understand

What this skill does

# /understand

Analyze the current codebase and produce a `knowledge-graph.json` file in `.understand-anything/`. This file powers the interactive dashboard for exploring the project's architecture.

## Options

- `$ARGUMENTS` may contain:
  - `--full` — Force a full rebuild, ignoring any existing graph
  - `--auto-update` — Enable automatic graph updates on commit (writes `autoUpdate: true` to `.understand-anything/config.json`)
  - `--no-auto-update` — Disable automatic graph updates (writes `autoUpdate: false` to `.understand-anything/config.json`)
  - `--review` — Run full LLM graph-reviewer instead of inline deterministic validation
  - `--language <lang>` — Generate all textual content (summaries, descriptions, tags, titles, languageNotes, languageLesson) in the specified language. Accepts ISO 639-1 codes (`zh`, `ja`, `ko`, `en`, `es`, `fr`, `de`, etc.) or friendly names (`chinese`, `japanese`, `korean`, `english`, `spanish`, etc.). Locale variants supported: `zh-TW`, `zh-HK`, etc. Defaults to `en` (English). Stores preference in `.understand-anything/config.json` for consistency across incremental updates.
  - A directory path (e.g. `/path/to/repo` or `../other-project`) — Analyze the given directory instead of the current working directory

---

## Progress Reporting

Throughout execution, report progress to the user at each phase transition and during batch processing. This keeps users informed on large codebases where analysis can take a long time.

- **Phase transitions:** At the start of each phase, print a status line:
  > `[Phase N/7] <phase name>...`
  >
  > Example: `[Phase 2/7] Analyzing files (12 batches)...`

- **Batch progress:** During Phase 2, report each batch with its index and total:
  > `Analyzing batch X/N (files: foo.ts, bar.ts, ...)` (list up to 3 filenames, then `...` if more)

- **Phase completion:** When a phase finishes, briefly confirm:
  > `Phase N complete. <one-line summary of result>`
  >
  > Example: `Phase 1 complete. Found 247 files across 3 languages.`

---

## Phase 0 — Pre-flight

Determine whether to run a full analysis or incremental update.

1. **Resolve `PROJECT_ROOT`:**
   - Parse `$ARGUMENTS` for a non-flag token (any argument that does not start with `--`). If found, treat it as the target directory path.
     - If the path is relative, resolve it against the current working directory.
     - Verify the resolved path exists and is a directory (run `test -d <path>`). If it does not exist or is not a directory, report an error to the user and **STOP**.
     - Set `PROJECT_ROOT` to the resolved absolute path.
   - If no directory path argument is found, 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 knowledge 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] Detected git worktree at $PROJECT_ROOT"
           echo "[understand] Redirecting output to main repo root: $MAIN_ROOT"
           echo "[understand] (Set UNDERSTAND_NO_WORKTREE_REDIRECT=1 to keep PROJECT_ROOT as the worktree.)"
           PROJECT_ROOT="$MAIN_ROOT"
         fi
       fi
     fi
     ```

     Set `UNDERSTAND_NO_WORKTREE_REDIRECT=1` if you intentionally want a per-worktree graph (rare — most users want the redirect).
1.5. **Ensure the plugin is built.** Later phases invoke Node scripts that import `@understand-anything/core`. On a fresh install `packages/core/dist/` does not exist yet — build once.

   **Important:** do **not** assume the plugin root is simply two directories above the skill path string. In many installations `~/.agents/skills/understand` 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=$(realpath ~/.agents/skills/understand 2>/dev/null || readlink -f ~/.agents/skills/understand 2>/dev/null || echo "")
   SELF_RELATIVE=$([ -n "$SKILL_REAL" ] && cd "$SKILL_REAL/../.." 2>/dev/null && pwd || echo "")
   COPILOT_SKILL_REAL=$(realpath ~/.copilot/skills/understand 2>/dev/null || readlink -f ~/.copilot/skills/understand 2>/dev/null || echo "")
   COPILOT_SELF_RELATIVE=$([ -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>}"
     echo "  - ${COPILOT_SELF_RELATIVE:-<unresolved path derived from ~/.copilot/skills/understand>}"
     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

   if [ ! -f "$PLUGIN_ROOT/packages/core/dist/index.js" ]; then
     cd "$PLUGIN_ROOT" && (pnpm install --frozen-lockfile 2>/dev/null || pnpm install) && pnpm --filter @understand-anything/core build
   fi
   ```

   If `pnpm` is missing, report to the user: "Install Node.js ≥ 22 and pnpm ≥ 10, then re-run `/understand`."

2. Get the current git commit hash:
   ```bash
   git rev-parse HEAD
   ```
3. Create the intermediate and temp output directories:
   ```bash
   mkdir -p $PROJECT_ROOT/.understand-anything/intermediate
   mkdir -p $PROJECT_ROOT/.understand-anything/tmp
   ```
3.1. **Purge stale trash dirs.** Phase 7 cleanup `mv`s scratch dirs into `.trash-<timestamp>/` rather than `rm -rf`ing them directly (see issue #301), so that destructive-action gates on hardened hosts don't trip on just-created paths. Reclaim the space here once the trash is older than 7 days — by this point any freshness-window check has long since stopped caring about those dirs:
   ```bash
   find $PROJECT_ROOT/.understand-anything/ -maxdepth 1 -type d -name '.trash-*' -mtime +7 -exec rm -rf {} + 2>/dev/null || true
   ```
3.5. **Auto-update configuration:**
    - If `