Jackbox Megapicker Patcher

Patches the Jackbox Megapicker to support launching games installed in different directories, includes an ASAR integrity check bypass.

Note

The ASAR patcher is AI generated, but I did reverse engineer it myself to figure out how to do it.

How to use

After running the executable, your game should be patched. From here, you can input the games inside of {MEGAPICKER_DIRECTORY}/games/{STEAM_ID}/

• MEGAPICKER_DIRECTORY is where you installed the megapicker, for example: C:\Program Files (x86)\Steam\steamapps\common\The Jackbox Megapicker
• STEAM_ID is the steam ID for each of the packs/standalone games. For example, the ID of Jackbox Pack 11 is 3364070

Custom directory per game

Instead of placing every game under {MEGAPICKER_DIRECTORY}/games/{STEAM_ID}/, you can point individual games at any directory with the repeatable --game <STEAM_ID>=<PATH> option:

jackbox_megapicker_patcher --game 3364070=/data/jackbox/pack11 --game 2748040=/data/jackbox/pack10

Games that aren't listed keep falling back to {MEGAPICKER_DIRECTORY}/games/{STEAM_ID}/. Absolute paths are recommended, as relative paths are resolved against the megapicker's own directory at launch time.

Custom launch arguments

You can append extra arguments to the command the megapicker uses to launch a game. Use the repeatable --launch-arg <ARG> option to apply an argument to every game, and --game-launch-arg <STEAM_ID>=<ARG> to apply one only to a specific game (on top of any global --launch-arg values):

jackbox_megapicker_patcher \
  --launch-arg -fullscreen \
  --game-launch-arg 3364070=-jbg.config --game-launch-arg 3364070=foo=bar

These are added after the arguments the megapicker already passes (-launchTo …, -jbg.config isBundle=false), both when launching the game's executable directly and when falling back to steam://run/….

Note

The asar patcher might be unreliable, so you can manually input the patched the main.js file to .vite/build/main.js inside the app.asar file.

1. Install 7zip and this plugin for it
2. Run the patcher
3. Delete resources/app.asar and rename the backup file to resources/app.asar
4. Open resources/app.asar inside of 7zip and navigate to .vite/build
5. Drag over the main.js file inside of resources/main.js inside of 7zip, you should be prompted to override
6. Override the file and close 7zip

The code execution cannot proceed because steam_api64.dll was not found

You must install the Steamworks SDK and place the steam_api64.dll in the same directory as the executable.

1. Go to Steamworks SDK Releases
2. Press "Install latest SDK"
3. Extract the downloaded .zip file.
4. You can find the .dll within the ./sdk/redistributable_bin/win64 folder inside of the extracted folder

Usage

Usage: jackbox_megapicker_patcher.exe [OPTIONS] [PATH]

Arguments:
  [PATH]
          The path to your Steam install of Jackbox Megapicker.

          If not specified, automatically query Steam for the install location.

Options:
  -g, --game <STEAM_ID=PATH>
          Map a game's Steam ID to a specific install directory. Repeatable.

          Format: <STEAM_ID>=<PATH>, e.g. --game 3364070=/games/pack11

          Games not listed here fall back to `<MEGAPICKER>/games/<STEAM_ID>`.

  -L, --launch-arg <ARG>
          Extra argument appended to every game's launch command. Repeatable.

          e.g. --launch-arg -fullscreen

      --game-launch-arg <STEAM_ID=ARG>
          Extra launch argument for a specific game, keyed by Steam ID. Repeatable.

          Format: <STEAM_ID>=<ARG>, e.g. --game-launch-arg 3364070=-fullscreen

          Applied on top of any --launch-arg values for that game.

  -a, --asar
          Disable app.asar patch

  -e, --executable
          Disable executable patch

  -h, --help
          Print help (see a summary with '-h')

  -V, --version
          Print version

NixOS / Nix flake

The repository is a Nix flake. Steam auto-detection is disabled in the Nix build (it would require libsteam_api.so at runtime), so you always pass the megapicker path explicitly.

Build and run the patcher directly:

nix run github:<owner>/jackbox_megapicker_patcher -- \
  "/path/to/The Jackbox Megapicker" \
  --game 3364070=/data/jackbox/pack11

Or, for local development: nix build, nix develop.

Declarative configuration (home-manager / NixOS)

Both a home-manager module (homeManagerModules.default) and a NixOS module (nixosModules.default) are exposed. They let you declare each game's directory and generate a pre-configured jackbox-megapicker-patch command. Patching mutates the Steam install in place, so the command is not run automatically on rebuild — you run it yourself after (re)installing the megapicker or adding a game.

# flake.nix
{
  inputs.jackbox.url = "github:<owner>/jackbox_megapicker_patcher";

  # In your home-manager configuration:
  # imports = [ jackbox.homeManagerModules.default ];
  # (or, system-wide: imports = [ jackbox.nixosModules.default ];)

  programs.jackbox-megapicker-patcher = {
    enable = true;
    megapickerPath = "/home/alice/.local/share/Steam/steamapps/common/The Jackbox Megapicker";
    games = {
      "3364070" = "/data/jackbox/pack11"; # The Jackbox Party Pack 11
      "2748040" = "/data/jackbox/pack10"; # The Jackbox Party Pack 10
    };
    launchArgs = [ "-fullscreen" ]; # applied to every game
    gameLaunchArgs = {
      "3364070" = [ "-jbg.config" "foo=bar" ]; # only Pack 11
    };
  };
}

Then run jackbox-megapicker-patch (the raw jackbox_megapicker_patcher binary is installed too).

To re-apply the patch automatically after Steam updates the megapicker, wire the exposed config.programs.jackbox-megapicker-patcher.patchCommand into a home.activation script and a systemd.user.path unit watching <MEGAPICKER>/resources/app.asar.