Getting started

pip install loopguard-runtime

pip install "loopguard-runtime[langgraph]"

from langchain_core.tools import tool
from loopguard import LoopGuardCallbackHandler, LoopGuardInterrupt

@tool
def search(query: str) -> str:
    """Search for a source; this example always returns no results."""
    return "no results"

handler = LoopGuardCallbackHandler()
handler.raise_error = True

try:
    for _ in range(3):
        search.invoke({"query": "pricing page"}, config={"callbacks": [handler]})
except LoopGuardInterrupt as exc:
    print("LoopGuard stopped the run:", exc)

report = handler.report()
print("Decision:", report["decisions"][-1]["action"])
print("Tool calls:", report["metrics"]["tool_calls"])

python first_run.py

Decision: stop
Tool calls: 3

handler = LoopGuardCallbackHandler(interrupt_on_fatal=False)