refactor patch management and add ownership safeguards

17 files changed, 2113 insertions, 1918 deletions

diff --git a/backend/__init__.py b/backend/__init__.py
new file mode 100644
index 0000000..462b5df
--- /dev/null
+++ b/backend/__init__.py
@@ -0,0 +1 @@
+"""Backend services for Decky Framegen."""
diff --git a/backend/assets.py b/backend/assets.py
new file mode 100644
index 0000000..69f71ba
--- /dev/null
+++ b/backend/assets.py
@@ -0,0 +1,184 @@
+"""Static asset metadata and patch file inventories."""
+
+OPTISCALER_ARCHIVE_ASSET = {
+    "name": "Optiscaler_0.9.4-final.20260718._MM.7z",
+    "sha256": "575cb4df866116093df75af607e37fd70e10f5163e0f23fd5c804142e80ef0ad",
+    "version": "0.9.4-final.20260718",
+}
+
+FSR4_INT8_ASSET = {
+    "name": "amd_fidelityfx_upscaler_dx12.dll",
+    "sha256": "c7720bc16bede334f59a1a32cd22edbcbbb159685ed5240e61350a5fb0bc8a94",
+    "version": "4.0.2c",
+}
+
+FSR4_OFFICIAL_411_ASSET = {
+    "name": "amdxcffx64.dll",
+    "sha256": "a2b136b6affd35a49b141a936be935f7d5ddc8d8f9b8c9afbe62ff9ddb2538a0",
+    "version": "4.1.1-official",
+}
+
+FSR4_VALVE_411_ASSET = {
+    "name": "amdxcffx64_valve_2.3.0.2913.dll",
+    "sha256": "4e7dc37aebea3a90e3d3cc43e24cb2b54176b2535315f20dbe63b3b7cfc56b1e",
+    "version": "4.1.1-valve-2.3.0.2913",
+}
+
+AMDXC64_RDNA2_ASSET = {
+    "name": "amdxc64.dll",
+    "sha256": "a0a0af61d475e30a70966b3459f3793df772faf8f26ae3261d10554ff592cbd5",
+    "version": "8.18.10.0474",
+}
+
+OPTISCALER_PRE10_ASSET = {
+    "name": "OptiScaler_0.10.0-pre1.20260622_135940.dll",
+    "sha256": "b374b19081cc066365d0c6da4808d768e16469b0cbdfc478b6e95999947d5364",
+    "version": "0.10.0-pre1.20260622_135940",
+}
+
+OPTIPATCHER_ASSET = {
+    "name": "OptiPatcher_rolling.asi",
+    "sha256": "88b9e1be3559737cd205fdf5f2c8550cf1923fb1def4c603e5bf03c3e84131b1",
+    "version": "rolling",
+}
+
+FSR4_UPSCALER_FILENAME = "amd_fidelityfx_upscaler_dx12.dll"
+FSR4_DRIVER_OVERRIDE_FILENAME = "amdxcffx64.dll"
+INSTALL_MANIFEST_FILENAME = "install-manifest.json"
+VERSION_FILENAME = "version.txt"
+DEFAULT_FSR4_VARIANT = "rdna23-int8"
+DEFAULT_FRAMEGEN_BACKEND = "auto"
+FRAMEGEN_BACKENDS = {
+    "auto": "OptiScaler automatic selection",
+    "nukems": "Nukem's DLSSG → FSR3",
+}
+
+FSR4_VARIANTS = {
+    "rdna23-int8": {
+        "label": "4.0.2c / RDNA2-3 compatibility",
+        "dir_name": "fsr4-rdna2-3",
+        "sha256": "c7720bc16bede334f59a1a32cd22edbcbbb159685ed5240e61350a5fb0bc8a94",
+        "source_asset_name": FSR4_INT8_ASSET["name"],
+        "source_version": FSR4_INT8_ASSET["version"],
+        "uses_archive_native": False,
+        "extra_files": [],
+    },
+    "rdna4-native": {
+        "label": "4.1.1 SDK / RDNA3 dGPU + RDNA4",
+        "dir_name": "fsr4-rdna4",
+        "sha256": "d0dcccc74a43c44ba435b7a369b456e0970d8a4464e4bd683119b374f2c9fb46",
+        "source_asset_name": OPTISCALER_ARCHIVE_ASSET["name"],
+        "source_version": OPTISCALER_ARCHIVE_ASSET["version"],
+        "uses_archive_native": True,
+        "extra_files": [],
+    },
+    "rdna34-official-411": {
+        "label": "4.1.1 driver override / RDNA3-4",
+        "dir_name": "fsr4-rdna3-4-official-411",
+        "sha256": "d0dcccc74a43c44ba435b7a369b456e0970d8a4464e4bd683119b374f2c9fb46",
+        "source_asset_name": OPTISCALER_ARCHIVE_ASSET["name"],
+        "source_version": OPTISCALER_ARCHIVE_ASSET["version"],
+        "uses_archive_native": True,
+        "extra_files": [
+            {
+                "name": FSR4_DRIVER_OVERRIDE_FILENAME,
+                "sha256": FSR4_OFFICIAL_411_ASSET["sha256"],
+                "source_asset_name": FSR4_OFFICIAL_411_ASSET["name"],
+                "source_version": FSR4_OFFICIAL_411_ASSET["version"],
+            }
+        ],
+        "config_overrides": {},
+    },
+    "rdna2-valve-411-pre10": {
+        "label": "4.1.1 Valve RDNA2 compatibility",
+        "dir_name": "fsr4-rdna2-valve-411-pre10",
+        "sha256": "d0dcccc74a43c44ba435b7a369b456e0970d8a4464e4bd683119b374f2c9fb46",
+        "source_asset_name": OPTISCALER_ARCHIVE_ASSET["name"],
+        "source_version": OPTISCALER_ARCHIVE_ASSET["version"],
+        "uses_archive_native": True,
+        "injector": {
+            "name": "OptiScaler.dll",
+            "sha256": OPTISCALER_PRE10_ASSET["sha256"],
+            "source_asset_name": OPTISCALER_PRE10_ASSET["name"],
+            "source_version": OPTISCALER_PRE10_ASSET["version"],
+        },
+        "extra_files": [
+            {
+                "name": FSR4_DRIVER_OVERRIDE_FILENAME,
+                "sha256": FSR4_VALVE_411_ASSET["sha256"],
+                "source_asset_name": FSR4_VALVE_411_ASSET["name"],
+                "source_version": FSR4_VALVE_411_ASSET["version"],
+            },
+            {
+                "name": "amdxc64.dll",
+                "sha256": AMDXC64_RDNA2_ASSET["sha256"],
+                "source_asset_name": AMDXC64_RDNA2_ASSET["name"],
+                "source_version": AMDXC64_RDNA2_ASSET["version"],
+            },
+        ],
+        "config_overrides": {
+            "FSR.Fsr4ForceModel": "2",
+            "Plugins.LoadCustomAmdxc64OnRdna2": "true",
+        },
+    },
+}
+
+VARIANT_EXTRA_FILENAMES = sorted(
+    {
+        extra_file["name"]
+        for variant in FSR4_VARIANTS.values()
+        for extra_file in variant.get("extra_files", [])
+    }
+)
+
+PROXY_DLL_BACKUPS = [
+    "dxgi.dll",
+    "winmm.dll",
+    "dbghelp.dll",
+    "version.dll",
+    "wininet.dll",
+    "winhttp.dll",
+    "OptiScaler.asi",
+]
+VALID_DLL_NAMES = set(PROXY_DLL_BACKUPS)
+
+INJECTOR_FILENAMES = [
+    *PROXY_DLL_BACKUPS,
+    "nvngx.dll",
+    "_nvngx.dll",
+    "nvngx-wrapper.dll",
+    "dlss-enabler.dll",
+    "OptiScaler.dll",
+]
+
+ORIGINAL_DLL_BACKUPS = [
+    "d3dcompiler_47.dll",
+    "amd_fidelityfx_dx12.dll",
+    "amd_fidelityfx_framegeneration_dx12.dll",
+    FSR4_UPSCALER_FILENAME,
+    FSR4_DRIVER_OVERRIDE_FILENAME,
+    "amdxc64.dll",
+    "amd_fidelityfx_vk.dll",
+]
+
+RESTORABLE_BACKUP_FILES = [
+    *PROXY_DLL_BACKUPS,
+    *ORIGINAL_DLL_BACKUPS,
+]
+
+SUPPORT_FILES = [
+    "libxess.dll",
+    "libxess_dx11.dll",
+    "libxess_fg.dll",
+    "libxell.dll",
+    "amd_fidelityfx_dx12.dll",
+    "amd_fidelityfx_framegeneration_dx12.dll",
+    "amd_fidelityfx_vk.dll",
+    "dlssg_to_fsr3_amd_is_better.dll",
+    "fakenvapi.dll",
+    "fakenvapi.ini",
+]
+
+MARKER_FILENAME = "FRAMEGEN_PATCH"
+MANIFEST_SCHEMA_VERSION = 2
+BACKUP_DIRECTORY_NAME = ".framegen-backups"
diff --git a/backend/bundle.py b/backend/bundle.py
new file mode 100644
index 0000000..a6ef9e4
--- /dev/null
+++ b/backend/bundle.py
@@ -0,0 +1,522 @@
+"""Management of the shared OptiScaler bundle in ``~/fgmod``."""
+
+import os
+import shutil
+import subprocess
+from datetime import datetime, timezone
+from pathlib import Path
+from typing import Callable
+
+from . import config
+from .assets import (
+    DEFAULT_FRAMEGEN_BACKEND,
+    DEFAULT_FSR4_VARIANT,
+    FRAMEGEN_BACKENDS,
+    FSR4_DRIVER_OVERRIDE_FILENAME,
+    FSR4_VARIANTS,
+    FSR4_UPSCALER_FILENAME,
+    INSTALL_MANIFEST_FILENAME,
+    MANIFEST_SCHEMA_VERSION,
+    OPTIPATCHER_ASSET,
+    OPTISCALER_ARCHIVE_ASSET,
+    OPTISCALER_PRE10_ASSET,
+    AMDXC64_RDNA2_ASSET,
+    FSR4_INT8_ASSET,
+    FSR4_OFFICIAL_411_ASSET,
+    FSR4_VALVE_411_ASSET,
+    VERSION_FILENAME,
+)
+from .files import file_sha256, read_json, write_json
+
+
+Logger = Callable[[str], None]
+
+
+class BundleManager:
+    def __init__(self, home: Path, plugin_dir: Path, logger: Logger):
+        self.home = home
+        self.plugin_dir = plugin_dir
+        self.logger = logger
+
+    @property
+    def fgmod_path(self) -> Path:
+        return self.home / "fgmod"
+
+    def _log(self, message: str) -> None:
+        self.logger(f"[Framegen] {message}")
+
+    def _create_renamed_copies(self, source_file: Path, renames_dir: Path) -> bool:
+        try:
+            if not source_file.exists():
+                self._log(f"Source file {source_file} does not exist")
+                return False
+            renames_dir.mkdir(parents=True, exist_ok=True)
+            for filename in ("dxgi.dll", "winmm.dll", "dbghelp.dll", "version.dll", "wininet.dll", "winhttp.dll", "OptiScaler.asi"):
+                shutil.copy2(source_file, renames_dir / filename)
+            return True
+        except OSError as exc:
+            self._log(f"Failed to create renamed copies: {exc}")
+            return False
+
+    def _copy_launcher_scripts(self, assets_dir: Path, extract_path: Path) -> bool:
+        try:
+            scripts = {
+                "fgmod.sh": "fgmod",
+                "fgmod-uninstaller.sh": "fgmod-uninstaller.sh",
+                "update-optiscaler-config.py": "update-optiscaler-config.py",
+            }
+            for source_name, destination_name in scripts.items():
+                source = assets_dir / source_name
+                if not source.exists():
+                    continue
+                destination = extract_path / destination_name
+                shutil.copy2(source, destination)
+                destination.chmod(0o755)
+            return True
+        except OSError as exc:
+            self._log(f"Failed to copy launcher scripts: {exc}")
+            return False
+
+    def _extract_archive(self, archive_path: Path, output_dir: Path) -> None:
+        output_dir.mkdir(parents=True, exist_ok=True)
+        environment = os.environ.copy()
+        environment["LD_LIBRARY_PATH"] = ""
+        result = subprocess.run(
+            ["7z", "x", "-y", "-o" + str(output_dir), str(archive_path)],
+            capture_output=True,
+            text=True,
+            check=False,
+            env=environment,
+        )
+        if result.returncode != 0:
+            raise RuntimeError(result.stderr or result.stdout or f"Failed to extract {archive_path.name}")
+
+    def _verify(self, path: Path, expected_sha256: str, description: str) -> str:
+        actual = file_sha256(path)
+        if actual.lower() != expected_sha256.lower():
+            raise RuntimeError(f"{description} hash mismatch: expected {expected_sha256}, got {actual}")
+        return actual
+
+    def _manifest_path(self) -> Path:
+        return self.fgmod_path / INSTALL_MANIFEST_FILENAME
+
+    def load_manifest(self) -> dict:
+        return read_json(self._manifest_path())
+
+    @staticmethod
+    def normalize_variant(value: str | None) -> str:
+        return value if value in FSR4_VARIANTS else DEFAULT_FSR4_VARIANT
+
+    @staticmethod
+    def normalize_backend(value: str | None) -> str:
+        return value if value in FRAMEGEN_BACKENDS else DEFAULT_FRAMEGEN_BACKEND
+
+    def selected_variant(self, requested: str | None = None) -> str:
+        if requested in FSR4_VARIANTS:
+            return requested
+        installed = self.load_manifest().get("selected_default_variant")
+        return self.normalize_variant(installed)
+
+    def selected_backend(self, requested: str | None = None) -> str:
+        if requested in FRAMEGEN_BACKENDS:
+            return requested
+        manifest_backend = self.load_manifest().get("framegen_backend")
+        if manifest_backend in FRAMEGEN_BACKENDS:
+            return manifest_backend
+        return self.normalize_backend(config.detect_backend(self.fgmod_path / "OptiScaler.ini"))
+
+    def variant_info(self, variant: str | None) -> dict:
+        return FSR4_VARIANTS[self.normalize_variant(variant)]
+
+    def variant_dir(self, variant: str | None) -> Path:
+        return self.fgmod_path / self.variant_info(variant)["dir_name"]
+
+    def variant_path(self, variant: str | None) -> Path:
+        return self.variant_dir(variant) / FSR4_UPSCALER_FILENAME
+
+    def variant_extra_files(self, variant: str | None) -> list[dict]:
+        return list(self.variant_info(variant).get("extra_files") or [])
+
+    def variant_extra_path(self, variant: str | None, filename: str) -> Path:
+        return self.variant_dir(variant) / filename
+
+    def variant_injector_info(self, variant: str | None) -> dict | None:
+        injector = self.variant_info(variant).get("injector")
+        return injector if isinstance(injector, dict) else None
+
+    def variant_injector_path(self, variant: str | None) -> Path | None:
+        injector = self.variant_injector_info(variant)
+        return self.variant_dir(variant) / injector["name"] if injector else None
+
+    def variant_proxy_path(self, variant: str | None, dll_name: str) -> Path | None:
+        if not self.variant_injector_info(variant):
+            return None
+        return self.variant_dir(variant) / "renames" / dll_name
+
+    def variant_config_overrides(self, variant: str | None) -> dict:
+        overrides = self.variant_info(variant).get("config_overrides") or {}
+        return dict(overrides) if isinstance(overrides, dict) else {}
+
+    def fgmod_version(self) -> str | None:
+        manifest = self.load_manifest()
+        optiscaler = manifest.get("optiscaler")
+        if isinstance(optiscaler, dict) and optiscaler.get("version"):
+            return str(optiscaler["version"])
+        try:
+            version = (self.fgmod_path / VERSION_FILENAME).read_text(encoding="utf-8").strip()
+            return version or None
+        except OSError:
+            return None
+
+    def managed_support_candidates(self, filename: str) -> list[Path]:
+        candidates = [self.fgmod_path / filename]
+        if filename == FSR4_UPSCALER_FILENAME:
+            candidates = [self.fgmod_path / filename] + [self.variant_path(variant) for variant in FSR4_VARIANTS]
+        else:
+            for variant in FSR4_VARIANTS:
+                if any(extra.get("name") == filename for extra in self.variant_extra_files(variant)):
+                    candidates.append(self.variant_extra_path(variant, filename))
+        unique: list[Path] = []
+        seen: set[str] = set()
+        for candidate in candidates:
+            if str(candidate) not in seen:
+                unique.append(candidate)
+                seen.add(str(candidate))
+        return unique
+
+    def is_managed_support_file(self, path: Path) -> bool:
+        return path.exists() and any(
+            candidate.is_file() and file_sha256(path) == file_sha256(candidate)
+            for candidate in self.managed_support_candidates(path.name)
+        )
+
+    def _sync_variant_root_extra_files(self, variant: str) -> None:
+        selected = {extra["name"]: extra for extra in self.variant_extra_files(variant)}
+        all_extra_names = {
+            extra["name"]
+            for item in FSR4_VARIANTS.values()
+            for extra in item.get("extra_files", [])
+        }
+        for filename in all_extra_names:
+            root_path = self.fgmod_path / filename
+            if filename not in selected:
+                if root_path.exists():
+                    root_path.unlink()
+                continue
+            source = self.variant_extra_path(variant, filename)
+            if not source.exists():
+                raise FileNotFoundError(f"Prepared FSR4 variant extra file missing: {source}")
+            shutil.copy2(source, root_path)
+
+    def activate_variant(self, variant: str | None) -> str:
+        variant_id = self.normalize_variant(variant)
+        source = self.variant_path(variant_id)
+        if not source.exists():
+            raise FileNotFoundError(f"Prepared FSR4 variant missing: {source}")
+        shutil.copy2(source, self.fgmod_path / FSR4_UPSCALER_FILENAME)
+        self._sync_variant_root_extra_files(variant_id)
+        return variant_id
+
+    def detect_variant(self, directory: Path, upscaler_sha256: str | None) -> str | None:
+        if not upscaler_sha256:
+            return None
+        normalized = upscaler_sha256.lower()
+        for variant_id, variant in FSR4_VARIANTS.items():
+            if str(variant.get("sha256", "")).lower() != normalized:
+                continue
+            if all(
+                (directory / extra["name"]).exists()
+                and file_sha256(directory / extra["name"]).lower() == extra["sha256"].lower()
+                for extra in variant.get("extra_files", [])
+            ):
+                return variant_id
+        return None
+
+    def extract_static_optiscaler(
+        self,
+        selected_default_variant: str = DEFAULT_FSR4_VARIANT,
+        framegen_backend: str = DEFAULT_FRAMEGEN_BACKEND,
+    ) -> dict:
+        """Prepare the shared bundle; replacement remains intentionally non-atomic for compatibility."""
+        try:
+            selected_default_variant = self.normalize_variant(selected_default_variant)
+            framegen_backend = self.normalize_backend(framegen_backend)
+            bin_path = self.plugin_dir / "bin"
+            assets_dir = self.plugin_dir / "assets"
+            if not bin_path.exists():
+                return {"status": "error", "message": f"Bin directory not found: {bin_path}"}
+
+            asset_sources = {
+                "archive": (bin_path / OPTISCALER_ARCHIVE_ASSET["name"], OPTISCALER_ARCHIVE_ASSET),
+                "int8": (bin_path / FSR4_INT8_ASSET["name"], FSR4_INT8_ASSET),
+                "official": (bin_path / FSR4_OFFICIAL_411_ASSET["name"], FSR4_OFFICIAL_411_ASSET),
+                "valve": (bin_path / FSR4_VALVE_411_ASSET["name"], FSR4_VALVE_411_ASSET),
+                "amdxc64": (bin_path / AMDXC64_RDNA2_ASSET["name"], AMDXC64_RDNA2_ASSET),
+                "pre10": (bin_path / OPTISCALER_PRE10_ASSET["name"], OPTISCALER_PRE10_ASSET),
+                "optipatcher": (bin_path / OPTIPATCHER_ASSET["name"], OPTIPATCHER_ASSET),
+            }
+            for path, asset in asset_sources.values():
+                if not path.exists():
+                    return {"status": "error", "message": f"Required bundled asset missing: {asset['name']}"}
+                self._verify(path, asset["sha256"], asset["name"])
+
+            if self.fgmod_path.exists():
+                shutil.rmtree(self.fgmod_path)
+            self.fgmod_path.mkdir(parents=True, exist_ok=True)
+            self._extract_archive(asset_sources["archive"][0], self.fgmod_path)
+
+            source = self.fgmod_path / "OptiScaler.dll"
+            if not self._create_renamed_copies(source, self.fgmod_path / "renames"):
+                return {"status": "error", "message": "Failed to prepare renamed OptiScaler proxies."}
+            if not self._copy_launcher_scripts(assets_dir, self.fgmod_path):
+                return {"status": "error", "message": "Failed to copy launcher scripts."}
+
+            plugins_dir = self.fgmod_path / "plugins"
+            plugins_dir.mkdir(parents=True, exist_ok=True)
+            optipatcher_dst = plugins_dir / "OptiPatcher.asi"
+            shutil.copy2(asset_sources["optipatcher"][0], optipatcher_dst)
+            optipatcher_sha256 = self._verify(optipatcher_dst, OPTIPATCHER_ASSET["sha256"], "Prepared OptiPatcher plugin")
+
+            ini_file = self.fgmod_path / "OptiScaler.ini"
+            config.configure(ini_file, framegen_backend, logger=self.logger)
+
+            native_root = self.fgmod_path / FSR4_UPSCALER_FILENAME
+            native_sha256 = self._verify(native_root, FSR4_VARIANTS["rdna4-native"]["sha256"], "Archive-native FSR4 upscaler")
+            for variant_id in ("rdna4-native", "rdna34-official-411", "rdna2-valve-411-pre10"):
+                variant_dir = self.variant_dir(variant_id)
+                variant_dir.mkdir(parents=True, exist_ok=True)
+                prepared = variant_dir / FSR4_UPSCALER_FILENAME
+                shutil.copy2(native_root, prepared)
+                self._verify(prepared, FSR4_VARIANTS[variant_id]["sha256"], f"Prepared {variant_id} FSR4 upscaler")
+
+            official_dir = self.variant_dir("rdna34-official-411")
+            shutil.copy2(asset_sources["official"][0], official_dir / FSR4_DRIVER_OVERRIDE_FILENAME)
+            self._verify(official_dir / FSR4_DRIVER_OVERRIDE_FILENAME, FSR4_OFFICIAL_411_ASSET["sha256"], "Prepared official driver override")
+
+            valve_dir = self.variant_dir("rdna2-valve-411-pre10")
+            shutil.copy2(asset_sources["valve"][0], valve_dir / FSR4_DRIVER_OVERRIDE_FILENAME)
+            shutil.copy2(asset_sources["amdxc64"][0], valve_dir / "amdxc64.dll")
+            shutil.copy2(asset_sources["pre10"][0], valve_dir / "OptiScaler.dll")
+            self._verify(valve_dir / FSR4_DRIVER_OVERRIDE_FILENAME, FSR4_VALVE_411_ASSET["sha256"], "Prepared Valve driver override")
+            self._verify(valve_dir / "amdxc64.dll", AMDXC64_RDNA2_ASSET["sha256"], "Prepared RDNA2 driver override")
+            self._verify(valve_dir / "OptiScaler.dll", OPTISCALER_PRE10_ASSET["sha256"], "Prepared pre10 OptiScaler injector")
+            if not self._create_renamed_copies(valve_dir / "OptiScaler.dll", valve_dir / "renames"):
+                return {"status": "error", "message": "Failed to prepare renamed pre10 OptiScaler proxies."}
+
+            int8_dir = self.variant_dir("rdna23-int8")
+            int8_dir.mkdir(parents=True, exist_ok=True)
+            shutil.copy2(asset_sources["int8"][0], int8_dir / FSR4_UPSCALER_FILENAME)
+            self._verify(int8_dir / FSR4_UPSCALER_FILENAME, FSR4_INT8_ASSET["sha256"], "Prepared RDNA2-3 FSR4 upscaler")
+
+            selected_default_variant = self.activate_variant(selected_default_variant)
+            active_sha256 = file_sha256(self.fgmod_path / FSR4_UPSCALER_FILENAME)
+            (self.fgmod_path / VERSION_FILENAME).write_text(OPTISCALER_ARCHIVE_ASSET["version"], encoding="utf-8")
+            manifest = self._build_manifest(
+                selected_default_variant,
+                framegen_backend,
+                native_sha256,
+                optipatcher_sha256,
+                active_sha256,
+            )
+            write_json(self._manifest_path(), manifest)
+            return {
+                "status": "success",
+                "message": f"Successfully extracted OptiScaler {OPTISCALER_ARCHIVE_ASSET['version']} to ~/fgmod",
+                "version": OPTISCALER_ARCHIVE_ASSET["version"],
+                "selected_default_variant": selected_default_variant,
+                "selected_default_variant_label": FSR4_VARIANTS[selected_default_variant]["label"],
+                "framegen_backend": framegen_backend,
+                "framegen_backend_label": FRAMEGEN_BACKENDS[framegen_backend],
+            }
+        except Exception as exc:
+            self._log(f"Extract failed: {exc}")
+            return {"status": "error", "message": f"Extract failed: {exc}"}
+
+    def _build_manifest(
+        self,
+        selected_variant: str,
+        framegen_backend: str,
+        native_sha256: str,
+        optipatcher_sha256: str,
+        active_sha256: str,
+    ) -> dict:
+        variants = {}
+        for variant_id, variant in FSR4_VARIANTS.items():
+            injector = variant.get("injector")
+            injector_manifest = None
+            if isinstance(injector, dict):
+                injector_manifest = {
+                    key: injector[key]
+                    for key in ("name", "sha256", "source_asset_name", "source_version")
+                }
+                injector_manifest["path"] = str(Path(variant["dir_name"]) / injector["name"])
+            variants[variant_id] = {
+                "label": variant["label"],
+                "dir_name": variant["dir_name"],
+                "path": str(Path(variant["dir_name"]) / FSR4_UPSCALER_FILENAME),
+                "sha256": variant["sha256"],
+                "source_asset_name": variant["source_asset_name"],
+                "source_version": variant["source_version"],
+                "uses_archive_native": bool(variant["uses_archive_native"]),
+                "injector": injector_manifest,
+                "config_overrides": dict(variant.get("config_overrides") or {}),
+                "extra_files": [
+                    {
+                        **{key: extra[key] for key in ("name", "sha256", "source_asset_name", "source_version")},
+                        "path": str(Path(variant["dir_name"]) / extra["name"]),
+                    }
+                    for extra in variant.get("extra_files", [])
+                ],
+            }
+        return {
+            "schema_version": MANIFEST_SCHEMA_VERSION,
+            "installed_at": datetime.now(timezone.utc).isoformat(),
+            "optiscaler": {
+                "asset_name": OPTISCALER_ARCHIVE_ASSET["name"],
+                "version": OPTISCALER_ARCHIVE_ASSET["version"],
+                "sha256": OPTISCALER_ARCHIVE_ASSET["sha256"],
+                "native_upscaler_sha256": native_sha256,
+            },
+            "optipatcher": {
+                "asset_name": OPTIPATCHER_ASSET["name"],
+                "version": OPTIPATCHER_ASSET["version"],
+                "sha256": optipatcher_sha256,
+                "target_path": "plugins/OptiPatcher.asi",
+            },
+            "fsr4_variants": variants,
+            "selected_default_variant": selected_variant,
+            "framegen_backend": framegen_backend,
+            "framegen_backend_label": FRAMEGEN_BACKENDS[framegen_backend],
+            "active_root_upscaler": {
+                "path": FSR4_UPSCALER_FILENAME,
+                "sha256": active_sha256,
+                "variant": selected_variant,
+            },
+        }
+
+    def run_install(self, selected_variant: str, framegen_backend: str) -> dict:
+        selected_variant = self.normalize_variant(selected_variant)
+        framegen_backend = self.normalize_backend(framegen_backend)
+        result = self.extract_static_optiscaler(selected_variant, framegen_backend)
+        if result["status"] != "success":
+            return {"status": "error", "message": f"OptiScaler extraction failed: {result.get('message', 'Unknown error')}"}
+        return {
+            "status": "success",
+            "output": f"Successfully installed OptiScaler {result.get('version', OPTISCALER_ARCHIVE_ASSET['version'])} with {result.get('selected_default_variant_label', FSR4_VARIANTS[selected_variant]['label'])}.",
+            "version": result.get("version", OPTISCALER_ARCHIVE_ASSET["version"]),
+            "selected_default_variant": result.get("selected_default_variant", selected_variant),
+            "selected_default_variant_label": result.get("selected_default_variant_label", FSR4_VARIANTS[selected_variant]["label"]),
+            "framegen_backend": result.get("framegen_backend", framegen_backend),
+            "framegen_backend_label": result.get("framegen_backend_label", FRAMEGEN_BACKENDS[framegen_backend]),
+        }
+
+    def uninstall(self) -> dict:
+        try:
+            if not self.fgmod_path.exists():
+                return {"status": "success", "output": "No fgmod directory found to remove"}
+            shutil.rmtree(self.fgmod_path)
+            return {"status": "success", "output": "Successfully removed fgmod directory"}
+        except OSError as exc:
+            self._log(f"Uninstall error: {exc}")
+            return {"status": "error", "message": f"Uninstall failed: {exc}", "output": str(exc)}
+
+    def set_default_variant(self, selected_variant: str) -> dict:
+        try:
+            if not self.fgmod_path.exists():
+                return {"status": "error", "message": "OptiScaler bundle not installed. Run Install first."}
+            manifest = self.load_manifest()
+            if not manifest:
+                return {"status": "error", "message": "Install manifest missing. Reinstall OptiScaler."}
+            selected_variant = self.activate_variant(selected_variant)
+            active_sha256 = file_sha256(self.fgmod_path / FSR4_UPSCALER_FILENAME)
+            manifest["selected_default_variant"] = selected_variant
+            manifest["active_root_upscaler"] = {
+                "path": FSR4_UPSCALER_FILENAME,
+                "sha256": active_sha256,
+                "variant": selected_variant,
+            }
+            manifest["updated_at"] = datetime.now(timezone.utc).isoformat()
+            write_json(self._manifest_path(), manifest)
+            return {
+                "status": "success",
+                "output": f"Default FSR4 runtime switched to {FSR4_VARIANTS[selected_variant]['label']}.",
+                "version": self.fgmod_version(),
+                "selected_default_variant": selected_variant,
+                "selected_default_variant_label": FSR4_VARIANTS[selected_variant]["label"],
+            }
+        except Exception as exc:
+            self._log(f"Failed to switch default FSR4 runtime: {exc}")
+            return {"status": "error", "message": f"Failed to switch default FSR4 runtime: {exc}"}
+
+    def set_framegen_backend(self, framegen_backend: str) -> dict:
+        try:
+            if not self.fgmod_path.exists():
+                return {"status": "error", "message": "OptiScaler bundle not installed. Run Install first."}
+            backend = self.normalize_backend(framegen_backend)
+            manifest = self.load_manifest()
+            if not manifest:
+                return {"status": "error", "message": "Install manifest missing. Reinstall OptiScaler."}
+            ini_file = self.fgmod_path / "OptiScaler.ini"
+            if not config.configure(ini_file, backend, logger=self.logger):
+                return {"status": "error", "message": "Could not update the shared OptiScaler.ini."}
+            manifest["framegen_backend"] = backend
+            manifest["framegen_backend_label"] = FRAMEGEN_BACKENDS[backend]
+            manifest["updated_at"] = datetime.now(timezone.utc).isoformat()
+            write_json(self._manifest_path(), manifest)
+            return {
+                "status": "success",
+                "framegen_backend": backend,
+                "framegen_backend_label": FRAMEGEN_BACKENDS[backend],
+                "output": f"Frame generation backend set to {FRAMEGEN_BACKENDS[backend]}.",
+            }
+        except Exception as exc:
+            self._log(f"Failed to set frame generation backend: {exc}")
+            return {"status": "error", "message": f"Failed to set frame generation backend: {exc}"}
+
+    def check(self) -> dict:
+        required_files = [
+            "OptiScaler.dll",
+            "OptiScaler.ini",
+            "dlssg_to_fsr3_amd_is_better.dll",
+            "fakenvapi.dll",
+            "fakenvapi.ini",
+            "amd_fidelityfx_dx12.dll",
+            "amd_fidelityfx_framegeneration_dx12.dll",
+            FSR4_UPSCALER_FILENAME,
+            "amd_fidelityfx_vk.dll",
+            "libxess.dll",
+            "libxess_dx11.dll",
+            "libxess_fg.dll",
+            "libxell.dll",
+            "fgmod",
+            "fgmod-uninstaller.sh",
+            "update-optiscaler-config.py",
+            INSTALL_MANIFEST_FILENAME,
+        ]
+        if not self.fgmod_path.exists() or any(not (self.fgmod_path / filename).exists() for filename in required_files):
+            return {"exists": False}
+        plugins_dir = self.fgmod_path / "plugins"
+        if not (plugins_dir / "OptiPatcher.asi").exists():
+            return {"exists": False}
+        for variant_id, variant in FSR4_VARIANTS.items():
+            variant_dir = self.variant_dir(variant_id)
+            if not (variant_dir / FSR4_UPSCALER_FILENAME).exists():
+                return {"exists": False}
+            injector = variant.get("injector")
+            if isinstance(injector, dict) and not (variant_dir / injector.get("name", "OptiScaler.dll")).exists():
+                return {"exists": False}
+            for extra in variant.get("extra_files", []):
+                if not (variant_dir / extra["name"]).exists():
+                    return {"exists": False}
+        manifest = self.load_manifest()
+        variant = self.selected_variant()
+        backend = self.selected_backend()
+        return {
+            "exists": True,
+            "version": self.fgmod_version(),
+            "selected_fsr4_variant": variant,
+            "selected_fsr4_variant_label": FSR4_VARIANTS[variant]["label"],
+            "framegen_backend": backend,
+            "framegen_backend_label": FRAMEGEN_BACKENDS[backend],
+            "install_manifest_present": bool(manifest),
+        }
diff --git a/backend/config.py b/backend/config.py
new file mode 100644
index 0000000..87476cc
--- /dev/null
+++ b/backend/config.py
@@ -0,0 +1,175 @@
+"""OptiScaler configuration migration and default handling."""
+
+import re
+from pathlib import Path
+from typing import Callable
+
+
+Logger = Callable[[str], None]
+
+
+def _split_override_key(raw_key: str) -> tuple[str | None, str]:
+    key = str(raw_key).strip()
+    if "." in key:
+        section, section_key = key.split(".", 1)
+        section = section.strip()
+        section_key = section_key.strip()
+        if section and section_key:
+            return section, section_key
+    return None, key
+
+
+def apply_overrides(ini_file: Path, overrides: dict, logger: Logger | None = None) -> bool:
+    """Upsert INI keys without disturbing unrelated game configuration."""
+    if not overrides:
+        return True
+    try:
+        content = ini_file.read_text(encoding="utf-8", errors="replace")
+        newline = "\r\n" if "\r\n" in content else "\n"
+        lines = content.splitlines(keepends=True)
+        section_pattern = re.compile(r"^\s*\[(?P<section>[^\]]+)\]\s*$")
+
+        def ensure_trailing_newline() -> None:
+            if lines and not lines[-1].endswith(("\n", "\r")):
+                lines[-1] += newline
+
+        def upsert(section: str | None, key: str, value: str) -> None:
+            replacement = f"{key}={value}"
+            key_pattern = re.compile(rf"^(\s*{re.escape(key)}\s*)=.*$")
+
+            if section is None:
+                for index, line in enumerate(lines):
+                    if key_pattern.match(line):
+                        ending = "\r\n" if line.endswith("\r\n") else ("\n" if line.endswith("\n") else newline)
+                        lines[index] = f"{replacement}{ending}"
+                        return
+                ensure_trailing_newline()
+                lines.append(f"{replacement}{newline}")
+                return
+
+            in_section = False
+            insert_at = None
+            for index, line in enumerate(lines):
+                match = section_pattern.match(line.strip())
+                if match:
+                    if in_section:
+                        insert_at = index
+                        break
+                    if match.group("section") == section:
+                        in_section = True
+                        continue
+                if in_section and key_pattern.match(line):
+                    ending = "\r\n" if line.endswith("\r\n") else ("\n" if line.endswith("\n") else newline)
+                    lines[index] = f"{replacement}{ending}"
+                    return
+
+            if in_section:
+                if insert_at is None:
+                    ensure_trailing_newline()
+                    insert_at = len(lines)
+                lines.insert(insert_at, f"{replacement}{newline}")
+                return
+
+            ensure_trailing_newline()
+            if lines and lines[-1].strip():
+                lines.append(newline)
+            lines.extend((f"[{section}]{newline}", f"{replacement}{newline}"))
+
+        for raw_key, raw_value in overrides.items():
+            section, key = _split_override_key(str(raw_key))
+            if key:
+                upsert(section, key, str(raw_value).strip())
+        ini_file.write_text("".join(lines), encoding="utf-8")
+        return True
+    except Exception as exc:
+        if logger:
+            logger(f"Failed to apply OptiScaler.ini overrides to {ini_file}: {exc}")
+        return False
+
+
+def migrate(ini_file: Path, logger: Logger | None = None) -> bool:
+    """Migrate the pre-0.9 ``FGType`` setting to split input/output keys."""
+    try:
+        if not ini_file.exists():
+            return False
+        content = ini_file.read_text(encoding="utf-8", errors="replace")
+        match = re.search(r"^FGType\s*=\s*(\S+)", content, re.MULTILINE)
+        if not match:
+            return True
+
+        value = match.group(1)
+        if re.search(r"^FGInput\s*=", content, re.MULTILINE):
+            updated = re.sub(r"^FGType\s*=\s*\S+\n?", "", content, flags=re.MULTILINE)
+            message = f"Removed stale FGType from {ini_file}"
+        else:
+            updated = re.sub(
+                r"^FGType\s*=\s*\S+",
+                f"FGInput={value}\nFGOutput={value}",
+                content,
+                flags=re.MULTILINE,
+            )
+            message = f"Migrated FGType={value} in {ini_file}"
+        if updated != content:
+            ini_file.write_text(updated, encoding="utf-8")
+            if logger:
+                logger(message)
+        return True
+    except Exception as exc:
+        if logger:
+            logger(f"Failed to migrate OptiScaler.ini: {exc}")
+        return False
+
+
+def disable_hq_font_auto(ini_file: Path, logger: Logger | None = None) -> bool:
+    """Avoid the HQ font auto mode, which is unreliable under Proton."""
+    try:
+        if not ini_file.exists():
+            return False
+        content = ini_file.read_text(encoding="utf-8", errors="replace")
+        updated = re.sub(r"UseHQFont\s*=\s*auto", "UseHQFont=false", content)
+        if updated != content:
+            ini_file.write_text(updated, encoding="utf-8")
+        return True
+    except Exception as exc:
+        if logger:
+            logger(f"Failed to update HQ font setting in {ini_file}: {exc}")
+        return False
+
+
+def configure(
+    ini_file: Path,
+    framegen_backend: str,
+    variant_overrides: dict | None = None,
+    logger: Logger | None = None,
+) -> bool:
+    """Apply safe defaults and the selected frame-generation backend."""
+    if not ini_file.exists():
+        return False
+    backend = framegen_backend if framegen_backend in {"auto", "nukems"} else "auto"
+    overrides = {
+        "FGInput": backend,
+        "FGOutput": backend,
+        "Fsr4Update": "true",
+        "LoadAsiPlugins": "true",
+    }
+    if variant_overrides:
+        overrides.update(variant_overrides)
+    migrated = migrate(ini_file, logger)
+    hq_updated = disable_hq_font_auto(ini_file, logger)
+    configured = apply_overrides(ini_file, overrides, logger)
+    return migrated and hq_updated and configured
+
+
+def detect_backend(ini_file: Path) -> str:
+    """Return the configured backend when both FG keys agree."""
+    try:
+        content = ini_file.read_text(encoding="utf-8", errors="replace")
+    except OSError:
+        return "auto"
+    values = [
+        match.group(1).strip().lower()
+        for match in re.finditer(r"^FG(?:Input|Output)\s*=\s*(\S+)", content, re.MULTILINE)
+    ]
+    if values and all(value == "nukems" for value in values):
+        return "nukems"
+    return "auto"
diff --git a/backend/files.py b/backend/files.py
new file mode 100644
index 0000000..c5ec839
--- /dev/null
+++ b/backend/files.py
@@ -0,0 +1,36 @@
+"""Small filesystem helpers shared by backend services."""
+
+import filecmp
+import hashlib
+import json
+from pathlib import Path
+
+
+def file_sha256(path: Path) -> str:
+    digest = hashlib.sha256()
+    with path.open("rb") as stream:
+        for chunk in iter(lambda: stream.read(1024 * 1024), b""):
+            digest.update(chunk)
+    return digest.hexdigest()
+
+
+def files_match(file_a: Path, file_b: Path) -> bool:
+    try:
+        return file_a.is_file() and file_b.is_file() and filecmp.cmp(file_a, file_b, shallow=False)
+    except OSError:
+        return False
+
+
+def read_json(path: Path) -> dict:
+    try:
+        with path.open("r", encoding="utf-8") as stream:
+            payload = json.load(stream)
+        return payload if isinstance(payload, dict) else {}
+    except (OSError, ValueError, TypeError):
+        return {}
+
+
+def write_json(path: Path, payload: dict) -> None:
+    path.parent.mkdir(parents=True, exist_ok=True)
+    with path.open("w", encoding="utf-8") as stream:
+        json.dump(payload, stream, indent=2)
diff --git a/backend/patcher.py b/backend/patcher.py
new file mode 100644
index 0000000..59d08f1
--- /dev/null
+++ b/backend/patcher.py
@@ -0,0 +1,685 @@
+"""Patch ownership, safe cleanup, and Steam-game operations."""
+
+import os
+import shutil
+from datetime import datetime, timezone
+from pathlib import Path
+from typing import Callable
+
+from . import config
+from .assets import (
+    BACKUP_DIRECTORY_NAME,
+    FRAMEGEN_BACKENDS,
+    FSR4_UPSCALER_FILENAME,
+    INJECTOR_FILENAMES,
+    MARKER_FILENAME,
+    MANIFEST_SCHEMA_VERSION,
+    RESTORABLE_BACKUP_FILES,
+    SUPPORT_FILES,
+    VALID_DLL_NAMES,
+    VARIANT_EXTRA_FILENAMES,
+)
+from .bundle import BundleManager
+from .files import file_sha256, files_match, read_json, write_json
+from .steam import SteamLibrary
+
+
+Logger = Callable[[str], None]
+
+
+class PatchManager:
+    def __init__(self, home: Path, bundle: BundleManager, steam: SteamLibrary, logger: Logger):
+        self.home = home
+        self.bundle = bundle
+        self.steam = steam
+        self.logger = logger
+
+    def _log(self, message: str) -> None:
+        self.logger(f"[Framegen] {message}")
+
+    @staticmethod
+    def _relative_path(root: Path, path: Path) -> str:
+        return path.resolve().relative_to(root.resolve()).as_posix()
+
+    def _safe_path(self, root: Path, value: str | Path) -> Path:
+        candidate = Path(value)
+        if candidate.is_absolute():
+            resolved = candidate.resolve()
+        else:
+            resolved = (root / candidate).resolve()
+        try:
+            resolved.relative_to(root.resolve())
+        except ValueError as exc:
+            raise ValueError(f"Path escapes patch directory: {value}") from exc
+        return resolved
+
+    def _read_marker(self, marker_path: Path) -> dict:
+        return read_json(marker_path)
+
+    def _find_marker(self, install_root: Path, appid: str | None = None) -> Path | None:
+        if not install_root.exists():
+            return None
+        try:
+            markers = sorted(path for path in install_root.rglob(MARKER_FILENAME) if path.is_file())
+        except OSError:
+            return None
+        for marker in markers:
+            metadata = self._read_marker(marker)
+            if appid is None or str(metadata.get("appid")) == str(appid):
+                return marker
+        return None
+
+    def _marker_target(self, marker_path: Path, metadata: dict) -> Path:
+        target_value = metadata.get("target_relative") or metadata.get("target_dir") or str(marker_path.parent)
+        target = self._safe_path(marker_path.parent, target_value)
+        if not target.is_dir():
+            raise FileNotFoundError(f"Patch target directory does not exist: {target}")
+        return target
+
+    def _bundle_source_for_proxy(self, variant: str, dll_name: str) -> Path:
+        candidates = [
+            self.bundle.variant_proxy_path(variant, dll_name),
+            self.bundle.variant_injector_path(variant),
+            self.bundle.fgmod_path / "renames" / dll_name,
+            self.bundle.fgmod_path / "OptiScaler.dll",
+        ]
+        for candidate in candidates:
+            if candidate and candidate.exists():
+                return candidate
+        raise FileNotFoundError(f"No injector source found for {dll_name}")
+
+    def _copy_plan(self, target_dir: Path, variant: str) -> list[tuple[str, Path]]:
+        plan: list[tuple[str, Path]] = []
+        # The proxy is the only file selected by the user; all other files are bundle-owned.
+        plan.append(("__proxy__", self._bundle_source_for_proxy(variant, "dxgi.dll")))
+        for filename in SUPPORT_FILES:
+            source = self.bundle.fgmod_path / filename
+            if source.is_file():
+                plan.append((filename, source))
+        upscaler = self.bundle.variant_path(variant)
+        if upscaler.is_file():
+            plan.append((FSR4_UPSCALER_FILENAME, upscaler))
+        for extra in self.bundle.variant_extra_files(variant):
+            source = self.bundle.variant_extra_path(variant, extra["name"])
+            if source.is_file():
+                plan.append((extra["name"], source))
+
+        for source_root, relative_root in (
+            (self.bundle.fgmod_path / "plugins", Path("plugins")),
+            (self.bundle.fgmod_path / "D3D12_Optiscaler", Path("D3D12_Optiscaler")),
+        ):
+            if not source_root.is_dir():
+                continue
+            for source in sorted(path for path in source_root.rglob("*") if path.is_file()):
+                plan.append(((relative_root / source.relative_to(source_root)).as_posix(), source))
+        return plan
+
+    def _backup_destination(self, target_dir: Path, relative: str, source: Path, force: bool = False) -> str | None:
+        destination = self._safe_path(target_dir, relative)
+        if not destination.exists():
+            return None
+        if destination.is_dir():
+            raise IsADirectoryError(f"Patch destination is a directory: {destination}")
+        if not force and files_match(destination, source):
+            return None
+
+        if relative in RESTORABLE_BACKUP_FILES:
+            legacy_backup = destination.with_name(destination.name + ".b")
+            if not legacy_backup.exists():
+                shutil.copy2(destination, legacy_backup)
+            elif not files_match(legacy_backup, destination):
+                raise RuntimeError(f"Refusing to overwrite an existing backup: {legacy_backup}")
+            return self._relative_path(target_dir, legacy_backup)
+
+        backup = target_dir / BACKUP_DIRECTORY_NAME / relative
+        backup.parent.mkdir(parents=True, exist_ok=True)
+        if backup.exists():
+            if not files_match(backup, destination):
+                raise RuntimeError(f"Refusing to overwrite an existing backup: {backup}")
+        else:
+            shutil.copy2(destination, backup)
+        return self._relative_path(target_dir, backup)
+
+    def _cleanup_empty_directories(self, target_dir: Path, managed_files: list[str]) -> None:
+        directories = sorted(
+            {self._safe_path(target_dir, path).parent for path in managed_files},
+            key=lambda path: len(path.parts),
+            reverse=True,
+        )
+        for directory in directories:
+            if directory == target_dir:
+                continue
+            try:
+                directory.rmdir()
+            except OSError:
+                pass
+        backup_dir = target_dir / BACKUP_DIRECTORY_NAME
+        try:
+            backup_dir.rmdir()
+        except OSError:
+            pass
+
+    def _rollback(
+        self,
+        target_dir: Path,
+        managed: list[dict],
+        backups: list[dict],
+    ) -> None:
+        for entry in reversed(managed):
+            try:
+                path = self._safe_path(target_dir, entry["path"])
+                backup = next((item["backup"] for item in backups if item["path"] == entry["path"]), None)
+                if backup:
+                    backup_path = self._safe_path(target_dir, backup)
+                    if backup_path.exists():
+                        if path.exists():
+                            path.unlink()
+                        shutil.move(backup_path, path)
+                elif path.exists() and entry.get("sha256") == file_sha256(path):
+                    path.unlink()
+            except (OSError, ValueError):
+                continue
+        self._cleanup_empty_directories(target_dir, [entry["path"] for entry in managed])
+
+    def _patch_directory(
+        self,
+        target_dir: Path,
+        dll_name: str,
+        variant: str,
+        framegen_backend: str,
+        *,
+        appid: str,
+        game_name: str,
+        original_launch_options: str,
+        previous_variant: str | None = None,
+    ) -> dict:
+        if dll_name not in VALID_DLL_NAMES:
+            return {"status": "error", "message": f"Invalid proxy DLL name: {dll_name}"}
+        if not self.bundle.fgmod_path.exists() or not (self.bundle.fgmod_path / "OptiScaler.dll").exists():
+            return {"status": "error", "message": "OptiScaler bundle not installed. Run Install first."}
+
+        variant = self.bundle.selected_variant(variant)
+        framegen_backend = self.bundle.selected_backend(framegen_backend)
+        previous_marker = target_dir / MARKER_FILENAME
+        if previous_marker.exists():
+            return {"status": "error", "message": f"Patch marker already exists in {target_dir}; clean it up before patching."}
+        variant_overrides = self.bundle.variant_config_overrides(variant)
+        if previous_variant == "rdna2-valve-411-pre10" and variant != previous_variant:
+            variant_overrides.setdefault("FSR.Fsr4ForceModel", "auto")
+            variant_overrides.setdefault("Plugins.LoadCustomAmdxc64OnRdna2", "false")
+
+        managed: list[dict] = []
+        backups: list[dict] = []
+        try:
+            plan = self._copy_plan(target_dir, variant)
+            proxy_source = self._bundle_source_for_proxy(variant, dll_name)
+            plan[0] = (dll_name, proxy_source)
+            config_path = target_dir / "OptiScaler.ini"
+            if config_path.exists():
+                plan.append(("OptiScaler.ini", config_path))
+            elif (self.bundle.fgmod_path / "OptiScaler.ini").exists():
+                plan.append(("OptiScaler.ini", self.bundle.fgmod_path / "OptiScaler.ini"))
+
+            for relative, source in plan:
+                destination = self._safe_path(target_dir, relative)
+                if not source.is_file():
+                    continue
+                backup = self._backup_destination(
+                    target_dir,
+                    relative,
+                    source,
+                    # Preserve every pre-existing destination. Identical bytes do
+                    # not prove that a file belongs to this plugin.
+                    force=destination.exists(),
+                )
+                if backup:
+                    backups.append({
+                        "path": relative,
+                        "backup": backup,
+                        "sha256": file_sha256(self._safe_path(target_dir, backup)),
+                    })
+                destination.parent.mkdir(parents=True, exist_ok=True)
+                if destination.resolve() != source.resolve():
+                    shutil.copy2(source, destination)
+                managed.append({
+                    "path": relative,
+                    "sha256": file_sha256(destination),
+                    "source_sha256": file_sha256(source),
+                })
+
+            if config_path.exists() and not config.configure(
+                config_path,
+                framegen_backend,
+                variant_overrides=variant_overrides,
+                logger=self.logger,
+            ):
+                raise RuntimeError("Could not update OptiScaler.ini")
+            config_entry = next((entry for entry in managed if entry["path"] == "OptiScaler.ini"), None)
+            if config_entry:
+                config_entry["sha256"] = file_sha256(config_path)
+
+            payload = {
+                "schema_version": MANIFEST_SCHEMA_VERSION,
+                "appid": str(appid),
+                "game_name": game_name,
+                "dll_name": dll_name,
+                "target_dir": str(target_dir),
+                "target_relative": ".",
+                "original_launch_options": original_launch_options,
+                "backed_up_files": [item["path"] for item in backups],
+                "backups": backups,
+                "managed_files": managed,
+                "managed_directories": sorted({str(Path(item["path"]).parent) for item in managed if Path(item["path"]).parent != Path(".")}),
+                "optiscaler_version": self.bundle.fgmod_version(),
+                "fsr4_variant": variant,
+                "fsr4_variant_label": self.bundle.variant_info(variant)["label"],
+                "fsr4_upscaler_sha256": file_sha256(target_dir / FSR4_UPSCALER_FILENAME) if (target_dir / FSR4_UPSCALER_FILENAME).exists() else None,
+                "framegen_backend": framegen_backend,
+                "framegen_backend_label": FRAMEGEN_BACKENDS[framegen_backend],
+                "patched_at": datetime.now(timezone.utc).isoformat(),
+            }
+            # The marker is written last, so an interrupted copy is never advertised as a complete patch.
+            write_json(previous_marker, payload)
+            return {
+                "status": "success",
+                "message": f"OptiScaler files copied to {target_dir} using {self.bundle.variant_info(variant)['label']}",
+                "fsr4_variant": variant,
+                "fsr4_variant_label": self.bundle.variant_info(variant)["label"],
+                "fsr4_upscaler_sha256": payload["fsr4_upscaler_sha256"],
+                "optiscaler_version": payload["optiscaler_version"],
+                "framegen_backend": framegen_backend,
+            }
+        except (OSError, RuntimeError, ValueError) as exc:
+            self._rollback(target_dir, managed, backups)
+            self._log(f"Patch failed for {target_dir}: {exc}")
+            return {"status": "error", "message": f"Patch failed: {exc}"}
+
+    def _managed_entries(self, target_dir: Path, metadata: dict) -> tuple[list[tuple[dict, Path]], list[str]]:
+        entries: list[tuple[dict, Path]] = []
+        errors: list[str] = []
+        for entry in metadata.get("managed_files", []):
+            if not isinstance(entry, dict) or not entry.get("path"):
+                errors.append("Patch marker contains an invalid managed file entry.")
+                continue
+            try:
+                path = self._safe_path(target_dir, entry["path"])
+            except ValueError as exc:
+                errors.append(str(exc))
+                continue
+            expected = str(entry.get("sha256") or "")
+            if not expected:
+                errors.append(f"Patch marker has no hash for {entry['path']}.")
+            elif path.exists() and (not path.is_file() or file_sha256(path).lower() != expected.lower()):
+                errors.append(f"Refusing to remove modified managed file: {path}")
+            entries.append((entry, path))
+        return entries, errors
+
+    def _restore_backups(self, target_dir: Path, metadata: dict) -> list[str]:
+        restored: list[str] = []
+        for item in metadata.get("backups", []):
+            if not isinstance(item, dict) or not item.get("path") or not item.get("backup"):
+                raise ValueError("Patch marker contains an invalid backup entry.")
+            path = self._safe_path(target_dir, item["path"])
+            backup = self._safe_path(target_dir, item["backup"])
+            if not backup.exists():
+                continue
+            if not backup.is_file():
+                raise ValueError(f"Patch backup is not a file: {backup}")
+            expected = str(item.get("sha256") or "")
+            if expected and file_sha256(backup).lower() != expected.lower():
+                raise RuntimeError(f"Refusing to restore a modified backup: {backup}")
+            if path.exists():
+                raise RuntimeError(f"Refusing to overwrite a file while restoring backup: {path}")
+            path.parent.mkdir(parents=True, exist_ok=True)
+            shutil.move(backup, path)
+            restored.append(str(item["path"]))
+
+        # Older releases used ``name.b`` backups and listed only their base names.
+        for raw_name in metadata.get("backed_up_files", []):
+            name = Path(str(raw_name)).name
+            if name not in RESTORABLE_BACKUP_FILES:
+                continue
+            original = self._safe_path(target_dir, name)
+            backup = self._safe_path(target_dir, name + ".b")
+            if backup.exists() and not original.exists():
+                shutil.move(backup, original)
+                restored.append(name)
+        return restored
+
+    def _validate_backups(self, target_dir: Path, metadata: dict) -> None:
+        for item in metadata.get("backups", []):
+            if not isinstance(item, dict) or not item.get("path") or not item.get("backup"):
+                raise ValueError("Patch marker contains an invalid backup entry.")
+            self._safe_path(target_dir, item["path"])
+            backup = self._safe_path(target_dir, item["backup"])
+            if not backup.exists():
+                continue
+            if not backup.is_file():
+                raise ValueError(f"Patch backup is not a file: {backup}")
+            expected = str(item.get("sha256") or "")
+            if expected and file_sha256(backup).lower() != expected.lower():
+                raise RuntimeError(f"Refusing to restore a modified backup: {backup}")
+
+    def _legacy_owned_paths(self, target_dir: Path, metadata: dict) -> list[Path]:
+        paths: list[Path] = []
+        for entry in metadata.get("managed_files", []):
+            if isinstance(entry, dict) and entry.get("path"):
+                try:
+                    paths.append(self._safe_path(target_dir, entry["path"]))
+                except ValueError:
+                    continue
+
+        variant = self.bundle.normalize_variant(metadata.get("fsr4_variant"))
+        proxy_sources = [
+            self.bundle.fgmod_path / "OptiScaler.dll",
+            self.bundle.fgmod_path / "renames",
+            self.bundle.variant_dir(variant) / "renames",
+        ]
+        for filename in INJECTOR_FILENAMES:
+            target = target_dir / filename
+            if not target.is_file():
+                continue
+            matches_bundle = False
+            for source in proxy_sources:
+                candidate = source if source.is_file() and source.name == filename else source / filename
+                if candidate.is_file() and files_match(target, candidate):
+                    matches_bundle = True
+                    break
+            if matches_bundle:
+                paths.append(target)
+        for filename in SUPPORT_FILES + VARIANT_EXTRA_FILENAMES + [FSR4_UPSCALER_FILENAME]:
+            target = target_dir / filename
+            if target.is_file() and self.bundle.is_managed_support_file(target):
+                paths.append(target)
+        for relative in (Path("plugins/OptiPatcher.asi"),):
+            target = target_dir / relative
+            source = self.bundle.fgmod_path / relative
+            if target.is_file() and source.is_file() and files_match(target, source):
+                paths.append(target)
+        d3d12_source = self.bundle.fgmod_path / "D3D12_Optiscaler"
+        d3d12_target = target_dir / "D3D12_Optiscaler"
+        if d3d12_source.is_dir() and d3d12_target.is_dir():
+            for source in d3d12_source.rglob("*"):
+                if source.is_file():
+                    candidate = d3d12_target / source.relative_to(d3d12_source)
+                    if candidate.is_file() and files_match(candidate, source):
+                        paths.append(candidate)
+        unique: list[Path] = []
+        seen: set[str] = set()
+        for path in paths:
+            if str(path) not in seen:
+                unique.append(path)
+                seen.add(str(path))
+        return unique
+
+    def _unpatch_target(self, target_dir: Path, marker_path: Path | None) -> dict:
+        metadata = self._read_marker(marker_path) if marker_path else {
+            "backed_up_files": [
+                name for name in RESTORABLE_BACKUP_FILES
+                if (target_dir / f"{name}.b").is_file()
+            ],
+        }
+        try:
+            if marker_path and marker_path.exists() and not metadata:
+                return {"status": "error", "message": f"Patch marker is unreadable: {marker_path}"}
+            schema_version = int(metadata.get("schema_version") or 1) if metadata else 1
+            if schema_version >= MANIFEST_SCHEMA_VERSION:
+                entries, errors = self._managed_entries(target_dir, metadata)
+                if errors:
+                    return {"status": "error", "message": " ".join(errors)}
+                self._validate_backups(target_dir, metadata)
+                managed_paths = [path for _, path in entries]
+                for _, path in entries:
+                    if path.exists():
+                        path.unlink()
+                restored = self._restore_backups(target_dir, metadata)
+                self._cleanup_empty_directories(target_dir, [str(path.relative_to(target_dir)) for path in managed_paths])
+            else:
+                owned = self._legacy_owned_paths(target_dir, metadata)
+                entries, errors = self._managed_entries(target_dir, metadata)
+                if errors:
+                    return {"status": "error", "message": " ".join(errors)}
+                owned.extend(path for _, path in entries if path not in owned)
+                for path in owned:
+                    if path.is_file():
+                        path.unlink()
+                restored = self._restore_backups(target_dir, metadata)
+                self._cleanup_empty_directories(target_dir, [str(path.relative_to(target_dir)) for path in owned])
+            if marker_path and marker_path.exists():
+                marker_path.unlink()
+            return {
+                "status": "success",
+                "message": f"OptiScaler files removed from {target_dir}",
+                "restored_files": restored,
+            }
+        except (OSError, RuntimeError, ValueError) as exc:
+            self._log(f"Unpatch failed for {target_dir}: {exc}")
+            return {"status": "error", "message": f"Unpatch failed: {exc}"}
+
+    def resolve_target_directory(self, directory: str) -> Path:
+        target = Path(directory).expanduser()
+        if not target.exists():
+            raise FileNotFoundError(f"Target directory does not exist: {directory}")
+        if not target.is_dir():
+            raise NotADirectoryError(f"Target path is not a directory: {directory}")
+        if not os.access(target, os.W_OK | os.X_OK):
+            raise PermissionError(f"Insufficient permissions for {directory}")
+        return target.resolve()
+
+    def manual_patch_directory(
+        self,
+        directory: str,
+        dll_name: str,
+        fsr4_variant: str,
+        framegen_backend: str | None = None,
+    ) -> dict:
+        try:
+            target = self.resolve_target_directory(directory)
+        except (FileNotFoundError, NotADirectoryError, PermissionError) as exc:
+            return {"status": "error", "message": str(exc)}
+        marker = target / MARKER_FILENAME
+        previous_metadata = self._read_marker(marker) if marker.exists() else {}
+        previous_variant = previous_metadata.get("fsr4_variant")
+        if marker.exists():
+            if str(previous_metadata.get("appid")) not in ("", "manual", "None"):
+                return {"status": "error", "message": "This directory is managed by an AppID patch; unpatch it there first."}
+            cleanup = self._unpatch_target(target, marker)
+            if cleanup["status"] != "success":
+                return cleanup
+        return self._patch_directory(
+            target,
+            dll_name,
+            self.bundle.selected_variant(fsr4_variant),
+            self.bundle.selected_backend(framegen_backend),
+            appid="manual",
+            game_name="Manual patch",
+            original_launch_options="",
+            previous_variant=previous_variant,
+        )
+
+    def manual_unpatch_directory(self, directory: str) -> dict:
+        try:
+            target = self.resolve_target_directory(directory)
+        except (FileNotFoundError, NotADirectoryError, PermissionError) as exc:
+            return {"status": "error", "message": str(exc)}
+        marker = target / MARKER_FILENAME
+        return self._unpatch_target(target, marker if marker.exists() else None)
+
+    def list_installed_games(self) -> dict:
+        try:
+            return {
+                "status": "success",
+                "games": [
+                    {
+                        "appid": str(game["appid"]),
+                        "name": game["name"],
+                        "install_found": Path(game["install_path"]).exists(),
+                    }
+                    for game in self.steam.find_installed_games()
+                ],
+            }
+        except Exception as exc:
+            self._log(str(exc))
+            return {"status": "error", "message": str(exc)}
+
+    def get_game_status(self, appid: str) -> dict:
+        try:
+            game_info = self.steam.game_record(str(appid))
+            if not game_info:
+                return {
+                    "status": "success", "appid": str(appid), "install_found": False, "patched": False,
+                    "dll_name": None, "target_dir": None, "fsr4_variant": None, "fsr4_variant_label": None,
+                    "framegen_backend": None, "message": "Game not found in Steam library.",
+                }
+            install_root = Path(game_info["install_path"])
+            base = {
+                "status": "success", "appid": str(appid), "name": game_info["name"],
+                "install_found": install_root.exists(), "patched": False, "dll_name": None,
+                "target_dir": None, "fsr4_variant": None, "fsr4_variant_label": None,
+                "framegen_backend": None,
+            }
+            if not install_root.exists():
+                return {**base, "message": "Game install directory not found."}
+            marker = self._find_marker(install_root, str(appid))
+            if not marker:
+                return {**base, "message": "Not patched."}
+            metadata = self._read_marker(marker)
+            target_dir = self._marker_target(marker, metadata)
+            dll_name = str(metadata.get("dll_name") or "dxgi.dll")
+            upscaler = target_dir / FSR4_UPSCALER_FILENAME
+            upscaler_sha256 = file_sha256(upscaler) if upscaler.is_file() else None
+            variant = self.bundle.detect_variant(target_dir, upscaler_sha256) or self.bundle.normalize_variant(metadata.get("fsr4_variant"))
+            backend = self.bundle.normalize_backend(metadata.get("framegen_backend") or self.bundle.selected_backend())
+            dll_present = (target_dir / dll_name).is_file()
+            return {
+                **base,
+                "patched": dll_present,
+                "dll_name": dll_name,
+                "target_dir": str(target_dir),
+                "patched_at": metadata.get("patched_at"),
+                "optiscaler_version": metadata.get("optiscaler_version"),
+                "fsr4_variant": variant,
+                "fsr4_variant_label": self.bundle.variant_info(variant)["label"],
+                "fsr4_upscaler_sha256": upscaler_sha256,
+                "framegen_backend": backend,
+                "framegen_backend_label": FRAMEGEN_BACKENDS[backend],
+                "message": f"Patched using {dll_name} with {self.bundle.variant_info(variant)['label']}." if dll_present else f"Marker found but {dll_name} is missing. Reinstall recommended.",
+            }
+        except Exception as exc:
+            self._log(f"get_game_status failed for {appid}: {exc}")
+            return {"status": "error", "message": str(exc)}
+
+    @staticmethod
+    def build_managed_launch_options(dll_name: str) -> str:
+        if dll_name == "OptiScaler.asi":
+            return "SteamDeck=0 %command%"
+        base = dll_name.replace(".dll", "")
+        return f"WINEDLLOVERRIDES={base}=n,b SteamDeck=0 %command%"
+
+    @staticmethod
+    def is_managed_launch_options(options: str) -> bool:
+        normalized = " ".join((options or "").replace('"', "").split())
+        if not normalized:
+            return False
+        return any(
+            dll_name != "OptiScaler.asi" and f"WINEDLLOVERRIDES={dll_name.replace('.dll', '')}=n,b" in normalized
+            for dll_name in VALID_DLL_NAMES
+        ) or "fgmod/fgmod" in normalized
+
+    def patch_game(
+        self,
+        appid: str,
+        dll_name: str,
+        current_launch_options: str,
+        fsr4_variant: str,
+        framegen_backend: str | None = None,
+    ) -> dict:
+        try:
+            if dll_name not in VALID_DLL_NAMES:
+                return {"status": "error", "message": f"Invalid proxy DLL name: {dll_name}"}
+            game_info = self.steam.game_record(str(appid))
+            if not game_info:
+                return {"status": "error", "message": "Game not found in Steam library."}
+            install_root = Path(game_info["install_path"])
+            if not install_root.exists():
+                return {"status": "error", "message": "Game install directory does not exist."}
+            if self.steam.is_game_running(game_info):
+                return {"status": "error", "message": "Close the game before patching."}
+            if not self.bundle.fgmod_path.exists():
+                return {"status": "error", "message": "OptiScaler bundle not installed. Run Install first."}
+
+            existing_marker = self._find_marker(install_root)
+            existing_metadata = self._read_marker(existing_marker) if existing_marker else {}
+            if existing_marker and str(existing_metadata.get("appid")) not in (str(appid), "manual", "None"):
+                return {"status": "error", "message": "Another Framegen patch marker was found in this game install."}
+            original_options = current_launch_options or ""
+            stored_options = str(existing_metadata.get("original_launch_options") or "")
+            if stored_options and not self.is_managed_launch_options(stored_options):
+                original_options = stored_options
+            if self.is_managed_launch_options(original_options):
+                original_options = ""
+
+            if existing_marker:
+                old_target = self._marker_target(existing_marker, existing_metadata)
+                cleanup = self._unpatch_target(old_target, existing_marker)
+                if cleanup["status"] != "success":
+                    return cleanup
+            target_dir, _ = self.steam.guess_patch_target(game_info)
+            result = self._patch_directory(
+                target_dir,
+                dll_name,
+                self.bundle.selected_variant(fsr4_variant),
+                self.bundle.selected_backend(framegen_backend),
+                appid=str(appid),
+                game_name=game_info["name"],
+                original_launch_options=original_options,
+                previous_variant=existing_metadata.get("fsr4_variant"),
+            )
+            if result["status"] != "success":
+                return result
+            backend = result.get("framegen_backend") or self.bundle.selected_backend(framegen_backend)
+            return {
+                **result,
+                "appid": str(appid),
+                "name": game_info["name"],
+                "dll_name": dll_name,
+                "target_dir": str(target_dir),
+                "launch_options": self.build_managed_launch_options(dll_name),
+                "original_launch_options": original_options,
+                "framegen_backend": backend,
+                "message": f"Patched {game_info['name']} using {dll_name} with {result.get('fsr4_variant_label') or self.bundle.variant_info(fsr4_variant)['label']}.",
+            }
+        except Exception as exc:
+            self._log(f"patch_game failed for {appid}: {exc}")
+            return {"status": "error", "message": str(exc)}
+
+    def unpatch_game(self, appid: str) -> dict:
+        try:
+            game_info = self.steam.game_record(str(appid))
+            if not game_info:
+                return {"status": "error", "message": "Game not found in Steam library."}
+            install_root = Path(game_info["install_path"])
+            if not install_root.exists():
+                return {"status": "success", "appid": str(appid), "name": game_info["name"], "launch_options": "", "message": "Game install directory does not exist."}
+            if self.steam.is_game_running(game_info):
+                return {"status": "error", "message": "Close the game before unpatching."}
+            marker = self._find_marker(install_root, str(appid))
+            if not marker:
+                return {"status": "success", "appid": str(appid), "name": game_info["name"], "launch_options": "", "message": "No Framegen patch found for this game."}
+            metadata = self._read_marker(marker)
+            target_dir = self._marker_target(marker, metadata)
+            original_options = str(metadata.get("original_launch_options") or "")
+            cleanup = self._unpatch_target(target_dir, marker)
+            if cleanup["status"] != "success":
+                return {**cleanup, "appid": str(appid), "name": game_info["name"]}
+            self._log(f"unpatch_game success: appid={appid} target={target_dir}")
+            return {
+                "status": "success",
+                "appid": str(appid),
+                "name": game_info["name"],
+                "launch_options": original_options,
+                "message": f"Unpatched {game_info['name']}.",
+            }
+        except Exception as exc:
+            self._log(f"unpatch_game failed for {appid}: {exc}")
+            return {"status": "error", "message": str(exc)}
diff --git a/backend/steam.py b/backend/steam.py
new file mode 100644
index 0000000..c2e90b0
--- /dev/null
+++ b/backend/steam.py
@@ -0,0 +1,187 @@
+"""Steam library discovery and conservative executable selection."""
+
+import re
+import subprocess
+from pathlib import Path
+from typing import Callable
+
+
+Logger = Callable[[str], None]
+
+BAD_EXE_SUBSTRINGS = [
+    "crashreport",
+    "crashreportclient",
+    "eac",
+    "easyanticheat",
+    "beclient",
+    "eosbootstrap",
+    "benchmark",
+    "uninstall",
+    "setup",
+    "launcher",
+    "updater",
+    "bootstrap",
+    "_redist",
+    "prereq",
+]
+
+
+class SteamLibrary:
+    def __init__(self, home: Path, logger: Logger):
+        self.home = home
+        self.logger = logger
+
+    def steam_common_path(self) -> Path:
+        return self.home / ".local" / "share" / "Steam" / "steamapps" / "common"
+
+    def _steam_root_candidates(self) -> list[Path]:
+        candidates = [
+            self.home / ".local" / "share" / "Steam",
+            self.home / ".steam" / "steam",
+            self.home / ".steam" / "root",
+            self.home / ".var" / "app" / "com.valvesoftware.Steam" / "home" / ".local" / "share" / "Steam",
+            self.home / ".var" / "app" / "com.valvesoftware.Steam" / "home" / ".steam" / "steam",
+        ]
+        unique: list[Path] = []
+        seen: set[str] = set()
+        for candidate in candidates:
+            key = str(candidate)
+            if key not in seen:
+                unique.append(candidate)
+                seen.add(key)
+        return unique
+
+    def _steam_library_paths(self) -> list[Path]:
+        library_paths: list[Path] = []
+        seen: set[str] = set()
+        for steam_root in self._steam_root_candidates():
+            if steam_root.exists() and str(steam_root) not in seen:
+                library_paths.append(steam_root)
+                seen.add(str(steam_root))
+            library_file = steam_root / "steamapps" / "libraryfolders.vdf"
+            if not library_file.exists():
+                continue
+            try:
+                for line in library_file.read_text(encoding="utf-8", errors="replace").splitlines():
+                    if '"path"' not in line:
+                        continue
+                    path = line.split('"path"', 1)[1].strip().strip('"').replace("\\\\", "/")
+                    candidate = Path(path)
+                    if str(candidate) not in seen:
+                        library_paths.append(candidate)
+                        seen.add(str(candidate))
+            except OSError as exc:
+                self.logger(f"[Framegen] failed to parse libraryfolders: {library_file}: {exc}")
+        return library_paths
+
+    def find_installed_games(self, appid: str | None = None) -> list[dict]:
+        games: list[dict] = []
+        for library_path in self._steam_library_paths():
+            steamapps_path = library_path / "steamapps"
+            if not steamapps_path.exists():
+                continue
+            for appmanifest in steamapps_path.glob("appmanifest_*.acf"):
+                game_info: dict = {
+                    "appid": "",
+                    "name": "",
+                    "library_path": str(library_path),
+                    "install_path": "",
+                }
+                install_dir = ""
+                try:
+                    for line in appmanifest.read_text(encoding="utf-8", errors="replace").splitlines():
+                        if '"appid"' in line:
+                            game_info["appid"] = line.split('"appid"', 1)[1].strip().strip('"')
+                        elif '"name"' in line:
+                            game_info["name"] = line.split('"name"', 1)[1].strip().strip('"')
+                        elif '"installdir"' in line:
+                            install_dir = line.split('"installdir"', 1)[1].strip().strip('"')
+                except OSError as exc:
+                    self.logger(f"[Framegen] skipping manifest {appmanifest}: {exc}")
+                    continue
+                if not game_info["appid"] or not game_info["name"]:
+                    continue
+                if "Proton" in game_info["name"] or "Steam Linux Runtime" in game_info["name"]:
+                    continue
+                game_info["install_path"] = str(steamapps_path / "common" / install_dir) if install_dir else str(Path())
+                if appid is None or str(game_info["appid"]) == str(appid):
+                    games.append(game_info)
+        deduped = {str(game["appid"]): game for game in games}
+        return sorted(deduped.values(), key=lambda game: game["name"].lower())
+
+    def game_record(self, appid: str) -> dict | None:
+        matches = self.find_installed_games(appid)
+        return matches[0] if matches else None
+
+    @staticmethod
+    def normalized_path_string(value: str) -> str:
+        normalized = value.lower().replace("\\", "/")
+        normalized = normalized.replace("z:/", "/")
+        return normalized.replace("//", "/")
+
+    def candidate_executables(self, install_root: Path) -> list[Path]:
+        if not install_root.exists():
+            return []
+        try:
+            return [exe for exe in install_root.rglob("*.exe") if exe.is_file()]
+        except OSError as exc:
+            self.logger(f"[Framegen] exe scan failed for {install_root}: {exc}")
+            return []
+
+    def _exe_score(self, exe: Path, install_root: Path, game_name: str) -> int:
+        normalized = self.normalized_path_string(str(exe))
+        name = exe.name.lower()
+        score = 0
+        if normalized.endswith("-win64-shipping.exe"):
+            score += 300
+        if "shipping.exe" in name:
+            score += 220
+        if "/binaries/win64/" in normalized:
+            score += 200
+        if "/win64/" in normalized:
+            score += 80
+        if exe.parent == install_root:
+            score += 20
+        sanitized_game = re.sub(r"[^a-z0-9]", "", game_name.lower())
+        sanitized_name = re.sub(r"[^a-z0-9]", "", exe.stem.lower())
+        sanitized_root = re.sub(r"[^a-z0-9]", "", install_root.name.lower())
+        if sanitized_game and sanitized_game in sanitized_name:
+            score += 120
+        if sanitized_root and sanitized_root in sanitized_name:
+            score += 90
+        for bad in BAD_EXE_SUBSTRINGS:
+            if bad in normalized:
+                score -= 200
+        return score - len(exe.parts)
+
+    def best_running_executable(self, candidates: list[Path]) -> Path | None:
+        if not candidates:
+            return None
+        try:
+            result = subprocess.run(["ps", "-eo", "args="], capture_output=True, text=True, check=False)
+            process_lines = result.stdout.splitlines()
+        except OSError as exc:
+            self.logger(f"[Framegen] running exe scan failed: {exc}")
+            return None
+        normalized_candidates = [(exe, self.normalized_path_string(str(exe))) for exe in candidates]
+        matches: list[tuple[int, Path]] = []
+        for line in process_lines:
+            normalized_line = self.normalized_path_string(line)
+            for exe, normalized_exe in normalized_candidates:
+                if normalized_exe in normalized_line:
+                    matches.append((len(normalized_exe), exe))
+        return max(matches, key=lambda item: item[0])[1] if matches else None
+
+    def guess_patch_target(self, game_info: dict) -> tuple[Path, Path | None]:
+        install_root = Path(game_info["install_path"])
+        candidates = self.candidate_executables(install_root)
+        if not candidates:
+            return install_root, None
+        running_exe = self.best_running_executable(candidates)
+        if running_exe:
+            return running_exe.parent, running_exe
+        best = max(candidates, key=lambda exe: self._exe_score(exe, install_root, game_info["name"]))
+        return best.parent, best
+
+    def is_game_running(self, game_info: dict) -> bool:
+        return self.best_running_executable(self.candidate_executables(Path(game_info["install_path"]))) is not None
diff --git a/defaults/assets/fgmod.sh b/defaults/assets/fgmod.sh
index e0ee1d2..33207f3 100755
--- a/defaults/assets/fgmod.sh
+++ b/defaults/assets/fgmod.sh
@@ -305,7 +305,11 @@ fi
 
 # === OptiScaler env variables Handling ===
 if [[ -f "$fgmod_path/update-optiscaler-config.py" ]]; then
-  python "$fgmod_path/update-optiscaler-config.py" "$exe_folder_path/OptiScaler.ini"
+  if [[ -n "$python_bin" ]]; then
+    "$python_bin" "$fgmod_path/update-optiscaler-config.py" "$exe_folder_path/OptiScaler.ini"
+  else
+    echo " Python is unavailable; skipping OptiScaler config migration"
+  fi
 fi
 
 # OptiScaler 0.9.0-pre11 can assert on Proton when HQ font auto mode tries to load
diff --git a/main.py b/main.py
index b1a8079..c5a3e01 100644
--- a/main.py
+++ b/main.py
@@ -1,1663 +1,65 @@
-import decky
-import os
-import subprocess
-import json
-import shutil
-import re
-import filecmp
-import hashlib
-from datetime import datetime, timezone
-from pathlib import Path
-
-OPTISCALER_ARCHIVE_ASSET = {
-    "name": "Optiscaler_0.9.4-final.20260718._MM.7z",
-    "sha256": "575cb4df866116093df75af607e37fd70e10f5163e0f23fd5c804142e80ef0ad",
-    "version": "0.9.4-final.20260718",
-}
-
-FSR4_INT8_ASSET = {
-    "name": "amd_fidelityfx_upscaler_dx12.dll",
-    "sha256": "c7720bc16bede334f59a1a32cd22edbcbbb159685ed5240e61350a5fb0bc8a94",
-    "version": "4.0.2c",
-}
-
-FSR4_OFFICIAL_411_ASSET = {
-    "name": "amdxcffx64.dll",
-    "sha256": "a2b136b6affd35a49b141a936be935f7d5ddc8d8f9b8c9afbe62ff9ddb2538a0",
-    "version": "4.1.1-official",
-}
-
-FSR4_VALVE_411_ASSET = {
-    "name": "amdxcffx64_valve_2.3.0.2913.dll",
-    "sha256": "4e7dc37aebea3a90e3d3cc43e24cb2b54176b2535315f20dbe63b3b7cfc56b1e",
-    "version": "4.1.1-valve-2.3.0.2913",
-}
-
-AMDXC64_RDNA2_ASSET = {
-    "name": "amdxc64.dll",
-    "sha256": "a0a0af61d475e30a70966b3459f3793df772faf8f26ae3261d10554ff592cbd5",
-    "version": "8.18.10.0474",
-}
-
-OPTISCALER_PRE10_ASSET = {
-    "name": "OptiScaler_0.10.0-pre1.20260622_135940.dll",
-    "sha256": "b374b19081cc066365d0c6da4808d768e16469b0cbdfc478b6e95999947d5364",
-    "version": "0.10.0-pre1.20260622_135940",
-}
-
-OPTIPATCHER_ASSET = {
-    "name": "OptiPatcher_rolling.asi",
-    "sha256": "88b9e1be3559737cd205fdf5f2c8550cf1923fb1def4c603e5bf03c3e84131b1",
-    "version": "rolling",
-}
-
-FSR4_UPSCALER_FILENAME = "amd_fidelityfx_upscaler_dx12.dll"
-FSR4_DRIVER_OVERRIDE_FILENAME = "amdxcffx64.dll"
-INSTALL_MANIFEST_FILENAME = "install-manifest.json"
-VERSION_FILENAME = "version.txt"
-DEFAULT_FSR4_VARIANT = "rdna23-int8"
-
-FSR4_VARIANTS = {
-    "rdna23-int8": {
-        "label": "4.0.2c / RDNA2-3 compatibility",
-        "dir_name": "fsr4-rdna2-3",
-        "sha256": "c7720bc16bede334f59a1a32cd22edbcbbb159685ed5240e61350a5fb0bc8a94",
-        "source_asset_name": FSR4_INT8_ASSET["name"],
-        "source_version": FSR4_INT8_ASSET["version"],
-        "uses_archive_native": False,
-        "extra_files": [],
-    },
-    "rdna4-native": {
-        "label": "4.1.1 SDK / RDNA3 dGPU + RDNA4",
-        "dir_name": "fsr4-rdna4",
-        "sha256": "d0dcccc74a43c44ba435b7a369b456e0970d8a4464e4bd683119b374f2c9fb46",
-        "source_asset_name": OPTISCALER_ARCHIVE_ASSET["name"],
-        "source_version": OPTISCALER_ARCHIVE_ASSET["version"],
-        "uses_archive_native": True,
-        "extra_files": [],
-    },
-    "rdna34-official-411": {
-        "label": "4.1.1 driver override / RDNA3-4",
-        "dir_name": "fsr4-rdna3-4-official-411",
-        "sha256": "d0dcccc74a43c44ba435b7a369b456e0970d8a4464e4bd683119b374f2c9fb46",
-        "source_asset_name": OPTISCALER_ARCHIVE_ASSET["name"],
-        "source_version": OPTISCALER_ARCHIVE_ASSET["version"],
-        "uses_archive_native": True,
-        "extra_files": [
-            {
-                "name": FSR4_DRIVER_OVERRIDE_FILENAME,
-                "sha256": FSR4_OFFICIAL_411_ASSET["sha256"],
-                "source_asset_name": FSR4_OFFICIAL_411_ASSET["name"],
-                "source_version": FSR4_OFFICIAL_411_ASSET["version"],
-            }
-        ],
-        "config_overrides": {},
-    },
-    "rdna2-valve-411-pre10": {
-        "label": "4.1.1 Valve RDNA2 compatibility",
-        "dir_name": "fsr4-rdna2-valve-411-pre10",
-        "sha256": "d0dcccc74a43c44ba435b7a369b456e0970d8a4464e4bd683119b374f2c9fb46",
-        "source_asset_name": OPTISCALER_ARCHIVE_ASSET["name"],
-        "source_version": OPTISCALER_ARCHIVE_ASSET["version"],
-        "uses_archive_native": True,
-        "injector": {
-            "name": "OptiScaler.dll",
-            "sha256": OPTISCALER_PRE10_ASSET["sha256"],
-            "source_asset_name": OPTISCALER_PRE10_ASSET["name"],
-            "source_version": OPTISCALER_PRE10_ASSET["version"],
-        },
-        "extra_files": [
-            {
-                "name": FSR4_DRIVER_OVERRIDE_FILENAME,
-                "sha256": FSR4_VALVE_411_ASSET["sha256"],
-                "source_asset_name": FSR4_VALVE_411_ASSET["name"],
-                "source_version": FSR4_VALVE_411_ASSET["version"],
-            },
-            {
-                "name": "amdxc64.dll",
-                "sha256": AMDXC64_RDNA2_ASSET["sha256"],
-                "source_asset_name": AMDXC64_RDNA2_ASSET["name"],
-                "source_version": AMDXC64_RDNA2_ASSET["version"],
-            }
-        ],
-        "config_overrides": {
-            "FSR.Fsr4ForceModel": "2",
-            "Plugins.LoadCustomAmdxc64OnRdna2": "true",
-        },
-    },
-}
-VARIANT_EXTRA_FILENAMES = sorted(
-    {
-        extra_file["name"]
-        for variant in FSR4_VARIANTS.values()
-        for extra_file in variant.get("extra_files", [])
-    }
-)
+"""Decky entry point for the Framegen plugin.
 
-PROXY_DLL_BACKUPS = [
-    "dxgi.dll",
-    "winmm.dll",
-    "dbghelp.dll",
-    "version.dll",
-    "wininet.dll",
-    "winhttp.dll",
-    "OptiScaler.asi",
-]
+Decky-facing methods live here; filesystem, Steam, configuration, and patch
+ownership concerns are implemented in ``backend`` services.
+"""
 
-VALID_DLL_NAMES = set(PROXY_DLL_BACKUPS)
-
-INJECTOR_FILENAMES = [
-    *PROXY_DLL_BACKUPS,
-    "nvngx.dll",
-    "_nvngx.dll",
-    "nvngx-wrapper.dll",
-    "dlss-enabler.dll",
-    "OptiScaler.dll",
-]
-
-PATCH_CLEANUP_FILES = [
-    *INJECTOR_FILENAMES,
-    *VARIANT_EXTRA_FILENAMES,
-    "nvapi64.dll",
-    "nvapi64.dll.b",
-    "nvngx.ini",
-    "dlss-enabler-upscaler.dll",
-    "fakenvapi.log",
-    "OptiScaler.log",
-    "dlssg_to_fsr3.log",
-    "dlssg_to_fsr3_amd_is_better-3.0.dll",
-]
-
-PATCH_FINGERPRINT_FILES = [
-    "FRAMEGEN_PATCH",
-    "OptiScaler.ini",
-    "fakenvapi.dll",
-    "fakenvapi.ini",
-    "dlssg_to_fsr3_amd_is_better.dll",
-    "D3D12_Optiscaler",
-]
-
-ORIGINAL_DLL_BACKUPS = [
-    "d3dcompiler_47.dll",
-    "amd_fidelityfx_dx12.dll",
-    "amd_fidelityfx_framegeneration_dx12.dll",
-    FSR4_UPSCALER_FILENAME,
-    FSR4_DRIVER_OVERRIDE_FILENAME,
-    "amdxc64.dll",
-    "amd_fidelityfx_vk.dll",
-]
-
-RESTORABLE_BACKUP_FILES = [
-    *PROXY_DLL_BACKUPS,
-    *ORIGINAL_DLL_BACKUPS,
-]
-
-SUPPORT_FILES = [
-    "libxess.dll",
-    "libxess_dx11.dll",
-    "libxess_fg.dll",
-    "libxell.dll",
-    "amd_fidelityfx_dx12.dll",
-    "amd_fidelityfx_framegeneration_dx12.dll",
-    "amd_fidelityfx_vk.dll",
-    "dlssg_to_fsr3_amd_is_better.dll",
-    "fakenvapi.dll",
-    "fakenvapi.ini",
-]
+from pathlib import Path
 
-MARKER_FILENAME = "FRAMEGEN_PATCH"
+import decky
 
-BAD_EXE_SUBSTRINGS = [
-    "crashreport",
-    "crashreportclient",
-    "eac",
-    "easyanticheat",
-    "beclient",
-    "eosbootstrap",
-    "benchmark",
-    "uninstall",
-    "setup",
-    "launcher",
-    "updater",
-    "bootstrap",
-    "_redist",
-    "prereq",
-]
+from backend.assets import DEFAULT_FRAMEGEN_BACKEND, DEFAULT_FSR4_VARIANT
+from backend.bundle import BundleManager
+from backend.patcher import PatchManager
+from backend.steam import SteamLibrary
 
-LEGACY_FILES = [
-    "dlssg_to_fsr3.ini",
-    "dlssg_to_fsr3.log",
-    "nvapi64.dll",
-    "nvapi64.dll.b",
-    "fakenvapi.log",
-    "dlss-enabler.dll",
-    "dlss-enabler-upscaler.dll",
-    "dlss-enabler.log",
-    "nvngx.ini",
-    "nvngx-wrapper.dll",
-    "_nvngx.dll",
-    "dlssg_to_fsr3_amd_is_better-3.0.dll",
-    "OptiScaler.asi",
-    "OptiScaler.ini",
-    "OptiScaler.log",
-]
 
 class Plugin:
+    def __init__(self):
+        home = Path(str(decky.HOME))
+        plugin_dir = Path(str(decky.DECKY_PLUGIN_DIR))
+        logger = decky.logger.error
+        self._bundle = BundleManager(home, plugin_dir, logger)
+        self._steam = SteamLibrary(home, logger)
+        self._patcher = PatchManager(home, self._bundle, self._steam, logger)
+
     async def _main(self):
         decky.logger.info("Framegen plugin loaded")
 
     async def _unload(self):
         decky.logger.info("Framegen plugin unloaded.")
-        
-    def _create_renamed_copies(self, source_file, renames_dir):
-        """Create renamed copies of the OptiScaler.dll file"""
-        try:
-            renames_dir.mkdir(exist_ok=True)
-            
-            rename_files = [
-                "dxgi.dll",
-                "winmm.dll",
-                "dbghelp.dll",
-                "version.dll",
-                "wininet.dll",
-                "winhttp.dll",
-                "OptiScaler.asi"
-            ]
-            
-            if source_file.exists():
-                for rename_file in rename_files:
-                    dest_file = renames_dir / rename_file
-                    shutil.copy2(source_file, dest_file)
-                    decky.logger.info(f"Created renamed copy: {dest_file}")
-                return True
-            else:
-                decky.logger.error(f"Source file {source_file} does not exist")
-                return False
-                
-        except Exception as e:
-            decky.logger.error(f"Failed to create renamed copies: {e}")
-            return False
-    
-    def _copy_launcher_scripts(self, assets_dir, extract_path):
-        """Copy launcher scripts from assets directory"""
-        try:
-            # Copy fgmod script
-            fgmod_script_src = assets_dir / "fgmod.sh"
-            fgmod_script_dest = extract_path / "fgmod"
-            if fgmod_script_src.exists():
-                shutil.copy2(fgmod_script_src, fgmod_script_dest)
-                fgmod_script_dest.chmod(0o755)
-                decky.logger.info(f"Copied fgmod script to {fgmod_script_dest}")
-            
-            # Copy uninstaller script
-            uninstaller_src = assets_dir / "fgmod-uninstaller.sh"
-            uninstaller_dest = extract_path / "fgmod-uninstaller.sh"
-            if uninstaller_src.exists():
-                shutil.copy2(uninstaller_src, uninstaller_dest)
-                uninstaller_dest.chmod(0o755)
-                decky.logger.info(f"Copied uninstaller script to {uninstaller_dest}")
-
-            # Copy optiscaler config updater script
-            optiscaler_config_updater_src = assets_dir / "update-optiscaler-config.py"
-            optiscaler_config_updater_dest = extract_path / "update-optiscaler-config.py"
-            if optiscaler_config_updater_src.exists():
-                shutil.copy2(optiscaler_config_updater_src, optiscaler_config_updater_dest)
-                optiscaler_config_updater_dest.chmod(0o755)
-                decky.logger.info(f"Copied update-optiscaler-config.py script to {optiscaler_config_updater_dest}")
-                
-            return True
-        except Exception as e:
-            decky.logger.error(f"Failed to copy launcher scripts: {e}")
-            return False
-    
-    def _files_match(self, file_a: Path, file_b: Path) -> bool:
-        try:
-            return file_a.exists() and file_b.exists() and filecmp.cmp(file_a, file_b, shallow=False)
-        except Exception:
-            return False
-
-    def _is_bundled_proxy_copy(self, file_path: Path, fgmod_path: Path) -> bool:
-        bundled_copy = fgmod_path / "renames" / file_path.name
-        return self._files_match(file_path, bundled_copy)
-
-    def _has_patch_fingerprint(self, directory: Path) -> bool:
-        return any((directory / filename).exists() for filename in PATCH_FINGERPRINT_FILES)
-
-    def _backup_preexisting_proxy_files(self, directory: Path, fgmod_path: Path) -> list[str]:
-        backed_up: list[str] = []
-        already_patched = self._has_patch_fingerprint(directory)
-        for filename in PROXY_DLL_BACKUPS:
-            source = directory / filename
-            backup = directory / f"{filename}.b"
-            if not source.exists() or backup.exists():
-                continue
-            if already_patched or self._is_bundled_proxy_copy(source, fgmod_path):
-                continue
-            shutil.move(source, backup)
-            backed_up.append(filename)
-        return backed_up
-
-    def _file_sha256(self, path: Path) -> str:
-        digest = hashlib.sha256()
-        with open(path, "rb") as f:
-            for chunk in iter(lambda: f.read(1024 * 1024), b""):
-                digest.update(chunk)
-        return digest.hexdigest()
-
-    def _read_json_file(self, path: Path) -> dict:
-        try:
-            with open(path, "r", encoding="utf-8") as f:
-                data = json.load(f)
-            return data if isinstance(data, dict) else {}
-        except Exception:
-            return {}
-
-    def _write_json_file(self, path: Path, payload: dict) -> None:
-        with open(path, "w", encoding="utf-8") as f:
-            json.dump(payload, f, indent=2)
-
-    def _extract_archive(self, archive_path: Path, output_dir: Path, members: list[str] | None = None) -> None:
-        output_dir.mkdir(parents=True, exist_ok=True)
-        extract_cmd = [
-            "7z",
-            "x",
-            "-y",
-            "-o" + str(output_dir),
-            str(archive_path),
-        ]
-        if members:
-            extract_cmd.extend(members)
-
-        clean_env = os.environ.copy()
-        clean_env["LD_LIBRARY_PATH"] = ""
-        result = subprocess.run(
-            extract_cmd,
-            capture_output=True,
-            text=True,
-            check=False,
-            env=clean_env,
-        )
-        if result.returncode != 0:
-            raise RuntimeError(result.stderr or result.stdout or f"Failed to extract {archive_path.name}")
-
-    def _verify_bundled_asset(self, path: Path, expected_sha256: str, description: str) -> str:
-        actual_sha256 = self._file_sha256(path)
-        if actual_sha256.lower() != expected_sha256.lower():
-            raise RuntimeError(
-                f"{description} hash mismatch: expected {expected_sha256}, got {actual_sha256}"
-            )
-        return actual_sha256
-
-    def _install_manifest_path(self, fgmod_path: Path) -> Path:
-        return fgmod_path / INSTALL_MANIFEST_FILENAME
-
-    def _load_install_manifest(self, fgmod_path: Path) -> dict:
-        return self._read_json_file(self._install_manifest_path(fgmod_path))
-
-    def _normalize_fsr4_variant(self, fsr4_variant: str | None) -> str:
-        variant = str(fsr4_variant or "").strip()
-        if variant in FSR4_VARIANTS:
-            return variant
-        return DEFAULT_FSR4_VARIANT
-
-    def _selected_fsr4_variant(self, fgmod_path: Path, requested_variant: str | None = None) -> str:
-        normalized_requested = str(requested_variant or "").strip()
-        if normalized_requested in FSR4_VARIANTS:
-            return normalized_requested
-        manifest = self._load_install_manifest(fgmod_path)
-        manifest_variant = str(manifest.get("selected_default_variant") or "").strip()
-        if manifest_variant in FSR4_VARIANTS:
-            return manifest_variant
-        return DEFAULT_FSR4_VARIANT
-
-    def _fsr4_variant_info(self, fsr4_variant: str | None) -> dict:
-        return FSR4_VARIANTS[self._normalize_fsr4_variant(fsr4_variant)]
-
-    def _fsr4_variant_dir(self, fgmod_path: Path, fsr4_variant: str | None) -> Path:
-        variant_id = self._normalize_fsr4_variant(fsr4_variant)
-        return fgmod_path / FSR4_VARIANTS[variant_id]["dir_name"]
-
-    def _fsr4_variant_path(self, fgmod_path: Path, fsr4_variant: str | None) -> Path:
-        return self._fsr4_variant_dir(fgmod_path, fsr4_variant) / FSR4_UPSCALER_FILENAME
-
-    def _fsr4_variant_extra_files(self, fsr4_variant: str | None) -> list[dict]:
-        variant = self._fsr4_variant_info(fsr4_variant)
-        return list(variant.get("extra_files") or [])
-
-    def _fsr4_variant_extra_file_path(self, fgmod_path: Path, fsr4_variant: str | None, filename: str) -> Path:
-        return self._fsr4_variant_dir(fgmod_path, fsr4_variant) / filename
-
-    def _fsr4_variant_injector_info(self, fsr4_variant: str | None) -> dict | None:
-        variant = self._fsr4_variant_info(fsr4_variant)
-        injector = variant.get("injector")
-        return injector if isinstance(injector, dict) else None
-
-    def _fsr4_variant_injector_path(self, fgmod_path: Path, fsr4_variant: str | None) -> Path | None:
-        injector = self._fsr4_variant_injector_info(fsr4_variant)
-        if not injector:
-            return None
-        return self._fsr4_variant_dir(fgmod_path, fsr4_variant) / injector.get("name", "OptiScaler.dll")
-
-    def _fsr4_variant_renamed_proxy_path(self, fgmod_path: Path, fsr4_variant: str | None, dll_name: str) -> Path | None:
-        if not self._fsr4_variant_injector_info(fsr4_variant):
-            return None
-        return self._fsr4_variant_dir(fgmod_path, fsr4_variant) / "renames" / dll_name
-
-    def _fsr4_variant_config_overrides(self, fsr4_variant: str | None) -> dict:
-        variant = self._fsr4_variant_info(fsr4_variant)
-        overrides = variant.get("config_overrides") or {}
-        return dict(overrides) if isinstance(overrides, dict) else {}
-
-    def _split_ini_override_key(self, raw_key: str) -> tuple[str | None, str]:
-        key = str(raw_key).strip()
-        if "." in key:
-            section, section_key = key.split(".", 1)
-            section = section.strip()
-            section_key = section_key.strip()
-            if section and section_key:
-                return section, section_key
-        return None, key
-
-    def _apply_optiscaler_ini_overrides(self, ini_file: Path, overrides: dict) -> bool:
-        if not overrides:
-            return True
-        try:
-            content = ini_file.read_text(encoding="utf-8", errors="replace")
-            newline = "\r\n" if "\r\n" in content else "\n"
-            lines = content.splitlines(keepends=True)
-            section_pattern = re.compile(r"^\s*\[(?P<section>[^\]]+)\]\s*$")
-
-            def ensure_trailing_newline() -> None:
-                if lines and not lines[-1].endswith(("\n", "\r")):
-                    lines[-1] += newline
-
-            def upsert(section: str | None, key: str, value: str) -> None:
-                replacement = f"{key}={value}"
-                key_pattern = re.compile(rf"^(\s*{re.escape(key)}\s*)=.*$")
-
-                if section is None:
-                    for idx, line in enumerate(lines):
-                        if key_pattern.match(line):
-                            line_ending = "\r\n" if line.endswith("\r\n") else ("\n" if line.endswith("\n") else newline)
-                            lines[idx] = f"{replacement}{line_ending}"
-                            return
-                    ensure_trailing_newline()
-                    lines.append(f"{replacement}{newline}")
-                    return
-
-                in_section = False
-                insert_at = None
-                for idx, line in enumerate(lines):
-                    match = section_pattern.match(line.strip())
-                    if match:
-                        if in_section:
-                            insert_at = idx
-                            break
-                        if match.group("section") == section:
-                            in_section = True
-                            continue
-                    if in_section and key_pattern.match(line):
-                        line_ending = "\r\n" if line.endswith("\r\n") else ("\n" if line.endswith("\n") else newline)
-                        lines[idx] = f"{replacement}{line_ending}"
-                        return
-
-                if in_section:
-                    if insert_at is None:
-                        ensure_trailing_newline()
-                        insert_at = len(lines)
-                    lines.insert(insert_at, f"{replacement}{newline}")
-                    return
-
-                ensure_trailing_newline()
-                if lines and lines[-1].strip():
-                    lines.append(newline)
-                lines.append(f"[{section}]{newline}")
-                lines.append(f"{replacement}{newline}")
-
-            for raw_key, raw_value in overrides.items():
-                section, key = self._split_ini_override_key(str(raw_key))
-                value = str(raw_value).strip()
-                if key:
-                    upsert(section, key, value)
-
-            ini_file.write_text("".join(lines), encoding="utf-8")
-            return True
-        except Exception as exc:
-            decky.logger.error(f"Failed to apply OptiScaler.ini overrides to {ini_file}: {exc}")
-            return False
-
-    def _sync_variant_root_extra_files(self, fgmod_path: Path, fsr4_variant: str | None) -> None:
-        selected_extra_files = {extra_file["name"]: extra_file for extra_file in self._fsr4_variant_extra_files(fsr4_variant)}
-        for filename in VARIANT_EXTRA_FILENAMES:
-            root_path = fgmod_path / filename
-            if filename not in selected_extra_files:
-                if root_path.exists():
-                    root_path.unlink()
-                continue
-            source_path = self._fsr4_variant_extra_file_path(fgmod_path, fsr4_variant, filename)
-            if not source_path.exists():
-                raise FileNotFoundError(f"Prepared FSR4 variant extra file missing: {source_path}")
-            shutil.copy2(source_path, root_path)
-
-    def _activate_default_fsr4_variant(self, fgmod_path: Path, fsr4_variant: str | None) -> str:
-        variant_id = self._normalize_fsr4_variant(fsr4_variant)
-        variant_path = self._fsr4_variant_path(fgmod_path, variant_id)
-        if not variant_path.exists():
-            raise FileNotFoundError(f"Prepared FSR4 variant missing: {variant_path}")
-        shutil.copy2(variant_path, fgmod_path / FSR4_UPSCALER_FILENAME)
-        self._sync_variant_root_extra_files(fgmod_path, variant_id)
-        return variant_id
-
-    def _detect_fsr4_variant(self, directory: Path, upscaler_sha256: str | None) -> str | None:
-        for variant_id, variant in FSR4_VARIANTS.items():
-            extra_files = list(variant.get("extra_files") or [])
-            if not extra_files:
-                continue
-            if not upscaler_sha256 or str(variant.get("sha256") or "").lower() != str(upscaler_sha256).lower():
-                continue
-            all_match = True
-            for extra_file in extra_files:
-                file_path = directory / extra_file["name"]
-                if not file_path.exists() or self._file_sha256(file_path).lower() != extra_file["sha256"].lower():
-                    all_match = False
-                    break
-            if all_match:
-                return variant_id
-
-        if not upscaler_sha256:
-            return None
-        normalized_sha = str(upscaler_sha256).lower()
-        for variant_id, variant in FSR4_VARIANTS.items():
-            if variant.get("extra_files"):
-                continue
-            if str(variant.get("sha256") or "").lower() == normalized_sha:
-                return variant_id
-        return None
-
-    def _fgmod_version(self, fgmod_path: Path) -> str | None:
-        manifest = self._load_install_manifest(fgmod_path)
-        optiscaler = manifest.get("optiscaler") if isinstance(manifest, dict) else None
-        if isinstance(optiscaler, dict) and optiscaler.get("version"):
-            return str(optiscaler.get("version"))
-        version_file = fgmod_path / VERSION_FILENAME
-        try:
-            if version_file.exists():
-                return version_file.read_text(encoding="utf-8").strip() or None
-        except Exception:
-            return None
-        return None
-
-    def _managed_support_candidate_paths(self, fgmod_path: Path, filename: str) -> list[Path]:
-        candidates: list[Path] = []
-        if filename == FSR4_UPSCALER_FILENAME:
-            candidates.append(fgmod_path / FSR4_UPSCALER_FILENAME)
-            for variant_id in FSR4_VARIANTS:
-                candidates.append(self._fsr4_variant_path(fgmod_path, variant_id))
-        else:
-            candidates.append(fgmod_path / filename)
-            for variant_id in FSR4_VARIANTS:
-                for extra_file in self._fsr4_variant_extra_files(variant_id):
-                    if extra_file["name"] == filename:
-                        candidates.append(self._fsr4_variant_extra_file_path(fgmod_path, variant_id, filename))
-        unique: list[Path] = []
-        seen: set[str] = set()
-        for candidate in candidates:
-            key = str(candidate)
-            if key not in seen:
-                unique.append(candidate)
-                seen.add(key)
-        return unique
-
-    def _is_managed_support_file(self, path: Path, fgmod_path: Path) -> bool:
-        if not path.exists():
-            return False
-        for candidate in self._managed_support_candidate_paths(fgmod_path, path.name):
-            if self._files_match(path, candidate):
-                return True
-        return False
-
-    def _migrate_optiscaler_ini(self, ini_file):
-        """Migrate pre-v0.9-final OptiScaler.ini: replace FGType with FGInput + FGOutput.
-
-        v0.9-final split the single FGType key into separate FGInput and FGOutput keys.
-        Games already patched with an older build will have FGType=<value> in their
-        per-game INI but no FGInput/FGOutput entries, causing the new DLL to silently
-        fall back to nofg.  This migration runs at patch-time and at every fgmod.sh
-        launch so users never have to manually touch their INI.
-        """
-        try:
-            if not ini_file.exists():
-                return False
-
-            with open(ini_file, 'r') as f:
-                content = f.read()
-
-            fg_type_match = re.search(r'^FGType\s*=\s*(\S+)', content, re.MULTILINE)
-            if not fg_type_match:
-                return True  # Nothing to migrate
-
-            fg_value = fg_type_match.group(1)
-
-            if re.search(r'^FGInput\s*=', content, re.MULTILINE):
-                # FGInput already present (INI already in v0.9-final format);
-                # just remove the now-unknown FGType line.
-                content = re.sub(r'^FGType\s*=\s*\S+\n?', '', content, flags=re.MULTILINE)
-                decky.logger.info(f"Removed stale FGType from {ini_file} (FGInput already present)")
-            else:
-                # Replace the single FGType=X line with FGInput=X then FGOutput=X
-                content = re.sub(
-                    r'^FGType\s*=\s*\S+',
-                    f'FGInput={fg_value}\nFGOutput={fg_value}',
-                    content,
-                    flags=re.MULTILINE
-                )
-                decky.logger.info(f"Migrated FGType={fg_value} → FGInput={fg_value}, FGOutput={fg_value} in {ini_file}")
-
-            with open(ini_file, 'w') as f:
-                f.write(content)
-            return True
-        except Exception as e:
-            decky.logger.error(f"Failed to migrate OptiScaler.ini: {e}")
-            return False
-
-    def _disable_hq_font_auto(self, ini_file):
-        """Disable the new HQ font auto mode to avoid missing font assertions on Wine/Proton."""
-        try:
-            if not ini_file.exists():
-                decky.logger.warning(f"OptiScaler.ini not found at {ini_file}")
-                return False
-
-            with open(ini_file, 'r') as f:
-                content = f.read()
-
-            updated_content = re.sub(r'UseHQFont\s*=\s*auto', 'UseHQFont=false', content)
-            if updated_content != content:
-                with open(ini_file, 'w') as f:
-                    f.write(updated_content)
-                decky.logger.info("Set UseHQFont=false to avoid missing font assertions")
-
-            return True
-        except Exception as e:
-            decky.logger.error(f"Failed to update HQ font setting in OptiScaler.ini: {e}")
-            return False
-
-    def _modify_optiscaler_ini(self, ini_file):
-        """Modify OptiScaler.ini to set FG defaults, ASI plugin settings, and safe font defaults."""
-        try:
-            if ini_file.exists():
-                with open(ini_file, 'r') as f:
-                    content = f.read()
-                
-                # Replace FGInput=auto with FGInput=nukems (final v0.9+ split FGType into FGInput/FGOutput)
-                updated_content = re.sub(r'FGInput\s*=\s*auto', 'FGInput=nukems', content)
-
-                # Replace FGOutput=auto with FGOutput=nukems
-                updated_content = re.sub(r'FGOutput\s*=\s*auto', 'FGOutput=nukems', updated_content)
-                
-                # Replace Fsr4Update=auto with Fsr4Update=true
-                updated_content = re.sub(r'Fsr4Update\s*=\s*auto', 'Fsr4Update=true', updated_content)
-                
-                # Replace LoadAsiPlugins=auto with LoadAsiPlugins=true
-                updated_content = re.sub(r'LoadAsiPlugins\s*=\s*auto', 'LoadAsiPlugins=true', updated_content)
-
-                # Disable new HQ font auto mode to avoid missing font assertions on Proton
-                updated_content = re.sub(r'UseHQFont\s*=\s*auto', 'UseHQFont=false', updated_content)
-                
-                with open(ini_file, 'w') as f:
-                    f.write(updated_content)
-                
-                decky.logger.info("Modified OptiScaler.ini to set FGInput=nukems, FGOutput=nukems, Fsr4Update=true, LoadAsiPlugins=true, UseHQFont=false")
-                return True
-            else:
-                decky.logger.warning(f"OptiScaler.ini not found at {ini_file}")
-                return False
-        except Exception as e:
-            decky.logger.error(f"Failed to modify OptiScaler.ini: {e}")
-            return False
-
-    async def extract_static_optiscaler(self, selected_default_variant: str = DEFAULT_FSR4_VARIANT) -> dict:
-        """Prepare the shared ~/fgmod bundle with all bundled FSR4 runtime variants."""
-        try:
-            decky.logger.info("Starting extract_static_optiscaler method")
-
-            bin_path = Path(decky.DECKY_PLUGIN_DIR) / "bin"
-            extract_path = Path(decky.HOME) / "fgmod"
-            assets_dir = Path(decky.DECKY_PLUGIN_DIR) / "assets"
-            selected_default_variant = self._normalize_fsr4_variant(selected_default_variant)
-
-            if not bin_path.exists():
-                return {"status": "error", "message": f"Bin directory not found: {bin_path}"}
-
-            optiscaler_archive = bin_path / OPTISCALER_ARCHIVE_ASSET["name"]
-            fsr4_int8_src = bin_path / FSR4_INT8_ASSET["name"]
-            fsr4_official_411_src = bin_path / FSR4_OFFICIAL_411_ASSET["name"]
-            fsr4_valve_411_src = bin_path / FSR4_VALVE_411_ASSET["name"]
-            amdxc64_rdna2_src = bin_path / AMDXC64_RDNA2_ASSET["name"]
-            optiscaler_pre10_src = bin_path / OPTISCALER_PRE10_ASSET["name"]
-            optipatcher_src = bin_path / OPTIPATCHER_ASSET["name"]
-            for required_path, asset in [
-                (optiscaler_archive, OPTISCALER_ARCHIVE_ASSET),
-                (fsr4_int8_src, FSR4_INT8_ASSET),
-                (fsr4_official_411_src, FSR4_OFFICIAL_411_ASSET),
-                (fsr4_valve_411_src, FSR4_VALVE_411_ASSET),
-                (amdxc64_rdna2_src, AMDXC64_RDNA2_ASSET),
-                (optiscaler_pre10_src, OPTISCALER_PRE10_ASSET),
-                (optipatcher_src, OPTIPATCHER_ASSET),
-            ]:
-                if not required_path.exists():
-                    return {
-                        "status": "error",
-                        "message": f"Required bundled asset missing: {asset['name']}",
-                    }
-                self._verify_bundled_asset(required_path, asset["sha256"], asset["name"])
-
-            if extract_path.exists():
-                shutil.rmtree(extract_path)
-            extract_path.mkdir(parents=True, exist_ok=True)
-
-            self._extract_archive(optiscaler_archive, extract_path)
-
-            source_file = extract_path / "OptiScaler.dll"
-            renames_dir = extract_path / "renames"
-            if not self._create_renamed_copies(source_file, renames_dir):
-                return {"status": "error", "message": "Failed to prepare renamed OptiScaler proxies."}
-
-            if not self._copy_launcher_scripts(assets_dir, extract_path):
-                return {"status": "error", "message": "Failed to copy launcher scripts."}
-
-            plugins_dir = extract_path / "plugins"
-            plugins_dir.mkdir(parents=True, exist_ok=True)
-            optipatcher_dst = plugins_dir / "OptiPatcher.asi"
-            shutil.copy2(optipatcher_src, optipatcher_dst)
-            optipatcher_sha256 = self._verify_bundled_asset(
-                optipatcher_dst,
-                OPTIPATCHER_ASSET["sha256"],
-                "Prepared OptiPatcher plugin",
-            )
-
-            ini_file = extract_path / "OptiScaler.ini"
-            self._modify_optiscaler_ini(ini_file)
-
-            native_upscaler_root = extract_path / FSR4_UPSCALER_FILENAME
-            native_upscaler_sha256 = self._verify_bundled_asset(
-                native_upscaler_root,
-                FSR4_VARIANTS["rdna4-native"]["sha256"],
-                "Archive-native FSR4 upscaler",
-            )
 
-            rdna4_dir = extract_path / FSR4_VARIANTS["rdna4-native"]["dir_name"]
-            rdna4_dir.mkdir(parents=True, exist_ok=True)
-            rdna4_upscaler = rdna4_dir / FSR4_UPSCALER_FILENAME
-            shutil.copy2(native_upscaler_root, rdna4_upscaler)
-            self._verify_bundled_asset(
-                rdna4_upscaler,
-                FSR4_VARIANTS["rdna4-native"]["sha256"],
-                "Prepared rdna4-native FSR4 upscaler",
-            )
-
-            official_411_dir = extract_path / FSR4_VARIANTS["rdna34-official-411"]["dir_name"]
-            official_411_dir.mkdir(parents=True, exist_ok=True)
-            official_411_upscaler = official_411_dir / FSR4_UPSCALER_FILENAME
-            shutil.copy2(native_upscaler_root, official_411_upscaler)
-            self._verify_bundled_asset(
-                official_411_upscaler,
-                FSR4_VARIANTS["rdna34-official-411"]["sha256"],
-                "Prepared rdna34-official-411 FSR4 upscaler",
-            )
-            self._verify_bundled_asset(
-                fsr4_official_411_src,
-                FSR4_OFFICIAL_411_ASSET["sha256"],
-                "Bundled rdna34-official-411 driver override",
-            )
-            official_411_driver = official_411_dir / FSR4_DRIVER_OVERRIDE_FILENAME
-            shutil.copy2(fsr4_official_411_src, official_411_driver)
-            self._verify_bundled_asset(
-                official_411_driver,
-                FSR4_OFFICIAL_411_ASSET["sha256"],
-                "Prepared rdna34-official-411 driver override",
-            )
-
-            rdna2_valve_dir = extract_path / FSR4_VARIANTS["rdna2-valve-411-pre10"]["dir_name"]
-            rdna2_valve_dir.mkdir(parents=True, exist_ok=True)
-            rdna2_valve_upscaler = rdna2_valve_dir / FSR4_UPSCALER_FILENAME
-            shutil.copy2(native_upscaler_root, rdna2_valve_upscaler)
-            self._verify_bundled_asset(
-                rdna2_valve_upscaler,
-                FSR4_VARIANTS["rdna2-valve-411-pre10"]["sha256"],
-                "Prepared rdna2-valve-411-pre10 FSR4 upscaler",
-            )
-            self._verify_bundled_asset(
-                fsr4_valve_411_src,
-                FSR4_VALVE_411_ASSET["sha256"],
-                "Bundled rdna2-valve-411-pre10 driver override",
-            )
-            rdna2_valve_driver = rdna2_valve_dir / FSR4_DRIVER_OVERRIDE_FILENAME
-            shutil.copy2(fsr4_valve_411_src, rdna2_valve_driver)
-            self._verify_bundled_asset(
-                rdna2_valve_driver,
-                FSR4_VALVE_411_ASSET["sha256"],
-                "Prepared rdna2-valve-411-pre10 driver override",
-            )
-            self._verify_bundled_asset(
-                amdxc64_rdna2_src,
-                AMDXC64_RDNA2_ASSET["sha256"],
-                "Bundled rdna2-valve-411-pre10 amdxc64 override",
-            )
-            rdna2_valve_amdxc64 = rdna2_valve_dir / "amdxc64.dll"
-            shutil.copy2(amdxc64_rdna2_src, rdna2_valve_amdxc64)
-            self._verify_bundled_asset(
-                rdna2_valve_amdxc64,
-                AMDXC64_RDNA2_ASSET["sha256"],
-                "Prepared rdna2-valve-411-pre10 amdxc64 override",
-            )
-            self._verify_bundled_asset(
-                optiscaler_pre10_src,
-                OPTISCALER_PRE10_ASSET["sha256"],
-                "Bundled rdna2-valve-411-pre10 OptiScaler injector",
-            )
-            rdna2_valve_injector = rdna2_valve_dir / "OptiScaler.dll"
-            shutil.copy2(optiscaler_pre10_src, rdna2_valve_injector)
-            self._verify_bundled_asset(
-                rdna2_valve_injector,
-                OPTISCALER_PRE10_ASSET["sha256"],
-                "Prepared rdna2-valve-411-pre10 OptiScaler injector",
-            )
-            if not self._create_renamed_copies(rdna2_valve_injector, rdna2_valve_dir / "renames"):
-                return {"status": "error", "message": "Failed to prepare renamed pre10 OptiScaler proxies."}
-
-            rdna23_dir = extract_path / FSR4_VARIANTS["rdna23-int8"]["dir_name"]
-            rdna23_dir.mkdir(parents=True, exist_ok=True)
-            self._verify_bundled_asset(
-                fsr4_int8_src,
-                FSR4_VARIANTS["rdna23-int8"]["sha256"],
-                "Bundled rdna23-int8 FSR4 upscaler",
-            )
-            shutil.copy2(fsr4_int8_src, rdna23_dir / FSR4_UPSCALER_FILENAME)
-            self._verify_bundled_asset(
-                rdna23_dir / FSR4_UPSCALER_FILENAME,
-                FSR4_VARIANTS["rdna23-int8"]["sha256"],
-                "Prepared rdna23-int8 FSR4 upscaler",
-            )
-
-            selected_default_variant = self._activate_default_fsr4_variant(extract_path, selected_default_variant)
-            active_upscaler_sha256 = self._file_sha256(extract_path / FSR4_UPSCALER_FILENAME)
-
-            version_file = extract_path / VERSION_FILENAME
-            version_file.write_text(OPTISCALER_ARCHIVE_ASSET["version"], encoding="utf-8")
-
-            install_manifest = {
-                "schema_version": 1,
-                "installed_at": datetime.now(timezone.utc).isoformat(),
-                "optiscaler": {
-                    "asset_name": OPTISCALER_ARCHIVE_ASSET["name"],
-                    "version": OPTISCALER_ARCHIVE_ASSET["version"],
-                    "sha256": OPTISCALER_ARCHIVE_ASSET["sha256"],
-                    "native_upscaler_sha256": native_upscaler_sha256,
-                },
-                "optipatcher": {
-                    "asset_name": OPTIPATCHER_ASSET["name"],
-                    "version": OPTIPATCHER_ASSET["version"],
-                    "sha256": optipatcher_sha256,
-                    "target_path": str(optipatcher_dst.relative_to(extract_path)),
-                },
-                "fsr4_variants": {
-                    variant_id: {
-                        "label": variant["label"],
-                        "dir_name": variant["dir_name"],
-                        "path": str((Path(variant["dir_name"]) / FSR4_UPSCALER_FILENAME).as_posix()),
-                        "sha256": variant["sha256"],
-                        "source_asset_name": variant["source_asset_name"],
-                        "source_version": variant["source_version"],
-                        "uses_archive_native": bool(variant["uses_archive_native"]),
-                        "injector": (
-                            {
-                                "name": variant["injector"]["name"],
-                                "sha256": variant["injector"]["sha256"],
-                                "source_asset_name": variant["injector"]["source_asset_name"],
-                                "source_version": variant["injector"]["source_version"],
-                                "path": str((Path(variant["dir_name"]) / variant["injector"]["name"]).as_posix()),
-                            }
-                            if isinstance(variant.get("injector"), dict)
-                            else None
-                        ),
-                        "config_overrides": dict(variant.get("config_overrides") or {}),
-                        "extra_files": [
-                            {
-                                "name": extra_file["name"],
-                                "sha256": extra_file["sha256"],
-                                "source_asset_name": extra_file["source_asset_name"],
-                                "source_version": extra_file["source_version"],
-                                "path": str((Path(variant["dir_name"]) / extra_file["name"]).as_posix()),
-                            }
-                            for extra_file in variant.get("extra_files", [])
-                        ],
-                    }
-                    for variant_id, variant in FSR4_VARIANTS.items()
-                },
-                "selected_default_variant": selected_default_variant,
-                "active_root_upscaler": {
-                    "path": FSR4_UPSCALER_FILENAME,
-                    "sha256": active_upscaler_sha256,
-                    "variant": selected_default_variant,
-                },
-            }
-            self._write_json_file(self._install_manifest_path(extract_path), install_manifest)
+    async def extract_static_optiscaler(
+        self,
+        selected_default_variant: str = DEFAULT_FSR4_VARIANT,
+        framegen_backend: str = DEFAULT_FRAMEGEN_BACKEND,
+    ) -> dict:
+        return self._bundle.extract_static_optiscaler(selected_default_variant, framegen_backend)
 
-            return {
-                "status": "success",
-                "message": f"Successfully extracted OptiScaler {OPTISCALER_ARCHIVE_ASSET['version']} to ~/fgmod",
-                "version": OPTISCALER_ARCHIVE_ASSET["version"],
-                "selected_default_variant": selected_default_variant,
-                "selected_default_variant_label": FSR4_VARIANTS[selected_default_variant]["label"],
-            }
-        except Exception as e:
-            decky.logger.error(f"Extract failed with exception: {str(e)}")
-            import traceback
-            decky.logger.error(f"Traceback: {traceback.format_exc()}")
-            return {"status": "error", "message": f"Extract failed: {str(e)}"}
+    async def run_install_fgmod(
+        self,
+        selected_default_variant: str = DEFAULT_FSR4_VARIANT,
+        framegen_backend: str = DEFAULT_FRAMEGEN_BACKEND,
+    ) -> dict:
+        return self._bundle.run_install(selected_default_variant, framegen_backend)
 
     async def run_uninstall_fgmod(self) -> dict:
-        try:
-            # Remove fgmod directory
-            fgmod_path = Path(decky.HOME) / "fgmod"
-            
-            if fgmod_path.exists():
-                shutil.rmtree(fgmod_path)
-                decky.logger.info(f"Removed directory: {fgmod_path}")
-                return {
-                    "status": "success", 
-                    "output": "Successfully removed fgmod directory"
-                }
-            else:
-                return {
-                    "status": "success", 
-                    "output": "No fgmod directory found to remove"
-                }
-            
-        except Exception as e:
-            decky.logger.error(f"Uninstall error: {str(e)}")
-            return {
-                "status": "error", 
-                "message": f"Uninstall failed: {str(e)}", 
-                "output": str(e)
-            }
+        return self._bundle.uninstall()
 
     async def set_default_fsr4_variant(self, selected_default_variant: str = DEFAULT_FSR4_VARIANT) -> dict:
-        try:
-            fgmod_path = Path(decky.HOME) / "fgmod"
-            if not fgmod_path.exists():
-                return {"status": "error", "message": "OptiScaler bundle not installed. Run Install first."}
-
-            selected_default_variant = self._normalize_fsr4_variant(selected_default_variant)
-            manifest = self._load_install_manifest(fgmod_path)
-            if not manifest:
-                return {"status": "error", "message": "Install manifest missing. Reinstall OptiScaler."}
+        return self._bundle.set_default_variant(selected_default_variant)
 
-            selected_default_variant = self._activate_default_fsr4_variant(fgmod_path, selected_default_variant)
-            active_upscaler_sha256 = self._file_sha256(fgmod_path / FSR4_UPSCALER_FILENAME)
-            manifest["selected_default_variant"] = selected_default_variant
-            manifest["active_root_upscaler"] = {
-                "path": FSR4_UPSCALER_FILENAME,
-                "sha256": active_upscaler_sha256,
-                "variant": selected_default_variant,
-            }
-            manifest["updated_at"] = datetime.now(timezone.utc).isoformat()
-            self._write_json_file(self._install_manifest_path(fgmod_path), manifest)
-            return {
-                "status": "success",
-                "output": f"Default FSR4 runtime switched to {FSR4_VARIANTS[selected_default_variant]['label']}.",
-                "version": self._fgmod_version(fgmod_path),
-                "selected_default_variant": selected_default_variant,
-                "selected_default_variant_label": FSR4_VARIANTS[selected_default_variant]["label"],
-            }
-        except Exception as e:
-            decky.logger.error(f"Failed to switch default FSR4 runtime: {e}")
-            return {"status": "error", "message": f"Failed to switch default FSR4 runtime: {e}"}
-
-    async def run_install_fgmod(self, selected_default_variant: str = DEFAULT_FSR4_VARIANT) -> dict:
-        try:
-            decky.logger.info("Starting OptiScaler installation from static bundle")
-            selected_default_variant = self._normalize_fsr4_variant(selected_default_variant)
-
-            extract_result = await self.extract_static_optiscaler(selected_default_variant)
-            if extract_result["status"] != "success":
-                return {
-                    "status": "error",
-                    "message": f"OptiScaler extraction failed: {extract_result.get('message', 'Unknown error')}"
-                }
-
-            return {
-                "status": "success",
-                "output": (
-                    "Successfully installed OptiScaler "
-                    f"{extract_result.get('version', OPTISCALER_ARCHIVE_ASSET['version'])} "
-                    f"with {extract_result.get('selected_default_variant_label', FSR4_VARIANTS[selected_default_variant]['label'])}."
-                ),
-                "version": extract_result.get("version", OPTISCALER_ARCHIVE_ASSET["version"]),
-                "selected_default_variant": extract_result.get("selected_default_variant", selected_default_variant),
-                "selected_default_variant_label": extract_result.get(
-                    "selected_default_variant_label",
-                    FSR4_VARIANTS[selected_default_variant]["label"],
-                ),
-            }
-
-        except Exception as e:
-            decky.logger.error(f"Unexpected error during installation: {str(e)}")
-            return {
-                "status": "error",
-                "message": f"Installation failed: {str(e)}"
-            }
+    async def set_framegen_backend(self, framegen_backend: str = DEFAULT_FRAMEGEN_BACKEND) -> dict:
+        return self._bundle.set_framegen_backend(framegen_backend)
 
     async def check_fgmod_path(self) -> dict:
-        path = Path(decky.HOME) / "fgmod"
-        required_files = [
-            "OptiScaler.dll",
-            "OptiScaler.ini",
-            "dlssg_to_fsr3_amd_is_better.dll",
-            "fakenvapi.dll",
-            "fakenvapi.ini",
-            "amd_fidelityfx_dx12.dll",
-            "amd_fidelityfx_framegeneration_dx12.dll",
-            FSR4_UPSCALER_FILENAME,
-            "amd_fidelityfx_vk.dll",
-            "libxess.dll",
-            "libxess_dx11.dll",
-            "libxess_fg.dll",
-            "libxell.dll",
-            "fgmod",
-            "fgmod-uninstaller.sh",
-            "update-optiscaler-config.py",
-            INSTALL_MANIFEST_FILENAME,
-        ]
-
-        if not path.exists():
-            return {"exists": False}
-
-        for file_name in required_files:
-            if not path.joinpath(file_name).exists():
-                return {"exists": False}
-
-        plugins_dir = path / "plugins"
-        if not plugins_dir.exists() or not (plugins_dir / "OptiPatcher.asi").exists():
-            return {"exists": False}
-
-        for variant_id, variant in FSR4_VARIANTS.items():
-            variant_dir = path / variant["dir_name"]
-            variant_path = variant_dir / FSR4_UPSCALER_FILENAME
-            if not variant_path.exists():
-                return {"exists": False}
-            injector = variant.get("injector")
-            if isinstance(injector, dict):
-                if not (variant_dir / injector.get("name", "OptiScaler.dll")).exists():
-                    return {"exists": False}
-                if not (variant_dir / "renames" / "dxgi.dll").exists():
-                    return {"exists": False}
-            for extra_file in variant.get("extra_files", []):
-                if not (variant_dir / extra_file["name"]).exists():
-                    return {"exists": False}
-
-        manifest = self._load_install_manifest(path)
-        selected_variant = self._selected_fsr4_variant(path)
-        return {
-            "exists": True,
-            "version": self._fgmod_version(path),
-            "selected_fsr4_variant": selected_variant,
-            "selected_fsr4_variant_label": FSR4_VARIANTS[selected_variant]["label"],
-            "install_manifest_present": bool(manifest),
-        }
-
-    def _resolve_target_directory(self, directory: str) -> Path:
-        decky.logger.info(f"Resolving target directory: {directory}")
-        target = Path(directory).expanduser()
-        if not target.exists():
-            raise FileNotFoundError(f"Target directory does not exist: {directory}")
-        if not target.is_dir():
-            raise NotADirectoryError(f"Target path is not a directory: {directory}")
-        if not os.access(target, os.W_OK | os.X_OK):
-            raise PermissionError(f"Insufficient permissions for {directory}")
-        decky.logger.info(f"Resolved directory {directory} to absolute path {target}")
-        return target
-
-    def _manual_patch_directory_impl(
-        self,
-        directory: Path,
-        dll_name: str = "dxgi.dll",
-        fsr4_variant: str | None = None,
-        allow_managed_support_cleanup: bool = False,
-    ) -> dict:
-        fgmod_path = Path(decky.HOME) / "fgmod"
-        if not fgmod_path.exists():
-            return {
-                "status": "error",
-                "message": "OptiScaler bundle not installed. Run Install first.",
-            }
-
-        optiscaler_dll = fgmod_path / "OptiScaler.dll"
-        if not optiscaler_dll.exists():
-            return {
-                "status": "error",
-                "message": "OptiScaler.dll not found in ~/fgmod. Reinstall OptiScaler.",
-            }
-
-        preserve_ini = True
-        previous_marker_metadata = self._read_marker(directory / MARKER_FILENAME)
-        previous_variant = str(previous_marker_metadata.get("fsr4_variant") or "").strip()
-        selected_variant = self._selected_fsr4_variant(fgmod_path, fsr4_variant)
-        selected_variant_info = FSR4_VARIANTS[selected_variant]
-        selected_config_overrides = self._fsr4_variant_config_overrides(selected_variant)
-        if previous_variant == "rdna2-valve-411-pre10" and selected_variant != previous_variant:
-            selected_config_overrides.setdefault("FSR.Fsr4ForceModel", "auto")
-            selected_config_overrides.setdefault("Plugins.LoadCustomAmdxc64OnRdna2", "false")
-        selected_upscaler_src = self._fsr4_variant_path(fgmod_path, selected_variant)
-        if not selected_upscaler_src.exists():
-            selected_upscaler_src = fgmod_path / FSR4_UPSCALER_FILENAME
-        if not selected_upscaler_src.exists():
-            return {
-                "status": "error",
-                "message": f"FSR4 upscaler variant not found for {selected_variant}. Reinstall OptiScaler.",
-            }
-        selected_extra_files = self._fsr4_variant_extra_files(selected_variant)
-        optiscaler_version = self._fgmod_version(fgmod_path)
-        selected_upscaler_sha256 = self._file_sha256(selected_upscaler_src)
-
-        try:
-            decky.logger.info(
-                f"Manual patch started for {directory} with FSR4 variant {selected_variant} ({selected_variant_info['label']})"
-            )
-
-            backed_up_proxies = self._backup_preexisting_proxy_files(directory, fgmod_path)
-            decky.logger.info(
-                f"Backed up pre-existing proxy files: {backed_up_proxies}"
-                if backed_up_proxies
-                else "No pre-existing proxy files required backup"
-            )
-
-            removed_patch_files = []
-            for filename in dict.fromkeys(PATCH_CLEANUP_FILES):
-                path = directory / filename
-                if path.exists():
-                    path.unlink()
-                    removed_patch_files.append(filename)
-            decky.logger.info(
-                f"Removed stale patch files: {removed_patch_files}"
-                if removed_patch_files
-                else "No stale patch files found to remove"
-            )
-
-            backed_up_originals = []
-            removed_managed_support = []
-            for dll in ORIGINAL_DLL_BACKUPS:
-                source = directory / dll
-                backup = directory / f"{dll}.b"
-                if not source.exists() or backup.exists():
-                    continue
-                if allow_managed_support_cleanup and self._is_managed_support_file(source, fgmod_path):
-                    source.unlink()
-                    removed_managed_support.append(dll)
-                    continue
-                shutil.move(source, backup)
-                backed_up_originals.append(dll)
-            if removed_managed_support:
-                decky.logger.info(f"Removed managed support files before repatch: {removed_managed_support}")
-            decky.logger.info(
-                f"Backed up original game DLLs: {backed_up_originals}"
-                if backed_up_originals
-                else "No original game DLLs required backup"
-            )
-
-            variant_renamed = self._fsr4_variant_renamed_proxy_path(fgmod_path, selected_variant, dll_name)
-            variant_injector = self._fsr4_variant_injector_path(fgmod_path, selected_variant)
-            root_renamed = fgmod_path / "renames" / dll_name
-            destination_dll = directory / dll_name
-            if variant_renamed and variant_renamed.exists():
-                source_for_copy = variant_renamed
-            elif variant_injector and variant_injector.exists():
-                source_for_copy = variant_injector
-            elif root_renamed.exists():
-                source_for_copy = root_renamed
-            else:
-                source_for_copy = optiscaler_dll
-            shutil.copy2(source_for_copy, destination_dll)
-            decky.logger.info(f"Copied injector DLL from {source_for_copy} to {destination_dll}")
-
-            target_ini = directory / "OptiScaler.ini"
-            source_ini = fgmod_path / "OptiScaler.ini"
-            if preserve_ini and target_ini.exists():
-                decky.logger.info(f"Preserving existing OptiScaler.ini at {target_ini}")
-            elif source_ini.exists():
-                shutil.copy2(source_ini, target_ini)
-                decky.logger.info(f"Copied OptiScaler.ini from {source_ini} to {target_ini}")
-            else:
-                decky.logger.warning("No OptiScaler.ini found to copy")
-
-            if target_ini.exists():
-                self._migrate_optiscaler_ini(target_ini)
-                self._disable_hq_font_auto(target_ini)
-                self._apply_optiscaler_ini_overrides(target_ini, selected_config_overrides)
-
-            plugins_src = fgmod_path / "plugins"
-            plugins_dest = directory / "plugins"
-            if plugins_src.exists():
-                shutil.copytree(plugins_src, plugins_dest, dirs_exist_ok=True)
-                decky.logger.info(f"Synced plugins directory from {plugins_src} to {plugins_dest}")
-            else:
-                decky.logger.warning("Plugins directory missing in fgmod bundle")
-
-            d3d12_src = fgmod_path / "D3D12_Optiscaler"
-            d3d12_dest = directory / "D3D12_Optiscaler"
-            if d3d12_src.exists():
-                shutil.copytree(d3d12_src, d3d12_dest, dirs_exist_ok=True)
-                decky.logger.info(f"Copied D3D12_Optiscaler directory to {d3d12_dest}")
-            else:
-                decky.logger.warning("D3D12_Optiscaler directory missing in fgmod bundle")
-
-            copied_support = []
-            missing_support = []
-            for filename in SUPPORT_FILES:
-                source = fgmod_path / filename
-                dest = directory / filename
-                if source.exists():
-                    shutil.copy2(source, dest)
-                    copied_support.append(filename)
-                else:
-                    missing_support.append(filename)
-
-            upscaler_dest = directory / FSR4_UPSCALER_FILENAME
-            shutil.copy2(selected_upscaler_src, upscaler_dest)
-            copied_support.append(FSR4_UPSCALER_FILENAME)
-
-            for extra_file in selected_extra_files:
-                source = self._fsr4_variant_extra_file_path(fgmod_path, selected_variant, extra_file["name"])
-                dest = directory / extra_file["name"]
-                if source.exists():
-                    shutil.copy2(source, dest)
-                    copied_support.append(extra_file["name"])
-                else:
-                    missing_support.append(extra_file["name"])
-
-            if copied_support:
-                decky.logger.info(f"Copied support files: {copied_support}")
-            if missing_support:
-                decky.logger.warning(f"Support files missing from fgmod bundle: {missing_support}")
-
-            decky.logger.info(f"Manual patch complete for {directory}")
-            return {
-                "status": "success",
-                "message": (
-                    f"OptiScaler files copied to {directory} using "
-                    f"{selected_variant_info['label']}"
-                ),
-                "fsr4_variant": selected_variant,
-                "fsr4_variant_label": selected_variant_info["label"],
-                "fsr4_upscaler_sha256": selected_upscaler_sha256,
-                "optiscaler_version": optiscaler_version,
-            }
-
-        except PermissionError as exc:
-            decky.logger.error(f"Manual patch permission error: {exc}")
-            return {
-                "status": "error",
-                "message": f"Permission error while patching: {exc}",
-            }
-        except Exception as exc:
-            decky.logger.error(f"Manual patch failed: {exc}")
-            return {
-                "status": "error",
-                "message": f"Manual patch failed: {exc}",
-            }
-
-    def _manual_unpatch_directory_impl(self, directory: Path) -> dict:
-        try:
-            decky.logger.info(f"Manual unpatch started for {directory}")
-
-            removed_files = []
-            for filename in set(INJECTOR_FILENAMES + SUPPORT_FILES + VARIANT_EXTRA_FILENAMES + [FSR4_UPSCALER_FILENAME]):
-                path = directory / filename
-                if path.exists():
-                    path.unlink()
-                    removed_files.append(filename)
-            decky.logger.info(f"Removed injector/support files: {removed_files}" if removed_files else "No injector/support files found to remove")
-
-            legacy_removed = []
-            for legacy in LEGACY_FILES:
-                path = directory / legacy
-                if path.exists():
-                    try:
-                        path.unlink()
-                    except IsADirectoryError:
-                        shutil.rmtree(path, ignore_errors=True)
-                    legacy_removed.append(legacy)
-            decky.logger.info(f"Removed legacy artifacts: {legacy_removed}" if legacy_removed else "No legacy artifacts present")
-
-            plugins_dir = directory / "plugins"
-            if plugins_dir.exists():
-                shutil.rmtree(plugins_dir, ignore_errors=True)
-                decky.logger.info(f"Removed plugins directory at {plugins_dir}")
-
-            d3d12_dir = directory / "D3D12_Optiscaler"
-            if d3d12_dir.exists():
-                shutil.rmtree(d3d12_dir, ignore_errors=True)
-                decky.logger.info(f"Removed D3D12_Optiscaler directory from {d3d12_dir}")
-
-            restored_backups = []
-            for dll in dict.fromkeys(RESTORABLE_BACKUP_FILES):
-                backup = directory / f"{dll}.b"
-                original = directory / dll
-                if backup.exists():
-                    if original.exists():
-                        original.unlink()
-                    shutil.move(backup, original)
-                    restored_backups.append(dll)
-            decky.logger.info(f"Restored backups: {restored_backups}" if restored_backups else "No backups found to restore")
-
-            uninstaller = directory / "fgmod-uninstaller.sh"
-            if uninstaller.exists():
-                uninstaller.unlink()
-                decky.logger.info(f"Removed fgmod uninstaller at {uninstaller}")
-
-            decky.logger.info(f"Manual unpatch complete for {directory}")
-            return {
-                "status": "success",
-                "message": f"OptiScaler files removed from {directory}",
-            }
-
-        except PermissionError as exc:
-            decky.logger.error(f"Manual unpatch permission error: {exc}")
-            return {
-                "status": "error",
-                "message": f"Permission error while unpatching: {exc}",
-            }
-        except Exception as exc:
-            decky.logger.error(f"Manual unpatch failed: {exc}")
-            return {
-                "status": "error",
-                "message": f"Manual unpatch failed: {exc}",
-            }
-
-    # ── Steam library discovery ───────────────────────────────────────────────
-
-    def _home_path(self) -> Path:
-        try:
-            return Path(decky.HOME)
-        except TypeError:
-            return Path(str(decky.HOME))
-
-    def _steam_root_candidates(self) -> list[Path]:
-        home = self._home_path()
-        candidates = [
-            home / ".local" / "share" / "Steam",
-            home / ".steam" / "steam",
-            home / ".steam" / "root",
-            home / ".var" / "app" / "com.valvesoftware.Steam" / "home" / ".local" / "share" / "Steam",
-            home / ".var" / "app" / "com.valvesoftware.Steam" / "home" / ".steam" / "steam",
-        ]
-        unique: list[Path] = []
-        seen: set[str] = set()
-        for c in candidates:
-            key = str(c)
-            if key not in seen:
-                unique.append(c)
-                seen.add(key)
-        return unique
-
-    def _steam_library_paths(self) -> list[Path]:
-        library_paths: list[Path] = []
-        seen: set[str] = set()
-        for steam_root in self._steam_root_candidates():
-            if steam_root.exists():
-                key = str(steam_root)
-                if key not in seen:
-                    library_paths.append(steam_root)
-                    seen.add(key)
-            library_file = steam_root / "steamapps" / "libraryfolders.vdf"
-            if not library_file.exists():
-                continue
-            try:
-                with open(library_file, "r", encoding="utf-8", errors="replace") as f:
-                    for line in f:
-                        if '"path"' not in line:
-                            continue
-                        path = line.split('"path"', 1)[1].strip().strip('"').replace("\\\\", "/")
-                        candidate = Path(path)
-                        key = str(candidate)
-                        if key not in seen:
-                            library_paths.append(candidate)
-                            seen.add(key)
-            except Exception as exc:
-                decky.logger.error(f"[Framegen] failed to parse libraryfolders: {library_file}: {exc}")
-        return library_paths
-
-    def _find_installed_games(self, appid: str | None = None) -> list[dict]:
-        games: list[dict] = []
-        for library_path in self._steam_library_paths():
-            steamapps_path = library_path / "steamapps"
-            if not steamapps_path.exists():
-                continue
-            for appmanifest in steamapps_path.glob("appmanifest_*.acf"):
-                game_info: dict = {"appid": "", "name": "", "library_path": str(library_path), "install_path": ""}
-                install_dir = ""
-                try:
-                    with open(appmanifest, "r", encoding="utf-8", errors="replace") as f:
-                        for line in f:
-                            if '"appid"' in line:
-                                game_info["appid"] = line.split('"appid"', 1)[1].strip().strip('"')
-                            elif '"name"' in line:
-                                game_info["name"] = line.split('"name"', 1)[1].strip().strip('"')
-                            elif '"installdir"' in line:
-                                install_dir = line.split('"installdir"', 1)[1].strip().strip('"')
-                except Exception as exc:
-                    decky.logger.error(f"[Framegen] skipping manifest {appmanifest}: {exc}")
-                    continue
-                if not game_info["appid"] or not game_info["name"]:
-                    continue
-                if "Proton" in game_info["name"] or "Steam Linux Runtime" in game_info["name"]:
-                    continue
-                install_path = steamapps_path / "common" / install_dir if install_dir else Path()
-                game_info["install_path"] = str(install_path)
-                if appid is None or str(game_info["appid"]) == str(appid):
-                    games.append(game_info)
-        deduped: dict[str, dict] = {}
-        for game in games:
-            deduped[str(game["appid"])] = game
-        return sorted(deduped.values(), key=lambda g: g["name"].lower())
-
-    def _game_record(self, appid: str) -> dict | None:
-        matches = self._find_installed_games(appid)
-        return matches[0] if matches else None
-
-    # ── Patch target auto-detection ───────────────────────────────────────────
-
-    def _normalized_path_string(self, value: str) -> str:
-        normalized = value.lower().replace("\\", "/")
-        normalized = normalized.replace("z:/", "/")
-        normalized = normalized.replace("//", "/")
-        return normalized
-
-    def _candidate_executables(self, install_root: Path) -> list[Path]:
-        if not install_root.exists():
-            return []
-        candidates: list[Path] = []
-        try:
-            for exe in install_root.rglob("*.exe"):
-                if exe.is_file():
-                    candidates.append(exe)
-        except Exception as exc:
-            decky.logger.error(f"[Framegen] exe scan failed for {install_root}: {exc}")
-        return candidates
-
-    def _exe_score(self, exe: Path, install_root: Path, game_name: str) -> int:
-        normalized = self._normalized_path_string(str(exe))
-        name = exe.name.lower()
-        score = 0
-        if normalized.endswith("-win64-shipping.exe"):
-            score += 300
-        if "shipping.exe" in name:
-            score += 220
-        if "/binaries/win64/" in normalized:
-            score += 200
-        if "/win64/" in normalized:
-            score += 80
-        if exe.parent == install_root:
-            score += 20
-        sanitized_game = re.sub(r"[^a-z0-9]", "", game_name.lower())
-        sanitized_name = re.sub(r"[^a-z0-9]", "", exe.stem.lower())
-        sanitized_root = re.sub(r"[^a-z0-9]", "", install_root.name.lower())
-        if sanitized_game and sanitized_game in sanitized_name:
-            score += 120
-        if sanitized_root and sanitized_root in sanitized_name:
-            score += 90
-        for bad in BAD_EXE_SUBSTRINGS:
-            if bad in normalized:
-                score -= 200
-        score -= len(exe.parts)
-        return score
-
-    def _best_running_executable(self, candidates: list[Path]) -> Path | None:
-        if not candidates:
-            return None
-        try:
-            result = subprocess.run(["ps", "-eo", "args="], capture_output=True, text=True, check=False)
-            process_lines = result.stdout.splitlines()
-        except Exception as exc:
-            decky.logger.error(f"[Framegen] running exe scan failed: {exc}")
-            return None
-        normalized_candidates = [(exe, self._normalized_path_string(str(exe))) for exe in candidates]
-        matches: list[tuple[int, Path]] = []
-        for line in process_lines:
-            normalized_line = self._normalized_path_string(line)
-            for exe, normalized_exe in normalized_candidates:
-                if normalized_exe in normalized_line:
-                    matches.append((len(normalized_exe), exe))
-        if not matches:
-            return None
-        matches.sort(key=lambda item: item[0], reverse=True)
-        return matches[0][1]
-
-    def _guess_patch_target(self, game_info: dict) -> tuple[Path, Path | None]:
-        install_root = Path(game_info["install_path"])
-        candidates = self._candidate_executables(install_root)
-        if not candidates:
-            return install_root, None
-        running_exe = self._best_running_executable(candidates)
-        if running_exe:
-            return running_exe.parent, running_exe
-        best = max(candidates, key=lambda exe: self._exe_score(exe, install_root, game_info["name"]))
-        return best.parent, best
-
-    def _is_game_running(self, game_info: dict) -> bool:
-        install_root = Path(game_info["install_path"])
-        candidates = self._candidate_executables(install_root)
-        return self._best_running_executable(candidates) is not None
-
-    # ── Marker file tracking ──────────────────────────────────────────────────
-
-    def _find_marker(self, install_root: Path) -> Path | None:
-        if not install_root.exists():
-            return None
-        try:
-            for marker in install_root.rglob(MARKER_FILENAME):
-                if marker.is_file():
-                    return marker
-        except Exception:
-            pass
-        return None
-
-    def _read_marker(self, marker_path: Path) -> dict:
-        try:
-            with open(marker_path, "r", encoding="utf-8") as f:
-                data = json.load(f)
-            return data if isinstance(data, dict) else {}
-        except Exception:
-            return {}
-
-    def _write_marker(
-        self,
-        marker_path: Path,
-        *,
-        appid: str,
-        game_name: str,
-        dll_name: str,
-        target_dir: Path,
-        original_launch_options: str,
-        backed_up_files: list[str],
-        optiscaler_version: str | None = None,
-        fsr4_variant: str | None = None,
-        fsr4_upscaler_sha256: str | None = None,
-    ) -> None:
-        normalized_variant = self._normalize_fsr4_variant(fsr4_variant)
-        variant_info = FSR4_VARIANTS[normalized_variant]
-        payload = {
-            "appid": str(appid),
-            "game_name": game_name,
-            "dll_name": dll_name,
-            "target_dir": str(target_dir),
-            "original_launch_options": original_launch_options,
-            "backed_up_files": backed_up_files,
-            "optiscaler_version": optiscaler_version,
-            "fsr4_variant": normalized_variant,
-            "fsr4_variant_label": variant_info["label"],
-            "fsr4_upscaler_sha256": fsr4_upscaler_sha256,
-            "managed_files": [
-                {
-                    "path": str(target_dir / FSR4_UPSCALER_FILENAME),
-                    "sha256": fsr4_upscaler_sha256,
-                    "kind": "fsr4-upscaler",
-                    "variant": normalized_variant,
-                }
-            ],
-            "patched_at": datetime.now(timezone.utc).isoformat(),
-        }
-        self._write_json_file(marker_path, payload)
-
-    # ── Launch options helpers ────────────────────────────────────────────────
-
-    def _build_managed_launch_options(self, dll_name: str) -> str:
-        if dll_name == "OptiScaler.asi":
-            return "SteamDeck=0 %command%"
-        base = dll_name.replace(".dll", "")
-        return f"WINEDLLOVERRIDES={base}=n,b SteamDeck=0 %command%"
-
-    def _is_managed_launch_options(self, opts: str) -> bool:
-        if not opts or not opts.strip():
-            return False
-        normalized = " ".join(opts.strip().split())
-        for dll_name in VALID_DLL_NAMES:
-            if dll_name == "OptiScaler.asi":
-                continue
-            base = dll_name.replace(".dll", "")
-            if f"WINEDLLOVERRIDES={base}=n,b" in normalized:
-                return True
-        if "fgmod/fgmod" in normalized:
-            return True
-        return False
+        return self._bundle.check()
 
     async def list_installed_games(self) -> dict:
-        try:
-            games = []
-            for game in self._find_installed_games():
-                install_root = Path(game["install_path"])
-                games.append({
-                    "appid": str(game["appid"]),
-                    "name": game["name"],
-                    "install_found": install_root.exists(),
-                })
-            return {"status": "success", "games": games}
-        except Exception as e:
-            decky.logger.error(str(e))
-            return {"status": "error", "message": str(e)}
+        return self._patcher.list_installed_games()
 
     async def get_path_defaults(self) -> dict:
-        try:
-            home_path = Path(decky.HOME)
-        except TypeError:
-            home_path = Path(str(decky.HOME))
-
-        steam_common = home_path / ".local" / "share" / "Steam" / "steamapps" / "common"
-
-        return {
-            "home": str(home_path),
-            "steam_common": str(steam_common),
-        }
+        return {"home": str(self._steam.home), "steam_common": str(self._steam.steam_common_path())}
 
     async def log_error(self, error: str) -> None:
         decky.logger.error(f"FRONTEND: {error}")
@@ -1667,109 +69,15 @@ class Plugin:
         directory: str,
         dll_name: str = "dxgi.dll",
         fsr4_variant: str = DEFAULT_FSR4_VARIANT,
+        framegen_backend: str = DEFAULT_FRAMEGEN_BACKEND,
     ) -> dict:
-        if dll_name not in VALID_DLL_NAMES:
-            return {"status": "error", "message": f"Invalid proxy DLL name: {dll_name}"}
-        try:
-            target_dir = self._resolve_target_directory(directory)
-        except (FileNotFoundError, NotADirectoryError, PermissionError) as exc:
-            decky.logger.error(f"Manual patch validation failed: {exc}")
-            return {"status": "error", "message": str(exc)}
-
-        allow_managed_support_cleanup = (target_dir / MARKER_FILENAME).exists()
-        return self._manual_patch_directory_impl(
-            target_dir,
-            dll_name,
-            fsr4_variant,
-            allow_managed_support_cleanup=allow_managed_support_cleanup,
-        )
+        return self._patcher.manual_patch_directory(directory, dll_name, fsr4_variant, framegen_backend)
 
     async def manual_unpatch_directory(self, directory: str) -> dict:
-        try:
-            target_dir = self._resolve_target_directory(directory)
-        except (FileNotFoundError, NotADirectoryError, PermissionError) as exc:
-            decky.logger.error(f"Manual unpatch validation failed: {exc}")
-            return {"status": "error", "message": str(exc)}
-
-        return self._manual_unpatch_directory_impl(target_dir)
-
-    # ── AppID-based patch / unpatch / status ───────────────────────────────────────
+        return self._patcher.manual_unpatch_directory(directory)
 
     async def get_game_status(self, appid: str) -> dict:
-        try:
-            game_info = self._game_record(str(appid))
-            if not game_info:
-                return {
-                    "status": "success",
-                    "appid": str(appid),
-                    "install_found": False,
-                    "patched": False,
-                    "dll_name": None,
-                    "target_dir": None,
-                    "fsr4_variant": None,
-                    "fsr4_variant_label": None,
-                    "message": "Game not found in Steam library.",
-                }
-            install_root = Path(game_info["install_path"])
-            if not install_root.exists():
-                return {
-                    "status": "success",
-                    "appid": str(appid),
-                    "name": game_info["name"],
-                    "install_found": False,
-                    "patched": False,
-                    "dll_name": None,
-                    "target_dir": None,
-                    "fsr4_variant": None,
-                    "fsr4_variant_label": None,
-                    "message": "Game install directory not found.",
-                }
-            marker = self._find_marker(install_root)
-            if not marker:
-                return {
-                    "status": "success",
-                    "appid": str(appid),
-                    "name": game_info["name"],
-                    "install_found": True,
-                    "patched": False,
-                    "dll_name": None,
-                    "target_dir": None,
-                    "fsr4_variant": None,
-                    "fsr4_variant_label": None,
-                    "message": "Not patched.",
-                }
-            metadata = self._read_marker(marker)
-            dll_name = metadata.get("dll_name", "dxgi.dll")
-            target_dir = Path(metadata.get("target_dir", str(marker.parent)))
-            dll_present = (target_dir / dll_name).exists()
-            upscaler_path = target_dir / FSR4_UPSCALER_FILENAME
-            upscaler_sha256 = self._file_sha256(upscaler_path) if upscaler_path.exists() else None
-            detected_variant = self._detect_fsr4_variant(target_dir, upscaler_sha256)
-            stored_variant = str(metadata.get("fsr4_variant") or "").strip() or None
-            effective_variant = detected_variant or (stored_variant if stored_variant in FSR4_VARIANTS else None)
-            effective_label = FSR4_VARIANTS[effective_variant]["label"] if effective_variant else None
-            return {
-                "status": "success",
-                "appid": str(appid),
-                "name": game_info["name"],
-                "install_found": True,
-                "patched": dll_present,
-                "dll_name": dll_name,
-                "target_dir": str(target_dir),
-                "patched_at": metadata.get("patched_at"),
-                "optiscaler_version": metadata.get("optiscaler_version"),
-                "fsr4_variant": effective_variant,
-                "fsr4_variant_label": effective_label,
-                "fsr4_upscaler_sha256": upscaler_sha256,
-                "message": (
-                    f"Patched using {dll_name}" + (f" with {effective_label}." if effective_label else ".")
-                    if dll_present
-                    else f"Marker found but {dll_name} is missing. Reinstall recommended."
-                ),
-            }
-        except Exception as exc:
-            decky.logger.error(f"[Framegen] get_game_status failed for {appid}: {exc}")
-            return {"status": "error", "message": str(exc)}
+        return self._patcher.get_game_status(appid)
 
     async def patch_game(
         self,
@@ -1777,137 +85,9 @@ class Plugin:
         dll_name: str = "dxgi.dll",
         current_launch_options: str = "",
         fsr4_variant: str = DEFAULT_FSR4_VARIANT,
+        framegen_backend: str = DEFAULT_FRAMEGEN_BACKEND,
     ) -> dict:
-        try:
-            if dll_name not in VALID_DLL_NAMES:
-                return {"status": "error", "message": f"Invalid proxy DLL name: {dll_name}"}
-            game_info = self._game_record(str(appid))
-            if not game_info:
-                return {"status": "error", "message": "Game not found in Steam library."}
-            install_root = Path(game_info["install_path"])
-            if not install_root.exists():
-                return {"status": "error", "message": "Game install directory does not exist."}
-            if self._is_game_running(game_info):
-                return {"status": "error", "message": "Close the game before patching."}
-            fgmod_path = Path(decky.HOME) / "fgmod"
-            if not fgmod_path.exists():
-                return {"status": "error", "message": "OptiScaler bundle not installed. Run Install first."}
-
-            # Preserve true original launch options across re-patches
-            original_launch_options = current_launch_options or ""
-            existing_marker = self._find_marker(install_root)
-            existing_marker_metadata = self._read_marker(existing_marker) if existing_marker else {}
-            existing_marker_target_dir = Path(
-                existing_marker_metadata.get("target_dir", str(existing_marker.parent))
-            ) if existing_marker else None
-            if existing_marker:
-                stored_opts = str(existing_marker_metadata.get("original_launch_options") or "")
-                if stored_opts and not self._is_managed_launch_options(stored_opts):
-                    original_launch_options = stored_opts
-            if self._is_managed_launch_options(original_launch_options):
-                original_launch_options = ""
-
-            # Auto-detect the right directory to patch
-            target_dir, target_exe = self._guess_patch_target(game_info)
-            decky.logger.info(f"[Framegen] patch_game: appid={appid} dll={dll_name} target={target_dir} exe={target_exe}")
-
-            allow_managed_support_cleanup = bool(
-                existing_marker and existing_marker_target_dir == target_dir
-            ) or (target_dir / MARKER_FILENAME).exists()
-            result = self._manual_patch_directory_impl(
-                target_dir,
-                dll_name,
-                fsr4_variant,
-                allow_managed_support_cleanup=allow_managed_support_cleanup,
-            )
-            if result["status"] != "success":
-                return result
-
-            backed_up = [dll for dll in dict.fromkeys(RESTORABLE_BACKUP_FILES) if (target_dir / f"{dll}.b").exists()]
-            marker_path = target_dir / MARKER_FILENAME
-            self._write_marker(
-                marker_path,
-                appid=str(appid),
-                game_name=game_info["name"],
-                dll_name=dll_name,
-                target_dir=target_dir,
-                original_launch_options=original_launch_options,
-                backed_up_files=backed_up,
-                optiscaler_version=result.get("optiscaler_version"),
-                fsr4_variant=result.get("fsr4_variant"),
-                fsr4_upscaler_sha256=result.get("fsr4_upscaler_sha256"),
-            )
-
-            if existing_marker and existing_marker != marker_path:
-                try:
-                    existing_marker.unlink()
-                except Exception:
-                    pass
-
-            managed_launch_options = self._build_managed_launch_options(dll_name)
-            decky.logger.info(f"[Framegen] patch_game success: appid={appid} launch_options={managed_launch_options}")
-            return {
-                "status": "success",
-                "appid": str(appid),
-                "name": game_info["name"],
-                "dll_name": dll_name,
-                "target_dir": str(target_dir),
-                "launch_options": managed_launch_options,
-                "original_launch_options": original_launch_options,
-                "optiscaler_version": result.get("optiscaler_version"),
-                "fsr4_variant": result.get("fsr4_variant"),
-                "fsr4_variant_label": result.get("fsr4_variant_label"),
-                "fsr4_upscaler_sha256": result.get("fsr4_upscaler_sha256"),
-                "message": (
-                    f"Patched {game_info['name']} using {dll_name} "
-                    f"with {result.get('fsr4_variant_label', FSR4_VARIANTS[self._normalize_fsr4_variant(fsr4_variant)]['label'])}."
-                ),
-            }
-        except Exception as exc:
-            decky.logger.error(f"[Framegen] patch_game failed for {appid}: {exc}")
-            return {"status": "error", "message": str(exc)}
+        return self._patcher.patch_game(appid, dll_name, current_launch_options, fsr4_variant, framegen_backend)
 
     async def unpatch_game(self, appid: str) -> dict:
-        try:
-            game_info = self._game_record(str(appid))
-            if not game_info:
-                return {"status": "error", "message": "Game not found in Steam library."}
-            install_root = Path(game_info["install_path"])
-            if not install_root.exists():
-                return {
-                    "status": "success",
-                    "appid": str(appid),
-                    "name": game_info["name"],
-                    "launch_options": "",
-                    "message": "Game install directory does not exist.",
-                }
-            if self._is_game_running(game_info):
-                return {"status": "error", "message": "Close the game before unpatching."}
-            marker = self._find_marker(install_root)
-            if not marker:
-                return {
-                    "status": "success",
-                    "appid": str(appid),
-                    "name": game_info["name"],
-                    "launch_options": "",
-                    "message": "No Framegen patch found for this game.",
-                }
-            metadata = self._read_marker(marker)
-            target_dir = Path(metadata.get("target_dir", str(marker.parent)))
-            original_launch_options = str(metadata.get("original_launch_options") or "")
-            self._manual_unpatch_directory_impl(target_dir)
-            try:
-                marker.unlink()
-            except FileNotFoundError:
-                pass
-            decky.logger.info(f"[Framegen] unpatch_game success: appid={appid} target={target_dir}")
-            return {
-                "status": "success",
-                "appid": str(appid),
-                "name": game_info["name"],
-                "launch_options": original_launch_options,
-                "message": f"Unpatched {game_info['name']}.",
-            }
-        except Exception as exc:
-            decky.logger.error(f"[Framegen] unpatch_game failed for {appid}: {exc}")
-            return {"status": "error", "message": str(exc)}
+        return self._patcher.unpatch_game(appid)
diff --git a/package.json b/package.json
index d0c04a4..8b982a0 100644
--- a/package.json
+++ b/package.json
@@ -6,7 +6,7 @@
   "scripts": {
     "build": "rollup -c",
     "watch": "rollup -c -w",
-    "test": "echo \"Error: no test specified\" && exit 1"
+    "test": "python3 -m unittest discover -s tests -v"
   },
   "repository": {
     "type": "git",
@@ -90,4 +90,3 @@
     }
   ]
 }
-
diff --git a/src/api/index.ts b/src/api/index.ts
index b1bf0b8..4dda43c 100644
--- a/src/api/index.ts
+++ b/src/api/index.ts
@@ -1,7 +1,7 @@
 import { callable } from "@decky/api";
 
 export const runInstallFGMod = callable<
-  [selected_default_variant?: string],
+  [selected_default_variant?: string, framegen_backend?: string],
   {
     status: string;
     message?: string;
@@ -9,6 +9,8 @@ export const runInstallFGMod = callable<
     version?: string;
     selected_default_variant?: string;
     selected_default_variant_label?: string;
+    framegen_backend?: string;
+    framegen_backend_label?: string;
   }
 >("run_install_fgmod");
 
@@ -29,6 +31,17 @@ export const setDefaultFsr4Variant = callable<
   }
 >("set_default_fsr4_variant");
 
+export const setFramegenBackend = callable<
+  [framegen_backend?: string],
+  {
+    status: string;
+    message?: string;
+    output?: string;
+    framegen_backend?: string;
+    framegen_backend_label?: string;
+  }
+>("set_framegen_backend");
+
 export const checkFGModPath = callable<
   [],
   {
@@ -36,6 +49,8 @@ export const checkFGModPath = callable<
     version?: string | null;
     selected_fsr4_variant?: string | null;
     selected_fsr4_variant_label?: string | null;
+    framegen_backend?: string | null;
+    framegen_backend_label?: string | null;
     install_manifest_present?: boolean;
   }
 >("check_fgmod_path");
@@ -53,7 +68,7 @@ export const getPathDefaults = callable<
 >("get_path_defaults");
 
 export const runManualPatch = callable<
-  [string, string, string],
+  [string, string, string, string],
   {
     status: string;
     message?: string;
@@ -62,6 +77,7 @@ export const runManualPatch = callable<
     fsr4_variant_label?: string;
     fsr4_upscaler_sha256?: string;
     optiscaler_version?: string | null;
+    framegen_backend?: string;
   }
 >("manual_patch_directory");
 
@@ -86,11 +102,13 @@ export const getGameStatus = callable<
     fsr4_variant?: string | null;
     fsr4_variant_label?: string | null;
     fsr4_upscaler_sha256?: string | null;
+    framegen_backend?: string | null;
+    framegen_backend_label?: string | null;
   }
 >("get_game_status");
 
 export const patchGame = callable<
-  [appid: string, dll_name: string, current_launch_options: string, fsr4_variant: string],
+  [appid: string, dll_name: string, current_launch_options: string, fsr4_variant: string, framegen_backend: string],
   {
     status: string;
     message?: string;
@@ -104,6 +122,7 @@ export const patchGame = callable<
     fsr4_variant?: string;
     fsr4_variant_label?: string;
     fsr4_upscaler_sha256?: string;
+    framegen_backend?: string;
   }
 >("patch_game");
 
diff --git a/src/components/CustomPathOverride.tsx b/src/components/CustomPathOverride.tsx
index af47735..fb7cd05 100644
--- a/src/components/CustomPathOverride.tsx
+++ b/src/components/CustomPathOverride.tsx
@@ -38,6 +38,7 @@ interface ManualPatchControlsProps {
   onManualModeChange?: (enabled: boolean) => void;
   dllName: string;
   fsr4Variant: string;
+  framegenBackend: string;
 }
 
 interface PickerState {
@@ -58,7 +59,7 @@ const formatResultMessage = (result: ApiResponse | null) => {
   return result.message || result.output || "Operation failed.";
 };
 
-export const ManualPatchControls = ({ isAvailable, onManualModeChange, dllName, fsr4Variant }: ManualPatchControlsProps) => {
+export const ManualPatchControls = ({ isAvailable, onManualModeChange, dllName, fsr4Variant, framegenBackend }: ManualPatchControlsProps) => {
   const [isEnabled, setEnabled] = useState(false);
   const [defaults, setDefaults] = useState<PathDefaults>(INITIAL_DEFAULTS);
   const [pickerState, setPickerState] = useState<PickerState>(INITIAL_PICKER_STATE);
@@ -160,14 +161,14 @@ export const ManualPatchControls = ({ isAvailable, onManualModeChange, dllName,
       if (!selectedPath) return;
 
       const setBusy = action === "patch" ? setIsPatching : setIsUnpatching;
-  setLastOperation(action);
+      setLastOperation(action);
       setBusy(true);
       setOperationResult(null);
 
       try {
         const response =
           action === "patch"
-            ? await runManualPatch(selectedPath, dllName, fsr4Variant)
+            ? await runManualPatch(selectedPath, dllName, fsr4Variant, framegenBackend)
             : await runManualUnpatch(selectedPath);
         setOperationResult(response ?? { status: "error", message: "No response from backend." });
       } catch (err) {
@@ -179,7 +180,7 @@ export const ManualPatchControls = ({ isAvailable, onManualModeChange, dllName,
         setBusy(false);
       }
     },
-    [selectedPath, dllName, fsr4Variant]
+    [selectedPath, dllName, fsr4Variant, framegenBackend]
   );
 
   const handleToggle = (value: boolean) => {
@@ -304,4 +305,4 @@ export const ManualPatchControls = ({ isAvailable, onManualModeChange, dllName,
       )}
     </>
   );
-};
\ No newline at end of file
+};
diff --git a/src/components/OptiScalerControls.tsx b/src/components/OptiScalerControls.tsx
index a8b0863..d6c4c77 100644
--- a/src/components/OptiScalerControls.tsx
+++ b/src/components/OptiScalerControls.tsx
@@ -1,9 +1,17 @@
 import { useState, useEffect } from "react";
 import { DropdownItem, Field, PanelSection, PanelSectionRow, ToggleField } from "@decky/ui";
-import { runInstallFGMod, runUninstallFGMod, setDefaultFsr4Variant } from "../api";
-import { OperationResult } from "./ResultDisplay";
+import { runInstallFGMod, runUninstallFGMod, setDefaultFsr4Variant, setFramegenBackend } from "../api";
+import { ResultDisplay, type OperationResult } from "./ResultDisplay";
 import { createAutoCleanupTimer } from "../utils";
-import { TIMEOUTS, PROXY_DLL_OPTIONS, DEFAULT_PROXY_DLL, FSR4_VARIANT_OPTIONS, DEFAULT_FSR4_VARIANT } from "../utils/constants";
+import {
+  TIMEOUTS,
+  PROXY_DLL_OPTIONS,
+  DEFAULT_PROXY_DLL,
+  FSR4_VARIANT_OPTIONS,
+  DEFAULT_FSR4_VARIANT,
+  FRAMEGEN_BACKEND_OPTIONS,
+  DEFAULT_FRAMEGEN_BACKEND,
+} from "../utils/constants";
 import { InstallationStatus } from "./InstallationStatus";
 import { OptiScalerHeader } from "./OptiScalerHeader";
 import { ClipboardCommands } from "./ClipboardCommands";
@@ -18,6 +26,8 @@ interface FgmodInfo {
   version?: string | null;
   selected_fsr4_variant?: string | null;
   selected_fsr4_variant_label?: string | null;
+  framegen_backend?: string | null;
+  framegen_backend_label?: string | null;
   install_manifest_present?: boolean;
 }
 
@@ -37,19 +47,22 @@ export function OptiScalerControls({ pathExists, setPathExists, fgmodInfo }: Opt
   const [dllName, setDllName] = useState<string>(DEFAULT_PROXY_DLL);
   const [fsr4Variant, setFsr4Variant] = useState<string>(DEFAULT_FSR4_VARIANT);
   const [fsr4VariantTouched, setFsr4VariantTouched] = useState(false);
+  const [framegenBackend, setFramegenBackendValue] = useState<string>(DEFAULT_FRAMEGEN_BACKEND);
+  const [framegenBackendTouched, setFramegenBackendTouched] = useState(false);
   const [switchingVariant, setSwitchingVariant] = useState(false);
+  const [switchingBackend, setSwitchingBackend] = useState(false);
   useEffect(() => {
     if (installResult) {
       return createAutoCleanupTimer(() => setInstallResult(null), TIMEOUTS.resultDisplay);
     }
-    return () => {}; // Ensure a cleanup function is always returned
+    return undefined;
   }, [installResult]);
 
   useEffect(() => {
     if (uninstallResult) {
       return createAutoCleanupTimer(() => setUninstallResult(null), TIMEOUTS.resultDisplay);
     }
-    return () => {}; // Ensure a cleanup function is always returned
+    return undefined;
   }, [uninstallResult]);
 
   useEffect(() => {
@@ -59,16 +72,26 @@ export function OptiScalerControls({ pathExists, setPathExists, fgmodInfo }: Opt
     }
   }, [fgmodInfo?.selected_fsr4_variant, fsr4VariantTouched]);
 
+  useEffect(() => {
+    const installedBackend = fgmodInfo?.framegen_backend;
+    if (!framegenBackendTouched && installedBackend && FRAMEGEN_BACKEND_OPTIONS.some((option) => option.value === installedBackend)) {
+      setFramegenBackendValue(installedBackend);
+    }
+  }, [fgmodInfo?.framegen_backend, framegenBackendTouched]);
+
   const handleInstallClick = async () => {
     try {
       setInstalling(true);
-      const result = await runInstallFGMod(fsr4Variant);
+      const result = await runInstallFGMod(fsr4Variant, framegenBackend);
       setInstallResult(result);
       if (result.status === "success") {
         setPathExists(true);
+        setFsr4VariantTouched(false);
+        setFramegenBackendTouched(false);
       }
     } catch (e) {
       console.error(e);
+      setInstallResult({ status: "error", message: e instanceof Error ? e.message : "Installation failed." });
     } finally {
       setInstalling(false);
     }
@@ -84,11 +107,35 @@ export function OptiScalerControls({ pathExists, setPathExists, fgmodInfo }: Opt
       }
     } catch (e) {
       console.error(e);
+      setUninstallResult({ status: "error", message: e instanceof Error ? e.message : "Uninstall failed." });
     } finally {
       setUninstalling(false);
     }
   };
 
+  const handleFramegenBackendChange = async (nextBackend: string) => {
+    const previousBackend = framegenBackend;
+    setFramegenBackendValue(nextBackend);
+    setFramegenBackendTouched(true);
+    if (pathExists !== true) return;
+
+    try {
+      setSwitchingBackend(true);
+      const result = await setFramegenBackend(nextBackend);
+      if (result.status !== "success") {
+        throw new Error(result.message || result.output || "Failed to update the frame-generation backend.");
+      }
+      setFramegenBackendValue(result.framegen_backend || nextBackend);
+      setFramegenBackendTouched(false);
+    } catch (error) {
+      console.error(error);
+      setFramegenBackendValue(previousBackend);
+      setFramegenBackendTouched(false);
+    } finally {
+      setSwitchingBackend(false);
+    }
+  };
+
   const handleFsr4VariantChange = async (nextVariant: string) => {
     const previousVariant = fsr4Variant;
     setFsr4Variant(nextVariant);
@@ -132,13 +179,28 @@ export function OptiScalerControls({ pathExists, setPathExists, fgmodInfo }: Opt
           menuLabel="Default FSR4 runtime"
           selectedOption={fsr4Variant}
           rgOptions={FSR4_VARIANT_OPTIONS.map((option) => ({ data: option.value, label: option.label }))}
-          disabled={installing || uninstalling || switchingVariant}
+          disabled={installing || uninstalling || switchingVariant || switchingBackend}
           onChange={(option) => {
             void handleFsr4VariantChange(String(option.data));
           }}
         />
       </PanelSectionRow>
 
+      <PanelSectionRow>
+        <DropdownItem
+          layout="below"
+          label="Frame generation backend"
+          description={FRAMEGEN_BACKEND_OPTIONS.find((option) => option.value === framegenBackend)?.hint}
+          menuLabel="Frame generation backend"
+          selectedOption={framegenBackend}
+          rgOptions={FRAMEGEN_BACKEND_OPTIONS.map((option) => ({ data: option.value, label: option.label }))}
+          disabled={installing || uninstalling || switchingBackend}
+          onChange={(option) => {
+            void handleFramegenBackendChange(String(option.data));
+          }}
+        />
+      </PanelSectionRow>
+
       {pathExists === true && fgmodInfo?.version && installedVariantLabel && (
         <PanelSectionRow>
           <Field label="Installed bundle" description={`OptiScaler ${fgmodInfo.version}`}>
@@ -162,7 +224,7 @@ export function OptiScalerControls({ pathExists, setPathExists, fgmodInfo }: Opt
       )}
 
       {pathExists === true && (
-        <SteamGamePatcher dllName={dllName} fsr4Variant={fsr4Variant} />
+        <SteamGamePatcher dllName={dllName} fsr4Variant={fsr4Variant} framegenBackend={framegenBackend} />
       )}
 
       <ClipboardCommands pathExists={pathExists} dllName={dllName} />
@@ -192,8 +254,12 @@ export function OptiScalerControls({ pathExists, setPathExists, fgmodInfo }: Opt
         onManualModeChange={setAdvancedModeEnabled}
         dllName={dllName}
         fsr4Variant={fsr4Variant}
+        framegenBackend={framegenBackend}
       />
 
+      <ResultDisplay result={installResult} />
+      <ResultDisplay result={uninstallResult} />
+
       {!advancedModeEnabled && (
         <InstructionCard pathExists={pathExists} />
       )}
diff --git a/src/components/SteamGamePatcher.tsx b/src/components/SteamGamePatcher.tsx
index e8ac3d2..cd8fe3c 100644
--- a/src/components/SteamGamePatcher.tsx
+++ b/src/components/SteamGamePatcher.tsx
@@ -4,12 +4,24 @@ import { toaster } from "@decky/api";
 import { listInstalledGames, getGameStatus, patchGame, unpatchGame } from "../api";
 import { FSR4_VARIANT_OPTIONS } from "../utils/constants";
 
-// ─── SteamClient helpers ─────────────────────────────────────────────────────
+type SteamAppsApi = {
+  RegisterForAppDetails?: (
+    appId: number,
+    callback: (details: { strLaunchOptions?: string }) => void
+  ) => { unregister: () => void };
+  SetAppLaunchOptions?: (appId: number, options: string) => void;
+};
+
+const getSteamApps = (): SteamAppsApi | undefined => {
+  if (typeof SteamClient === "undefined") return undefined;
+  return SteamClient.Apps as unknown as SteamAppsApi;
+};
 
 const getAppLaunchOptions = (appId: number): Promise<string> =>
   new Promise((resolve, reject) => {
-    if (typeof SteamClient === "undefined" || !SteamClient?.Apps?.RegisterForAppDetails) {
-      resolve("");
+    const apps = getSteamApps();
+    if (!apps || typeof apps.RegisterForAppDetails !== "function" || typeof apps.SetAppLaunchOptions !== "function") {
+      reject(new Error("Steam launch-options API is unavailable; patching was not started."));
       return;
     }
     let settled = false;
@@ -20,7 +32,7 @@ const getAppLaunchOptions = (appId: number): Promise<string> =>
       unregister();
       reject(new Error("Timed out reading launch options."));
     }, 5000);
-    const registration = SteamClient.Apps.RegisterForAppDetails(
+    const registration = apps.RegisterForAppDetails(
       appId,
       (details: { strLaunchOptions?: string }) => {
         if (settled) return;
@@ -31,15 +43,25 @@ const getAppLaunchOptions = (appId: number): Promise<string> =>
       }
     );
     unregister = registration.unregister;
+    if (settled) unregister();
   });
 
 const setAppLaunchOptions = (appId: number, options: string): void => {
-  if (typeof SteamClient !== "undefined" && SteamClient?.Apps?.SetAppLaunchOptions) {
-    SteamClient.Apps.SetAppLaunchOptions(appId, options);
+  const apps = getSteamApps();
+  if (!apps || typeof apps.SetAppLaunchOptions !== "function") {
+    throw new Error("Steam launch-options API is unavailable; launch options were not changed.");
   }
+  apps.SetAppLaunchOptions(appId, options);
 };
 
-// ─── Types ───────────────────────────────────────────────────────────────────
+const canManageLaunchOptions = (): boolean => {
+  const apps = getSteamApps();
+  return Boolean(
+    apps &&
+    typeof apps.RegisterForAppDetails === "function" &&
+    typeof apps.SetAppLaunchOptions === "function"
+  );
+};
 
 type GameEntry = { appid: string; name: string; install_found?: boolean };
 
@@ -55,20 +77,19 @@ type GameStatus = {
   fsr4_variant?: string | null;
   fsr4_variant_label?: string | null;
   fsr4_upscaler_sha256?: string | null;
+  framegen_backend?: string | null;
+  framegen_backend_label?: string | null;
 };
 
-// ─── Module-level state persistence ──────────────────────────────────────────
-
 let lastSelectedAppId = "";
 
-// ─── Component ───────────────────────────────────────────────────────────────
-
 interface SteamGamePatcherProps {
   dllName: string;
   fsr4Variant: string;
+  framegenBackend: string;
 }
 
-export function SteamGamePatcher({ dllName, fsr4Variant }: SteamGamePatcherProps) {
+export function SteamGamePatcher({ dllName, fsr4Variant, framegenBackend }: SteamGamePatcherProps) {
   const [games, setGames] = useState<GameEntry[]>([]);
   const [gamesLoading, setGamesLoading] = useState(true);
   const [selectedAppId, setSelectedAppId] = useState<string>(() => lastSelectedAppId);
@@ -77,8 +98,6 @@ export function SteamGamePatcher({ dllName, fsr4Variant }: SteamGamePatcherProps
   const [busyAction, setBusyAction] = useState<"patch" | "unpatch" | null>(null);
   const [resultMessage, setResultMessage] = useState<string>("");
 
-  // ── Data loaders ───────────────────────────────────────────────────────────
-
   const loadGames = useCallback(async () => {
     setGamesLoading(true);
     try {
@@ -136,8 +155,6 @@ export function SteamGamePatcher({ dllName, fsr4Variant }: SteamGamePatcherProps
     void loadStatus(selectedAppId);
   }, [selectedAppId, loadStatus]);
 
-  // ── Derived state ──────────────────────────────────────────────────────────
-
   const selectedGame = useMemo(
     () => games.find((g) => g.appid === selectedAppId) ?? null,
     [games, selectedAppId]
@@ -163,20 +180,16 @@ export function SteamGamePatcher({ dllName, fsr4Variant }: SteamGamePatcherProps
     return `Patch with ${dllName}`;
   }, [busyAction, dllName, gameStatus, isPatchedWithDifferentDll, selectedGame]);
 
-  // ── Actions ────────────────────────────────────────────────────────────────
-
   const handlePatch = useCallback(async () => {
     if (!selectedGame || !selectedAppId || busyAction) return;
     setBusyAction("patch");
     setResultMessage("");
     try {
-      let currentLaunchOptions = "";
-      try {
-        currentLaunchOptions = await getAppLaunchOptions(Number(selectedAppId));
-      } catch {
-        // non-fatal: proceed without current launch options
+      if (!canManageLaunchOptions()) {
+        throw new Error("Steam launch-options API is unavailable; patching was not started.");
       }
-      const result = await patchGame(selectedAppId, dllName, currentLaunchOptions, fsr4Variant);
+      const currentLaunchOptions = await getAppLaunchOptions(Number(selectedAppId));
+      const result = await patchGame(selectedAppId, dllName, currentLaunchOptions, fsr4Variant, framegenBackend);
       if (result.status !== "success") throw new Error(result.message || "Patch failed.");
       setAppLaunchOptions(Number(selectedAppId), result.launch_options || "");
       const msg = result.message || `Patched ${selectedGame.name}.`;
@@ -190,13 +203,16 @@ export function SteamGamePatcher({ dllName, fsr4Variant }: SteamGamePatcherProps
     } finally {
       setBusyAction(null);
     }
-  }, [busyAction, dllName, fsr4Variant, loadStatus, selectedAppId, selectedGame]);
+  }, [busyAction, dllName, framegenBackend, fsr4Variant, loadStatus, selectedAppId, selectedGame]);
 
   const handleUnpatch = useCallback(async () => {
     if (!selectedGame || !selectedAppId || busyAction) return;
     setBusyAction("unpatch");
     setResultMessage("");
     try {
+      if (!canManageLaunchOptions()) {
+        throw new Error("Steam launch-options API is unavailable; unpatching was not started.");
+      }
       const result = await unpatchGame(selectedAppId);
       if (result.status !== "success") throw new Error(result.message || "Unpatch failed.");
       setAppLaunchOptions(Number(selectedAppId), result.launch_options || "");
@@ -213,8 +229,6 @@ export function SteamGamePatcher({ dllName, fsr4Variant }: SteamGamePatcherProps
     }
   }, [busyAction, loadStatus, selectedAppId, selectedGame]);
 
-  // ── Status display ─────────────────────────────────────────────────────────
-
   const statusDisplay = useMemo(() => {
     if (!selectedGame) return { text: "—", color: undefined as string | undefined };
     if (statusLoading) return { text: "Loading...", color: undefined };
@@ -230,8 +244,6 @@ export function SteamGamePatcher({ dllName, fsr4Variant }: SteamGamePatcherProps
 
   const focusableFieldProps = { focusable: true, highlightOnFocus: true } as const;
 
-  // ── Render ─────────────────────────────────────────────────────────────────
-
   return (
     <>
       <PanelSectionRow>
@@ -278,6 +290,14 @@ export function SteamGamePatcher({ dllName, fsr4Variant }: SteamGamePatcherProps
           </PanelSectionRow>
 
           <PanelSectionRow>
+            <Field {...focusableFieldProps} label="Frame generation backend">
+              {gameStatus?.patched
+                ? (gameStatus?.framegen_backend_label || gameStatus?.framegen_backend || "Unknown")
+                : `Will patch with ${framegenBackend}`}
+            </Field>
+          </PanelSectionRow>
+
+          <PanelSectionRow>
             <ButtonItem layout="below" disabled={!canPatch} onClick={handlePatch}>
               {patchButtonLabel}
             </ButtonItem>
diff --git a/src/index.tsx b/src/index.tsx
index 4a9a9f6..6d598fc 100644
--- a/src/index.tsx
+++ b/src/index.tsx
@@ -2,7 +2,6 @@ import { definePlugin } from "@decky/api";
 import { MdOutlineAutoAwesomeMotion } from "react-icons/md";
 import { useState, useEffect } from "react";
 import { OptiScalerControls } from "./components";
-// import { InstalledGamesSection } from "./components/InstalledGamesSection";
 import { checkFGModPath } from "./api";
 import { safeAsyncOperation } from "./utils";
 import { TIMEOUTS } from "./utils/constants";
@@ -12,6 +11,8 @@ type FgmodInfo = {
   version?: string | null;
   selected_fsr4_variant?: string | null;
   selected_fsr4_variant_label?: string | null;
+  framegen_backend?: string | null;
+  framegen_backend_label?: string | null;
   install_manifest_present?: boolean;
 };
 
@@ -43,11 +44,6 @@ function MainContent() {
         setPathExists={setPathExists}
         fgmodInfo={fgmodInfo}
       />
-      {pathExists === true ? (
-        <>
-          {/* <InstalledGamesSection /> */}
-        </>
-      ) : null}
     </>
   );
 }
diff --git a/src/utils/constants.ts b/src/utils/constants.ts
index 3af9874..2568dd4 100644
--- a/src/utils/constants.ts
+++ b/src/utils/constants.ts
@@ -85,6 +85,22 @@ export const FSR4_VARIANT_OPTIONS = [
 export type Fsr4VariantValue = typeof FSR4_VARIANT_OPTIONS[number]["value"];
 export const DEFAULT_FSR4_VARIANT: Fsr4VariantValue = "rdna23-int8";
 
+export const FRAMEGEN_BACKEND_OPTIONS = [
+  {
+    value: "auto",
+    label: "OptiScaler automatic selection",
+    hint: "Let OptiScaler select the compatible frame-generation path.",
+  },
+  {
+    value: "nukems",
+    label: "Nukem's DLSSG → FSR3",
+    hint: "Use Nukem's DLSSG-to-FSR3 path for games that need it.",
+  },
+] as const;
+
+export type FramegenBackendValue = typeof FRAMEGEN_BACKEND_OPTIONS[number]["value"];
+export const DEFAULT_FRAMEGEN_BACKEND: FramegenBackendValue = "auto";
+
 // Common timeout values
 export const TIMEOUTS = {
   resultDisplay: 5000,  // 5 seconds
diff --git a/tests/test_backend.py b/tests/test_backend.py
new file mode 100644
index 0000000..69165f1
--- /dev/null
+++ b/tests/test_backend.py
@@ -0,0 +1,104 @@
+import tempfile
+import unittest
+from pathlib import Path
+
+from backend import config
+from backend.bundle import BundleManager
+from backend.patcher import PatchManager
+from backend.steam import SteamLibrary
+
+
+class BackendSafetyTests(unittest.TestCase):
+    def setUp(self):
+        self.temp_dir = tempfile.TemporaryDirectory()
+        root = Path(self.temp_dir.name)
+        self.home = root / "home"
+        self.plugin_dir = root / "plugin"
+        self.home.mkdir()
+        self.plugin_dir.mkdir()
+
+        bundle_path = self.home / "fgmod"
+        (bundle_path / "renames").mkdir(parents=True)
+        (bundle_path / "plugins").mkdir()
+        (bundle_path / "fsr4-rdna2-3").mkdir()
+        (bundle_path / "OptiScaler.dll").write_bytes(b"optiscaler")
+        (bundle_path / "renames" / "dxgi.dll").write_bytes(b"managed-proxy")
+        (bundle_path / "OptiScaler.ini").write_text("FGInput=auto\nFGOutput=auto\n", encoding="utf-8")
+        (bundle_path / "plugins" / "OptiPatcher.asi").write_bytes(b"plugin")
+        (bundle_path / "fsr4-rdna2-3" / "amd_fidelityfx_upscaler_dx12.dll").write_bytes(b"upscaler")
+
+        logger = lambda _message: None
+        bundle = BundleManager(self.home, self.plugin_dir, logger)
+        self.manager = PatchManager(self.home, bundle, SteamLibrary(self.home, logger), logger)
+        self.target = root / "game"
+        (self.target / "plugins").mkdir(parents=True)
+        (self.target / "plugins" / "keep.txt").write_text("user-owned", encoding="utf-8")
+        (self.target / "dxgi.dll").write_bytes(b"original-game-proxy")
+        (self.target / "OptiScaler.ini").write_text("FGInput=auto\nFGOutput=auto\nUserSetting=true\n", encoding="utf-8")
+
+    def tearDown(self):
+        self.temp_dir.cleanup()
+
+    def test_patch_and_unpatch_preserve_unowned_files(self):
+        result = self.manager.manual_patch_directory(str(self.target), "dxgi.dll", "rdna23-int8", "auto")
+        self.assertEqual(result["status"], "success")
+        self.assertTrue((self.target / "FRAMEGEN_PATCH").exists())
+        self.assertTrue((self.target / "dxgi.dll.b").exists())
+        self.assertTrue((self.target / "plugins" / "keep.txt").exists())
+
+        cleanup = self.manager.manual_unpatch_directory(str(self.target))
+        self.assertEqual(cleanup["status"], "success")
+        self.assertFalse((self.target / "FRAMEGEN_PATCH").exists())
+        self.assertEqual((self.target / "dxgi.dll").read_bytes(), b"original-game-proxy")
+        self.assertEqual((self.target / "plugins" / "keep.txt").read_text(encoding="utf-8"), "user-owned")
+        self.assertEqual(
+            (self.target / "OptiScaler.ini").read_text(encoding="utf-8"),
+            "FGInput=auto\nFGOutput=auto\nUserSetting=true\n",
+        )
+        self.assertFalse((self.target / "plugins" / "OptiPatcher.asi").exists())
+
+    def test_unpatch_refuses_modified_managed_file_and_keeps_marker(self):
+        result = self.manager.manual_patch_directory(str(self.target), "dxgi.dll", "rdna23-int8", "nukems")
+        self.assertEqual(result["status"], "success")
+        (self.target / "dxgi.dll").write_bytes(b"user-modified")
+
+        cleanup = self.manager.manual_unpatch_directory(str(self.target))
+        self.assertEqual(cleanup["status"], "error")
+        self.assertTrue((self.target / "FRAMEGEN_PATCH").exists())
+        self.assertEqual((self.target / "dxgi.dll").read_bytes(), b"user-modified")
+        self.assertTrue((self.target / "plugins" / "keep.txt").exists())
+
+    def test_appid_unpatch_propagates_cleanup_failure(self):
+        class FakeSteam:
+            def game_record(self, appid):
+                return {"appid": appid, "name": "Test Game", "install_path": str(self_target)}
+
+            def is_game_running(self, _game_info):
+                return False
+
+            def guess_patch_target(self, _game_info):
+                return self_target, None
+
+        self_target = self.target
+        self.manager.steam = FakeSteam()
+        result = self.manager.patch_game("123", "dxgi.dll", "", "rdna23-int8", "auto")
+        self.assertEqual(result["status"], "success")
+        (self.target / "dxgi.dll").write_bytes(b"modified after patch")
+
+        cleanup = self.manager.unpatch_game("123")
+        self.assertEqual(cleanup["status"], "error")
+        self.assertTrue((self.target / "FRAMEGEN_PATCH").exists())
+
+    def test_backend_configuration_is_explicit(self):
+        ini_file = self.target / "backend.ini"
+        ini_file.write_text("FGInput=auto\nFGOutput=auto\n", encoding="utf-8")
+        self.assertTrue(config.configure(ini_file, "nukems"))
+        self.assertIn("FGInput=nukems", ini_file.read_text(encoding="utf-8"))
+        self.assertIn("FGOutput=nukems", ini_file.read_text(encoding="utf-8"))
+        self.assertTrue(config.configure(ini_file, "auto"))
+        self.assertIn("FGInput=auto", ini_file.read_text(encoding="utf-8"))
+        self.assertIn("FGOutput=auto", ini_file.read_text(encoding="utf-8"))
+
+
+if __name__ == "__main__":
+    unittest.main()