feat: Steam game & library detection (M6) — 0.8.0

The first slice of M6 (gaming-environment checks): detect a user's Steam
libraries and the games installed in each — also the D12 "pick a game"
foundation.

- core/steam.py: multi-install/library discovery (libraryfolders.vdf, symlink
  dedupe, native/Flatpak/Snap), appmanifest_*.acf scan with runtime/Proton/
  redist filtering, scan cache + new-game diff. Stdlib only. VDF keys read
  case-insensitively (e.g. lastupdated vs SizeOnDisk).
- Libraries are opt-in (config steam_libraries); the flat TOML writer now
  emits list/array values.
- GUI Games page: library checkboxes with per-library counts, game list,
  background rescan on every launch, NEW badge + sidebar count for games
  installed since the last scan (acknowledged when viewed).
- CLI: rigdoctor games / games libraries [--enable|--disable|--all|--json]
  (headless-complete, D17).
- Tests for VDF parse, scan, tool filter, cache diff, config list round-trip.
- Docs (MODULES/ROADMAP) updated; version 0.7.3 -> 0.8.0.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -5,6 +5,22 @@ All notable changes to RigDoctor are recorded here. Format follows
 (`MAJOR.MINOR.PATCH`, pre-1.0). `__version__` and `pyproject.toml` must match the git
 release tag (so the auto-updater, D18, can compare versions).
 
+## [0.8.0] - 2026-05-22
+### Added
+- **Gaming environment checks (M6) — Steam game detection.** RigDoctor now finds your Steam
+  libraries (across multiple drives, via `libraryfolders.vdf`) and the games installed in each
+  (parsing `appmanifest_*.acf` — stdlib only, no Steam tooling needed). Runtimes, Proton builds,
+  and redistributables are filtered out.
+  - **Opt-in libraries:** detected libraries are listed with a per-library game count; you check
+    the ones to scan. Nothing is scanned until you pick a library.
+  - **Background scan on every launch:** the GUI rescans the selected libraries in the background
+    when it opens and flags games installed since the last scan with a **NEW** badge plus a count
+    on the **Games** sidebar item (cleared when you view the page). Results are cached
+    (`~/.local/state/rigdoctor/games.json`) so the list shows instantly.
+  - **CLI:** `rigdoctor games` lists detected games; `rigdoctor games libraries
+    [--enable PATH | --disable PATH | --all]` lists/selects libraries (headless-complete, D17).
+- Config now supports list values (TOML arrays); `steam_libraries` records the selected libraries.
+
 ## [0.7.3] - 2026-05-21
 ### Fixed
 - Shared terminal now has **scrollback** — large output (e.g. `ls -la`) can be scrolled up to

docs/MODULES.md

@@ -14,7 +14,7 @@ Status: ⬜ not started · 🟦 designing · 🟨 in progress · ✅ done
 | M2 | Live monitor (TUI) | Monitoring | none (stdlib curses) | all | P1 | ⬜ |
 | M8 | Alerting | Monitoring | libnotify (opt) | all | P2 | 🟨 |
 | M5 | System inventory | Diagnostics | none (opt: lm-sensors, dmidecode) | all | P1 | 🟨 |
-| M6 | Gaming env checks | Diagnostics | none | all | P2 | ⬜ |
+| M6 | Gaming env checks | Diagnostics | none | all | P2 | 🟨 |
 | M10 | Desktop GUI | Desktop UI | **python3-pyside6** | all | P2 | 🟨 |
 | M11 | Tray / menu-bar applet | Desktop UI | **python3-pyside6** (+ AppIndicator on GNOME) | all | P2 | ⬜ |
 | M9 | Installer | (meta) | none | all | P1 | 🟨 |
@@ -41,7 +41,15 @@ Status: ⬜ not started · 🟦 designing · 🟨 in progress · ✅ done
   (text/JSON) + GUI Health tab. GPU-firmware verification deferred.
 - **M2 Live monitor** — depends on M1; the terminal "HWMonitor for Linux" face. Stdlib-only.
 - **M5 / M6 Diagnostics** — inventory export + gaming-env checks; M6 flags risky settings and
-  suggests the fix command but does not apply it (D9).
+  suggests the fix command but does not apply it (D9). *M6 implemented (Steam detection first —
+  the D12 "pick a game" foundation):* discovers Steam installs + all library folders
+  (`libraryfolders.vdf`, multi-drive) and the games in each (`appmanifest_*.acf`), filtering
+  runtimes/Proton/redistributables — stdlib only. **Libraries are opt-in** (`steam_libraries`
+  config); the GUI **Games** page lists them with per-library counts and rescans in the
+  background on every launch, badging games installed since the last scan (cached in
+  `state/games.json`). CLI: `rigdoctor games` / `games libraries [--enable|--disable|--all]`.
+  *Pending:* the env-check probes (CPU governor, GPU persistence, GameMode/MangoHud, swappiness,
+  hugepages, mitigations, PCIe ASPM) and non-Steam launchers (Lutris/Heroic).
 - **M8 Alerting** — threshold/event notifications; integrates with the tray applet (M11).
 - **M10 Desktop GUI** — PySide6 graphical front-end over the core engine (dashboard, log
   browser, report viewer, logger controls). Optional; adds the Qt dependency. *Bootstrapped

docs/ROADMAP.md

@@ -27,7 +27,11 @@ Ubuntu + NVIDIA first; `.deb` distribution (see `DECISIONS.md`).
 
 ## Phase 3 — Diagnostics breadth
 - [ ] M5 system inventory + exportable report
-- [ ] M6 gaming environment checks (suggest-only)
+- [~] M6 gaming environment checks (suggest-only) — *Steam game/library detection done*
+      (multi-library `libraryfolders.vdf` discovery + `appmanifest` scan, opt-in libraries,
+      launch-time background rescan with new-game badge; CLI `rigdoctor games`, GUI Games page).
+      This is also the D12 "pick a game" foundation. *Pending:* the env-check probes (governor,
+      GPU persistence, GameMode/MangoHud, swappiness, hugepages, mitigations, PCIe ASPM).
 - [ ] SMART integration (smartmontools if present)
 
 ## Phase 4 — Desktop UI & installer

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "rigdoctor"
-version = "0.7.3"
+version = "0.8.0"
 description = "Modular hardware monitoring & crash diagnostics for Linux gamers."
 readme = "README.md"
 requires-python = ">=3.11"

src/rigdoctor/__init__.py

@@ -1,3 +1,3 @@
 """RigDoctor — modular hardware monitoring & crash diagnostics for Linux gamers."""
 
-__version__ = "0.7.3"
+__version__ = "0.8.0"

src/rigdoctor/cli.py

@@ -345,6 +345,73 @@ def cmd_report(args) -> int:
     return 0
 
 
+def cmd_games(args) -> int:
+    from .core import steam
+
+    selected = steam.selected_library_paths()
+    if not selected:
+        print("No Steam libraries selected to scan.")
+        print("  See them with:   rigdoctor games libraries")
+        print("  Then enable one: rigdoctor games libraries --enable <path>  (or --all)")
+        return 1
+    result = steam.rescan()
+    if args.json:
+        from dataclasses import asdict
+
+        print(json.dumps({
+            "scanned_at": result.scanned_at,
+            "new_appids": result.new_appids,
+            "games": [asdict(g) for g in result.games],
+        }, indent=2, ensure_ascii=False))
+        return 0
+    if not result.games:
+        print("No games found in the selected Steam libraries.")
+        return 0
+    new = set(result.new_appids)
+    print(f"{len(result.games)} game(s) across {len(selected)} librar(y/ies):\n")
+    for g in result.games:
+        flag = " NEW" if g.appid in new else ""
+        print(f"  {g.name:<48} {steam.human_size(g.size_bytes):>9}{flag}")
+    if new:
+        print(f"\n{len(new)} newly-installed since the last scan.")
+    return 0
+
+
+def cmd_games_libraries(args) -> int:
+    from .core import steam
+
+    discovered = steam.discover_libraries()
+    selected = {os.path.realpath(p) for p in steam.selected_library_paths()}
+
+    # --all / --enable / --disable adjust the selection, then we list the result.
+    if args.all or args.enable or args.disable:
+        if args.all:
+            selected = {lib.path for lib in discovered}
+        for raw in args.enable or []:
+            selected.add(os.path.realpath(os.path.expanduser(raw)))
+        for raw in args.disable or []:
+            selected.discard(os.path.realpath(os.path.expanduser(raw)))
+        config.update_config(steam_libraries=sorted(selected))
+
+    if not discovered:
+        print("No Steam libraries detected (is Steam installed?).")
+        return 1
+    if args.json:
+        print(json.dumps([
+            {"path": lib.path, "label": lib.label, "selected": lib.path in selected,
+             "games": len(steam.scan_library(lib.path))}
+            for lib in discovered
+        ], indent=2, ensure_ascii=False))
+        return 0
+    print("Steam libraries (checked = scanned for games):\n")
+    for lib in discovered:
+        mark = "x" if lib.path in selected else " "
+        count = len(steam.scan_library(lib.path))
+        label = f"  [{lib.label}]" if lib.label else ""
+        print(f"  [{mark}] {lib.path}{label}  ({count} games)")
+    return 0
+
+
 def build_parser() -> argparse.ArgumentParser:
     p = argparse.ArgumentParser(
         prog="rigdoctor",
@@ -423,6 +490,17 @@ def build_parser() -> argparse.ArgumentParser:
     inv.add_argument("--markdown", action="store_true", help="output Markdown (for forum/bug reports)")
     inv.add_argument("-o", "--output", default=None, help="write to a file instead of stdout")
     inv.set_defaults(func=cmd_inventory)
+
+    games_p = sub.add_parser("games", help="Steam game & library detection (M6)")
+    games_p.add_argument("--json", action="store_true", help="output JSON")
+    games_p.set_defaults(func=cmd_games)
+    games_sub = games_p.add_subparsers(dest="games_cmd")
+    lib_p = games_sub.add_parser("libraries", help="list/select Steam libraries to scan")
+    lib_p.add_argument("--enable", action="append", metavar="PATH", help="scan this library (repeatable)")
+    lib_p.add_argument("--disable", action="append", metavar="PATH", help="stop scanning this library (repeatable)")
+    lib_p.add_argument("--all", action="store_true", help="scan all detected libraries")
+    lib_p.add_argument("--json", action="store_true", help="output JSON")
+    lib_p.set_defaults(func=cmd_games_libraries)
     return p
 
 

src/rigdoctor/config.py

@@ -27,6 +27,10 @@ STATUS_FILE = STATE_DIR / "recorder.json"
 PID_FILE = STATE_DIR / "recorder.pid"
 SPAWN_LOG = STATE_DIR / "recorder.out"
 
+# Gaming environment / game detection (M6) — cached Steam game scan (mutable state,
+# not config: refreshed by the background scan on every launch).
+GAMES_FILE = STATE_DIR / "games.json"
+
 # Update access token (M13) — gates updates to Gitea account holders (D18).
 # Stored in the OS keyring (Secret Service / GNOME Keyring) via `secret-tool` when
 # available — encrypted at rest, unlocked with the login session — else a 0600 file.
@@ -143,6 +147,7 @@ DEFAULTS: dict = {
     "gpu_temp_alert": 90.0,       # °C — alert when GPU reaches this
     "cpu_temp_alert": 95.0,       # °C — alert when CPU reaches this
     "relay_url": "wss://rigdoctor.jesseyvanofferen.com",  # session-sharing relay (M12)
+    "steam_libraries": [],        # Steam library paths to scan for games (M6); empty = none picked yet
 }
 
 
@@ -165,6 +170,8 @@ def _toml_value(value) -> str:
         return "true" if value else "false"
     if isinstance(value, (int, float)):
         return repr(value)
+    if isinstance(value, (list, tuple)):
+        return "[" + ", ".join(_toml_value(v) for v in value) + "]"
     return '"' + str(value).replace("\\", "\\\\").replace('"', '\\"') + '"'
 
 

src/rigdoctor/core/steam.py

@@ -0,0 +1,340 @@
+"""Steam library & game detection (M6, the Steam piece of D12 game detection).
+
+Discovers a user's Steam installs, the library folders they've configured (Steam tracks
+them all in ``libraryfolders.vdf``, so multiple libraries on multiple drives are covered),
+and the games installed in each (one ``appmanifest_<appid>.acf`` per app). Stdlib only —
+no Steam tooling required, every probe degrades gracefully.
+
+The set of libraries actually scanned is user-chosen (config ``steam_libraries``); nothing
+is scanned until the user opts a library in. Scan results are cached in ``games.json`` so the
+GUI can show the list instantly and the launch-time background scan can diff against it to
+flag newly-installed games.
+"""
+
+from __future__ import annotations
+
+import json
+import os
+import time
+from dataclasses import asdict, dataclass
+from pathlib import Path
+
+from ..config import GAMES_FILE, load_config
+
+# Steam "apps" that aren't games: runtimes, Proton builds, redistributables. Filtered out of
+# scans by appid (known IDs) or by name prefix (covers future Proton/runtime versions).
+_TOOL_APPIDS = {
+    "228980",   # Steamworks Common Redistributables
+    "1070560",  # Steam Linux Runtime 1.0 (scout)
+    "1391110",  # Steam Linux Runtime 2.0 (soldier)
+    "1628350",  # Steam Linux Runtime 3.0 (sniper)
+    "1493710",  # Proton Experimental
+    "2180100",  # Proton Hotfix
+    "1826330",  # Proton EasyAntiCheat Runtime
+    "1161040",  # Proton BattlEye Runtime
+}
+_TOOL_NAME_PREFIXES = ("Proton", "Steam Linux Runtime", "Steamworks Common")
+
+# Where Steam may be installed (native + Flatpak + Snap). Symlinks (~/.steam/steam) are
+# resolved and de-duplicated by real path.
+_ROOT_CANDIDATES = (
+    "~/.steam/steam",
+    "~/.steam/root",
+    "~/.local/share/Steam",
+    "~/.var/app/com.valvesoftware.Steam/data/Steam",  # Flatpak
+    "~/snap/steam/common/.local/share/Steam",          # Snap
+)
+
+
+@dataclass
+class SteamLibrary:
+    path: str          # the library root (contains a steamapps/ dir)
+    label: str = ""    # Steam's label for the folder, if any
+
+
+@dataclass
+class Game:
+    appid: str
+    name: str
+    library: str       # library path the game lives in
+    installdir: str    # folder name under <library>/steamapps/common
+    size_bytes: int = 0
+    last_updated: int = 0  # epoch seconds (acf LastUpdated), 0 if unknown
+
+
+# --- VDF (Valve Data Format) parsing --------------------------------------------------
+# Minimal text-VDF reader: quoted "key" "value" pairs and "key" { ... } nesting. Enough
+# for libraryfolders.vdf and appmanifest_*.acf; ignores #base/#include and unquoted tokens.
+
+def _parse_vdf(text: str) -> dict:
+    pos = 0
+    n = len(text)
+
+    def skip_ws() -> None:
+        nonlocal pos
+        while pos < n:
+            c = text[pos]
+            if c in " \t\r\n":
+                pos += 1
+            elif c == "/" and pos + 1 < n and text[pos + 1] == "/":  # // line comment
+                while pos < n and text[pos] != "\n":
+                    pos += 1
+            else:
+                break
+
+    def read_string() -> str:
+        nonlocal pos
+        pos += 1  # opening quote
+        out = []
+        while pos < n:
+            c = text[pos]
+            if c == "\\" and pos + 1 < n:
+                nxt = text[pos + 1]
+                out.append({"n": "\n", "t": "\t", "\\": "\\", '"': '"'}.get(nxt, nxt))
+                pos += 2
+                continue
+            if c == '"':
+                pos += 1
+                break
+            out.append(c)
+            pos += 1
+        return "".join(out)
+
+    def parse_obj() -> dict:
+        nonlocal pos
+        obj: dict = {}
+        while True:
+            skip_ws()
+            if pos >= n or text[pos] == "}":
+                pos += 1  # consume closing brace (or run off the end)
+                return obj
+            if text[pos] != '"':  # skip unquoted/unsupported tokens defensively
+                pos += 1
+                continue
+            key = read_string()
+            skip_ws()
+            if pos < n and text[pos] == "{":
+                pos += 1
+                obj[key] = parse_obj()
+            elif pos < n and text[pos] == '"':
+                obj[key] = read_string()
+            else:  # malformed; bail on this key
+                obj[key] = ""
+        return obj
+
+    skip_ws()
+    if pos < n and text[pos] == '"':
+        root_key = read_string()
+        skip_ws()
+        if pos < n and text[pos] == "{":
+            pos += 1
+            return {root_key: parse_obj()}
+    return {}
+
+
+def _read_vdf(path: Path) -> dict:
+    try:
+        return _parse_vdf(path.read_text(encoding="utf-8", errors="replace"))
+    except OSError:
+        return {}
+
+
+# --- discovery ------------------------------------------------------------------------
+
+def steam_roots() -> list[Path]:
+    """Existing Steam install roots, de-duplicated by resolved path."""
+    seen: set[Path] = set()
+    roots: list[Path] = []
+    for cand in _ROOT_CANDIDATES:
+        p = Path(os.path.expanduser(cand))
+        if not p.exists():
+            continue
+        real = p.resolve()
+        if real in seen:
+            continue
+        seen.add(real)
+        roots.append(real)
+    return roots
+
+
+def _libraryfolders_vdf(root: Path) -> Path | None:
+    for rel in ("steamapps/libraryfolders.vdf", "config/libraryfolders.vdf"):
+        p = root / rel
+        if p.exists():
+            return p
+    return None
+
+
+def discover_libraries() -> list[SteamLibrary]:
+    """Every Steam library folder configured on this machine, de-duplicated by real path.
+
+    Reads each install's ``libraryfolders.vdf`` (which lists all drives/folders), and
+    always includes the install root itself as a fallback.
+    """
+    seen: set[Path] = set()
+    libs: list[SteamLibrary] = []
+
+    def add(path: Path, label: str = "") -> None:
+        if not (path / "steamapps").is_dir():
+            return
+        real = path.resolve()
+        if real in seen:
+            return
+        seen.add(real)
+        libs.append(SteamLibrary(path=str(real), label=label))
+
+    for root in steam_roots():
+        vdf = _libraryfolders_vdf(root)
+        folders = _read_vdf(vdf).get("libraryfolders", {}) if vdf else {}
+        if isinstance(folders, dict):
+            for entry in folders.values():
+                if isinstance(entry, dict) and entry.get("path"):
+                    add(Path(entry["path"]), entry.get("label", ""))
+        add(root)  # the install root is itself a library
+    return libs
+
+
+# --- game scanning --------------------------------------------------------------------
+
+def is_tool(appid: str, name: str) -> bool:
+    """True for non-game Steam apps (runtimes, Proton, redistributables)."""
+    if appid in _TOOL_APPIDS:
+        return True
+    return name.startswith(_TOOL_NAME_PREFIXES)
+
+
+def scan_library(library: str) -> list[Game]:
+    """Games installed in one library, parsed from its appmanifest_*.acf files."""
+    steamapps = Path(library) / "steamapps"
+    games: list[Game] = []
+    try:
+        manifests = sorted(steamapps.glob("appmanifest_*.acf"))
+    except OSError:
+        return games
+    for manifest in manifests:
+        state = _read_vdf(manifest).get("AppState", {})
+        if not isinstance(state, dict):
+            continue
+        # Steam treats VDF keys case-insensitively (e.g. "SizeOnDisk" but "lastupdated").
+        state = {k.lower(): v for k, v in state.items()}
+        appid = state.get("appid", "")
+        name = state.get("name", "").strip()
+        if not appid or not name or is_tool(appid, name):
+            continue
+        games.append(Game(
+            appid=appid,
+            name=name,
+            library=str(library),
+            installdir=state.get("installdir", ""),
+            size_bytes=_int(state.get("sizeondisk")),
+            last_updated=_int(state.get("lastupdated")),
+        ))
+    return games
+
+
+def scan_games(libraries: list[str]) -> list[Game]:
+    """All games across the given libraries, de-duplicated by appid, sorted by name."""
+    by_appid: dict[str, Game] = {}
+    for lib in libraries:
+        for game in scan_library(lib):
+            by_appid.setdefault(game.appid, game)  # first library wins on duplicates
+    return sorted(by_appid.values(), key=lambda g: g.name.lower())
+
+
+def _int(value) -> int:
+    try:
+        return int(value)
+    except (TypeError, ValueError):
+        return 0
+
+
+# --- config-driven selection ----------------------------------------------------------
+
+def selected_library_paths(cfg: dict | None = None) -> list[str]:
+    """Library paths the user has opted in to scanning (config ``steam_libraries``)."""
+    cfg = cfg or load_config()
+    paths = cfg.get("steam_libraries") or []
+    return [str(p) for p in paths]
+
+
+# --- scan cache + new-game detection --------------------------------------------------
+
+@dataclass
+class ScanResult:
+    games: list[Game]
+    new_appids: list[str]   # newly-installed since the last scan (badge fuel)
+    scanned_at: float
+
+
+def load_cache() -> dict | None:
+    try:
+        return json.loads(GAMES_FILE.read_text())
+    except (OSError, ValueError):
+        return None
+
+
+def _save_cache(games: list[Game], known: set[str], new: list[str], when: float) -> None:
+    GAMES_FILE.parent.mkdir(parents=True, exist_ok=True)
+    data = {
+        "scanned_at": when,
+        "known_appids": sorted(known),
+        "new_appids": new,
+        "games": [asdict(g) for g in games],
+    }
+    GAMES_FILE.write_text(json.dumps(data, indent=2, ensure_ascii=False))
+
+
+def cached_games() -> list[Game]:
+    """Games from the last scan (for instant display before a rescan finishes)."""
+    cache = load_cache()
+    if not cache:
+        return []
+    return [Game(**{k: g.get(k) for k in Game.__dataclass_fields__}) for g in cache.get("games", [])]
+
+
+def rescan(cfg: dict | None = None) -> ScanResult:
+    """Scan the selected libraries, diff against the cache, and persist the result.
+
+    Newly-installed games (appids never seen before) are reported in ``new_appids``. The
+    very first scan reports nothing as new (so the whole library isn't flagged at once);
+    unacknowledged new games carry forward until they're acknowledged or uninstalled.
+    """
+    games = scan_games(selected_library_paths(cfg))
+    current = {g.appid for g in games}
+    prev = load_cache()
+    if prev is None:
+        known: set[str] = set(current)  # first run: everything is "known", nothing new
+        new = []
+    else:
+        known = set(prev.get("known_appids", []))
+        carried = set(prev.get("new_appids", [])) & current  # still-unacknowledged & installed
+        new = sorted((current - known) | carried)
+        known |= current
+    when = time.time()
+    _save_cache(games, known, new, when)
+    return ScanResult(games=games, new_appids=new, scanned_at=when)
+
+
+def acknowledge_new() -> None:
+    """Clear the new-game badge (called when the user views the games list)."""
+    cache = load_cache()
+    if not cache or not cache.get("new_appids"):
+        return
+    cache["new_appids"] = []
+    try:
+        GAMES_FILE.write_text(json.dumps(cache, indent=2, ensure_ascii=False))
+    except OSError:
+        pass
+
+
+# --- formatting -----------------------------------------------------------------------
+
+def human_size(num_bytes: int) -> str:
+    if num_bytes <= 0:
+        return "—"
+    size = float(num_bytes)
+    for unit in ("B", "KB", "MB", "GB", "TB"):
+        if size < 1024 or unit == "TB":
+            return f"{size:.0f} {unit}" if unit in ("B", "KB") else f"{size:.1f} {unit}"
+        size /= 1024
+    return f"{size:.1f} TB"

src/rigdoctor/gui/games_page.py

@@ -0,0 +1,249 @@
+"""Games page (M6 in the GUI): pick Steam libraries and browse detected games.
+
+Libraries are opt-in — the user checks which ones to scan. The list is loaded from the
+cache instantly, then a background rescan refreshes it and flags games installed since the
+last scan (a "NEW" badge here + a count on the sidebar nav).
+"""
+
+from __future__ import annotations
+
+import os
+import threading
+import time
+
+from PySide6.QtCore import Qt, QTimer, Signal
+from PySide6.QtWidgets import (
+    QCheckBox,
+    QFrame,
+    QHBoxLayout,
+    QLabel,
+    QPushButton,
+    QScrollArea,
+    QVBoxLayout,
+    QWidget,
+)
+
+from ..config import load_config, update_config
+from .theme import ACCENT, GOOD, MUTED
+
+
+def _game_row(name: str, sublabel: str, size: str, is_new: bool) -> QFrame:
+    card = QFrame()
+    card.setObjectName("Card")
+    h = QHBoxLayout(card)
+    h.setContentsMargins(16, 10, 16, 10)
+    h.setSpacing(10)
+
+    left = QVBoxLayout()
+    left.setSpacing(2)
+    title = QLabel(name)
+    title.setStyleSheet("font-weight: 600; background: transparent;")
+    title.setWordWrap(True)
+    left.addWidget(title)
+    if sublabel:
+        sub = QLabel(sublabel)
+        sub.setObjectName("Muted")
+        left.addWidget(sub)
+    h.addLayout(left, 1)
+
+    if is_new:
+        badge = QLabel("NEW")
+        badge.setStyleSheet(
+            f"color: {GOOD}; border: 1px solid {GOOD}; border-radius: 6px; "
+            f"padding: 1px 6px; font-weight: 700; background: transparent;"
+        )
+        h.addWidget(badge, 0, Qt.AlignmentFlag.AlignVCenter)
+
+    size_label = QLabel(size)
+    size_label.setObjectName("Muted")
+    size_label.setMinimumWidth(80)
+    size_label.setAlignment(Qt.AlignmentFlag.AlignRight | Qt.AlignmentFlag.AlignVCenter)
+    h.addWidget(size_label, 0)
+    return card
+
+
+class GamesPage(QWidget):
+    _libraries_ready = Signal(object)  # list[dict(path, label, count, selected)]
+    _scanned = Signal(object)          # steam.ScanResult
+    new_count_changed = Signal(int)    # newly-installed game count (for the nav badge)
+
+    def __init__(self) -> None:
+        super().__init__()
+        self.setObjectName("Page")
+        self._libraries_ready.connect(self._render_libraries)
+        self._scanned.connect(self._render_games)
+        self._busy = False
+        self._new_appids: set[str] = set()
+
+        root = QVBoxLayout(self)
+        root.setContentsMargins(20, 18, 20, 18)
+        root.setSpacing(16)
+
+        header = QHBoxLayout()
+        title = QLabel("Games")
+        title.setObjectName("PageTitle")
+        header.addWidget(title)
+        header.addStretch(1)
+        self._status = QLabel("")
+        self._status.setObjectName("Muted")
+        header.addWidget(self._status)
+        self._rescan_btn = QPushButton("Rescan")
+        self._rescan_btn.setObjectName("PrimaryButton")
+        self._rescan_btn.clicked.connect(self.refresh)
+        header.addWidget(self._rescan_btn)
+        root.addLayout(header)
+
+        # Libraries (opt-in checkboxes)
+        lib_card = QFrame()
+        lib_card.setObjectName("Card")
+        lib_v = QVBoxLayout(lib_card)
+        lib_v.setContentsMargins(16, 12, 16, 12)
+        lib_v.setSpacing(6)
+        lib_head = QLabel("Steam libraries")
+        lib_head.setStyleSheet("font-weight: 700; background: transparent;")
+        lib_v.addWidget(lib_head)
+        self._lib_box = QVBoxLayout()
+        self._lib_box.setSpacing(6)
+        lib_v.addLayout(self._lib_box)
+        self._lib_hint = QLabel("Looking for Steam libraries…")
+        self._lib_hint.setObjectName("Muted")
+        self._lib_hint.setWordWrap(True)
+        lib_v.addWidget(self._lib_hint)
+        root.addWidget(lib_card)
+
+        # Games list
+        scroll = QScrollArea()
+        scroll.setWidgetResizable(True)
+        scroll.setFrameShape(QFrame.Shape.NoFrame)
+        scroll.setStyleSheet("background: transparent;")
+        self._container = QWidget()
+        self._list = QVBoxLayout(self._container)
+        self._list.setContentsMargins(0, 0, 0, 0)
+        self._list.setSpacing(8)
+        self._list.setAlignment(Qt.AlignmentFlag.AlignTop)
+        scroll.setWidget(self._container)
+        root.addWidget(scroll, 1)
+
+        self._load_cached()                       # instant display from the last scan
+        QTimer.singleShot(400, self.refresh)      # then rescan in the background on launch
+
+    # --- loading ----------------------------------------------------------------------
+
+    def _load_cached(self) -> None:
+        from ..core import steam
+
+        cache = steam.load_cache() or {}
+        self._new_appids = set(cache.get("new_appids", []))
+        games = steam.cached_games()
+        if games:
+            self._populate_games(games, self._new_appids)
+        self.new_count_changed.emit(len(self._new_appids))
+
+    def refresh(self) -> None:
+        if self._busy:
+            return
+        self._busy = True
+        self._rescan_btn.setEnabled(False)
+        self._status.setText("Scanning Steam libraries…")
+        threading.Thread(target=self._work, daemon=True).start()
+
+    def _work(self) -> None:
+        from ..core import steam
+
+        try:
+            selected = {os.path.realpath(p) for p in steam.selected_library_paths()}
+            libs = [
+                {"path": lib.path, "label": lib.label, "selected": lib.path in selected,
+                 "count": len(steam.scan_library(lib.path))}
+                for lib in steam.discover_libraries()
+            ]
+            self._libraries_ready.emit(libs)
+            self._scanned.emit(steam.rescan())
+        except Exception:
+            self._scanned.emit(None)
+
+    # --- rendering --------------------------------------------------------------------
+
+    def _render_libraries(self, libs) -> None:
+        while self._lib_box.count():
+            item = self._lib_box.takeAt(0)
+            w = item.widget()
+            if w is not None:
+                w.deleteLater()
+        if not libs:
+            self._lib_hint.setText("No Steam libraries detected. Is Steam installed?")
+            self._lib_hint.show()
+            return
+        self._lib_hint.hide()
+        for lib in libs:
+            label = lib["path"]
+            if lib["label"]:
+                label += f"  [{lib['label']}]"
+            cb = QCheckBox(f"{label}    ·  {lib['count']} games")
+            cb.setChecked(lib["selected"])
+            cb.toggled.connect(lambda checked, p=lib["path"]: self._toggle_library(p, checked))
+            self._lib_box.addWidget(cb)
+
+    def _toggle_library(self, path: str, checked: bool) -> None:
+        selected = {os.path.realpath(p) for p in (load_config().get("steam_libraries") or [])}
+        if checked:
+            selected.add(os.path.realpath(path))
+        else:
+            selected.discard(os.path.realpath(path))
+        update_config(steam_libraries=sorted(selected))
+        self.refresh()
+
+    def _render_games(self, result) -> None:
+        self._busy = False
+        self._rescan_btn.setEnabled(True)
+        if result is None:
+            self._status.setText("scan failed")
+            return
+        self._new_appids = set(result.new_appids)
+        self._populate_games(result.games, self._new_appids)
+        new = len(self._new_appids)
+        suffix = f"  ·  {new} new" if new else ""
+        self._status.setText(
+            f"{len(result.games)} games  ·  {time.strftime('%H:%M:%S')}{suffix}"
+        )
+        self.new_count_changed.emit(new)
+
+    def _populate_games(self, games, new_appids: set[str]) -> None:
+        from ..core import steam
+
+        while self._list.count():
+            item = self._list.takeAt(0)
+            w = item.widget()
+            if w is not None:
+                w.deleteLater()
+
+        if not games:
+            empty = QLabel(
+                "No games to show yet — check a Steam library above to scan it for games."
+            )
+            empty.setObjectName("Muted")
+            empty.setWordWrap(True)
+            self._list.addWidget(empty)
+            self._list.addStretch(1)
+            return
+
+        for g in games:
+            self._list.addWidget(_game_row(
+                g.name,
+                os.path.basename(g.library.rstrip("/")) or g.library,
+                steam.human_size(g.size_bytes),
+                g.appid in new_appids,
+            ))
+        self._list.addStretch(1)
+
+    # --- nav badge integration --------------------------------------------------------
+
+    def showEvent(self, event) -> None:  # noqa: N802 (Qt override)
+        # Viewing the list acknowledges the new games: clear the sidebar badge. The NEW
+        # tags stay on the rows for this session so the user can still spot them.
+        super().showEvent(event)
+        if self._new_appids:
+            from ..core import steam
+
+            threading.Thread(target=steam.acknowledge_new, daemon=True).start()
+            self.new_count_changed.emit(0)

src/rigdoctor/gui/main_window.py

@@ -28,6 +28,7 @@ from .. import __version__
 from ..config import load_config
 from ..core import alerts, elevation, updates
 from .dashboard import Dashboard
+from .games_page import GamesPage
 from .health_page import HealthPage
 from .notifications_page import NotificationsPage
 from .recorder_page import RecorderPage
@@ -36,7 +37,7 @@ from .share_page import SharePage
 from .theme import ACCENT, GOOD, MUTED
 from .worker import SamplerWorker
 
-_NAV_ITEMS = ["Dashboard", "Logs", "Health", "Setup", "Notifications", "Share"]
+_NAV_ITEMS = ["Dashboard", "Logs", "Health", "Games", "Setup", "Notifications", "Share"]
 
 
 class MainWindow(QMainWindow):
@@ -66,6 +67,8 @@ class MainWindow(QMainWindow):
         self.dashboard = Dashboard()
         self.recorder_page = RecorderPage()
         self.health_page = HealthPage()
+        self.games_page = GamesPage()
+        self.games_page.new_count_changed.connect(self._set_games_badge)
         self.setup_page = SetupPage()
         self.notifications_page = NotificationsPage()
         self.notifications_page.changed.connect(self._apply_alert_settings)
@@ -73,9 +76,10 @@ class MainWindow(QMainWindow):
         self._stack.addWidget(self.dashboard)            # 0 Dashboard
         self._stack.addWidget(self.recorder_page)        # 1 Logs
         self._stack.addWidget(self.health_page)          # 2 Health
-        self._stack.addWidget(self.setup_page)           # 3 Setup
+        self._stack.addWidget(self.games_page)           # 3 Games
-        self._stack.addWidget(self.notifications_page)   # 4 Notifications
+        self._stack.addWidget(self.setup_page)           # 4 Setup
-        self._stack.addWidget(self.share_page)           # 5 Share
+        self._stack.addWidget(self.notifications_page)   # 5 Notifications
+        self._stack.addWidget(self.share_page)           # 6 Share
         content_layout.addWidget(self._stack)
 
         layout.addWidget(self._build_sidebar())
@@ -135,6 +139,7 @@ class MainWindow(QMainWindow):
 
         group = QButtonGroup(self)
         group.setExclusive(True)
+        self._nav_buttons: dict[str, QPushButton] = {}
         for i, name in enumerate(_NAV_ITEMS):
             btn = QPushButton(name)
             btn.setObjectName("NavButton")
@@ -144,6 +149,7 @@ class MainWindow(QMainWindow):
             btn.clicked.connect(lambda _checked, idx=i: self._stack.setCurrentIndex(idx))
             group.addButton(btn, i)
             v.addWidget(btn)
+            self._nav_buttons[name] = btn
 
         v.addStretch(1)
         live = QLabel(f'<span style="color:{ACCENT};">●</span> <span style="color:{MUTED};">Live</span>')
@@ -229,6 +235,11 @@ class MainWindow(QMainWindow):
         # collected and used by the relay guest view + the CLI `rigdoctor inventory`.)
         self.health_page._run()
 
+    def _set_games_badge(self, count: int) -> None:
+        btn = self._nav_buttons.get("Games")
+        if btn is not None:
+            btn.setText(f"Games   ● {count}" if count > 0 else "Games")
+
     def _apply_alert_settings(self) -> None:
         cfg = load_config()
         self._alert_monitor.enabled = bool(cfg.get("alerts_enabled", True))

tests/test_config.py

@@ -19,6 +19,16 @@ class ConfigTests(unittest.TestCase):
                 self.assertEqual(loaded["gpu_temp_alert"], 88.0)
                 self.assertEqual(loaded["update_check_minutes"], 5)
 
+    def test_list_value_round_trip(self):
+        with tempfile.TemporaryDirectory() as d:
+            cf = Path(d) / "config.toml"
+            with mock.patch.object(config, "CONFIG_FILE", cf), mock.patch.object(config, "CONFIG_DIR", Path(d)):
+                paths = ["/home/u/.local/share/Steam", "/mnt/games/SteamLibrary"]
+                config.update_config(steam_libraries=paths)
+                self.assertEqual(config.load_config()["steam_libraries"], paths)
+                config.update_config(steam_libraries=[])
+                self.assertEqual(config.load_config()["steam_libraries"], [])
+
     def test_update_config_merges_and_keeps_defaults(self):
         with tempfile.TemporaryDirectory() as d:
             cf = Path(d) / "config.toml"

tests/test_steam.py

@@ -0,0 +1,147 @@
+"""Tests for M6 Steam library & game detection (VDF parse, scan, tool filter, cache diff)."""
+
+import tempfile
+import unittest
+from pathlib import Path
+from unittest import mock
+
+from rigdoctor.core import steam
+
+_GAME_ACF = """"AppState"
+{{
+\t"appid"\t\t"{appid}"
+\t"name"\t\t"{name}"
+\t"installdir"\t\t"{installdir}"
+\t"SizeOnDisk"\t\t"{size}"
+\t"LastUpdated"\t\t"{updated}"
+}}
+"""
+
+_LIBRARYFOLDERS = """"libraryfolders"
+{{
+\t"0"
+\t{{
+\t\t"path"\t\t"{path}"
+\t\t"label"\t\t"Main"
+\t\t"apps"
+\t\t{{
+\t\t\t"570"\t\t"123"
+\t\t}}
+\t}}
+}}
+"""
+
+
+def _make_library(root: Path, games) -> Path:
+    """games: list of (appid, name, installdir, size, updated). Returns the library path."""
+    steamapps = root / "steamapps"
+    steamapps.mkdir(parents=True, exist_ok=True)
+    for appid, name, installdir, size, updated in games:
+        (steamapps / f"appmanifest_{appid}.acf").write_text(
+            _GAME_ACF.format(appid=appid, name=name, installdir=installdir, size=size, updated=updated)
+        )
+    return root
+
+
+class VdfTests(unittest.TestCase):
+    def test_parse_nested_and_pairs(self):
+        data = steam._parse_vdf(_GAME_ACF.format(
+            appid="570", name="Dota 2", installdir="dota 2 beta", size="15", updated="1700"))
+        state = data["AppState"]
+        self.assertEqual(state["appid"], "570")
+        self.assertEqual(state["name"], "Dota 2")
+        self.assertEqual(state["installdir"], "dota 2 beta")
+
+    def test_parse_handles_quotes_in_names(self):
+        acf = _GAME_ACF.format(appid="1", name="Baldur\\'s Gate 3", installdir="bg3", size="1", updated="1")
+        data = steam._parse_vdf(acf)
+        self.assertIn("Baldur", data["AppState"]["name"])
+
+    def test_parse_garbage_returns_empty(self):
+        self.assertEqual(steam._parse_vdf("not vdf at all"), {})
+
+
+class ToolFilterTests(unittest.TestCase):
+    def test_known_tool_appid(self):
+        self.assertTrue(steam.is_tool("228980", "Steamworks Common Redistributables"))
+
+    def test_proton_name_prefix(self):
+        self.assertTrue(steam.is_tool("9999999", "Proton 8.0"))
+        self.assertTrue(steam.is_tool("9999998", "Steam Linux Runtime 3.0 (sniper)"))
+
+    def test_real_game_is_not_a_tool(self):
+        self.assertFalse(steam.is_tool("570", "Dota 2"))
+
+
+class ScanTests(unittest.TestCase):
+    def test_scan_library_filters_tools(self):
+        with tempfile.TemporaryDirectory() as d:
+            lib = _make_library(Path(d), [
+                ("570", "Dota 2", "dota 2 beta", "15000000000", "1700000000"),
+                ("228980", "Steamworks Common Redistributables", "Steamworks Shared", "0", "0"),
+                ("1493710", "Proton Experimental", "Proton - Experimental", "0", "0"),
+            ])
+            games = steam.scan_library(str(lib))
+            names = {g.name for g in games}
+            self.assertEqual(names, {"Dota 2"})
+            self.assertEqual(games[0].size_bytes, 15000000000)
+
+    def test_scan_games_dedupes_and_sorts(self):
+        with tempfile.TemporaryDirectory() as d1, tempfile.TemporaryDirectory() as d2:
+            a = _make_library(Path(d1), [("10", "Zeta", "zeta", "1", "1"), ("20", "Alpha", "alpha", "1", "1")])
+            b = _make_library(Path(d2), [("20", "Alpha", "alpha", "1", "1")])  # dup appid 20
+            games = steam.scan_games([str(a), str(b)])
+            self.assertEqual([g.name for g in games], ["Alpha", "Zeta"])  # sorted, deduped
+
+
+class DiscoverTests(unittest.TestCase):
+    def test_discover_reads_libraryfolders(self):
+        with tempfile.TemporaryDirectory() as d:
+            root = Path(d) / "Steam"
+            (root / "steamapps").mkdir(parents=True)
+            extra = Path(d) / "Extra"
+            (extra / "steamapps").mkdir(parents=True)
+            (root / "steamapps" / "libraryfolders.vdf").write_text(
+                _LIBRARYFOLDERS.format(path=str(extra)))
+            with mock.patch.object(steam, "steam_roots", return_value=[root]):
+                libs = steam.discover_libraries()
+            paths = {lib.path for lib in libs}
+            self.assertIn(str(root.resolve()), paths)   # root itself
+            self.assertIn(str(extra.resolve()), paths)  # the configured extra library
+
+
+class CacheDiffTests(unittest.TestCase):
+    def _rescan(self, lib, games_file, cfg):
+        with mock.patch.object(steam, "GAMES_FILE", games_file):
+            return steam.rescan(cfg=cfg)
+
+    def test_first_scan_has_no_new_then_added_game_is_new(self):
+        with tempfile.TemporaryDirectory() as d:
+            lib = _make_library(Path(d) / "lib", [("10", "Alpha", "alpha", "1", "1")])
+            games_file = Path(d) / "games.json"
+            cfg = {"steam_libraries": [str(lib)]}
+
+            first = self._rescan(lib, games_file, cfg)
+            self.assertEqual(first.new_appids, [])  # first run flags nothing as new
+
+            # Install a second game; it should be flagged new on the next scan.
+            _make_library(lib, [("10", "Alpha", "alpha", "1", "1"), ("20", "Beta", "beta", "1", "1")])
+            second = self._rescan(lib, games_file, cfg)
+            self.assertEqual(second.new_appids, ["20"])
+            self.assertEqual({g.name for g in second.games}, {"Alpha", "Beta"})
+
+    def test_acknowledge_clears_new(self):
+        with tempfile.TemporaryDirectory() as d:
+            lib = _make_library(Path(d) / "lib", [("10", "Alpha", "alpha", "1", "1")])
+            games_file = Path(d) / "games.json"
+            cfg = {"steam_libraries": [str(lib)]}
+            self._rescan(lib, games_file, cfg)
+            _make_library(lib, [("10", "Alpha", "alpha", "1", "1"), ("20", "Beta", "beta", "1", "1")])
+            self._rescan(lib, games_file, cfg)
+            with mock.patch.object(steam, "GAMES_FILE", games_file):
+                steam.acknowledge_new()
+                self.assertEqual(steam.load_cache()["new_appids"], [])
+
+
+if __name__ == "__main__":
+    unittest.main()