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Launching Minecraft

To launch Minecraft with your mod installed, you can choose the "Minecraft Client" task in your Run Configurations list - it's recommended you launch in "Debug" mode as this will allow you to hotswap methods and create breakpoints where possible.

If the run configurations don't exist, reload the project. If they still dont exist, you can alternatively use the gradlew runClient command instead. This is not recommended though as hotswapping and various debug tools are not available.

You should see the game launch in development mode - you are unauthenticated and cannot join any online servers in this mode:


If you need to log into an actual account instead of being stuck in offline mode, you can utilize the "DevLogin" library by PlanetTeamSpeakk

Simply add the following to the build.gradle file found in the root of your mod project:

repositories {

  // ...

dependencies {
  modImplementation "com.ptsmods:devlogin:3.3"

  // ...

Next, you'll need to add the --msa-nostore argument to your "Minecraft Client" run configuration:

Now, when launching the game, you will be prompted to authenticate with Microsoft.

If you wish to store the authentication token, simply replace --msa-nostore with the --msa argument. This is not recommended though.

Hot Swapping

Hot Swapping is only available when the run configurations are ran in "Debug" mode - even then, you're still quite limited:

  • You can't add or remove methods
  • You can't change method parameters
  • You can't add or remove fields

Hot Swapping Mixins

If you wish to hot-swap mixins, you need to mark the mixin jar library as a java agent.

1. Locate the Mixin library jar.

In IntelliJ IDEA, you can find the mixin library jar in the "External Libraries" section of the "Project" section:

You will need to copy the jar's "Absolute Path"

2. Add the -javaagent VM argument.

In your "Minecraft Client" and or "Minecraft Server" run configuration, add the following to the VM Arguments option:

-javaagent:"path to mixin library jar here"

Now, you should be able to modify the contents of your mixin methods.

Not affiliated with Mojang Studios or the Fabric Project.