The Merdeka Curriculum gives Indonesian teachers substantial flexibility to design and adapt instruction, yet the educational value of this flexibility depends on how coherently planned learning is enacted in the classroom. This qualitative classroom case examines the alignment between a Grade 3 Indonesian-language teaching module and its enactment in a public primary school in Pasuruan, Indonesia. Data were drawn from direct classroom observation, a teacher interview, and document analysis conducted on 20 April 2026. The analysis compared planned and enacted instruction across five dimensions: content and objectives, pedagogy and student activity, learning media, assessment and feedback, and contextual adaptation. The teaching module was administratively comprehensive, but several elements were weakly operationalized. In enactment, planned interactive activities and media were reduced to teacher explanation, brief questioning, individual textbook work, and teacher initials on completed tasks. The teacher attributed these adaptations to heterogeneous student readiness, limited instructional time, and the need to keep the lesson manageable. We interpret this pattern as adaptive simplification: a context-responsive adjustment that preserved lesson continuity but reduced learner agency, multimodal support, and formative closure. The study contributes a planning–enactment alignment matrix for distinguishing productive adaptation from reductive simplification and argues that curriculum flexibility should preserve core pedagogical functions rather than merely reduce activity complexity.