In standard Minecraft, making a single typo while editing a resource pack shader forces the game to unload your entire active resource pack list. Stop Unloading My Resourcepacks (SUMR) lets you test changes rapidly in-game using a dedicated hot-reload key and automatic fallback shaders.
Setting Up the Hot-Reload Key
1. Open the pause menu and navigate to Options > Controls > Key Binds.
2. Scroll through the list to find the hot-reload key added by the mod.
3. Assign it to an unused key on your keyboard so you can trigger reloads without opening menus, then click Done.
Testing Shader Changes Live
1. Load into a world and enable your work-in-progress pack under Options > Resource Packs. Make sure the pack sits uncompressed in your resourcepacks folder so you can edit its files directly.
2. Edit and save your custom shader files or post-effect JSON files in an external text editor.
3. Return to your world and press your assigned hot-reload key.
4. If your shader contains an error, the mod keeps your pack list active by substituting default or dummy shaders and prints the exact failure on your screen so you can fix it and reload again.