Understand Domain

# /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.

## 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.

```bash
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:

```bash
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 \