for observability, providing message counts before and after context summarization.

changelog/3855.added.md

@@ -0,0 +1 @@
+- Added `summary_message_template` to `LLMContextSummarizationConfig` for customizing how summaries are formatted when injected into context (e.g., wrapping in XML tags).

changelog/3855.changed.md

@@ -0,0 +1 @@
+- Updated context summarization to use `user` role instead of `assistant` for summary messages.

examples/foundational/54-context-summarization-openai.py

@@ -20,14 +20,13 @@ from loguru import logger
 
 from pipecat.adapters.schemas.function_schema import FunctionSchema
 from pipecat.adapters.schemas.tools_schema import ToolsSchema
-from pipecat.audio.turn.smart_turn.local_smart_turn_v3 import LocalSmartTurnAnalyzerV3
 from pipecat.audio.vad.silero import SileroVADAnalyzer
-from pipecat.audio.vad.vad_analyzer import VADParams
 from pipecat.frames.frames import LLMRunFrame
 from pipecat.pipeline.pipeline import Pipeline
 from pipecat.pipeline.runner import PipelineRunner
 from pipecat.pipeline.task import PipelineParams, PipelineTask
 from pipecat.processors.aggregators.llm_context import LLMContext
+from pipecat.processors.aggregators.llm_context_summarizer import SummaryAppliedEvent
 from pipecat.processors.aggregators.llm_response_universal import (
     LLMAssistantAggregatorParams,
     LLMContextAggregatorPair,
@@ -42,8 +41,6 @@ from pipecat.services.openai.llm import OpenAILLMService
 from pipecat.transports.base_transport import BaseTransport, TransportParams
 from pipecat.transports.daily.transport import DailyParams
 from pipecat.transports.websocket.fastapi import FastAPIWebsocketParams
-from pipecat.turns.user_stop import TurnAnalyzerUserTurnStopStrategy
-from pipecat.turns.user_turn_strategies import UserTurnStrategies
 from pipecat.utils.context.llm_context_summarization import LLMContextSummarizationConfig
 
 load_dotenv(override=True)
@@ -120,10 +117,7 @@ async def run_bot(transport: BaseTransport, runner_args: RunnerArguments):
     user_aggregator, assistant_aggregator = LLMContextAggregatorPair(
         context,
         user_params=LLMUserAggregatorParams(
-            user_turn_strategies=UserTurnStrategies(
+            vad_analyzer=SileroVADAnalyzer(),
-                stop=[TurnAnalyzerUserTurnStopStrategy(turn_analyzer=LocalSmartTurnAnalyzerV3())]
-            ),
-            vad_analyzer=SileroVADAnalyzer(params=VADParams(stop_secs=0.2)),
         ),
         assistant_params=LLMAssistantAggregatorParams(
             enable_context_summarization=True,
@@ -138,6 +132,19 @@ async def run_bot(transport: BaseTransport, runner_args: RunnerArguments):
         ),
     )
 
+    # Listen for summarization events
+    summarizer = assistant_aggregator._summarizer
+    if summarizer:
+
+        @summarizer.event_handler("on_summary_applied")
+        async def on_summary_applied(summarizer, event: SummaryAppliedEvent):
+            logger.info(
+                f"Context summarized: {event.original_message_count} messages -> "
+                f"{event.new_message_count} messages "
+                f"({event.summarized_message_count} summarized, "
+                f"{event.preserved_message_count} preserved)"
+            )
+
     pipeline = Pipeline(
         [
             transport.input(),  # Transport user input

examples/foundational/54a-context-summarization-google.py

@@ -20,14 +20,13 @@ from loguru import logger
 
 from pipecat.adapters.schemas.function_schema import FunctionSchema
 from pipecat.adapters.schemas.tools_schema import ToolsSchema
-from pipecat.audio.turn.smart_turn.local_smart_turn_v3 import LocalSmartTurnAnalyzerV3
 from pipecat.audio.vad.silero import SileroVADAnalyzer
-from pipecat.audio.vad.vad_analyzer import VADParams
 from pipecat.frames.frames import LLMRunFrame
 from pipecat.pipeline.pipeline import Pipeline
 from pipecat.pipeline.runner import PipelineRunner
 from pipecat.pipeline.task import PipelineParams, PipelineTask
 from pipecat.processors.aggregators.llm_context import LLMContext
+from pipecat.processors.aggregators.llm_context_summarizer import SummaryAppliedEvent
 from pipecat.processors.aggregators.llm_response_universal import (
     LLMAssistantAggregatorParams,
     LLMContextAggregatorPair,
@@ -42,8 +41,6 @@ from pipecat.services.llm_service import FunctionCallParams
 from pipecat.transports.base_transport import BaseTransport, TransportParams
 from pipecat.transports.daily.transport import DailyParams
 from pipecat.transports.websocket.fastapi import FastAPIWebsocketParams
-from pipecat.turns.user_stop import TurnAnalyzerUserTurnStopStrategy
-from pipecat.turns.user_turn_strategies import UserTurnStrategies
 from pipecat.utils.context.llm_context_summarization import LLMContextSummarizationConfig
 
 load_dotenv(override=True)
@@ -120,10 +117,7 @@ async def run_bot(transport: BaseTransport, runner_args: RunnerArguments):
     user_aggregator, assistant_aggregator = LLMContextAggregatorPair(
         context,
         user_params=LLMUserAggregatorParams(
-            user_turn_strategies=UserTurnStrategies(
+            vad_analyzer=SileroVADAnalyzer(),
-                stop=[TurnAnalyzerUserTurnStopStrategy(turn_analyzer=LocalSmartTurnAnalyzerV3())]
-            ),
-            vad_analyzer=SileroVADAnalyzer(params=VADParams(stop_secs=0.2)),
         ),
         assistant_params=LLMAssistantAggregatorParams(
             enable_context_summarization=True,
@@ -138,6 +132,19 @@ async def run_bot(transport: BaseTransport, runner_args: RunnerArguments):
         ),
     )
 
+    # Listen for summarization events
+    summarizer = assistant_aggregator._summarizer
+    if summarizer:
+
+        @summarizer.event_handler("on_summary_applied")
+        async def on_summary_applied(summarizer, event: SummaryAppliedEvent):
+            logger.info(
+                f"Context summarized: {event.original_message_count} messages -> "
+                f"{event.new_message_count} messages "
+                f"({event.summarized_message_count} summarized, "
+                f"{event.preserved_message_count} preserved)"
+            )
+
     pipeline = Pipeline(
         [
             transport.input(),  # Transport user input

examples/foundational/54c-context-summarization-dedicated-llm.py

@@ -0,0 +1,231 @@
+#
+# Copyright (c) 2024-2026, Daily
+#
+# SPDX-License-Identifier: BSD 2-Clause License
+#
+
+"""Example demonstrating advanced context summarization configuration.
+
+This example shows how to customize context summarization with:
+- A dedicated cheap/fast LLM for generating summaries (Gemini Flash)
+- A custom summary message template (XML tags)
+- A custom summarization prompt
+- A summarization timeout
+- The on_summary_applied event for observability
+"""
+
+import asyncio
+import os
+
+from dotenv import load_dotenv
+from loguru import logger
+
+from pipecat.adapters.schemas.function_schema import FunctionSchema
+from pipecat.adapters.schemas.tools_schema import ToolsSchema
+from pipecat.audio.vad.silero import SileroVADAnalyzer
+from pipecat.frames.frames import LLMRunFrame
+from pipecat.pipeline.pipeline import Pipeline
+from pipecat.pipeline.runner import PipelineRunner
+from pipecat.pipeline.task import PipelineParams, PipelineTask
+from pipecat.processors.aggregators.llm_context import LLMContext
+from pipecat.processors.aggregators.llm_context_summarizer import SummaryAppliedEvent
+from pipecat.processors.aggregators.llm_response_universal import (
+    LLMAssistantAggregatorParams,
+    LLMContextAggregatorPair,
+    LLMUserAggregatorParams,
+)
+from pipecat.runner.types import RunnerArguments
+from pipecat.runner.utils import create_transport
+from pipecat.services.cartesia.tts import CartesiaTTSService
+from pipecat.services.deepgram.stt import DeepgramSTTService
+from pipecat.services.google import GoogleLLMService
+from pipecat.services.llm_service import FunctionCallParams
+from pipecat.services.openai.llm import OpenAILLMService
+from pipecat.transports.base_transport import BaseTransport, TransportParams
+from pipecat.transports.daily.transport import DailyParams
+from pipecat.transports.websocket.fastapi import FastAPIWebsocketParams
+from pipecat.utils.context.llm_context_summarization import LLMContextSummarizationConfig
+
+load_dotenv(override=True)
+
+# We use lambdas to defer transport parameter creation until the transport
+# type is selected at runtime.
+transport_params = {
+    "daily": lambda: DailyParams(
+        audio_in_enabled=True,
+        audio_out_enabled=True,
+    ),
+    "twilio": lambda: FastAPIWebsocketParams(
+        audio_in_enabled=True,
+        audio_out_enabled=True,
+    ),
+    "webrtc": lambda: TransportParams(
+        audio_in_enabled=True,
+        audio_out_enabled=True,
+    ),
+}
+
+# Custom summarization prompt tailored to the application
+CUSTOM_SUMMARIZATION_PROMPT = """Summarize this conversation, preserving:
+- Key decisions and agreements
+- Important facts and user preferences
+- Any pending action items or unresolved questions
+
+Be concise. Use clear, factual statements grouped by topic.
+Omit greetings, small talk, and resolved tangents."""
+
+
+# Tool functions for the LLM
+async def get_current_weather(params: FunctionCallParams):
+    """Get the current weather."""
+    logger.info("Tool called: get_current_weather")
+    await asyncio.sleep(1)  # Simulate some processing
+    await params.result_callback({"conditions": "nice", "temperature": "75"})
+
+
+async def run_bot(transport: BaseTransport, runner_args: RunnerArguments):
+    logger.info("Starting bot")
+
+    stt = DeepgramSTTService(api_key=os.getenv("DEEPGRAM_API_KEY"))
+
+    tts = CartesiaTTSService(
+        api_key=os.getenv("CARTESIA_API_KEY"),
+        voice_id="71a7ad14-091c-4e8e-a314-022ece01c121",  # British Reading Lady
+    )
+
+    # Primary LLM for conversation (could be any provider)
+    llm = OpenAILLMService(api_key=os.getenv("OPENAI_API_KEY"))
+
+    # Dedicated cheap/fast LLM for summarization only
+    summarization_llm = GoogleLLMService(
+        api_key=os.getenv("GOOGLE_API_KEY"),
+        model="gemini-2.5-flash",
+    )
+
+    # Register tool functions
+    llm.register_function("get_current_weather", get_current_weather)
+
+    weather_function = FunctionSchema(
+        name="get_current_weather",
+        description="Get the current weather",
+        properties={
+            "location": {
+                "type": "string",
+                "description": "The city and state, e.g. San Francisco, CA",
+            },
+            "format": {
+                "type": "string",
+                "enum": ["celsius", "fahrenheit"],
+                "description": "The temperature unit to use. Infer this from the user's location.",
+            },
+        },
+        required=["location", "format"],
+    )
+    tools = ToolsSchema(standard_tools=[weather_function])
+
+    messages = [
+        {
+            "role": "system",
+            "content": (
+                "You are a helpful LLM in a WebRTC call. Your goal is to demonstrate "
+                "your capabilities in a succinct way. Your output will be spoken aloud, "
+                "so avoid special characters that can't easily be spoken. Respond to what "
+                "the user said in a creative and helpful way. You have access to tools to "
+                "get the current weather - use them when relevant.\n\n"
+                "When you see a <context_summary> block, it contains a compressed summary "
+                "of earlier conversation. Use it as reference but don't mention it to the user."
+            ),
+        },
+    ]
+
+    context = LLMContext(messages, tools=tools)
+
+    # Create aggregators with custom summarization
+    user_aggregator, assistant_aggregator = LLMContextAggregatorPair(
+        context,
+        user_params=LLMUserAggregatorParams(
+            vad_analyzer=SileroVADAnalyzer(),
+        ),
+        assistant_params=LLMAssistantAggregatorParams(
+            enable_context_summarization=True,
+            context_summarization_config=LLMContextSummarizationConfig(
+                # Trigger thresholds (low values to demonstrate quickly)
+                max_context_tokens=1000,
+                max_unsummarized_messages=10,
+                # Summary generation
+                target_context_tokens=800,
+                min_messages_after_summary=2,
+                summarization_prompt=CUSTOM_SUMMARIZATION_PROMPT,
+                # Custom summary format - wrap in XML tags so the system
+                # prompt can identify summaries vs. live conversation
+                summary_message_template="<context_summary>\n{summary}\n</context_summary>",
+                # Use a dedicated cheap LLM for summarization instead of
+                # the primary conversation model
+                llm=summarization_llm,
+                # Cancel summarization if it takes longer than 60 seconds
+                summarization_timeout=60.0,
+            ),
+        ),
+    )
+
+    # Listen for summarization events
+    summarizer = assistant_aggregator._summarizer
+    if summarizer:
+
+        @summarizer.event_handler("on_summary_applied")
+        async def on_summary_applied(summarizer, event: SummaryAppliedEvent):
+            logger.info(
+                f"Context summarized: {event.original_message_count} messages -> "
+                f"{event.new_message_count} messages "
+                f"({event.summarized_message_count} summarized, "
+                f"{event.preserved_message_count} preserved)"
+            )
+
+    pipeline = Pipeline(
+        [
+            transport.input(),  # Transport user input
+            stt,
+            user_aggregator,  # User responses
+            llm,  # LLM
+            tts,  # TTS
+            transport.output(),  # Transport bot output
+            assistant_aggregator,  # Assistant spoken responses
+        ]
+    )
+
+    task = PipelineTask(
+        pipeline,
+        params=PipelineParams(
+            enable_metrics=True,
+            enable_usage_metrics=True,
+        ),
+        idle_timeout_secs=runner_args.pipeline_idle_timeout_secs,
+    )
+
+    @transport.event_handler("on_client_connected")
+    async def on_client_connected(transport, client):
+        logger.info("Client connected")
+        # Kick off the conversation.
+        messages.append({"role": "system", "content": "Please introduce yourself to the user."})
+        await task.queue_frames([LLMRunFrame()])
+
+    @transport.event_handler("on_client_disconnected")
+    async def on_client_disconnected(transport, client):
+        logger.info("Client disconnected")
+        await task.cancel()
+
+    runner = PipelineRunner(handle_sigint=runner_args.handle_sigint)
+
+    await runner.run(task)
+
+
+async def bot(runner_args: RunnerArguments):
+    """Main bot entry point compatible with Pipecat Cloud."""
+    transport = await create_transport(runner_args, transport_params)
+    await run_bot(transport, runner_args)
+
+
+if __name__ == "__main__":
+    from pipecat.runner.run import main
+
+    main()

src/pipecat/frames/frames.py

@@ -2019,6 +2019,8 @@ class LLMContextSummaryRequestFrame(ControlFrame):
             the summary text.
         summarization_prompt: System prompt instructing the LLM how to generate
             the summary.
+        summarization_timeout: Maximum time in seconds for the LLM to generate a
+            summary. When None, a default timeout of 120s is applied.
     """
 
     request_id: str
@@ -2026,6 +2028,7 @@ class LLMContextSummaryRequestFrame(ControlFrame):
     min_messages_to_keep: int
     target_context_tokens: int
     summarization_prompt: str
+    summarization_timeout: Optional[float] = None
 
 
 @dataclass

src/pipecat/processors/aggregators/llm_context_summarizer.py

@@ -6,8 +6,10 @@
 
 """This module defines a summarizer for managing LLM context summarization."""
 
+import asyncio
 import uuid
-from typing import Optional
+from dataclasses import dataclass
+from typing import TYPE_CHECKING, Optional
 
 from loguru import logger
 
@@ -22,10 +24,33 @@ from pipecat.processors.aggregators.llm_context import LLMContext, LLMSpecificMe
 from pipecat.utils.asyncio.task_manager import BaseTaskManager
 from pipecat.utils.base_object import BaseObject
 from pipecat.utils.context.llm_context_summarization import (
+    DEFAULT_SUMMARIZATION_TIMEOUT,
     LLMContextSummarizationConfig,
     LLMContextSummarizationUtil,
 )
 
+if TYPE_CHECKING:
+    from pipecat.services.llm_service import LLMService
+
+
+@dataclass
+class SummaryAppliedEvent:
+    """Event data emitted when context summarization completes successfully.
+
+    Parameters:
+        original_message_count: Number of messages before summarization.
+        new_message_count: Number of messages after summarization.
+        summarized_message_count: Number of messages that were compressed
+            into the summary.
+        preserved_message_count: Number of recent messages preserved
+            uncompressed.
+    """
+
+    original_message_count: int
+    new_message_count: int
+    summarized_message_count: int
+    preserved_message_count: int
+
 
 class LLMContextSummarizer(BaseObject):
     """Summarizer for managing LLM context summarization.
@@ -39,6 +64,10 @@ class LLMContextSummarizer(BaseObject):
     - on_request_summarization: Emitted when summarization should be triggered.
         The aggregator should broadcast this frame to the LLM service.
 
+    - on_summary_applied: Emitted after a summary has been successfully applied
+        to the context. Receives a SummaryAppliedEvent with metrics about the
+        compression.
+
     Example::
 
         @summarizer.event_handler("on_request_summarization")
@@ -49,6 +78,10 @@ class LLMContextSummarizer(BaseObject):
                 context=frame.context,
                 ...
             )
+
+        @summarizer.event_handler("on_summary_applied")
+        async def on_summary_applied(summarizer, event: SummaryAppliedEvent):
+            logger.info(f"Compressed {event.original_message_count} -> {event.new_message_count} messages")
     """
 
     def __init__(
@@ -74,6 +107,7 @@ class LLMContextSummarizer(BaseObject):
         self._pending_summary_request_id: Optional[str] = None
 
         self._register_event_handler("on_request_summarization", sync=True)
+        self._register_event_handler("on_summary_applied")
 
     @property
     def task_manager(self) -> BaseTaskManager:
@@ -198,8 +232,10 @@ class LLMContextSummarizer(BaseObject):
     async def _request_summarization(self):
         """Request context summarization from LLM service.
 
-        Creates a summarization request frame and emits it via event handler.
+        Creates a summarization request frame and either handles it directly
-        Tracks the request ID to match async responses and prevent race conditions.
+        using a dedicated LLM (if configured) or emits it via event handler
+        for the pipeline's primary LLM. Tracks the request ID to match async
+        responses and prevent race conditions.
         """
         # Generate unique request ID
         request_id = str(uuid.uuid4())
@@ -218,10 +254,63 @@ class LLMContextSummarizer(BaseObject):
             min_messages_to_keep=min_keep,
             target_context_tokens=self._config.target_context_tokens,
             summarization_prompt=self._config.summary_prompt,
+            summarization_timeout=self._config.summarization_timeout,
         )
 
-        # Emit event for aggregator to broadcast
+        if self._config.llm:
-        await self._call_event_handler("on_request_summarization", request_frame)
+            # Use dedicated LLM directly — no need to involve the pipeline
+            self.task_manager.create_task(
+                self._generate_summary_with_dedicated_llm(self._config.llm, request_frame),
+                f"{self}-dedicated-llm-summary",
+            )
+        else:
+            # Emit event for aggregator to broadcast to the pipeline LLM
+            await self._call_event_handler("on_request_summarization", request_frame)
+
+    async def _generate_summary_with_dedicated_llm(
+        self, llm: "LLMService", frame: LLMContextSummaryRequestFrame
+    ):
+        """Generate summary using a dedicated LLM service.
+
+        Calls the dedicated LLM's _generate_summary directly and feeds the
+        result back through _handle_summary_result, bypassing the pipeline.
+
+        Args:
+            llm: The dedicated LLM service to use for summarization.
+            frame: The summarization request frame.
+        """
+        timeout = frame.summarization_timeout or DEFAULT_SUMMARIZATION_TIMEOUT
+
+        try:
+            summary, last_index = await asyncio.wait_for(
+                llm._generate_summary(frame),
+                timeout=timeout,
+            )
+            result_frame = LLMContextSummaryResultFrame(
+                request_id=frame.request_id,
+                summary=summary,
+                last_summarized_index=last_index,
+            )
+        except asyncio.TimeoutError:
+            error = f"Context summarization timed out after {timeout}s"
+            logger.error(f"{self}: {error}")
+            result_frame = LLMContextSummaryResultFrame(
+                request_id=frame.request_id,
+                summary="",
+                last_summarized_index=-1,
+                error=error,
+            )
+        except Exception as e:
+            error = f"Error generating context summary: {e}"
+            logger.error(f"{self}: {error}")
+            result_frame = LLMContextSummaryResultFrame(
+                request_id=frame.request_id,
+                summary="",
+                last_summarized_index=-1,
+                error=error,
+            )
+
+        await self._handle_summary_result(result_frame)
 
     async def _handle_summary_result(self, frame: LLMContextSummaryResultFrame):
         """Handle context summarization result from LLM service.
@@ -306,8 +395,10 @@ class LLMContextSummarizer(BaseObject):
         # Get recent messages to keep
         recent_messages = messages[last_summarized_index + 1 :]
 
-        # Create summary message as an assistant message
+        # Create summary message as a user message (the summary is context
-        summary_message = {"role": "assistant", "content": f"Conversation summary: {summary}"}
+        # provided *to* the assistant, not something the assistant said)
+        summary_content = self._config.summary_message_template.format(summary=summary)
+        summary_message = {"role": "user", "content": summary_content}
 
         # Reconstruct context
         new_messages = []
@@ -317,9 +408,23 @@ class LLMContextSummarizer(BaseObject):
         new_messages.extend(recent_messages)
 
         # Update context
+        original_message_count = len(messages)
+        num_system_preserved = 1 if first_system_msg else 0
         self._context.set_messages(new_messages)
 
+        # Messages actually summarized = index range minus the preserved system message
+        summarized_count = last_summarized_index + 1 - num_system_preserved
+
         logger.info(
-            f"{self}: Applied context summary, compressed {last_summarized_index + 1} messages "
+            f"{self}: Applied context summary, compressed {summarized_count} messages "
-            f"into summary. Context now has {len(new_messages)} messages (was {len(messages)})"
+            f"into summary. Context now has {len(new_messages)} messages (was {original_message_count})"
         )
+
+        # Emit event for observability
+        event = SummaryAppliedEvent(
+            original_message_count=original_message_count,
+            new_message_count=len(new_messages),
+            summarized_message_count=summarized_count,
+            preserved_message_count=len(recent_messages) + num_system_preserved,
+        )
+        await self._call_event_handler("on_summary_applied", event)

src/pipecat/services/llm_service.py

@@ -62,6 +62,7 @@ from pipecat.services.ai_service import AIService
 from pipecat.services.settings import LLMSettings
 from pipecat.turns.user_turn_completion_mixin import UserTurnCompletionLLMServiceMixin
 from pipecat.utils.context.llm_context_summarization import (
+    DEFAULT_SUMMARIZATION_TIMEOUT,
     LLMContextSummarizationUtil,
 )
 
@@ -436,8 +437,15 @@ class LLMService(UserTurnCompletionLLMServiceMixin, AIService):
         last_index = -1
         error = None
 
+        timeout = frame.summarization_timeout or DEFAULT_SUMMARIZATION_TIMEOUT
+
         try:
-            summary, last_index = await self._generate_summary(frame)
+            summary, last_index = await asyncio.wait_for(
+                self._generate_summary(frame),
+                timeout=timeout,
+            )
+        except asyncio.TimeoutError:
+            await self.push_error(error_msg=f"Context summarization timed out after {timeout}s")
         except Exception as e:
             error = f"Error generating context summary: {e}"
             await self.push_error(error, exception=e)

src/pipecat/utils/context/llm_context_summarization.py

@@ -11,12 +11,18 @@ context when token limits are reached, enabling efficient long-running conversat
 """
 
 from dataclasses import dataclass
-from typing import List, Optional
+from typing import TYPE_CHECKING, List, Optional
+
+if TYPE_CHECKING:
+    from pipecat.services.llm_service import LLMService
 
 from loguru import logger
 
 from pipecat.processors.aggregators.llm_context import LLMContext, LLMSpecificMessage
 
+# Fallback timeout (seconds) used when summarization_timeout is None.
+DEFAULT_SUMMARIZATION_TIMEOUT = 120.0
+
 # Token estimation constants
 CHARS_PER_TOKEN = 4  # Industry-standard heuristic: 1 token ≈ 4 characters
 TOKEN_OVERHEAD_PER_MESSAGE = 10  # Estimated structural overhead per message
@@ -73,6 +79,19 @@ class LLMContextSummarizationConfig:
             immediate conversational context.
         summarization_prompt: Custom prompt for the LLM to use when generating
             summaries. If None, uses DEFAULT_SUMMARIZATION_PROMPT.
+        summary_message_template: Template for formatting the summary when
+            injected into context. Must contain ``{summary}`` as a placeholder
+            for the generated summary text. Allows applications to wrap the
+            summary in custom delimiters (e.g., XML tags) so that system
+            prompts can distinguish summaries from live conversation.
+        llm: Optional separate LLM service for generating summaries. When set,
+            summarization requests are sent to this service instead of the
+            pipeline's primary LLM. Useful for routing summarization to a
+            cheaper/faster model (e.g., Gemini Flash) while keeping an
+            expensive model for conversation. If None, uses the pipeline LLM.
+        summarization_timeout: Maximum time in seconds to wait for the LLM to
+            generate a summary. If the call exceeds this timeout, summarization
+            is aborted with an error and future summarizations are unblocked.
     """
 
     max_context_tokens: int = 8000
@@ -80,6 +99,9 @@ class LLMContextSummarizationConfig:
     max_unsummarized_messages: int = 20
     min_messages_after_summary: int = 4
     summarization_prompt: Optional[str] = None
+    summary_message_template: str = "Conversation summary: {summary}"
+    llm: Optional["LLMService"] = None
+    summarization_timeout: float = DEFAULT_SUMMARIZATION_TIMEOUT
 
     def __post_init__(self):
         """Validate configuration parameters."""

tests/test_context_summarization.py

@@ -6,10 +6,11 @@
 
 """Tests for context summarization feature."""
 
+import asyncio
 import unittest
-from unittest.mock import AsyncMock, MagicMock, patch
+from unittest.mock import AsyncMock
 
-from pipecat.frames.frames import LLMContextSummaryRequestFrame
+from pipecat.frames.frames import LLMContextSummaryRequestFrame, LLMContextSummaryResultFrame
 from pipecat.processors.aggregators.llm_context import LLMContext, LLMSpecificMessage
 from pipecat.services.llm_service import LLMService
 from pipecat.utils.context.llm_context_summarization import (
@@ -601,6 +602,250 @@ class TestSummaryGenerationExceptions(unittest.IsolatedAsyncioTestCase):
         self.assertGreater(last_index, -1)
         self.assertEqual(last_index, 1)  # Should be the index of the last summarized message
 
+    async def test_generate_summary_task_timeout(self):
+        """Test that _generate_summary_task handles timeout correctly."""
+        llm_service = LLMService()
+
+        # Mock _generate_summary to hang
+        async def slow_summary(frame):
+            await asyncio.sleep(10)
+            return ("summary", 1)
+
+        llm_service._generate_summary = slow_summary
+
+        broadcast_calls = []
+
+        async def mock_broadcast(frame_class, **kwargs):
+            broadcast_calls.append((frame_class, kwargs))
+
+        llm_service.broadcast_frame = mock_broadcast
+        llm_service.push_error = AsyncMock()
+
+        context = LLMContext()
+        context.add_message({"role": "user", "content": "Message 1"})
+        context.add_message({"role": "assistant", "content": "Response 1"})
+        context.add_message({"role": "user", "content": "Message 2"})
+
+        frame = LLMContextSummaryRequestFrame(
+            request_id="timeout_test",
+            context=context,
+            min_messages_to_keep=1,
+            target_context_tokens=1000,
+            summarization_prompt="Summarize this",
+            summarization_timeout=0.1,  # Very short timeout
+        )
+
+        await llm_service._generate_summary_task(frame)
+
+        # Should have broadcast an error result
+        self.assertEqual(len(broadcast_calls), 1)
+        _, kwargs = broadcast_calls[0]
+        self.assertEqual(kwargs["request_id"], "timeout_test")
+        self.assertEqual(kwargs["summary"], "")
+        self.assertEqual(kwargs["last_summarized_index"], -1)
+        # error is None for timeout path (push_error is called instead)
+        self.assertIsNone(kwargs["error"])
+
+        # push_error should have been called with timeout message
+        llm_service.push_error.assert_called_once()
+        call_args = llm_service.push_error.call_args
+        error_msg = call_args.kwargs.get("error_msg") or call_args.args[0]
+        self.assertIn("timed out", error_msg)
+
+
+class TestDedicatedLLMSummarization(unittest.IsolatedAsyncioTestCase):
+    """Tests for dedicated LLM summarization in LLMContextSummarizer."""
+
+    async def asyncSetUp(self):
+        from pipecat.utils.asyncio.task_manager import TaskManager, TaskManagerParams
+
+        self.task_manager = TaskManager()
+        self.task_manager.setup(TaskManagerParams(loop=asyncio.get_running_loop()))
+
+    def _create_context_and_config(self, dedicated_llm):
+        """Create a context with enough messages and a config with a dedicated LLM."""
+        context = LLMContext()
+        for i in range(10):
+            context.add_message(
+                {"role": "user", "content": f"Test message {i} that adds tokens to context."}
+            )
+
+        config = LLMContextSummarizationConfig(
+            max_context_tokens=50,  # Very low to trigger easily
+            llm=dedicated_llm,
+            summarization_timeout=5.0,
+        )
+        return context, config
+
+    async def test_dedicated_llm_success(self):
+        """Test that dedicated LLM generates summary and applies result."""
+        from pipecat.processors.aggregators.llm_context_summarizer import LLMContextSummarizer
+
+        dedicated_llm = LLMService()
+        dedicated_llm._generate_summary = AsyncMock(return_value=("Dedicated summary", 5))
+
+        context, config = self._create_context_and_config(dedicated_llm)
+        original_message_count = len(context.messages)
+        summarizer = LLMContextSummarizer(context=context, config=config)
+        await summarizer.setup(self.task_manager)
+
+        # Track whether on_request_summarization event fires (it should NOT)
+        event_fired = False
+
+        @summarizer.event_handler("on_request_summarization")
+        async def on_request_summarization(summarizer, frame):
+            nonlocal event_fired
+            event_fired = True
+
+        # Trigger summarization via LLM response start
+        from pipecat.frames.frames import LLMFullResponseStartFrame
+
+        await summarizer.process_frame(LLMFullResponseStartFrame())
+
+        # Wait for the background task to complete
+        await asyncio.sleep(0.1)
+
+        # The event should NOT have fired (dedicated LLM handles it internally)
+        self.assertFalse(event_fired)
+
+        # Verify the dedicated LLM was called
+        dedicated_llm._generate_summary.assert_called_once()
+
+        # Verify summary was applied to context (message count should decrease)
+        self.assertLess(len(context.messages), original_message_count)
+
+        # Verify summary message is present
+        summary_messages = [
+            msg for msg in context.messages if "Conversation summary:" in msg.get("content", "")
+        ]
+        self.assertEqual(len(summary_messages), 1)
+        self.assertIn("Dedicated summary", summary_messages[0]["content"])
+
+        await summarizer.cleanup()
+
+    async def test_dedicated_llm_timeout(self):
+        """Test that dedicated LLM timeout produces error and clears state."""
+        from pipecat.processors.aggregators.llm_context_summarizer import LLMContextSummarizer
+
+        dedicated_llm = LLMService()
+
+        async def slow_summary(frame):
+            await asyncio.sleep(10)
+            return ("summary", 1)
+
+        dedicated_llm._generate_summary = slow_summary
+
+        context, config = self._create_context_and_config(dedicated_llm)
+        config.summarization_timeout = 0.1  # Very short timeout
+        summarizer = LLMContextSummarizer(context=context, config=config)
+        await summarizer.setup(self.task_manager)
+
+        original_message_count = len(context.messages)
+
+        # Trigger summarization
+        from pipecat.frames.frames import LLMFullResponseStartFrame
+
+        await summarizer.process_frame(LLMFullResponseStartFrame())
+
+        # Wait for the background task to complete (timeout + some buffer)
+        await asyncio.sleep(0.3)
+
+        # Context should be unchanged (timeout = error = no summary applied)
+        self.assertEqual(len(context.messages), original_message_count)
+
+        # Summarization state should be cleared so new requests can be made
+        self.assertFalse(summarizer._summarization_in_progress)
+
+        await summarizer.cleanup()
+
+    async def test_dedicated_llm_exception(self):
+        """Test that dedicated LLM exceptions produce error and clear state."""
+        from pipecat.processors.aggregators.llm_context_summarizer import LLMContextSummarizer
+
+        dedicated_llm = LLMService()
+        dedicated_llm._generate_summary = AsyncMock(
+            side_effect=RuntimeError("LLM connection failed")
+        )
+
+        context, config = self._create_context_and_config(dedicated_llm)
+        summarizer = LLMContextSummarizer(context=context, config=config)
+        await summarizer.setup(self.task_manager)
+
+        original_message_count = len(context.messages)
+
+        # Trigger summarization
+        from pipecat.frames.frames import LLMFullResponseStartFrame
+
+        await summarizer.process_frame(LLMFullResponseStartFrame())
+
+        # Wait for the background task to complete
+        await asyncio.sleep(0.1)
+
+        # Context should be unchanged (exception = error = no summary applied)
+        self.assertEqual(len(context.messages), original_message_count)
+
+        # Summarization state should be cleared
+        self.assertFalse(summarizer._summarization_in_progress)
+
+        await summarizer.cleanup()
+
+    async def test_dedicated_llm_does_not_emit_event(self):
+        """Test that summarizer does NOT emit on_request_summarization when dedicated LLM is set."""
+        from pipecat.processors.aggregators.llm_context_summarizer import LLMContextSummarizer
+
+        dedicated_llm = LLMService()
+        dedicated_llm._generate_summary = AsyncMock(return_value=("Summary", 1))
+
+        context, config = self._create_context_and_config(dedicated_llm)
+        summarizer = LLMContextSummarizer(context=context, config=config)
+        await summarizer.setup(self.task_manager)
+
+        event_fired = False
+
+        @summarizer.event_handler("on_request_summarization")
+        async def on_request_summarization(summarizer, frame):
+            nonlocal event_fired
+            event_fired = True
+
+        from pipecat.frames.frames import LLMFullResponseStartFrame
+
+        await summarizer.process_frame(LLMFullResponseStartFrame())
+        await asyncio.sleep(0.1)
+
+        self.assertFalse(event_fired)
+
+        await summarizer.cleanup()
+
+    async def test_no_dedicated_llm_emits_event(self):
+        """Test that summarizer emits on_request_summarization when no dedicated LLM."""
+        from pipecat.processors.aggregators.llm_context_summarizer import LLMContextSummarizer
+
+        context = LLMContext()
+        for i in range(10):
+            context.add_message(
+                {"role": "user", "content": f"Test message {i} that adds tokens to context."}
+            )
+
+        config = LLMContextSummarizationConfig(max_context_tokens=50)
+        summarizer = LLMContextSummarizer(context=context, config=config)
+        await summarizer.setup(self.task_manager)
+
+        request_frame = None
+
+        @summarizer.event_handler("on_request_summarization")
+        async def on_request_summarization(summarizer, frame):
+            nonlocal request_frame
+            request_frame = frame
+
+        from pipecat.frames.frames import LLMFullResponseStartFrame
+
+        await summarizer.process_frame(LLMFullResponseStartFrame())
+
+        self.assertIsNotNone(request_frame)
+        self.assertIsInstance(request_frame, LLMContextSummaryRequestFrame)
+
+        await summarizer.cleanup()
+
 
 class TestLLMSpecificMessageHandling(unittest.TestCase):
     """Tests that LLMSpecificMessage objects are correctly skipped in summarization."""

tests/test_llm_context_summarizer.py

@@ -14,7 +14,10 @@ from pipecat.frames.frames import (
     LLMFullResponseStartFrame,
 )
 from pipecat.processors.aggregators.llm_context import LLMContext
-from pipecat.processors.aggregators.llm_context_summarizer import LLMContextSummarizer
+from pipecat.processors.aggregators.llm_context_summarizer import (
+    LLMContextSummarizer,
+    SummaryAppliedEvent,
+)
 from pipecat.utils.asyncio.task_manager import TaskManager, TaskManagerParams
 from pipecat.utils.context.llm_context_summarization import LLMContextSummarizationConfig
 
@@ -291,6 +294,252 @@ class TestLLMContextSummarizer(unittest.IsolatedAsyncioTestCase):
 
         await summarizer.cleanup()
 
+    async def test_summary_message_role_is_user(self):
+        """Test that the summary message uses the user role."""
+        config = LLMContextSummarizationConfig(max_context_tokens=50, min_messages_after_summary=2)
+
+        summarizer = LLMContextSummarizer(context=self.context, config=config)
+        await summarizer.setup(self.task_manager)
+
+        # Add messages and trigger summarization
+        for i in range(10):
+            self.context.add_message({"role": "user", "content": "Test message."})
+
+        request_frame = None
+
+        @summarizer.event_handler("on_request_summarization")
+        async def on_request_summarization(summarizer, frame):
+            nonlocal request_frame
+            request_frame = frame
+
+        await summarizer.process_frame(LLMFullResponseStartFrame())
+        self.assertIsNotNone(request_frame)
+
+        # Simulate receiving a summary result
+        summary_result = LLMContextSummaryResultFrame(
+            request_id=request_frame.request_id,
+            summary="This is a test summary.",
+            last_summarized_index=5,
+        )
+        await summarizer.process_frame(summary_result)
+
+        # Find the summary message and verify its role is "user"
+        summary_msg = next(
+            (msg for msg in self.context.messages if "summary" in msg.get("content", "").lower()),
+            None,
+        )
+        self.assertIsNotNone(summary_msg)
+        self.assertEqual(summary_msg["role"], "user")
+
+        await summarizer.cleanup()
+
+    async def test_summary_message_default_template(self):
+        """Test that the default summary_message_template is used."""
+        config = LLMContextSummarizationConfig(max_context_tokens=50, min_messages_after_summary=2)
+
+        summarizer = LLMContextSummarizer(context=self.context, config=config)
+        await summarizer.setup(self.task_manager)
+
+        for i in range(10):
+            self.context.add_message({"role": "user", "content": "Test message."})
+
+        request_frame = None
+
+        @summarizer.event_handler("on_request_summarization")
+        async def on_request_summarization(summarizer, frame):
+            nonlocal request_frame
+            request_frame = frame
+
+        await summarizer.process_frame(LLMFullResponseStartFrame())
+
+        summary_result = LLMContextSummaryResultFrame(
+            request_id=request_frame.request_id,
+            summary="Key facts from conversation.",
+            last_summarized_index=5,
+        )
+        await summarizer.process_frame(summary_result)
+
+        # Default template wraps with "Conversation summary: {summary}"
+        summary_msg = next(
+            (
+                msg
+                for msg in self.context.messages
+                if "Conversation summary:" in msg.get("content", "")
+            ),
+            None,
+        )
+        self.assertIsNotNone(summary_msg)
+        self.assertEqual(
+            summary_msg["content"], "Conversation summary: Key facts from conversation."
+        )
+
+        await summarizer.cleanup()
+
+    async def test_summary_message_custom_template(self):
+        """Test that a custom summary_message_template is applied."""
+        config = LLMContextSummarizationConfig(
+            max_context_tokens=50,
+            min_messages_after_summary=2,
+            summary_message_template="<context_summary>\n{summary}\n</context_summary>",
+        )
+
+        summarizer = LLMContextSummarizer(context=self.context, config=config)
+        await summarizer.setup(self.task_manager)
+
+        for i in range(10):
+            self.context.add_message({"role": "user", "content": "Test message."})
+
+        request_frame = None
+
+        @summarizer.event_handler("on_request_summarization")
+        async def on_request_summarization(summarizer, frame):
+            nonlocal request_frame
+            request_frame = frame
+
+        await summarizer.process_frame(LLMFullResponseStartFrame())
+
+        summary_result = LLMContextSummaryResultFrame(
+            request_id=request_frame.request_id,
+            summary="Key facts from conversation.",
+            last_summarized_index=5,
+        )
+        await summarizer.process_frame(summary_result)
+
+        # Custom template wraps with XML tags
+        summary_msg = next(
+            (msg for msg in self.context.messages if "<context_summary>" in msg.get("content", "")),
+            None,
+        )
+        self.assertIsNotNone(summary_msg)
+        self.assertEqual(
+            summary_msg["content"],
+            "<context_summary>\nKey facts from conversation.\n</context_summary>",
+        )
+
+        await summarizer.cleanup()
+
+    async def test_on_summary_applied_event(self):
+        """Test that on_summary_applied event fires with correct data."""
+        config = LLMContextSummarizationConfig(max_context_tokens=50, min_messages_after_summary=2)
+
+        summarizer = LLMContextSummarizer(context=self.context, config=config)
+        await summarizer.setup(self.task_manager)
+
+        # Add messages (1 system + 10 user = 11 total)
+        for i in range(10):
+            self.context.add_message({"role": "user", "content": "Test message."})
+
+        request_frame = None
+        applied_event = None
+
+        @summarizer.event_handler("on_request_summarization")
+        async def on_request_summarization(summarizer, frame):
+            nonlocal request_frame
+            request_frame = frame
+
+        @summarizer.event_handler("on_summary_applied")
+        async def on_summary_applied(summarizer, event):
+            nonlocal applied_event
+            applied_event = event
+
+        original_count = len(self.context.messages)  # 11
+        await summarizer.process_frame(LLMFullResponseStartFrame())
+
+        # Summarize up to index 7 (system=0, user1..user7), keep last 3 (user8, user9, user10)
+        summary_result = LLMContextSummaryResultFrame(
+            request_id=request_frame.request_id,
+            summary="Test summary.",
+            last_summarized_index=7,
+        )
+        await summarizer.process_frame(summary_result)
+
+        # Allow async event handler to complete
+        await asyncio.sleep(0.05)
+
+        # Verify event was fired
+        self.assertIsNotNone(applied_event)
+        self.assertIsInstance(applied_event, SummaryAppliedEvent)
+        self.assertEqual(applied_event.original_message_count, original_count)
+
+        # After summarization: system + summary + 3 recent = 5
+        self.assertEqual(applied_event.new_message_count, 5)
+
+        # Summarized messages: indices 1-7 = 7 messages (excluding system at index 0)
+        self.assertEqual(applied_event.summarized_message_count, 7)
+
+        # Preserved: system (1) + recent messages after index 7 (3) = 4
+        self.assertEqual(applied_event.preserved_message_count, 4)
+
+        await summarizer.cleanup()
+
+    async def test_on_summary_applied_not_fired_on_error(self):
+        """Test that on_summary_applied event is NOT fired when summarization fails."""
+        config = LLMContextSummarizationConfig(max_context_tokens=50, min_messages_after_summary=2)
+
+        summarizer = LLMContextSummarizer(context=self.context, config=config)
+        await summarizer.setup(self.task_manager)
+
+        for i in range(10):
+            self.context.add_message({"role": "user", "content": "Test message."})
+
+        request_frame = None
+        applied_event = None
+
+        @summarizer.event_handler("on_request_summarization")
+        async def on_request_summarization(summarizer, frame):
+            nonlocal request_frame
+            request_frame = frame
+
+        @summarizer.event_handler("on_summary_applied")
+        async def on_summary_applied(summarizer, event):
+            nonlocal applied_event
+            applied_event = event
+
+        await summarizer.process_frame(LLMFullResponseStartFrame())
+
+        # Send a result with an error
+        error_result = LLMContextSummaryResultFrame(
+            request_id=request_frame.request_id,
+            summary="",
+            last_summarized_index=-1,
+            error="Summarization timed out",
+        )
+        await summarizer.process_frame(error_result)
+
+        await asyncio.sleep(0.05)
+
+        # Event should NOT have fired
+        self.assertIsNone(applied_event)
+
+        await summarizer.cleanup()
+
+    async def test_request_frame_includes_timeout(self):
+        """Test that the request frame includes the configured summarization_timeout."""
+        config = LLMContextSummarizationConfig(
+            max_context_tokens=50,
+            summarization_timeout=60.0,
+        )
+
+        summarizer = LLMContextSummarizer(context=self.context, config=config)
+        await summarizer.setup(self.task_manager)
+
+        request_frame = None
+
+        @summarizer.event_handler("on_request_summarization")
+        async def on_request_summarization(summarizer, frame):
+            nonlocal request_frame
+            request_frame = frame
+
+        for i in range(10):
+            self.context.add_message({"role": "user", "content": "Test message to add tokens."})
+
+        await summarizer.process_frame(LLMFullResponseStartFrame())
+
+        self.assertIsNotNone(request_frame)
+        self.assertEqual(request_frame.summarization_timeout, 60.0)
+
+        await summarizer.cleanup()
+
 
 if __name__ == "__main__":
     unittest.main()