Abstract: Systems and methods of compressing input source code for processing by a large language model with a limited context window, parsing input source code using the programming language's formal grammar to generate an Abstract Syntax Tree (AST), generating a semantic model by extracting from the AST structural relationships functional relationships, classifying each AST node into a semantic tier based on its element type, selecting AST nodes for retention by iteratively including nodes in descending importance order, enabling the large language model to request selective expansion, transmitting the compressed output with embedded reference records to the large language model, and upon receiving from the large language model a request to expand a specific region identified by AST node reference, retrieving the original source for that region, transmitting it.