Filter Incomplete User Turns

Use LLM-based detection to suppress responses when users are cut off mid-thought

Overview

Filter Incomplete Turns is an LLM-powered feature that detects when a user’s conversational turn was incomplete (they were cut off or need time to think) and suppresses the bot’s response accordingly. Instead of responding to partial input, the bot waits for the user to continue, then automatically re-engages if they remain silent.

This creates more natural conversations by:

• Preventing the bot from responding to incomplete thoughts
• Giving users time to finish speaking without interruption
• Automatically prompting users to continue after pauses

How It Works

When enabled, the LLM outputs a turn completion marker as the first character of every response:

Marker	Meaning	Bot Behavior
✓	Complete - User finished their thought	Respond normally
○	Incomplete Short - User was cut off mid-sentence	Suppress response, wait 5s, then prompt
◐	Incomplete Long - User needs time to think	Suppress response, wait 10s, then prompt

The system automatically:

1. Injects turn completion instructions into the LLM’s system prompt
2. Detects markers in the LLM’s streaming response
3. Suppresses bot speech for incomplete turns
4. Starts a timeout based on the incomplete type
5. Re-prompts the LLM when the timeout expires

Configuration

Enable the feature via LLMUserAggregatorParams when creating an LLMContextAggregatorPair:

from pipecat.processors.aggregators.llm_context import LLMContext
from pipecat.processors.aggregators.llm_response_universal import (
    LLMContextAggregatorPair,
    LLMUserAggregatorParams,
)

context = LLMContext(messages)
user_aggregator, assistant_aggregator = LLMContextAggregatorPair(
    context,
    user_params=LLMUserAggregatorParams(
        filter_incomplete_user_turns=True,
    ),
)

LLMUserAggregatorParams

filter_incomplete_user_turns · bool · default: "False"

Enable LLM-based turn completion detection. When True, the system automatically appends turn completion instructions to the LLM’s system_instruction and configures the LLM service to process turn markers.

user_turn_completion_config · UserTurnCompletionConfig · default: "None"

Optional configuration object for customizing turn completion behavior. If not provided, default values are used.

UserTurnCompletionConfig

Use UserTurnCompletionConfig to customize timeouts, prompts, and instructions:

from pipecat.turns.user_turn_completion_mixin import UserTurnCompletionConfig

user_aggregator, assistant_aggregator = LLMContextAggregatorPair(
    context,
    user_params=LLMUserAggregatorParams(
        filter_incomplete_user_turns=True,
        user_turn_completion_config=UserTurnCompletionConfig(
            incomplete_short_timeout=5.0,
            incomplete_long_timeout=10.0,
            incomplete_short_prompt="Custom prompt for short pauses...",
            incomplete_long_prompt="Custom prompt for long pauses...",
            instructions="Custom turn completion instructions...",
        ),
    ),
)

Parameters

incomplete_short_timeout · float · default: "5.0"

Seconds to wait after detecting ○ (incomplete short) before re-prompting the LLM. Use shorter values for more responsive re-engagement.

incomplete_long_timeout · float · default: "10.0"

Seconds to wait after detecting ◐ (incomplete long) before re-prompting the LLM. Use longer values to give users more time to think.

incomplete_short_prompt · str · default: "..."

System prompt sent to the LLM when the short timeout expires. Should instruct the LLM to generate a brief, natural prompt encouraging the user to continue.

incomplete_long_prompt · str · default: "..."

System prompt sent to the LLM when the long timeout expires. Should instruct the LLM to generate a friendly check-in message.

instructions · str · default: "..."

Complete turn completion instructions appended to the system prompt. Override this to customize how the LLM determines turn completeness.

Markers Explained

Complete (✓)

The user has provided enough information for a meaningful response:

User: "I'd go to Japan because I love the culture and food."
LLM: "✓ Japan is a wonderful choice! The blend of ancient traditions..."

The ✓ marker tells the system to push the response normally. The marker itself is not spoken (marked with skip_tts).

Incomplete Short (○)

The user was cut off mid-sentence and will likely continue soon:

User: "I'd go to Japan because I love"
LLM: "○"

The ○ marker suppresses the bot’s response entirely. After 5 seconds (configurable), the LLM is prompted to re-engage with something like “Go ahead, I’m listening.”

Incomplete Long (◐)

The user needs more time to think or explicitly asked for time:

User: "That's a good question. Let me think..."
LLM: "◐"

The ◐ marker also suppresses the response, but waits 15 seconds (configurable) before prompting. This handles cases like:

• “Hold on a second”
• “Let me think about that”
• “Hmm, that’s interesting…”

Usage Examples

Basic Usage

Enable turn completion with default settings:

from pipecat.processors.aggregators.llm_context import LLMContext
from pipecat.processors.aggregators.llm_response_universal import (
    LLMContextAggregatorPair,
    LLMUserAggregatorParams,
)

messages = [
    {
        "role": "system",
        "content": "You are a helpful assistant...",
    }
]

context = LLMContext(messages)
user_aggregator, assistant_aggregator = LLMContextAggregatorPair(
    context,
    user_params=LLMUserAggregatorParams(
        filter_incomplete_user_turns=True,
    ),
)

You don’t need to modify your system prompt. Turn completion instructions are automatically appended when filter_incomplete_user_turns is enabled.

Custom Timeouts

Adjust timeouts for your use case:

from pipecat.turns.user_turn_completion_mixin import UserTurnCompletionConfig

user_aggregator, assistant_aggregator = LLMContextAggregatorPair(
    context,
    user_params=LLMUserAggregatorParams(
        filter_incomplete_user_turns=True,
        user_turn_completion_config=UserTurnCompletionConfig(
            incomplete_short_timeout=3.0,  # More responsive
            incomplete_long_timeout=20.0,  # More patient
        ),
    ),
)

Custom Prompts

Customize what the LLM says when re-engaging:

user_aggregator, assistant_aggregator = LLMContextAggregatorPair(
    context,
    user_params=LLMUserAggregatorParams(
        filter_incomplete_user_turns=True,
        user_turn_completion_config=UserTurnCompletionConfig(
            incomplete_short_prompt="""The user paused briefly.
Generate a contextual prompt to encourage them to continue.
Respond with ✓ followed by your message.""",
            incomplete_long_prompt="""The user has been quiet for a while.
Generate a friendly check-in.
Respond with ✓ followed by your message.""",
        ),
    ),
)

Custom prompts must instruct the LLM to respond with ✓ followed by the message. This ensures the re-engagement message is spoken normally.

With Smart Turn Detection

Combine with smart turn detection for better end-of-turn detection:

from pipecat.audio.turn.smart_turn.local_smart_turn_v3 import LocalSmartTurnAnalyzerV3
from pipecat.turns.user_stop import TurnAnalyzerUserTurnStopStrategy
from pipecat.turns.user_turn_strategies import UserTurnStrategies

user_aggregator, assistant_aggregator = LLMContextAggregatorPair(
    context,
    user_params=LLMUserAggregatorParams(
        user_turn_strategies=UserTurnStrategies(
            stop=[
                TurnAnalyzerUserTurnStopStrategy(
                    turn_analyzer=LocalSmartTurnAnalyzerV3()
                )
            ]
        ),
        filter_incomplete_user_turns=True,
    ),
)

Smart turn detection helps determine when the user stops speaking, while turn completion filtering determines whether to respond. They work well together for natural conversations.

Transcripts

Turn completion markers are automatically stripped from assistant transcripts emitted via the on_assistant_turn_stopped event. Your transcript handlers will receive clean text without markers:

@assistant_aggregator.event_handler("on_assistant_turn_stopped")
async def on_assistant_turn_stopped(aggregator, message: AssistantTurnStoppedMessage):
    # message.content will be "Japan is a wonderful choice!"
    # NOT "✓ Japan is a wonderful choice!"
    print(f"Assistant: {message.content}")

Supported LLM Services

Turn completion detection works with any LLM service that inherits from LLMService:

• OpenAI (OpenAILLMService)
• Anthropic (AnthropicLLMService)
• Google Gemini (GoogleLLMService)
• AWS Bedrock (AWSLLMService)
• And other compatible services

Graceful Degradation

If the LLM fails to output a turn marker:

1. The system logs a warning indicating markers were expected but not found
2. The buffered text is pushed normally to avoid losing the response
3. The conversation continues without interruption

This ensures the feature doesn’t break conversations if the LLM occasionally disobeys instructions.

Related

• User Turn Strategies - Configure turn detection
• Smart Turn Detection - AI-powered end-of-turn detection
• Transcriptions - Working with conversation transcripts