Slabbed 0.5.1-alpha.1 for Fabric 1.21.11

The largest update this line has shipped — 116 commits since 0.5.0-beta.8. The placement core was rebuilt around a single idea: a block's height is computed once, when you place it, and then frozen — recorded in the world save itself, immune to anything that happens around it later. Alpha status reflects the size of that rebuild, not its test coverage: 389 gametests plus client-side proofs run green on every build.

⚠️ BACKUP YOUR WORLDS!

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Some blocks will shift down half a block when upgrading an existing pre-0.5.1 world. This may cause unexpected, permanent effects.

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Slabbed now lets a block rest lower in three cases where it previously stayed flush. Blocks placed before this version carry no saved height, so they follow the new rule the first time they load:

• a carpet resting directly on a bottom slab
• powder snow resting directly on a bottom slab
• a top slab resting directly on a bottom slab

Each now sits half a block lower than on beta.8. Nothing is deleted or relocated — the same builds simply render and collide the way they would if placed today. Measured by resolving identical layouts on both versions: three of thirteen legacy layouts differ, all by −0.5, all downward. If a beta.8 build depends on those staying flush, back it up before upgrading.

The core change: placement is permanent

• Every block item placement records its height at placement time, atomically. Where a block lands is where it stays — breaking its support, building next to it, reloading, or restarting changes nothing. This closes the long-standing family of pop/snap bugs at the root instead of case by case. (Enforced by a blocking invariance matrix; support removal, reload and full-restart persistence confirmed live.)
• A lowered placement that qualifies for no anchor still records its height — protection no longer depends on a lucky classification.
• A block placed flat stays flat, whatever kind of block it is; in-place transforms (grass → dirt, crop growth, waterlogging) keep the recorded height; removal clears only the removed block's record.
• Same-item merges (a second candle, sea pickle, snow layer) preserve the cell's recorded height instead of re-deriving it.

Placement accuracy

• Scaffolding works correctly with Slabbed installed (#65): side-click stacking lands on top of the column, placing upward from inside scaffolding no longer creates an invisible untargetable block, and stacking on a lowered column follows the column's real seat.
• Placing into a replaceable cell (grass, ferns, flowers, one-layer snow) no longer records a wrong height a full cell up or down.
• Slab top-edge and corner clicks place on top of the slab instead of deflecting to the side. (Live-confirmed.)
• Clicks on the visible face of a lowered block are accepted at the server's own validation seam, so what you can see and aim at is what the server lets you build against.
• A slab seats on a bottom slab's top face; a slab may lower onto a slab that is itself sunk; a follower can never sink into its own support; followers inherit their support's actual height rather than a guessed constant.
• Seat decisions ask geometry, not block class: a seat is a face rather than a volume, a TOP or DOUBLE slab counts as a seat, "hanging" is judged by whether a block is hanging rather than whether its type could be, and a plain full block on bare Terrain Slabs no longer earns a spurious anchor and snap.

Targeting

• The pick window widened to ±2 blocks with its radius derived from the active depth cap, so lowered blocks stay targetable across the whole supported range.
• Escape hatch: -Dslabbed.offsetRaycast=false restores vanilla picking entirely.

Terrain Slabs compatibility — improved, not complete

• Player-placed Terrain slab heights are preserved exactly, and a Terrain slab placed onto an already-lowered block continues the surface at the same depth. (Live-confirmed with the original Terrain Slabs 3.3.0.)
• Floor objects (torches, levers, repeaters, comparators) seat on Terrain slab surfaces; hanging objects follow Terrain underside planes.
• Terrain-Slabs-owned vegetation and snow get exactly one offset — Terrain Slabs' own — whether the surface underneath is natural or player-placed.
• Carpets follow their support, and potting a flower no longer moves the block above it.

Stability and rendering

• Fixed a client crash while meshing chunks on Terrain-slab-dense terrain. beta.8 guarded one renderer-boundary read; the rest of the resolver could still walk past the region edge on a mesh worker and crash the game on world load. Every resolver read is now bounded, ending the lookup at the region edge. (Reproduced live on a Terrain worldgen world; fix confirmed on the same world.)
• Chunk-seam culling compares real heights instead of booleans, fixing see-through seams on back rows, and its eligibility follows geometry rather than anchor membership.
• Dependent chunk remeshes are coalesced and prioritised, bounded per tick.
• Lever use particles align with the lever's frozen height, joining the earlier torch, candle, brewing-stand and pot particle fixes.

Multiplayer and world data

• Fixed a chunk that could fail to load once it accumulated roughly 2,048 height markers (#38): the sync format now groups positions by chunk section, keeping even a fully dense chunk under the engine's attachment size ceiling — and at the true limit the store declines a new record instead of corrupting the chunk.
• Vanilla redstone wire connections restored on lowered supports (#37).
• Bottom-slab mob proofing restored (#39).
• Loading a pre-0.5.1 world writes nothing into it: old saves stay byte-clean of Slabbed data until you place something new. (Verified at the region-file level.)

Notices, tooling, packaging

• The join notice now describes the build it is on — this version greets you with alpha, not beta — and the wording can no longer drift from the version.
• /slabdy (the height-readout overlay) ships in every build and is off by default; toggle it with /slabdy. Its readout shows cached versus freshly-computed heights for the target and its support.
• Test, recorder and rig tooling never ships: the release jar is gated by a closed-world allowlist, and both jars are scanned for stray content before release.

Known limits

• The supported lowering floor is one full block (−1.0). A deeper range exists behind an explicit per-world opt-in, for development only.
• A custom Terrain Slabs slab placed directly on top of a vanilla slab still does not lower; the reverse works.
• Side-clicking certain legacy lowered slabs (placed before this version, in specific side-by-side arrangements) can silently place nothing. Being traced; a fix will follow.
• #36 (0–1 FPS) did not reproduce in controlled testing against beta.8 and remains open pending reporter follow-up.

Every 1.21.11 Fabric report filed on GitHub

Reports confirmed against Minecraft 1.21.11 Fabric, credited to their reporters. Issues filed against other versions or loaders are tracked separately and are not listed here.

👾 Changelog written by AI, edited by Peetsa

Slabbed 0.5.0-alpha.1 for Minecraft 26.2

⚠️ A heads-up before you update

This alpha finally locks in a block's height the moment you place it — no more slow pop-in, no more things drifting or flickering after you've already built them. It's the biggest fix I've made since I started this mod back in February, and it's the reason this build is worth trying.

The tradeoff: that locked-in height only starts existing for blocks placed under this version. If you open a world you built on an earlier version, anything you'd already lowered won't carry that forward — it'll look like it was placed at normal height instead. Nothing is deleted or broken, it's a visual/behavior reset for blocks placed before this update, not data loss.

Please back up any world you care about before opening it in this build.

If you want your existing world to stay exactly as it is for now, just hold off and keep playing on your current version — try this one on a copy, or a fresh world, first.

I'm looking into fixing this for existing worlds automatically in a follow-up build. In the meantime, if you're comfortable editing your launcher's JVM arguments, adding -Dslabbed.frozenDy=false restores the old behavior.

This is an alpha because I want real feedback before I call anything stable — if something looks wrong, tell me. Thanks for testing.

Full details for everything below are in "Known limitations and alpha testing request."

New

• Your block stays where you put it. A placed block's height is now decided at the moment you place it and locked in from then on. Nothing that happens nearby afterwards — breaking a neighbor, placing next to it, updates rippling through the area — will ever move a block you already placed. This is the headline change of this build, it is on by default, and it has been confirmed in live play, including specifically testing that removing a lowered block's own support does not pop a block placed on top of it. This does change how existing worlds look — read the first item under Known limitations before you open one.
• Build deeper. Stepped-down slab arrangements are no longer stopped at one full block below grid level; towers can now keep lowering past the old limit. Confirmed in live play down to two and a half blocks below, including a crash-free deep-tower stress pass.
• World-join notice. Joining a world now shows a short notice reminding you that you are on a pre-release build, and its dismiss option now reports honestly instead of claiming success when it could not apply.

Improved

• Blocks land where you aim. The landing logic for slabs and full blocks was rebuilt so that the spot you aim at is the spot you get, and side placements deep below grid level are no longer rejected by the server. Confirmed in live play.
• Chains and dripstone under lowered ceilings. Continuing a chain or dripstone run from a lowered slab behaves much better: new links line up with the existing run instead of drifting, a chain placed against a flush ceiling no longer ends up half a block too high, follow-on links well below the surface are accepted, side-aimed placements pick the correct half, and dripstone continues correctly both upward and downward — including when you click its side. Confirmed much improved in live play; a few scenarios, including chains placed against a flush ceiling and the deepest runs, are still being verified (see Known limitations).
• Clicking into visible space works. When a block renders below floor level, clicking its top face now places into the open space you can actually see instead of refusing the click. Confirmed in live play.
• A wave of ported stability fixes. The stability campaign from the 1.21.11 line is now in this build: torches, fences, walls, and bottom slabs sit correctly on lowered top-slab carriers; vertical slabs keep their anchoring and never pop; and Terrain Slabs blocks are never mistaken for Slabbed carriers, with the overhang traversal logic guarded accordingly. Confirmed together in a live session.
• Terrain Slabs compatibility. Deferring to Terrain Slabs' own "on-top" blocks now covers everything Terrain Slabs treats that way, not just vegetation. Verified by automated tests.
• Placement-state hardening. A broad defensive pass tightened how placement-time state is captured and preserved — height read-back, waterlogging symmetry, freeze handling for connecting blocks, marker hand-off, and more. To be clear about credit: the day-to-day stability you will feel comes chiefly from the locked-in placement height described under New; this pass hardens the same placement-time data that feature relies on.
• Leaner world sync. The data that carries placed-height information in chunk sync is now compacted. Verified by automated tests. (This is the same change that fixes the chunk-loading failure below.)
• Cleaner release jar. Development-only diagnostics are now separated out of the normal release jar.

Fixes

• Worlds no longer fail to load after dense slab building (reported as issue #38). A chunk holding enough placed slabs could exceed a size limit and refuse to load, taking that part of the world with it. The placed-height data is now stored compactly so it stays well under the limit. Verified by automated tests.
• Mobs no longer spawn on bottom slabs (reported as issue #39). Slab mob-proofing behaves like vanilla again. Verified by automated tests; a long overnight spawn check has not been run.
• A significant rendering slowdown is fixed. Reading a block's locked-in height on the render path no longer takes a shared lock or allocates memory for every block in view, and rendering blocks near a lowered surface no longer routes through reflection. Confirmed smooth in live play across ordinary building, chunk loading, and a dense build; no formal benchmark comparison was run, so please still report performance issues per the request below.
• Standing signs of every wood now sit flush on a lowered slab. Previously only oak did; every other wood's standing sign could float above the surface instead of resting on it.
• Overlap protection. Placements that would interpenetrate a lowered block already occupying that space are now refused — including the case of placing through an open trapdoor — while legitimate edge-contact placements still work. Confirmed in live play.
• Hoppers and chests no longer snap. Hoppers, chests, and similar flat block entities hold their placed height instead of snapping to grid. Confirmed in live play.
• Stale visuals refresh promptly. The rendered shape of blocks near a height change now updates right away instead of showing an outdated shape — including with Sodium, where the correction could previously take up to about 30 seconds — and fences, walls, and iron bars connect visually without delay. (The blocks themselves never moved; this fixes the picture catching up to reality.) Verified in live sessions.
• Particles sit at the right height. Lowered candles, candle cakes, brewing stands, wall redstone torches, and decorated-pot insert bursts now spawn their particles at the lowered model instead of half a block above it (the remaining particle fixes ported from the 1.21.11 line).
• Copper chain texture. A bridged copper chain under a slab ceiling no longer renders with the plain iron chain texture. Confirmed in live play.

Known limitations and alpha testing request

Three blanket caveats up front:

• ⚠️ If you open a world you built on an earlier version, its previously lowered blocks will look flat.

Height is now decided and locked in the moment you place a block, but only going forward

• a block placed under an earlier version has no such record, and this build does not fall back to recomputing its height live the way older versions did. The block itself is not moved or damaged, and anything you place from now on will lower and lock in correctly; it is specifically already-placed lowered blocks that will render and behave as if they were never lowered. There is no automatic conversion for existing worlds, and this also applies to lowered-looking blocks from world generation, /setblock, or another mod. Back up any world before opening it in this build, and consider testing on a copy or a fresh world first.
• Broad mod compatibility is an unverified alpha risk. Running this build inside large modpacks has not been broadly tested.
• No formal performance benchmark was run. A significant render-path slowdown was found and fixed this build (see Fixes), and normal play has felt smooth since, but nothing here is a measured performance guarantee — please treat it as an open question and report anything that feels off.

The following changes shipped in this build pass their automated tests but have not yet been fully re-verified in live play. They should be improvements — please treat them as "being verified," not "done," and report anything odd:

• Client and server agreeing on placement height at the instant of placement (this targets the brief flicker some placements showed).
• Ordinary objects such as flower pots landing at the aimed height.
• Interacting with deeply lowered blocks — empty-hand use, use while holding an item, and powder-snow contact — no longer being rejected by the server.
• Deep placements being validated against the actual slab shapes rather than a coarse approximation.
• Potted-plant changes (for example, planting into an empty pot) keeping the pot's placed height.
• Lever, powered redstone wire, and use-created fire particles seating at the lowered height.
• Chains placed against a flush ceiling landing at the corrected height, and the deepest chain and dripstone continuation cases (runs continuing well past one block down).

Known open issues:

• In some deep arrangements, a hanging chain can still render at the wrong height even though its targeting outline and collision are correct.
• A connected dripstone's second segment at depth may still misbehave; this is parked for a follow-up build.
• In certain deep arrangements, a few block families — doors, carpets, banners, and beds — may still land at grid height rather than the lowered height (powder snow intentionally never lowers). Per-family placement height is ongoing work.
• Redstone dust carries a signal up a lowered step but not back down it. This looks like an existing vanilla quirk made more visible by the mod's lowered blocks rather than something the mod itself is doing, but it has not been fully root-caused — and a fix applied before it is properly diagnosed risks breaking dust connections that currently work correctly, so it is deferred rather than rushed.

☞ How you can help — alpha testing request.

If you hit a problem, the most useful report includes:

• Reproducible steps — what you placed, where, and in what order, so I can recreate it.
• Your full mod list (and loader version).
• Your latest.log, or the crash report where one was produced.
• A screenshot or video of the problem.
• For performance reports: a comparison of the same scene with Slabbed enabled versus disabled — a report that says "lag with the mod on AND off" versus "lag only with the mod on" is worth ten times a bare "it lags."

If I need extra detail on a specific report, I may send you a separate diagnostics build to reproduce it with — the normal release jar you have now carries none of that tooling.

Thank you for testing an alpha — every report above makes the next build better.

Slabbed 0.5.0-beta.8 — Minecraft 1.21.11 Fabric

Fixed

• Fixed a client crash that could occur while Minecraft rebuilt chunk meshes near a renderer-region boundary. Beta.7 used a development-only class name when recognizing the bounded renderer view, so production could rethrow an expected out-of-region lookup instead of ending the scan safely. Beta.8 uses a mapping-safe renderer check.

Verification

• Reproduced and regression-tested the production mapping failure.
• Tested visible rain, repeated short-grass mesh rebuilds, and chunk unload/reload without recurrence.
• Rechecked and closed the already-fixed fence-gate visual report (#12) and Terrain Slabs log-carrier report (#22).

Rain appears to have triggered or coincided with the rebuild that exposed #35; it was not the direct cause. The reported blue flashes and 0-1 FPS behavior were not independently proven and should be re-reported with a fresh log if they remain after beta.8.

0.5.0-beta.7 — 1.21.11 (Fabric)

Fixed

• Redstone repeaters and comparators can now be placed on a Terrain Slabs bottom slab (this also generically fixes any other block whose placement depends on the same solidity check — buttons, pressure plates, rails, etc.)
• Decorative objects (candles, trapdoors, and similar) resting on a slab, fence, or other support no longer pop back to full height when that support is broken
• Lowered brewing stands emit their ambient smoke particles at the correct height instead of full block height
• Stashing an item into a lowered decorated pot spawns its particle burst at the correct height instead of full block height
• A hanging lantern under a Terrain Slabs slab no longer hangs too low, leaving a gap
• A slab placed beside a lowered full block no longer has an invisible side face (#24)

Added

• A brief one-time notice reminding you Slabbed is in beta, with a clickable [Don't show again] link. Dismissing it only silences it for that specific world — a different world you haven't dismissed it in will still show it once.

Changed

• The /slabdy target-height overlay is now off by default. It still ships with the mod and can be turned on any time with /slabdy, but it no longer shows on-screen unless you ask for it.

Security

• Fixed a leak in an internal dev tool where its output file could contain live Microsoft account credentials. This tool is not part of a normal build, so it never affected regular play, but it's been fixed and additionally removed from release builds entirely.

All fixes above have been confirmed on a live test build before this release.

[0.4.2-beta.2] - Minecraft 1.21.1 (NeoForge)

Carries the 0.4.2 parity-candidate work for this port plus a render-path performance cleanup. Build metadata was corrected from +26.2 to +1.21.1, the actual target Minecraft version.

Performance

• Removed always-on per-block work from the chunk-mesh render path: the full-mesh-bounds diagnostic sampler no longer does a block-registry lookup, string allocations, and an atomic increment per block before checking its trace flag.
• The per-vertex bounds loop is now skipped entirely unless the trace is armed.
• Render trace flags are read once at class-load instead of per block; render.offset.trace stays live but is gated cheap-first.
• This is zero behavior change and matters most under Sodium, which routes all block geometry through this path.

Developer

• /slabdy overlay now starts off by default in release/profile launches.
• It remains toggleable in-game, but the initial state is false unless explicitly enabled with -Dslabbed.targetDyOverlay=true.

Known limitations

• A face-culling / shadow artifact beside a lowered full-block ↔ vanilla-slab boundary is deferred to a later render/culling slice.
• Full Terrain Slabs named-surface support is not in this build; Terrain Slabs blocks are kept un-offset and otherwise behave as vanilla support.
• No all-item or all-partial-block support claim is made for this beta.

Slabbed 0.4.2-beta.1 for Minecraft 1.21.1

This beta rebuilds the 1.21.1 line with the latest Slabbed support fixes and release-jar cleanup.

Fixed

• Fixed the severe lag spike caused by repeated missing diagnostic-class lookups during rendering.
• Fixed chain visual/selection alignment so lowered chain setups keep model, outline, and targeting in sync.
• Fixed pointed dripstone combine behavior on lowered Slabbed targets.
• Fixed Terrain Slabs compatibility for placed bottom slabs:
  • full blocks can stack flush without gaps
  • floor-standing objects now sit flush on supported Terrain Slab bottom slabs
  • genuine hanging objects and ceiling chain geometry remain unchanged
• Fixed object placement on flat Terrain Slab bottom surfaces.

Improved

• Added better /slabdy diagnostics for testing lowered-state source, dy, target half, and supporting block state.
• Cleaned the packaged release jar so proof/debug/test helpers do not ship in the runtime artifact.

Notes

• Terrain Slabs generated/self-rendering quirks remain Terrain Slabs-side behavior where Slabbed reports dy=0.
• This is a beta release; please report any weird placement, targeting, or visual alignment issues with screenshots and the block setup.

Backports Slabbed 0.4.2-beta.2 to Minecraft 26.1.

• Restores the latest beta.2 slab placement fixes on Minecraft 26.1, including pointed dripstone stacking on slabs and attaching underneath lowered bottom slabs.
• Keeps the target-dy debug overlay off by default; it can still be enabled with /slabdev debug when needed.
• Fixes the chain ceiling support model path so Sodium/Fabric do not warn about an undiscovered Slabbed extra model during resource reload.

DEPRECATED

Please download the latest NeoForge version 0.4.2-beta.2+1.21.1 for the performance fix.

This NeoForge build brings the Slabbed 0.4.2-beta.1+26.2 line to Minecraft 1.21.1. (Woohoo! 🎉)

Highlights:

• Added the NeoForge 1.21.1 release jar for Slabbed 0.4.2-beta.1+26.2.
• Improved WYSIWYG slab-supported placement so models, outlines, and targeting line up more reliably.
• Fixed fence placement and chaining cases around lowered/flat slab lanes while preserving legal vanilla connections.
• Fixed lanterns on chains so the lantern behaves like an add-on below the chain instead of merging into it.
• Fixed pointed dripstone combining on slab-supported placements, including standing and hanging cases.
• Fixed lowered redstone torch smoke height.
• Removed internal proof/debug/dev helpers from the packaged runtime jar.
• Verified the packaged jar uses NeoForge metadata and does not declare or hard-link a Fabric API runtime dependency.

Still beta: weird mixed modded-block arrangements may still have edge cases. Please include screenshots or video with bug reports, especially for crosshair, outline, placement, or visual-height mismatches.