Extract or derive diagrammable data from the current context.
If the Emacs foreground color and background mode are not already known from a previous diagram in this session, query them:
```
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.
Write a Mermaid file to a temporary file.
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.
Run mmdc with -t dark if background mode is dark, or -t default if light.
Output the result as a markdown image on its own line:
```
![description](/tmp/agent-diagram-XXXX.png)
```

# 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.

{
  "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

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.

mermaid

Create diagrams with Mermaid

How to create a diagram

More from xenodium/emacs-skills

emacsclient

describe

dired

open

select

highlight