langgraph.errors.GraphRecursionError: Recursion limit of 25 reached without hitting a stop condition.

[stelterlab]

I got this error while running a research. Found a limit set in src/workflow.py set to 100. Doesn't seem to get used.

Used version of yesterday (69d6e16) with OpenAI as LLM provider and Tavily AI as Search Engine.

My request was: "How to create a read only user in OpenStack who can see every resource in every project and every domain?"

`ERROR: Exception in ASGI application
Traceback (most recent call last):
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/responses.py", line 270, in call
await wrap(partial(self.listen_for_disconnect, receive))
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/responses.py", line 266, in wrap
await func()
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/responses.py", line 234, in listen_for_disconnect
message = await receive()
^^^^^^^^^^^^^^^
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/uvicorn/protocols/http/h11_impl.py", line 531, in receive
await self.message_event.wait()
File "/Users/cosinus/.local/share/uv/python/cpython-3.12.8-macos-aarch64-none/lib/python3.12/asyncio/locks.py", line 212, in wait
await fut
asyncio.exceptions.CancelledError: Cancelled by cancel scope 10a9cee40

During handling of the above exception, another exception occurred:

• Exception Group Traceback (most recent call last):
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/_utils.py", line 76, in collapse_excgroups
  | yield
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/responses.py", line 263, in call
  | async with anyio.create_task_group() as task_group:
  | ^^^^^^^^^^^^^^^^^^^^^^^^^
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/anyio/_backends/_asyncio.py", line 767, in aexit
  | raise BaseExceptionGroup(
  | ExceptionGroup: unhandled errors in a TaskGroup (1 sub-exception)
  +-+---------------- 1 ----------------
  | Traceback (most recent call last):
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/uvicorn/protocols/http/h11_impl.py", line 403, in run_asgi
  | result = await app( # type: ignore[func-returns-value]
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/uvicorn/middleware/proxy_headers.py", line 60, in call
  | return await self.app(scope, receive, send)
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/fastapi/applications.py", line 1054, in call
  | await super().call(scope, receive, send)
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/applications.py", line 112, in call
  | await self.middleware_stack(scope, receive, send)
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/middleware/errors.py", line 187, in call
  | raise exc
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/middleware/errors.py", line 165, in call
  | await self.app(scope, receive, _send)
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/middleware/cors.py", line 93, in call
  | await self.simple_response(scope, receive, send, request_headers=headers)
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/middleware/cors.py", line 144, in simple_response
  | await self.app(scope, receive, send)
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/middleware/exceptions.py", line 62, in call
  | await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
  | raise exc
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
  | await app(scope, receive, sender)
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/routing.py", line 714, in call
  | await self.middleware_stack(scope, receive, send)
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/routing.py", line 734, in app
  | await route.handle(scope, receive, send)
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/routing.py", line 288, in handle
  | await self.app(scope, receive, send)
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/routing.py", line 76, in app
  | await wrap_app_handling_exceptions(app, request)(scope, receive, send)
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
  | raise exc
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
  | await app(scope, receive, sender)
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/routing.py", line 74, in app
  | await response(scope, receive, send)
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/responses.py", line 262, in call
  | with collapse_excgroups():
  | ^^^^^^^^^^^^^^^^^^^^
  | File "/Users/cosinus/.local/share/uv/python/cpython-3.12.8-macos-aarch64-none/lib/python3.12/contextlib.py", line 158, in exit
  | self.gen.throw(value)
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/_utils.py", line 82, in collapse_excgroups
  | raise exc
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/responses.py", line 266, in wrap
  | await func()
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/responses.py", line 246, in stream_response
  | async for chunk in self.body_iterator:
  | File "/Users/cosinus/src/deer-flow/src/server/app.py", line 98, in _astream_workflow_generator
  | async for agent, _, event_data in graph.astream(
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/langgraph/pregel/init.py", line 2305, in astream
  | async for _ in runner.atick(
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/langgraph/pregel/runner.py", line 527, in atick
  | _panic_or_proceed(
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/langgraph/pregel/runner.py", line 619, in _panic_or_proceed
  | raise exc
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/langgraph/pregel/retry.py", line 128, in arun_with_retry
  | return await task.proc.ainvoke(task.input, config)
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/langgraph/utils/runnable.py", line 583, in ainvoke
  | input = await step.ainvoke(input, config, **kwargs)
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/langgraph/utils/runnable.py", line 371, in ainvoke
  | ret = await asyncio.create_task(coro, context=context)
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  | File "/Users/cosinus/src/deer-flow/src/graph/nodes.py", line 420, in researcher_node
  | return await _setup_and_execute_agent_step(
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  | File "/Users/cosinus/src/deer-flow/src/graph/nodes.py", line 412, in _setup_and_execute_agent_step
  | return await _execute_agent_step(state, default_agent, agent_type)
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  | File "/Users/cosinus/src/deer-flow/src/graph/nodes.py", line 331, in _execute_agent_step
  | result = await agent.ainvoke(input=agent_input)
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/langgraph/pregel/init.py", line 2420, in ainvoke
  | async for chunk in self.astream(
  | File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/langgraph/pregel/init.py", line 2327, in astream
  | raise GraphRecursionError(msg)
  | langgraph.errors.GraphRecursionError: Recursion limit of 25 reached without hitting a stop condition. You can increase the limit by setting the recursion_limit config key.
  | For troubleshooting, visit: https://python.langchain.com/docs/troubleshooting/errors/GRAPH_RECURSION_LIMIT
  | During task with name 'researcher' and id '52c1115d-7c8c-9b68-249f-25927e097f6b'
  +------------------------------------

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/uvicorn/protocols/http/h11_impl.py", line 403, in run_asgi
result = await app( # type: ignore[func-returns-value]
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/uvicorn/middleware/proxy_headers.py", line 60, in call
return await self.app(scope, receive, send)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/fastapi/applications.py", line 1054, in call
await super().call(scope, receive, send)
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/applications.py", line 112, in call
await self.middleware_stack(scope, receive, send)
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/middleware/errors.py", line 187, in call
raise exc
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/middleware/errors.py", line 165, in call
await self.app(scope, receive, _send)
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/middleware/cors.py", line 93, in call
await self.simple_response(scope, receive, send, request_headers=headers)
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/middleware/cors.py", line 144, in simple_response
await self.app(scope, receive, send)
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/middleware/exceptions.py", line 62, in call
await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
raise exc
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
await app(scope, receive, sender)
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/routing.py", line 714, in call
await self.middleware_stack(scope, receive, send)
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/routing.py", line 734, in app
await route.handle(scope, receive, send)
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/routing.py", line 288, in handle
await self.app(scope, receive, send)
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/routing.py", line 76, in app
await wrap_app_handling_exceptions(app, request)(scope, receive, send)
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
raise exc
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
await app(scope, receive, sender)
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/routing.py", line 74, in app
await response(scope, receive, send)
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/responses.py", line 262, in call
with collapse_excgroups():
^^^^^^^^^^^^^^^^^^^^
File "/Users/cosinus/.local/share/uv/python/cpython-3.12.8-macos-aarch64-none/lib/python3.12/contextlib.py", line 158, in exit
self.gen.throw(value)
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/_utils.py", line 82, in collapse_excgroups
raise exc
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/responses.py", line 266, in wrap
await func()
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/starlette/responses.py", line 246, in stream_response
async for chunk in self.body_iterator:
File "/Users/cosinus/src/deer-flow/src/server/app.py", line 98, in _astream_workflow_generator
async for agent, _, event_data in graph.astream(
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/langgraph/pregel/init.py", line 2305, in astream
async for _ in runner.atick(
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/langgraph/pregel/runner.py", line 527, in atick
_panic_or_proceed(
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/langgraph/pregel/runner.py", line 619, in _panic_or_proceed
raise exc
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/langgraph/pregel/retry.py", line 128, in arun_with_retry
return await task.proc.ainvoke(task.input, config)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/langgraph/utils/runnable.py", line 583, in ainvoke
input = await step.ainvoke(input, config, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/langgraph/utils/runnable.py", line 371, in ainvoke
ret = await asyncio.create_task(coro, context=context)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/cosinus/src/deer-flow/src/graph/nodes.py", line 420, in researcher_node
return await _setup_and_execute_agent_step(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/cosinus/src/deer-flow/src/graph/nodes.py", line 412, in _setup_and_execute_agent_step
return await _execute_agent_step(state, default_agent, agent_type)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/cosinus/src/deer-flow/src/graph/nodes.py", line 331, in _execute_agent_step
result = await agent.ainvoke(input=agent_input)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/langgraph/pregel/init.py", line 2420, in ainvoke
async for chunk in self.astream(
File "/Users/cosinus/src/deer-flow/.venv/lib/python3.12/site-packages/langgraph/pregel/init.py", line 2327, in astream
raise GraphRecursionError(msg)
langgraph.errors.GraphRecursionError: Recursion limit of 25 reached without hitting a stop condition. You can increase the limit by setting the recursion_limit config key.
For troubleshooting, visit: https://python.langchain.com/docs/troubleshooting/errors/GRAPH_RECURSION_LIMIT
During task with name 'researcher' and id '52c1115d-7c8c-9b68-249f-25927e097f6b'`

[fxnie]

same

[biosafetylvl5]

Same 😢

This also occurred for me (like @stelterlab) while handling another exception.

Using the latest commit as of now, with docker.

[changqingla]

#138

[henbucuoshanghai]

same，why？

[henbucuoshanghai]

what happening when has this error?

[hetaoBackend]

Thanks for the context here. I did a careful shell check against current main, and this is already implemented.

Current main now mitigates this failure mode in two ways: Gateway runs default to recursion_limit=100 instead of LangGraph's native 25, and the lead agent includes LoopDetectionMiddleware that warns on repeated tool calls and strips tool_calls at a hard limit so the run can return partial results instead of looping to GraphRecursionError. The issue also has merged related work in #138 and later #1056, with current source and tests covering the behavior.

Best possible solution:

Close this issue as implemented on current main. Keep the Gateway default recursion_limit=100 and LoopDetectionMiddleware behavior; any remaining cases where a specific caller still omits or overrides recursion_limit should be filed as a narrower reproduction with the affected endpoint/config.

What I checked:

• Gateway default recursion limit: Current main initializes Gateway run config with recursion_limit=100, so DeerFlow's Gateway path no longer inherits LangGraph's default limit of 25. (backend/app/gateway/services.py:132, ad6d934a5fd0)
• Loop detection middleware wired into lead agent: The lead agent middleware chain appends LoopDetectionMiddleware before ClarificationMiddleware, making loop breaking part of normal lead-agent execution. (backend/packages/harness/deerflow/agents/lead_agent/agent.py:261, ad6d934a5fd0)
• Loop detection hard stop behavior: LoopDetectionMiddleware tracks repeated tool-call hashes, warns after the configured threshold, and at the hard limit returns an AIMessage update with tool_calls cleared and a forced-stop message. (backend/packages/harness/deerflow/agents/middlewares/loop_detection_middleware.py:179, ad6d934a5fd0)
• Regression tests cover hard stop: The loop detection test suite verifies that the fourth repeated call can trigger a hard stop and that the resulting AIMessage has tool_calls == []. (backend/tests/test_loop_detection_middleware.py:176, ad6d934a5fd0)
• Related merged fixes: The issue discussion links merged PR Fix :This PR can resolve the issue of exceeding the default tool invocation limit by setting the recursion limit through an environment variable.mit #138 for configurable recursion limit behavior, and later related PR feat: add LoopDetectionMiddleware to break repetitive tool call loops #1056 merged LoopDetectionMiddleware to break repetitive tool-call loops before recursion_limit kills the run.
• Fix provenance: Commit c3170f2 improves LoopDetectionMiddleware by hashing tool calls with stable keys so near-identical repeated reads/commands are caught more reliably; current main contains it. (backend/packages/harness/deerflow/agents/middlewares/loop_detection_middleware.py:62, c3170f22dac7)

Likely related people:

• virtaava: Authored merged PR feat: add LoopDetectionMiddleware to break repetitive tool call loops #1056, which added LoopDetectionMiddleware and explicitly marked this issue as related to the repetitive tool-call loop failure mode. (role: introduced related loop-breaking feature; confidence: high; commits: d833339c3873; files: backend/packages/harness/deerflow/agents/middlewares/loop_detection_middleware.py, backend/packages/harness/deerflow/agents/lead_agent/agent.py, backend/tests/test_loop_detection_middleware.py)
• koppx: Authored commit c3170f2, which hardened LoopDetectionMiddleware hashing for repeated tool calls with nearby or normalized arguments. (role: recent maintainer of loop detection behavior; confidence: high; commits: c3170f22dac7; files: backend/packages/harness/deerflow/agents/middlewares/loop_detection_middleware.py, backend/tests/test_loop_detection_middleware.py)
• SHIYAO ZHANG: Local blame on current main points the Gateway default recursion_limit and initial visible LoopDetectionMiddleware wiring to the grafted current-main history at commit 163121d; the exact earlier feature ancestry is partly collapsed in this checkout. (role: current-main code history owner; confidence: medium; commits: 163121d32756; files: backend/app/gateway/services.py, backend/packages/harness/deerflow/agents/lead_agent/agent.py, backend/packages/harness/deerflow/agents/middlewares/loop_detection_middleware.py)
• changqingla: Authored merged PR Fix :This PR can resolve the issue of exceeding the default tool invocation limit by setting the recursion limit through an environment variable.mit #138, linked from the issue discussion, to address exceeding the default tool invocation limit by setting recursion limit through environment/configuration. (role: earlier related fix contributor; confidence: medium; commits: 1a43beb02301; files: src/workflow.py)

So I’m closing this as already implemented rather than keeping a duplicate issue open.

Codex review notes: model gpt-5.5, reasoning high; reviewed against ad6d934a5fd0; fix evidence: commit c3170f22dac7, main fix timestamp 2026-04-07T17:46:33+08:00.