This workshop examines the design and evaluation of behavioural paradigms that effectively elicit and measure proactive behaviour in Intelligent Virtual Agents (IVA) research. Current paradigms focus mainly on agent behaviour. However, it remains unclear how these paradigms effectively help to elicit and measure proactive agent interactions and produce ecologically valid data, particularly for the paradigms that promote the use of different modalities during interaction beyond text or speech. We invite researchers to discuss methodologies for developing tasks that not only structure agent behaviours but also provide meaningful insights into the social and cognitive processes involved in proactive interactions.