The paper presents a craft-oriented middleware for assisting in situ robotic fabrication. This middleware addresses the need for sensor-based feedback in robotic fabrication involving uncertain materials, non-structured environments, or post-production surfaces. The presented middleware addresses these fabrication challenges by allowing the robot to react to its environment without the need for a predetermined program. The middleware and its components are presented, followed by experiments demonstrating in situ capacities. The first experiment demonstrates autonomous carving—performing an iterative, non-prescribed robotic fabrication process. The second experiment presents integrated fabrication—a sequence of subtractive and additive techniques performed on a non-even substrate. Together, these experiments contribute to the implementation of sensible robotic middleware in architecture and assist in restoring the lost link between workmanship and construction sites.