Work with the official launcher

modsmith.launcher reads and changes the official launcher’s profiles, which are the installations players choose from.

import modsmith as ms

game = ms.minecraft.GameDir.default()
launcher = ms.launcher.Launcher(game)

The launcher has to have run once, because that creates its files. Otherwise Modsmith raises modsmith.errors.LauncherError.

Add a profile

key = launcher.add_profile(
    "My Pack",
    "fabric-loader-0.16.10-1.21.1",
    "instances/my-pack",
    memory_mb=6144,
)

The arguments are the display name, the version to start and the instance folder. Modsmith stores the folder as an absolute path.

Calling it again with the same name updates the profile, and keeps any fields you did not set. Use the returned key to find the profile later.

Add an icon

from pathlib import Path

if Path("icon.png").is_file():
    icon = ms.launcher.icon_data_uri(Path("icon.png").read_bytes())
    launcher.add_profile("My Pack", "1.21.1", "instances/my-pack", icon=icon)

List and remove profiles

for key, profile in launcher.profiles().items():
    print(key, profile.name, profile.version_id, profile.game_dir)

launcher.remove_profile("modsmith-my-pack")

Keep the launcher closed

The launcher can overwrite its files while it runs, so close it before changing profiles. You can warn the player:

if ms.launcher.is_running():
    print("Please close the Minecraft Launcher first.")

Note

is_running is a best-effort check. Treat it as a reason to warn the player, not as a guarantee.

Modsmith saves a backup of each file before changing it, next to the original, with the suffix .modsmith.bak.