feat(install): level-aware casan init + merge-safe adoption + hub guardrail

Answers the 3 adoption questions (Plan-21 follow-up):

1) LEVEL SELECTION (4 packaging levels, packaging/levels.json):
   - install.sh --level core|devkit; platform refused (preview service),
     enterprise refused (future). Level recorded in .casan-level.
   - casan init --level 1..4: L1=gate+Plan-20 hooks only; L2=+CI+domain-pack;
     L3=L2 base+preview note; L4=refused. New `casan level show|set`.
   - levels.json core now includes adapters/ + schemas/ + install scripts.

2) EXISTING SHELLS (agents/skills): init MERGES Plan-20 hooks into an existing
   .claude/settings.json and .codex/{hooks.json,config.toml} idempotently
   instead of clobbering — preserves the project's own hooks/agents/skills and
   unrelated keys. Re-running never duplicates the CASAN hook.

3) NO RE-INDEX / NO SHELL REWRITE: init only adds config; it does not parse or
   index code and does not rewrite the project shell.

Safety fixes after a test accidentally ran init in the real repo:
   - launcher shim now SELF-LOCATES its install from its own path (no ambient
     CASAN_HOME cross-talk).
   - casan init REFUSES to adopt a CASAN source hub into itself (--force to
     override), so the Plan-20 hooks can't block the developing agent.
   - test always runs init inside throwaway dirs; +source-hub guard test.

hybrid-install-tests.sh: 41/41 PASS.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

bin/casan

@@ -42,7 +42,8 @@ casan — CASAN governance harness CLI ($(version))
 Usage: casan <command> [args]
 
 Commands:
-  init [--project id] [--client all]   Adopt CASAN into THIS project (config only, hybrid model)
+  init [--level 1..4] [--project id]   Adopt CASAN into THIS project (config only, hybrid model)
+  level <show|set 1..4>                Show / change the project's packaging level
   verify-harness                       Verify the resolved harness matches the project pin
   run <in> <out> [action] [-- cmd...]  Run a step through the harness (H4→H5→H6→exec→H4-out)
   gate                                 Run the full CI harness gate (all suites)
@@ -73,6 +74,15 @@ case "$cmd" in
   verify-harness)
     [[ -f "$DEVKIT_ROOT/casan-init.py" ]] || { echo "casan: verify-harness requires the casan-devkit package" >&2; exit 1; }
     exec python3 "$DEVKIT_ROOT/casan-init.py" verify "$@" ;;
+  level)
+    [[ -f "$DEVKIT_ROOT/casan-init.py" ]] || { echo "casan: level requires the casan-devkit package" >&2; exit 1; }
+    sub="${1:-show}"; shift || true
+    case "$sub" in
+      show) exec python3 "$DEVKIT_ROOT/casan-init.py" level --show "$@" ;;
+      set)  n="${1:-devkit}"; shift || true
+            exec python3 "$DEVKIT_ROOT/casan-init.py" init --level "$n" "$@" ;;
+      *) echo "casan: usage: casan level <show|set <1..4>>" >&2; exit 64 ;;
+    esac ;;
   run)        exec bash "$BASH_DIR/casan-harness.sh" "$@" ;;
   gate)
     if [[ -n "${CASAN_PROJECT_MANIFEST:-}${CASAN_PROJECT_ID:-}" ]]; then

docs/casan/CASAN_INSTALL_HYBRID.md

@@ -21,12 +21,26 @@ sh install.sh                 # macOS/Linux
 pwsh .\install.ps1            # Windows
 ```
 
+Chọn **level đóng gói** để cài (theo `packaging/levels.json`):
+
+```bash
+sh install.sh --level core      # L1: harness + gates + CLI (casan run/gate/verify)
+sh install.sh --level devkit    # L2 (mặc định): + adoption tooling (casan init, CI, domain-pack)
+sh install.sh --level platform  # L3 preview: từ chối — là service, deploy riêng
+sh install.sh --level enterprise# L4 future: từ chối (chưa ship)
+```
+
+Levels là cumulative (devkit ⊃ core). `casan init` là tính năng của **L2 (devkit)**;
+cài `--level core` sẽ không có `casan init` (báo rõ ràng).
+
 Installer sẽ:
 
 - Copy harness vào `$CASAN_HOME/versions/<version>` (mặc định `~/.casan`,
   Windows: `%LOCALAPPDATA%\casan`) và trỏ `current` vào version đó.
 - Ghi **hash toàn vẹn** của gate-code (`.harness-hash`) — mỏ neo cho pin+verify.
-- Tạo launcher `casan` và đưa lên PATH (`~/.local/bin` hoặc `$CASAN_HOME/bin`).
+- Ghi level đã cài vào `.casan-level`.
+- Tạo launcher `casan` (tự định vị install của chính nó) và đưa lên PATH
+  (`~/.local/bin` hoặc `$CASAN_HOME/bin`).
 
 > Windows cần **Git for Windows (Git Bash)** để *chạy* harness (xem
 > [CASAN_AGENTIC_CLIENTS_WINDOWS.md](CASAN_AGENTIC_CLIENTS_WINDOWS.md)) — không
@@ -39,11 +53,25 @@ cục bộ), `CASAN_DIST_URL` (tải tarball), `CASAN_NO_PATH_LINK=1` (không t
 
 ```bash
 cd <dự-án-của-bạn>
-casan init                       # project id lấy theo tên thư mục
-# hoặc:
-casan init --project my-app --client all --mode observe
+casan init                       # project id lấy theo tên thư mục, level=devkit
+# hoặc chọn level áp dụng cho project:
+casan init --level 1 --project my-app   # L1: chỉ gate + hook Plan-20
+casan init --level 2 --project my-app   # L2 (mặc định): + CI workflow + domain-pack
+casan level show                        # xem level đã cài + level project
+casan level set 2                       # đổi level project (không cần init lại)
 ```
 
+**Áp dụng cho dự án ĐÃ có vỏ (agents/skills/hook sẵn):** an toàn.
+- `init` **KHÔNG index/parse code, KHÔNG sửa source, KHÔNG dựng lại vỏ** — chỉ thêm config.
+- Hook được **MERGE** idempotent vào `.claude/settings.json` / `.codex/hooks.json`
+  hiện có (giữ nguyên hook/agents/skills/khóa khác của bạn), không ghi đè. Chạy
+  `init` nhiều lần không nhân đôi hook.
+- **Guardrail:** `init` **từ chối** khi target chính là một CASAN source hub (để
+  không tự chặn agent đang phát triển CASAN); dùng `--force` nếu thực sự cần.
+
+`--level 3` (platform) chỉ áp base L2 + nhắc rằng platform là service deploy riêng;
+`--level 4` (enterprise) bị từ chối (chưa ship).
+
 `casan init` chỉ ghi **config per-project** (không copy harness):
 
 | File | Vai trò |

docs/plans/CASAN_PLAN_21_HYBRID_INSTALL.md

@@ -1,7 +1,7 @@
 # CASAN Plan-21 — Hybrid Global Install + `casan init`
 
 > Ngày lập: 2026-07-23  
-> Trạng thái: **IMPLEMENTED (MVP) — global install + `casan init` + pin/verify xanh (21/21 test)**  
+> Trạng thái: **IMPLEMENTED — global install + `casan init` + pin/verify + level-aware + merge-safe (41/41 test)**  
 > Liên quan: [Plan-20](CASAN_PLAN_20_AGENTIC_CLIENT_INTEGRATION.md) (adapter/hook là base phổ quát), [CASAN_INSTALL_HYBRID.md](../casan/CASAN_INSTALL_HYBRID.md)
 
 ## 1. Mục tiêu
@@ -42,9 +42,23 @@ harness global thao tác đúng trên state của dự án hiện tại.
 | Integrity hash primitive | `packages/casan-harness/scripts/python/harness_hash.py` |
 | `casan init` / `verify` | `packages/casan-devkit/casan-init.py` |
 | CLI wiring | `bin/casan` (`init`, `verify-harness`) |
-| Acceptance suite | `packages/casan-devkit/tests/hybrid-install-tests.sh` — **21/21 PASS** |
+| Acceptance suite | `packages/casan-devkit/tests/hybrid-install-tests.sh` — **41/41 PASS** |
 | Adoption doc | `docs/casan/CASAN_INSTALL_HYBRID.md` |
 
+### Level selection (4 packaging levels) & safe adoption
+
+- `install.sh --level core|devkit` (driven by `packaging/levels.json`); `platform`
+  refused as a preview SERVICE, `enterprise` refused (future). Level recorded in
+  `.casan-level`; launcher self-locates its own install (no cross-home talk).
+- `casan init --level 1..4`: L1 = gate + Plan-20 hooks only; L2 = + CI workflow +
+  domain-pack; L3 = L2 base + preview note; L4 = refused. `casan level show`/`set`.
+- **Merge, not clobber:** `init` merges Plan-20 hooks into an existing
+  `.claude/settings.json` / `.codex/{hooks.json,config.toml}` idempotently,
+  preserving the project's own hooks/agents/skills. Never re-indexes or rewrites
+  the project shell.
+- **Source-hub guardrail:** `init` refuses to adopt a CASAN source hub into itself
+  (would block the developing agent); `--force` overrides.
+
 ## 5. Definition of Done
 
 - ✅ `install.sh` cài harness + launcher + integrity hash từ checkout cục bộ.

install.ps1

@@ -92,7 +92,12 @@ $binDir = Join-Path $CasanHome 'bin'
 New-Item -ItemType Directory -Force -Path $binDir | Out-Null
 $launcherPs1 = @'
 $ErrorActionPreference = "Stop"
-$CasanHome = if ($env:CASAN_HOME) { $env:CASAN_HOME } else { Join-Path $env:LOCALAPPDATA "casan" }
+# Self-locate THIS install from the launcher's own path (<home>\bin\casan.ps1) so a
+# specific launcher always uses ITS install regardless of any ambient CASAN_HOME.
+$selfHome = Split-Path -Parent (Split-Path -Parent $MyInvocation.MyCommand.Path)
+if ((Test-Path (Join-Path $selfHome "current")) -or (Test-Path (Join-Path $selfHome "versions"))) {
+  $CasanHome = $selfHome
+} elseif ($env:CASAN_HOME) { $CasanHome = $env:CASAN_HOME } else { $CasanHome = Join-Path $env:LOCALAPPDATA "casan" }
 $cur = Join-Path $CasanHome "current"
 if (-not (Test-Path $cur)) { Write-Error "casan: no install at $cur (run install.ps1)"; exit 1 }
 $env:CASAN_HARNESS_ROOT = Join-Path $cur "packages\casan-harness"

install.sh

@@ -15,12 +15,34 @@
 set -eu
 
 CASAN_HOME="${CASAN_HOME:-$HOME/.casan}"
+LEVEL="${CASAN_LEVEL:-devkit}"   # core | devkit  (platform=preview service, enterprise=future)
+
+# Parse flags (also accept `--level X`, e.g. `... | sh -s -- --level core`).
+while [ "$#" -gt 0 ]; do
+  case "$1" in
+    --level) LEVEL="$2"; shift 2 ;;
+    --level=*) LEVEL="${1#*=}"; shift ;;
+    -h|--help) sed -n '2,12p' "$0" 2>/dev/null; exit 0 ;;
+    *) shift ;;
+  esac
+done
 
 log()  { printf '[casan-install] %s\n' "$1"; }
 die()  { printf '[casan-install] ERROR: %s\n' "$1" >&2; exit 1; }
 
 command -v python3 >/dev/null 2>&1 || die "python3 is required on PATH."
 
+# Levels are cumulative (packaging/levels.json is the source of truth). The tool
+# installer handles the two ADOPT-INTO-PROJECT levels; L3/L4 are separate.
+case "$LEVEL" in
+  core|devkit) ;;
+  platform)
+    die "Level 3 (platform) is a PREVIEW service, not a per-project tool install. Install the CLI base with '--level devkit', then deploy the platform separately (scripts/package-release.sh platform, docs/packaging)." ;;
+  enterprise)
+    printf '[casan-install] Level 4 (enterprise) is FUTURE / not shipped — refusing (see packaging/levels.json).\n' >&2; exit 3 ;;
+  *) die "unknown --level '$LEVEL' (valid: core | devkit)." ;;
+esac
+
 # ── 1) Locate the source (local checkout, explicit CASAN_SRC, or a dist tarball)
 SRC=""
 CLEANUP=""
@@ -50,6 +72,7 @@ fi
 VERSION="$(cat "$SRC/VERSION" 2>/dev/null || echo "0.0.0")"
 log "source   : $SRC"
 log "version  : $VERSION"
+log "level    : $LEVEL (core=harness+CLI, devkit=+adoption tooling)"
 log "install  : $CASAN_HOME"
 
 # ── 2) Copy harness + devkit + CLI into a versioned dir ──────────────────────
@@ -67,11 +90,21 @@ copy_tree() { # <relpath>
     cp -R "$SRC/$1/." "$DEST/$1/"
   fi
 }
+# L1 core: harness + CLI + installer + level manifest.
 copy_tree "packages/casan-harness"
-copy_tree "packages/casan-devkit"
 cp "$SRC/bin/casan" "$DEST/bin/casan"
 chmod +x "$DEST/bin/casan"
 cp "$SRC/VERSION" "$DEST/VERSION" 2>/dev/null || printf '%s\n' "$VERSION" > "$DEST/VERSION"
+for f in install.sh install.ps1; do [ -f "$SRC/$f" ] && cp "$SRC/$f" "$DEST/$f"; done
+mkdir -p "$DEST/packaging"; [ -f "$SRC/packaging/levels.json" ] && cp "$SRC/packaging/levels.json" "$DEST/packaging/levels.json"
+
+# L2 devkit: adoption tooling (templates, domain-pack, casan init, package-release).
+if [ "$LEVEL" = "devkit" ]; then
+  copy_tree "packages/casan-devkit"
+  mkdir -p "$DEST/scripts"; [ -f "$SRC/scripts/package-release.sh" ] && cp "$SRC/scripts/package-release.sh" "$DEST/scripts/package-release.sh"
+  [ -d "$SRC/docs/packaging" ] && { mkdir -p "$DEST/docs"; cp -R "$SRC/docs/packaging" "$DEST/docs/packaging"; }
+fi
+printf '%s\n' "$LEVEL" > "$DEST/.casan-level"
 
 # Prune stray caches the copy may have carried.
 find "$DEST" -name '__pycache__' -type d -prune -exec rm -rf {} + 2>/dev/null || true
@@ -92,7 +125,15 @@ cat > "$CASAN_HOME/bin/casan" <<'LAUNCH'
 #!/usr/bin/env bash
 # CASAN global launcher — resolves the shared harness and the CURRENT project.
 set -uo pipefail
-CASAN_HOME="${CASAN_HOME:-$HOME/.casan}"
+# Self-locate THIS install from the launcher's own path (…/<home>/bin/casan) so
+# invoking a specific launcher always uses ITS install, regardless of any ambient
+# CASAN_HOME env. Fall back to CASAN_HOME/$HOME only if self-resolution fails.
+_self="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+if [[ -d "$_self/current" || -d "$_self/versions" ]]; then
+  CASAN_HOME="$_self"
+else
+  CASAN_HOME="${CASAN_HOME:-$HOME/.casan}"
+fi
 CUR="$CASAN_HOME/current"
 [[ -d "$CUR" ]] || { echo "casan: no install at $CUR (run install.sh)" >&2; exit 1; }
 export CASAN_HARNESS_ROOT="$CUR/packages/casan-harness"
@@ -127,6 +168,10 @@ else
   log "launcher : $CASAN_HOME/bin/casan"
   log "add to PATH:  export PATH=\"$CASAN_HOME/bin:\$PATH\"   (add to your shell rc)"
 fi
-log "next: cd <your-project> && casan init"
+if [ "$LEVEL" = "devkit" ]; then
+  log "next: cd <your-project> && casan init   (adopt CASAN, config only)"
+else
+  log "level core installed: 'casan run/gate/verify' available. Re-run with --level devkit to get 'casan init'."
+fi
 
 [ -n "$CLEANUP" ] && rm -rf "$CLEANUP" || true

packages/casan-devkit/casan-init.py

@@ -34,11 +34,47 @@ import time
 
 PROJECT_RE = re.compile(r"^[a-z][a-z0-9-]{1,62}$")
 
+# Packaging levels (docs/packaging/CASAN_PACKAGING_PLAN.md, packaging/levels.json).
+# Cumulative: devkit⊃core, platform⊃devkit, enterprise⊃platform.
+LEVEL_NAME = {"1": "core", "2": "devkit", "3": "platform", "4": "enterprise",
+              "core": "core", "devkit": "devkit", "platform": "platform", "enterprise": "enterprise"}
+LEVEL_NUM = {"core": 1, "devkit": 2, "platform": 3, "enterprise": 4}
+
 
 def now_iso():
     return time.strftime("%Y-%m-%dT%H:%M:%SZ", time.gmtime())
 
 
+def devkit_root():
+    return os.path.dirname(os.path.abspath(__file__))
+
+
+def _copy_if_absent(src, dst, created_rel, target, created):
+    if not os.path.exists(src) or os.path.exists(dst):
+        return False
+    os.makedirs(os.path.dirname(dst), exist_ok=True)
+    with open(src, "rb") as fh:
+        data = fh.read()
+    with open(dst, "wb") as fh:
+        fh.write(data)
+    created.append(os.path.relpath(dst, target))
+    return True
+
+
+def _copy_tree_missing(src_dir, dst_dir, target, created):
+    if not os.path.isdir(src_dir):
+        return 0
+    n = 0
+    for dp, _dn, fns in os.walk(src_dir):
+        rel = os.path.relpath(dp, src_dir)
+        for fn in fns:
+            s = os.path.join(dp, fn)
+            d = os.path.join(dst_dir, rel, fn) if rel != "." else os.path.join(dst_dir, fn)
+            if _copy_if_absent(s, d, None, target, created):
+                n += 1
+    return n
+
+
 def resolve_harness(explicit):
     for cand in (explicit, os.environ.get("CASAN_HARNESS_ROOT")):
         if cand and os.path.isdir(os.path.join(cand, "scripts", "bash")):
@@ -121,6 +157,101 @@ def _copy_template(src, dst, backups):
         return False
 
 
+def _load_json_or(path, default):
+    try:
+        with open(path, "r", encoding="utf-8") as fh:
+            return json.load(fh)
+    except (OSError, ValueError):
+        return default
+
+
+def _backup_once(path, backups):
+    bak = path + ".casan-bak"
+    if os.path.exists(path) and not os.path.exists(bak):
+        with open(path, "r", encoding="utf-8", errors="replace") as fh:
+            old = fh.read()
+        with open(bak, "w", encoding="utf-8") as fh:
+            fh.write(old)
+        backups.append(bak)
+
+
+def _has_marker_hook(groups, marker):
+    if not isinstance(groups, list):
+        return False
+    for g in groups:
+        if not isinstance(g, dict):
+            continue
+        for h in g.get("hooks", []) or []:
+            if isinstance(h, dict) and marker in str(h.get("command", "")):
+                return True
+    return False
+
+
+def merge_json_hooks(target_file, template_file, marker, backups):
+    """MERGE the template's hook groups into an existing hooks JSON without
+    clobbering the user's own hooks/agents/skills config. Idempotent by `marker`:
+    re-running never duplicates the CASAN hook. Returns created|merged|unchanged|None."""
+    tmpl = _load_json_or(template_file, None)
+    if not isinstance(tmpl, dict):
+        return None
+    existed = os.path.exists(target_file)
+    doc = _load_json_or(target_file, {}) if existed else {}
+    if not isinstance(doc, dict):
+        doc = {}
+    hooks = doc.get("hooks")
+    if not isinstance(hooks, dict):
+        hooks = {}
+        doc["hooks"] = hooks
+    changed = not existed
+    for event, groups in (tmpl.get("hooks") or {}).items():
+        cur = hooks.get(event)
+        if not isinstance(cur, list):
+            cur = []
+            hooks[event] = cur
+        if _has_marker_hook(cur, marker):
+            continue
+        cur.extend(groups if isinstance(groups, list) else [])
+        changed = True
+    for k, v in tmpl.items():  # carry template scalars (e.g. "version") if absent
+        if k != "hooks" and k not in doc:
+            doc[k] = v
+            changed = True
+    if changed:
+        _backup_once(target_file, backups)
+        os.makedirs(os.path.dirname(target_file), exist_ok=True)
+        with open(target_file, "w", encoding="utf-8") as fh:
+            fh.write(json.dumps(doc, ensure_ascii=False, indent=2) + "\n")
+    return ("created" if not existed else "merged") if changed else "unchanged"
+
+
+def merge_codex_config(target_file, mode, integration_mode, backups):
+    """Append a CASAN [casan] section (and, only if absent, a [hooks] enabler) to
+    an existing .codex/config.toml without duplicating tables. stdlib-only; no TOML
+    writer needed. Idempotent by the '[casan]' marker."""
+    casan_block = (
+        "\n# CASAN Plan-20 (added by casan init)\n"
+        "[casan]\n"
+        'enforcement_mode = "%s"\n'
+        'integration_mode = "%s"\n' % (mode, integration_mode)
+    )
+    hooks_block = "\n[hooks]\nenabled = true\nproject_hooks = true\n"
+    if not os.path.exists(target_file):
+        os.makedirs(os.path.dirname(target_file), exist_ok=True)
+        with open(target_file, "w", encoding="utf-8") as fh:
+            fh.write("# CASAN Plan-20 Codex config (created by casan init)\n"
+                     + hooks_block + casan_block)
+        return "created"
+    with open(target_file, "r", encoding="utf-8", errors="replace") as fh:
+        cur = fh.read()
+    if "[casan]" in cur:
+        return "unchanged"
+    _backup_once(target_file, backups)
+    add = ("" if "[hooks]" in cur else hooks_block) + casan_block
+    with open(target_file, "w", encoding="utf-8") as fh:
+        fh.write(cur.rstrip() + "\n" + add)
+    return "merged"
+
+
 def cmd_init(args):
     harness = resolve_harness(args.harness)
     if not harness:
@@ -132,11 +263,37 @@ def cmd_init(args):
         sys.stderr.write("casan init: target is not a directory: %s\n" % target)
         return 66
 
+    # Guardrail: refuse to adopt a CASAN SOURCE HUB into itself. Installing the
+    # Plan-20 PreToolUse hook into the CASAN repo would block the very agent
+    # developing CASAN (no admission => deny). Detect the hub by the harness
+    # source living inside the target. Override with --force for the rare
+    # intentional case.
+    hub_marker = os.path.join(target, "packages", "casan-harness", "scripts", "bash", "casan-harness.sh")
+    if os.path.exists(hub_marker) and not args.force:
+        sys.stderr.write(
+            "casan init: target looks like a CASAN SOURCE HUB (%s exists) — refusing to "
+            "adopt CASAN into itself (the Plan-20 hooks would block your own agent). "
+            "Use --force only if you really mean to.\n" % os.path.relpath(hub_marker, target))
+        return 65
+
     project = args.project or re.sub(r"[^a-z0-9-]", "-", os.path.basename(target).lower()).strip("-")
     if not PROJECT_RE.match(project):
         sys.stderr.write("casan init: --project must match ^[a-z][a-z0-9-]{1,62}$ (got %r)\n" % project)
         return 64
 
+    # Packaging level to adopt into the project.
+    lvl_name = LEVEL_NAME.get(str(args.level).lower())
+    if not lvl_name:
+        sys.stderr.write("casan init: --level must be 1..4 or core|devkit|platform|enterprise\n")
+        return 64
+    lvl = LEVEL_NUM[lvl_name]
+    if lvl == 4:
+        sys.stderr.write("casan init: Level 4 (enterprise) is FUTURE / not shipped — refusing "
+                         "(no fake-complete adoption). See packaging/levels.json.\n")
+        return 3
+    preview = (lvl == 3)   # platform is a separate preview SERVICE; init applies the L2 base
+    apply_devkit = (lvl >= 2)
+
     clients = ["claude", "codex"] if args.client == "all" else [args.client]
     version = harness_version(harness)
     hhash, hsource = compute_harness_hash(harness)
@@ -157,6 +314,8 @@ def cmd_init(args):
         "clients": clients,
         "harness_version": version,
         "adoption_model": "hybrid-global",
+        "target_level": lvl,
+        "target_level_name": lvl_name,
     }
     p = os.path.join(cfg_dir, "config.json")
     _write(p, json.dumps(cfg, ensure_ascii=False, indent=2) + "\n", backups); created_add(p)
@@ -192,18 +351,46 @@ def cmd_init(args):
     if not os.path.exists(gi):
         _write(gi, "# CASAN runtime state — do not commit\nlogs/\nstate/\n", backups); created_add(gi)
 
-    # ── Plan-20 client hooks from the harness adapters ──
+    # ── Plan-20 client hooks — MERGED into any existing config, never clobbered.
+    # A project that already has a shell (.claude/agents, skills, its own hooks)
+    # keeps everything; CASAN hooks are added idempotently.
     ad = os.path.join(harness, "adapters")
+    merges = {}
     if "claude" in clients:
-        if _copy_template(os.path.join(ad, "claude-code", "settings.template.json"),
-                          os.path.join(target, ".claude", "settings.json"), backups):
-            created_add(os.path.join(target, ".claude", "settings.json"))
+        dst = os.path.join(target, ".claude", "settings.json")
+        r = merge_json_hooks(dst, os.path.join(ad, "claude-code", "settings.template.json"),
+                             "claude_hook.py", backups)
+        if r and r != "unchanged":
+            created_add(dst)
+        merges[".claude/settings.json"] = r
     if "codex" in clients:
-        for src, dst in (("hooks.template.json", "hooks.json"),
-                         ("config.template.toml", "config.toml")):
-            if _copy_template(os.path.join(ad, "codex", src),
-                              os.path.join(target, ".codex", dst), backups):
-                created_add(os.path.join(target, ".codex", dst))
+        dsth = os.path.join(target, ".codex", "hooks.json")
+        r = merge_json_hooks(dsth, os.path.join(ad, "codex", "hooks.template.json"),
+                             "codex_hook.py", backups)
+        if r and r != "unchanged":
+            created_add(dsth)
+        merges[".codex/hooks.json"] = r
+        dstc = os.path.join(target, ".codex", "config.toml")
+        r = merge_codex_config(dstc, args.mode, args.integration_mode, backups)
+        if r and r != "unchanged":
+            created_add(dstc)
+        merges[".codex/config.toml"] = r
+
+    # ── Level 2 (devkit) adoption extras: CI workflow + domain-pack scaffold.
+    # These are the real difference between L1 (gate/hooks only) and L2 (full
+    # adoption). Copied only if absent — never clobber the project's own files.
+    level_extras = []
+    if apply_devkit:
+        dk = devkit_root()
+        ci_src = os.path.join(dk, "templates", "gitea-workflow", "ci.yml")
+        ci_dst = os.path.join(target, ".gitea", "workflows", "casan-ci.yml")
+        if _copy_if_absent(ci_src, ci_dst, None, target, created):
+            level_extras.append(".gitea/workflows/casan-ci.yml")
+        dom_src = os.path.join(dk, "templates", "domain-pack")
+        dom_dst = os.path.join(target, "apps", project, "domain")
+        n = _copy_tree_missing(dom_src, dom_dst, target, created)
+        if n:
+            level_extras.append("apps/%s/domain (%d files)" % (project, n))
 
     # ── manifest (so uninstall/verify know what init created) ──
     manifest = {
@@ -219,14 +406,22 @@ def cmd_init(args):
         "status": "initialized",
         "project_id": project,
         "target": target,
+        "target_level": lvl,
+        "target_level_name": lvl_name,
         "harness_version": version,
         "harness_hash": hhash,
         "enforcement_mode": args.mode,
         "clients": clients,
         "created": created,
-        "note": ("harness NOT copied into repo (hybrid model); "
-                 "run `casan verify-harness` to check the pin"),
+        "hook_merges": merges,
+        "level_extras": level_extras,
+        "note": ("harness NOT copied into repo (hybrid model); client hooks MERGED "
+                 "(existing config preserved); run `casan verify-harness` to check the pin"),
     }, ensure_ascii=False, indent=2))
+    if preview:
+        sys.stderr.write("casan init: NOTE — Level 3 (platform) is a PREVIEW SERVICE (Control "
+                         "Panel/Dashboard), adopted by DEPLOYING it, not by repo config. "
+                         "Applied the Level 2 base here; deploy platform separately.\n")
     if hsource == "error":
         sys.stderr.write("casan init: WARNING — could not compute harness hash; "
                          "pin verification will be unavailable.\n")
@@ -264,6 +459,36 @@ def cmd_verify(args):
     return 0
 
 
+def cmd_level(args):
+    """Show the installed packaging level and the project's target level."""
+    harness = resolve_harness(args.harness)
+    installed = None
+    if harness:
+        try:
+            with open(os.path.join(install_root(harness), ".casan-level"), "r", encoding="utf-8") as fh:
+                installed = fh.read().strip()
+        except (OSError, IOError):
+            installed = "unknown"
+    target = os.path.abspath(args.target or os.getcwd())
+    cfg = _load_json_or(os.path.join(target, ".casan", "config.json"), {})
+    status_map = {1: "implemented", 2: "implemented", 3: "preview", 4: "future"}
+    tl = cfg.get("target_level")
+    out = {
+        "installed_level": installed,
+        "project_target_level": tl,
+        "project_target_level_name": cfg.get("target_level_name"),
+        "project_level_status": status_map.get(tl, "unknown") if tl else None,
+        "levels": {
+            "1 core": "implemented — harness + gates + CLI",
+            "2 devkit": "implemented — + adoption tooling (casan init, CI, domain-pack)",
+            "3 platform": "preview — Control Panel/Dashboard SERVICE (deploy separately)",
+            "4 enterprise": "future — not shipped",
+        },
+    }
+    print(json.dumps(out, ensure_ascii=False, indent=2))
+    return 0
+
+
 def main(argv=None):
     parser = argparse.ArgumentParser(prog="casan-init", description="CASAN hybrid adoption")
     sub = parser.add_subparsers(dest="cmd")
@@ -272,20 +497,31 @@ def main(argv=None):
     pi.add_argument("--target", help="project root (default: cwd)")
     pi.add_argument("--project", help="project id (^[a-z][a-z0-9-]{1,62}$; default: dir name)")
     pi.add_argument("--client", choices=["claude", "codex", "all"], default="all")
+    pi.add_argument("--level", default="devkit",
+                    help="packaging level to adopt: 1|core, 2|devkit (default), 3|platform (preview), 4|enterprise (refused)")
     pi.add_argument("--mode", choices=["observe", "enforce"], default="observe")
     pi.add_argument("--integration-mode", dest="integration_mode",
                     choices=["project_hook", "managed_hook", "casan_owned"], default="project_hook")
+    pi.add_argument("--force", action="store_true",
+                    help="bypass the source-hub safety guard (adopt CASAN into a CASAN checkout)")
     pi.add_argument("--harness", help="override harness root")
 
     pv = sub.add_parser("verify", help="verify the resolved harness matches the project pin")
     pv.add_argument("--target", help="project root (default: cwd)")
     pv.add_argument("--harness", help="override harness root")
 
+    pl = sub.add_parser("level", help="show installed + project packaging level")
+    pl.add_argument("--show", action="store_true", help="(default) show levels")
+    pl.add_argument("--target", help="project root (default: cwd)")
+    pl.add_argument("--harness", help="override harness root")
+
     args = parser.parse_args(argv)
     if args.cmd == "init":
         return cmd_init(args)
     if args.cmd == "verify":
         return cmd_verify(args)
+    if args.cmd == "level":
+        return cmd_level(args)
     parser.print_help()
     return 64
 

packages/casan-devkit/tests/hybrid-install-tests.sh

@@ -64,6 +64,71 @@ PROJ2="$WORK/proj2/Some_App"; mkdir -p "$PROJ2"
 PID=$(python3 -c 'import json;print(json.load(open("'"$PROJ2"'/.casan/config.json"))["project_id"])' 2>/dev/null)
 [[ "$PID" =~ ^[a-z][a-z0-9-]{1,62}$ ]] && pass "defaulted project id is sanitized ($PID)" || fail "bad default project id ($PID)"
 
+echo "===== ⑦ init MERGES into an existing shell (agents/skills/hooks preserved) ====="
+EXP="$WORK/existing"; mkdir -p "$EXP/.claude/agents" "$EXP/.claude/skills" "$EXP/.codex"
+cat > "$EXP/.claude/settings.json" <<'EOF'
+{ "model": "claude-opus-4-8", "hooks": { "PreToolUse": [ {"matcher":"*","hooks":[{"type":"command","command":"my-existing-hook.sh"}]} ] } }
+EOF
+echo "agent" > "$EXP/.claude/agents/reviewer.md"; echo "skill" > "$EXP/.claude/skills/deploy.md"
+printf '[hooks]\nenabled = true\n\n[mytool]\nfoo = 1\n' > "$EXP/.codex/config.toml"
+( cd "$EXP" && "$CASAN" init --project existing-app >/dev/null 2>&1 )
+py_check() { python3 - "$1" "$2" <<'PY'
+import json,sys
+d=json.load(open(sys.argv[1]))
+cmds=[h["command"] for ev in d.get("hooks",{}).values() for g in ev for h in g["hooks"]]
+sys.exit(0 if any(sys.argv[2] in c for c in cmds) else 1)
+PY
+}
+[ -f "$EXP/.claude/agents/reviewer.md" ] && [ -f "$EXP/.claude/skills/deploy.md" ] && pass "existing agents/skills preserved" || fail "agents/skills lost"
+py_check "$EXP/.claude/settings.json" "my-existing-hook" && pass "existing Claude hook preserved (not clobbered)" || fail "existing hook clobbered"
+py_check "$EXP/.claude/settings.json" "claude_hook.py" && pass "CASAN Claude hook merged in" || fail "CASAN hook not merged"
+[ "$(python3 -c 'import json;print(json.load(open("'"$EXP"'/.claude/settings.json")).get("model"))')" = "claude-opus-4-8" ] && pass "unrelated settings key (model) preserved" || fail "model key lost"
+grep -q '\[mytool\]' "$EXP/.codex/config.toml" && pass "existing codex [mytool] preserved" || fail "mytool lost"
+[ "$(grep -c '^\[hooks\]' "$EXP/.codex/config.toml")" = "1" ] && pass "codex config.toml has no duplicate [hooks] table" || fail "duplicate [hooks]"
+# idempotent
+( cd "$EXP" && "$CASAN" init --project existing-app >/dev/null 2>&1 )
+N=$(python3 -c 'import json;d=json.load(open("'"$EXP"'/.claude/settings.json"));print(sum(1 for g in d["hooks"]["PreToolUse"] for h in g["hooks"] if "claude_hook.py" in h["command"]))')
+[ "$N" = "1" ] && pass "re-running init is idempotent (no duplicate CASAN hook)" || fail "init duplicated CASAN hook (n=$N)"
+
+echo "===== ⑧ level-aware install + init (packaging/levels.json) ====="
+# core install: no devkit, casan init unavailable
+CORE_HOME="$WORK/home-core/.casan"
+CASAN_HOME="$CORE_HOME" sh "$REPO_ROOT/install.sh" --level core >/dev/null 2>&1
+[ -d "$CORE_HOME/current/packages/casan-devkit" ] && fail "core install pulled in devkit" || pass "core level excludes devkit"
+[ "$(cat "$CORE_HOME/current/.casan-level" 2>/dev/null)" = "core" ] && pass "install records level=core" || fail "no .casan-level=core"
+# Always run init inside a THROWAWAY dir — never the ambient cwd.
+CINIT="$WORK/core-init-proj"; mkdir -p "$CINIT"
+CI_OUT=$( ( cd "$CINIT" && "$CORE_HOME/bin/casan" init 2>&1 | head -1 ) || true )
+echo "$CI_OUT" | grep -q "requires the casan-devkit" && pass "casan init unavailable on core (clear message)" || fail "core init did not fail clearly ($CI_OUT)"
+
+# enterprise refused, platform refused-with-guidance
+ERC=0; CASAN_HOME="$WORK/home-e/.casan" sh "$REPO_ROOT/install.sh" --level enterprise >/dev/null 2>&1 || ERC=$?
+[ "$ERC" -eq 3 ] && pass "install --level enterprise refused (rc=3, no fake-complete)" || fail "enterprise not refused (rc=$ERC)"
+PRC=0; CASAN_HOME="$WORK/home-p/.casan" sh "$REPO_ROOT/install.sh" --level platform >/dev/null 2>&1 || PRC=$?
+[ "$PRC" -ne 0 ] && pass "install --level platform refused (preview service, rc=$PRC)" || fail "platform install pretended to succeed"
+
+# devkit install: init --level differentiation
+DK_HOME="$WORK/home-dk/.casan"
+CASAN_HOME="$DK_HOME" sh "$REPO_ROOT/install.sh" --level devkit >/dev/null 2>&1
+DKC="$DK_HOME/bin/casan"
+L1="$WORK/l1"; mkdir -p "$L1"; ( cd "$L1" && "$DKC" init --level 1 --project l1 >/dev/null 2>&1 )
+( [ ! -d "$L1/.gitea" ] && [ ! -d "$L1/apps" ] ) && pass "init --level 1 = gate/hooks only (no CI/domain)" || fail "L1 wrote devkit extras"
+[ -f "$L1/.claude/settings.json" ] && pass "init --level 1 still writes Plan-20 hooks (core feature)" || fail "L1 missing hooks"
+L2="$WORK/l2"; mkdir -p "$L2"; ( cd "$L2" && "$DKC" init --level 2 --project l2 >/dev/null 2>&1 )
+( [ -f "$L2/.gitea/workflows/casan-ci.yml" ] && [ -d "$L2/apps/l2/domain" ] ) && pass "init --level 2 adds CI + domain-pack" || fail "L2 missing devkit extras"
+L4RC=0; L4="$WORK/l4"; mkdir -p "$L4"; ( cd "$L4" && "$DKC" init --level 4 --project l4 >/dev/null 2>&1 ) || L4RC=$?
+[ "$L4RC" -eq 3 ] && pass "init --level 4 (enterprise) refused (rc=3)" || fail "L4 init not refused (rc=$L4RC)"
+LVL=$( ( cd "$L2" && "$DKC" level show ) | python3 -c 'import json,sys;print(json.load(sys.stdin)["project_target_level"])' 2>/dev/null)
+[ "$LVL" = "2" ] && pass "casan level show reports project target level" || fail "level show wrong ($LVL)"
+
+echo "===== ⑨ SAFETY: init refuses to adopt a CASAN source hub into itself ====="
+HUB="$WORK/fakehub"; mkdir -p "$HUB/packages/casan-harness/scripts/bash"
+echo '#casan' > "$HUB/packages/casan-harness/scripts/bash/casan-harness.sh"
+GRC=0; ( cd "$HUB" && "$DKC" init --project hub >/dev/null 2>"$WORK/hub.err" ) || GRC=$?
+[ "$GRC" -eq 65 ] && pass "init refuses a source hub (rc=65)" || fail "source-hub not refused (rc=$GRC)"
+[ ! -f "$HUB/.claude/settings.json" ] && pass "no hooks written into the refused hub" || fail "hooks written into source hub"
+( cd "$HUB" && "$DKC" init --project hub --force >/dev/null 2>&1 ) && pass "--force overrides the source-hub guard" || fail "--force did not override guard"
+
 echo ""
 echo "===== HYBRID INSTALL SUMMARY: PASS=$PASS FAIL=$FAIL ====="
 [[ "$FAIL" -eq 0 ]] || exit 1

packaging/levels.json

@@ -19,9 +19,14 @@
         "packages/casan-harness/memory",
         "packages/casan-harness/templates",
         "packages/casan-harness/tests",
+        "packages/casan-harness/adapters",
+        "packages/casan-harness/schemas",
         "packages/casan-harness/init-options.json",
         "packages/casan-harness/README.md",
         "bin/casan",
+        "install.sh",
+        "install.ps1",
+        "packaging/levels.json",
         "VERSION"
       ],
       "excludes_globs": ["**/__pycache__/**", "**/*.pyc", "**/.DS_Store"],