---

name: understand description: Analyze a codebase to produce an interactive knowledge graph for understanding architecture, components, and relationships argument-hint: ["[path] [--full|--auto-update|--no-auto-update|--review|--language <lang>|--exclude <patterns>]"]

/understand

Analyze the current codebase and produce a knowledge-graph.json file in the project's data directory (.ua/, or the legacy .understand-anything/ when it already exists). 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 $UA_DIR/config.json)
  • --no-auto-update — Disable automatic graph updates (writes autoUpdate: false to $UA_DIR/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 $UA_DIR/config.json for consistency across incremental updates.
  • --exclude <patterns> — Comma-separated glob patterns for additional files/directories to exclude from analysis (e.g., --exclude "tests/*,docs/*"). These patterns take highest priority over built-in defaults and .understandignore rules. Supports gitignore syntax including ! negation.
  • 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 — the data directory (.ua/, or legacy .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.

     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:

   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."

1.7. Resolve the data directory $UA_DIR. All Understand-Anything artifacts live in the project's data directory. Resolve it once, now that $PROJECT_ROOT is known, and reuse $UA_DIR for every read and write in later phases:

UA_DIR="$PROJECT_ROOT/$([ -d "$PROJECT_ROOT/.understand-anything" ] && echo .understand-anything || echo .ua)"

This keeps the legacy .understand-anything/ directory when it already exists (existing projects keep working with no migration) and uses the new .ua/ otherwise. Because each phase may run in a fresh shell, treat $UA_DIR — like $PROJECT_ROOT — as a value you carry forward and substitute; re-resolve it with the line above if a later command block needs it in a new shell.

2. Get the current git commit hash:

   git rev-parse HEAD
   

3. Create the intermediate and temp output directories:

   mkdir -p "$UA_DIR/intermediate"
   mkdir -p "$UA_DIR/tmp"
   

3.1. Purge stale trash dirs. Phase 7 cleanup mvs scratch dirs into .trash-<timestamp>/ rather than rm -rfing 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:

find "$UA_DIR/" -maxdepth 1 -type d -name '.trash-*' -mtime +7 -exec rm -rf {} + 2>/dev/null || true

3.5. Auto-update configuration: - If --auto-update is in $ARGUMENTS: write {"autoUpdate": true} to $UA_DIR/config.json - If --no-auto-update is in $ARGUMENTS: write {"autoUpdate": false} to $UA_DIR/config.json - These flags only set the config — analysis proceeds normally regardless.

3.6. Language configuration: - Parse $ARGUMENTS for --language <lang> flag. If found, extract the language code. - Language code normalization: Map friendly names to ISO codes: - chinese → zh, japanese → ja, korean → ko, english → en, spanish → es, french → fr, german → de, portuguese → pt, russian → ru, arabic → ar, etc. - Locale variants: zh-TW, zh-HK, zh-CN, pt-BR, etc. are preserved as-is. - If --language is NOT specified: - Stored preference wins. If $UA_DIR/config.json has an outputLanguage field, set $OUTPUT_LANGUAGE to it and skip the rest. - Otherwise detect (first run only). Infer the predominant language of the user's conversation as an ISO 639-1 code ($DETECTED_LANG). If it is en or cannot be confidently determined, set $OUTPUT_LANGUAGE=en and proceed silently — no prompt (English users see no change). - If $DETECTED_LANG ≠ en, confirm once before analyzing: tell the user you detected <language> and ask whether to generate all content in it; they press Enter/"yes" to accept, or type another language code/name to override (normalize via the friendly-name map above). If running non-interactively (no reply possible), skip the wait, use $DETECTED_LANG, and print a one-line notice instead of blocking. - Persist the resolved $OUTPUT_LANGUAGE (including en) into config.json so it never re-prompts for this project. - If --language IS specified: - Update $UA_DIR/config.json with the new language: merge {"outputLanguage": "<lang>"} into existing config. - Store as $OUTPUT_LANGUAGE for use throughout all phases. - Language directive template: Store as $LANGUAGE_DIRECTIVE: markdown > **Language directive**: Generate all textual content (summaries, descriptions, tags, titles, languageNotes, languageLesson) in **{language}**. Maintain technical accuracy while using natural, native-level phrasing in the target language. Keep technical terms in English when no standard translation exists (e.g., "middleware", "hook", "barrel").

3.7. Exclude patterns: - Parse $ARGUMENTS for --exclude <patterns> flag. If found, extract the comma-separated patterns string. - Split on commas, trim whitespace from each pattern, and filter out empty entries. - St