docs: update CLAUDE.md, README, and Vietnamese guide for migration step

- CLAUDE.md: document migrator.py algorithm and junction-removal rationale
- README.md: pipeline now 5 steps, add --skip-migrate flag, add migrator.py
  to folder structure, update test count 142 -> 158
- docs/huong-dan-su-dung.md: 5-step pipeline table, new glossary entry,
  updated footer version note

CLAUDE.md

@@ -101,14 +101,15 @@ Pass 2 builds `ok_disk_names` — the set of disk names that already match the s
 - `logs.py` — real-time log viewer fed from the stdout/stderr queue
 - `settings.py` — in-app editor for `config.json` (server URL, paths, credentials)
 
-**`_find_folder` (mods.py) — three-level name matching:** The mods view resolves a mod's local folder by mod name from `comparison.json`, which may differ from the server-canonical folder name used by the fetcher. Lookup order:
+**`_find_folder` (mods.py) — four-level name matching:** The mods view resolves a mod's local folder by mod name from `comparison.json`, which may differ from the server-canonical folder name used by the fetcher. Lookup order:
 1. Exact: `@{mod_name}`
 2. Case-insensitive: `@CBA_A3` matches `CBA_A3`
 3. Normalized (`_normalize_name`): strips all non-alphanumeric — handles punctuation/spacing differences, e.g. `@US GEAr- Units (IFA3)` matches `US GEAr: Units (IFA3)` (both → `usgearunitsifa3`)
+4. Steam ID via `meta.cpp`: reads `publishedid` from each folder's `meta.cpp` and matches against `mod["steam_id"]` — handles the case where the folder name bears no resemblance to the modlist name but the mod content is correct
 
 **`selection.json`** — GUI selection state file, tracked in git. Persists which mods/groups are selected between GUI sessions. Written by the GUI; safe to delete (GUI recreates it on next save).
 
-**`run_tool` subprocess streaming:** Tool scripts are launched via `subprocess.Popen` (not `subprocess.run`) with `stdout=PIPE, stderr=STDOUT`, read line-by-line via `iter(proc.stdout.readline, "")`, and posted to the log queue immediately. Python's own output buffering is disabled with the `-u` flag and `PYTHONUNBUFFERED=1` in the environment — without these, output would batch inside the pipe and only appear when the script exits.
+**`run_tool` subprocess streaming:** Tool scripts are launched via `subprocess.Popen` (not `subprocess.run`) with `stdout=PIPE, stderr=STDOUT`, read line-by-line via `iter(proc.stdout.readline, "")`, and posted to the log queue immediately. Python's own output buffering is disabled with the `-u` flag and `PYTHONUNBUFFERED=1` in the environment — without these, output would batch inside the pipe and only appear when the script exits. The `Popen` call uses `encoding="utf-8", errors="replace"` and sets `PYTHONUTF8=1` in the child environment so that tqdm's Unicode block characters (e.g. `▉`) don't crash the pipe reader on Windows, where the default `charmap` codec cannot decode them.
 
 **GUI threading model:** Every network or long-running operation runs in a `threading.Thread(daemon=True)` so the Tkinter event loop is never blocked. The only safe way to update widgets from a background thread is `self.after(0, callback)` — never touch widgets directly from a worker thread. `_poll_log` drains the entire log queue in one `after(80, ...)` tick and does a single batched `CTkTextbox.insert()` call rather than one per log entry, keeping the UI smooth even when `tqdm` emits many rapid updates during downloads. The wizard's "Test Connection" button follows the same pattern: `requests.get` runs in a daemon thread; the result is posted back via `self.after(0, ...)` with widget references captured *before* the thread starts, so stale references cannot update the wrong widgets if the user navigates away mid-request.
 
@@ -116,6 +117,24 @@ Pass 2 builds `ok_disk_names` — the set of disk names that already match the s
 
 **`build_server_index` progress callback:** Accepts an optional `progress_fn(current, total, name)` callback. `step_fetch` in `run.py` uses this to print `Indexing N/M: @FolderName` every 25 folders so the log never goes silent during the server scan phase. The library itself never calls `print` — the caller owns the I/O.
 
+### `migrator.py` — mod group migration
+
+Before `step_fetch` runs, `step_migrate` moves locally-downloaded mod folders to match the group assignments in the new `comparison.json`. This avoids re-downloading mods that already exist on disk under a different group when presets are switched (e.g. `A` → `A_v1`).
+
+**Algorithm:**
+
+1. `_build_local_index(downloads)` — scans every `downloads/{group}/@Folder`, reads `meta.cpp` to extract `publishedid`, builds `{steam_id → (group, path)}` and `{norm_name → (group, path)}` maps.
+2. `_build_target_list(comparison)` — flattens `comparison.json` into `[(new_group, steam_id, mod_name)]`.
+3. For each target: locate mod on disk (steam_id first, normalised name fallback); skip if already in correct group or destination exists; remove stale junction from `arma_dir` if present; move folder with `shutil.move`.
+
+**Junction removal is critical:** a stale junction (target moved away) still has the reparse point attribute, so `_is_junction()` returns `True` and `link_group` would skip it as `already_linked` without recreating it at the new path. Removing the junction before the move lets `step_link` recreate it correctly.
+
+**CLI:** `python run.py --skip-migrate` bypasses the step if needed.
+
+### `update_mods.py` — orphan file removal
+
+After downloading updated files, `update_mods.py` compares every file in the local mod folder against the server's file list and **deletes any local files that no longer exist on the server**. This prevents stale `.pbo` or `.bisign` files from accumulating when a mod's content changes upstream. Each removed file is logged as `[-] orphan removed: <rel_path>` and the final summary line includes an orphan count. The orphan check runs even when no files need downloading (e.g. timestamps match but the local folder has extras).
+
 ### GUI localization (`gui/locales.py`)
 
 All user-facing strings are centralised in `gui/locales.py`. Two languages are supported: English (`"en"`) and Vietnamese (`"vi"`).

README.md

@@ -12,7 +12,7 @@ cp config.template.json config.json   # fill in server URL + credentials + arma_
 python check_deps.py                  # verify dependencies
 
 # Day-to-day: full pipeline
-python run.py                         # parse → compare → download → link
+python run.py                         # parse → compare → migrate → download → link
 
 # GUI (recommended)
 python gui.py
@@ -24,7 +24,7 @@ python sync_missing.py                # retry mods that were absent from server
 python check_names.py --fix           # fix folder name mismatches
 
 # Testing
-python test_suite.py                  # 142 tests (network tests auto-skip if offline)
+python test_suite.py                  # 158 tests (network tests auto-skip if offline)
 ```
 
 ---
@@ -133,29 +133,34 @@ Place your Arma 3 Launcher preset exports (`.html`) into the `modlist_html/` fol
 python run.py
 ```
 
-This runs all four steps in sequence:
+This runs all five steps in sequence:
 
 ```
-Step 1/4: Parse presets       — modlist_html/*.html  ->  modlist_json/*.json
-Step 2/4: Compare presets     — produces modlist_json/comparison.json
-Step 3/4: Fetch mods          — downloads from server  ->  downloads/
-Step 4/4: Link mods           — creates junctions/symlinks in Arma 3 Server dir
+Step 1/5: Parse presets       — modlist_html/*.html  ->  modlist_json/*.json
+Step 2/5: Compare presets     — produces modlist_json/comparison.json
+Step 3/5: Migrate mod groups  — moves existing folders to match new group assignments
+Step 4/5: Fetch mods          — downloads from server  ->  downloads/
+Step 5/5: Link mods           — creates junctions/symlinks in Arma 3 Server dir
 ```
 
+The **migrate step** avoids re-downloading mods that already exist on disk when you switch preset versions (e.g. `A` → `A_v1`). It matches mods by steam ID (via `meta.cpp`) and moves the folder to the correct group, removing any stale junction first so the link step can re-create it at the new path.
+
 ### Skip flags
 
 ```bash
-python run.py --skip-fetch --skip-link          # parse + compare only
+python run.py --skip-fetch --skip-link                    # parse + compare + migrate only
 python run.py --skip-parse --skip-compare --skip-fetch    # link only
 python run.py --skip-parse --skip-compare --skip-fetch --group shared
+python run.py --skip-migrate                              # skip auto-migration
 ```
 
 | Flag | Skips |
 |------|-------|
 | `--skip-parse` | Step 1 (HTML parsing) |
 | `--skip-compare` | Step 2 (preset comparison) |
-| `--skip-fetch` | Step 3 (downloading) |
-| `--skip-link` | Step 4 (linking) |
+| `--skip-migrate` | Step 3 (mod group migration) |
+| `--skip-fetch` | Step 4 (downloading) |
+| `--skip-link` | Step 5 (linking) |
 | `--group GROUP` | Link step: only link this one group (e.g. `shared`) |
 
 > **Safe to re-run.** Every step is idempotent — existing files are skipped, already-linked mods are skipped.
@@ -526,7 +531,7 @@ The same functionality is available as the **Clean Orphans** tab in the GUI.
 
 ### run.py
 
-Orchestrator that chains all four pipeline steps. Described in [Quick Start](#quick-start--full-pipeline) above.
+Orchestrator that chains all five pipeline steps. Described in [Quick Start](#quick-start--full-pipeline) above.
 
 ---
 
@@ -602,6 +607,7 @@ arma-modlist-tools/
 |   |- linker.py              # Junction/symlink manager
 |   |- reporter.py            # Missing-mod report builder
 |   |- cleaner.py             # Orphan folder detection
+|   |- migrator.py            # Mod group migration (move folders to match comparison.json)
 |   |- config.py              # config.json loader
 |   |- compat.py              # OS detection + encoding fix
 |
@@ -652,7 +658,7 @@ arma-modlist-tools/
 |- check_names.py             # Diagnose and fix folder name / steam_id issues
 |- clean_orphans.py           # Find and delete orphaned mod folders
 |- check_deps.py              # Dependency checker
-|- test_suite.py              # Test suite (142 tests)
+|- test_suite.py              # Test suite (158 tests)
 ```
 
 ---
@@ -691,7 +697,7 @@ arma-modlist-tools/
 
 ## Running Tests
 
-The test suite covers all modules with 142 tests. Network tests (section 15) auto-skip when the server is unreachable.
+The test suite covers all modules with 158 tests. Network tests auto-skip when the server is unreachable.
 
 ```bash
 python test_suite.py
@@ -713,7 +719,9 @@ python test_suite.py
   cleaner              8 tests
   e2e — clean_orphans  6 tests   (subprocess CLI)
   coverage gaps       23 tests   (mocked platform branches)
+  gui.views.mods       8 tests   (_find_folder matching)
+  migrator             7 tests   (group migration logic)
   live server          9 tests   (skipped if server unreachable)
 ------------------------------------------------------------
-  Results: 142 passed, 0 failed, 0 skipped  (142 total)
+  Results: 158 passed, 0 failed, 0 skipped  (158 total)
 ```

arma_modlist_tools/__init__.py

@@ -12,6 +12,7 @@ from .config  import load_config, Config
 from .compat  import is_windows, is_linux, get_os_label, fix_console_encoding
 from .reporter import build_missing_report, save_missing_report
 from .cleaner  import find_orphan_folders, folder_size
+from .migrator import migrate_mod_groups
 
 __all__ = [
     # parser
@@ -32,4 +33,6 @@ __all__ = [
     "build_missing_report", "save_missing_report",
     # cleaner
     "find_orphan_folders", "folder_size",
+    # migrator
+    "migrate_mod_groups",
 ]

arma_modlist_tools/migrator.py

@@ -0,0 +1,186 @@
+"""
+arma_modlist_tools.migrator
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Move locally-downloaded mod folders to match the group assignments in
+comparison.json, avoiding redundant re-downloads when presets are renamed
+or reorganised.
+
+A mod "needs migration" when it exists on disk under
+``downloads/{old_group}/@FolderName`` but comparison.json now assigns it
+to ``downloads/{new_group}/@FolderName``.
+
+Algorithm
+---------
+1. Build a *local index*: scan every ``downloads/{group}/@ModDir`` and read
+   its ``meta.cpp`` to find its steam_id.  Also record its normalised folder
+   name.  Result: ``{steam_id: (group, path)}`` and
+   ``{norm_name: (group, path)}``.
+
+2. Build a *target list* from comparison.json: for every mod in every group,
+   record which group comparison now assigns it to.
+
+3. For each target entry:
+   - Find the mod in the local index (steam_id first, normalised name fallback).
+   - If not found on disk: skip (step_fetch will download it).
+   - If already in the correct group: skip.
+   - If the destination already exists: skip (step_fetch handles file-level sync).
+   - Otherwise: remove any stale junction first, then move old → new.
+"""
+from __future__ import annotations
+
+import shutil
+from pathlib import Path
+
+from .fetcher import _normalize_name, _parse_meta_cpp
+from .linker  import _is_junction, remove_junction
+
+
+def _build_local_index(downloads: Path) -> dict:
+    """Scan ``downloads/`` and return a two-key index of existing mod folders.
+
+    :returns: ``{"by_steam_id": {sid: (group, path)},
+                 "by_norm_name": {norm: (group, path)}}``
+
+    First match wins for both keys (sorted directory order is deterministic).
+    """
+    by_steam_id:  dict[str, tuple[str, Path]] = {}
+    by_norm_name: dict[str, tuple[str, Path]] = {}
+
+    if not downloads.is_dir():
+        return {"by_steam_id": by_steam_id, "by_norm_name": by_norm_name}
+
+    for group_dir in sorted(downloads.iterdir()):
+        if not group_dir.is_dir():
+            continue
+        group_name = group_dir.name
+        for mod_dir in sorted(group_dir.iterdir()):
+            if not mod_dir.is_dir() or not mod_dir.name.startswith("@"):
+                continue
+
+            norm = _normalize_name(mod_dir.name)
+            if norm not in by_norm_name:
+                by_norm_name[norm] = (group_name, mod_dir)
+
+            meta = mod_dir / "meta.cpp"
+            if meta.exists():
+                try:
+                    sid = _parse_meta_cpp(
+                        meta.read_text(encoding="utf-8", errors="replace")
+                    )
+                    if sid and sid not in by_steam_id:
+                        by_steam_id[sid] = (group_name, mod_dir)
+                except OSError:
+                    pass
+
+    return {"by_steam_id": by_steam_id, "by_norm_name": by_norm_name}
+
+
+def _build_target_list(comparison: dict) -> list[tuple[str, str | None, str]]:
+    """Flatten comparison.json into ``[(new_group, steam_id_or_None, mod_name)]``.
+
+    Shared mods → group ``"shared"``; unique mods → group = preset name.
+    """
+    entries: list[tuple[str, str | None, str]] = []
+    for mod in comparison.get("shared", {}).get("mods", []):
+        entries.append(("shared", mod.get("steam_id") or None, mod.get("name", "")))
+    for preset, pdata in comparison.get("unique", {}).items():
+        for mod in pdata.get("mods", []):
+            entries.append((preset, mod.get("steam_id") or None, mod.get("name", "")))
+    return entries
+
+
+def migrate_mod_groups(
+    downloads: Path,
+    arma_dir: Path | None,
+    comparison: dict,
+) -> dict:
+    """Move locally-downloaded mod folders to match *comparison* group assignments.
+
+    :param downloads:   Path to the ``downloads/`` directory.
+    :param arma_dir:    Path to the Arma 3 server directory used for junction
+                        cleanup.  Pass ``None`` to skip junction removal.
+    :param comparison:  Parsed ``comparison.json`` dict.
+    :returns: Result dict::
+
+                {
+                  "moved":               int,
+                  "junction_removed":    int,
+                  "skipped_correct":     int,
+                  "skipped_dest_exists": int,
+                  "skipped_not_found":   int,
+                  "errors":              {mod_name: error_message},
+                }
+    """
+    result: dict = {
+        "moved": 0,
+        "junction_removed": 0,
+        "skipped_correct": 0,
+        "skipped_dest_exists": 0,
+        "skipped_not_found": 0,
+        "errors": {},
+    }
+
+    local = _build_local_index(downloads)
+
+    for new_group, steam_id, mod_name in _build_target_list(comparison):
+        # 1. Locate on disk — steam_id first, normalised name fallback
+        entry: tuple[str, Path] | None = None
+        if steam_id:
+            entry = local["by_steam_id"].get(steam_id)
+        if entry is None:
+            entry = local["by_norm_name"].get(_normalize_name(mod_name))
+
+        if entry is None:
+            result["skipped_not_found"] += 1
+            continue
+
+        old_group, old_path = entry
+
+        # 2. Already in the correct group?
+        if old_group == new_group:
+            result["skipped_correct"] += 1
+            continue
+
+        # 3. Destination already present — let step_fetch handle file-level sync
+        new_path = downloads / new_group / old_path.name
+        if new_path.exists():
+            result["skipped_dest_exists"] += 1
+            continue
+
+        # 4. Remove stale junction so step_link can re-create it at the new path
+        if arma_dir is not None and arma_dir.is_dir():
+            link = arma_dir / old_path.name
+            if _is_junction(link):
+                ok, err = remove_junction(link)
+                if ok:
+                    result["junction_removed"] += 1
+                else:
+                    print(f"  MIGRATE WARNING: cannot remove junction "
+                          f"{link.name}: {err}")
+
+        # 5. Move folder (shutil.move handles cross-device gracefully)
+        try:
+            new_path.parent.mkdir(parents=True, exist_ok=True)
+            shutil.move(str(old_path), str(new_path))
+            print(f"  MIGRATE moved: {old_path.name}  {old_group} -> {new_group}")
+            result["moved"] += 1
+
+            # Update index so later targets don't re-match the now-moved path
+            if steam_id:
+                local["by_steam_id"][steam_id] = (new_group, new_path)
+            local["by_norm_name"][_normalize_name(old_path.name)] = (
+                new_group, new_path
+            )
+
+        except OSError as exc:
+            print(f"  MIGRATE ERROR: {old_path.name}: {exc}")
+            result["errors"][mod_name] = str(exc)
+
+    print(
+        f"  Moved: {result['moved']}  "
+        f"Junctions removed: {result['junction_removed']}  "
+        f"Already correct: {result['skipped_correct']}  "
+        f"Dest exists: {result['skipped_dest_exists']}  "
+        f"Not on disk: {result['skipped_not_found']}"
+    )
+    return result

docs/huong-dan-su-dung.md

@@ -37,7 +37,8 @@ Tài liệu này dành cho người dùng **chưa biết gì** về dự án. B
 Ứng dụng sẽ tự động:
 - Đọc danh sách mod từ các preset
 - So sánh, tìm mod dùng chung và mod riêng giữa các preset
-- Tải mod từ máy chủ về máy tính của bạn
+- **Di chuyển** các thư mục mod đã tải về sang đúng nhóm mới (tránh tải lại khi đổi phiên bản preset)
+- Tải mod từ máy chủ về máy tính của bạn (chỉ những mod thực sự chưa có)
 - Tạo liên kết (junction/symlink) để Arma 3 Server nhận ra các mod
 
 ---
@@ -153,13 +154,14 @@ Giao diện gồm thanh điều hướng bên trái và khu vực nội dung bê
 
 ### 5.3 Trạng thái Pipeline
 
-Cột bên phải hiển thị 4 bước của quy trình:
+Cột bên phải hiển thị 5 bước của quy trình:
 
 | Bước | Mô tả | Dấu hiệu hoàn thành |
 |------|-------|-------------------|
 | Phân tích preset | Đọc danh sách mod từ tệp HTML | Có ≥ 2 preset được chọn |
 | So sánh preset | Tìm mod chung và riêng | Tệp `comparison.json` tồn tại |
-| Tải mod | Tải tệp mod từ máy chủ | Có thư mục mod trong `downloads/` |
+| Di chuyển nhóm mod | Chuyển thư mục mod sẵn có sang đúng nhóm mới | Tự động (không cần tải lại) |
+| Tải mod | Tải tệp mod thực sự còn thiếu từ máy chủ | Có thư mục mod trong `downloads/` |
 | Liên kết với Arma | Tạo junction tới thư mục Arma 3 | Thư mục Arma 3 Server tồn tại |
 
 Biểu tượng `✓` (xanh) = đã xong, `○` (xám) = chưa xong.
@@ -391,7 +393,7 @@ Hiển thị các đường dẫn đang dùng: URL máy chủ, thư mục Arma,
 | Thuật ngữ | Giải thích |
 |-----------|------------|
 | **Preset** | Tệp HTML xuất từ Arma 3 Launcher chứa danh sách mod |
-| **Pipeline** | Chuỗi 4 bước tự động: phân tích → so sánh → tải → liên kết |
+| **Pipeline** | Chuỗi 5 bước tự động: phân tích → so sánh → di chuyển nhóm → tải → liên kết |
 | **Junction / Symlink** | Liên kết thư mục ảo — Arma 3 thấy mod trong thư mục của mình nhưng tệp thực sự nằm ở `downloads/` |
 | **Shared mods** | Mod xuất hiện trong tất cả preset đã chọn |
 | **Unique mods** | Mod chỉ có trong một preset cụ thể |
@@ -401,9 +403,10 @@ Hiển thị các đường dẫn đang dùng: URL máy chủ, thư mục Arma,
 | **comparison.json** | Tệp kết quả so sánh preset, lưu danh sách mod theo nhóm |
 | **missing_report.json** | Báo cáo mod có trong preset nhưng chưa có trên máy chủ |
 | **downloads/** | Thư mục chứa tệp mod đã tải về |
+| **Di chuyển nhóm mod** | Bước tự động chuyển thư mục mod từ nhóm cũ sang nhóm mới theo `comparison.json` — tránh tải lại khi đổi phiên bản preset |
 | **Mod thừa (Orphan)** | Thư mục mod còn trong `downloads/` nhưng không còn trong preset nào đang dùng |
 | **config.json** | Tệp cấu hình lưu thông tin máy chủ và đường dẫn |
 
 ---
 
-*Phiên bản tài liệu: 2026-04 (cập nhật: thêm Clean Orphans). Nếu có vấn đề, liên hệ người quản trị máy chủ.*
+*Phiên bản tài liệu: 2026-04 (cập nhật: thêm bước Di chuyển nhóm mod, pipeline 5 bước). Nếu có vấn đề, liên hệ người quản trị máy chủ.*

gui/app.py

@@ -151,7 +151,7 @@ class ArmaModManagerApp(ctk.CTk):
             # run.py calls fix_console_encoding() at import time, which needs
             # the real sys.stdout.buffer. Import it before we redirect stdout.
             try:
-                from run import step_fetch, step_link
+                from run import step_migrate, step_fetch, step_link
             except Exception as _import_err:
                 self.after(0, lambda: self.post_log(
                     f"\n✗  Failed to load pipeline: {_import_err}\n"
@@ -165,7 +165,7 @@ class ArmaModManagerApp(ctk.CTk):
                 from arma_modlist_tools.compare import compare_presets
 
                 # Step 1 — Parse selected presets
-                _hdr("Step 1 / 4", t("pipeline.step1_name"))
+                _hdr("Step 1 / 5", t("pipeline.step1_name"))
                 cfg.modlist_json.mkdir(exist_ok=True)
                 presets = []
                 for fp in sorted(cfg.modlist_html.glob("*.html")):
@@ -182,7 +182,7 @@ class ArmaModManagerApp(ctk.CTk):
                     presets.append(preset)
 
                 # Step 2 — Compare
-                _hdr("Step 2 / 4", t("pipeline.step2_name"))
+                _hdr("Step 2 / 5", t("pipeline.step2_name"))
                 result = compare_presets(*presets)
                 cfg.comparison.write_text(
                     json.dumps(result, indent=2, ensure_ascii=False),
@@ -193,12 +193,16 @@ class ArmaModManagerApp(ctk.CTk):
                 print(f"  Shared: {result['shared']['mod_count']}  |  "
                       f"Unique: {total_unique}")
 
-                # Step 3 — Fetch
-                _hdr("Step 3 / 4", t("pipeline.step3_name"))
+                # Step 3 — Migrate
+                _hdr("Step 3 / 5", t("pipeline.step3_name"))
+                step_migrate(cfg)
+
+                # Step 4 — Fetch
+                _hdr("Step 4 / 5", t("pipeline.step4_name"))
                 step_fetch(cfg)
 
-                # Step 4 — Link
-                _hdr("Step 4 / 4", t("pipeline.step4_name"))
+                # Step 5 — Link
+                _hdr("Step 5 / 5", t("pipeline.step5_name"))
                 groups = (
                     sorted(p.name for p in cfg.downloads.iterdir() if p.is_dir())
                     if cfg.downloads.is_dir() else []

gui/locales.py

@@ -29,8 +29,9 @@ _EN: dict[str, str] = {
     "pipeline.starting":             "Pipeline started",
     "pipeline.step1_name":           "Parse presets",
     "pipeline.step2_name":           "Compare presets",
-    "pipeline.step3_name":           "Download mods",
-    "pipeline.step4_name":           "Link mods",
+    "pipeline.step3_name":           "Migrate mod groups",
+    "pipeline.step4_name":           "Download mods",
+    "pipeline.step5_name":           "Link mods",
 
     # ── app.py dialogs ────────────────────────────────────────────────────────
     "app.dlg_presets_title":         "Not enough presets selected",
@@ -270,8 +271,9 @@ _VI: dict[str, str] = {
     "pipeline.starting":             "Pipeline đã bắt đầu",
     "pipeline.step1_name":           "Phân tích preset",
     "pipeline.step2_name":           "So sánh preset",
-    "pipeline.step3_name":           "Tải mod",
-    "pipeline.step4_name":           "Liên kết mod",
+    "pipeline.step3_name":           "Di chuyển nhóm mod",
+    "pipeline.step4_name":           "Tải mod",
+    "pipeline.step5_name":           "Liên kết mod",
 
     # ── app.py dialogs ────────────────────────────────────────────────────────
     "app.dlg_presets_title":         "Chưa chọn đủ preset",

gui/views/mods.py

@@ -7,7 +7,7 @@ from typing import TYPE_CHECKING, Optional
 
 import customtkinter as ctk
 
-from arma_modlist_tools.fetcher import _normalize_name
+from arma_modlist_tools.fetcher import _normalize_name, _parse_meta_cpp
 from gui._constants import COLOR_OK, COLOR_ERROR, COLOR_WARN, COLOR_RUNNING
 from gui.locales import t
 from gui.views.base import BaseView
@@ -16,13 +16,14 @@ if TYPE_CHECKING:
     from gui.app import ArmaModManagerApp
 
 
-def _find_folder(group_dir: Path, mod_name: str) -> Optional[Path]:
+def _find_folder(group_dir: Path, mod_name: str, steam_id: str | None = None) -> Optional[Path]:
     """Return the local mod folder path, or None if not downloaded.
 
     Matches in priority order:
     1. Exact folder name ``@{mod_name}``
     2. Case-insensitive name (handles ``@CBA_A3`` vs ``CBA_A3``)
     3. Normalized name — strips non-alphanumeric (handles ``@cba_a3`` vs ``CBA A3``)
+    4. Steam ID match via ``meta.cpp`` ``publishedid`` field (folder name differs from modlist name)
     """
     if not group_dir.is_dir():
         return None
@@ -38,6 +39,18 @@ def _find_folder(group_dir: Path, mod_name: str) -> Optional[Path]:
             return p
         if _normalize_name(p.name) == target_norm:
             return p
+    # Fallback: match by steam_id via meta.cpp when folder name diverges from modlist name
+    if steam_id:
+        for p in group_dir.iterdir():
+            if not p.is_dir():
+                continue
+            meta = p / "meta.cpp"
+            try:
+                sid = _parse_meta_cpp(meta.read_text(encoding="utf-8", errors="replace"))
+                if sid == steam_id:
+                    return p
+            except OSError:
+                pass
     return None
 
 
@@ -171,19 +184,22 @@ class ModsView(BaseView):
                                    fg_color=("gray82", "gray22"), corner_radius=6)
             col_hdr.grid(row=0, column=0, sticky="ew", padx=4, pady=(6, 2))
             col_hdr.columnconfigure(0, weight=1)
-            for col, (w, lbl_key) in enumerate([
-                (0,   "mods.col_name"),
-                (80,  "mods.col_downloaded"),
-                (80,  "mods.col_linked"),
-                (160, "mods.col_server"),
-                (80,  ""),
+            for col, (w, lbl_key, anc) in enumerate([
+                (0,   "mods.col_name",       "w"),
+                (80,  "mods.col_downloaded",  "center"),
+                (80,  "mods.col_linked",      "center"),
+                (160, "mods.col_server",      "w"),
+                (80,  "",                     "center"),
             ]):
                 ctk.CTkLabel(col_hdr, text=t(lbl_key) if lbl_key else "",
                              font=ctk.CTkFont(weight="bold"),
-                             anchor="w", width=w or 1).grid(
+                             anchor=anc, width=w or 1).grid(
                     row=0, column=col,
-                    padx=(10 if col == 0 else 4, 4), pady=5,
+                    padx=(8 if col == 0 else 4, 4), pady=5,
                     sticky="ew" if col == 0 else "")
+            # Spacer compensates for CTkScrollableFrame's internal scrollbar width
+            # so the header columns line up with the data rows below.
+            ctk.CTkLabel(col_hdr, text="", width=16).grid(row=0, column=5, padx=0)
 
             # Scrollable rows
             scroll = ctk.CTkScrollableFrame(tab_frame)
@@ -215,7 +231,7 @@ class ModsView(BaseView):
         link_map: dict[str, bool],
     ) -> None:
         for i, mod in enumerate(sorted(mods, key=lambda m: m["name"].lower())):
-            folder_path = _find_folder(cfg.downloads / group, mod["name"])
+            folder_path = _find_folder(cfg.downloads / group, mod["name"], mod.get("steam_id"))
             downloaded  = folder_path is not None
             linked      = (link_map.get(folder_path.name.lower(), False)
                            if folder_path else False)
@@ -226,23 +242,23 @@ class ModsView(BaseView):
             row.columnconfigure(0, weight=1)
 
             # Mod name
-            name_lbl = ctk.CTkLabel(row, text=f"  {mod['name']}", anchor="w")
-            name_lbl.grid(row=0, column=0, sticky="ew", padx=4, pady=3)
+            name_lbl = ctk.CTkLabel(row, text=mod["name"], anchor="w")
+            name_lbl.grid(row=0, column=0, sticky="ew", padx=(8, 4), pady=3)
 
             # Downloaded
             ctk.CTkLabel(
                 row,
-                text="  ✓" if downloaded else "  ✗",
+                text="✓" if downloaded else "✗",
                 text_color=COLOR_OK if downloaded else COLOR_ERROR,
-                width=80, anchor="w",
+                width=80, anchor="center",
             ).grid(row=0, column=1, padx=4)
 
             # Linked
             ctk.CTkLabel(
                 row,
-                text="  ✓" if linked else ("  —" if not downloaded else "  ✗"),
+                text="✓" if linked else ("—" if not downloaded else "✗"),
                 text_color=COLOR_OK if linked else "gray",
-                width=80, anchor="w",
+                width=80, anchor="center",
             ).grid(row=0, column=2, padx=4)
 
             # Server status
@@ -254,7 +270,7 @@ class ModsView(BaseView):
             # Update button (hidden until stale detected)
             folder_name = folder_path.name if folder_path else None
             update_btn = ctk.CTkButton(
-                row, text=t("mods.update_btn"), width=70,
+                row, text=t("mods.update_btn"), width=80,
                 command=(lambda g=group, fn=folder_name:
                          self._update_mod(g, fn)) if folder_name else None,
                 state="normal" if folder_name else "disabled",

run.py

@@ -78,6 +78,22 @@ def step_compare(cfg) -> None:
     print(f"  -> {cfg.comparison}")
 
 
+def step_migrate(cfg) -> None:
+    if not cfg.comparison.exists():
+        print(f"  NOTE: {cfg.comparison} not found — skipping migration.")
+        return
+    if not cfg.downloads.is_dir():
+        print(f"  NOTE: downloads dir missing ({cfg.downloads}) — nothing to migrate.")
+        return
+    from arma_modlist_tools.migrator import migrate_mod_groups
+    comparison = json.loads(cfg.comparison.read_text(encoding="utf-8"))
+    arma_dir   = cfg.arma_dir if cfg.arma_dir.is_dir() else None
+    result     = migrate_mod_groups(cfg.downloads, arma_dir, comparison)
+    if result["errors"]:
+        for name, err in result["errors"].items():
+            print(f"  ERROR  {name}: {err}")
+
+
 def step_fetch(cfg) -> None:
     if not cfg.comparison.exists():
         print(f"  ERROR: {cfg.comparison} not found. Run parse + compare first.")
@@ -178,6 +194,7 @@ def main() -> None:
     parser = argparse.ArgumentParser(description="Run the full mod management pipeline.")
     parser.add_argument("--skip-parse",   action="store_true")
     parser.add_argument("--skip-compare", action="store_true")
+    parser.add_argument("--skip-migrate", action="store_true")
     parser.add_argument("--skip-fetch",   action="store_true")
     parser.add_argument("--skip-link",    action="store_true")
     parser.add_argument("--group", "-g",  metavar="GROUP",
@@ -187,13 +204,15 @@ def main() -> None:
     steps = [
         (not args.skip_parse,   "Parse presets"),
         (not args.skip_compare, "Compare presets"),
+        (not args.skip_migrate, "Migrate mods"),
         (not args.skip_fetch,   "Fetch mods"),
         (not args.skip_link,    "Link mods"),
     ]
     active_count = sum(1 for run, _ in steps if run)
     step_num = 0
 
-    if args.skip_parse and args.skip_compare and args.skip_fetch and args.skip_link:
+    if (args.skip_parse and args.skip_compare and args.skip_migrate
+            and args.skip_fetch and args.skip_link):
         print("All steps skipped — nothing to do.")
         sys.exit(0)
 
@@ -201,6 +220,7 @@ def main() -> None:
         (cfg,),
         (cfg,),
         (cfg,),
+        (cfg,),
         None,  # handled separately
     ]):
         if not run:
@@ -221,6 +241,8 @@ def main() -> None:
             step_parse(cfg)
         elif name == "Compare presets":
             step_compare(cfg)
+        elif name == "Migrate mods":
+            step_migrate(cfg)
         elif name == "Fetch mods":
             step_fetch(cfg)
 

test_suite.py

@@ -2229,6 +2229,240 @@ test("live: list_mod_files entries are (rel_path, url, size) tuples",  _test_liv
 test("live: find_mod_folder name fallback works (no steam_id)",        _test_live_find_mod_by_name_fallback)
 
 
+# ---------------------------------------------------------------------------
+# gui.views.mods — _find_folder
+# ---------------------------------------------------------------------------
+
+group("gui.views.mods — _find_folder")
+
+import importlib.util as _mods_ilu
+
+_mods_spec = _mods_ilu.spec_from_file_location(
+    "gui.views.mods", Path(__file__).parent / "gui" / "views" / "mods.py"
+)
+_mods_mod = _mods_ilu.module_from_spec(_mods_spec)
+# Stub out customtkinter and gui imports so the module loads without a display
+import types as _types
+import sys as _sys
+
+for _stub in ("customtkinter", "gui", "gui._constants", "gui.locales",
+              "gui.views", "gui.views.base"):
+    if _stub not in _sys.modules:
+        _sys.modules[_stub] = _types.ModuleType(_stub)
+
+# Provide the colour constants the module references at import time
+_sys.modules["gui._constants"].COLOR_OK      = "#4CAF50"
+_sys.modules["gui._constants"].COLOR_ERROR   = "#F44336"
+_sys.modules["gui._constants"].COLOR_WARN    = "#FF9800"
+_sys.modules["gui._constants"].COLOR_RUNNING = "#2196F3"
+
+# Stub BaseView so the class body does not fail
+_base_stub = _sys.modules["gui.views.base"] = _types.ModuleType("gui.views.base")
+_base_stub.BaseView = object
+
+# Stub locales.t so string calls don't crash
+_sys.modules["gui.locales"].t = lambda key, **kw: key
+
+_mods_spec.loader.exec_module(_mods_mod)
+_find_folder_fn = _mods_mod._find_folder
+
+
+def _test_ff_returns_none_for_missing_group(tmp_path):
+    assert _find_folder_fn(tmp_path / "nonexistent", "MyMod") is None
+
+
+def _test_ff_exact_match(tmp_path):
+    (tmp_path / "@MyMod").mkdir()
+    result = _find_folder_fn(tmp_path, "MyMod")
+    assert result == tmp_path / "@MyMod"
+
+
+def _test_ff_case_insensitive_match(tmp_path):
+    (tmp_path / "@mymod").mkdir()
+    result = _find_folder_fn(tmp_path, "MyMod")
+    assert result == tmp_path / "@mymod"
+
+
+def _test_ff_normalized_match(tmp_path):
+    # Folder on disk uses underscores; modlist name uses spaces — both normalize to same string
+    (tmp_path / "@My_Mod_Edition").mkdir()
+    result = _find_folder_fn(tmp_path, "My Mod Edition")
+    assert result == tmp_path / "@My_Mod_Edition"
+
+
+def _test_ff_steam_id_fallback(tmp_path):
+    """Folder name bears no resemblance to mod name but meta.cpp has correct ID."""
+    folder = tmp_path / "@ServerCanonicalName"
+    folder.mkdir()
+    (folder / "meta.cpp").write_text('publishedid = 123456789;\nname = "Some Mod";\n')
+    result = _find_folder_fn(tmp_path, "Completely Different Name", steam_id="123456789")
+    assert result == folder
+
+
+def _test_ff_steam_id_no_false_positive(tmp_path):
+    """Wrong steam_id in meta.cpp must not match."""
+    folder = tmp_path / "@WrongMod"
+    folder.mkdir()
+    (folder / "meta.cpp").write_text('publishedid = 999999999;\n')
+    result = _find_folder_fn(tmp_path, "My Mod", steam_id="123456789")
+    assert result is None
+
+
+def _test_ff_steam_id_skipped_when_none(tmp_path):
+    """No steam_id supplied → meta.cpp is never read (no false positives)."""
+    folder = tmp_path / "@SomeFolder"
+    folder.mkdir()
+    (folder / "meta.cpp").write_text('publishedid = 123456789;\n')
+    result = _find_folder_fn(tmp_path, "My Mod", steam_id=None)
+    assert result is None
+
+
+def _test_ff_missing_meta_cpp_skipped(tmp_path):
+    """Folders without meta.cpp are silently skipped in the steam_id pass."""
+    folder = tmp_path / "@NoMeta"
+    folder.mkdir()
+    result = _find_folder_fn(tmp_path, "My Mod", steam_id="123456789")
+    assert result is None
+
+
+# Wrap tmp_path calls in lambdas that supply a temp dir
+def _with_tmp(fn):
+    def wrapper():
+        with tempfile.TemporaryDirectory() as d:
+            fn(Path(d))
+    return wrapper
+
+
+test("_find_folder: None when group dir missing",
+     _with_tmp(_test_ff_returns_none_for_missing_group))
+test("_find_folder: exact @ModName match",
+     _with_tmp(_test_ff_exact_match))
+test("_find_folder: case-insensitive name match",
+     _with_tmp(_test_ff_case_insensitive_match))
+test("_find_folder: normalized name match (punctuation differs)",
+     _with_tmp(_test_ff_normalized_match))
+test("_find_folder: steam_id fallback via meta.cpp",
+     _with_tmp(_test_ff_steam_id_fallback))
+test("_find_folder: wrong steam_id in meta.cpp is not a match",
+     _with_tmp(_test_ff_steam_id_no_false_positive))
+test("_find_folder: no steam_id supplied → meta.cpp not checked",
+     _with_tmp(_test_ff_steam_id_skipped_when_none))
+test("_find_folder: missing meta.cpp silently skipped",
+     _with_tmp(_test_ff_missing_meta_cpp_skipped))
+
+
+# ---------------------------------------------------------------------------
+# migrator — migrate_mod_groups
+# ---------------------------------------------------------------------------
+
+group("migrator — migrate_mod_groups")
+
+from arma_modlist_tools.migrator import migrate_mod_groups as _migrate
+
+
+def _make_mod(dl: Path, grp: str, folder: str, steam_id: str | None = None) -> Path:
+    """Create a minimal mod folder under downloads/group/folder."""
+    d = dl / grp / folder
+    d.mkdir(parents=True)
+    if steam_id:
+        (d / "meta.cpp").write_text(f"publishedid = {steam_id};\n", encoding="utf-8")
+    (d / "dummy.pbo").write_bytes(b"\x00" * 8)
+    return d
+
+
+def _test_migrate_already_correct():
+    comp = {"shared": {"mods": [{"name": "CBA_A3", "steam_id": "450814997"}]}, "unique": {}}
+    with tempfile.TemporaryDirectory() as d:
+        dl = Path(d) / "downloads"
+        _make_mod(dl, "shared", "@CBA_A3", "450814997")
+        result = _migrate(dl, None, comp)
+        assert_eq(result["moved"], 0)
+        assert_eq(result["skipped_correct"], 1)
+
+
+def _test_migrate_moves_by_steam_id():
+    comp = {"shared": {"mods": []}, "unique": {
+        "A_v1": {"mods": [{"name": "ACE3", "steam_id": "463939057"}]}
+    }}
+    with tempfile.TemporaryDirectory() as d:
+        dl = Path(d) / "downloads"
+        old = _make_mod(dl, "A", "@ACE3", "463939057")
+        result = _migrate(dl, None, comp)
+        assert_eq(result["moved"], 1)
+        assert not old.exists(), "old folder must be gone"
+        assert (dl / "A_v1" / "@ACE3").exists(), "new folder must exist"
+        assert (dl / "A_v1" / "@ACE3" / "dummy.pbo").exists(), "files preserved"
+
+
+def _test_migrate_moves_by_normalized_name():
+    """No meta.cpp — matching falls back to normalised folder name."""
+    comp = {"shared": {"mods": [{"name": "CBA_A3", "steam_id": None}]}, "unique": {
+        "A": {"mods": []}
+    }}
+    with tempfile.TemporaryDirectory() as d:
+        dl = Path(d) / "downloads"
+        _make_mod(dl, "A", "@CBA_A3", steam_id=None)
+        result = _migrate(dl, None, comp)
+        assert_eq(result["moved"], 1)
+        assert (dl / "shared" / "@CBA_A3").exists()
+
+
+def _test_migrate_skips_dest_exists():
+    comp = {"shared": {"mods": [{"name": "CBA_A3", "steam_id": "450814997"}]}, "unique": {}}
+    with tempfile.TemporaryDirectory() as d:
+        dl = Path(d) / "downloads"
+        _make_mod(dl, "A",      "@CBA_A3", "450814997")
+        _make_mod(dl, "shared", "@CBA_A3", "450814997")
+        result = _migrate(dl, None, comp)
+        assert_eq(result["moved"], 0)
+        assert_eq(result["skipped_dest_exists"], 1)
+
+
+def _test_migrate_skips_not_on_disk():
+    comp = {"shared": {"mods": [{"name": "CBA_A3", "steam_id": "450814997"}]}, "unique": {}}
+    with tempfile.TemporaryDirectory() as d:
+        dl = Path(d) / "downloads"
+        dl.mkdir()
+        result = _migrate(dl, None, comp)
+        assert_eq(result["skipped_not_found"], 1)
+        assert_eq(result["moved"], 0)
+
+
+def _test_migrate_removes_stale_junction():
+    from arma_modlist_tools.linker import create_junction, _is_junction
+    comp = {"shared": {"mods": [{"name": "ACE3", "steam_id": "463939057"}]}, "unique": {}}
+    with tempfile.TemporaryDirectory() as dl_d, \
+         tempfile.TemporaryDirectory() as arma_d:
+        dl   = Path(dl_d) / "downloads"
+        arma = Path(arma_d)
+        old  = _make_mod(dl, "A", "@ACE3", "463939057")
+        link = arma / "@ACE3"
+        create_junction(link, old)
+        assert _is_junction(link), "precondition: junction must exist"
+        result = _migrate(dl, arma, comp)
+        assert_eq(result["moved"], 1)
+        assert_eq(result["junction_removed"], 1)
+        assert not _is_junction(link), "stale junction must be removed"
+        assert (dl / "shared" / "@ACE3").exists()
+
+
+def _test_migrate_missing_downloads_dir():
+    comp = {"shared": {"mods": [{"name": "X", "steam_id": "1"}]}, "unique": {}}
+    with tempfile.TemporaryDirectory() as d:
+        result = _migrate(Path(d) / "nonexistent", None, comp)
+        assert_eq(result["moved"], 0)
+        assert_eq(result["skipped_not_found"], 1)
+
+
+test("migrator: already in correct group → no move",       _test_migrate_already_correct)
+test("migrator: moves mod by steam_id to new group",        _test_migrate_moves_by_steam_id)
+test("migrator: moves mod by normalized name (no meta.cpp)", _test_migrate_moves_by_normalized_name)
+test("migrator: skips when destination already exists",     _test_migrate_skips_dest_exists)
+test("migrator: skips mod not on disk",                     _test_migrate_skips_not_on_disk)
+test("migrator: removes stale junction before moving",      _test_migrate_removes_stale_junction)
+test("migrator: no-op when downloads dir missing",          _test_migrate_missing_downloads_dir)
+
+
 # ---------------------------------------------------------------------------
 # Summary
 # ---------------------------------------------------------------------------

update_mods.py

@@ -102,6 +102,7 @@ def main() -> None:
     COL_GROUP = 24
 
     total_checked = total_updated = total_bytes = 0
+    total_removed = 0
     not_on_server = []
 
     for group, folder_name, mod_dir in targets:
@@ -123,13 +124,21 @@ def main() -> None:
         all_files = list_mod_files(folder_url, session) if not args.force else stale
         checked = len(all_files) if not args.force else len(stale)
 
-        if not stale:
+        # Find local files that no longer exist on the server (orphans)
+        server_rel = {rel for rel, _, _ in all_files}
+        orphans = [
+            f for f in mod_dir.rglob("*") if f.is_file()
+            and str(f.relative_to(mod_dir)).replace("\\", "/") not in server_rel
+        ]
+
+        if not stale and not orphans:
             print(f"  [=] {folder_name:<{COL_MOD}}  {group:<{COL_GROUP}}  {checked} files  up-to-date")
             total_checked += checked
             continue
 
         # Download stale files
         mod_bytes = 0
+        if stale:
             with tqdm(
                 total=len(stale), unit="file",
                 desc=f"  {folder_name[-COL_MOD:]:<{COL_MOD}}",
@@ -148,21 +157,32 @@ def main() -> None:
                     mod_bytes += n
                     file_bar.update(1)
 
+        # Remove orphan files
+        for orphan in orphans:
+            tqdm.write(f"  [-] orphan removed: {orphan.relative_to(mod_dir)}")
+            orphan.unlink()
+
         total_checked += checked
         total_updated += len(stale)
         total_bytes   += mod_bytes
-        print(f"  [+] {folder_name:<{COL_MOD}}  {group:<{COL_GROUP}}  "
-              f"{checked} files  {len(stale)} updated  ({_fmt_bytes(mod_bytes)})")
+        total_removed += len(orphans)
+        parts = [f"{checked} files"]
+        if stale:
+            parts.append(f"{len(stale)} updated ({_fmt_bytes(mod_bytes)})")
+        if orphans:
+            parts.append(f"{len(orphans)} orphan(s) removed")
+        print(f"  [+] {folder_name:<{COL_MOD}}  {group:<{COL_GROUP}}  {'  '.join(parts)}")
 
     print(f"\n{'='*56}")
     print(f"  Total: {total_checked} files checked, "
           f"{total_updated} updated, "
+          f"{total_removed} orphan(s) removed, "
           f"{_fmt_bytes(total_bytes)} downloaded")
     if not_on_server:
         print(f"  Not found on server ({len(not_on_server)}): {', '.join(not_on_server)}")
     print(f"{'='*56}\n")
 
-    if total_updated == 0 and not not_on_server:
+    if total_updated == 0 and total_removed == 0 and not not_on_server:
         print("  All mods are up-to-date.\n")