Embodiments relate to systems, devices, and computing-implemented methods for providing a response system for a chatbot program and/or virtual assistant that can perform operations including receiving user input that includes an identifier, determining a current state based on the identifier, determining an intent engine stack based on the current state, processing the user input using an intent engine in the intent engine stack to obtain an intent and a variable, performing an action based on the current state, the intent, and the variable, and transitioning to a next state based on the action, the current state, the intent, and the variable.