rohitg00/ai-engineering-from-scratch · error · RuntimeError

unknown node {current!r}

Error message

unknown node {current!r}

What it means

Error "unknown node {current!r}" thrown in rohitg00/ai-engineering-from-scratch.

Source

Thrown at phases/14-agent-engineering/13-langgraph-stateful-graphs/code/main.py:110

    def __init__(self, graph: StateGraph,
                 checkpointer: InMemoryCheckpointer) -> None:
        self.graph = graph
        self.checkpointer = checkpointer

    def run(self, session_id: str, initial_state: State,
            resume_from: str | None = None,
            state_override: State | None = None) -> State:
        if state_override is not None:
            state = copy.deepcopy(state_override)
        else:
            state = copy.deepcopy(initial_state)
        current = resume_from or self.graph.entry
        if current is None:
            raise RuntimeError("no entry node set")
        while current is not None and current != END:
            fn = self.graph.nodes.get(current)
            if fn is None:
                raise RuntimeError(f"unknown node {current!r}")
            update = fn(state)
            if update is None:
                update = {}
            state = {**state, **update}
            self.checkpointer.save(session_id, current, state)
            if state.get("_pause_reason"):
                reason = state.pop("_pause_reason")
                raise PausedAtNode(current, state)
            current = self.graph._next(current, state)
        return state


def _classify(state: State) -> Update:
    text = state["input"].lower()
    if "refund" in text or "money back" in text:
        route = "refund"
    elif "crash" in text or "bug" in text or "error" in text:
        route = "bug"

View on GitHub (pinned to 39ea8a1c6d)

When it happens

Trigger: Thrown at phases/14-agent-engineering/13-langgraph-stateful-graphs/code/main.py:110 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of rohitg00/ai-engineering-from-scratch@39ea8a1c6d (2026-08-26). Data as JSON: /api/errors/6992c59a26431501. Report an issue: GitHub.