This study analyzes the intersection of spiritual identity and architectural minimalism in the Saminah Sihyadi Mosque, Surakarta, by interpreting its spatial configuration as a multimodal cultural text. Drawing on Kress and van Leeuwen's multimodal discourse analysis, it investigates how visual and material elements—unpolished stone, wood, and natural light—function as semiotic resources communicating Javanese values and Islamic humility. Through qualitative field research combining visual documentation, spatial observation, and semi-structured interviews, the mosque's spatial elements are analyzed across three metafunctions: representational, interactive, and compositional. The findings demonstrate that meaning in this mosque is produced not through conventional symbolic markers, but through the relational interplay of material restraint, spatial permeability, and diffused light—a condition this study terms an "aesthetic of sincerity." This spatial logic articulates Javanese-Islamic values such as humility, balance, and inclusivity through embodied and atmospheric experience rather than ornamental assertion. The study concludes that contemporary mosque architecture in Indonesia is shifting toward spatially enacted religious expression, where absence of grandeur operates as a deliberate semiotic strategy. These findings suggest that multimodal semiotics offers a productive framework for analyzing religious spaces that communicate cultural identity through relational, experiential, and material means.