Decky GameVault

A community fork of Junk-Store — an open, extensible multi-store game launcher for the Steam Deck and other Decky-compatible handhelds (ROG Ally, Legion Go, …).

About

GameVault lets you browse, install, and launch non-Steam games directly from Game Mode — no Desktop Mode required. Games are added to your Steam library as shortcuts with the right compatibility tool (Proton, or native for engines that don't need it), artwork, and per-game launch settings.

Built on the Junk-Store framework, this fork adds seven store/library integrations and a large set of quality-of-life features on top of the original Epic Games support.

Current release: v1.2.1 — see Releases.

Store & Library Integrations

Source	Backend	Runs via	Notes
Epic Games	Legendary	Proton	Original upstream integration
GOG	gogdl	Proton	Community extension — login, install, DLC manager, cloud saves
Amazon Games	Nile	Proton	Community extension
itch.io	itch.io API	Proton / native	Owned games and your Collections
RPG Maker	NW.js / mkxp-z	Native (no Proton)	Drop-folder scanner for MV/MZ/VX Ace/XP/VX
EA Play (beta)	maxima-cli	Proton	EA back-catalog titles
Ubisoft (Optima) (beta)	optima-cli	Proton	Owned Ubisoft games via built-in Uplay R1 / Orbit R2 loaders — no Ubisoft Connect

A Note on GOG

The official Junk-Store project offers its own GOG integration via Patreon or Ko-fi. The GOG extension in this fork is a separate, independently-built implementation. If you want the officially supported GOG experience, please consider supporting the original project.

Setup Notes

• Epic Games — Works out of the box. Log in from the plugin.
• GOG — Install dependencies from the About menu first. Login uses a browser redirect (needs a keyboard to paste the redirect URL once).
• Amazon Games — Install dependencies from the About menu first. Browser-redirect login, same as GOG.
• itch.io — Log in with your itch.io API key to access purchased and claimed games. See itch.io Collections below.
• RPG Maker — Install dependencies (this fetches the native NW.js + mkxp-z runtimes), then drop game folders into the RPG Maker install location. See RPG Maker (Native) below.
• EA Play (beta) — Requires the maxima-cli EA client. Install dependencies from the About menu, then log in with your EA account.
• Ubisoft (Optima) (beta) — Install dependencies from the About menu (fetches the optima-cli runtime), then log in with your Ubisoft account in the browser. Games run through GameVault's own DRM loaders — no Ubisoft Connect install needed. See Ubisoft (Optima) below.

Features

Original (from Junk-Store)

Part of the upstream framework GameVault is built on:

• Epic Games Store — Full integration via Legendary (install, update, verify, repair)
• EOS Overlay Management — Install, update, and remove the Epic Online Services overlay
• Per-Game Launch Configuration — Proton version, environment variables, FPS limiting, FSR, ESYNC/FSYNC toggles from the QAM
• Platform Config Editor — Edit game INI/config files directly from Game Mode
• Executable Runner — Run executables (EXE, BAT, MSI) from a game's install folder
• Protontricks Integration — Launch the Protontricks GUI for manual Proton fixes
• UMU ID Management — Update UMU IDs for compatibility tracking
• Registry Fix — Apply Windows registry fixes via Proton (Epic)
• Dependency Installer — One-click install for Proton EasyAntiCheat and BattlEye runtimes
• Import/Move Games — Manage game storage locations
• Custom Backend Support — Extensible architecture for community store scripts
• Developer Mode — Toggle developer tools and the log viewer

Community Additions (GameVault Fork)

Added by this fork:

• GOG Extension — Full game management, browser-based login, cloud save sync
• GOG DLC Manager — Per-game gear menu to install/remove individual DLCs, with a base-game-only toggle
• Amazon Games Extension — Full game management via the Nile backend
• itch.io Extension — Owned games via API key
• itch.io Collections — Your itch.io Collections imported as a library source: an Owned tab plus one nested sub-tab per Collection. Toggle Collection import on/off in the tab config
• RPG Maker (Native) Extension — Run RPG Maker games with no Proton (see below)
• EA Play Extension (beta) — Launch EA back-catalog titles through maxima-cli
• Ubisoft (Optima) Extension (beta) — Install and launch owned Ubisoft games through built-in Uplay R1 / Orbit R2 loaders, no Ubisoft Connect required (see below)
• My Added Games — A tab for games you add manually, kept alongside the store libraries
• SteamGridDB Artwork Fallback — Automatically fills missing artwork from SteamGridDB. Set your API key in any store's tab config (gear icon); results are cached per game
• Artwork Scan — Sweep a library and backfill missing cover/hero/logo art
• Cloud Save Sync (Epic & GOG) — Upload/download saves, with a per-game auto-sync toggle
• GE-Proton Installer — One-click download and install of the latest GE-Proton from the Dependencies tab
• Proton Fixes Lookup — Look up known fixes for any installed game from the umu-protonfixes database; falls back to Steam fixes via UMU ID
• Auto-Apply Proton Fixes — One-click apply of known environment-variable fixes to a game's launch config
• Storage Management — Total disk usage across all stores, per-store breakdown, free space, and installed games sorted by size, from the About page's Storage tab
• Batch Install Queue — Select multiple games from a store grid and queue them for sequential download and install
• Game Update Detection — Checks for updates when viewing an installed game (Epic, GOG, Amazon) and flags an "Update Available" indicator on the play button
• Improved GOG Uninstall — Cleans up gogdl manifest state so games can be reinstalled without manual intervention

RPG Maker (Native)

Runs RPG Maker games natively — no Wine or Proton — so they're light on a handheld:

• MV / MZ launch under a bundled native Linux NW.js.
• VX Ace / XP / VX (RGSS) launch under mkxp-z, a native C++ reimplementation of the RGSS runtime.

There's no store to log into — it's a drop-folder scanner. Copy a game's folder into the RPG Maker install location; the extension detects the engine, lists it, and "Add" creates a native Steam shortcut (compatibility tool cleared). The NW.js and mkxp-z runtimes are fetched by About → Install Dependencies.

Run-Time Packages (RTP): some older VX Ace/XP/VX games rely on RPG Maker's shared RTP assets rather than bundling their own. When you run Install Dependencies, GameVault fetches those RTPs directly from RPG Maker's official publisher source (Degica/Kadokawa) and extracts them on-device — it does not re-host them. Most games ship self-contained and don't need this at all.

Ubisoft (Optima) (beta)

Installs and launches games you own on Ubisoft, backed by a standalone optima-cli client — no Ubisoft Connect install required. Ownership is verified against your Ubisoft account, and games run through GameVault's own Uplay R1 / Orbit R2 DRM loaders under Proton.

Optima self-heals on every launch — it re-writes the game's registry keys and DRM config, makes sure the local save folder exists (your saves are never touched), and re-verifies the loader. So if a game fails once, try launching a second time before assuming it's broken.

Some limitations to be aware of (it's a beta):

• Single-player only. Online/multiplayer is untested and generally won't work — the loaders emulate local ownership and can't provide a real online session (e.g. free-to-play titles like Brawlhalla that auth against Ubisoft's servers will bail).
• Uplay R1 / Orbit R2 titles only. Games protected by Denuvo or any other DRM can't be emulated and won't launch. For those, use Ubisoft Connect via Heroic.
• Tested working on the ROG Ally so far: Assassin's Creed III, Assassin's Creed IV: Black Flag, Assassin's Creed Unity, Beyond Good & Evil, Tom Clancy's Splinter Cell, and Watch_Dogs.

If a game won't launch, retry once, then open a GitHub issue with the "[Optima] game won't launch" template — include the game title, product id, and the logs from ~/homebrew/logs/GameVault/.

The optima-cli runtime is fetched by About → Install Dependencies.

Installing

1. Download GameVault.zip from the Releases page.
2. Transfer it to your device.
3. Extract to ~/homebrew/plugins/GameVault/.
4. Restart Decky Loader.
5. Open the plugin, go to About → Install Dependencies to pull the runtimes needed by GOG, Amazon, EA Play, Ubisoft (Optima), and RPG Maker.

Adding a single extension to an existing install

Two extensions ship standalone installers you can run on-device to add them without reinstalling the whole plugin:

• install-itchio-extension.sh
• install-rpgmaker-extension.sh

Building from source

pnpm install
pnpm run build

The frontend is TypeScript (React); most store extensions are shell + Python under defaults/scripts/Extensions/<Store>/. dist/ is git-ignored and produced by the build.

Contributing / Backend CLIs

The Ubisoft (Optima) and EA Play (Maxima) extensions are thin GameVault wrappers around standalone command-line clients. Those clients live in their own repos, are the place where the real login / install / launch logic lives, and run standalone on the desktop (no Decky or Steam required) — which makes them easy to hack on and test outside the plugin:

• Optima (Ubisoft Connect client, Rust optima-cli) — github.com/Starkka15/Optima
• Maxima (EA Desktop replacement, maxima-cli) — github.com/Starkka15/Maxima

If you'd like to help develop or flesh these out — more supported games, better DRM handling, online/auth work — contributions to those repos are welcome. GameVault picks up the improvements automatically the next time it fetches the runtime via About → Install Dependencies. Extension-side glue (tabs, install/launch scripts) lives here under defaults/scripts/Extensions/{Optima,EA}/.

Credits

Original Project

• Junk-Store by Eben Bruyns
• Eben Bruyns (junkrunner) — Software Sorcerer
• Annie Ryan (mrs junkrunner) — Order Oracle
• Jesse Bofill — Visual Virtuoso
• Tech — Glitch Gladiator
• Logan (Beebles) — UI Developer

Community Fork

• Starkka15 — GOG, Amazon, itch.io, RPG Maker (native), EA Play, and Ubisoft (Optima) extensions; optima-cli (the Ubisoft Connect client itself); itch.io Collections; GOG DLC manager; My Added Games; cloud save sync; SteamGridDB integration + artwork scan; GE-Proton installer; protonfixes lookup/apply; storage management; batch install queue; update detection

Backends & Third-Party Tools

Most of the fork's store extensions are wrappers that drive excellent third-party tools. Full credit to their authors — GameVault just integrates them into Game Mode. In several cases we maintain forked branches with GameVault-specific changes: upstream didn't always work as-is under GameVault's Proton/SteamOS handheld flow, so we've patched things to make them reliable there. Those forks track upstream and exist only to bridge the gap — all credit stays with the original authors.

• gogdl — the GOG downloader behind the GOG extension, from the Heroic Games Launcher project (Paweł Lidwin / imLinguin and contributors). GameVault installs the upstream heroic-gogdl flatpak.
• Nile — the Amazon Games downloader behind the Amazon extension, by Paweł Lidwin (imLinguin).
• Maxima (maxima-cli) — the open-source EA Desktop replacement powering the EA Play extension, by the Maxima project (ArmchairDevelopers) and contributors. We run a forked branch that adds the non-interactive install/launch CLI plus GameVault-specific fixes (e.g. live download-progress reporting, install resume, registry self-heal).
• RPG Maker runtimes — NW.js (runs MV/MZ) by the NW.js project; mkxp-z (runs VX Ace/XP/VX), a continuation of mkxp by Jonas Kulla (Ancurio). GameVault only repackages the mkxp-z AppImage; the runtime is theirs.
• Ubisoft (Optima) DRM loaders — optima-cli is ours, but the emulation shims it deploys are not: the Uplay R1 loader and Orbit R2 loader by Re0xCat, Ubisoft demux/manifest/install-protocol reversing by YoobieRE, and Proton launching via umu-launcher. We vendor and patch the loaders (e.g. the Orbit R2 shim is fixed up in optima-cli's tree) so they work under our Proton launch flow — original authorship is unchanged.
• Legendary — the Epic Games downloader behind the Epic integration, by Rui Pinheiro (derrod) (used via the upstream Junk-Store Epic integration).
• GE-Proton — the custom Proton build fetched by the GE-Proton installer, by Thomas Crider (GloriousEggroll).
• umu-protonfixes — the Proton-fixes database behind the protonfixes lookup/apply feature (and umu-launcher, also used by Optima), by Open-Wine-Components.
• SteamGridDB — the community artwork source powering the artwork fallback and library artwork scan.
• DOSBox Staging — runs DOS-era GOG titles; installed as a flatpak on demand.

Platform

GameVault is a plugin for Decky Loader and is built with decky-frontend-lib — both by the SteamDeck Homebrew project. None of this exists without their plugin platform.

Links

• Original project: github.com/ebenbruyns/junkstore
• Official Junk-Store Discord:

License

See LICENSE. GameVault inherits Junk-Store's license as a fork.

AI Disclosure

This project is developed with AI assistance. See AI.md for how AI is used here, the ethical obligations behind it, and how upstream credit and licensing are handled.