CIAO - Code In Architecture Out - Automated Software Architecture Documentation with Large Language Models

TL;DR

This paper introduces CIAO, a structured LLM-based process for automatically generating comprehensive system-level architectural documentation from GitHub repositories, evaluated positively by developers.

Contribution

It presents a novel, standards-oriented workflow leveraging LLMs to produce coherent architectural documentation directly from code repositories.

Findings

Developed a process that generates system-level architecture documents in minutes.

Developers find the generated documentation valuable and broadly accurate.

The approach is cost-effective and suitable for practical use.

Abstract

Software architecture documentation is essential for system comprehension, yet it is often unavailable or incomplete. While recent LLM-based techniques can generate documentation from code, they typically address local artifacts rather than producing coherent, system-level architectural descriptions. This paper presents a structured process for automatically generating system-level architectural documentation directly from GitHub repositories using Large Language Models. The process, called CIAO (Code In Architecture Out), defines an LLM-based workflow that takes a repository as input and produces system-level architectural documentation following a template derived from ISO/IEC/IEEE 42010, SEI Views \& Beyond, and the C4 model. The resulting documentation can be directly added to the target repository. We evaluated the process through a study with 22 developers, each reviewing the documentation generated for a repository they had contributed to. The evaluation shows that developers generally perceive the produced documentation as valuable, comprehensible, and broadly accurate with respect to the source code, while also highlighting limitations in diagram quality, high-level context modeling, and deployment views. We also assessed the operational cost of the process, finding that generating a complete architectural document requires only a few minutes and is inexpensive to run. Overall, the results indicate that a structured, standards-oriented approach can effectively guide LLMs in producing system-level architectural documentation that is both usable and cost-effective.