Jar Stacker v0.7.0

Jar Stacker 0.7.0 Release Notes

Release Version: 0.7.0
Release Date: September 15, 2026
Target Platform: Fabric Loader (>=0.19.3)
Supported Minecraft Versions: Minecraft Java Edition 1.21.1 through 26.2

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Highlights

Jar Stacker v0.7.0 is our largest update yet, expanding entity stacking and logical virtualization across the entire modern Minecraft lifecycle—from Minecraft 1.21.1 through 26.2.

• Full Multi-Version Support (1.21.1–26.2): 9 dedicated compile artifacts covering 15 distinct Minecraft versions with 100% test parity.
• Latest Entity Wins Item Stacking: Dropped items smoothly consolidate into the newest item with natural Vanilla physics, preserving exact position and flight velocity with zero survivor teleportation or visual pop.
• Adaptive 2/10 Scan Cadence: High-frequency 2-tick scans for moving and freshly spawned items during mining, paired with an ultra-lightweight 10-tick baseline for settled items.
• Complete Per-Logical-Entity Status Effects & Persistent Burn: Independent duration, amplifier, and fire tick counters per stacked mob, with exact death and hurt callbacks for event-driven effects (INFESTED, OOZING, WEAVING, WIND_CHARGED).
• Real Daylight Sunlight & Environmental Ignition: Stacked undead mobs naturally detect and respond to real Vanilla sunlight and environmental hazards with zero desynchronization.
• Native Combat & MC-3304 Parity: Decoupled weapon Looting evaluation, sweeping edge damage propagation, and projectile kill credit matching native Minecraft.
• 100% Automated Matrix Verification: All 15 supported runtimes pass our comprehensive 360-test automated server suite (5,400 / 5,400 tests passing).

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Minecraft Compatibility & Artifact Matrix

Important

Install ONLY ONE Jar Stacker JAR matching your Minecraft version. Do not install multiple Jar Stacker JARs simultaneously.

Minecraft Version	Required Mod Artifact	Java	Status / Details
1.21.1	jarstacker-0.7.0+mc1.21.1.jar	Java 21	Dedicated Target (Loom Remap)
1.21.2 – 1.21.3	jarstacker-0.7.0+mc1.21.2.jar	Java 21	Compatibility Band Anchor
1.21.4	jarstacker-0.7.0+mc1.21.4.jar	Java 21	Dedicated Target (Loom Remap)
1.21.5	jarstacker-0.7.0+mc1.21.5.jar	Java 21	Dedicated Target (Loom Remap)
1.21.6 – 1.21.8	jarstacker-0.7.0+mc1.21.6.jar	Java 21	Compatibility Band Anchor
1.21.9 – 1.21.10	jarstacker-0.7.0+mc1.21.9.jar	Java 21	Compatibility Band Anchor
1.21.11	jarstacker-0.7.0+mc1.21.11.jar	Java 21	Dedicated Target (Loom Remap)
26.1 – 26.1.2	jarstacker-0.7.0+mc26.1.jar	Java 25	Compatibility Band Anchor (Unobfuscated Loom)
26.2	jarstacker-0.7.0+mc26.2.jar	Java 25	Dedicated Target (Java 25, EntityTypes, Unobfuscated Loom)

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What's New & Improved

1. Item Stacking UX ("Latest Entity Wins")

• Natural Motion Preservation: Newly mined drops retain their natural position, trajectory, and momentum. The newest entity becomes the physical survivor, eliminating jarring anchor snaps back to old piles.
• Adaptive Cadence: Items in motion or recently spawned (age <= 40) are evaluated every 2 ticks (~100 ms), delivering immediate merge responsiveness during rapid block breaking while maintaining minimal tick overhead on settled piles.
• Visual Smoothness: Operates strictly through native entity state without fragile client-side render interpolation or lerp offsets.
• Clean Nametags: Clean single-item display hides floating labels for unstacked items (count == 1), preserving pure Vanilla visuals.

2. Mob Stacking & Logical Virtualization

• Strict State Invariant: Guaranteed count balance: $\text{logicalCount} == \text{healthRecordCount} == \text{statusRecordCount} == \text{burnRecordCount}$.
• Compile-Time Typed Variant Safety: Typed compatibility checks across all 16 Vanilla variant entities (Mooshroom, Cow, Pig, Sheep, Wolf, Cat, Frog, Horse, Llama, Rabbit, Fox, Axolotl, Parrot, Salmon, Tropical Fish, and Villager professions).
• Fail-Safe Unknown Variant Policy: Custom or modded mobs with unknown variant semantics safely fail closed (UNKNOWN_VARIANT_COMPATIBILITY), preventing silent attribute desynchronization.
• Dynamic Equipment Extraction: Mobs picking up damageable weapons or armor automatically extract the active member as an independent singleton, protecting durability mechanics and preventing exploits.
• Separated Lifecycle Groups: Dedicated grouping for breeding readiness, mating cooldowns, baby maturity progression, and single-increment sheep wool regrowth.

3. Combat Attribution & Death Parity

• Decoupled Combat Context (CombatDeathContext): Full player attribution, damage type tracking, and enchantment levels matching native Vanilla mechanics.
• MC-3304 Parity: Projectiles (arrows, tridents) and player-ignited TNT evaluate the player's held weapon at the exact moment of impact/death.
• Sweeping Attacks: Primary targets receive full weapon Looting and damage; sweeping attacks propagate secondary sweep damage cleanly across stack members.
• Multi-Death Batching: When $K$ members die from high-damage attacks (explosions, sweep strikes), loot and XP are awarded exactly $K$ times without mass physical entity spawning.

4. Logical Status Effects & Persistent Burn

• Authoritative Classification: All Vanilla status effects classified into 7 behavior classes, verified with 0 unknown and 0 unsupported effects across the entire registry.
• Event-Driven Parity: Native hurt callbacks for INFESTED (spawning silverfish); native death callbacks for OOZING (spawning slimes), WEAVING (placing cobwebs), and WIND_CHARGED (triggering wind bursts).
• Persistent Burn Countdown: Logical members store independent remainingFireTicks. Fire damage ticks authoritatively every 20 ticks unless protected by Fire Resistance.
• Daylight Sunlight Detection: Undead stacks accurately check daytime and sky clearance, igniting and sustaining fire with full physical-logical continuity.

5. In-Game Configuration GUI & Commands

• Seamless configuration UI powered by YetAnotherConfigLib (YACL v3) and Mod Menu.
• Built-in fallback screen available when YACL is not installed.
• Real-time diagnostic inspect command (/jarstacker inspect) raycasting live entity state.

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Important Bug Fixes

• Sunlight Burn Extinguish Fix: Fixed an issue where daylight sunlight burn checks did not properly synchronize shared ignition across logical undead stack records.
• Targeted Ignition Context Isolation: Fixed fire aspect melee and flaming arrow impacts improperly spreading single-target burn to unhit stack members.
• Item Merge Discard Race: Resolved rare timing conditions where older item entities remained active after count transfer during rapid multi-pile merges.
• Attribute Modifier Staling: Fixed residual speed and strength modifiers lingering on representative mobs after active member death.

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Installation

1. Install Fabric Loader (>=0.19.3) and Fabric API for your target Minecraft version.
2. Ensure you have the appropriate Java runtime installed:
   • Java 21 for Minecraft 1.21.1 – 1.21.11
   • Java 25 for Minecraft 26.1 – 26.2
3. Download the single Jar Stacker JAR matching your Minecraft version from the matrix table above.
4. Place the .jar file into your .minecraft/mods directory.
5. (Optional) Install YACL v3 and Mod Menu to configure settings in-game.

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Upgrade Notes

• World & Save Compatibility: Jar Stacker 0.7.0 preserves the established stack and configuration formats. As with any mod or Minecraft version upgrade, back up your world before updating. Cross-version world upgrade from Minecraft 26.1.2 to 26.2 was explicitly verified with Jar Stacker state preserved.
• Downgrade Notice: World downgrades (e.g. 26.2 to 26.1 or 1.21.x) are not supported by Minecraft and are not supported by Jar Stacker. Always backup your worlds before performing major Minecraft version upgrades.

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Compatibility Notes

• Modded Entities: Authentic Vanilla entities registered in the minecraft namespace are fully supported. Custom modded entities with unknown variant mechanics safely fail closed to prevent state corruption.
• Server-Side Operation: Jar Stacker is fully functional on dedicated servers without requiring client-side installation. Clients connecting to a Jar Stacker server do not require the mod.
• Optional Client Libraries: YACL and Mod Menu are purely optional client-side enhancements; their absence has zero effect on server or client functionality.

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Known Limitations

• Modded entities that define non-standard custom NBT variants are not stacked by default unless added to explicit stacking rules.
• World downgrades to older Minecraft versions will cause Vanilla data loss and are unsupported.

Jar Stacker v0.6.0

Highlights

Jar Stacker v0.6.0 introduces the finalized Latest Entity Wins item merge architecture, sub-100ms adaptive scanning cadence, comprehensive logical status effect virtualization for mob stacks, and exact Vanilla 1.21.1 combat and Looting attribution parity (MC-3304).

Changes

1. Item Stacking Architecture (Latest Entity Wins)

• Latest Entity Wins: Compatible dropped items consolidate into the newest ItemEntity with zero survivor displacement (distMoved = 0.0). The physical newest entity retains its natural coordinates, velocity, on-ground state, and motion.
• Adaptive 2/10 Scan Cadence: High-frequency scans (every 2 ticks / ~100 ms) for active/moving items ensure rapid consolidation during mining, with an ultra-lightweight 10-tick baseline for settled items.
• Broad Configured Radius: Consolidates items within the configured radius (default: 4.0 blocks) without artificial contact-only gating.
• Clean Vanilla Visuals: Nametags are hidden on count-1 items when showCountOnlyWhenStacked is enabled.
• Removed Experimental Leftovers: Removed -Djarstacker.itemMergeMode system properties, setMergeMode hooks, stable-representative item branches, and obsolete client render transition mixins.

2. Mob Stacking & Logical Status Effects

• Per-Logical-Entity Status Effects: Independent MobEffectInstance tracking (amplifier, duration, ambient flags, particle effects) across all 39 Vanilla 1.21.1 status effects.
• Persistent Burn Counters: Fire ticks are counted down independently per member with authoritative damage ticking every 20 ticks.
• Event-Driven Parity: INFESTED triggers native hurt callbacks; OOZING, WEAVING, and WIND_CHARGED trigger native death callbacks on logical death.
• Zero Mass Entity Footprint: Splash and lingering potions affect all N logical members with O(1) physical entity footprint.

3. Combat Attribution & MC-3304 Parity

• Decoupled Combat Context (CombatDeathContext): Independently evaluates killer identity, damage source, player kill attribution, and enchantment levels.
• MC-3304 Parity: Bows, crossbows, tridents, and player-ignited TNT evaluate the player's held weapon at the moment of impact/death matching native 1.21.1 behavior.
• Dynamic Equipment Extraction: Mobs picking up damageable weapons, armor, or tools dynamically extract as autonomous singletons to protect equipment durability.

Verification & Test Results

• Automated Integration Test Suite: 343 / 343 tests passing (100%) on dedicated server environment.
• Item Invariant Tests (IM1-IM29): Validated latest survivor preservation, motion preservation, adaptive scan latency, rapid mining sequences, and real-world block drop integration.
• Client Launch Verification: Reaches title screen cleanly with zero mixin or injection errors.

Installation

• Download jarstacker-0.6.0.jar and place it in your .minecraft/mods directory.
• Requires Fabric Loader >= 0.19.3 and Fabric API for Minecraft 1.21.1.
• Optional: YetAnotherConfigLib (YACL v3) and Mod Menu for the in-game configuration interface.