Create diagrams with D2

Create a diagram from the most recent interaction context using D2. Generate a PNG image 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:

   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 D2 file to a temporary file using the foreground color.
4. Run D2 with --theme 200 if background mode is dark, or --theme 0 if light.
5. Output the result as a markdown image on its own line:

   ![description](/tmp/agent-diagram-XXXX.png)
   

# Use --theme 200 for dark, --theme 0 for light
d2 --theme 200 --pad 40 /tmp/agent-diagram-XXXX.d2 /tmp/agent-diagram-XXXX.png

D2 template

Use --theme 200 for dark or --theme 0 for light, based on the Emacs background mode. Apply the queried foreground color to style.font-color and style.stroke on nodes and edges.

direction: right

node1: Label {
  style.font-color: "#eeffff"
  style.fill: "#2d3748"
  style.stroke: "#eeffff"
}

node2: Label {
  style.font-color: "#eeffff"
  style.fill: "#2d3748"
  style.stroke: "#eeffff"
}

node1 -> node2: label {style.stroke: "#eeffff"; style.font-color: "#eeffff"}

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 --theme 200 for dark or --theme 0 for light. Always use --pad 40.
• Always use a timestamp in the filename (e.g., /tmp/agent-diagram-$(date +%s).png). Never use descriptive names.
• Set the queried foreground color on style.font-color and style.stroke for all nodes and edges so the diagram is readable on the user's Emacs background.
• Use meaningful fill colors to distinguish different types of elements.
• After D2 runs successfully, output a markdown image (![description](path)) on its own line.
• Choose an appropriate layout direction and structure for the data.
• Include labels on edges when they add clarity.
• If no diagrammable data exists in the recent context, inform the user.