A stack-based conversation engine is provided. The conversation engine enables a voice or text based virtual assistant to create interactive, conversational experiences in an extensible manner. The conversation engine can be used to support a conversation between a user and a virtual assistant. The conversation engine can be configured to receive, from the virtual assistant, a fulfillment request specifying an intent from the virtual assistant; push an item onto a conversation stack stored, the item including an identifier of the intent; execute an action handler associated with the intent to generate instructions to manipulate the conversation stack; manipulate the conversation stack according to the instructions; and store the conversation stack for subsequent processing in support of the conversation.