Add configurable summary_message_template to LLMContextSummarizationConfig

Allows applications to customize how the summary is wrapped when
  injected into context (e.g., XML tags, custom delimiters) so system
  prompts can distinguish summaries from live conversation.

src/pipecat/processors/aggregators/llm_context_summarizer.py

@@ -306,8 +306,10 @@ class LLMContextSummarizer(BaseObject):
         # Get recent messages to keep
         recent_messages = messages[last_summarized_index + 1 :]
 
-        # Create summary message as an user message
-        summary_message = {"role": "user", "content": f"Conversation summary: {summary}"}
+        # Create summary message as a user message (the summary is context
+        # 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 = []

src/pipecat/utils/context/llm_context_summarization.py

@@ -73,6 +73,11 @@ 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.
     """
 
     max_context_tokens: int = 8000
@@ -80,6 +85,7 @@ 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}"
 
     def __post_init__(self):
         """Validate configuration parameters."""