| name | c4-diagrams |
| description | Use when explaining existing architecture, visualizing a new system before detailed design, mapping software boundaries, or creating C4-style ASCII or Mermaid diagrams. |
| license | MIT |
| compatibility | Codex lazy-loaded skill for OpenSpec projects. |
C4 Diagrams
Use this optional skill only after recommendation and user consent.
Focus on boundaries, responsibilities, actors, dependencies, and data flow.
Draw only the levels that answer the current question.
First Gates
Establish purpose, format, and rigor. If the user has not specified them, ask a
single concise question.
- Purpose: existing code, new system, design review.
- Format: ASCII or Mermaid.
- Rigor: strict C4, lightweight C4-inspired, or hybrid.
Workflow
- For existing code, inspect entry points, runtime boundaries, integrations,
persistence, and major directories before diagramming.
- Pick the smallest useful diagram set: system context, container, component,
dynamic, or deployment.
- Draw in ASCII or plain Mermaid
flowchart / sequenceDiagram.
- Explain boundaries, responsibilities, assumptions, and open questions in
3-6 bullets.
- Stop before detailed design unless the user asks to continue.
Output Rules
- Containers are runnable or deployable units.
- Components live inside one container.
- Do not hide uncertainty; label assumptions and unknowns.
- Avoid drawing all C4 levels by default.
