CobaltC Semantic Compiler is a trustworthy compiler for the CobaltC language that generates explanatory semantic analysis in JSON format. It checks source code against the language specification, produces Explainable Semantic IR with compiler decisions, and generates HTML reports explaining program behavior alongside source code. The project targets CobaltC 1.0.3 with incremental feature support and emphasizes transparency through evidence and clear documentation of implemented versus unsupported features.