Fallback handling

Real users type things your router never planned for. "How long have you been open?" "Is my doctor available on weekends?" "Thanks!" Without a fallback node these messages either crash the flow or get force-routed into the booking branch and produce nonsense. The smalltalk node is your escape hatch.

booking_graph.py

python

async def smalltalk(state: BookingState) -> BookingState:
    intent = state.get("intent") or "unknown"
    system = (
        "You are a friendly healthcare booking assistant. "
        "Keep replies to 1-2 sentences."
    )
    prompt = (
        f"The patient's intent was classified as '{intent}'. "
        f"Message: {state.get('user_message', '')}\n"
        "Reply helpfully. If they want to book, invite them to describe their symptom."
    )
    state["assistant_reply"] = await _llm_text(prompt, system)
    state["status"] = state.get("status") or "gathering"
    _record_event(state, "smalltalk", {})
    return state

The fallback node takes any non-booking intent and produces a short, helpful reply. It nudges the user toward the happy path (describe a symptom) without locking them out. The status stays in gathering so the next turn starts fresh.

Ordering exercise: Order what happens when intent = unknown

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Quiz: Quiz

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Checkpoint: Intent routing checkpoint

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