fenix-skills/skills/mermaid/SKILL.md

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---
name: mermaid
description: 'This skill should be used when the user invokes "/mermaid" to create a diagram from the current context using Mermaid and output the resulting image path.'
tools: Bash
disable-model-invocation: true
---
# Create diagrams with Mermaid
Create a diagram from the most recent interaction context using Mermaid. Generate a PNG image with a transparent background and output it as a markdown image so it renders inline.
## How to create a diagram
1. Extract or derive diagrammable data from the current context.
2. If the Emacs foreground color and background mode are not already known from a previous diagram in this session, query them:
```sh
emacsclient --eval '(face-foreground (quote default))'
emacsclient --eval '(frame-parameter nil (quote background-mode))'
```
The first returns a hex color like `"#eeffff"`. The second returns `dark` or `light`. Reuse both for all subsequent diagrams.
3. Write a Mermaid file to a temporary file.
4. Write a JSON config file that overrides theme variables with the queried foreground color. Set `"theme"` to `"dark"` or `"default"` based on the background mode.
5. Run `mmdc` with `-t dark` if background mode is `dark`, or `-t default` if `light`.
6. Output the result as a markdown image on its own line:
```
![description](/tmp/agent-diagram-XXXX.png)
```
```sh
# Use -t dark for dark, -t default for light
PUPPETEER_EXECUTABLE_PATH=/opt/homebrew/bin/chromium mmdc \
-i /tmp/agent-diagram-XXXX.mmd \
-o /tmp/agent-diagram-XXXX.png \
-t dark -b transparent --scale 2 \
--configFile /tmp/agent-diagram-XXXX-config.json
```
## Mermaid config template
Write this JSON config file to apply the Emacs foreground color. Replace `#eeffff` with the queried color. Set `"theme"` to `"dark"` or `"default"` based on the Emacs background mode.
```json
{
"theme": "dark",
"themeVariables": {
"primaryTextColor": "#eeffff",
"secondaryTextColor": "#eeffff",
"tertiaryTextColor": "#eeffff",
"primaryBorderColor": "#eeffff",
"lineColor": "#eeffff",
"textColor": "#eeffff",
"actorTextColor": "#eeffff",
"actorBorder": "#eeffff",
"signalColor": "#eeffff",
"signalTextColor": "#eeffff",
"labelTextColor": "#eeffff",
"loopTextColor": "#eeffff",
"noteTextColor": "#eeffff",
"noteBorderColor": "#eeffff",
"sectionTextColor": "#eeffff",
"titleColor": "#eeffff"
}
}
```
## Mermaid diagram template
```mermaid
sequenceDiagram
participant a as Alice
participant b as Bob
a->>b: Hello
b-->>a: Hi back
```
## Rules
- Query the Emacs foreground color once per session and reuse it for all subsequent diagrams. Only query again if the color is not already known.
- Query the Emacs background mode once per session via `(frame-parameter nil 'background-mode)`. Use `-t dark` for `dark` or `-t default` for `light`. Always use `-b transparent --scale 2`.
- Always use `PUPPETEER_EXECUTABLE_PATH=/opt/homebrew/bin/chromium` when invoking `mmdc`.
- Always write a JSON config file with `themeVariables` set to the queried foreground color and pass it via `--configFile`.
- Always use a timestamp in the filename (e.g., `/tmp/agent-diagram-$(date +%s).png`). Never use descriptive names.
- After mmdc runs successfully, output a markdown image (`![description](path)`) on its own line.
- Choose an appropriate diagram type for the data (sequence, flowchart, class, state, er, gantt, etc.).
- Include a title when it adds clarity.
- If no diagrammable data exists in the recent context, inform the user.