Architecture Diagrams

Boundary can generate architecture diagrams in Mermaid and GraphViz DOT formats, showing how components are organized into layers and how they depend on each other.

boundary diagram <PATH> [--diagram-type <TYPE>]

Diagram Types

Type	Format	Description
`layers` (default)	Mermaid	Components grouped into layer subgraphs with dependency edges
`dependencies`	Mermaid	Simplified layer-to-layer dependency flow with edge counts
`dot`	GraphViz	Same as `layers` in DOT format
`dot-dependencies`	GraphViz	Same as `dependencies` in DOT format

Mermaid Layer Diagram

Shows each real architectural component inside its layer subgraph. Dependency edges are drawn between components; edges that violate layer boundaries are marked as violations.

boundary diagram .
boundary diagram . --diagram-type layers

Example output:

flowchart TB
  subgraph Domain
    domain__user_User["User"]
    domain__user_UserRepository["UserRepository"]
  end
  subgraph Infrastructure
    infra__postgres_PostgresUserRepository["PostgresUserRepository"]
  end
  infra__postgres_PostgresUserRepository --> domain__user_User

Violation edges are rendered with a dashed arrow and a violation label:

  domain__user_User -.->|"infra/postgres (violation)"| infra__postgres_PostgresUserRepository

Note: Only real named components (structs, interfaces, classes) appear in diagrams. Synthetic graph nodes used for internal dependency tracking (<file>, <package>) are automatically filtered out.

Rendering

Paste the output into any Mermaid-compatible renderer:

mermaid.live — instant online preview
GitHub Markdown — wrap in a ```mermaid code block
VS Code — Mermaid Preview extension

Mermaid Dependency Flow

A higher-level view showing layer-to-layer edges with dependency counts, useful for quickly spotting which layers are talking to each other and where violations are concentrated.

boundary diagram . --diagram-type dependencies

Example output:

flowchart LR
  domain["domain (2)"]
  infrastructure["infrastructure (1)"]
  infrastructure -->|"1 deps"| domain

GraphViz DOT Diagrams

The dot and dot-dependencies types produce GraphViz DOT output. Pipe to dot to render as an image:

# Render as PNG
boundary diagram . --diagram-type dot | dot -Tpng -o architecture.png

# Render as SVG
boundary diagram . --diagram-type dot-dependencies | dot -Tsvg -o flow.svg

# Save DOT source for later
boundary diagram . --diagram-type dot > architecture.dot

Layer subgraphs use colour-coded backgrounds:

Layer	Background Colour
Domain	`#e8f5e9` (green tint)
Application	`#e3f2fd` (blue tint)
Infrastructure	`#fff3e0` (amber tint)
Presentation	`#fce4ec` (pink tint)

CI Integration

Generate and commit diagrams as part of a CI workflow:

- name: Update architecture diagram
  run: boundary diagram . > docs/architecture.mmd

Or use the diagram as a visual diff in pull requests by generating it and including it in PR descriptions.

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