PRP Diagram — Visual Supplement for a Plan

Input: $ARGUMENTS — a path to a plan/PRD markdown file. If blank, use the most recent file in $PRP_DIR/plans/.

One agent, one pass, no subagents. Read the plan, produce the diagrams a human wants beside it while absorbing it. Nothing else.

Resolve the store

# --- PRP store resolver (canonical; keep byte-identical across skills) ---
_gd="$(git rev-parse --path-format=absolute --git-common-dir 2>/dev/null)"
case "$_gd" in */.git) _root="${_gd%/.git}" ;; "") _root="$PWD" ;; *) _root="$_gd" ;; esac
_root="$(cd "$_root" && pwd -P)"
_name="$(basename "$_root" | tr '[:upper:]' '[:lower:]' | tr -cs 'a-z0-9' '-' | sed 's/^-*//;s/-*$//')"
PRP_DIR="${PRP_HOME:-$HOME/.prp}/${_name:-project}-$(printf %s "$_root" | git hash-object --stdin | cut -c1-8)"
mkdir -p "$PRP_DIR"; [ -f "$PRP_DIR/project.json" ] || printf '{"path": "%s", "name": "%s"}\n' "$_root" "${_name:-project}" > "$PRP_DIR/project.json"

Output path

<plan-basename>.diagrams.md — strip the plan filename's trailing .md, append .diagrams.md.

• Plan lives inside $PRP_DIR → write NEXT TO it (same directory).
• Plan lives anywhere else → write to $PRP_DIR/plans/ (mkdir -p "$PRP_DIR/plans").

Overwrite on re-run without asking — this is a derived artifact; the plan is the source of truth.

Content policy (strict)

The file contains ONLY:

1. A single title line: # <plan title> — Diagrams
2. Per diagram: one bold caption line (**<what this shows>**), then one ```mermaid fence.

No prose paragraphs, no recommendations, no analysis, no legend sections. Diagrams supplement the plan — they never editorialize it.

Choosing diagrams

Diagram only what the plan actually contains — never invent entities, flows, or states the plan doesn't describe. Skip any category the plan doesn't support.

Keep each diagram legible: ~40 nodes max — split into two diagrams rather than cram one. Mermaid syntax must be valid: prefer simple constructs over clever ones, and quote labels containing special characters (A["label (with) specials"]).

HTML alternative

Only when the user explicitly asks for .html: write a single self-contained html file at the same path with .diagrams.html instead. Same content policy — a title, then per diagram a caption and a <pre class="mermaid"> block. Do NOT embed or link mermaid.js (no CDN, no scripts) — the consuming UI provides the renderer; add an html comment noting that.

Report

One line to the user: the expanded absolute output path plus which diagram types were produced.