This paper investigates the spatial mechanism of architecture without order that can embrace sustainability in architecture. Throughout history, the architectural design process has never been separated from applying for rigid order as an ideal paradigm. However, the application of rigid order tends to look apart from the existing conditions and ignore the chronological time aspect. Therefore, no rigid order mechanism can confront the possibility of existing context conditions that naturally appear to reinvent sustainability's design in architecture. The study utilized a contingency and indeterminacy approach with its potential to redefine the application of rigid order in architectural design. The discussion circulates the idea that contingency is emphasized in three things, i.e., subjects that keep changing, changes of subject, and chronological lines of time. These three aspects are further utilized to analyze precedents that used a contingency approach through their design process. This paper proposes a gradation zone as a potential mechanism for developed architectural design in no rigid order. Gradation zone includes a form of dynamic implementation of simultaneous events, immersive experience and ambiance, and different space quality with the nature of constantly changing according to the possibilities. Further discussion using this gradation zone within the design process can reinvent sustainability forms such as boundary, spatial organization, and the path that can exist without rigid order. © 2024 American Institute of Physics Inc.. All rights reserved.