Description This preprint presents the Nemosine Framework, a modular cognitive architecture designed to support assisted reasoning, structured thinking, and systematic analysis. The framework operates through coordinated functional cognitive modules (“personas”) that organize tasks such as planning, cross-checking, metacognitive reflection, and symbolic processing, forming an operational model for complex reasoning support. The proposed architecture integrates principles from metacognition, distributed cognition, and symbolic-modular systems, emphasizing interpretability, modular coordination, and implementation-oriented design. The system is documented through formal specification, structural modeling, and reproducible architectural artifacts. This paper serves as the core conceptual reference of the Nemosine project.Supplementary technical documentation, architectural appendices, and related artifacts are maintained separately to preserve clarity and editorial separation. The complete project documentation, versioned materials, and traceability index are available via the Open Science Framework (OSF) project hub: https://osf.io/r4yf8 This version corresponds to the preprint submitted to arXiv and SciELO Preprints. No changes were made to the conceptual content relative to those submissions. Version 0.2 includes a supporting technical appendix consolidating architectural artifacts previously published separately.