deer-flow/backend/src/tools/builtins/task_tool.py

"""Task tool for delegating work to subagents."""

import logging
import time
import uuid
from typing import Annotated, Literal

from langchain.tools import InjectedToolCallId, ToolRuntime, tool
from langgraph.config import get_stream_writer
from langgraph.typing import ContextT

from src.agents.thread_state import ThreadState
from src.subagents import SubagentExecutor, get_subagent_config
from src.subagents.executor import MAX_CONCURRENT_SUBAGENTS, SubagentStatus, count_active_tasks_by_trace, get_background_task_result

logger = logging.getLogger(__name__)


@tool("task", parse_docstring=True)
def task_tool(
    runtime: ToolRuntime[ContextT, ThreadState],
    description: str,
    prompt: str,
    subagent_type: Literal["general-purpose", "bash"],
    tool_call_id: Annotated[str, InjectedToolCallId],
    max_turns: int | None = None,
) -> str:
    """Delegate a task to a specialized subagent that runs in its own context.

    Subagents help you:
    - Preserve context by keeping exploration and implementation separate
    - Handle complex multi-step tasks autonomously
    - Execute commands or operations in isolated contexts

    Available subagent types:
    - **general-purpose**: A capable agent for complex, multi-step tasks that require
      both exploration and action. Use when the task requires complex reasoning,
      multiple dependent steps, or would benefit from isolated context.
    - **bash**: Command execution specialist for running bash commands. Use for
      git operations, build processes, or when command output would be verbose.

    When to use this tool:
    - Complex tasks requiring multiple steps or tools
    - Tasks that produce verbose output
    - When you want to isolate context from the main conversation
    - Parallel research or exploration tasks

    When NOT to use this tool:
    - Simple, single-step operations (use tools directly)
    - Tasks requiring user interaction or clarification

    Args:
        description: A short (3-5 word) description of the task for logging/display. ALWAYS PROVIDE THIS PARAMETER FIRST.
        prompt: The task description for the subagent. Be specific and clear about what needs to be done. ALWAYS PROVIDE THIS PARAMETER SECOND.
        subagent_type: The type of subagent to use. ALWAYS PROVIDE THIS PARAMETER THIRD.
        max_turns: Optional maximum number of agent turns. Defaults to subagent's configured max.
    """
    # Get subagent configuration
    config = get_subagent_config(subagent_type)
    if config is None:
        return f"Error: Unknown subagent type '{subagent_type}'. Available: general-purpose, bash"

    # Override max_turns if specified
    if max_turns is not None:
        # Create a copy with updated max_turns
        from dataclasses import replace

        config = replace(config, max_turns=max_turns)

    # Extract parent context from runtime
    sandbox_state = None
    thread_data = None
    thread_id = None
    parent_model = None
    trace_id = None

    if runtime is not None:
        sandbox_state = runtime.state.get("sandbox")
        thread_data = runtime.state.get("thread_data")
        thread_id = runtime.context.get("thread_id")

        # Try to get parent model from configurable
        metadata = runtime.config.get("metadata", {})
        parent_model = metadata.get("model_name")

        # Get or generate trace_id for distributed tracing
        trace_id = metadata.get("trace_id") or str(uuid.uuid4())[:8]

    # Check sub-agent limit before creating a new one
    if trace_id and count_active_tasks_by_trace(trace_id) >= MAX_CONCURRENT_SUBAGENTS:
        logger.warning(f"[trace={trace_id}] Sub-agent limit reached ({MAX_CONCURRENT_SUBAGENTS}). Rejecting new task: {description}")
        return f"Error: Maximum number of concurrent sub-agents ({MAX_CONCURRENT_SUBAGENTS}) reached. Please wait for existing tasks to complete before launching new ones."

    # Get available tools (excluding task tool to prevent nesting)
    # Lazy import to avoid circular dependency
    from src.tools import get_available_tools

    # Subagents should not have subagent tools enabled (prevent recursive nesting)
    tools = get_available_tools(model_name=parent_model, subagent_enabled=False)

    # Create executor
    executor = SubagentExecutor(
        config=config,
        tools=tools,
        parent_model=parent_model,
        sandbox_state=sandbox_state,
        thread_data=thread_data,
        thread_id=thread_id,
        trace_id=trace_id,
    )

    # Start background execution (always async to prevent blocking)
    # Use tool_call_id as task_id for better traceability
    task_id = executor.execute_async(prompt, task_id=tool_call_id)
    logger.info(f"[trace={trace_id}] Started background task {task_id}, polling for completion...")

    # Poll for task completion in backend (removes need for LLM to poll)
    poll_count = 0
    last_status = None
    last_message_count = 0  # Track how many AI messages we've already sent

    writer = get_stream_writer()
    # Send Task Started message'
    writer({"type": "task_started", "task_id": task_id, "description": description})


    while True:
        result = get_background_task_result(task_id)

        if result is None:
            logger.error(f"[trace={trace_id}] Task {task_id} not found in background tasks")
            writer({"type": "task_failed", "task_id": task_id, "error": "Task disappeared from background tasks"})
            return f"Error: Task {task_id} disappeared from background tasks"

        # Log status changes for debugging
        if result.status != last_status:
            logger.info(f"[trace={trace_id}] Task {task_id} status: {result.status.value}")
            last_status = result.status

        # Check for new AI messages and send task_running events
        current_message_count = len(result.ai_messages)
        if current_message_count > last_message_count:
            # Send task_running event for each new message
            for i in range(last_message_count, current_message_count):
                message = result.ai_messages[i]
                writer({
                    "type": "task_running",
                    "task_id": task_id,
                    "message": message,
                    "message_index": i + 1,  # 1-based index for display
                    "total_messages": current_message_count
                })
                logger.info(f"[trace={trace_id}] Task {task_id} sent message #{i + 1}/{current_message_count}")
            last_message_count = current_message_count

        # Check if task completed, failed, or timed out
        if result.status == SubagentStatus.COMPLETED:
            writer({"type": "task_completed", "task_id": task_id, "result": result.result})
            logger.info(f"[trace={trace_id}] Task {task_id} completed after {poll_count} polls")
            return f"Task Succeeded. Result: {result.result}"
        elif result.status == SubagentStatus.FAILED:
            writer({"type": "task_failed", "task_id": task_id, "error": result.error})
            logger.error(f"[trace={trace_id}] Task {task_id} failed: {result.error}")
            return f"Task failed. Error: {result.error}"
        elif result.status == SubagentStatus.TIMED_OUT:
            writer({"type": "task_timed_out", "task_id": task_id, "error": result.error})
            logger.warning(f"[trace={trace_id}] Task {task_id} timed out: {result.error}")
            return f"Task timed out. Error: {result.error}"

        # Still running, wait before next poll
        time.sleep(5)  # Poll every 5 seconds
        poll_count += 1

        # Polling timeout as a safety net (in case thread pool timeout doesn't work)
        # Set to 16 minutes (longer than the default 15-minute thread pool timeout)
        # This catches edge cases where the background task gets stuck
        if poll_count > 192:  # 192 * 5s = 16 minutes
            logger.error(f"[trace={trace_id}] Task {task_id} polling timed out after {poll_count} polls (should have been caught by thread pool timeout)")
            writer({"type": "task_timed_out", "task_id": task_id})
            return f"Task polling timed out after 16 minutes. This may indicate the background task is stuck. Status: {result.status.value}"