Methods, apparatus and articles of manufacture to provide client extensibility during provisioning of a composite blueprint are disclosed. An example virtual appliance in a cloud computing environment includes an orchestrator to facilitate provisioning of a virtual computing resource based on a blueprint, the provisioning associated with an event defined by the blueprint. The example virtual appliance also includes an event broker to maintain a set of subscribers to the event broker, each of the set of subscribers further subscribing to at least one event topic through the event broker, the event broker to trigger a notification of a first subscriber to a first event topic associated with the event when the event broker determines that the first subscriber is a blocking subscriber for the first event topic, the event broker to facilitate modification of the event by a blocking subscriber but not by a non-blocking subscriber.