deer-flow/src/graph/nodes.py

# Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
# SPDX-License-Identifier: MIT

import json
import logging
import os
from functools import partial
from typing import Annotated, Literal

from langchain_core.messages import AIMessage, HumanMessage, ToolMessage
from langchain_core.runnables import RunnableConfig
from langchain_core.tools import tool
from langchain_mcp_adapters.client import MultiServerMCPClient
from langgraph.types import Command, interrupt

from src.agents import create_agent
from src.config.agents import AGENT_LLM_MAP
from src.config.configuration import Configuration
from src.llms.llm import get_llm_by_type, get_llm_token_limit_by_type
from src.prompts.planner_model import Plan
from src.prompts.template import apply_prompt_template
from src.tools import (
    crawl_tool,
    get_retriever_tool,
    get_web_search_tool,
    python_repl_tool,
)
from src.tools.search import LoggedTavilySearch
from src.utils.context_manager import ContextManager, validate_message_content
from src.utils.json_utils import repair_json_output, sanitize_tool_response

from ..config import SELECTED_SEARCH_ENGINE, SearchEngine
from .types import State
from .utils import (
    build_clarified_topic_from_history,
    get_message_content,
    is_user_message,
    reconstruct_clarification_history,
)

logger = logging.getLogger(__name__)


@tool
def handoff_to_planner(
    research_topic: Annotated[str, "The topic of the research task to be handed off."],
    locale: Annotated[str, "The user's detected language locale (e.g., en-US, zh-CN)."],
):
    """Handoff to planner agent to do plan."""
    # This tool is not returning anything: we're just using it
    # as a way for LLM to signal that it needs to hand off to planner agent
    return


@tool
def handoff_after_clarification(
    locale: Annotated[str, "The user's detected language locale (e.g., en-US, zh-CN)."],
    research_topic: Annotated[
        str, "The clarified research topic based on all clarification rounds."
    ],
):
    """Handoff to planner after clarification rounds are complete. Pass all clarification history to planner for analysis."""
    return


def needs_clarification(state: dict) -> bool:
    """
    Check if clarification is needed based on current state.
    Centralized logic for determining when to continue clarification.
    """
    if not state.get("enable_clarification", False):
        return False

    clarification_rounds = state.get("clarification_rounds", 0)
    is_clarification_complete = state.get("is_clarification_complete", False)
    max_clarification_rounds = state.get("max_clarification_rounds", 3)

    # Need clarification if: enabled + has rounds + not complete + not exceeded max
    # Use <= because after asking the Nth question, we still need to wait for the Nth answer
    return (
        clarification_rounds > 0
        and not is_clarification_complete
        and clarification_rounds <= max_clarification_rounds
    )


def validate_and_fix_plan(plan: dict, enforce_web_search: bool = False) -> dict:
    """
    Validate and fix a plan to ensure it meets requirements.

    Args:
        plan: The plan dict to validate
        enforce_web_search: If True, ensure at least one step has need_search=true

    Returns:
        The validated/fixed plan dict
    """
    if not isinstance(plan, dict):
        return plan

    steps = plan.get("steps", [])

    # ============================================================
    # SECTION 1: Repair missing step_type fields (Issue #650 fix)
    # ============================================================
    for idx, step in enumerate(steps):
        if not isinstance(step, dict):
            continue
        
        # Check if step_type is missing or empty
        if "step_type" not in step or not step.get("step_type"):
            # Infer step_type based on need_search value
            inferred_type = "research" if step.get("need_search", False) else "processing"
            step["step_type"] = inferred_type
            logger.info(
                f"Repaired missing step_type for step {idx} ({step.get('title', 'Untitled')}): "
                f"inferred as '{inferred_type}' based on need_search={step.get('need_search', False)}"
            )

    # ============================================================
    # SECTION 2: Enforce web search requirements
    # ============================================================
    if enforce_web_search:
        # Check if any step has need_search=true
        has_search_step = any(step.get("need_search", False) for step in steps)

        if not has_search_step and steps:
            # Ensure first research step has web search enabled
            for idx, step in enumerate(steps):
                if step.get("step_type") == "research":
                    step["need_search"] = True
                    logger.info(f"Enforced web search on research step at index {idx}")
                    break
            else:
                # Fallback: If no research step exists, convert the first step to a research step with web search enabled.
                # This ensures that at least one step will perform a web search as required.
                steps[0]["step_type"] = "research"
                steps[0]["need_search"] = True
                logger.info(
                    "Converted first step to research with web search enforcement"
                )
        elif not has_search_step and not steps:
            # Add a default research step if no steps exist
            logger.warning("Plan has no steps. Adding default research step.")
            plan["steps"] = [
                {
                    "need_search": True,
                    "title": "Initial Research",
                    "description": "Gather information about the topic",
                    "step_type": "research",
                }
            ]

    return plan


def background_investigation_node(state: State, config: RunnableConfig):
    logger.info("background investigation node is running.")
    configurable = Configuration.from_runnable_config(config)
    query = state.get("clarified_research_topic") or state.get("research_topic")
    background_investigation_results = []
    
    if SELECTED_SEARCH_ENGINE == SearchEngine.TAVILY.value:
        searched_content = LoggedTavilySearch(
            max_results=configurable.max_search_results
        ).invoke(query)
        # check if the searched_content is a tuple, then we need to unpack it
        if isinstance(searched_content, tuple):
            searched_content = searched_content[0]
        
        # Handle string JSON response (new format from fixed Tavily tool)
        if isinstance(searched_content, str):
            try:
                parsed = json.loads(searched_content)
                if isinstance(parsed, dict) and "error" in parsed:
                    logger.error(f"Tavily search error: {parsed['error']}")
                    background_investigation_results = []
                elif isinstance(parsed, list):
                    background_investigation_results = [
                        f"## {elem.get('title', 'Untitled')}\n\n{elem.get('content', 'No content')}" 
                        for elem in parsed
                    ]
                else:
                    logger.error(f"Unexpected Tavily response format: {searched_content}")
                    background_investigation_results = []
            except json.JSONDecodeError:
                logger.error(f"Failed to parse Tavily response as JSON: {searched_content}")
                background_investigation_results = []
        # Handle legacy list format
        elif isinstance(searched_content, list):
            background_investigation_results = [
                f"## {elem['title']}\n\n{elem['content']}" for elem in searched_content
            ]
            return {
                "background_investigation_results": "\n\n".join(
                    background_investigation_results
                )
            }
        else:
            logger.error(
                f"Tavily search returned malformed response: {searched_content}"
            )
            background_investigation_results = []
    else:
        background_investigation_results = get_web_search_tool(
            configurable.max_search_results
        ).invoke(query)
    
    return {
        "background_investigation_results": json.dumps(
            background_investigation_results, ensure_ascii=False
        )
    }


def planner_node(
    state: State, config: RunnableConfig
) -> Command[Literal["human_feedback", "reporter"]]:
    """Planner node that generate the full plan."""
    logger.info("Planner generating full plan")
    configurable = Configuration.from_runnable_config(config)
    plan_iterations = state["plan_iterations"] if state.get("plan_iterations", 0) else 0

    # For clarification feature: use the clarified research topic (complete history)
    if state.get("enable_clarification", False) and state.get(
        "clarified_research_topic"
    ):
        # Modify state to use clarified research topic instead of full conversation
        modified_state = state.copy()
        modified_state["messages"] = [
            {"role": "user", "content": state["clarified_research_topic"]}
        ]
        modified_state["research_topic"] = state["clarified_research_topic"]
        messages = apply_prompt_template("planner", modified_state, configurable, state.get("locale", "en-US"))

        logger.info(
            f"Clarification mode: Using clarified research topic: {state['clarified_research_topic']}"
        )
    else:
        # Normal mode: use full conversation history
        messages = apply_prompt_template("planner", state, configurable, state.get("locale", "en-US"))

    if state.get("enable_background_investigation") and state.get(
        "background_investigation_results"
    ):
        messages += [
            {
                "role": "user",
                "content": (
                    "background investigation results of user query:\n"
                    + state["background_investigation_results"]
                    + "\n"
                ),
            }
        ]

    if configurable.enable_deep_thinking:
        llm = get_llm_by_type("reasoning")
    elif AGENT_LLM_MAP["planner"] == "basic":
        llm = get_llm_by_type("basic").with_structured_output(
            Plan,
            method="json_mode",
        )
    else:
        llm = get_llm_by_type(AGENT_LLM_MAP["planner"])

    # if the plan iterations is greater than the max plan iterations, return the reporter node
    if plan_iterations >= configurable.max_plan_iterations:
        return Command(goto="reporter")

    full_response = ""
    if AGENT_LLM_MAP["planner"] == "basic" and not configurable.enable_deep_thinking:
        response = llm.invoke(messages)
        full_response = response.model_dump_json(indent=4, exclude_none=True)
    else:
        response = llm.stream(messages)
        for chunk in response:
            full_response += chunk.content
    logger.debug(f"Current state messages: {state['messages']}")
    logger.info(f"Planner response: {full_response}")

    try:
        curr_plan = json.loads(repair_json_output(full_response))
    except json.JSONDecodeError:
        logger.warning("Planner response is not a valid JSON")
        if plan_iterations > 0:
            return Command(goto="reporter")
        else:
            return Command(goto="__end__")

    # Validate and fix plan to ensure web search requirements are met
    if isinstance(curr_plan, dict):
        curr_plan = validate_and_fix_plan(curr_plan, configurable.enforce_web_search)

    if isinstance(curr_plan, dict) and curr_plan.get("has_enough_context"):
        logger.info("Planner response has enough context.")
        new_plan = Plan.model_validate(curr_plan)
        return Command(
            update={
                "messages": [AIMessage(content=full_response, name="planner")],
                "current_plan": new_plan,
            },
            goto="reporter",
        )
    return Command(
        update={
            "messages": [AIMessage(content=full_response, name="planner")],
            "current_plan": full_response,
        },
        goto="human_feedback",
    )


def human_feedback_node(
    state: State, config: RunnableConfig
) -> Command[Literal["planner", "research_team", "reporter", "__end__"]]:
    current_plan = state.get("current_plan", "")
    # check if the plan is auto accepted
    auto_accepted_plan = state.get("auto_accepted_plan", False)
    if not auto_accepted_plan:
        feedback = interrupt("Please Review the Plan.")

        # Handle None or empty feedback
        if not feedback:
            logger.warning(f"Received empty or None feedback: {feedback}. Returning to planner for new plan.")
            return Command(goto="planner")

        # Normalize feedback string
        feedback_normalized = str(feedback).strip().upper()

        # if the feedback is not accepted, return the planner node
        if feedback_normalized.startswith("[EDIT_PLAN]"):
            logger.info(f"Plan edit requested by user: {feedback}")
            return Command(
                update={
                    "messages": [
                        HumanMessage(content=feedback, name="feedback"),
                    ],
                },
                goto="planner",
            )
        elif feedback_normalized.startswith("[ACCEPTED]"):
            logger.info("Plan is accepted by user.")
        else:
            logger.warning(f"Unsupported feedback format: {feedback}. Please use '[ACCEPTED]' to accept or '[EDIT_PLAN]' to edit.")
            return Command(goto="planner")

    # if the plan is accepted, run the following node
    plan_iterations = state["plan_iterations"] if state.get("plan_iterations", 0) else 0
    goto = "research_team"
    try:
        current_plan = repair_json_output(current_plan)
        # increment the plan iterations
        plan_iterations += 1
        # parse the plan
        new_plan = json.loads(current_plan)
        # Validate and fix plan to ensure web search requirements are met
        configurable = Configuration.from_runnable_config(config)
        new_plan = validate_and_fix_plan(new_plan, configurable.enforce_web_search)
    except json.JSONDecodeError:
        logger.warning("Planner response is not a valid JSON")
        if plan_iterations > 1:  # the plan_iterations is increased before this check
            return Command(goto="reporter")
        else:
            return Command(goto="__end__")

    return Command(
        update={
            "current_plan": Plan.model_validate(new_plan),
            "plan_iterations": plan_iterations,
            "locale": new_plan["locale"],
        },
        goto=goto,
    )


def coordinator_node(
    state: State, config: RunnableConfig
) -> Command[Literal["planner", "background_investigator", "coordinator", "__end__"]]:
    """Coordinator node that communicate with customers and handle clarification."""
    logger.info("Coordinator talking.")
    configurable = Configuration.from_runnable_config(config)

    # Check if clarification is enabled
    enable_clarification = state.get("enable_clarification", False)
    initial_topic = state.get("research_topic", "")
    clarified_topic = initial_topic
    # ============================================================
    # BRANCH 1: Clarification DISABLED (Legacy Mode)
    # ============================================================
    if not enable_clarification:
        # Use normal prompt with explicit instruction to skip clarification
        messages = apply_prompt_template("coordinator", state, locale=state.get("locale", "en-US"))
        messages.append(
            {
                "role": "system",
                "content": "CRITICAL: Clarification is DISABLED. You MUST immediately call handoff_to_planner tool with the user's query as-is. Do NOT ask questions or mention needing more information.",
            }
        )

        # Only bind handoff_to_planner tool
        tools = [handoff_to_planner]
        response = (
            get_llm_by_type(AGENT_LLM_MAP["coordinator"])
            .bind_tools(tools)
            .invoke(messages)
        )

        goto = "__end__"
        locale = state.get("locale", "en-US")
        research_topic = state.get("research_topic", "")

        # Process tool calls for legacy mode
        if response.tool_calls:
            try:
                for tool_call in response.tool_calls:
                    tool_name = tool_call.get("name", "")
                    tool_args = tool_call.get("args", {})

                    if tool_name == "handoff_to_planner":
                        logger.info("Handing off to planner")
                        goto = "planner"

                        # Extract locale and research_topic if provided
                        if tool_args.get("locale") and tool_args.get("research_topic"):
                            locale = tool_args.get("locale")
                            research_topic = tool_args.get("research_topic")
                        break

            except Exception as e:
                logger.error(f"Error processing tool calls: {e}")
                goto = "planner"

    # ============================================================
    # BRANCH 2: Clarification ENABLED (New Feature)
    # ============================================================
    else:
        # Load clarification state
        clarification_rounds = state.get("clarification_rounds", 0)
        clarification_history = list(state.get("clarification_history", []) or [])
        clarification_history = [item for item in clarification_history if item]
        max_clarification_rounds = state.get("max_clarification_rounds", 3)

        # Prepare the messages for the coordinator
        state_messages = list(state.get("messages", []))
        messages = apply_prompt_template("coordinator", state, locale=state.get("locale", "en-US"))

        clarification_history = reconstruct_clarification_history(
            state_messages, clarification_history, initial_topic
        )
        clarified_topic, clarification_history = build_clarified_topic_from_history(
            clarification_history
        )
        logger.debug("Clarification history rebuilt: %s", clarification_history)

        if clarification_history:
            initial_topic = clarification_history[0]
            latest_user_content = clarification_history[-1]
        else:
            latest_user_content = ""

        # Add clarification status for first round
        if clarification_rounds == 0:
            messages.append(
                {
                    "role": "system",
                    "content": "Clarification mode is ENABLED. Follow the 'Clarification Process' guidelines in your instructions.",
                }
            )

        current_response = latest_user_content or "No response"
        logger.info(
            "Clarification round %s/%s | topic: %s | current user response: %s",
            clarification_rounds,
            max_clarification_rounds,
            clarified_topic or initial_topic,
            current_response,
        )

        clarification_context = f"""Continuing clarification (round {clarification_rounds}/{max_clarification_rounds}):
            User's latest response: {current_response}
            Ask for remaining missing dimensions. Do NOT repeat questions or start new topics."""

        messages.append({"role": "system", "content": clarification_context})

        # Bind both clarification tools - let LLM choose the appropriate one
        tools = [handoff_to_planner, handoff_after_clarification]

        # Check if we've already reached max rounds
        if clarification_rounds >= max_clarification_rounds:
            # Max rounds reached - force handoff by adding system instruction
            logger.warning(
                f"Max clarification rounds ({max_clarification_rounds}) reached. Forcing handoff to planner. Using prepared clarified topic: {clarified_topic}"
            )
            # Add system instruction to force handoff - let LLM choose the right tool
            messages.append(
                {
                    "role": "system",
                    "content": f"MAX ROUNDS REACHED. You MUST call handoff_after_clarification (not handoff_to_planner) with the appropriate locale based on the user's language and research_topic='{clarified_topic}'. Do not ask any more questions.",
                }
            )

        response = (
            get_llm_by_type(AGENT_LLM_MAP["coordinator"])
            .bind_tools(tools)
            .invoke(messages)
        )
        logger.debug(f"Current state messages: {state['messages']}")

        # Initialize response processing variables
        goto = "__end__"
        locale = state.get("locale", "en-US")
        research_topic = (
            clarification_history[0]
            if clarification_history
            else state.get("research_topic", "")
        )
        if not clarified_topic:
            clarified_topic = research_topic

        # --- Process LLM response ---
        # No tool calls - LLM is asking a clarifying question
        if not response.tool_calls and response.content:
            # Check if we've reached max rounds - if so, force handoff to planner
            if clarification_rounds >= max_clarification_rounds:
                logger.warning(
                    f"Max clarification rounds ({max_clarification_rounds}) reached. "
                    "LLM didn't call handoff tool, forcing handoff to planner."
                )
                goto = "planner"
                # Continue to final section instead of early return
            else:
                # Continue clarification process
                clarification_rounds += 1
                # Do NOT add LLM response to clarification_history - only user responses
                logger.info(
                    f"Clarification response: {clarification_rounds}/{max_clarification_rounds}: {response.content}"
                )

                # Append coordinator's question to messages
                updated_messages = list(state_messages)
                if response.content:
                    updated_messages.append(
                        HumanMessage(content=response.content, name="coordinator")
                    )

                return Command(
                    update={
                        "messages": updated_messages,
                        "locale": locale,
                        "research_topic": research_topic,
                        "resources": configurable.resources,
                        "clarification_rounds": clarification_rounds,
                        "clarification_history": clarification_history,
                        "clarified_research_topic": clarified_topic,
                        "is_clarification_complete": False,
                        "goto": goto,
                        "__interrupt__": [("coordinator", response.content)],
                    },
                    goto=goto,
                )
        else:
            # LLM called a tool (handoff) or has no content - clarification complete
            if response.tool_calls:
                logger.info(
                    f"Clarification completed after {clarification_rounds} rounds. LLM called handoff tool."
                )
            else:
                logger.warning("LLM response has no content and no tool calls.")
            # goto will be set in the final section based on tool calls

    # ============================================================
    # Final: Build and return Command
    # ============================================================
    messages = list(state.get("messages", []) or [])
    if response.content:
        messages.append(HumanMessage(content=response.content, name="coordinator"))

    # Process tool calls for BOTH branches (legacy and clarification)
    if response.tool_calls:
        try:
            for tool_call in response.tool_calls:
                tool_name = tool_call.get("name", "")
                tool_args = tool_call.get("args", {})

                if tool_name in ["handoff_to_planner", "handoff_after_clarification"]:
                    logger.info("Handing off to planner")
                    goto = "planner"

                    # Extract locale if provided
                    locale = tool_args.get("locale", locale)
                    if not enable_clarification and tool_args.get("research_topic"):
                        research_topic = tool_args["research_topic"]

                    if enable_clarification:
                        logger.info(
                            "Using prepared clarified topic: %s",
                            clarified_topic or research_topic,
                        )
                    else:
                        logger.info(
                            "Using research topic for handoff: %s", research_topic
                        )
                    break

        except Exception as e:
            logger.error(f"Error processing tool calls: {e}")
            goto = "planner"
    else:
        # No tool calls detected - fallback to planner instead of ending
        logger.warning(
            "LLM didn't call any tools. This may indicate tool calling issues with the model. "
            "Falling back to planner to ensure research proceeds."
        )
        # Log full response for debugging
        logger.debug(f"Coordinator response content: {response.content}")
        logger.debug(f"Coordinator response object: {response}")
        # Fallback to planner to ensure workflow continues
        goto = "planner"

    # Apply background_investigation routing if enabled (unified logic)
    if goto == "planner" and state.get("enable_background_investigation"):
        goto = "background_investigator"

    # Set default values for state variables (in case they're not defined in legacy mode)
    if not enable_clarification:
        clarification_rounds = 0
        clarification_history = []

    clarified_research_topic_value = clarified_topic or research_topic

    # clarified_research_topic: Complete clarified topic with all clarification rounds
    return Command(
        update={
            "messages": messages,
            "locale": locale,
            "research_topic": research_topic,
            "clarified_research_topic": clarified_research_topic_value,
            "resources": configurable.resources,
            "clarification_rounds": clarification_rounds,
            "clarification_history": clarification_history,
            "is_clarification_complete": goto != "coordinator",
            "goto": goto,
        },
        goto=goto,
    )


def reporter_node(state: State, config: RunnableConfig):
    """Reporter node that write a final report."""
    logger.info("Reporter write final report")
    configurable = Configuration.from_runnable_config(config)
    current_plan = state.get("current_plan")
    input_ = {
        "messages": [
            HumanMessage(
                f"# Research Requirements\n\n## Task\n\n{current_plan.title}\n\n## Description\n\n{current_plan.thought}"
            )
        ],
        "locale": state.get("locale", "en-US"),
    }
    invoke_messages = apply_prompt_template("reporter", input_, configurable, input_.get("locale", "en-US"))
    observations = state.get("observations", [])

    # Add a reminder about the new report format, citation style, and table usage
    invoke_messages.append(
        HumanMessage(
            content="IMPORTANT: Structure your report according to the format in the prompt. Remember to include:\n\n1. Key Points - A bulleted list of the most important findings\n2. Overview - A brief introduction to the topic\n3. Detailed Analysis - Organized into logical sections\n4. Survey Note (optional) - For more comprehensive reports\n5. Key Citations - List all references at the end\n\nFor citations, DO NOT include inline citations in the text. Instead, place all citations in the 'Key Citations' section at the end using the format: `- [Source Title](URL)`. Include an empty line between each citation for better readability.\n\nPRIORITIZE USING MARKDOWN TABLES for data presentation and comparison. Use tables whenever presenting comparative data, statistics, features, or options. Structure tables with clear headers and aligned columns. Example table format:\n\n| Feature | Description | Pros | Cons |\n|---------|-------------|------|------|\n| Feature 1 | Description 1 | Pros 1 | Cons 1 |\n| Feature 2 | Description 2 | Pros 2 | Cons 2 |",
            name="system",
        )
    )

    observation_messages = []
    for observation in observations:
        observation_messages.append(
            HumanMessage(
                content=f"Below are some observations for the research task:\n\n{observation}",
                name="observation",
            )
        )

    # Context compression
    llm_token_limit = get_llm_token_limit_by_type(AGENT_LLM_MAP["reporter"])
    compressed_state = ContextManager(llm_token_limit).compress_messages(
        {"messages": observation_messages}
    )
    invoke_messages += compressed_state.get("messages", [])

    logger.debug(f"Current invoke messages: {invoke_messages}")
    response = get_llm_by_type(AGENT_LLM_MAP["reporter"]).invoke(invoke_messages)
    response_content = response.content
    logger.info(f"reporter response: {response_content}")

    return {"final_report": response_content}


def research_team_node(state: State):
    """Research team node that collaborates on tasks."""
    logger.info("Research team is collaborating on tasks.")
    pass


async def _execute_agent_step(
    state: State, agent, agent_name: str
) -> Command[Literal["research_team"]]:
    """Helper function to execute a step using the specified agent."""
    current_plan = state.get("current_plan")
    plan_title = current_plan.title
    observations = state.get("observations", [])

    # Find the first unexecuted step
    current_step = None
    completed_steps = []
    for step in current_plan.steps:
        if not step.execution_res:
            current_step = step
            break
        else:
            completed_steps.append(step)

    if not current_step:
        logger.warning("No unexecuted step found")
        return Command(goto="research_team")

    logger.info(f"Executing step: {current_step.title}, agent: {agent_name}")

    # Format completed steps information
    completed_steps_info = ""
    if completed_steps:
        completed_steps_info = "# Completed Research Steps\n\n"
        for i, step in enumerate(completed_steps):
            completed_steps_info += f"## Completed Step {i + 1}: {step.title}\n\n"
            completed_steps_info += f"<finding>\n{step.execution_res}\n</finding>\n\n"

    # Prepare the input for the agent with completed steps info
    agent_input = {
        "messages": [
            HumanMessage(
                content=f"# Research Topic\n\n{plan_title}\n\n{completed_steps_info}# Current Step\n\n## Title\n\n{current_step.title}\n\n## Description\n\n{current_step.description}\n\n## Locale\n\n{state.get('locale', 'en-US')}"
            )
        ]
    }

    # Add citation reminder for researcher agent
    if agent_name == "researcher":
        if state.get("resources"):
            resources_info = "**The user mentioned the following resource files:**\n\n"
            for resource in state.get("resources"):
                resources_info += f"- {resource.title} ({resource.description})\n"

            agent_input["messages"].append(
                HumanMessage(
                    content=resources_info
                    + "\n\n"
                    + "You MUST use the **local_search_tool** to retrieve the information from the resource files.",
                )
            )

        agent_input["messages"].append(
            HumanMessage(
                content="IMPORTANT: DO NOT include inline citations in the text. Instead, track all sources and include a References section at the end using link reference format. Include an empty line between each citation for better readability. Use this format for each reference:\n- [Source Title](URL)\n\n- [Another Source](URL)",
                name="system",
            )
        )

    # Invoke the agent
    default_recursion_limit = 25
    try:
        env_value_str = os.getenv("AGENT_RECURSION_LIMIT", str(default_recursion_limit))
        parsed_limit = int(env_value_str)

        if parsed_limit > 0:
            recursion_limit = parsed_limit
            logger.info(f"Recursion limit set to: {recursion_limit}")
        else:
            logger.warning(
                f"AGENT_RECURSION_LIMIT value '{env_value_str}' (parsed as {parsed_limit}) is not positive. "
                f"Using default value {default_recursion_limit}."
            )
            recursion_limit = default_recursion_limit
    except ValueError:
        raw_env_value = os.getenv("AGENT_RECURSION_LIMIT")
        logger.warning(
            f"Invalid AGENT_RECURSION_LIMIT value: '{raw_env_value}'. "
            f"Using default value {default_recursion_limit}."
        )
        recursion_limit = default_recursion_limit

    logger.info(f"Agent input: {agent_input}")
    
    # Validate message content before invoking agent
    try:
        validated_messages = validate_message_content(agent_input["messages"])
        agent_input["messages"] = validated_messages
    except Exception as validation_error:
        logger.error(f"Error validating agent input messages: {validation_error}")
    
    try:
        result = await agent.ainvoke(
            input=agent_input, config={"recursion_limit": recursion_limit}
        )
    except Exception as e:
        import traceback

        error_traceback = traceback.format_exc()
        error_message = f"Error executing {agent_name} agent for step '{current_step.title}': {str(e)}"
        logger.exception(error_message)
        logger.error(f"Full traceback:\n{error_traceback}")
        
        # Enhanced error diagnostics for content-related errors
        if "Field required" in str(e) and "content" in str(e):
            logger.error(f"Message content validation error detected")
            for i, msg in enumerate(agent_input.get('messages', [])):
                logger.error(f"Message {i}: type={type(msg).__name__}, "
                            f"has_content={hasattr(msg, 'content')}, "
                            f"content_type={type(msg.content).__name__ if hasattr(msg, 'content') else 'N/A'}, "
                            f"content_len={len(str(msg.content)) if hasattr(msg, 'content') and msg.content else 0}")

        detailed_error = f"[ERROR] {agent_name.capitalize()} Agent Error\n\nStep: {current_step.title}\n\nError Details:\n{str(e)}\n\nPlease check the logs for more information."
        current_step.execution_res = detailed_error

        return Command(
            update={
                "messages": [
                    HumanMessage(
                        content=detailed_error,
                        name=agent_name,
                    )
                ],
                "observations": observations + [detailed_error],
            },
            goto="research_team",
        )

    # Process the result
    response_content = result["messages"][-1].content
    
    # Sanitize response to remove extra tokens and truncate if needed
    response_content = sanitize_tool_response(str(response_content))
    
    logger.debug(f"{agent_name.capitalize()} full response: {response_content}")

    # Update the step with the execution result
    current_step.execution_res = response_content
    logger.info(f"Step '{current_step.title}' execution completed by {agent_name}")

    return Command(
        update={
            "messages": [
                HumanMessage(
                    content=response_content,
                    name=agent_name,
                )
            ],
            "observations": observations + [response_content],
        },
        goto="research_team",
    )


async def _setup_and_execute_agent_step(
    state: State,
    config: RunnableConfig,
    agent_type: str,
    default_tools: list,
) -> Command[Literal["research_team"]]:
    """Helper function to set up an agent with appropriate tools and execute a step.

    This function handles the common logic for both researcher_node and coder_node:
    1. Configures MCP servers and tools based on agent type
    2. Creates an agent with the appropriate tools or uses the default agent
    3. Executes the agent on the current step

    Args:
        state: The current state
        config: The runnable config
        agent_type: The type of agent ("researcher" or "coder")
        default_tools: The default tools to add to the agent

    Returns:
        Command to update state and go to research_team
    """
    configurable = Configuration.from_runnable_config(config)
    mcp_servers = {}
    enabled_tools = {}

    # Extract MCP server configuration for this agent type
    if configurable.mcp_settings:
        for server_name, server_config in configurable.mcp_settings["servers"].items():
            if (
                server_config["enabled_tools"]
                and agent_type in server_config["add_to_agents"]
            ):
                mcp_servers[server_name] = {
                    k: v
                    for k, v in server_config.items()
                    if k in ("transport", "command", "args", "url", "env", "headers")
                }
                for tool_name in server_config["enabled_tools"]:
                    enabled_tools[tool_name] = server_name

    # Create and execute agent with MCP tools if available
    if mcp_servers:
        client = MultiServerMCPClient(mcp_servers)
        loaded_tools = default_tools[:]
        all_tools = await client.get_tools()
        for tool in all_tools:
            if tool.name in enabled_tools:
                tool.description = (
                    f"Powered by '{enabled_tools[tool.name]}'.\n{tool.description}"
                )
                loaded_tools.append(tool)

        llm_token_limit = get_llm_token_limit_by_type(AGENT_LLM_MAP[agent_type])
        pre_model_hook = partial(ContextManager(llm_token_limit, 3).compress_messages)
        agent = create_agent(
            agent_type,
            agent_type,
            loaded_tools,
            agent_type,
            pre_model_hook,
            interrupt_before_tools=configurable.interrupt_before_tools,
        )
        return await _execute_agent_step(state, agent, agent_type)
    else:
        # Use default tools if no MCP servers are configured
        llm_token_limit = get_llm_token_limit_by_type(AGENT_LLM_MAP[agent_type])
        pre_model_hook = partial(ContextManager(llm_token_limit, 3).compress_messages)
        agent = create_agent(
            agent_type,
            agent_type,
            default_tools,
            agent_type,
            pre_model_hook,
            interrupt_before_tools=configurable.interrupt_before_tools,
        )
        return await _execute_agent_step(state, agent, agent_type)


async def researcher_node(
    state: State, config: RunnableConfig
) -> Command[Literal["research_team"]]:
    """Researcher node that do research"""
    logger.info("Researcher node is researching.")
    configurable = Configuration.from_runnable_config(config)
    tools = [get_web_search_tool(configurable.max_search_results), crawl_tool]
    retriever_tool = get_retriever_tool(state.get("resources", []))
    if retriever_tool:
        tools.insert(0, retriever_tool)
    logger.info(f"Researcher tools: {tools}")
    return await _setup_and_execute_agent_step(
        state,
        config,
        "researcher",
        tools,
    )


async def coder_node(
    state: State, config: RunnableConfig
) -> Command[Literal["research_team"]]:
    """Coder node that do code analysis."""
    logger.info("Coder node is coding.")
    return await _setup_and_execute_agent_step(
        state,
        config,
        "coder",
        [python_repl_tool],
    )