Cosine is an AI tool designed to assist developers in understanding and working with codebases more effectively. It acts as a developer companion, providing contextual answers, code explanations, and code suggestions. Unlike other AI copilots, Cosine goes beyond simple autocompletion and takes into account a deep semantic understanding of the codebase. It reads and indexes every code snippet in the codebase, creating a graph relationship between files and functions, and generating a comprehensive understanding of the code.With Cosine, developers can ask questions about their codebase, whether they are high-level or nuanced, and receive superhuman level answers. The tool combines multiple heuristics, including static analysis and semantic search, to provide fully contextual answers. In addition, developers can ask Cosine for guidance on adding new features or modifying existing code, and it will generate step-by-step guides.Cosine is privacy-focused and does not store code or submit inputs for training to external servers. The tool uses OpenAI to create on-the-fly semantic embeddings, which point to the code, and stores them locally on the user's system in a .cosine/ folder.Overall, Cosine aims to improve developer productivity by providing a comprehensive understanding of codebases and assisting with code-related questions and tasks. It is available as a VS Code extension and can be installed from the Visual Studio marketplace.