# Diagramming Code

Generates Mermaid diagrams from Trailmark code graphs.

- Repository: https://github.com/trailofbits/skills (7935 stars)
- Category: Engineering
- License: CC-BY-SA-4.0
- Last updated: 2026-10-28
- Runs scripts: yes, review before use

## Install

Claude Code: `npx skills add trailofbits/skills --skill diagramming-code -g -a claude-code -y`
Codex: `npx skills add trailofbits/skills --skill diagramming-code -g -a codex -y`
Cursor: `npx skills add trailofbits/skills --skill diagramming-code -g -a cursor -y`
Gemini CLI: `npx skills add trailofbits/skills --skill diagramming-code -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add trailofbits/skills`

## Description

Generates Mermaid diagrams from Trailmark code graphs. Produces call graphs, class hierarchies, module dependency maps, containment diagrams, complexity heatmaps, and attack surface data flow visualizations. Use when visualizing code architecture, drawing call graphs, generating class diagrams, creating dependency maps, producing complexity heatmaps, or visualizing data flow and attack surface paths as Mermaid diagrams.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Diagramming Code

Generates Mermaid diagrams from Trailmark's code graph. A pre-made script
handles Mermaid syntax generation; Claude selects the diagram type and
parameters. Trailmark 0.4.0 includes a native `trailmark diagram` command; use
it only after a version/command check, otherwise use this skill's bundled
script.

## When to Use

- Visualizing call paths between functions
- Drawing class inheritance hierarchies
- Mapping module import dependencies
- Showing class structure with members
- Highlighting complexity hotspots with color coding
- Tracing data flow from entrypoints to sensitive functions

## When NOT to Use

- Querying the graph without visualization (use the `trailmark` skill)
- Mutation testing triage (use the `genotoxic` skill)
- Architecture diagrams not derived from code (draw by hand)

## Prerequisites

**trailmark** must be installed. If `uv run trailmark` fails, run:

```bash
uv tool install trailmark
# Python snippets: uv run --with trailmark python -   (a tool env is not importable)
```

**DO NOT** fall back to hand-writing Mermaid from source code reading. The
script uses Trailmark's parsed graph for accuracy. If installation fails,
report the error to the user.

## Version Gate

Check whether native v0.4 diagram support exists:

```bash
trailmark diagram --help 2>/dev/null || uv run trailmark diagram --help 2>/dev/null
```

If this succeeds, you may use `trailmark diagram`. If it fails, use
`uv run {baseDir}/scripts/diagram.py`, which keeps the older skill workflow
intact. Do not assume the native CLI exists on Trailmark 0.2.x.

---

## Quick Start

```bash
uv run {baseDir}/scripts/diagram.py \
    --target {targetDir} --language auto --type call-graph \
    --focus <function> --depth 2

# Trailmark 0.4.0+ equivalent after the Version Gate succeeds
uv run trailmark diagram \
    --target {targetDir} --language auto --type call-graph \
    --focus <function> --depth 2
```

Output is raw Mermaid text. Wrap in a fenced code block:

The rest: https://github.com/trailofbits/skills/blob/HEAD/plugins/trailmark/skills/diagramming-code/SKILL.md