slabbed-minimal-hook-implementation-playbook

name	slabbed-minimal-hook-implementation-playbook
description	Implement one minimal end-to-end slab support slice (placement plus survival) and tag the result.

Slabbed — Minimal Hook Implementation Playbook (One Block, End-to-End)

Goal

Implement the smallest complete vertical slice:

• ONE “object” category works on slab tops
• includes both placement and survival (no pop-off)
• strict visuals (correct height/shape)
• minimal invasiveness
• savepoint tagged

Recommended first block category: floor torch (small surface + simple support logic)

Non-goals

• No “all items” yet
• No broad sweeping hooks unless proven safe
• No performance tuning beyond “don’t spam logs”

Preconditions

• slabbed-mixin-target-discovery completed and provides concrete Yarn targets
• slabbed-test-matrix-and-repro-world exists and repro lanes are ready
• Working branch is clean
• ./gradlew build currently passes

Step 0) Create a working branch

• Branch: feat/torch-on-slabs
• Confirm clean status

Step 1) Add SlabSupport helper (if not already)

Implement com.slabbed.init.SlabSupport per slabbed-slab-support-helper-contract.

Do NOT add extra behavior. Keep it generic to “top support”.

Step 2) Add ONE mixin for placement

Using the Yarn target plan:

• Create ONE mixin file (placement-time for torch)
• Hook should only widen “supported on top” when below is slab top face

Rules:

• Keep injection narrow (one method)
• Avoid redirecting huge helper methods unless necessary
• If you must intercept a predicate, do it at the closest call site for torch placement

Step 3) Add ONE mixin for survival

Add ONE mixin that prevents torch breaking due to slab support:

• Hook the torch’s canPlaceAt (or equivalent survival predicate) to allow slab-top support

Ensure:

• it still breaks when truly unsupported (air, liquids, etc.)
• it still follows vanilla where appropriate

Step 4) Strict visuals sanity

Validate that the torch visually sits on slab top:

• bottom slab: torch base at y+0.5
• top slab: torch base at y+1.0

If visual mismatch exists due to vanilla model assumptions:

• stop and report the exact mismatch
• do not hack around with unrelated rendering changes yet

Step 5) Test the vertical slice

Run the test matrix only for the torch category:

• Full blocks lane must still pass
• Bottom slab lane must pass
• Top slab lane must pass Run update triggers:
• neighbor update
• chunk unload/reload

Step 6) Savepoint

If torch passes:

• ./gradlew build
• commit message: feat: allow floor torches on slab tops
• tag: slabbed-first-placement-pass

If survival also passes after updates:

• add second commit if needed: fix: prevent torch popping off on slab updates
• tag: slabbed-first-survival-pass

Output report format (required)

• Strategy used (1 line)
• Yarn target(s) touched (class#method)
• Files changed
• Test result summary (torch only)
• Commit hash(es) + tag(s)

Stop conditions

• If any mixin target is missing (“no targets”): stop and rerun discovery
• If torch works but breaks another block in baseline lane: revert to last tag and reduce scope