Upper bound on number of iterations (#754)

Some custom agents might continue to iterate until they find the correct
answer, getting stuck on loops that generate request after request and
are really expensive for the end user. Putting an upper bound for the
number of iterations
by default controls this and can be explicitly tweaked by the user if
necessary.

Co-authored-by: Francisco Ingham <>

Author: fpingham

langchain/agents/agent.py

@@ -199,7 +199,7 @@ class AgentExecutor(Chain, BaseModel):
     agent: Agent
     tools: List[Tool]
     return_intermediate_steps: bool = False
-    max_iterations: Optional[int] = None
+    max_iterations: Optional[int] = 15
     early_stopping_method: str = "force"
 
     @classmethod