fix: use absolute paths in Arma 3 launch args to survive cwd change

Arma 3 changes its own working directory to the exe folder on startup,
so relative paths like -config=server.cfg resolved against A3Master/
instead of the server data dir. Configs were never found, and profile/
battleye dirs pointed at the wrong location (confirmed via RPT location
in A3Master/server/ instead of the data dir).

build_launch_args() now accepts an optional server_dir: Path argument.
When provided, all four path args (-config, -cfg, -profiles, -bepath)
use absolute paths. Service passes server_dir at the call site.

API.md

@@ -1374,18 +1374,30 @@ List all available mods and which are currently enabled for this server.
     "mods": [
       {
         "name": "@CBA_A3",
-        "folder_path": "C:/Arma3Server/@CBA_A3",
-        "enabled": true
+        "path": "D:/Arma3Server/1/mods/@CBA_A3",
+        "size_bytes": 12345678,
+        "enabled": true,
+        "is_server_mod": false,
+        "display_name": "Community Base Addons A3",
+        "workshop_id": "450814997"
       },
       {
         "name": "@ACRE2",
-        "folder_path": "C:/Arma3Server/@ACRE2",
-        "enabled": true
+        "path": "D:/Arma3Server/1/mods/@ACRE2",
+        "size_bytes": 9876543,
+        "enabled": true,
+        "is_server_mod": true,
+        "display_name": "ACRE2",
+        "workshop_id": "751965892"
       },
       {
         "name": "@USAF",
-        "folder_path": "C:/Arma3Server/@USAF",
-        "enabled": false
+        "path": "D:/Arma3Server/1/mods/@USAF",
+        "size_bytes": 55000000,
+        "enabled": false,
+        "is_server_mod": false,
+        "display_name": null,
+        "workshop_id": null
       }
     ]
   },
@@ -1393,6 +1405,8 @@ List all available mods and which are currently enabled for this server.
 }
 ```
 
+Mod folders are scanned from `{server_data_dir}/{server_id}/mods/@*`. `display_name` is parsed from `mod.cpp`; `workshop_id` from `meta.cpp`. `is_server_mod: true` means the mod is passed via `-serverMod=` instead of `-mod=`.
+
 ---
 
 ### PUT /servers/{server_id}/mods/enabled
@@ -1405,13 +1419,18 @@ Set the list of enabled mods. This **replaces** the entire enabled list — send
 
 ```json
 {
-  "mods": ["@CBA_A3", "@ACRE2"]
+  "mods": [
+    { "name": "@CBA_A3", "is_server_mod": false },
+    { "name": "@ACRE2",  "is_server_mod": true  }
+  ]
 }
 ```
 
-| Field  | Type          | Required | Description                        |
-|--------|---------------|----------|------------------------------------|
-| `mods` | array[string] | Yes      | Complete list of mod names to enable |
+| Field               | Type    | Required | Description |
+|---------------------|---------|----------|-------------|
+| `mods`              | array   | Yes      | Complete list of mod entries to enable |
+| `mods[].name`       | string  | Yes      | Mod folder name (must start with `@`) |
+| `mods[].is_server_mod` | bool | No       | `true` → `-serverMod=`, `false` (default) → `-mod=` |
 
 **Response 200:**
 
@@ -1420,7 +1439,10 @@ Set the list of enabled mods. This **replaces** the entire enabled list — send
   "success": true,
   "data": {
     "message": "Enabled mods updated. Restart the server for changes to take effect.",
-    "enabled_mods": ["@CBA_A3", "@ACRE2"]
+    "enabled_mods": [
+      { "name": "@CBA_A3", "is_server_mod": false },
+      { "name": "@ACRE2",  "is_server_mod": true  }
+    ]
   },
   "error": null
 }

CLAUDE.md

@@ -3,16 +3,17 @@
 ## Quick Start
 
 ```bash
-# Backend (from backend/)
-python -m uvicorn main:app --host 0.0.0.0 --port 8000 --reload
+# Backend (from backend/, venv must be active)
+uvicorn main:app --host 0.0.0.0 --port 8000 --reload
 
 # Frontend (from frontend/)
-npx vite --host
+npm run dev
 ```
 
 - Backend API: http://localhost:8000 (docs: http://localhost:8000/docs)
-- Frontend: http://localhost:5173
-- Default admin: `admin` / (random, printed at first startup; reset via `python -c "from core.auth.utils import hash_password; print(hash_password('admin123'))"` then update SQLite)
+- Frontend: http://localhost:5173 (Vite proxies /api and /ws to :8000)
+- Default admin: `admin` / (random, printed at first startup)
+- Full setup instructions (secrets, venv, debug configs): see README.md
 
 ## Architecture
 
@@ -94,29 +95,13 @@ cd frontend && npx tsc --noEmit
 - **Arma 3 per-mission params**: `ServerConfig.missions` is now `list[MissionRotationItem]` (adds optional `params: dict`). A new `default_mission_params` field holds server-wide defaults. Config version bumped to `"1.1.0"`. `_render_server_cfg()` now emits a `class Missions { ... }` block when the rotation is non-empty; `class Params` inside each mission uses per-mission params → global defaults → omit (in that priority order). The `MissionRotationEntry.params` is edited per-row in the Missions tab via `MissionParamsEditor`; `default_mission_params` is edited in the Config tab via the `key-value` widget.
 - **Config version migration**: `migrate_config("1.0.0", ...)` backfills `params: {}` on each existing rotation entry and adds `default_mission_params: {}`. `normalize_section()` does the same on reads for stored rows that pre-date the migration run.
 
-## Known Bugs — Mods Tab (fix next session)
+## Mods Tab — Implementation Notes
 
-Three bugs prevent the Mods tab from working correctly:
-
-### Bug 1 — Save fails with TypeError (critical)
-`Arma3ModManager.set_enabled_mods()` calls `config_repo.upsert_section()` with wrong keyword argument names:
-- Passes `data=` → should be `config_data=`
-- Passes `expected_version=` → should be `expected_config_version=`
-- Missing required `game_type=` argument
-- Missing required `schema_version=` argument
-
-**File:** `backend/adapters/arma3/mod_manager.py`, `set_enabled_mods()` method (~line 127)
-
-### Bug 2 — Mods not applied on server start (critical)
-`service.py` `start_server()` reads mods from a `server_mods` JOIN `mods` table (SQLAlchemy query, ~line 246) — but those tables are never populated by the Mods tab UI. The correct source is `config_repo.get_section(server_id, "mods")["enabled_mods"]`. The start flow needs to read from `config_repo` instead of the dead `server_mods` table join.
-
-**File:** `backend/core/servers/service.py`, `start_server()` method (~line 242–255)
-
-### Bug 3 — Wrong mod folder location (UX)
-`list_available_mods()` scans the server root (`get_server_dir()`) for `@*` folders. Mods should live in a `mods/` subfolder: `{server_dir}/mods/@ModName`. Needs:
-1. Change scan path: `server_dir / "mods"` instead of `server_dir`
-2. Ensure the `mods/` subdirectory is created by `ensure_server_dirs` (add `"mods"` to the Arma3 `get_server_dir_layout()`)
-3. Update CLAUDE.md + user docs to say mods go in `D:/ImContainer/Arma3Server/{id}/mods/@ModName`
-
-**File:** `backend/adapters/arma3/mod_manager.py`, `list_available_mods()` and `_server_dir()` (~line 47–88)
-Also: `backend/adapters/arma3/adapter.py`, `get_server_dir_layout()` (add `"mods"` entry)
+- Mods go in `{server_data_dir}/{server_id}/mods/@ModName` (e.g. `D:/ImContainer/Arma3Server/1/mods/@CBA_A3/`)
+- Enabled mods config schema: `{"enabled_mods": [{"name": "@CBA_A3", "is_server_mod": false}]}`
+  - Old string-list format is auto-migrated to the dict format on read
+  - `is_server_mod: true` → `-serverMod=` arg; `false` → `-mod=` arg
+- `list_available_mods()` scans `{server_dir}/mods/` for `@*` directories
+- `set_enabled_mods()` stores the new dict format; validates names against disk
+- Server start reads mods from `game_configs` via `config_repo`, NOT from the dead `server_mods` table
+- Directory scaffold: all 4 Arma3 subdirs (`server/`, `battleye/`, `mpmissions/`, `mods/`) are created on server create and backfilled on startup; each gets a `README.txt` if not already present

FRONTEND.md

@@ -189,7 +189,7 @@ All server data flows through TanStack Query hooks:
 | `useUploadMission(id)` | Mutation | `POST /api/servers/:id/missions` (multipart, `File[]`) | Invalidates `["missions", id]` |
 | `useUpdateMissionRotation(id)` | Mutation | `PUT /api/servers/:id/missions/rotation` | Invalidates rotation + server config |
 | `useDeleteMission(id)` | Mutation | `DELETE /api/servers/:id/missions/:filename` | Invalidates `["missions", id]` |
-| `useSetEnabledMods(id)` | Mutation | `PUT /api/servers/:id/mods/enabled` | Invalidates `["mods", id]` |
+| `useSetEnabledMods(id)` | Mutation | `PUT /api/servers/:id/mods/enabled` body: `EnabledModEntry[]` | Invalidates `["mods", id]` |
 | `useSendCommand(id)` | Mutation | `POST /api/servers/:id/rcon/command` | No invalidation |
 | `useKickPlayer(id)` | Mutation | `POST /api/servers/:id/players/:slot_id/kick` | Invalidates `["players", id]` |
 | `useBanPlayer(id)` | Mutation | `POST /api/servers/:id/players/:slot_id/ban` | Invalidates players + bans |
@@ -219,7 +219,8 @@ All server data flows through TanStack Query hooks:
 **Key type notes**:
 - `Server` type in `useServers.ts` uses `game_port`, `current_players`, `max_players` (matches enriched API response)
 - `Mission` type: `{ name, filename, size_bytes, terrain }` — terrain parsed from filename
-- `Mod` type: `{ name, path, size_bytes, enabled, display_name, workshop_id }` — `display_name`/`workshop_id` from mod.cpp/meta.cpp
+- `Mod` type: `{ name, path, size_bytes, enabled, is_server_mod, display_name, workshop_id }` — `display_name`/`workshop_id` from mod.cpp/meta.cpp; `is_server_mod` controls `-serverMod=` vs `-mod=`
+- `EnabledModEntry` type: `{ name: string, is_server_mod: boolean }` — used as `useSetEnabledMods` mutation input
 - `Ban` type: `{ id, server_id, guid, name, reason, banned_by, banned_at, expires_at, is_active, game_data }` (matches API)
 - There is no REST endpoint for logs — logs are only pushed via WebSocket events
 

README.md

@@ -19,25 +19,78 @@ A multi-game server management platform with a Python/FastAPI backend and React/
 - **TanStack Query v5** — server state management
 - **Zustand 5** — client state (auth, UI)
 - **Tailwind CSS** — dark neumorphic design system
-- **Playwright** — E2E testing (38 tests)
-- **Vitest** + **React Testing Library** — unit tests (167 tests)
+- **Playwright** — E2E testing
+- **Vitest** + **React Testing Library** — unit tests (173 tests)
 
 ## Quick Start
 
-### Backend
+### 1 — Backend setup
 
 ```bash
 cd backend
+
+# Create and activate a virtual environment
 python -m venv venv
-source venv/bin/activate  # Windows: venv\Scripts\activate
+source venv/bin/activate        # macOS / Linux
+# venv\Scripts\activate         # Windows (cmd)
+# venv\Scripts\Activate.ps1     # Windows (PowerShell)
+
 pip install -r requirements.txt
-cp .env.example .env       # Edit with your settings
-uvicorn main:app --reload
 ```
 
-First run prints a generated admin password. Change it immediately via `PUT /api/auth/password`.
+**Generate required secrets** (one-time):
 
-### Frontend
+```bash
+# Secret key (JWT signing)
+openssl rand -hex 32
+
+# Fernet encryption key (sensitive config fields at rest)
+python -c "from cryptography.fernet import Fernet; print(Fernet.generate_key().decode())"
+```
+
+Copy `.env.example` to `.env` and fill in the two keys:
+
+```bash
+cp .env.example .env   # then open .env in your editor
+```
+
+```ini
+# .env — minimum required values
+LANGUARD_SECRET_KEY=<output of openssl command>
+LANGUARD_ENCRYPTION_KEY=<output of Fernet command>
+LANGUARD_ARMA3_DEFAULT_EXE=C:/path/to/arma3server_x64.exe
+```
+
+**Start the backend** (development — auto-reload on file changes):
+
+```bash
+uvicorn main:app --host 0.0.0.0 --port 8000 --reload
+```
+
+First run prints a randomly-generated admin password to the console. Log in and change it immediately via Settings → Change Password (or `PUT /api/auth/password`).
+
+- API root: `http://localhost:8000`
+- Interactive docs: `http://localhost:8000/docs`
+
+**Debug in VS Code:** add this `launch.json` configuration:
+
+```json
+{
+  "name": "Backend — uvicorn",
+  "type": "debugpy",
+  "request": "launch",
+  "module": "uvicorn",
+  "args": ["main:app", "--host", "0.0.0.0", "--port", "8000"],
+  "cwd": "${workspaceFolder}/backend",
+  "env": { "PYTHONDONTWRITEBYTECODE": "1" },
+  "jinja": true,
+  "justMyCode": false
+}
+```
+
+---
+
+### 2 — Frontend setup
 
 ```bash
 cd frontend
@@ -45,28 +98,64 @@ npm install
 npm run dev
 ```
 
-Opens at `http://localhost:5173`. The dev server proxies `/api` to the backend on port 8000.
+The Vite dev server starts at `http://localhost:5173` and automatically proxies:
+- `/api/*` → `http://localhost:8000` (REST)
+- `/ws/*` → `ws://localhost:8000` (WebSocket)
+
+**Debug in VS Code:** install the [JavaScript Debugger](https://marketplace.visualstudio.com/items?itemName=ms-vscode.js-debug) extension (bundled by default), then add:
+
+```json
+{
+  "name": "Frontend — Vite (Chrome)",
+  "type": "chrome",
+  "request": "launch",
+  "url": "http://localhost:5173",
+  "webRoot": "${workspaceFolder}/frontend/src",
+  "sourceMapPathOverrides": {
+    "/@fs/*": "${workspaceFolder}/frontend/*"
+  }
+}
+```
+
+Start the Vite dev server first (`npm run dev`), then launch this config to attach Chrome DevTools with source-map support.
+
+---
 
 ## Running Tests
 
-### Frontend Unit Tests
+### Backend
+
+```bash
+cd backend
+source venv/bin/activate   # (if not already active)
+
+pytest                             # all tests
+pytest tests/adapters/arma3/ -v   # adapter tests only
+pytest --tb=short -q               # quiet output
+```
+
+### Frontend unit tests
 
 ```bash
 cd frontend
-npm test                  # Watch mode
-npx vitest run            # Single run
-npx vitest run --coverage # With coverage
+npm test                          # single run (CI-friendly)
+npm run test:watch                # watch mode during development
+npx vitest run --coverage         # with coverage report
 ```
 
-### Frontend E2E Tests
+### Frontend E2E tests (Playwright)
+
+Start the backend and the Vite dev server first, then:
 
 ```bash
 cd frontend
-# Start backend + frontend dev server first
-npx playwright test                    # All tests (mocked + integration)
-npx playwright tests-e2e/integration/   # Full-stack integration tests only
+npm run test:e2e              # all E2E tests (headless)
+npm run test:e2e:ui           # Playwright UI mode (interactive, great for debugging)
+npx playwright test --headed  # watch tests run in an actual browser
 ```
 
+Integration tests (require a live backend) live in `tests-e2e/integration/`. All other tests use API mocks and run without a backend.
+
 ## Project Structure
 
 ```
@@ -101,7 +190,7 @@ languard-servers-manager/
 │   │   ├── hooks/               # useServers, useServerDetail, useAuth, useGames, useWebSocket
 │   │   ├── store/               # auth.store, ui.store (Zustand)
 │   │   ├── lib/                 # api.ts (Axios client)
-│   │   └── __tests__/          # Vitest unit tests (~120 tests)
+│   │   └── __tests__/          # Vitest unit tests (173 tests)
 │   ├── tests-e2e/               # Playwright E2E tests
 │   └── playwright.config.ts
 ├── API.md                       # REST + WebSocket API reference

backend/adapters/arma3/config_generator.py

@@ -401,20 +401,36 @@ class Arma3ConfigGenerator:
         self,
         config_sections: dict[str, dict],
         mod_args: list[str] | None = None,
+        server_dir: Path | None = None,
     ) -> list[str]:
         from adapters.exceptions import LaunchArgsError
         launch = LaunchConfig(**config_sections.get("launch", {}))
         server = ServerConfig(**config_sections.get("server", {}))
 
+        # Arma 3 changes its own cwd to the exe directory at startup, so relative
+        # paths in launch args resolve against the exe dir, not server_dir.
+        # Use absolute paths when server_dir is provided so configs are always found.
+        if server_dir is not None:
+            d = Path(server_dir)
+            config_arg   = f"-config={d / 'server.cfg'}"
+            cfg_arg      = f"-cfg={d / 'basic.cfg'}"
+            profiles_arg = f"-profiles={d / 'server'}"
+            bepath_arg   = f"-bepath={d / 'battleye'}"
+        else:
+            config_arg   = "-config=server.cfg"
+            cfg_arg      = "-cfg=basic.cfg"
+            profiles_arg = "-profiles=./server"
+            bepath_arg   = "-bepath=./battleye"
+
         args = [
             f"-port={config_sections.get('_port', 2302)}",
-            "-config=server.cfg",
-            "-cfg=basic.cfg",
-            "-profiles=./server",
+            config_arg,
+            cfg_arg,
+            profiles_arg,
             "-name=server",
             f"-world={launch.world}",
             f"-limitFPS={launch.limit_fps}",
-            "-bepath=./battleye",
+            bepath_arg,
         ]
         if launch.auto_init:
             args.append("-autoInit")
@@ -437,146 +453,148 @@ class Arma3ConfigGenerator:
         return args
 
     def get_ui_schema(self) -> dict:
+        B, A = False, True  # basic / advanced shorthand
         return {
             "server": {
-                # Identity
-                "hostname":                 {"widget": "text",     "label": "Server Name"},
-                "max_players":              {"widget": "number",   "label": "Max Players", "min": 1, "max": 1000},
-                "password":                 {"widget": "password", "label": "Join Password"},
-                "password_admin":           {"widget": "password", "label": "Admin Password"},
-                "server_command_password":  {"widget": "password", "label": "Server Command Password"},
-                # Message of the Day
-                "motd_lines":               {"widget": "textarea", "label": "Message of the Day (one line per row)"},
-                "motd_interval":            {"widget": "number",   "label": "MOTD Interval (sec)", "min": 1},
-                # Mission / Rotation
+                # Identity — basic
+                "hostname":                 {"widget": "text",     "label": "Server Name",                             "advanced": B},
+                "max_players":              {"widget": "number",   "label": "Max Players", "min": 1, "max": 1000,      "advanced": B},
+                "password":                 {"widget": "password", "label": "Join Password",                           "advanced": B},
+                "password_admin":           {"widget": "password", "label": "Admin Password",                          "advanced": B},
+                "server_command_password":  {"widget": "password", "label": "Server Command Password",                 "advanced": A},
+                # Message of the Day — basic
+                "motd_lines":               {"widget": "textarea", "label": "Message of the Day (one line per row)",   "advanced": B},
+                "motd_interval":            {"widget": "number",   "label": "MOTD Interval (sec)", "min": 1,           "advanced": B},
+                # Mission / Rotation — basic
                 "forced_difficulty":        {"widget": "select",   "label": "Forced Difficulty",
-                                             "options": ["Recruit", "Regular", "Veteran", "Custom"]},
-                "auto_select_mission":      {"widget": "toggle",   "label": "Auto-Select Mission"},
-                "random_mission_order":     {"widget": "toggle",   "label": "Random Mission Order"},
-                # Behaviour
-                "persistent":              {"widget": "toggle",   "label": "Persistent (keep running when empty)"},
-                "kick_duplicate":          {"widget": "toggle",   "label": "Kick Duplicate Connections"},
-                "skip_lobby":              {"widget": "toggle",   "label": "Skip Lobby (go straight to briefing)"},
-                "drawing_in_map":          {"widget": "toggle",   "label": "Allow Drawing in Map"},
-                # Security
-                "battleye":                {"widget": "toggle",   "label": "BattlEye Anti-Cheat"},
+                                             "options": ["Recruit", "Regular", "Veteran", "Custom"],                   "advanced": B},
+                "auto_select_mission":      {"widget": "toggle",   "label": "Auto-Select Mission",                     "advanced": B},
+                "random_mission_order":     {"widget": "toggle",   "label": "Random Mission Order",                    "advanced": B},
+                # Behaviour — mixed
+                "persistent":              {"widget": "toggle",   "label": "Persistent (keep running when empty)",     "advanced": B},
+                "kick_duplicate":          {"widget": "toggle",   "label": "Kick Duplicate Connections",               "advanced": A},
+                "skip_lobby":              {"widget": "toggle",   "label": "Skip Lobby (go straight to briefing)",     "advanced": B},
+                "drawing_in_map":          {"widget": "toggle",   "label": "Allow Drawing in Map",                     "advanced": B},
+                # Security — basic
+                "battleye":                {"widget": "toggle",   "label": "BattlEye Anti-Cheat",                      "advanced": B},
                 "verify_signatures":       {"widget": "select",   "label": "Verify Addon Signatures",
-                                            "options": ["0 - Off", "1 - Kick unsigned", "2 - Strict (kick mismatched)"]},
+                                            "options": ["0 - Off", "1 - Kick unsigned", "2 - Strict (kick mismatched)"], "advanced": B},
                 "allowed_file_patching":   {"widget": "select",   "label": "Allow File Patching",
-                                            "options": ["0 - Nobody", "1 - Lobby only", "2 - Everyone"]},
-                # Voice
-                "disable_von":             {"widget": "toggle",   "label": "Disable Voice-over-Network (VoN)"},
-                "von_codec":               {"widget": "toggle",   "label": "Use Opus VoN Codec"},
-                "von_codec_quality":       {"widget": "number",   "label": "VoN Codec Quality (0–30)", "min": 0, "max": 30},
-                # Network / Kick thresholds
-                "kick_on_ping":            {"widget": "toggle",   "label": "Kick on High Ping"},
-                "kick_on_packet_loss":     {"widget": "toggle",   "label": "Kick on High Packet Loss"},
-                "kick_on_desync":          {"widget": "toggle",   "label": "Kick on High Desync"},
-                "kick_on_timeout":         {"widget": "toggle",   "label": "Kick on Timeout"},
-                "max_ping":                {"widget": "number",   "label": "Max Ping (ms)", "min": 1},
-                "max_packet_loss":         {"widget": "number",   "label": "Max Packet Loss (%)", "min": 0, "max": 100},
-                "max_desync":              {"widget": "number",   "label": "Max Desync", "min": 0},
-                "disconnect_timeout":      {"widget": "number",   "label": "Disconnect Timeout (sec)", "min": 0},
-                # Voting
-                "vote_threshold":          {"widget": "number",   "label": "Vote Threshold (0.0–1.0)", "min": 0, "max": 1},
-                "vote_mission_players":    {"widget": "number",   "label": "Min Players to Start Vote", "min": 0},
-                "vote_timeout":            {"widget": "number",   "label": "Vote Timeout (sec)", "min": 0},
-                # Timeouts
-                "role_timeout":            {"widget": "number",   "label": "Role Selection Timeout (sec)", "min": 0},
-                "briefing_timeout":        {"widget": "number",   "label": "Briefing Timeout (sec)", "min": 0},
-                "debriefing_timeout":      {"widget": "number",   "label": "Debriefing Timeout (sec)", "min": 0},
-                "lobby_idle_timeout":      {"widget": "number",   "label": "Lobby Idle Timeout (sec)", "min": 0},
-                # Misc
-                "statistics_enabled":      {"widget": "toggle",   "label": "Enable Steam Statistics"},
-                "upnp":                    {"widget": "toggle",   "label": "Enable UPnP"},
-                "loopback":                {"widget": "toggle",   "label": "Loopback Mode (LAN only)"},
+                                            "options": ["0 - Nobody", "1 - Lobby only", "2 - Everyone"],               "advanced": B},
+                # Voice — basic
+                "disable_von":             {"widget": "toggle",   "label": "Disable Voice-over-Network (VoN)",         "advanced": B},
+                "von_codec":               {"widget": "toggle",   "label": "Use Opus VoN Codec",                       "advanced": B},
+                "von_codec_quality":       {"widget": "number",   "label": "VoN Codec Quality (0–30)", "min": 0, "max": 30, "advanced": A},
+                # Network / Kick thresholds — advanced
+                "kick_on_ping":            {"widget": "toggle",   "label": "Kick on High Ping",                        "advanced": A},
+                "kick_on_packet_loss":     {"widget": "toggle",   "label": "Kick on High Packet Loss",                 "advanced": A},
+                "kick_on_desync":          {"widget": "toggle",   "label": "Kick on High Desync",                      "advanced": A},
+                "kick_on_timeout":         {"widget": "toggle",   "label": "Kick on Timeout",                          "advanced": A},
+                "max_ping":                {"widget": "number",   "label": "Max Ping (ms)", "min": 1,                  "advanced": A},
+                "max_packet_loss":         {"widget": "number",   "label": "Max Packet Loss (%)", "min": 0, "max": 100, "advanced": A},
+                "max_desync":              {"widget": "number",   "label": "Max Desync", "min": 0,                     "advanced": A},
+                "disconnect_timeout":      {"widget": "number",   "label": "Disconnect Timeout (sec)", "min": 0,       "advanced": A},
+                # Voting — advanced
+                "vote_threshold":          {"widget": "number",   "label": "Vote Threshold (0.0–1.0)", "min": 0, "max": 1, "advanced": A},
+                "vote_mission_players":    {"widget": "number",   "label": "Min Players to Start Vote", "min": 0,     "advanced": A},
+                "vote_timeout":            {"widget": "number",   "label": "Vote Timeout (sec)", "min": 0,             "advanced": A},
+                # Timeouts — advanced
+                "role_timeout":            {"widget": "number",   "label": "Role Selection Timeout (sec)", "min": 0,  "advanced": A},
+                "briefing_timeout":        {"widget": "number",   "label": "Briefing Timeout (sec)", "min": 0,         "advanced": A},
+                "debriefing_timeout":      {"widget": "number",   "label": "Debriefing Timeout (sec)", "min": 0,       "advanced": A},
+                "lobby_idle_timeout":      {"widget": "number",   "label": "Lobby Idle Timeout (sec)", "min": 0,       "advanced": A},
+                # Misc — advanced
+                "statistics_enabled":      {"widget": "toggle",   "label": "Enable Steam Statistics",                  "advanced": A},
+                "upnp":                    {"widget": "toggle",   "label": "Enable UPnP",                              "advanced": A},
+                "loopback":                {"widget": "toggle",   "label": "Loopback Mode (LAN only)",                 "advanced": A},
                 "timestamp_format":        {"widget": "select",   "label": "Log Timestamp Format",
-                                            "options": ["none", "short", "full"]},
-                "log_file":                {"widget": "text",     "label": "Log File Name"},
-                # Admin / Headless
+                                            "options": ["none", "short", "full"],                                       "advanced": A},
+                "log_file":                {"widget": "text",     "label": "Log File Name",                            "advanced": A},
+                # Admin / Headless — advanced
                 "admin_uids":              {"widget": "tag-list", "label": "Admin Steam UIDs",
-                                            "placeholder": "76561198000000000"},
+                                            "placeholder": "76561198000000000",                                         "advanced": A},
                 "headless_clients":        {"widget": "tag-list", "label": "Headless Client IPs",
-                                            "placeholder": "127.0.0.1"},
+                                            "placeholder": "127.0.0.1",                                                "advanced": A},
                 "local_clients":           {"widget": "tag-list", "label": "Local Client IPs",
-                                            "placeholder": "127.0.0.1"},
+                                            "placeholder": "127.0.0.1",                                                "advanced": A},
                 # missions managed by the Missions tab — hidden here
                 "missions":                {"widget": "hidden"},
-                # default params applied to every mission without custom params
+                # default params — advanced
                 "default_mission_params":  {"widget": "key-value", "label": "Default Mission Parameters",
-                                            "help": "Applied to all missions without custom params. Empty = no Params block."},
+                                            "help": "Applied to all missions without custom params.",                   "advanced": A},
             },
             "basic": {
-                "min_bandwidth":            {"widget": "number", "label": "Min Bandwidth (bps)", "min": 1},
-                "max_bandwidth":            {"widget": "number", "label": "Max Bandwidth (bps)", "min": 1},
-                "max_msg_send":             {"widget": "number", "label": "Max Messages Sent per Frame", "min": 1},
-                "max_size_guaranteed":      {"widget": "number", "label": "Max Guaranteed Packet Size (bytes)", "min": 1},
-                "max_size_non_guaranteed":  {"widget": "number", "label": "Max Non-Guaranteed Packet Size (bytes)", "min": 1},
-                "min_error_to_send":        {"widget": "number", "label": "Min Error to Send"},
-                "max_custom_file_size":     {"widget": "number", "label": "Max Custom File Size (bytes)", "min": 0},
+                # All network tuning fields are advanced
+                "min_bandwidth":            {"widget": "number", "label": "Min Bandwidth (bps)", "min": 1,             "advanced": A},
+                "max_bandwidth":            {"widget": "number", "label": "Max Bandwidth (bps)", "min": 1,             "advanced": A},
+                "max_msg_send":             {"widget": "number", "label": "Max Messages Sent per Frame", "min": 1,     "advanced": A},
+                "max_size_guaranteed":      {"widget": "number", "label": "Max Guaranteed Packet Size (bytes)", "min": 1, "advanced": A},
+                "max_size_non_guaranteed":  {"widget": "number", "label": "Max Non-Guaranteed Packet Size (bytes)", "min": 1, "advanced": A},
+                "min_error_to_send":        {"widget": "number", "label": "Min Error to Send",                        "advanced": A},
+                "max_custom_file_size":     {"widget": "number", "label": "Max Custom File Size (bytes)", "min": 0,   "advanced": A},
             },
             "profile": {
-                # Damage / health
-                "reduced_damage":       {"widget": "toggle",  "label": "Reduced Damage"},
-                # Indicators (0=Never, 1=Limited distance, 2=Fade out, 3=Always)
+                # Basic difficulty options
+                "reduced_damage":       {"widget": "toggle",  "label": "Reduced Damage",                               "advanced": A},
                 "group_indicators":     {"widget": "select",  "label": "Group Indicators",
-                                         "options": ["0 - Never", "1 - Limited distance", "2 - Fade out", "3 - Always"]},
+                                         "options": ["0 - Never", "1 - Limited distance", "2 - Fade out", "3 - Always"], "advanced": B},
                 "friendly_tags":        {"widget": "select",  "label": "Friendly Name Tags",
-                                         "options": ["0 - Never", "1 - Limited distance", "2 - Fade out", "3 - Always"]},
+                                         "options": ["0 - Never", "1 - Limited distance", "2 - Fade out", "3 - Always"], "advanced": B},
                 "enemy_tags":           {"widget": "select",  "label": "Enemy Name Tags",
-                                         "options": ["0 - Never", "1 - Limited distance", "2 - Fade out", "3 - Always"]},
+                                         "options": ["0 - Never", "1 - Limited distance", "2 - Fade out", "3 - Always"], "advanced": B},
                 "detected_mines":       {"widget": "select",  "label": "Detected Mines",
-                                         "options": ["0 - Never", "1 - Limited distance", "2 - Fade out", "3 - Always"]},
+                                         "options": ["0 - Never", "1 - Limited distance", "2 - Fade out", "3 - Always"], "advanced": A},
                 "commands":             {"widget": "select",  "label": "Map Commands",
-                                         "options": ["0 - Never", "1 - High command", "2 - Fade out", "3 - Always"]},
+                                         "options": ["0 - Never", "1 - High command", "2 - Fade out", "3 - Always"],    "advanced": B},
                 "waypoints":            {"widget": "select",  "label": "Waypoints",
-                                         "options": ["0 - Never", "1 - Known positions", "2 - Fade out", "3 - Always"]},
-                "tactical_ping":        {"widget": "toggle",  "label": "Tactical Ping"},
+                                         "options": ["0 - Never", "1 - Known positions", "2 - Fade out", "3 - Always"], "advanced": B},
+                "tactical_ping":        {"widget": "toggle",  "label": "Tactical Ping",                                "advanced": A},
                 "weapon_info":          {"widget": "select",  "label": "Weapon Info",
-                                         "options": ["0 - Never", "1 - Limited distance", "2 - Fade out", "3 - Always"]},
+                                         "options": ["0 - Never", "1 - Limited distance", "2 - Fade out", "3 - Always"], "advanced": B},
                 "stance_indicator":     {"widget": "select",  "label": "Stance Indicator",
-                                         "options": ["0 - Never", "1 - Experimental", "2 - Always", "3 - Always (soldier)"]},
+                                         "options": ["0 - Never", "1 - Experimental", "2 - Always", "3 - Always (soldier)"], "advanced": B},
                 "stamina_bar":          {"widget": "select",  "label": "Stamina Bar",
-                                         "options": ["0 - Never", "1 - Low stamina only", "2 - Always"]},
-                "weapon_crosshair":     {"widget": "toggle",  "label": "Weapon Crosshair"},
-                "vision_aid":           {"widget": "toggle",  "label": "Vision Aid"},
-                "third_person_view":    {"widget": "toggle",  "label": "Third Person View"},
-                "camera_shake":         {"widget": "toggle",  "label": "Camera Shake"},
-                "score_table":          {"widget": "toggle",  "label": "Show Score Table"},
-                "death_messages":       {"widget": "toggle",  "label": "Death Messages"},
-                "von_id":               {"widget": "toggle",  "label": "Show VoN Speaker ID"},
+                                         "options": ["0 - Never", "1 - Low stamina only", "2 - Always"],               "advanced": A},
+                "weapon_crosshair":     {"widget": "toggle",  "label": "Weapon Crosshair",                             "advanced": A},
+                "vision_aid":           {"widget": "toggle",  "label": "Vision Aid",                                   "advanced": A},
+                "third_person_view":    {"widget": "toggle",  "label": "Third Person View",                            "advanced": A},
+                "camera_shake":         {"widget": "toggle",  "label": "Camera Shake",                                 "advanced": A},
+                "score_table":          {"widget": "toggle",  "label": "Show Score Table",                             "advanced": A},
+                "death_messages":       {"widget": "toggle",  "label": "Death Messages",                               "advanced": A},
+                "von_id":               {"widget": "toggle",  "label": "Show VoN Speaker ID",                          "advanced": A},
                 "map_content_friendly": {"widget": "select",  "label": "Map — Friendly Units",
-                                         "options": ["0 - Never", "1 - Limited distance", "2 - Fade out", "3 - Always"]},
+                                         "options": ["0 - Never", "1 - Limited distance", "2 - Fade out", "3 - Always"], "advanced": A},
                 "map_content_enemy":    {"widget": "select",  "label": "Map — Enemy Units",
-                                         "options": ["0 - Never", "1 - Limited distance", "2 - Fade out", "3 - Always"]},
+                                         "options": ["0 - Never", "1 - Limited distance", "2 - Fade out", "3 - Always"], "advanced": A},
                 "map_content_mines":    {"widget": "select",  "label": "Map — Mines",
-                                         "options": ["0 - Never", "1 - Limited distance", "2 - Fade out", "3 - Always"]},
-                "auto_report":          {"widget": "toggle",  "label": "Auto Report (automatic radio reports)"},
-                "multiple_saves":       {"widget": "toggle",  "label": "Multiple Saves"},
+                                         "options": ["0 - Never", "1 - Limited distance", "2 - Fade out", "3 - Always"], "advanced": A},
+                "auto_report":          {"widget": "toggle",  "label": "Auto Report (automatic radio reports)",         "advanced": A},
+                "multiple_saves":       {"widget": "toggle",  "label": "Multiple Saves",                               "advanced": A},
                 "ai_level_preset":      {"widget": "select",  "label": "AI Level Preset",
-                                         "options": ["0 - Low", "1 - Normal", "2 - High", "3 - Custom", "4 - Ultra"]},
-                "skill_ai":             {"widget": "number",  "label": "AI Skill (0.0–1.0)", "min": 0, "max": 1},
-                "precision_ai":         {"widget": "number",  "label": "AI Precision / Accuracy (0.0–1.0)", "min": 0, "max": 1},
+                                         "options": ["0 - Low", "1 - Normal", "2 - High", "3 - Custom", "4 - Ultra"],  "advanced": B},
+                "skill_ai":             {"widget": "number",  "label": "AI Skill (0.0–1.0)", "min": 0, "max": 1,       "advanced": B},
+                "precision_ai":         {"widget": "number",  "label": "AI Precision / Accuracy (0.0–1.0)", "min": 0, "max": 1, "advanced": B},
             },
             "launch": {
-                "world":                   {"widget": "text",     "label": "Default World (map name)"},
-                "limit_fps":               {"widget": "number",   "label": "FPS Limit", "min": 1, "max": 1000},
-                "cpu_count":               {"widget": "number",   "label": "CPU Core Count (0 = auto)", "min": 0},
-                "ex_threads":              {"widget": "number",   "label": "Extra Thread Count", "min": 0},
-                "max_mem":                 {"widget": "number",   "label": "Max RAM (MB, 0 = auto)", "min": 0},
-                "auto_init":               {"widget": "toggle",   "label": "Auto-Init (skip mission select)"},
-                "load_mission_to_memory":  {"widget": "toggle",   "label": "Load Mission to Memory"},
-                "enable_ht":               {"widget": "toggle",   "label": "Enable HyperThreading"},
-                "huge_pages":              {"widget": "toggle",   "label": "Enable Huge Pages (performance)"},
-                "no_logs":                 {"widget": "toggle",   "label": "Disable Server Logging"},
-                "netlog":                  {"widget": "toggle",   "label": "Enable Network Log"},
+                # All launch/startup fields are advanced
+                "world":                   {"widget": "text",     "label": "Default World (map name)",                 "advanced": A},
+                "limit_fps":               {"widget": "number",   "label": "FPS Limit", "min": 1, "max": 1000,         "advanced": A},
+                "cpu_count":               {"widget": "number",   "label": "CPU Core Count (0 = auto)", "min": 0,      "advanced": A},
+                "ex_threads":              {"widget": "number",   "label": "Extra Thread Count", "min": 0,             "advanced": A},
+                "max_mem":                 {"widget": "number",   "label": "Max RAM (MB, 0 = auto)", "min": 0,         "advanced": A},
+                "auto_init":               {"widget": "toggle",   "label": "Auto-Init (skip mission select)",          "advanced": A},
+                "load_mission_to_memory":  {"widget": "toggle",   "label": "Load Mission to Memory",                   "advanced": A},
+                "enable_ht":               {"widget": "toggle",   "label": "Enable HyperThreading",                    "advanced": A},
+                "huge_pages":              {"widget": "toggle",   "label": "Enable Huge Pages (performance)",          "advanced": A},
+                "no_logs":                 {"widget": "toggle",   "label": "Disable Server Logging",                   "advanced": A},
+                "netlog":                  {"widget": "toggle",   "label": "Enable Network Log",                       "advanced": A},
                 "extra_params":            {"widget": "tag-list", "label": "Additional Startup Parameters",
-                                            "placeholder": "-filePatching"},
+                                            "placeholder": "-filePatching",                                             "advanced": A},
             },
             "rcon": {
-                "rcon_password": {"widget": "password", "label": "RCon Password"},
-                "max_ping":      {"widget": "number",   "label": "Max Ping for RCon (ms)", "min": 1},
-                "enabled":       {"widget": "toggle",   "label": "Enable RCon"},
+                "rcon_password": {"widget": "password", "label": "RCon Password",                                      "advanced": B},
+                "max_ping":      {"widget": "number",   "label": "Max Ping for RCon (ms)", "min": 1,                   "advanced": A},
+                "enabled":       {"widget": "toggle",   "label": "Enable RCon",                                        "advanced": B},
             },
         }
 

backend/adapters/arma3/mod_manager.py

@@ -47,24 +47,27 @@ class Arma3ModManager:
     def _server_dir(self) -> Path:
         return get_server_dir(self._server_id)
 
+    def _mods_dir(self) -> Path:
+        return get_server_dir(self._server_id) / "mods"
+
     # ── File / DB operations ──
 
     def list_available_mods(self) -> list[dict]:
         """
-        Scan the server directory for mod folders (directories starting with '@').
+        Scan the server's mods/ subdirectory for mod folders (directories starting with '@').
 
         Returns list of dicts:
             name: str        — directory name (e.g. "@CBA_A3")
             path: str        — absolute directory path
             size_bytes: int  — total directory size (approximate, non-recursive)
         """
-        server_dir = self._server_dir()
-        if not server_dir.exists():
+        mods_dir = self._mods_dir()
+        if not mods_dir.exists():
             return []
 
         mods = []
         try:
-            for entry in server_dir.iterdir():
+            for entry in mods_dir.iterdir():
                 if entry.is_dir() and _MOD_DIR_PATTERN.match(entry.name):
                     try:
                         size = sum(
@@ -87,54 +90,59 @@ class Arma3ModManager:
         mods.sort(key=lambda m: m["name"].lower())
         return mods
 
-    def get_enabled_mods(self, config_repo) -> list[str]:
+    def get_enabled_mods(self, config_repo) -> list[dict]:
         """
-        Get the list of enabled mod names from the database config.
+        Get the list of enabled mods from the database config.
 
-        Args:
-            config_repo: ConfigRepository instance.
-
-        Returns list of mod directory names (e.g. ["@CBA_A3", "@ace"]).
+        Returns list of dicts: [{"name": "@CBA_A3", "is_server_mod": False}, ...]
+        Handles migration from old string-list format automatically.
         """
         mods_section = config_repo.get_section(self._server_id, "mods")
         if mods_section is None:
             return []
-        enabled = mods_section.get("enabled_mods", [])
-        if isinstance(enabled, str):
-            enabled = [m.strip() for m in enabled.split(",") if m.strip()]
-        return enabled
+        raw = mods_section.get("enabled_mods", [])
+        result = []
+        for item in raw:
+            if isinstance(item, str):
+                result.append({"name": item, "is_server_mod": False})
+            elif isinstance(item, dict):
+                result.append({"name": item.get("name", ""), "is_server_mod": bool(item.get("is_server_mod", False))})
+        return result
 
-    def set_enabled_mods(self, mod_names: list[str], config_repo) -> None:
+    def set_enabled_mods(self, mod_entries: list[dict], config_repo) -> None:
         """
         Update the enabled mods list in the database config.
 
         Args:
-            mod_names: List of mod directory names to enable.
+            mod_entries: List of dicts with "name" (str) and "is_server_mod" (bool).
             config_repo: ConfigRepository instance.
 
-        Raises AdapterError if any mod name doesn't exist on disk.
+        Raises AdapterError if any mod name is invalid or not found on disk.
         """
         available = {m["name"] for m in self.list_available_mods()}
-        for name in mod_names:
+        for entry in mod_entries:
+            name = entry.get("name", "")
             if not _MOD_DIR_PATTERN.match(name):
                 raise AdapterError(f"Invalid mod name '{name}': must start with '@'")
             if name not in available:
                 raise AdapterError(
-                    f"Mod '{name}' not found in server directory. "
+                    f"Mod '{name}' not found in mods directory. "
                     f"Available: {sorted(available)}"
                 )
 
         mods_section = config_repo.get_section(self._server_id, "mods") or {}
-        current_version = mods_section.get("config_version", 0)
+        current_version = mods_section.get("_meta", {}).get("config_version")
         config_repo.upsert_section(
             server_id=self._server_id,
+            game_type="arma3",
             section="mods",
-            data={"enabled_mods": mod_names},
-            expected_version=current_version,
+            config_data={"enabled_mods": mod_entries},
+            schema_version="1.0.0",
+            expected_config_version=current_version,
         )
         logger.info(
             "Updated enabled mods for server %d: %s",
-            self._server_id, mod_names,
+            self._server_id, [e["name"] for e in mod_entries],
         )
 
     # ── CLI argument building ──

backend/adapters/arma3/process_config.py

@@ -27,4 +27,50 @@ class Arma3ProcessConfig:
 
     def get_server_dir_layout(self) -> list[str]:
         """Subdirectories to create inside servers/{id}/."""
-        return ["server", "battleye", "mpmissions"]
+        return ["server", "battleye", "mpmissions", "mods"]
+
+    _DIR_READMES: dict[str, str] = {
+        "server": (
+            "Arma 3 Server — Log Directory\n"
+            "==============================\n\n"
+            "Arma 3 writes RPT log files here (e.g. arma3server_2024-01-01_12-00-00.rpt).\n"
+            "These are viewable in Languard's Logs tab.\n\n"
+            "Do NOT place files here manually."
+        ),
+        "battleye": (
+            "BattlEye Anti-Cheat\n"
+            "===================\n\n"
+            "BattlEye configuration and GUID ban list files live here.\n"
+            "Managed automatically by Arma 3 and Languard.\n\n"
+            "Do NOT modify these files manually unless you know what you are doing."
+        ),
+        "mpmissions": (
+            "Mission Files\n"
+            "=============\n\n"
+            "Place Arma 3 mission files (.pbo) here to make them available for the server.\n"
+            "Once placed here they will appear in Languard's Missions tab.\n\n"
+            "Example: Wasteland_A3.Altis.pbo"
+        ),
+        "mods": (
+            "Mods\n"
+            "====\n\n"
+            "Place Arma 3 mod folders here. Each mod folder must start with '@'.\n\n"
+            "Example layout:\n"
+            "  mods/\n"
+            "    @CBA_A3/\n"
+            "      addons/\n"
+            "    @ACE/\n"
+            "      addons/\n\n"
+            "After placing mods here:\n"
+            "  1. Go to the Mods tab in Languard.\n"
+            "  2. Select the mods you want to enable.\n"
+            "  3. Toggle 'Server-only' for mods that should use -serverMod= (e.g. task force radio server plugin).\n"
+            "  4. Click 'Apply Selection'.\n"
+            "  5. Restart the server for changes to take effect.\n\n"
+            "Mods with a mod.cpp file will display their friendly name in the UI.\n"
+            "Workshop mods with meta.cpp will show their Workshop ID."
+        ),
+    }
+
+    def get_dir_readme(self, dir_name: str) -> str | None:
+        return self._DIR_READMES.get(dir_name)

backend/core/servers/mods_router.py

@@ -24,8 +24,13 @@ def _ok(data):
     return {"success": True, "data": data, "error": None}
 
 
+class EnabledModEntry(BaseModel):
+    name: str
+    is_server_mod: bool = False
+
+
 class SetEnabledModsRequest(BaseModel):
-    mods: list[str]
+    mods: list[EnabledModEntry]
 
 
 def _get_mod_manager(server_id: int, game_type: str):
@@ -52,12 +57,15 @@ def list_mods(
     config_repo = ConfigRepository(db)
     try:
         available = mgr.list_available_mods()
-        enabled = set(mgr.get_enabled_mods(config_repo))
+        enabled_mods = mgr.get_enabled_mods(config_repo)
     except AdapterError as exc:
         raise HTTPException(status_code=500, detail={"code": "ADAPTER_ERROR", "message": str(exc)})
 
+    enabled_map = {m["name"]: m for m in enabled_mods}
     for mod in available:
-        mod["enabled"] = mod["name"] in enabled
+        entry = enabled_map.get(mod["name"])
+        mod["enabled"] = entry is not None
+        mod["is_server_mod"] = entry["is_server_mod"] if entry else False
 
     return _ok({
         "server_id": server_id,
@@ -83,7 +91,7 @@ def set_enabled_mods(
 
     config_repo = ConfigRepository(db)
     try:
-        mgr.set_enabled_mods(body.mods, config_repo)
+        mgr.set_enabled_mods([m.model_dump() for m in body.mods], config_repo)
     except AdapterError as exc:
         raise HTTPException(status_code=400, detail={"code": "ADAPTER_ERROR", "message": str(exc)})
     except ValueError as exc:
@@ -97,5 +105,5 @@ def set_enabled_mods(
 
     return _ok({
         "message": "Enabled mods updated. Restart the server for changes to take effect.",
-        "enabled_mods": body.mods,
+        "enabled_mods": [m.model_dump() for m in body.mods],
     })

backend/core/servers/service.py

@@ -126,9 +126,10 @@ class ServerService:
             max_restarts=max_restarts,
         )
 
-        # Create directory layout
+        # Create directory layout with per-directory README files
         layout = process_config.get_server_dir_layout()
-        ensure_server_dirs(server_id, layout)
+        readme_fn = getattr(process_config, "get_dir_readme", None)
+        ensure_server_dirs(server_id, layout, readme_provider=readme_fn)
 
         # Seed default config sections
         config_gen = adapter.get_config_generator()
@@ -242,17 +243,17 @@ class ServerService:
         # Get mod args if adapter supports mods
         mod_args: list[str] = []
         if adapter.has_capability("mod_manager"):
-            from sqlalchemy import text
-            mods = self._db.execute(
-                text("""
-                SELECT m.folder_path, sm.is_server_mod, sm.sort_order
-                FROM server_mods sm JOIN mods m ON m.id = sm.mod_id
-                WHERE sm.server_id = :sid ORDER BY sm.sort_order
-                """),
-                {"sid": server_id},
-            ).fetchall()
-            mod_list = [dict(r._mapping) for r in mods]
-            mod_args = adapter.get_mod_manager().build_mod_args(mod_list)
+            mod_mgr = adapter.get_mod_manager(server_id)
+            enabled_mods = mod_mgr.get_enabled_mods(self._config_repo)
+            server_dir = get_server_dir(server_id)
+            mod_list = [
+                {
+                    "folder_path": str(server_dir / "mods" / m["name"]),
+                    "game_data": {"is_server_mod": m.get("is_server_mod", False)},
+                }
+                for m in enabled_mods
+            ]
+            mod_args = mod_mgr.build_mod_args(mod_list)
 
         # Write config files (atomic)
         server_dir = get_server_dir(server_id)
@@ -273,7 +274,7 @@ class ServerService:
 
         # Build launch args
         try:
-            launch_args = config_gen.build_launch_args(raw_sections, mod_args)
+            launch_args = config_gen.build_launch_args(raw_sections, mod_args, server_dir=server_dir)
         except LaunchArgsError as e:
             raise HTTPException(
                 status_code=status.HTTP_400_BAD_REQUEST,

backend/core/utils/file_utils.py

@@ -3,6 +3,7 @@ from __future__ import annotations
 
 import re
 from pathlib import Path
+from typing import Callable
 
 
 def get_server_dir(server_id: int) -> Path:
@@ -12,16 +13,27 @@ def get_server_dir(server_id: int) -> Path:
     return base / str(server_id)
 
 
-def ensure_server_dirs(server_id: int, layout: list[str] | None = None) -> None:
+def ensure_server_dirs(
+    server_id: int,
+    layout: list[str] | None = None,
+    readme_provider: Callable[[str], str | None] | None = None,
+) -> None:
     """
     Create servers/{id}/ and any subdirectories from adapter layout.
-    layout example: ["server", "battleye", "mpmissions"]
+    If readme_provider is given, writes README.txt into each subdir (skips if file already exists).
     """
     server_dir = get_server_dir(server_id)
     server_dir.mkdir(parents=True, exist_ok=True)
     if layout:
         for subdir in layout:
-            (server_dir / subdir).mkdir(parents=True, exist_ok=True)
+            subdir_path = server_dir / subdir
+            subdir_path.mkdir(parents=True, exist_ok=True)
+            if readme_provider:
+                content = readme_provider(subdir)
+                if content:
+                    readme_path = subdir_path / "README.txt"
+                    if not readme_path.exists():
+                        readme_path.write_text(content, encoding="utf-8")
 
 
 def safe_delete_file(path: Path) -> bool:

backend/main.py

@@ -90,7 +90,24 @@ async def lifespan(app: FastAPI):
             except Exception as exc:
                 logger.error("Failed to reattach threads for server %d: %s", server["id"], exc)
 
-    # 8. Seed default admin if no users exist
+    # 8. Backfill server directory scaffold for existing servers (idempotent)
+    from core.dal.server_repository import ServerRepository as _ServerRepo
+    from core.utils.file_utils import ensure_server_dirs as _ensure_dirs
+    from adapters.registry import GameAdapterRegistry as _Registry
+    with engine.connect() as db:
+        for server in _ServerRepo(db).get_all():
+            try:
+                _adapter = _Registry.get(server["game_type"])
+                _pc = _adapter.get_process_config()
+                _ensure_dirs(
+                    server["id"],
+                    _pc.get_server_dir_layout(),
+                    readme_provider=getattr(_pc, "get_dir_readme", None),
+                )
+            except Exception as exc:
+                logger.warning("Dir scaffold failed for server %d: %s", server["id"], exc)
+
+    # 9. Seed default admin if no users exist
     from core.auth.service import AuthService
     with engine.connect() as db:
         svc = AuthService(db)
@@ -104,7 +121,7 @@ async def lifespan(app: FastAPI):
             logger.warning("  Change this password immediately!")
             logger.warning("=" * 60)
 
-    # 9. Register and start APScheduler cleanup jobs
+    # 10. Register and start APScheduler cleanup jobs
     from core.jobs.scheduler import start_scheduler, stop_scheduler
     from core.jobs.cleanup_jobs import register_cleanup_jobs
     register_cleanup_jobs()

backend/tests/adapters/arma3/test_config_schema.py

@@ -0,0 +1,89 @@
+"""Tests for Arma3ConfigGenerator.get_ui_schema() — advanced flag completeness."""
+import pytest
+from adapters.arma3.config_generator import Arma3ConfigGenerator
+
+BASIC_FIELDS = {
+    "server": {
+        "hostname", "max_players", "password", "password_admin",
+        "motd_lines", "motd_interval",
+        "forced_difficulty", "auto_select_mission", "random_mission_order",
+        "persistent", "skip_lobby", "drawing_in_map",
+        "battleye", "verify_signatures", "allowed_file_patching",
+        "disable_von", "von_codec",
+    },
+    "profile": {
+        "group_indicators", "friendly_tags", "enemy_tags",
+        "commands", "waypoints", "weapon_info", "stance_indicator",
+        "ai_level_preset", "skill_ai", "precision_ai",
+    },
+    "rcon": {"rcon_password", "enabled"},
+}
+
+ADVANCED_SAMPLES = {
+    "server": {
+        "server_command_password", "kick_duplicate", "vote_threshold",
+        "max_ping", "max_packet_loss", "disconnect_timeout",
+        "kick_on_ping", "log_file", "upnp", "loopback",
+        "admin_uids", "headless_clients", "local_clients",
+        "default_mission_params",
+    },
+    "basic": {
+        "min_bandwidth", "max_bandwidth", "max_msg_send",
+        "max_size_guaranteed", "min_error_to_send",
+    },
+    "profile": {
+        "reduced_damage", "tactical_ping", "weapon_crosshair",
+        "vision_aid", "third_person_view", "score_table",
+        "death_messages", "von_id",
+    },
+    "launch": {
+        "world", "limit_fps", "cpu_count", "max_mem",
+        "enable_ht", "huge_pages", "no_logs", "netlog",
+    },
+    "rcon": {"max_ping"},
+}
+
+
+@pytest.fixture
+def schema():
+    return Arma3ConfigGenerator().get_ui_schema()
+
+
+def test_every_visible_field_has_advanced_key(schema):
+    """Every non-hidden field must carry an explicit `advanced` bool."""
+    for section, fields in schema.items():
+        for field, entry in fields.items():
+            if entry.get("widget") == "hidden":
+                continue
+            assert "advanced" in entry, (
+                f"section={section!r} field={field!r} is missing 'advanced' key"
+            )
+
+
+def test_basic_fields_are_not_advanced(schema):
+    """Confirmed basic fields must have advanced=False."""
+    for section, field_names in BASIC_FIELDS.items():
+        for field in field_names:
+            entry = schema[section][field]
+            assert entry["advanced"] is False, (
+                f"section={section!r} field={field!r} should be basic (advanced=False)"
+            )
+
+
+def test_advanced_samples_are_marked_advanced(schema):
+    """Sampled advanced fields must have advanced=True."""
+    for section, field_names in ADVANCED_SAMPLES.items():
+        for field in field_names:
+            entry = schema[section][field]
+            assert entry["advanced"] is True, (
+                f"section={section!r} field={field!r} should be advanced (advanced=True)"
+            )
+
+
+def test_hidden_fields_excluded_from_advanced_requirement(schema):
+    """Hidden fields (e.g. missions) are exempt from the advanced check."""
+    for section, fields in schema.items():
+        for field, entry in fields.items():
+            if entry.get("widget") == "hidden":
+                # No advanced key required — just confirm widget is hidden
+                assert entry["widget"] == "hidden"

frontend/src/__tests__/ConfigEditorAdvanced.test.tsx

@@ -0,0 +1,210 @@
+/**
+ * TDD RED → GREEN: basic/advanced field filtering and profile section gate.
+ */
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { render, screen, fireEvent, waitFor } from "@testing-library/react";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+import type { ReactNode } from "react";
+
+vi.mock("@/lib/api", () => ({
+  apiClient: {
+    get: vi.fn(),
+    put: vi.fn(),
+    post: vi.fn(),
+    delete: vi.fn(),
+  },
+}));
+
+vi.mock("@/lib/logger", () => ({
+  logger: { error: vi.fn(), warn: vi.fn(), info: vi.fn(), debug: vi.fn() },
+}));
+
+import { apiClient } from "@/lib/api";
+import { ConfigEditor } from "@/components/servers/ConfigEditor";
+
+function createWrapper() {
+  const qc = new QueryClient({ defaultOptions: { queries: { retry: false } } });
+  return function Wrapper({ children }: { children: ReactNode }) {
+    return <QueryClientProvider client={qc}>{children}</QueryClientProvider>;
+  };
+}
+
+const BASIC_SERVER_SECTION = {
+  _meta: { config_version: "v1", schema_version: "1.1.0" },
+  hostname: "My Server",
+  max_players: 10,
+  kick_duplicate: 1,         // advanced
+  server_command_password: "",  // advanced
+  vote_threshold: 0.33,      // advanced
+};
+
+const SCHEMA_WITH_ADVANCED = {
+  server: {
+    hostname: { widget: "text", label: "Hostname", advanced: false },
+    max_players: { widget: "number", label: "Max Players", advanced: false },
+    kick_duplicate: { widget: "toggle", label: "Kick Duplicate", advanced: true },
+    server_command_password: { widget: "password", label: "SC Password", advanced: true },
+    vote_threshold: { widget: "number", label: "Vote Threshold", advanced: true },
+  },
+};
+
+const PROFILE_SECTION = {
+  _meta: { config_version: "v1", schema_version: "1.1.0" },
+  group_indicators: 1,
+  reduced_damage: 0,
+};
+
+const PROFILE_SCHEMA = {
+  profile: {
+    group_indicators: { widget: "toggle", label: "Group Indicators", advanced: false },
+    reduced_damage: { widget: "toggle", label: "Reduced Damage", advanced: true },
+  },
+};
+
+describe("ConfigEditor — basic/advanced filtering", () => {
+  beforeEach(() => {
+    vi.mocked(apiClient.get).mockReset();
+  });
+
+  function mockServerConfig(sections: Record<string, Record<string, unknown>>) {
+    const configMap: Record<string, unknown> = {};
+    for (const [k, v] of Object.entries(sections)) {
+      configMap[k] = v;
+    }
+    vi.mocked(apiClient.get).mockImplementation((url: string) => {
+      if (url.endsWith("/config/schema")) {
+        return Promise.resolve({ data: { success: true, data: { ...SCHEMA_WITH_ADVANCED } } });
+      }
+      if (url.endsWith("/config")) {
+        return Promise.resolve({ data: { success: true, data: configMap } });
+      }
+      if (url.includes("/config/")) {
+        const section = url.split("/config/")[1];
+        return Promise.resolve({ data: { success: true, data: sections[section] ?? {} } });
+      }
+      return Promise.resolve({ data: { success: true, data: {} } });
+    });
+  }
+
+  it("hides advanced fields by default", async () => {
+    mockServerConfig({ server: BASIC_SERVER_SECTION });
+    render(<ConfigEditor serverId={1} />, { wrapper: createWrapper() });
+
+    await screen.findByText("Hostname");
+    expect(screen.getByText("Hostname")).toBeInTheDocument();
+    expect(screen.queryByText("Kick Duplicate")).not.toBeInTheDocument();
+    expect(screen.queryByText("SC Password")).not.toBeInTheDocument();
+  });
+
+  it("shows advanced fields after clicking Show advanced", async () => {
+    mockServerConfig({ server: BASIC_SERVER_SECTION });
+    render(<ConfigEditor serverId={1} />, { wrapper: createWrapper() });
+
+    await screen.findByText("Hostname");
+    fireEvent.click(screen.getByText(/show advanced/i));
+
+    expect(screen.getByText("Kick Duplicate")).toBeInTheDocument();
+    expect(screen.getByText("SC Password")).toBeInTheDocument();
+  });
+
+  it("hides advanced fields again after toggling off", async () => {
+    mockServerConfig({ server: BASIC_SERVER_SECTION });
+    render(<ConfigEditor serverId={1} />, { wrapper: createWrapper() });
+
+    await screen.findByText("Hostname");
+    fireEvent.click(screen.getByText(/show advanced/i));
+    await screen.findByText("Kick Duplicate");
+    fireEvent.click(screen.getByText(/hide advanced/i));
+
+    await waitFor(() => {
+      expect(screen.queryByText("Kick Duplicate")).not.toBeInTheDocument();
+    });
+  });
+
+  it("shows all fields when no schema is available (graceful fallback)", async () => {
+    vi.mocked(apiClient.get).mockImplementation((url: string) => {
+      if (url.endsWith("/config")) {
+        return Promise.resolve({
+          data: { success: true, data: { server: BASIC_SERVER_SECTION } },
+        });
+      }
+      if (url.includes("/config/server")) {
+        return Promise.resolve({ data: { success: true, data: BASIC_SERVER_SECTION } });
+      }
+      if (url.endsWith("/config/schema")) {
+        return Promise.resolve({ data: { success: true, data: {} } }); // no schema
+      }
+      return Promise.resolve({ data: { success: true, data: {} } });
+    });
+
+    render(<ConfigEditor serverId={1} />, { wrapper: createWrapper() });
+    await screen.findByText("Hostname");
+    // Without schema, fields have no advanced flag — all should display
+    expect(screen.getByText("Hostname")).toBeInTheDocument();
+  });
+});
+
+describe("ConfigEditor — profile section gate", () => {
+  beforeEach(() => {
+    vi.mocked(apiClient.get).mockReset();
+  });
+
+  function mockWithDifficulty(difficulty: string) {
+    const serverSectionData = {
+      _meta: { config_version: "v1", schema_version: "1.1.0" },
+      forced_difficulty: difficulty,
+      hostname: "My Server",
+    };
+    vi.mocked(apiClient.get).mockImplementation((url: string) => {
+      if (url.endsWith("/config/schema")) {
+        return Promise.resolve({
+          data: {
+            success: true,
+            data: {
+              server: {
+                forced_difficulty: { widget: "select", label: "Difficulty", advanced: false, options: ["Recruit", "Regular", "Veteran", "Custom"] },
+                hostname: { widget: "text", label: "Hostname", advanced: false },
+              },
+              ...PROFILE_SCHEMA,
+            },
+          },
+        });
+      }
+      if (url.endsWith("/config")) {
+        return Promise.resolve({
+          data: { success: true, data: { server: serverSectionData, profile: PROFILE_SECTION } },
+        });
+      }
+      if (url.includes("/config/server")) {
+        return Promise.resolve({ data: { success: true, data: serverSectionData } });
+      }
+      if (url.includes("/config/profile")) {
+        return Promise.resolve({ data: { success: true, data: PROFILE_SECTION } });
+      }
+      return Promise.resolve({ data: { success: true, data: {} } });
+    });
+  }
+
+  it("shows profile warning banner when difficulty is not Custom", async () => {
+    mockWithDifficulty("Regular");
+    render(<ConfigEditor serverId={1} />, { wrapper: createWrapper() });
+
+    // Switch to Difficulty tab
+    await screen.findByText("Difficulty");
+    fireEvent.click(screen.getByText("Difficulty"));
+
+    await screen.findByText(/only apply when/i);
+  });
+
+  it("does not show profile warning banner when difficulty is Custom", async () => {
+    mockWithDifficulty("Custom");
+    render(<ConfigEditor serverId={1} />, { wrapper: createWrapper() });
+
+    await screen.findByText("Difficulty");
+    fireEvent.click(screen.getByText("Difficulty"));
+
+    // Fields should show without the gating banner
+    await screen.findByText("Group Indicators");
+    expect(screen.queryByText(/only apply when/i)).not.toBeInTheDocument();
+  });
+});

frontend/src/components/servers/ConfigEditor.tsx

@@ -35,6 +35,7 @@ export function ConfigEditor({ serverId }: ConfigEditorProps) {
   const isAdmin = useAuthStore((s) => s.user?.role === "admin");
   const addNotification = useUIStore((s) => s.addNotification);
   const { data: configMap, isLoading } = useServerConfig(serverId);
+  const { data: schema } = useServerConfigSchema(serverId);
 
   const sections = configMap ? Object.keys(configMap).filter((k) => k !== "_meta") : [];
   const [activeSection, setActiveSection] = useState<string>(sections[0] ?? "");
@@ -49,6 +50,11 @@ export function ConfigEditor({ serverId }: ConfigEditorProps) {
 
   const currentSection = activeSection || sections[0];
 
+  // Derive forced_difficulty from server section for profile gate
+  const serverSection = configMap["server"] as Record<string, unknown> | undefined;
+  const forcedDifficulty = serverSection?.["forced_difficulty"] as string | undefined;
+  const profileGated = currentSection === "profile" && forcedDifficulty !== "Custom";
+
   return (
     <div data-testid="config-editor">
       <div className="flex gap-1 mb-3 overflow-x-auto">
@@ -72,11 +78,18 @@ export function ConfigEditor({ serverId }: ConfigEditorProps) {
         <p className="text-text-muted text-xs mb-4">{SECTION_DESCRIPTIONS[currentSection]}</p>
       )}
 
+      {profileGated && (
+        <div className="rounded-lg border border-surface-raised bg-surface-overlay px-4 py-3 mb-4 text-sm text-text-secondary">
+          These settings only apply when <strong>Forced Difficulty</strong> is set to <strong>Custom</strong> in the Server tab. Current value: <em>{forcedDifficulty ?? "—"}</em>
+        </div>
+      )}
+
       {currentSection && (
         <ConfigSectionForm
           key={currentSection}
           serverId={serverId}
           section={currentSection}
+          sectionSchema={schema?.[currentSection] ?? {}}
           isAdmin={isAdmin}
           addNotification={addNotification}
         />
@@ -88,19 +101,21 @@ export function ConfigEditor({ serverId }: ConfigEditorProps) {
 function ConfigSectionForm({
   serverId,
   section,
+  sectionSchema,
   isAdmin,
   addNotification,
 }: {
   serverId: number;
   section: string;
+  sectionSchema: Record<string, FieldSchema>;
   isAdmin: boolean;
   addNotification: (n: { type: "success" | "error" | "info" | "warning"; message: string }) => void;
 }) {
   const { data: sectionData, isLoading } = useServerConfigSection(serverId, section);
-  const { data: schema } = useServerConfigSchema(serverId);
   const updateSection = useUpdateConfigSection(serverId, section);
   const [editValues, setEditValues] = useState<Record<string, unknown> | null>(null);
   const [showPassword, setShowPassword] = useState<Record<string, boolean>>({});
+  const [showAdvanced, setShowAdvanced] = useState(false);
 
   if (isLoading) {
     return <div className="text-text-muted text-sm">Loading section...</div>;
@@ -110,12 +125,23 @@ function ConfigSectionForm({
     return <div className="text-text-muted text-sm">No data for this section.</div>;
   }
 
-  const sectionSchema = schema?.[section] ?? {};
-  const fields = Object.entries(sectionData).filter(([key]) => {
+  const hasAdvancedFields = Object.values(sectionSchema).some((f) => f.advanced === true);
+
+  const allFields = Object.entries(sectionData).filter(([key]) => {
     if (key === "_meta") return false;
     if (sectionSchema[key]?.widget === "hidden") return false;
     return true;
   });
+
+  // When schema has advanced flags, filter by them; otherwise show everything
+  const schemaHasFlags = Object.keys(sectionSchema).length > 0 && Object.values(sectionSchema).some((f) => "advanced" in f);
+  const fields = schemaHasFlags
+    ? allFields.filter(([key]) => {
+        const fieldSchema = sectionSchema[key];
+        if (!fieldSchema || fieldSchema.advanced === undefined) return true;
+        return showAdvanced ? true : !fieldSchema.advanced;
+      })
+    : allFields;
   const meta = sectionData._meta;
   const displayValues = editValues ?? Object.fromEntries(fields);
   const isEditing = editValues !== null;
@@ -131,7 +157,11 @@ function ConfigSectionForm({
   };
 
   const handleSave = async () => {
-    if (!editValues || !meta) return;
+    if (!editValues) return;
+    if (!meta) {
+      addNotification({ type: "error", message: "Cannot save: config metadata is missing. Please refresh the page." });
+      return;
+    }
     try {
       await updateSection.mutateAsync({
         config_version: meta.config_version,
@@ -167,9 +197,19 @@ function ConfigSectionForm({
   return (
     <div className="space-y-3">
       <div className="flex items-center justify-between mb-2">
-        <p className="text-text-muted text-xs">
-          Version: {meta?.config_version ?? "--"} | Schema: {meta?.schema_version ?? "--"}
-        </p>
+        <div className="flex items-center gap-3">
+          <p className="text-text-muted text-xs">
+            Version: {meta?.config_version ?? "--"} | Schema: {meta?.schema_version ?? "--"}
+          </p>
+          {hasAdvancedFields && !isEditing && (
+            <button
+              onClick={() => setShowAdvanced((v) => !v)}
+              className="text-xs text-text-secondary hover:text-text-primary underline underline-offset-2"
+            >
+              {showAdvanced ? "Hide advanced" : "Show advanced"}
+            </button>
+          )}
+        </div>
         {isAdmin && !isEditing && (
           <button onClick={handleEdit} className="btn-ghost text-sm">
             Edit
@@ -197,7 +237,7 @@ function ConfigSectionForm({
                 onChange={(v) => handleChange(key, v)}
               />
             ) : widget === "toggle" ? (
-              <div className="flex-1 px-3 py-2">
+              <div className="flex items-center flex-1 px-1">
                 <ToggleDisplay value={rawValue} />
               </div>
             ) : widget === "select" ? (
@@ -267,9 +307,11 @@ function FieldWidget({
       const options = fieldSchema?.options ?? [];
       // Options may use "N - Description" format for numeric fields
       const isNumericOptions = options.length > 0 && /^\d+ /.test(options[0]);
-      const selectedOpt = isNumericOptions
-        ? (options.find((opt) => parseInt(opt, 10) === Number(value)) ?? String(value ?? ""))
-        : String(value ?? "");
+      const matchedOpt = isNumericOptions
+        ? options.find((opt) => parseInt(opt, 10) === Number(value))
+        : options.find((opt) => opt === String(value ?? ""));
+      // Fall back to first option when stored value has no match (avoids silent blank selection)
+      const selectedOpt = matchedOpt ?? options[0] ?? String(value ?? "");
       return (
         <select
           className="neu-input flex-1 text-sm"
@@ -293,11 +335,9 @@ function FieldWidget({
 
     case "toggle":
       return (
-        <input
-          type="checkbox"
-          className="w-5 h-5 accent-accent"
+        <ToggleSwitch
           checked={value === true || value === 1 || value === "true"}
-          onChange={(e) => onChange(e.target.checked ? 1 : 0)}
+          onChange={(checked) => onChange(checked ? 1 : 0)}
         />
       );
 
@@ -323,10 +363,13 @@ function FieldWidget({
         <input
           type="number"
           className="neu-input flex-1 text-sm"
-          value={String(value ?? "")}
+          value={value === null || value === undefined ? "" : String(value)}
           min={fieldSchema?.min}
           max={fieldSchema?.max}
-          onChange={(e) => onChange(Number(e.target.value))}
+          onChange={(e) => {
+            const v = e.target.value;
+            onChange(v === "" ? null : Number(v));
+          }}
         />
       );
 
@@ -362,13 +405,50 @@ function FieldWidget({
   }
 }
 
+function ToggleSwitch({ checked, onChange }: { checked: boolean; onChange: (v: boolean) => void }) {
+  return (
+    <button
+      type="button"
+      role="switch"
+      aria-checked={checked}
+      onClick={() => onChange(!checked)}
+      className={clsx(
+        "relative inline-flex h-6 w-11 shrink-0 items-center rounded-full",
+        "transition-colors duration-200 focus:outline-none focus:ring-2 focus:ring-accent focus:ring-offset-1 focus:ring-offset-surface-base",
+        checked
+          ? "bg-accent shadow-glow-amber"
+          : "bg-surface-overlay border border-surface-raised shadow-neu-recessed",
+      )}
+    >
+      <span
+        className={clsx(
+          "inline-block h-4 w-4 rounded-full shadow-md transform transition-transform duration-200",
+          checked ? "translate-x-6 bg-text-inverse" : "translate-x-1 bg-text-muted",
+        )}
+      />
+    </button>
+  );
+}
+
 function ToggleDisplay({ value }: { value: unknown }) {
   const on = value === true || value === 1 || value === "true" || value === "1";
   return (
-    <span className={clsx("inline-flex items-center gap-1.5 text-sm font-sans", on ? "text-green-400" : "text-text-muted")}>
-      <span className={clsx("w-3 h-3 rounded-full", on ? "bg-green-400" : "bg-surface-overlay border border-text-muted")} />
-      {on ? "Enabled" : "Disabled"}
-    </span>
+    <div
+      className={clsx(
+        "relative inline-flex h-6 w-11 shrink-0 items-center rounded-full cursor-not-allowed opacity-75",
+        on
+          ? "bg-accent shadow-glow-amber"
+          : "bg-surface-overlay border border-surface-raised shadow-neu-recessed",
+      )}
+      aria-hidden="true"
+    >
+      <span
+        className={clsx(
+          "inline-block h-4 w-4 rounded-full shadow-md transform",
+          on ? "translate-x-6 bg-text-inverse" : "translate-x-1 bg-text-muted",
+        )}
+      />
+    </div>
   );
 }
 

frontend/src/components/servers/ModList.tsx

@@ -1,5 +1,5 @@
 import { useState, useEffect } from "react";
-import { Save } from "lucide-react";
+import { Save, Server } from "lucide-react";
 
 import { useServerMods, useSetEnabledMods } from "@/hooks/useServerDetail";
 import type { Mod } from "@/hooks/useServerDetail";
@@ -38,14 +38,25 @@ export function ModList({ serverId }: ModListProps) {
     setAvailable((prev) => [...prev, { ...mod, enabled: false }].sort((a, b) => a.name.localeCompare(b.name)));
   };
 
+  const toggleServerMod = (modName: string) => {
+    setSelected((prev) =>
+      prev.map((m) => m.name === modName ? { ...m, is_server_mod: !m.is_server_mod } : m),
+    );
+  };
+
+  const _selectedKey = (mods: Mod[]) =>
+    mods.map((m) => `${m.name}:${m.is_server_mod}`).sort().join(",");
+
   const hasChanges = modsData !== undefined && (
-    selected.map((m) => m.name).sort().join(",") !==
-    (modsData.mods.filter((m) => m.enabled).map((m) => m.name).sort().join(","))
+    _selectedKey(selected) !==
+    _selectedKey(modsData.mods.filter((m) => m.enabled))
   );
 
   const handleApply = async () => {
     try {
-      await setEnabledMods.mutateAsync(selected.map((m) => m.name));
+      await setEnabledMods.mutateAsync(
+        selected.map((m) => ({ name: m.name, is_server_mod: m.is_server_mod })),
+      );
       addNotification({ type: "success", message: `${selected.length} mod(s) enabled. Server restart required.` });
     } catch (err) {
       logger.error("ModList", "Failed to apply mods: %s", err);
@@ -144,6 +155,7 @@ export function ModList({ serverId }: ModListProps) {
                   mod={mod}
                   actionLabel="←"
                   onAction={isAdmin ? () => moveToAvailable(mod) : undefined}
+                  onToggleServerMod={isAdmin ? () => toggleServerMod(mod.name) : undefined}
                   selected
                 />
               ))
@@ -159,17 +171,17 @@ function ModRow({
   mod,
   actionLabel,
   onAction,
+  onToggleServerMod,
   selected = false,
 }: {
   mod: Mod;
   actionLabel: string;
   onAction?: () => void;
+  onToggleServerMod?: () => void;
   selected?: boolean;
 }) {
   return (
-    <div
-      className="flex items-center gap-2 px-2 py-1.5 rounded-lg bg-surface-recessed shadow-neu-recessed"
-    >
+    <div className="flex items-center gap-2 px-2 py-1.5 rounded-lg bg-surface-recessed shadow-neu-recessed">
       <div className="flex-1 min-w-0">
         <p className="text-text-primary text-sm font-medium truncate">
           {mod.display_name ?? mod.name}
@@ -186,6 +198,21 @@ function ModRow({
           <span className="text-text-muted text-xs">{formatSize(mod.size_bytes)}</span>
         </div>
       </div>
+      {selected && onToggleServerMod && (
+        <button
+          type="button"
+          onClick={onToggleServerMod}
+          title={mod.is_server_mod ? "Server-only mod (-serverMod). Click to switch to client mod (-mod)" : "Client mod (-mod). Click to switch to server-only (-serverMod)"}
+          className={`flex items-center gap-1 text-xs px-1.5 py-0.5 rounded shrink-0 transition-colors ${
+            mod.is_server_mod
+              ? "bg-amber-500/20 text-amber-400"
+              : "bg-surface-raised text-text-muted hover:text-text-secondary"
+          }`}
+        >
+          <Server size={10} />
+          {mod.is_server_mod ? "Server" : "Client"}
+        </button>
+      )}
       {onAction && (
         <button
           type="button"

frontend/src/hooks/useServerDetail.ts

@@ -124,10 +124,16 @@ export interface Mod {
   path: string;
   size_bytes: number;
   enabled: boolean;
+  is_server_mod: boolean;
   display_name: string | null;
   workshop_id: string | null;
 }
 
+export interface EnabledModEntry {
+  name: string;
+  is_server_mod: boolean;
+}
+
 export interface FieldSchema {
   widget: "text" | "number" | "password" | "textarea" | "select" | "toggle" | "tag-list" | "hidden" | "key-value";
   label?: string;
@@ -135,6 +141,7 @@ export interface FieldSchema {
   min?: number;
   max?: number;
   options?: string[];
+  advanced?: boolean;
 }
 
 export interface ConfigSchema {
@@ -380,7 +387,7 @@ export function useDeleteMission(serverId: number) {
 export function useSetEnabledMods(serverId: number) {
   const queryClient = useQueryClient();
   return useMutation({
-    mutationFn: (mods: string[]) =>
+    mutationFn: (mods: EnabledModEntry[]) =>
       apiClient.put(`/api/servers/${serverId}/mods/enabled`, { mods }),
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: ["mods", serverId] });