understand-domain

name	understand-domain
description	Extract business domain knowledge from a codebase and generate an interactive domain flow graph. Works standalone (lightweight scan) or derives from an existing /understand knowledge graph.
argument-hint	["--full"]

/understand-domain

Extracts business domain knowledge — domains, business flows, and process steps — from a codebase and produces an interactive horizontal flow graph in the dashboard.

⚠️ IMPORTANT: You ARE the LLM. All analysis steps use you as the LLM. Do NOT call external APIs. When the skill says "dispatch a subagent" — use your platform's delegation mechanism.

How It Works

• If a knowledge graph already exists (.understand-anything/knowledge-graph.json), derives domain knowledge from it (cheap, no file scanning)
• If no knowledge graph exists, performs a lightweight scan: file tree + entry point detection + sampled files
• Use --full flag to force a fresh scan even if a knowledge graph exists

Instructions

Phase 0: Resolve PROJECT_ROOT

Set PROJECT_ROOT to the current working directory.

Worktree redirect. If PROJECT_ROOT is inside a git worktree (not the main checkout), redirect output to the main repository root. Worktrees managed by Claude Code are ephemeral — .understand-anything/ written there is destroyed when the session ends, taking the domain graph with it (issue #133). Detect a worktree by comparing git rev-parse --git-dir against git rev-parse --git-common-dir; in a normal checkout or submodule they resolve to the same path, in a worktree they differ and the parent of --git-common-dir is the main repo root.

COMMON_DIR=$(git -C "$PROJECT_ROOT" rev-parse --git-common-dir 2>/dev/null)
GIT_DIR=$(git -C "$PROJECT_ROOT" rev-parse --git-dir 2>/dev/null)
if [ -n "$COMMON_DIR" ] && [ -n "$GIT_DIR" ]; then
  COMMON_ABS=$(cd "$PROJECT_ROOT" && cd "$COMMON_DIR" 2>/dev/null && pwd -P)
  GIT_ABS=$(cd "$PROJECT_ROOT" && cd "$GIT_DIR" 2>/dev/null && pwd -P)
  if [ -n "$COMMON_ABS" ] && [ "$COMMON_ABS" != "$GIT_ABS" ]; then
    MAIN_ROOT=$(dirname "$COMMON_ABS")
    if [ -d "$MAIN_ROOT" ] && [ "${UNDERSTAND_NO_WORKTREE_REDIRECT:-0}" != "1" ]; then
      echo "[understand-domain] Detected git worktree at $PROJECT_ROOT"
      echo "[understand-domain] Redirecting output to main repo root: $MAIN_ROOT"
      echo "[understand-domain] (Set UNDERSTAND_NO_WORKTREE_REDIRECT=1 to keep PROJECT_ROOT as the worktree.)"
      PROJECT_ROOT="$MAIN_ROOT"
    fi
  fi
fi

Use $PROJECT_ROOT (not the bare CWD) for every reference to "the current project" / <project-root> in subsequent phases.

Important: do not assume the plugin root is simply two directories above the skill path string. In many installations ~/.agents/skills/understand-domain is a symlink into the real plugin checkout. Prefer runtime-provided plugin roots first (for Claude), then fall back to universal symlinks, skill symlink resolution, and common clone-based install paths.

Resolve the plugin root like this:

SKILL_REAL=$(realpath ~/.agents/skills/understand-domain 2>/dev/null || readlink -f ~/.agents/skills/understand-domain 2>/dev/null || echo "")
SELF_RELATIVE=$([ -n "$SKILL_REAL" ] && cd "$SKILL_REAL/../.." 2>/dev/null && pwd || echo "")
COPILOT_SKILL_REAL=$(realpath ~/.copilot/skills/understand-domain 2>/dev/null || readlink -f ~/.copilot/skills/understand-domain 2>/dev/null || echo "")
COPILOT_SELF_RELATIVE=$([ -n "$COPILOT_SKILL_REAL" ] && cd "$COPILOT_SKILL_REAL/../.." 2>/dev/null && pwd || echo "")

PLUGIN_ROOT=""
for candidate in \
  "${CLAUDE_PLUGIN_ROOT}" \
  "$HOME/.understand-anything-plugin" \
  "$SELF_RELATIVE" \
  "$COPILOT_SELF_RELATIVE" \
  "$HOME/.codex/understand-anything/understand-anything-plugin" \
  "$HOME/.opencode/understand-anything/understand-anything-plugin" \
  "$HOME/.pi/understand-anything/understand-anything-plugin" \
  "$HOME/understand-anything/understand-anything-plugin"; do
  if [ -n "$candidate" ] && [ -f "$candidate/package.json" ] && [ -f "$candidate/pnpm-workspace.yaml" ]; then
    PLUGIN_ROOT="$candidate"
    break
  fi
done

if [ -z "$PLUGIN_ROOT" ]; then
  echo "Error: Cannot find the understand-anything plugin root."
  echo "Checked:"
  echo "  - ${CLAUDE_PLUGIN_ROOT:-<unset CLAUDE_PLUGIN_ROOT>}"
  echo "  - $HOME/.understand-anything-plugin"
  echo "  - ${SELF_RELATIVE:-<unresolved path derived from ~/.agents/skills/understand-domain>}"
  echo "  - ${COPILOT_SELF_RELATIVE:-<unresolved path derived from ~/.copilot/skills/understand-domain>}"
  echo "  - $HOME/.codex/understand-anything/understand-anything-plugin"
  echo "  - $HOME/.opencode/understand-anything/understand-anything-plugin"
  echo "  - $HOME/.pi/understand-anything/understand-anything-plugin"
  echo "  - $HOME/understand-anything/understand-anything-plugin"
  echo "Make sure the plugin is installed correctly."
  exit 1
fi

Use $PLUGIN_ROOT for every reference to agent definitions in subsequent phases.

Phase 1: Detect Existing Graph

1. Check if $PROJECT_ROOT/.understand-anything/knowledge-graph.json exists
2. If it exists AND --full was NOT passed → proceed to Phase 3 (derive from graph)
3. Otherwise → proceed to Phase 2 (lightweight scan)

Phase 2: Lightweight Scan (Path 1)

The preprocessing script does NOT produce a domain graph — it produces raw material (file tree, entry points, exports/imports) so the domain-analyzer agent can focus on the actual domain analysis instead of spending dozens of tool calls exploring the codebase. Think of it as a cheat sheet: cheap Python preprocessing → expensive LLM gets a clean, small input → better results for less cost.

1. Run the preprocessing script bundled with this skill, passing $PROJECT_ROOT from Phase 0:

   python ./extract-domain-context.py "$PROJECT_ROOT"
   

   This outputs $PROJECT_ROOT/.understand-anything/intermediate/domain-context.json containing:
   • File tree (respecting .gitignore)
   • Detected entry points (HTTP routes, CLI commands, event handlers, cron jobs, exported handlers)
   • File signatures (exports, imports per file)
   • Code snippets for each entry point (signature + first few lines)
   • Project metadata (package.json, README, etc.)
2. Read the generated domain-context.json as context for Phase 4
3. Proceed to Phase 4

Phase 3: Derive from Existing Graph (Path 2)

1. Read $PROJECT_ROOT/.understand-anything/knowledge-graph.json
2. Format the graph data as structured context:
   • All nodes with their types, names, summaries, and tags
   • All edges with their types (especially calls, imports, contains)
   • All layers with their descriptions
   • Tour steps if available
3. This is the context for the domain analyzer — no file reading needed
4. Proceed to Phase 4

Phase 4: Domain Analysis

1. Read the domain-analyzer agent prompt from $PLUGIN_ROOT/agents/domain-analyzer.md
2. Dispatch a subagent with the domain-analyzer prompt + the context from Phase 2 or 3
3. The agent writes its output to $PROJECT_ROOT/.understand-anything/intermediate/domain-analysis.json

Phase 5: Validate and Save

1. Read the domain analysis output
2. Validate using the standard graph validation pipeline (the schema now supports domain/flow/step types)
3. If validation fails, log warnings but save what's valid (error tolerance)
4. Save to $PROJECT_ROOT/.understand-anything/domain-graph.json
5. Clean up $PROJECT_ROOT/.understand-anything/intermediate/domain-analysis.json and $PROJECT_ROOT/.understand-anything/intermediate/domain-context.json

Phase 6: Launch Dashboard

1. Auto-trigger /understand-dashboard to visualize the domain graph
2. The dashboard will detect domain-graph.json and show the domain view by default