Diagnose: GraphRecursionError / GRAPH_RECURSION_LIMIT in a LangGraph run

Symptom

GRAPHRECURSIONLIMIT: the StateGraph reached the maximum number of steps before hitting a stop condition.

Confirm

Trace one run step by step (or log node entries). Ask: does this graph have a path to END in the number of steps you expect? Watch for a pair of nodes bouncing back and forth.

Cause

Two distinct causes, different fixes:

1. Infinite loop: a conditional edge whose condition never selects the exit, or literal add_edge("a", "b") + add_edge("b", "a") with no conditional exit.
2. Legitimately deep graph: many sequential steps, large fan-outs, long agent loops that really do need hundreds of steps.

Fix

• Loop: fix the condition so some path reaches END. This is the fix in most cases.
• Deep: raise it for that invocation:

graph.invoke({...}, {"recursion_limit": 1000})

Verify

Re-run and confirm it terminates. If you raised the limit, also confirm the step count is sane; a graph that needs 900 steps to do a 10-step job has a logic problem, not a limit problem.

Diagnostic procedure grounded in the official GRAPHRECURSIONLIMIT error page, verified 2026-09-26. Error page: https://docs.langchain.com/oss/python/langgraph/errors/GRAPHRECURSIONLIMIT