Use cases
What people actually use it for.
Each page includes who it is not for, which is usually the more useful half.
$curl -fsSL https://lucidtrain.com/install.sh | sh
- Onboarding Engineers to a CodebaseThe first week is spent building a mental model that somebody already has. A diagram transfers it in an afternoon.
- Documenting Legacy CodeIncluding the newest kind of legacy code: what a coding agent wrote for you over several sessions that nobody has looked at as a whole.
- Architecture ReviewMost of the effort in an architecture review goes into producing the diagrams, and most of those diagrams describe the system as remembered rather than as built.
- System Design Interview PreparationThe diagram is the easy part. Interviews are decided by the tradeoffs you can defend when the interviewer pushes.
- Technical Design DocumentsThe diagram in a design doc usually gets drawn last, badly, because everyone is tired of the document by then.
- Migration PlanningMigrations fail on the intermediate states, which is exactly the part nobody draws.
- Offline and Air-Gapped TeamsEvery other tool in this category is a web application. If your code cannot go to a browser, that rules all of them out.
- Keeping Diagrams in Sync with CodeEvery architecture diagram is accurate on the day it is drawn. The question is what happens in month four.
- Open Source MaintainersMost first-time contributors give up before opening a pull request, and a surprising share of that is not knowing where anything is.
- Consultants and AgenciesYou are handed a codebase, given a fortnight, and expected to explain it back. Uploading it to a SaaS tool is usually not an option.
Elsewhere
- System Design TemplatesEach template is a real diagram produced by the same layout engine the app runs, not a picture of one.
- AI System DesignThe diagram can cause the code, not just describe it.
- Harness EngineeringAgent equals model plus harness. The harness is the half you can actually change.
- Coding Engines Lucid Train Can DriveThe binary is already on your machine and already signed in. Nothing is proxied and no credential passes through us.
- Dependency and Agent Supply Chain AuditYour packages are audited by everyone. The programs your agent launches are audited by almost no one.
- Grafana and Observability in a Coding AgentNothing is exported to us. It reads the Grafana you already run, with your credential, on your machine.
- AI Design Mode for Web PagesRunning on the Claude Code or Codex CLI you already have, with your repository open beside it.
- Software Architecture GlossaryWhat each term means, where it came from, and where it stops being useful.
- Guides to Choosing Architecture ToolsNo winner is declared, because the right answer depends on constraints a web page cannot see.
- Alternatives to Popular Diagramming and Agent ToolsEach page sorts the field by the reason you are leaving, because that is what decides the answer.
- MCP and Architecture DiagramsYour agent supplies the structure. A constraint solver decides where everything goes.
- Generate a Diagram from Your CodeEvery source below lists the exact files it reads and the constructs it maps to diagram nodes.
- AI Diagram GeneratorsThe agent emits a semantic graph and ELK computes the layout, so overlapping boxes are structurally impossible.
- Compare Lucid TrainEvery page says what the other tool is better at. If that section were empty the comparison would not be worth reading.
- Convert Code and DiagramsEvery conversion page states what survives the round trip and what does not.
- Beyond DiagramsDiagrams are the front door. These are the rooms behind it.