Lucid Train compared with PlantUML.
PlantUML has been the diagram-as-code default for years, and both of its main limitations are the same age.
Lucid Train generates diagrams from your codebase and lays them out with ELK, a modern layered constraint solver with orthogonal edge routing. PlantUML requires you to write the diagram by hand as text and renders it through Graphviz, which produces denser output that is usually corrected with manual layout hints. Lucid Train also attaches real service icons, runs offline against local models, and can convert a diagram into a coding specification.
You do not write it
PlantUML syntax describes a diagram you have already worked out. Lucid Train reads manifests, entry points and the import graph and produces the graph for you, which is the difference between documenting a system you understand and understanding one you inherited.
A modern layout engine
PlantUML's default rendering comes from Graphviz, which is capable and produces the characteristic dense output that people either accept or fight with layout hints. ELK is a layered solver with orthogonal routing and container-aware tier bands, which shows most on larger diagrams and needs no hints.
Icons, tiers and states
Real bundled service logos on every card, seven tier bands, node states that mark single points of failure, and per-node documentation panels. PlantUML has sprite libraries; it has no concept of a tier or a failure state.
What PlantUML is good at
Coverage and scriptability. It draws every UML type and a great deal more, it is free, it runs anywhere Java runs, and it renders in a build pipeline from text held in version control. For generated documentation in CI it is proven.
Side by side
| Lucid Train | PlantUML | |
|---|---|---|
| Generates from a codebase | Yes | No, written by hand |
| Layout engine | ELK, layered solver | Graphviz, usually |
| Real service icons | Yes, bundled, offline | Sprite libraries |
| Tier bands and failure marking | Yes | No |
| Diagram to code as a specification | Yes | No |
| Runs fully offline with local models | Yes | Yes, no AI |
| Export | SVG, 2x PNG, Markdown, .excalidraw | SVG, PNG, PDF |
| Renders in CI from text | No | Yes |
| Price | CLI free and open source; desktop $3/month, 7-day trial, no card | Free, open source |
Questions
Can Lucid Train export PlantUML?
No. The agent can write PlantUML into a file as text, but there is no PlantUML rendering or round-trip in the product.
Is ELK better than Graphviz for architecture diagrams?
For layered diagrams with tier groupings, yes: it produces fewer crossings and more predictable grouping, and it does not need manual hints, which is the thing diagram-as-code was supposed to avoid.
Which for a documentation pipeline?
PlantUML renders from text in CI and Lucid Train is a desktop application. For generated docs at build time, PlantUML fits; for understanding and designing systems, Lucid Train does.
Affiliation
Lucid Train is an independent product and is not affiliated with, endorsed by, or connected to the product described on this page. All names and trademarks belong to their respective owners. Pricing and features were checked on 19 August 2026 and change without notice; check the vendor's own site before deciding.
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