Gracefully handling GraphRecursionError from subgraphs so the parent agent can retry or degrade

OSS Product Help LangChain
1

Hi,

Context:

  • We have a parent agent (main graph) delegating complex work to a sub-agent (subgraph). Using create_agent.

  • In certain scenarios the subgraph exceeds the recursion_limit and raises a GraphRecursionError.

  • We want the parent agent to detect this error and either:

    1. retry with adjusted parameters,

    2. degrade to a safe path,

    3. serialize the error into the graph state and continue without crashing.

Questions:

  1. Is there an official/recommended pattern to catch GraphRecursionError at the node/subgraph boundary and return structured state instead of raising?

  2. Are there hooks/middlewares to centrally handle exceptions (like GraphRecursionError) during compile/run?

  3. Can different recursion_limit values be set per subgraph/node, or adjusted dynamically between retries?

  4. Is there a built-in retry mechanism, or a recommended way to implement bounded retries via conditional edges that avoids re-triggering recursion loops?

  5. Are diagnostics (e.g., last executed node, edge ID, partial call stack) attached to GraphRecursionError to support downstream decisions?

Environment:

[project]
name = "langchainlab"
version = "0.1.0"
description = "Add your description here"
requires-python = ">=3.13, <3.14"
dependencies = [
    "black>=25.9.0",
    "deepagents>=0.1.3",
    "fastapi[standard]>=0.120.1",
    "isort>=7.0.0",
    "langchain>=1.0.2",
    "langchain-deepseek>=1.0.0",
    "langchain-openai>=1.0.1",
    "langgraph>=1.0.1",
    "langgraph-cli[inmem]>=0.4.4",
    "python-dotenv>=1.1.1",
    "tavily-python>=0.7.12",
]

Code

# from deepagents.middleware.subagents import SubAgentMiddleware
# from langchain.agents import create_agent
# from langchain.agents.middleware import TodoListMiddleware, SummarizationMiddleware

# from src.llm.llm import get_model, get_small_model
# from src.middleware import inject_project_context
# from src.subagents import codeact_subagent, research_subagent
# from src.utils import now_local, get_system_info, format_system_info

system_info = get_system_info()
formatted_system_info = format_system_info(system_info)

agent = create_agent(
    system_prompt="""You are an intelligent task coordinator focused on optimizing programming/code projects. Your job is to analyze user requirements and invoke the most suitable sub-agent to complete tasks.
"""
    ),
    model=get_model(),
    middleware=[
        inject_project_context,  # First, inject project context (no explicit call required)
        TodoListMiddleware(),
        SummarizationMiddleware(model=get_model(), max_tokens_before_summary=10000),
        SubAgentMiddleware(
            default_model=get_small_model(),
            default_tools=[],
            subagents=[research_subagent, codeact_subagent],
        ),
    ],
)