Tools that treat diagrams as code, such as PlantUML, are invaluable
for communicating complex system behavior. But Unmesh
Joshi often wished for an extension to walk through these
diagrams step-by-step. Yet, extending established tools like PlantUML
often involves significant initial setup – parsing hooks, build scripts,
viewer code, packaging – enough “plumbing” to deter rapid prototyping.
He narrates now he used an LLM to build a small extension
adding step-wise playback to PlantUML sequence diagrams. This illustrates
how syntax design, parsing, SVG generation, build automation, and an HTML
viewer were iteratively developed through a conversation with an LLM –
turning tedious tasks into manageable steps.