Slabbed — Mixin Target Discovery (MC 1.21.11 / Yarn)

Goal

Identify and lock the correct Yarn-named classes/methods to hook for Slabbed’s core behavior:

• •placing things “on top of a slab like ground”
• •keeping them from popping off due to survival checks / neighbor updates

No behavior changes in this skill. Output is a target list + plan.

Non-goals

• •No new mixins added
• •No injections performed
• •No refactors

Inputs / assumptions

• •MC: 1.21.11 (Fabric)
• •Yarn mappings in project already working
• •Slab types: bottom slab / top slab / double slab
• •Rule: treat the top face of a slab as “ground”

Steps

0) Safety checkpoint

• •git status must be clean. If not, stop.

1) Make sure sources are available

Run:

• •./gradlew genSources (if needed)
• •Confirm IDE can navigate into net.minecraft sources

2) Locate vanilla “support” predicates

Using IDE “Find in files”, search for these terms (in net.minecraft sources):

• •canPlaceAt
• •getPlacementState
• •canPlaceOn
• •canPlantOnTop
• •isSideSolidFullSquare
• •isFullCube
• •getCollisionShape
• •getOutlineShape
• •getSidesShape
• •getStateForNeighborUpdate

For each promising hit, open call sites and trace who checks “solid top” or “full square”.

3) Identify slab shape semantics

Locate the SlabBlock implementation and record:

• •property names (e.g., TYPE)
• •how top/bottom/double shapes are represented
• •helper methods used to determine support on the upper face

Output:

• •SlabBlock class name (Yarn)
• •SlabType enum name (Yarn)
• •Methods used to compute shape/support

4) Build a target matrix of “things that pop off”

Pick 6 canonical test blocks (don’t implement, just list):

• •torch (floor)
• •redstone dust
• •repeater
• •rail
• •pressure plate
• •carpet

For each, locate its survival predicate:

• •class + method that performs support check (usually canPlaceAt or neighbor update path)
• •what it checks on the block below (pos.down())

Record for each:

• •Yarn class name
• •method signature (Yarn)
• •the exact condition that fails on slabs

5) Classify hooks into two buckets

Bucket A: Placement-time override points
Bucket B: Survival-time override points

For each bucket, list 1–3 best candidate targets and explain why:

• •stability across versions
• •minimal invasiveness
• •avoids breaking vanilla rules

6) Propose ONE primary strategy (pick one)

Choose the most robust approach and write a short plan:

Possible strategies (examples):

• •(S1) Patch “support test” helper(s) that most blocks rely on
• •(S2) Patch slab block to present a solid top face to support checks
• •(S3) Per-block targeted mixins (last resort; strict visuals may require)

Pick one as “Primary”, and list “Fallbacks”.

7) Output deliverable

Produce a Target Plan in this exact format:

• •Primary strategy: S?
• •Placement hooks:
  • •YarnClass#method(signature) — why
• •Survival hooks:
  • •YarnClass#method(signature) — why
• •Per-block exceptions (if any):
  • •block → target(s)
• •Risk notes:
  • •3 bullets
• •Next step mixins to create:
  • •filenames under src/main/java/com/slabbed/mixin/

8) Stop

Do not implement changes. Do not create mixin files. No commits.

Pass criteria

• •At least 1 credible Primary strategy with concrete Yarn targets for both placement and survival
• •At least 6 block examples traced to their predicates
• •Output plan is complete and actionable