Martin Fowler

Tools that treat diagrams as code, such as PlantUML, are invaluable for communicating complex system behavior. Their text-based format simplifies versioning, automation, and evolving architectural diagrams alongside code. In my work explaining distributed systems, PlantUML’s sequence diagrams are particularly useful for capturing interactions precisely.

However, I often wished for an extension to walk through these diagrams step-by-step, revealing interactions sequentially rather than showing the entire complex flow at once—like a slideshow for execution paths. This desire reflects a common developer scenario: wanting personalized extensions or internal tools for their own needs.

Yet, extending established tools like PlantUML often involves significant initial setup—parsing hooks, build scripts, viewer code, packaging—enough “plumbing” to deter rapid prototyping. The initial investment required to begin can suppress good ideas.

This is where Large Language Models (LLMs) prove useful. They can handle boilerplate tasks, freeing developers to focus on design and core logic. This article details how

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