Interrupt and resume

interrupt() pauses the graph and exposes a JSON-serializable request to the caller. Resume the same checkpoint with Command(resume=...) and the same thread_id.¹

Tiny example

from langgraph.checkpoint.memory import InMemorySaver
from langgraph.types import Command, interrupt

def approve_refund(state: RefundState) -> dict:
    approved = interrupt({"question": "Approve £450 refund?"})
    return {"approved": bool(approved)}

graph = builder.compile(checkpointer=InMemorySaver())
config = {"configurable": {"thread_id": "refund-104"}}

paused = graph.invoke({"amount": 450}, config)
finished = graph.invoke(Command(resume=True), config)

Node calls interrupt().
LangGraph saves the pause through the checkpointer.
The application shows the request to a reviewer.
The application resumes the same thread.
The resume value becomes the return value of interrupt().

Failure note

On resume, LangGraph restarts the node from its beginning. Code before interrupt() runs again. Put side effects after approval, move them to another node, or make them idempotent. Do not wrap interrupt() in a broad try/except; it uses a special exception to reach the runtime.

LangChain, Interrupts. ↩