AccessWidener

Open up private / protected / final Minecraft members at runtime — the scripting equivalent of a Fabric access widener, but applied live from a Tessera module. A widened member becomes public (and loses final), so scripts can then read/write/call it through the normal API (GraalJS host access or the bytecode engine).

import { AccessWidener } from 'ratph6.tessera.api';

AccessWidener.widenField('net.minecraft.client.Minecraft', 'gameMode');   // read a private field
AccessWidener.widenMethod('net.minecraft.client.Minecraft', 'setScreen'); // call a private method
AccessWidener.makeExtendable('net.minecraft.world.entity.Mob');           // drop final on a class

Important — timing. The JVM only permits access changes while a class is being defined. So a widening takes effect only on a class that is not yet loaded when you register it. Targeting a class that is already loaded (e.g. Minecraft, which loads at startup) logs a note and does nothing this session — register such widenings as early as possible (top of your module), or restart. Use /te errors to see if a widening came too late.

Like Mixin this needs runtime instrumentation; widenings are reverted on /te reload / module unload (they reapply on the next class load).

Already-loaded classes

Bytecode widening (widenField/widenMethod/makeExtendable) only works on classes not yet loaded. For classes that are already loaded (e.g. Minecraft, KeyMapping, Options — all created at startup), use the reflection accessors below instead: getField/setField/invoke and their static variants reach private members on any object, loaded or not, with no restart.

// bump a private int counter on the already-loaded KeyMapping — no restart, no widenField:
const keyUse = Minecraft.getInstance().options.keyUse;
AccessWidener.setField(keyUse, 'clickCount', AccessWidener.getField(keyUse, 'clickCount') + 1);