ForgeMultipart/docs/migration/HISTORY.md

Migration history

Historical findings from the Scala-to-Java migration. Counts, next-target suggestions and outstanding work below describe the state at the time of each entry; use the working handoff for current state and the plan for remaining gates. Routine sessions need not read this entire log.

The former detailed per-port handoff is also available with git show cf8b2f9:JAVA_MIGRATION_HANDOFF.md. Keep new findings here; summarize only current state and constraints in the handoff. Intentional compatibility differences belong in the divergence ledger.

2026-08-14

• Confirmed that the codebase is feasible to migrate incrementally to Java.
• Confirmed that generalized Scala try/catch overhead is not present; only a small set of exception-based non-local returns is relevant.
• Identified closure/boxing/collection allocations as stronger performance candidates.
• Confirmed that the existing runtime compiler already has a Java trait path.
• Confirmed that public bytecode exposes Scala types and compiler artifacts, so bridges and Scala runtime removal must be separate decisions.
• Confirmed Hodgepodge's normal/early/late UniMixins plus GTNHMixins registration pattern as the reference for fixed mixins.
• Confirmed that UniMixins is not a drop-in replacement for ForgeMultipart's runtime composite-tile generator.
• Confirmed GTNHLib as a viable route to fastutil, subject to pack-aligned versioning and runtime-resolution verification.
• Adopted characterization tests against the existing Scala implementation as a prerequisite for each converted area, backed by golden ABI/data fixtures and real Forge integration scenarios where plain JVM tests are insufficient.
• Bootstrapped JUnit Jupiter and passed an eight-case IDWriter characterization pilot against the untouched Scala implementation, covering byte/short/int thresholds and exact encoded bytes.
• The pilot found that negative IDWriter.setMax values select the byte carrier because Scala 2.11 treats 0xffffffff as signed -1; current registry callers supply non-negative collection sizes, so this is recorded as a dormant edge case and possible deliberate divergence rather than changed during characterization.
• Added a dedicated functionalTest source set and runFunctionalTestServer task. The task starts a real Java 8 Forge dedicated server, loads a test-only FML mod, runs JUnit after FMLServerStartedEvent, writes legacy JUnit XML, and shuts the server down.
• Passed the first two Forge integration checks against the untouched Scala implementation: complete server lifecycle/world startup with all three ForgeMultipart mod IDs loaded, and generation plus constructor-class caching of a TSlottedTile composite with its 27-slot map.
• Hardened the Gradle wrapper to delete stale reports and fail when no fresh report is produced, no tests run, or any failure/error is reported. This is necessary because Forge 1.7.10 can terminate after a test-mod exception with process exit code 0.
• Confirmed the Java 8 server lane on Azul OpenJDK 8u492. The current deobfuscated modern-server tasks are not usable as release evidence: Java 21 needs the legacy Security Manager switch and then Lwjgl3ifyRelauncherTweaker rejects the server launch; Java 25 rejects System.setSecurityManager before Forge loads. Modern-Java validation therefore remains a packaged-server gate rather than a custom test-runner workaround.
• Added eight plain-JVM characterization cases for NormalOcclusionTest and NormallyOccludedPart: empty sets, separation on every axis, face contact, tolerance-sized overlap, real overlap, containment, identical boxes, multiple-box all-pairs behavior, normal-box delegation, partial-box delegation, and parts without occlusion interfaces.
• Confirmed that normal occlusion returns true when parts may coexist, despite the source comment saying “true if the test fails.” Face contact and overlaps no larger than CodeChickenLib's 1e-5 intersection tolerance are accepted; larger overlaps reject placement. Preserve the behavior and correct the misleading documentation separately when this area is ported.
• Added nine plain-JVM characterization cases for PartialOcclusionTest: its fixed 8³ grid and x-major indexing, part-ID encoding, half-voxel coordinate rounding, required visibility, complete-occlusion exemption, cross-part overlap, same-part box overlap, unfilled entries, and the public JPartialOcclusion overload.
• Confirmed that every non-exempt part needs at least one exclusively owned voxel. Any second write to an occupied voxel permanently changes it to -1, including overlap between two boxes supplied by the same part; this can make that part fail the test. Preserve this exact dynamic-tile behavior during translation unless it is changed later as an explicitly documented bug fix.
• Completed the first behavior-preserving production conversion by replacing IDWriter.scala with IDWriter.java. All eight existing encoding cases, all 25 plain-JVM tests, the clean build, and both Java 8 Forge server checks pass unchanged.
• Preserved the four legacy Scala function accessor descriptors as deprecated binary bridges and added direct Java write(MCDataOutput, int) and read(MCDataInput) methods. Recompiled Scala registry callers use the new primitive methods because Scala property auto-application does not apply to accessors declared in Java.
• Removed the six IDWriter$$anonfun$setMax$* compiler artifacts from the packaged jar. Their disappearance and replacement with Java anonymous helper classes is recorded in JAVA_MIGRATION_DIVERGENCES.md; the supported IDWriter descriptors remain link-compatible.
• Added a frozen Scala 2.11.5 consumer compiled against the reference dev jar. Its constructor and inherited default method call JPartialOcclusion$class directly, so it detects the linkage failure that freshly recompiled tests would miss.
• Replaced TPartialOcclusion.scala with Java implementations of PartialOcclusionTest and JPartialOcclusion. The interface keeps its name and method descriptors, while allowCompleteOcclusion() is now a Java default method and the deprecated $class helper remains for old Scala binaries.
• Passed all ten partial-occlusion behavior/API cases, the frozen Scala binary consumer, all 27 plain-JVM tests, a clean build, and both Java 8 Forge server checks. The existing marker-interface registration remains unchanged and continues to drive runtime tile generation.
• Completed the downstream ABI inventory by constant-pool scan of 240 mod jars in GTNH daily 2026-08-14+678, recorded in JAVA_MIGRATION_ABI_INVENTORY.md with the scanner in tools/AbiScan.java and the frozen baseline in src/test/fixtures/abi/. GitHub code search was rejected as an oracle because it indexes default branches only and cannot see reflection strings or closed-source consumers.
• Found 27 consumer jars referencing 35 inherited types, 255 exact member descriptors, 76 other types, and 20 reflective string constants.
• Answered open decision 2: third-party Scala traits are registered externally. ProjRed passes its own LightMicroblock Scala trait to MicroblockGenerator.registerTrait, so registerScalaTrait and ScalaSignature decoding must survive Phase 7.
• Answered open decision 4: Scala runtime removal is not achievable for the first Java release. ProjRed, OpenComputers, ProjectBlue, and ForgeRelocationFMP link against 16 static methods on 8 trait $class helpers plus 17 companion MODULE$ singletons.
• Found only five referenced descriptors containing Scala types, and TileMultipart.jPartList() already outweighs partList() in downstream use. The Scala bridge surface is much smaller than the initial audit assumed.
• Found zero downstream references to IDWriter, so its four retained Scala function accessors are not load-bearing and can be dropped.
• Removed both speculative bridges the inventory proved dead: the four IDWriter Scala function accessors and the whole JPartialOcclusion$class helper, along with the ReferenceScalaPartialOcclusion fixture that only existed to verify the helper. JPartialOcclusion itself and both of its method descriptors are unchanged.
• IDWriter now selects a carrier width instead of storing Scala closures, removing the per-call Integer boxing and Function1/Function2 allocation that the first port had preserved. The nine encoding cases still pass unchanged.
• Established the working rule for the remaining phases: check JAVA_MIGRATION_ABI_INVENTORY.md before writing a bridge, rather than writing one reflexively for every converted file.
• Ported TCuboidPart, JCuboidPart and TCuboidPart$class to Java, the first conversion of a trait whose $class helper is genuinely load-bearing. All reference descriptors are preserved, verified by diffing javap -s against the reference dev jar, and a frozen Scala 2.11.5 consumer whose forwarders call all four statics loads and runs against the port.
• Found the first structural limit of the migration: Scala trait linearization cannot be reproduced by a Java interface, because a superclass method always beats an interface default on the JVM. Recompiled Scala consumers that mix TCuboidPart into a TMultiPart subclass now silently get TMultiPart's empty implementations. Binary compatibility is unaffected, and CuboidPartCharacterizationTest carries the regression guard, but this applies to every remaining trait that overrides TMultiPart members and should be assumed for TFacePart, TNormalOcclusion, TIconHitEffects and TItemMultiPart as well.
• Recorded the consequence for consumers: Scala code that recompiles must extend JCuboidPart or declare the overrides itself. This belongs in the release notes for the first Java release, not only in the divergence log.
• Found a build-order constraint: compileJava runs before compileScala, so ported Java that still references Scala types must live under src/main/scala for joint compilation, as minecraft/McBlockPart.java already does. Files can move to src/main/java once their Scala dependencies are ported.
• Established the fixture recipe for the remaining load-bearing bridges: build a reference dev jar at the pre-port commit, compile the consumer with Scala 2.11.5 under Java 8 with -target:jvm-1.8 against that jar plus the project compile classpath, then store the class base64-encoded under src/test/resources/compat/.
• Ported the whole TNormalOcclusion.scala unit: NormalOcclusionTest, NormalOcclusionTest$, JNormalOcclusion, TNormalOcclusion, TNormalOcclusion$class and NormallyOccludedPart. The singleton and both trait interfaces are descriptor-identical to the reference; the other three add only private members.
• Found that Scala emits trait super accessors as ACC_SYNTHETIC, which javac hides completely. An abstract synthetic method cannot be implemented by any Java class or by Scala recompiled against a Java interface, so codechicken$multipart$TNormalOcclusion$$super$occlusionTest is emitted as a non-synthetic default returning true. Method resolution ignores the flag, so existing call sites are unaffected. Expect the same treatment wherever a remaining trait calls super.
• Found the dangerous shape of the linearization problem. HollowMicroblock simply lacked an override, which is easy to spot. PostMicroblock already had one ending in super.occlusionTest(npart), which used to route through the trait and now reaches Microblock directly, silently dropping the box test while still compiling. Existing super call sites must be audited on every remaining trait conversion, not just missing overrides.
• Recorded a second source-only divergence: NormalOcclusionTest was a Scala object, so NormalOcclusionTest(a, b) apply sugar no longer compiles and recompiled Scala callers must write NormalOcclusionTest.apply(a, b). Both static forwarders and the MODULE$ singleton keep their descriptors, so binaries are unaffected.
• Kept scala.collection.Traversable in two descriptors, as the ABI inventory predicted. They are drained with JavaConversions.asJavaIterator(boxes.toIterator()), which is the one interop route callable from Java.
• Removed two more closure artifacts, NormalOcclusionTest$$anonfun$apply$1 and its nested $$anonfun$apply$2, and corrected the scaladoc that claimed the test "returns true if the test fails".
• Ported TFacePart, the first trait where Java default methods are actually safe. TMultiPart declares neither solid nor redstoneConductionMap, so there is no superclass method for a default to lose to. The interface is descriptor-identical to the reference and no in-repo Scala needed changing.
• Adopted the resulting rule for the remaining traits: emit default methods only when no class in an implementor's superclass chain declares the same member, otherwise leave the member abstract and add explicit forwarders as TCuboidPart and TNormalOcclusion required.
• Made TFacePart inheritable from Java as a side effect. Both members were abstract on the reference interface, so minecraft/McSidedMetaPart had to declare them even to accept the defaults. That class stays descriptor-identical, so the change is purely additive.
• Ported the whole TIconHitEffects.scala unit: IconHitEffects, JIconHitEffects, JIconHitEffects$class, TIconHitEffects and TIconHitEffects$class. Both interfaces are descriptor-identical to the reference and the other three add only a private constructor.
• Confirmed the default-versus-abstract rule discriminates correctly within a single file. JIconHitEffects.getBreakingIcon became a default because TMultiPart does not declare it, while TIconHitEffects.addHitEffects and addDestroyEffects stayed abstract because it does. MicroblockClient needed explicit forwarders only for the latter pair.
• Removed IconHitEffects$ and its MODULE$ field. No jar in the pack references it, in bytecode or by name, so it is dead under the inventory rule. This is the first public class the migration has dropped rather than a method, and it contrasts with NormalOcclusionTest$, which is referenced and was kept.
• Preserved evaluation order inside addDestroyEffects rather than hoisting the tile read, because the characterization pins which work happens before a null tile fails.
• Established that particle appearance cannot be asserted headless. Icon selection, side order and bounds scaling are covered by tests; the visual result stays on the manual checklist.
• Ported ItemMultiPart.scala into JItemMultiPart, TItemMultiPart and TItemMultiPart$class. The interface is descriptor-identical to the reference, JItemMultiPart gains only additive statics, and the bridge keeps all three public statics for ProjRed.
• Generalised the default-versus-abstract rule. TItemMultiPart extends Item rather than TMultiPart, and the same split applied: getHitDepth became a default because Item does not declare it, while onItemUse stayed abstract because Item does. What matters is the implementor's actual superclass, not TMultiPart specifically.
• Confirmed that placement logic is testable headless. onItemUse short-circuits as soon as newPart returns null, before any world, player or stack access, so the depth branch, the neighbour offset and the shared mutated BlockCoord can all be asserted with null arguments.
• Added the first functional coverage of runtime class generation interacting with a ported type. Microblock classes are built by ASM at run time, so a plain-JVM test cannot show that a generated class resolves a Java interface default; the Forge server suite now generates a FaceMicroblock and asserts it inherits redstoneConductionMap, and generates a HollowMicroblock and asserts its own 0x10 and false still win.

2026-08-15

• Ported the six marker interfaces: TSlottedPart, IRandomDisplayTick, INeighborTileChange, TRandomUpdateTick, ISidedHollowConnect and IMicroMaterialRender. All six are member- and descriptor-identical to the reference, and the seven implementors and mixin tiles were diffed as well and are unchanged member for member.
• Confirmed that five of the six were already pure abstract interfaces in bytecode with no $class helper, so their conversion had no bytecode consequence at all. Exactly one class left the jar: TRandomUpdateTick$class.
• Applied the default-versus-abstract rule to TRandomUpdateTick.onWorldJoin and got the failing answer: TMultiPart declares onWorldJoin, so a default would be shadowed by the superclass and the auto-registration would silently never run. It stays abstract, and implementors declare it and call TickScheduler.loadRandomTick themselves, which RedstoneTorchPart — the only implementor in this codebase — already did.
• Applied the bridge rule to TRandomUpdateTick$class and got a clean negative: no jar in the pack references TRandomUpdateTick in any form, and the frozen baseline contains exactly the eight $class helpers the inventory lists. No bridge was written, following the IDWriter precedent. The accepted cost is a recompiled-Scala-consumer break with no shipping consumer.
• Found that IMicroMaterialRender is implemented for every part solely by TMultiPart's Scala-style world/x/y/z/getRenderBounds accessors. Renaming any of them to a bean accessor would silently unimplement the interface, so the names are now pinned by a characterization test rather than left to reviewer attention.
• Established that for interfaces carrying no implementation, the characterization is the shape: every member abstract and public, no superinterface, and the exact member set. That is enough to catch the two realistic failure modes, a stray default and a renamed accessor.
• Noted that IRedstonePart.scala is misleadingly named and is not a marker-trait file. It carries six traits plus RedstoneInteractions, whose MODULE$ is load-bearing, and was moved out of the low-risk group.
• Historical documentation gap: the ports between TItemMultiPart and this entry — TEdgePart, Saw, both registries, TileMultipart, TMultiPart, TickScheduler and BlockMultipart — did not receive dated findings here. Use the handoff for their current status and git history for the original validation narrative; the divergence ledger now records only their effective compatibility differences.
• Ported MultipartHelper, MultipartHelper$ and MultipartHelper$IPartTileConverter to Java. All three are public-member- and descriptor-identical to the reference and the full emitted class list is unchanged, so this port neither added nor removed a class.
• Kept MultipartHelper$ on the strength of a reflective string constant alone. It is not among the 17 MODULE$ singletons read from bytecode and no jar links against it, but guidenh names it, and the inventory warns that removing a companion breaks such consumers invisibly. This is the opposite call to IconHitEffects$, which was dropped because nothing referenced it in bytecode or by name, and it establishes that the MODULE$ list alone is not sufficient grounds to delete a companion.
• Found a reusable characterization technique: a class that cannot class-initialize headless is a probe for control flow. MultipartSaveLoad reflects into TileEntity's static maps through ObfMapping and always throws under a plain JVM, so createTileFromNBT returning null rather than raising proves the id guard short-circuits before the loadingWorld assignment. Assert LinkageError rather than the exact type, because the first attempt raises ExceptionInInitializerError and later ones raise NoClassDefFoundError.
• Confirmed that erasure does not weaken IPartTileConverter.convert. The cast to T compiles away, but the ClassCastException a mismatched tile produces comes from the synthetic bridge on the subclass overriding convertMulti(T), which is the same mechanism Scala's asInstanceOf[T] relied on. It is now pinned by a test, because the code reads as though the check was lost.
• Added five Forge server tests, doubling that suite, because most of this class cannot run headless. They cover tile construction through the ASM generator, the NBT round trip through the save/load hooks, registerTileConverter appending to a Scala MutableList from Java, and sendDescPacket against a loaded chunk.
• Dropped the two commented-out blocks the reference carried, the PlayerInstance.playersInChunk reflection and the multi-tile sendDescPackets, rather than reproducing dead Scala as dead Java. The reason they existed, a missing forge access transformer, is now in the class javadoc.
• Read guidenh's actual source at 6137525 rather than inferring from its constant pool, and recorded the exact reflective member list in JAVA_MIGRATION_ABI_INVENTORY.md. The scan could see the 20 names; only the source shows which members are looked up on them, and none of it is visible to the ABI diff.
• Found that MultipartGenerator$.MODULE$ is load-bearing through reflection. generateCompositeTile is private[multipart], so no static forwarder exists and guidenh's static attempt always misses, leaving the companion as the only route. Phase 6/7 must keep it.
• Found that MicroblockGenerator$.create is matched by exact parameter types, with MicroblockClass's fully qualified name string-compared. Widening a parameter or renaming the class breaks the lookup while every call site still links.
• Verified against the already-ported TileMultipart that partList_$eq(scala.collection.Seq), loadParts, notifyTileChange and markRender all survived. partList_$eq is a Scala var setter with no Java-facing equivalent and is reflectively load-bearing, so dropping it for a list mutator would have broken guidenh invisibly. It was kept.
• Confirmed the MultipartHelper port satisfies guidenh directly: it resolves createTileFromNBT as a static on the plain class and only falls back to MultipartHelper$.MODULE$ if that misses, so the retained companion is belt-and-braces rather than the primary path.
• Ported TileCache to Java, the first conversion free to change shape rather than preserve it. It has zero downstream references in bytecode and does not appear in guidenh's reflective names, so map() became a java.util.Map, add/remove became void, and apply returns a nullable FlaggedTile instead of a scala.Option. No internal caller used any of the discarded return values.
• Dropped TileCache$, TileCache$FlaggedTile$ and the whole case-class machinery on FlaggedTile. It is only ever a map value, never compared, hashed, printed or destructured. This is the IconHitEffects$ case rather than the MultipartHelper$ one: nothing names it in bytecode or by string.
• Pinned an unreachable branch before removing it. The reference's findTile ends in case _ => null, but Some(FlaggedTile(t, rem)) matches whatever the flag holds, so a tile flagged removed is returned like any other and only the warning is suppressed. The functional test asserts that before the port so the Java version cannot quietly start returning null.
• Confirmed the adapter approach works for ports that change collection types. The characterization test named scala.Option in exactly one helper, so the port's test diff was two lines and every behavioral assertion carried over untouched.
• Ported PacketScheduler, IScheduledPacketPart and TScheduledPacketPart. IScheduledPacketPart is descriptor-identical, schedulePacket is unchanged, and TScheduledPacketPart.read stays abstract because TMultiPart declares it.
• Found the case the default-versus-abstract rule splits within a single interface. read cannot be a default because TMultiPart declares it, but writeScheduled and readScheduled can, because TMultiPart declares neither. Making the latter two defaults restores what a Scala implementor already got from the trait for free; only Java implementors ever had to write them out.
• Added TScheduledPacketPart.readMask as a Java 8 interface static, carrying the dispatch TScheduledPacketPart$class.read used to hold. Where a trait's central member cannot become a default, an interface static plus a documented one-line forwarder is the replacement, and it is the pattern to reuse.
• Widened sendScheduled from private[multipart] to public. Its only caller is in codechicken.multipart.handler, and Java has no scope spanning a package and its siblings, so package-private would not compile. Expect this wherever private[multipart] crosses into the handler package.
• Recorded that the whole subsystem has no implementors at all, in this codebase or in the pack. It is a third-party extension point, which is why every behavioral test had to construct its own part.
• Confirmed the Forge server suite can drive the packet path without players connected. MultipartSPH.getTileStream only needs a non-remote world and a position, so a part bound to a tile with setWorldObj is enough to exercise getWriteStream.
• Ported ControlKeyModifer and ControlKeyHandler. isControlDown(EntityPlayer) and isClientPressing() keep their descriptors; map() became a java.util.Map, and the implicit-conversion pair playerControlValue/ControlKeyValue was dropped because it only ever existed to give Scala player.isControlDown sugar and the reference already shipped the explicit static "for Java users".
• Kept the misspelling in ControlKeyModifer. It is the published type name; only the file name, which said ControlKeyModifier.scala, was corrected. Renaming the type is an API change with no forcing reason and should be a deliberate decision rather than a side effect of a port.
• Converted the first Scala object that extends a class rather than being a plain singleton. ControlKeyHandler is now an ordinary KeyBinding subclass with an INSTANCE constant, which drops the twelve static forwarders Scala generated for inherited KeyBinding members along with the companion. The registration sites pass ControlKeyHandler.INSTANCE.
• Found that a Forge FakePlayer makes the server half of player-dependent code testable. FakePlayerFactory.getMinecraft(worldServer) yields a player whose world is not remote, which is exactly the branch the server takes, and it needs no connection.
• Recorded that the client half remains untestable in both harnesses. isClientPressing is only ever set from a client tick, so the key binding, the press/release packet and the client branch of isControlDown are all manual checks.
• Removed both package objects rather than porting them. A Scala package object compiles to a class named package, which is a Java keyword, so no Java source can declare or even name it; the characterization had to reach both through Class.forName. Each held one member, a logger alias for its proxy, so the indirection was inlined at its eight call sites instead of being given an invented Java home.
• Proved the substitution was an identity before making it. The functional test asserted that each alias returned the very instance its proxy holds, so replacing logger with MultipartProxy.logger / MicroblockProxy.logger cannot change behavior. ConfigContent and MultipartGenerator are descriptor-identical afterwards.
• Noted the first case where the migration's answer is deletion. Zero downstream references plus an impossible target name means there is nothing to preserve, and inventing a MultipartLogger type to hold a one-line forwarder would add API rather than remove it.
• Emptied the low-risk queue. Everything remaining is the medium group or later, so the next piece of work should be chosen deliberately rather than taken off the top of a list.
• Ported MultipartRenderer in the TickScheduler$ shape, with the companion holding the implementation and the plain class holding static forwarders. Forge registers the singleton itself and guidenh resolves the static first, so both halves are load-bearing for different reasons and the emitted class list is unchanged.
• Applied the reflective-name rule for the second time, and this is the case it was written for: MultipartRenderer has no bytecode consumer at all, only guidenh string constants, and both the class and its companion had to survive.
• Found a Scala-to-Java trap that is not silent but will recur: uniform access makes renderer.hasOverrideBlockTexture read the same whether it is a field or a no-arg method. It is a method, and the port did not compile until it grew parentheses. Every remaining renderer conversion will meet this.
• Dropped the three static forwarders Scala generated for inherited TileEntitySpecialRenderer members, the same category as the twelve KeyBinding forwarders dropped from ControlKeyHandler.
• Dropped an unused ThreadSafeISBRH import. It annotated nothing and appears nowhere else; if the intent was to mark this ISBRH thread-safe for Angelica then the annotation was never applied in the reference either, which is worth checking independently of the migration.
• Recorded that this port adds nothing to the automated suites and everything to the manual checklist. Static and dynamic rendering, the breaking overlay and the render id all need a client.

2026-08-27

• Reproduced Schematica 1.12.6's exact ReflectionHelper lookup of the private MultiPartRegistry$.codechicken$multipart$MultiPartRegistry$$typeMap field. The test failed against the existing Java port with UnableToFindFieldException, matching Schematica's silent integration-disable path.
• Restored the exact private field name and scala.collection.mutable.Map descriptor as Scala's live wrapper over the canonical Java registry map. The wrapper adds no copied state or synchronization path.
• Proved through the reflected Scala view that Schematica can resolve a factory and that the Java registry immediately sees the same entry. The focused registry suite and all 126 plain-JVM tests pass.
• Added four source-consumer structural guards without adding downstream mods as test dependencies. They pin GuideNH's two BlockMicroMaterial mixin targets, Et Futurum's mutable static button-orientation arrays, and Iguana's reflected ItemSaw.harvestLevel field.
• Reproduced Galacticraft's name-only method scan and froze its dangerous assumption: exactly one public MicroMaterialRegistry.registerMaterial method may exist, it must accept (IMicroMaterial, String), and BlockMicroMaterial(Block, int) must remain reflectively constructible. All 130 plain-JVM tests pass.
• Accepted the dedicated-server EULA locally in ignored run/server/eula.txt, enabling the Forge characterization suite without adding a distributable acceptance file to the repository.
• Froze tile NBT order with two different built-in parts: the outer tile id, ordered parts entries and per-part id/payload values survive reconstruction, and jPartList plus partMap reproduce the same order and slots.
• Froze add/remove callback order, list publication, slot binding and detachment in a live Forge world. The plain-JVM replacement test also proves that a successful canReplacePart query does not mutate order or bindings.
• Reproduced MatterManipulator's live-tile relocation shape. Removing the tile first calls onWorldSeparate for each part in list order; after reinsertion, onMoved calls each part's onMoved and default onWorldJoin, again in list order. The original generated tile, part instances, order, slot map and tile references survive.
• Froze the complete logical chunk-description payload around the same torch/button pair: packet type, chunk coordinates, tile count, nibble-relative X/Z, full Y, part count, sorted runtime part IDs, part order and both meta bytes. CodeChickenLib's deferred Deflater transport step is deliberately outside this FMP fixture.
• Froze representative generated-trait behavior. The existing TSlottedTile fixture pins built-in Scala trait class caching and field initialization; a ProjectRed-shaped external Scala microblock trait pins registration by name, trait initialization and method dispatch; and TPartialOcclusionTile pins Java-trait rewriting and override dispatch through the generated tile.
• Froze a server-only pass-through interface with primitive/reference overloads. The generated tile forwards to one implementing part, rejects a second implementor, preserves and rebinds its delegate through copyFrom, and clears the generated implementation field on removal.
• Added an opt-in Forge/JFR workload and captured the first focused CPU/allocation baseline. With eight parts, updateEntity and operate allocate 184.0 and 183.9 bytes per call; generated redstone's three-query iteration allocates 80.5 bytes. CPU and allocation sites point to TileMultipart.parts() collection copies and Scala redstone IntRef/closure traversal. Full methodology and rerun commands are in JAVA_MIGRATION_PROFILE.md.
• The expanded baseline is 130 plain-JVM tests and 28 Forge server tests, all passing.

2026-08-28

• Ported all six interfaces and RedstoneInteractions from IRedstonePart.scala as one unit. The emitted class list is unchanged, every public descriptor is unchanged, and RedstoneInteractions$.MODULE$ remains the implementation singleton behind the static façade.
• Added six plain-JVM tests for interface shape, façade/companion members, maps, part-mask precedence, connector routing, and neighbor coordinate transforms, plus three Forge tests for initialized vanilla blocks, world power routing, the redstone-wire metadata fallback, and generated IRedstoneTile selection.
• Re-profiled immediately before and after the port. Allocation stayed at roughly 4.02 GB / 80.5 B per generated three-query iteration, and JFR retained the same TRedstoneTile Scala closure/iterator sites. That cost belongs to the Phase 5 generated-trait conversion, not this helper unit.
• Chose MicroRecipe.scala as the next independent Phase 4 unit because its nested collection scans compile early exits into NonLocalReturnControl; characterize all five recipe paths and precedence before porting it.
• Characterized MicroRecipe's complete 17-method façade/companion ABI, Scala splitMap, all five recipe forms, class-specific gluing rules, saw ordering, exact material/tag lookup, and hollow-over-gluing precedence against the original Scala implementation.
• Ported the recipe singleton to Java with ordinary loops. The published MicroRecipe static façade, MicroRecipe$.MODULE$, scala.Tuple3 return and immutable Scala map descriptors remain; the 12 private Scala closure classes and their NonLocalReturnControl exits are gone.
• The recipe port passes all 141 plain-JVM and 37 Forge tests.
• Characterized TPartialOcclusionTile against the untouched Scala implementation with four focused tests covering its exact direct class shape, partial/normal precedence, complete-occlusion behavior, and both short-circuit paths.
• Ported TPartialOcclusionTile to direct Java source without changing the generator. Its compiled input still has one no-arg constructor, no fields, and the same two public descriptors; the Forge rewrite still exposes exactly the two behavior methods plus its super accessor, caches the generated class, and passes all 37 server tests.
• The pilot raises the plain-JVM baseline to 145 tests. It deliberately proves no field or lifecycle behavior, so the next checkpoint is TSlottedTile, not a bulk conversion of the remaining traits.
• Characterized TSlottedTile against untouched Scala with six focused Forge cases plus the existing live-world lifecycle fixture. The gate freezes its exact 13-method runtime interface, 27-slot per-instance initialization, getter/setter rebinding, copy identity, clear/remove/bind behavior, occupied-slot rejection, Scala value equality, generated field, super accessors, and class cache.
• Ported TSlottedTile to a concrete Java mixin input with one public array field and ordinary loops. The runtime rewrite remains interface- and behavior-identical, while the four Scala range closures, $class artifact in the raw jar, and NonLocalReturnControl slot rejection disappear. All 145 plain-JVM and 43 Forge tests pass.
• Found a Phase 5 source-build constraint: shipping binaries still see the same runtime interface, but a consumer recompiled directly against the untransformed dev jar sees the Java mixin input as a class. Consumers that name a generated trait therefore need a transformed compile stub or must avoid direct trait invocations; record this before claiming source-compatible downstream rebuilds.
• Characterized TRedstoneTile against untouched Scala with three Forge cases covering its exact eight-method runtime interface, class caching, face/edge conduction, strong and weak maxima, mask filtering, arbitrary Seq input, neighbor masks, and vanilla-side translation. This directly covers ProjectRed's openConnections and Extra Utilities' one-argument weakPowerLevel calls.
• Ported TRedstoneTile to Java with allocation-free immutable-list traversal and an iterator fallback for other published Seq values. A package-private shim isolates inherited TileMultipart methods and Minecraft coordinate fields from known Java-trait transformer limitations; no public redstone or generated-interface member changed.
• The paired 50,000,000-iteration run fell from 4,023,855,000 bytes / 80.5 B per three-query iteration to zero measured allocation, while throughput rose 20.3% from 6,636,424 to 7,986,213 iterations/s. The checksum remained 3315999992, and all 145 plain-JVM plus 46 Forge tests pass.
• Characterized mutable-Seq read behavior, direct ordered indexing, and BlockMultipart.getTile filtering, then extended the focused workload with getLightValue and getTile phases before changing production code.
• Removed the Java-port-only ArrayList snapshots from all read paths and Java wrappers from internal block, renderer, and scheduler paths. The public jPartList() bridge is unchanged; add/remove retain intentional mutable snapshots before publishing a replacement immutable Seq.
• In the paired run, getLightValue fell from 183.9 B to 0.0 B per call with 11.42x throughput, and getTile fell from 24.0 B to 0.0 B per call with 2.89x throughput. All 147 plain-JVM and 46 Forge tests pass.

2026-08-30

• Characterized TileMultipartClient and TRandomDisplayTickTile together against untouched Scala. Six behavior cases freeze render-cache partitioning and bounds, lazy initialization, dynamic short-circuiting, base no-op display ticks, and ordered IRandomDisplayTick dispatch; a Forge smoke case freezes both exact runtime interfaces, inheritance, generated fields, and generated-class caching.
• Ported both traits to Java with package-private access shims. registerJavaTrait now linearizes an already registered Java parent trait, recognizes explicit field accessors, and skips transient runtime caches when auto-generating copyFrom. Trait registration now precedes BlockMultipart construction so Forge defines the runtime interfaces before ordinary Java bytecode can preload the mixin inputs.
• Added three no-op client dispatch hooks to TileMultipart, allowing in-repo Java callers to invoke generated overrides through the stable superclass rather than emit class opcodes against types Forge rewrites to interfaces. The runtime trait surfaces remain exact; the raw dev-jar source-build limitation remains documented.
• All 153 plain-JVM tests and all 77 Java 8 Forge dedicated-server tests pass. Actual static/dynamic rendering and particle appearance remain client-only manual checks.
• Characterized MultipartCompatiblity and MCPCCompatModule against untouched Scala. Three plain-JVM cases freeze both static facades, both MODULE$ companions, the private Scala Function4 field, default allow behavior and callback identity; two Forge cases freeze non-MCPC loading and the logged missing-hook fallback.
• Ported both singletons to four Java types with unchanged public names and descriptors. The callback still propagates reflection and cast failures unchanged, while the two Scala anonymous-function artifacts become private named Java callback classes. No frozen binary or audited source consumer names those implementation classes.
• All 156 plain-JVM tests and all 79 Java 8 Forge dedicated-server tests pass. This initialization-only hook is not a meaningful target for the focused allocation benchmark; successful MCPC integration remains environment-dependent.
• Characterized MultipartMod against untouched Scala. Two plain-JVM cases freeze both annotated singleton types, all ten lifecycle methods and annotations, plus the MultipartPH.channel companion descriptor and identity; two Forge cases freeze FML's companion mod instance, completed initialization and server-stop cleanup.
• Ported the singleton to an annotated Java facade/companion pair while retaining modLanguage = "scala". The one source use of the object as a value now names MultipartMod$.MODULE$ explicitly, leaving the compiled packet-handler field and accessor unchanged.
• Found that the inherited MultipartProxy.postInit static forwarder carries @SideOnly(CLIENT) and is stripped on a dedicated server. The Java companion therefore invokes MultipartProxy$.MODULE$ directly, matching the reference Scala bytecode and allowing virtual resolution to reach the server implementation.
• All 158 plain-JVM tests and all 81 Java 8 Forge dedicated-server tests pass. Mod lifecycle dispatch is startup-only, so it is not a meaningful focused throughput or allocation target.
• Characterized MultipartEventHandler against untouched Scala. Two plain-JVM cases freeze both singleton types, all twelve public event methods, priorities and the client-only highlight boundary; three Forge cases freeze companion registration on both buses, chunk load/unload cleanup, queued watches and END-phase tick dispatch.
• Ported the singleton to a Java facade/companion pair with unchanged public names, descriptors and annotations. The proxy now names MultipartEventHandler$.MODULE$ explicitly, preserving the exact object registered on both buses.
• Server ticking still passes the configuration manager's live player list through Scala's Java-list buffer adapter; no copy or new traversal was introduced. All 160 plain-JVM and all 84 Java 8 Forge dedicated-server tests pass.
• Characterized MicroblockMod against untouched Scala. Two plain-JVM cases freeze both annotated singleton types, all ten lifecycle/IMC methods, the mutable angelicaCompat accessors and shared identity; one Forge case freezes FML's companion mod instance and the completed microblock lifecycle.
• Ported the singleton to an annotated Java facade/companion pair while retaining modLanguage = "scala". Lifecycle dispatch calls MicroblockProxy$.MODULE$ directly, matching the reference bytecode and avoiding side-only static forwarders that Forge strips on a dedicated server.
• The internal client assignment now calls the preserved angelicaCompat_$eq method explicitly because recompiled Scala cannot apply property-assignment syntax to a Java-authored setter. The compiled accessor ABI is unchanged.
• All 162 plain-JVM and all 85 Java 8 Forge dedicated-server tests pass. Startup and lifecycle dispatch are not a meaningful focused throughput or allocation target; MicroblockEventHandler.scala is the next target.
• Reproduced the reported stale incremental @Mod(version) failure immediately after a commit. Gradle reran compileScala, but Zinc retained the joint-compiled Java classes that had inlined the previous Tags.VERSION.
• Configured compileScala to force Zinc recompilation whenever Gradle schedules the task. The focused version test passes without cleaning both before and after a commit changes the generated version, so the assertion remains.
• Characterized MicroblockEventHandler against untouched Scala. Two plain-JVM cases freeze both singleton types, all four public event methods, normal event metadata and both client-only boundaries. One Forge case freezes companion registration and complete method stripping on a dedicated server.
• Ported the handler to a Java facade/companion pair and changed the one Scala registration to name MODULE$ explicitly. Texture-atlas filtering, highlight guards, matrix/render sequence and cancellation behavior are unchanged; their actual rendering remains on the client manual checklist.
• All 164 plain-JVM and all 86 Java 8 Forge dedicated-server tests pass. This event-only adapter is not a meaningful focused performance target; microblock/handler/packethandlers.scala is next.
• Characterized the ForgeMicroblock packet-handler unit against untouched Scala. Seven plain-JVM cases freeze the shared channel base, both facade/companion surfaces and exact packet interfaces, the integrated-server registry skip, ordered missing-material disconnect, unknown-type MatchError and no-op server callback. One Forge case freezes the handshake channel, type and complete material-ID payload.
• Ported all five emitted packet-handler classes to Java and changed the two Scala proxy registrations to pass the companion singletons explicitly. Every callable public member and the emitted class list match the reference; the registry channel and wire format are unchanged.
• All 171 plain-JVM tests pass. After the local EULA was accepted, all 87 Java 8 Forge dedicated-server tests pass, including the new registry handshake.
• Characterized MultipartSaveLoad against untouched Scala. Three plain-JVM cases freeze the static facade, load-bearing companion, private fields and exact dummy class shape. Four Forge cases freeze ProjectRed-style binary linkage, both reflected vanilla maps, converter precedence/deletion and saved multipart reconstruction.
• Ported the singleton to a Java facade/companion pair and kept the dummy as the static facade member MultipartSaveLoad.TileNBTContainer, which emits the literal MultipartSaveLoad$TileNBTContainer binary name. Nesting it under the companion would emit the wrong double dollar. Every callable public member matches the reference. Only the unreferenced compiler-generated $$anonfun$1 closure disappeared.
• All 174 plain-JVM tests and all 91 Java 8 Forge dedicated-server tests pass. The next medium-risk target is MissingMicroMaterial.scala; its real icon/render paths remain client-manual work.
• Characterized MissingMicroMaterial against untouched Scala. Three plain-JVM cases freeze the exact facade and companion surfaces, MODULE$, inert material values, interface defaults and all client-only boundaries. One Forge case freezes side stripping and the exact singleton registered under the missing-material name and ID.
• Ported the singleton to a Java facade/companion pair and changed both Scala object-value uses to name MODULE$ explicitly. The placeholder key, stone item, sound, strength, resistance and missing-texture render pipeline are unchanged; only the actual client rendering remains manual.
• All 177 plain-JVM and all 92 Java 8 Forge dedicated-server tests pass. This inert singleton is not a meaningful focused performance target; DefaultContent.scala is the next medium-risk target.
• Characterized DefaultContent against untouched Scala. One plain-JVM case freezes its one-method static and companion surfaces. Two Forge cases freeze the five microblock factories and IDs, all 103 sorted built-in materials, their exact implementation types and the complete legacy-name remap table.
• Ported the singleton to a Java facade/companion pair while continuing to use the existing BlockMicroMaterial$ overloads and Scala ranges. Registration contents, ordering and the historical meta-0-only log2/leaves2 overload behavior are unchanged.
• All 178 plain-JVM and all 94 Java 8 Forge dedicated-server tests pass. Pre-init-only registration is not a meaningful focused performance target; GrassMicroMaterial.scala is the next material unit.
• Characterized GrassMicroMaterial and TopMicroMaterial against untouched Scala. Five plain-JVM cases freeze both constructors, the grass overlay accessor used by UtilitiesInExcess, the top default-argument facade/companion, common-side boundaries and horizontal/side UV plus colour-pipeline routing. One Forge case freezes their registered blocks/meta and the exact surface left on a dedicated server.
• Ported both classes and the default-argument companion directly to Java. Grass keeps its uncoloured base side pass, coloured top and height-adjusted side overlay; TopMicroMaterial keeps coloured horizontal faces and translated side UVs. All three emitted binary names and every callable public descriptor match the Scala reference.
• A clean compile was required to evict the deleted Scala classes before the unchanged characterization could test the Java implementation. All 183 plain-JVM and all 95 Java 8 Forge dedicated-server tests pass. The render path retains the same per-side transformation work, so no separate performance claim is made; multipart/handler/proxies.scala is the next medium-risk target.

2026-08-31

• Audited the published API surface against all 28 consumer checkouts to decide whether a cleaner API is warranted. It largely already is one: TMultiPart is an ordinary abstract Java class, and the factory, converter, material, PartMap, redstone and occlusion interfaces need no replacement. Added Phase 9 for the parts that are not.
• Found nine remaining public entries carrying Scala types. Two already have a Java sibling (jPartList, the String... registerParts overload), so their deprecation is free. getIdMap() needs no pair or map replacement because the array index is the material ID; materialCount() plus the existing materialName(int) and getMaterial(int) covers every audited use.
• Found a second and larger cleanliness problem: Scala's private[multipart] compiles to public, so seventeen implementation hooks are advertised as API. Verified all seventeen have zero external callers, and that the two similar-looking members that are load-bearing are bindPart (OpenComputers) and internalPartChange (ProjectRed). Fix is javadoc only, no descriptor change.
• Confirmed that removing Scala from FMP has no pack-level dependency payoff: OpenComputers (843 Scala files) and ProjectRed (171) keep scala-library in the pack regardless. Recorded this under Phase 8 so the motivation is not restated later as a dependency argument.
• Traced ScalaSignature.scala and ByteCodecs.scala to a single external caller, ProjectRed's ~60-line LightMicroblock trait. Rewriting it in Java deletes roughly 580 lines from FMP plus the Scala branch of ASMMixinCompiler, but it is not currently possible: registerJavaTrait rejects abstract classes while Microblock is abstract, and @SideOnly stripping exists only on the Scala signature path while LightMicroblock.renderDynamic is client-only and applied on both sides. Both gaps are recorded as Phase 7 prerequisites.
• Added Phase 10 for upstream consumer cleanup. All 27 consumers are GTNewHorizons forks and therefore patchable; Extra Utilities is the sole exception and is constrained rather than fixed. The pattern is a three-step ratchet: FMP adds a supported equivalent (additive, safe now), the consumer is patched and released, then FMP drops the private shape in a release allowed to break that ABI.

2026-09-01

• Characterized MultipartProxy against untouched Scala. Four plain-JVM cases freeze the four-type hierarchy, exact facade/companion surfaces, mutable singleton accessors, client-only boundaries and both chunk-index conversions. One Forge case freezes dedicated-server stripping, virtual fallback to the server implementation and initialized proxy state.
• Ported the hierarchy and facade to four Java types without changing their emitted names or callable public descriptors. Common generated-tile registration now names MultipartProxy$.MODULE$ explicitly so it still reaches the inherited server method after Forge strips the client override and its static forwarder.
• All 187 plain-JVM and all 96 Java 8 Forge dedicated-server tests pass. Startup registration and two bit-packing helpers are not a meaningful focused performance target; microblock/handler/proxies.scala is next.
• Characterized MicroblockProxy against untouched Scala. Four plain-JVM cases freeze its four-type hierarchy, complete facade/companion ABI, eight mutable server fields, protected Scala saw list and exact lazy-renderer shape. Two Forge cases freeze side stripping, inherited server lifecycle resolution, item/ore/recipe registration and saw order.
• Ported the hierarchy and facade to four Java types. The Scala MutableList remains for binary compatibility, the client renderer retains its field-only side annotation and lazy bitmap, and the saw-renderer closure becomes a direct iterator loop.
• All 191 plain-JVM and all 98 Java 8 Forge dedicated-server tests pass. This startup-only proxy is not a meaningful focused performance target; multipart/handler/packethandlers.scala is the last Scala handler unit and is next.
• Characterized the ForgeMultipart packet-handler unit against untouched Scala. Eleven plain-JVM cases freeze all six emitted retained types, exact facade/companion interfaces, channel identity, private prefixed state accessors, ordered registry and desync disconnects, control-key packets, coordinate streams and both update terminators.
• Ported the five top-level types and nested byte stream directly to Java. The three Scala mutable collection descriptors remain where reflection already observes them, while direct loops replace the anonymous MultiMap and thirteen closure classes without changing watcher, batching, framing or cleanup behavior.
• A clean build passes all 202 plain-JVM tests and the Java 8 Forge server passes all 98 tests. All six retained public surfaces match the reference by name and descriptor; only fourteen unreferenced compiler artifacts disappear. microblock/ItemMicroPart.scala is next.
• Characterized ItemMicroPart against untouched Scala. Six plain-JVM cases freeze its item, static facade and both companion surfaces, NBT/material semantics, creation overloads, invalid-class short circuits and a Scala 2.11.5 binary consumer that calls all four ItemMicroPart$.MODULE$ methods used by ProjectRed.
• Ported the item and renderer to four Java types with every callable public name and descriptor retained. Creative enumeration is a direct loop, and the renderer crosses the transformed MicroblockClient boundary through one narrow Scala helper rather than emitting an invalid class-method call from Java.
• A clean build passes all 208 plain-JVM tests and the Java 8 Forge server passes all 98 tests. The jar retains exactly the four public ItemMicroPart types; three unreferenced Scala iteration closures disappear. microblock/MicroblockPlacement.scala is next.
• Characterized MicroblockPlacement against untouched Scala. Three plain-JVM cases freeze the exact six-type hierarchy, constructors, fields, callable descriptors, companion and defaults. Four Forge cases freeze external placement, internal/opposite-slot selection, in-place expansion, custom-placement precedence and consumption.
• Ported the six retained types directly to Java. The only Scala source caller now names MicroblockPlacement$.MODULE$ explicitly; no runtime class was added or removed and every callable public member matches the reference.
• A clean build passes all 211 plain-JVM tests and the Java 8 Forge server passes all 102 tests. microblock/PlacementGrids.scala is next.
• Characterized PlacementGrids against untouched Scala. Five plain-JVM cases freeze the exact nine-class trait, helper, configurable-grid, facade and companion surface plus every face/corner/edge selection boundary on all six hit sides. The tests call ProjectBlue's load-bearing static facade directly.
• Ported all nine retained types to Java, preserving PlacementGrid$class for old Scala forwarders and using safe Java defaults for the three concrete trait methods. The three remaining Scala object-value users now name their companions explicitly.
• A clean build passes all 216 plain-JVM tests and the Java 8 Forge server passes all 102 tests. The jar class list is unchanged and all callable public descriptors match the reference. microblock/BlockMicroMaterial.scala is next.
• Characterized BlockMicroMaterial against untouched Scala. Five plain-JVM cases freeze all five retained public types, exact methods/fields/client annotations, material delegation, thread-local render-helper state and inventory pipeline. A frozen Scala 2.11.5 consumer calls both load-bearing companions; one Forge case freezes registered block semantics and dedicated-server side stripping.
• Ported the material base, both facade/companion pairs and ThreadState to Java. The GuideNH-targeted private final block/meta fields, public (Block, int) constructor, Scala Seq registration overloads, historical meta-0-only overload behavior, render pipeline and Angelica override lifecycle are unchanged.
• A clean build passes all 222 plain-JVM tests and the Java 8 Forge server passes all 103 tests. Every callable public descriptor matches the reference; only three unreferenced Scala closure/anonymous classes disappear. microblock/ConfigContent.scala is next.
• Characterized ConfigContent against untouched Scala. Six plain-JVM cases freeze its facade, companion and exact mutable-map field, config-file generation and parsing, alias/range semantics, malformed-line recovery, block registration and IMC filtering/validation.
• Ported the facade and companion directly to Java. Both retained runtime classes and every callable public descriptor match the reference; the seven Scala iteration/parser closure classes disappear. Public file helpers still throw the original IOException instances without adding checked exceptions to their descriptors or source declarations.
• A clean build passes all 228 plain-JVM tests and the Java 8 Forge server passes all 103 tests. microblock/AngelicaCompat.scala is next.
• Added a dependent GitHub Actions job that accepts the EULA in its ephemeral runner and invokes the existing self-validating runFunctionalTestServer task after the shared GTNH build. The Forge suite now gates pull requests and pushes instead of being local-only.
• Characterized AngelicaCompat against untouched Scala. Two plain-JVM cases freeze its exact non-final public surface, unusual Object return descriptors, CapturingTessellator guard, Iris calls and caught ClassCastException fallback.
• Ported the sole class directly to Java while retaining BoxedUnit.UNIT on the normal path and Unit$.MODULE$ on the fallback path. Both jars contain the same runtime class and every callable descriptor matches the reference.
• A clean build passes all 230 plain-JVM tests and the Java 8 Forge server passes all 103 tests. microblock/ItemSaw.scala is next.
• Characterized ItemSaw and ItemSawRenderer against untouched Scala. Four plain-JVM cases freeze all three runtime types, the reflective private-final harvest field, default and explicit durability, container behavior, renderer gating and supported render-type selection.
• Ported the item, static renderer facade and registered renderer companion directly to Java. All callable public descriptors, singleton/model fields and three runtime classes match the reference.
• A clean build passes all 234 plain-JVM tests and the Java 8 Forge server passes all 103 tests. microblock/MicroblockRender.scala is next.
• Characterized MicroblockRender against untouched Scala. Four plain-JVM cases freeze its facade/companion surface, thread-local face state, cuboid face-mask traversal, no-placement highlight exit and exact transformed-client call opcodes.
• Ported both retained types directly to Java. A clean compile preserves invokevirtual Microblock.setShape and invokeinterface MicroblockClient.getBounds/render; direct face iteration removes three unreferenced Scala anonymous/closure classes.
• A clean build passes all 238 plain-JVM tests and the Java 8 Forge server passes all 103 tests. microblock/MicroblockClass.scala is next.
• Characterized MicroblockClass, CommonMicroClass and its companion against untouched Scala. Three plain-JVM cases freeze the exact hierarchy, constructors, public descriptors, private fields, side annotations, registry semantics and generator call descriptors. Constructor execution remains a Forge-only boundary because generator initialization requires the launch class loader.
• Ported all three retained types directly to Java. Eager base-trait registration, synchronized one-time client-trait registration, part-factory registration order, class IDs, duplicate rejection and both create paths are unchanged. The GuideNH-pinned MicroblockGenerator$.create(MicroblockClass, int, boolean) descriptor remains exact.
• A clean build passes all 241 plain-JVM tests and the Java 8 Forge server passes all 103 tests. The clean reference and port jars contain the same three runtime types and every callable public descriptor matches. microblock/Microblock.scala is the next deliberately high-risk target.
• Characterized the Microblock base, its default-argument companion and all three mixin traits against untouched Scala. Three plain-JVM cases freeze the eight retained type surfaces, fields, constructor/default, signed shape packing, material delegation, item conversion, description/update bytes and core NBT.
• Ported Microblock and Microblock$ directly to Java while moving MicroblockClient, CommonMicroblock and CommonMicroblockClient unchanged to MicroblockTraits.scala. Keeping those load-bearing Scala traits avoids a Java single-inheritance workaround and preserves the existing ProjectRed generator path. Three remaining Scala assignments now call the same public field setters explicitly.
• A clean build passes all 244 plain-JVM tests and the Java 8 Forge server passes all 103 tests, including generated face/hollow parts and the external Scala microblock trait fixture. All eight retained public surfaces match the reference; only two private Scala iteration closures disappear. microblock/FaceMicroblock.scala is next.
• Characterized the face factory, placement singleton and both generated traits against untouched Scala. Two plain-JVM cases freeze all eight retained public surfaces and every placement rule; one Forge case freezes factory identity, all 42 populated bounds and generated face-part behavior.
• Ported the four concrete facade/companion types directly to Java while retaining FaceMicroblock and FaceMicroblockClient unchanged in FaceMicroblockTraits.scala. All callable public descriptors match the reference; the two private Scala bounds-initializer closures disappear.
• A clean build passes all 246 plain-JVM tests and the Java 8 Forge server passes all 104 tests. Recompiled Scala must spell the Java array getter as FaceMicroClass.aBounds()(index); existing binaries still link to the unchanged aBounds(): Cuboid6[] descriptor. microblock/CornerMicroblock.scala is next.
• Characterized the corner factory, placement singleton and generated trait against untouched Scala. Two plain-JVM cases freeze all six retained public surfaces and all 48 slot/side placement mappings; one Forge case freezes factory metadata, all 56 populated bounds and generated shape/slot behavior.
• Ported the four concrete facade/companion types directly to Java while retaining CornerMicroblock in CornerMicroblockTraits.scala. ProjectRed's load-bearing CornerMicroClass$.MODULE$.getClassId() linkage and every callable public descriptor remain exact; the two private Scala bounds-initializer closures disappear.
• A clean build passes all 248 plain-JVM tests and the Java 8 Forge server passes all 105 tests. Recompiled Scala must spell the Java array getter as CornerMicroClass.aBounds()(index); existing binaries still link unchanged. microblock/EdgeMicroblock.scala is next as one Edge/Post source unit.
• Characterized the combined Edge/Post unit against untouched Scala. Two plain-JVM cases freeze all twelve retained public surfaces, state/super accessors and edge-opposite mappings. Three Forge cases freeze both factories, all 84 edge and 12 post bounds, generated behavior, even-size post placement and matching-post expansion.
• Ported the six concrete facade/companion types directly to Java while retaining EdgeMicroblock, PostMicroblock, and stateful PostMicroblockClient in EdgeMicroblockTraits.scala. ProjectRed and UtilitiesInExcess class-ID linkage remains exact; the Post client traversal closure and all trait helpers remain.
• A clean build passes all 250 plain-JVM tests and the Java 8 Forge server passes all 108 tests. All callable public descriptors match the reference; only four private bounds-initializer closures disappear. microblock/HollowMicroblock.scala is next.
• Characterized the Hollow unit against untouched Scala. Two plain-JVM cases freeze all nine retained public surfaces, including the source-visible nested placement-grid relationship and both generated traits. Two Forge cases freeze both 42-entry tables, generated server behavior, every face, connected hollow sizes 1 through 11, and all collision, occlusion and subpart geometry.
• Ported the four concrete placement/factory facade and companion sources directly to Java while retaining HollowMicroblock and the large stateful HollowMicroblockClient in HollowMicroblockTraits.scala. The nested HollowPlacement.HollowPlacementGrid$ remains a real public static nested class rather than merely keeping its binary name.
• A clean build passes all 252 plain-JVM tests and the Java 8 Forge server passes all 110 tests. All nine supported public surfaces match the reference; both retained trait helpers and all seven trait closures are bytecode-identical. Only three private factory table-initializer closures disappear. microblock/TMicroOcclusion.scala is next.
• Characterized MicroOcclusion against untouched Scala. Five plain-JVM cases freeze the facade, companion, three generated-trait surfaces, all valid shrink-side mappings, exhaustive priority/size/transparency decisions, render masks, traversal ranges and the complete TMicroOcclusion decision matrix.
• Ported only the concrete facade and companion to Java. JMicroShrinkRender, TMicroOcclusion and the stateful TMicroOcclusionClient remain Scala; both trait helpers and all five retained Scala types have bytecode-identical disassembly. Direct Java iteration removes the sole private shrink closure.
• A clean build passes all 257 plain-JVM tests and the Java 8 Forge server passes all 110 tests. All seven supported public surfaces and WR-CBE's static recalcBounds descriptor match the reference. microblock/MicroblockGenerator.scala is next.
• Characterized MicroblockGenerator against untouched Scala. Three plain-JVM cases freeze its facade, companion, nested material interface, inherited ASMMixinFactory/ScratchBitSet shape, replaceable thread-local scratch state and load-bearing calls. One Forge case freezes the complete material-added external Scala-trait path.
• Ported the facade, companion and real public static nested IGeneratedMaterial interface directly to Java while leaving the generator and ScalaSignature machinery unchanged. Scratch-bit reuse, base/client selection, material callback ordering, boxed constructor argument and the ProjectRed Scala-trait registration path are unchanged.
• A clean build passes all 260 plain-JVM tests and the Java 8 Forge server passes all 111 tests. The same three runtime classes and every callable public descriptor match the reference, including ProjectRed's companion registration and GuideNH's exact companion create method. multipart/MultipartGenerator.scala is next.
• Characterized MultipartGenerator against untouched Scala. Two plain-JVM cases freeze both public surfaces, private Scala-map descriptors and companion call opcodes. Five Forge cases freeze side-specific hierarchy caches, duplicate/failed registration, scratch clearing, class snapshots/reuse, tile upgrades/downgrades, vanilla-block conversion and a precompiled Scala consumer exercising companion generation and pass-through registration.
• Ported the facade and companion directly to Java. All five Scala maps, both compiler-generated public accessors, the companion-only generateCompositeTile descriptor and side-safe proxy callback remain. Direct iteration removes six private closures; the ASM factory's sole source adjustment explicitly names MultipartGenerator$.MODULE$.
• A clean build passes all 262 plain-JVM tests and the Java 8 Forge server passes all 116 tests. Both supported public surfaces match the reference. multipart/asm/ScratchBitSet.scala is the next isolated support target; the generated microblock traits still require the documented abstract-Java-mixin and side-only-member prerequisites.
• Characterized ScratchBitSet against untouched Scala. Four plain-JVM cases freeze the exact interface/helper surface, lazy allocation, repeated accessor calls, owner/thread isolation, bit preservation/clearing, storage replacement/reinitialization and freshBitSet dispatch through an overridden getBitSet.
• Ported the interface and $class helper directly to Java without changing either generator. All seven callable methods, their abstract/static modifiers and both binary names remain exact; no new API or default methods are introduced. Neither downstream audit contains a reference to this support trait.
• A clean build passes all 266 plain-JVM tests and the Java 8 Forge server passes all 116 tests. The two-type ABI and both generator companions' disassembly match the reference. multipart/asm/ByteCodecs.scala is next as an isolated codec port, leaving signature parsing and trait compilation for separate targets.
• Condensed JAVA_MIGRATION_DIVERGENCES.md from 3,134 to 189 lines, keeping effective runtime, binary and source differences plus one shared classfile section. Removed repeated preservation claims, validation histories and superseded intermediate decisions; the original narrative remains in git history. The workflow now records test results here and updates the divergence ledger only for a genuinely new difference.
• Characterized ByteCodecs against untouched Scala in five plain-JVM cases: exact facade/companion ABI, every byte value and packing remainder, zero escaping, extra decoded padding, signed shifts and partial writes before malformed input fails. The baseline also rejects a raw 0xBF escaped into a lone 0xC0; that behavior is preserved.
• Ported the facade and companion directly to Java, retaining the original LAMP/EPFL attribution and unrolled algorithm. The signature-parser source is unchanged; its recompiled calls now use the retained static facade.
• Clean formatting/checkstyle/build passes all 271 plain-JVM tests, and Java 8 Forge passes all 116 tests including external Scala-trait generation. Both packaged types have Java source markers, Java 8 class versions and identical callable public names/descriptors. An additional one-off differential run compared all two-byte inputs across all six methods plus randomized lengths through 256, null and invalid decode lengths: all 450,790 cases matched on return values, exception types and full mutated arrays. No new difference needs a separate ledger entry. multipart/asm/ASMImplicits.scala is next; compiler behavior changes remain separate work.
• Characterized ASMImplicits against untouched Scala in five plain-JVM cases: all six runtime surfaces, identity conversions, node names, null handling, BitSet self-replacement and clear-before-failure, independent plain-BitSet copies, and boxed equality/hash behavior. Neither consumer audit identifies a direct external user.
• A follow-up characterization, also passed against the saved Scala reference jar, pins virtual BitSet.equals dispatch even for identical references. The Java implementation uses an explicit null check here because Objects.equals would skip that call.
• Ported the facade, companion and four nested value-class/extension types to two Java sources, retaining every callable public name, descriptor and modifier. Seven Scala compiler/factory call sites now explicitly invoke the helpers; compiler algorithms and trait registration are unchanged. The ledger records the lost implicit syntax and the Java publication rule: explicitly constructing either public extension companion no longer replaces MODULE$, verified against the reference in isolated class loaders.
• Clean formatting/checkstyle/build passes all 276 plain-JVM tests, and Java 8 Forge passes all 116 tests. All six helpers have Java source markers and Java 8 class versions; compiler/factory public descriptors and the full 464-class packaged inventory match the reference. MultipartGenerator$ disassembly is unchanged. The next bounded target is extracting DebugPrinter from ASMMixinCompiler.scala, leaving the compiler algorithms for later.
• Extracted DebugPrinter into a Java facade and companion, retaining all five methods on each and the companion singleton field. Configuration/default gating, immediate-child cleanup, dump paths/content and the 16,000-byte logging threshold are unchanged. Only three compiler call sites explicitly name DebugPrinter$.MODULE$.
• Per the current user instruction, no tests were added. A clean formatting/checkstyle/build passes all 276 existing plain-JVM tests; the Java 8 Forge suite passes all 116 tests with dumping both enabled and disabled. Against the saved 1faf0dd baseline, all 39 generated dump filenames and SHA-256 hashes and all six ordered byte-count messages match. The disabled run leaves the existing dump contents and modification times untouched and retains those log messages. Restored the original local debug_asm=true setting afterward.
• Both converted types have Java source markers and Java 8 class versions, and all callable public names/descriptors match. Removing the private cleanup closure shifts the compiler's private closure numbering; all 64 compiler types' disassembly matches after that renaming alone. The packaged inventory drops from 464 to 463 classes. No new divergence needs a ledger entry. ByteCodeReader in multipart/asm/ScalaSignature.scala is the next isolated target.
• Extracted ByteCodeReader to one Java source, retaining its public constructor, all nine methods and both private fields. Accessor/reader calls remain virtual, the generic advance(int, A) call remains eager, and byte unboxing retains Scala's null-to-zero behavior for overrides. String reads use a standard-library slice with the original default charset and Scala drop/take clamping; signed-byte decoding, integer overflow and unchecked failures are preserved. No signature-model or compiler algorithm changed.
• No tests were added, per the current user instruction. A clean formatting/checkstyle/build passes all 276 existing plain-JVM tests; Java 8 Forge passes all 116 tests, including external Scala-trait generation. All 39 generated dump names and SHA-256 hashes match the saved b45527e reference.
• The Java 8 packaged reader retains every callable public name/descriptor and the complete 463-class inventory is unchanged. All 140 retained ScalaSignature, ScalaSigReader and ASMMixinCompiler types have identical disassembly. Recompiled Scala uses pos_$eq and advance(length, value); the latter source-syntax difference is recorded in the ledger. ScalaSigReader in multipart/asm/ScalaSignature.scala is the next isolated target.
• Extracted ScalaSigReader to a Java facade and companion, retaining all five methods on each and the singleton field. Decode still uses the platform charset; encode keeps UTF-8 and the reference's trailing-byte truncation, including empty input. Annotation reads still use ScalaSignature.Bytes$, writes return the replaced list value, and lookup returns the first match as a Scala Option with the original malformed-entry failures.
• Replaced Scala array slicing and annotation traversal with standard-library operations. Only two compiler calls explicitly name the companion; no signature-model, byte-codec or compiler algorithm changed. Both Java 8 public surfaces match the saved 9f92704 reference, and all 137 retained signature/compiler types have identical disassembly. Only the private annotation-search closure disappears, taking the packaged inventory from 463 to 462.
• No tests were added, per the current user instruction. A clean formatting/checkstyle/build passes all 276 existing JVM tests; Java 8 Forge passes all 116 tests, including external Scala-trait generation. All 39 generated dump names and SHA-256 hashes match the reference. No new ledger entry is needed. multipart/asm/ASMMixinFactory.scala is next as a single factory port before the larger nested signature model and compiler.

2026-09-02

• Ported ASMMixinFactory directly to Java, retaining the Scala Seq constructor/argument descriptors, all six fields, synchronized construction, live parameter conversion, copied cache keys, generated-name sequence and both Scala- and Java-trait registration paths. Parent validation and callback/registration order remain unchanged; reflection failures escape as the same exceptions without adding checked exceptions to the public methods.
• Kept the reference's public JVM callbacks and both public mangled parent helpers. The retained Scala subclass needs only an explicit empty parameter sequence and public override syntax. Its companion and five closure types have identical disassembly; Scala adds four static facade forwarders without changing any existing entry. The ledger records that additive surface and the Scala-source syntax changes.
• No tests were added, per the current user instruction. Clean formatting/checkstyle/build passes all 276 existing JVM tests; Java 8 Forge passes all 116 tests, including the external Scala-trait and generated-tile fixtures. All 39 generated dump names and SHA-256 hashes match the saved f7be2b1 reference. Both generator companions and all 137 signature/compiler types have identical disassembly. Removing two private parent-traversal closures reduces the packaged inventory from 462 to 460 classes. multipart/asm/MultipartMixinFactory.scala is next, with the signature model and compiler algorithms still reserved for later targets.
• Ported MultipartMixinFactory to a Java facade/companion pair, retaining all ten facade methods, the singleton, both public callback overrides and the two companion-only mangled helpers. No other production source needed an adjustment. The compiler, signature model and stack analyser remain unchanged.
• Preserved the non-transient-field snapshot, existing copyFrom guard, generated delegate binding/removal, single-implementor gate, inherited-method override precedence, names, logging and registration order. The method collector retains Scala's immutable map and ordered inherited-entry buffer, preserving emitted method order; the public bridge helper still updates its supplied ObjectRef before emitting instructions. onCompiled keeps the side-safe MultipartGenerator$.MODULE$ call.
• No tests were added, per the current user instruction. Formatting/checkstyle/build passes all 276 existing JVM tests; Java 8 Forge passes all 116 tests, including pass-through delegation/copying and the frozen Scala consumer. Both Java 8 public surfaces match the saved 13ec2f5 reference. All 39 generated dump names and SHA-256 hashes match, and all 185 retained compiler/model/base-factory/generator types have identical disassembly. Only five private closures disappear, reducing the packaged inventory from 460 to 455 classes. The existing ledger row now describes the retained Java forwarders; no new divergence was added. multipart/asm/ScalaSignature.scala is next as the remaining parser/nested-model unit, with ASM compiler algorithm changes still deferred.
• Extracted ScalaSignature table decoding, name and literal evaluation, collection and object/class lookup into one package-private Java helper. The Scala shell retains the complete nested model and five generic construction branches. That boundary is required: primitive literal case classes expose both primitive and erased Object value() methods, which Java cannot declare together, while Java misreads the outer parameter in five Scala 2.11 generic inner constructors. A full model port is deferred until it has an explicit bridge strategy.
• The parser keeps direct case-class construction, path-dependent return types, Scala List/IndexedSeq/Option results, table mutation behavior, annotation grouping, signed literal conversion and the existing partial tag interpretation. All 69 retained signature types' public names, descriptors and generic declarations match the saved 1ad2b0f reference. The disassembly of 188 otherwise unchanged model, compiler, analyser, factory and generator types is identical; all 39 generated dump names and SHA-256 hashes also match.
• No tests were added, per the current user instruction. Formatting/checkstyle/build passes all 276 existing JVM tests and Java 8 Forge passes all 116 tests, including the external Scala-trait path. Four private parser/lookup closures are replaced by one Java helper, reducing the packaged inventory from 455 to 452 classes and leaving 206 Java files plus 9 Scala files / 1,883 nonblank Scala lines. No new compatibility divergence needs a ledger entry. multipart/asm/StackAnalyser.scala is the next bounded target; keep its control flow and nested model separable.
• Backfilled, on request, the characterization tests the six ports from b45527e to 8581d30 had skipped. Six new suites in src/test/java/codechicken/multipart/asm/ add 32 plain-JVM tests, taking that suite from 276 to 308. ByteCodeReader and the signature parser are covered by behavior; ScalaSigReader by round trips, annotation lookup and its replaced-value result. Debug initialization and generator execution need Forge, so those tests pin public surfaces, fields and bytecode constants and calls, leaving generated tiles, pass-through delegation and Java-trait copyFrom to the Forge suite.
• Ran the backfill against src/main restored from 1faf0dd: it compiles against the untouched Scala and 45 of 46 tests pass. The only failure is MultipartMixinFactory's facade method set, which is the four additive static forwarders already in the ledger. Two assertions were relaxed to hold on both trees: the facade private constructors Scala never emitted, and the DebugPrinter$ directory cleanup Scala emitted as a closure class.
• Two behaviors were pinned that inspection had not recorded. ScalaSigReader.encode drops the final 7-bit group, so a decode round trip is exact only when that group is empty; a payload ending in a high-bit byte does not survive it. ScalaSignature.evalS throws MatchError on an unknown tag while eval returns the table entry unchanged.

2026-09-03

• Addressed the three backfill review findings without changing production code. The lossy signature round trip now asserts the exact reference bytes [0, 62], rather than accepting any result different from [0, 0xfe].

• Replaced the two presence-only DebugPrinter JVM checks with three Forge behavior tests for both config modes: directory creation, immediate-child-only startup cleanup, dump gating/naming/content and cumulative 16,000-byte logging boundaries (including an empty input and a single input crossing two boundaries). An isolated copy changes only the hard-coded output path to @TempDir; config and logger state are restored and live dev dumps are untouched. A temporary fault-injection run removing deletion and reversing dump/log guards failed all three new printer tests; those production edits were then restored.

• Replaced the copyFrom call-presence check with three Forge tests invoking the actual completer. They assert byte-for-byte no-ops for empty/transient-only nodes and an existing method, then exact emitted super-call/guard/field order, transient exclusion and idempotence for mixed fields. Corrected the coverage claims: singleton construction is headless, but generation reaches Forge through ObfMapping; earlier dump comparisons were one-off checks.

• Verification baseline is now 305 JVM / 122 Forge tests: three weak JVM checks moved to six focused Forge checks. Formatting/checkstyle/build and the Forge suite pass; all 39 generated dump hashes and the dev config are unchanged. No production ABI, source counts or next target changed. multipart/asm/StackAnalyser.scala remains next, using explicit migration-test authorization and separate characterization and refactor commits.

• Characterized StackAnalyser against untouched Scala in 15 plain-JVM tests, committed separately as a6aca65. The baseline build passed 320 JVM tests and the Forge suite passed 122. The new tests exercise receiver/parameter initialization, narrow/wide slot aliases, partial failures, every duplication opcode, typed constants, case-class equality/copy/products, instruction provenance, loads/stores/increments, arithmetic/casts, arrays, fields, calls, branches/switches/returns, handler precedence, unsupported-node behavior and overridable default-argument dispatch.

• Extracted analyser control flow (setL, pop, insert, popArgs, visitInsn) into package-private Java StackAnalyserLogic. The Scala shell retains construction/state, default-argument bridges, simple accessors and the complete nested model. An isolated Scala 2.11.5 probe rejects a Java class alongside its same-name Scala companion; completing the model requires a coordinated class/companion conversion rather than replacing the class independently. The retained ScalaSignature model and its primitive/erased bridges are untouched.

• Preserved current opcode behavior, including wide DUP2 expansion, int-conversion/comparison/INSTANCEOF result types, reference-array descriptor construction, reversed multidimensional size capture and NEWARRAY's existing MatchError. Virtual calls still use the Scala default-argument getters. No compiler algorithm, optimization or unrelated bug fix is included.

• Saved the pre-port dev jar, Scala source, test reports and generated dumps under ignored run/migration-stack-analyser-reference/. All 40 named analyser surfaces match by member name, descriptor, modifiers, generic declarations and private fields; the other 39 named model/companion classfiles are byte-identical, preserving their serialized and Scala-facing behavior. All 199 retained ASM/generator disassemblies and all 39 generated dump names/hashes match. An additional one-off comparison of 8,960 opcode/node/stack combinations matches expression trees, types, aliases, instruction bindings, locals, exceptions and partial mutation.

• Formatting/checkstyle/build and Forge pass, including a clean build after stopping Gradle: 320 JVM / 122 Forge tests, zero failures/errors/skips. All characterization tests remain unchanged after the port. The forced Scala compilation version guard is retained, and all five @Mod version annotations match both clean packaged jars. Two unreferenced traversal closures become one Java helper (452 to 451 packaged classes); sources now total 207 Java files and 9 Scala files / 1,726 nonblank Scala lines. No new compatibility divergence is introduced. Next is ASMMixinCompiler.scala, bounded to ClassInfo/MethodInfo metadata lookup and traversal, with fresh characterization before touching its Forge-initialized state and no trait-rewriting algorithm changes.

• Characterized the compiler metadata unit before modification in abdf0b0: six JVM cases cover hierarchy order and diamond duplicates, parent-view capture/laziness, strict/view concatenation, virtual selection and short-circuiting, mutable node metadata, reflection order/descriptors/exceptions and case-class outer owners. Five Forge cases cover bytecode versus reflection roots, exact string-key caching and name-only node overloads, null/failure caching, internalDefine invalidation and Scala trait/companion metadata. Untouched Scala passes 326 JVM / 127 Forge tests.

• Extracted metadata lookup, cache population, parent flattening, method concatenation/selection, interface/method mapping and exception-name copying into package-private Java ClassInfoLookup. The same Scala collection operations and builders preserve result representations, laziness, traversal order and virtual dispatch. The nested model, scalar accessors, state, implicit overloads and construction callbacks remain in Scala; no compiler composition, trait registration/rewriting, stack-analysis or signature-decoding algorithm changed.

• Found and retained two necessary source bridges. javac cannot name the concrete metadata classes nested under ClassInfo$: it expects an extra $ absent from their existing binary names. Scala's IterableLike.view() also has an Object generic return signature but an IterableView descriptor; calling it from Java emits a nonexistent Object-returning method. Construction and the initial .view call stay Scala. Path-dependent ClassSymbolRef travels through an Object parameter and is cast back only at its retained Scala construction boundary.

• Preserved existing quirks exposed by characterization: dotted/slashed keys have independent metadata cache entries, internalDefine invalidates only the normalized key, null names are cached as null while load failures are not, bytecode roots can return Some(null), and the StackAnalyser$ companion's superclass/interface queries throw ClassCastException in the current signature model. These are unchanged behavior and do not add divergence entries.

• Saved the pre-port source/jar, reports and 40 generated dumps in ignored run/migration-class-info-reference/. All 16 named compiler APIs match by public/protected member names/descriptors/modifiers/generic declarations and private fields. All four metadata case-class/companion serialization IDs match. All 205 other named compiler methods and 36 algorithm closures match after normalizing private closure and captured-variable numbering; 137 ASM/generator classes outside the compiler have identical disassembly. All 40 dump names/hashes match, including the new deterministic cache-invalidation fixture; the local dev configuration is unchanged.

• Formatting/checkstyle/build and Forge pass, including a clean build after stopping Gradle: 326 JVM / 127 Forge, zero failures/errors/skips, with the characterization tests unchanged after the port. The forced Scala compilation guard is retained and all five @Mod annotations match both clean packaged jar versions. Private implementation closures become the helper/callbacks and the packaged inventory falls from 451 to 450. Sources now total 208 Java files and 9 Scala files / 1,714 nonblank Scala lines. Next is the bounded descriptor/bridge-emission helper unit in ASMMixinCompiler.scala: seperateDesc, staticDesc, finishBridgeCall, writeBridge and writeStaticBridge, with fresh characterization and no composition/trait-rewriting algorithm changes.

• Added eight Forge behavior tests for the descriptor/bridge helpers and committed them separately as 5d611e0. All pass against untouched Scala: descriptor splitting and receiver insertion, every argument/return category, local-slot widths, invocation flags, instruction order, maxima, partial visitor failures, overridable metadata getter order and descriptor rereads. Generated executable bridges verify virtual, special, interface and Scala-style static-helper dispatch with mixed wide/reference arguments. The original compiler singleton requires a Forge LaunchClassLoader; these tests therefore use the existing Forge harness. Baseline: 326 JVM / 135 Forge.

• Extracted only seperateDesc, staticDesc, finishBridgeCall, writeBridge and writeStaticBridge into Java ASMBridgeEmitter, retaining their Scala entry points and exact ABI. No composition, trait-rewriting, stack or signature-decoding algorithm changed. Existing descriptor-validation gaps, malformed-input exception types, unnormalized owner strings, independent bridge/callee descriptors and callback order are preserved.

• Saved the pre-port jar/source, reports and 40 generated dumps under ignored run/migration-bridge-reference/. All 16 named compiler APIs match by names/descriptors/modifiers/generic signatures and private fields; 14 named classfiles are byte-identical. All 214 other named compiler methods, 35 algorithm closures and 143 ASM/generator disassemblies outside the compiler match. All 40 dump names/hashes match and the dev configuration is unchanged. One private bridge closure is replaced by the Java helper, keeping 450 packaged classes. No new ledger entry is needed. Sources total 209 Java files and 9 Scala files / 1,689 nonblank Scala lines. Next: ASMMixinCompiler.getSuper recognition/lookup, with fresh characterization and no algorithm fixes mixed into its port.

• Formatting/checkstyle/build and the full Forge suite pass, including a clean build after stopping Gradle: 326 JVM / 135 Forge, zero failures/errors/skips. The eight characterization tests are unchanged after the port, and the clean jar repeats the API/disassembly/dump matches above. The forced Scala-compilation version guard is retained; all five @Mod annotations match both packaged jar versions. External Scala-trait coverage remains green and the existing manual client checks and Java-source bridge limitations remain outstanding.

• Added six Forge characterization cases for ASMMixinCompiler.getSuper, passing on untouched Scala and committed separately as c0df2e0: owner/name filter short-circuiting, greedy Scala super-name stripping, exact inherited signature selection and visibility, receiver recognition, argument indexing, failure paths, stack preservation, virtual getter/callback order, returned option identity and descriptor rereads. Baseline: 326 JVM / 141 Forge. The compiler singleton requires Forge initialization, so these behavior tests use its existing harness.

• Moved only getSuper into the existing Java ClassInfoLookup, retaining the public Scala entry point and Option.flatMap callback dispatch. The current argument-count/stack-slot mismatch for wide arguments remains, as do the lack of invocation-opcode and This.owner validation and the limited target-owner check. The caller's INVOKESPECIAL guard, all trait rewrites and metadata/model behavior remain unchanged; algorithm fixes are separate.

• Saved reference source/jar, reports and 40 generated dumps in ignored run/migration-super-reference/. All 16 named compiler APIs retain their names/descriptors/modifiers/generic signatures and private fields; 14 named classfiles are byte-identical. All 218 other named compiler methods, 34 algorithm closures, 17 existing metadata-helper methods and 143 other ASM/generator disassemblies match. All dump names/hashes match. One private Scala closure becomes a Java callback, leaving 450 packaged classes and no new divergence entry. Sources total 209 Java files and 9 Scala files / 1,675 nonblank Scala lines. Next: ASMMixinCompiler.listSideOnly annotation filtering, characterized first.

• Formatting/checkstyle/build and Forge pass, including clean verification after stopping Gradle: 326 JVM / 141 Forge, zero failures/errors/skips. Characterization tests remain unchanged. The clean jar repeats the API/disassembly/dump matches, the local dev config is unchanged, and all five @Mod versions match both packaged jar versions with the forced Scala-compilation guard retained. External Scala-trait tests remain green; existing manual client checks and Java-source model-bridge limitations remain outstanding.

• Reviewed the reported TileMultipart compatibility findings against cacc9a3^. Confirmed all three equality changes and the dropped virtual light query. Restored null-safe Scala equality in change notifications and replacement/removal filtering, removed all equal entries, and retained Scala contains/indexOf behavior. Removal still reports the first matching index and invokes hooks/detaches only the requested part, as Scala did.

• Restored getLightValue() before preRemove() and corrected the related early/stale snapshot reads: filtering now sees list updates from those callbacks, while empty/ticking decisions see updates from removal callbacks. Seven JVM regression tests cover these behaviors, including light-query exceptions and missing-part rejection. Six failed against the unfixed Java port; all seven pass against the complete original Scala class and fixed Java. The reference class needed only explicit Java getter/setter, singleton and boxed-function call syntax for migrated dependencies. Sources, compilation/test logs and reports are saved in ignored run/tile-compatibility-review/.

• Added brief comments explaining the profiled direct-list traversal and arbitrary-Seq fallback. No traversal or compiler algorithm changed. The existing NEWARRAY limitation, forced Scala-compilation guard and manual client checklist require no change in this review. All 450 class APIs match by names/descriptors/modifiers/generic signatures and private fields. All 40 generated dumps retain the same instructions: 39 hashes are exact, with only debug line numbers changed in the redstone helper by its added comment. These fixes restore the reference behavior and need no divergence entry. The next migration target remains ASMMixinCompiler.listSideOnly.

• Clean formatting/checkstyle/build and the full Forge suite pass after stopping Gradle: 333 JVM / 141 Forge tests, zero failures/errors/skips. The clean jar repeats the API/generated-output checks above; all five @Mod annotations match both packaged jar versions. The forced Scala-compilation guard is unchanged. Review corrections were committed as 5af333c and fast-forwarded onto algent/java; subsequent migration work continues on that branch.

• Added six Forge characterization tests for ASMMixinCompiler.listSideOnly, passing against untouched Scala and committed separately as b288d3d. A compiled Scala fixture covers actual signature annotations; synthetic signatures freeze exact-name selection, current-side exclusion, unknown/null enum names, owner-name deduplication, immutable result snapshots, short-circuiting and missing/wrong/null-value failures. Virtual accessor mutations and exceptions prove all filter predicates run before any selected owner is read. Baseline: 333 JVM / 147 Forge. The original singleton and side initialization require the existing Forge harness.

• Extracted only annotation filtering into the existing Java ClassInfoLookup, retaining the Scala entry point and separate Scala collection filter, map and toSet dispatch/builders. Trait registration, rewriting, composition and signature decoding remain unchanged. Unknown enum names, null owner names and malformed-input failures keep their original behavior; no algorithm fixes are mixed in and the external Scala-trait/model bridges remain intact.

• Saved the pre-port source/jar, reports and 40 generated dumps under ignored run/migration-side-only-reference/. All 16 named compiler APIs match by member names/descriptors/modifiers/generic signatures and private fields. All 218 other named compiler methods, 32 algorithm closures, 18 existing metadata-helper methods and 144 other ASM/generator disassemblies match. Retained compiler models have shared-source debug line shifts only. All 40 dump names/hashes match exactly. Two private Scala closures become two Java callbacks, leaving 450 packaged classes; the shared compiler entry covers this and no new divergence entry is needed. Sources total 209 Java files and 9 Scala files / 1,664 nonblank Scala lines.

• Formatting/checkstyle/build and Forge pass, including clean verification after stopping Gradle: 333 JVM / 147 Forge, zero failures/errors/skips. The six characterization tests are unchanged after the port. The clean jar repeats the API/disassembly/dump matches; the local dev config and forced Scala-compilation guard are unchanged. All five @Mod versions match both packaged jar versions. External Scala-trait tests remain green; existing manual client checks and Java-source model-bridge limitations remain outstanding. Next: Scala-trait registration metadata, getAndRegisterParentTraits and registerScalaTrait, characterized first with no registration algorithm changes.

• Added twelve Forge characterization tests for Scala-trait registration, passing against untouched Scala and committed separately as d2276c4. Real compiled Scala traits exercise parent/field/method/super metadata and side selection; synthetic signatures pin cached identity/nulls, lookup-before-registration ordering, duplicate parents, partial caches after failure, owner value equality, filtering precedence, first exact method identity, preceding accessor selection and mutation of the publication key by a metadata callback. Baseline: 333 JVM / 159 Forge.

• Extracted getAndRegisterParentTraits and registerScalaTrait into Java ScalaTraitRegistration, retaining their exact Scala entry points and four small callbacks for nested metadata type tests/casts and accessors. A javac probe confirms it expects ASMMixinCompiler$ClassInfo$$ScalaClassInfo for the existing nested model, whose binary name has only one $ between ClassInfo and ScalaClassInfo. The model stays in Scala. The class-symbol callback uses Object at the joint-compilation boundary and the retained ClassSymbolRef inside Java. No named model or bridge is removed; collection dispatch/builders, cache publication and registration algorithms are unchanged.

• The compiled fixtures exposed the existing Scala String alias limitation: its parameter descriptor becomes Lscala/Predef/String;, which cannot match the classfile method. A dedicated test freezes the exact registration failure, while the successful fixture spells the type java.lang.String. Missing accessors/methods and partial parent registration on failure remain unchanged. These are reference behaviors, not new divergences or fixes.

• Saved pre-port source/jar, reports and 40 generated dumps in ignored run/migration-scala-trait-reference/. All 16 named compiler APIs match by member names/descriptors/modifiers/generic signatures and private fields; 14 named classfiles are byte-identical. All 217 other named compiler methods, 28 other algorithm closures, 19 existing metadata-helper methods and 147 other ASM/generator disassemblies match. All 40 dump names/hashes match exactly. The Java helper/callbacks and retained Scala type bridges change the packaged inventory from 450 to 455 classes; private artifacts are covered by the shared compiler entry, so no new ledger entry is needed. Sources total 210 Java files and 9 Scala files / 1,629 nonblank Scala lines.

• Formatting/checkstyle/build and Forge pass, including clean verification after stopping Gradle: 333 JVM / 159 Forge, zero failures/errors/skips. The twelve characterization tests are unchanged after extraction. The clean jar repeats the API/disassembly/dump comparisons; the local dev config and forced Scala-compilation guard are unchanged. All five @Mod versions match both packaged jar versions. External Scala-trait tests remain green; existing manual client checks and Java-source model-bridge limitations remain. Next: getBytes, classNode and internalDefine class-byte loading/cache helpers, characterized first and without loader/cache algorithm changes.

• Investigated the 2026-09-03 ProjectRed placement crash on 60d060a. The failure occurs in multipart TESR rendering, not registration: the earlier client-trait port (970e888) left an INVOKEVIRTUAL call to TileMultipartClient.hasDynamicParts()Z in MultipartRenderer$, while Forge exposes that type as an interface. A raw-jar audit of calls/field accesses to all eight Java-authored tile trait inputs found this one unsafe external call. The recent Scala-trait registration extraction is not its cause.

• Added four Forge regression cases executing the shipped renderer method body against generated client tiles. Only GL/pass services and the final drawing callback are recorded, because the dedicated server strips the actual TMultiPart.renderDynamic method. Static and empty early returns, non-client rejection, render-state setup and exact dynamic coordinates/frame/pass are covered. The final tests were rerun against the broken renderer: both nonempty cases raise the same IncompatibleClassChangeError as the supplied crash. This closes the call-site gap left by earlier client-tile tests, which invoked trait methods through method handles.

• Added a default-false TileMultipart.hasDynamicParts() base hook and routed the renderer's flag query through it. Generated client tiles already supply the overriding getter. The original checked client-trait cast and guards remain; no generator algorithm or runtime trait interface changes. The additive base method is recorded in the existing divergence entry. Reference source/jar, reproduction reports and scripts are saved under ignored run/renderer-compatibility-review/; the manual checklist records the failed full-client check and required retest.

• Clean formatting/checkstyle/build and Forge pass after stopping Gradle: 333 JVM / 163 Forge tests, zero failures/errors/skips. All 455 class APIs match except the new base hook, and 3,713 other method bodies match. No unsafe external calls/field accesses to the eight transformed Java tile inputs remain. All 40 generated outputs keep their instructions: 34 names/hashes are exact; six composites are renumbered by the new tests' earlier client tile construction. The dev config and forced Scala-compilation guard remain unchanged; all five @Mod versions match both packaged jars. The user subsequently confirmed that placement with the supplied fix no longer crashes; the broader static/dynamic drawing and part-update checklist remains open.

• Added ten Forge characterization tests for ASMMixinCompiler.getBytes, classNode and internalDefine, passing against untouched Scala and committed separately as 4928cdf. A recording LaunchClassLoader exercises the real reflective transformer chain; the real FML remapper is tested with a temporary mapping/environment flag. Fixtures restore loader, caches and flags. They pin dotted/slash names, remapper input and transformer argument order, exclusion short-circuiting, raw-array identity, nulls, reflection wrapping, expanded frames, fresh node parsing, cached parse failures versus retried load failures, normalized metadata invalidation and publication before dump failure. internalDefine still stores bytes without defining a JVM class. Baseline: 333 JVM / 173 Forge.

• Extracted those three helpers into Java ClassBytes, retaining the Scala singleton, exact entry points and private cache fields. Scala find/getOrElseUpdate dispatch remains, as do the load-before-exclusion and publish/invalidate-before-dump ordering. The helper resolves the retained MODULE$ internally: joint compilation cannot expose the Scala-authored ASMMixinCompiler$ as a Java parameter to a Scala caller. This follows the earlier metadata helper pattern and changes no consumer API. Reflective class definition, startup initialization, trait registration/rewriting, composition and compiler algorithms are unchanged.

• Saved pre-port source/jar, reports, 41 generated dumps and reproducible checks in ignored run/migration-class-bytes-reference/. All 423 non-closure class APIs match by names/descriptors/modifiers/generic signatures and private fields, including all 16 named compiler APIs. All 3,615 other method bodies and 30 other compiler closures match after normalizing private closure numbering. All 41 generated dump names/hashes match exactly. Two private Scala closures become two Java callbacks plus their helper, taking the packaged inventory from 455 to 456 classes. The shared compiler ledger entry covers this, with no new effective divergence. Sources total 211 Java files and 9 Scala files / 1,597 nonblank Scala lines.

• Formatting/checkstyle/build and Forge pass, including a clean build after stopping Gradle: 333 JVM / 173 Forge, zero failures/errors/skips. All ten characterization tests remain unchanged. Clean APIs and dumps repeat the matches above; the dev config and forced Scala-compilation guard are unchanged. All five @Mod versions match both packaged jar versions. External Scala-trait tests remain green; existing manual client checks and Java-source model/trait limitations remain. Next: ASMMixinCompiler.define, characterized first for publication/debug accounting, reflective definition and failure ordering, without algorithm changes.

• Added ten Forge characterization tests for ASMMixinCompiler.define, passing on untouched Scala and committed first as 4d59900. They execute real JVM definitions in isolated LaunchClassLoaders and restore compiler caches, loader/reflection state and debug state. Tests freeze bytecode-name versus cache-key handling, delayed class initialization, exact byte publication, metadata invalidation, byte accounting and failures before/after reflection. Real duplicate definitions remain InvocationTargetException wrapping LinkageError; direct linkage errors from reflective class initialization exercise the original case-sensitive duplicate guard, including its null-message NullPointerException. Dump/accounting failures remain outside that guard. These quirks are preserved, not fixed.

• Moved only define into the existing Java ClassBytes, retaining its exact Scala entry point and the loader's startup initialization. Class composition, trait rewriting and external Scala-trait/model bridges are unchanged. Reference source/jar, reports, 42 dumps and verification scripts are in ignored run/migration-define-reference/. The 456-class inventory is unchanged; all 426 non-closure APIs (including 16 named compiler APIs), 3,628 other method bodies and 30 compiler closures match. All 42 generated dump names/hashes match exactly. No new divergence is needed.

• Formatting/checkstyle/build and Forge pass, including clean verification after stopping Gradle: 333 JVM / 183 Forge, zero failures/errors/skips. The characterization tests, dev config and forced Scala-compilation guard are unchanged; all five @Mod versions match both packaged jar versions. Sources total 211 Java files and 9 Scala files / 1,583 nonblank Scala lines. Next: ASMMixinCompiler.mixinClasses, characterized for composition/constructor/dispatch and generated output before extraction; keep compiler algorithm fixes separate.

• Consolidated the active plan/handoff after the reflective-definition port. The dated findings remain intact in this history, duplicated completed-port handoff summaries were removed, and current phase/status text was refreshed. The manual checklist now names verified consumer items, including the inverted ProjectRed lamp requirement.

2026-09-03 — composite class generation

• Added eight Forge characterization tests for ASMMixinCompiler.mixinClasses, passing on untouched Scala and committed first as 1c9cd65. They execute generated JVM classes and freeze empty selection, constructor forwarding, diamond linearization, initialization, field storage and mangling, method/super dispatch, covariant bridges, implemented-interface order and failures before or during definition. The reference also confirms the existing verifier failure for generated long and double field getters whose maximum stack remains one.
• Moved only composite generation into Java MixinClassGenerator, retaining the Scala entry point and the unusual public compiler-local allParents helper descriptor. External Scala-trait registration, Java-trait rewriting and compiler algorithms are unchanged. The 456-class reference becomes 442 classes: 16 unreferenced target closures become the Java helper and one private callback. The shared classfile ledger covers this with no new effective divergence.
• Saved the pre-port source/jar, reports, 79 generated outputs and checks in ignored run/migration-composition-reference/. Clean verification after stopping Gradle matches all 426 non-closure APIs, 3,628 non-target method bodies, 13 other compiler closures and every generated output name/hash. Formatting, checkstyle, build and Forge pass: 333 JVM / 191 Forge, zero failures/errors/skips. All five packaged @Mod versions, the forced Scala-compilation guard and dev config remain correct. Sources total 212 Java files and 9 Scala files / 1,444 nonblank Scala lines. Next: ASMMixinCompiler.registerJavaTrait, characterized before extraction; abstract mixins, side-only filtering and the wide-field defect remain separate compiler changes.

2026-09-03 — Java trait rewriting

• Added nine Forge characterization tests for ASMMixinCompiler.registerJavaTrait, passing against untouched Scala and committed first as 85ad2e4. They freeze rejected shapes, exact input cloning, constructors, initialization, field accessors, private/public methods, virtual self calls, super dispatch, parent traits, source metadata, implemented-interface deduplication, side-only annotation retention and partial publication after definition errors. They also preserve the existing primitive-NEWARRAY, foreign-field and inherited-call failures.
• Moved only rewriting into Java JavaTraitRegistration; registration dispatch and the Scala MixinInfo shell remain in the singleton. Abstract mixins and Java-path side filtering remain planned behavior changes. Nine unreferenced target closures and local compiler helpers become the Java helper, its context and callback, taking the packaged inventory from 442 to 436 classes. The shared classfile ledger covers these artifacts; no effective divergence was added.
• Saved the pre-port source/jar, reports, 102 generated outputs and checks in ignored run/migration-java-trait-reference/. Clean verification after stopping Gradle matches 428 non-target class APIs, 3,635 non-target method bodies, all five other compiler closures and every output name/hash. Formatting, checkstyle, build and Forge pass: 333 JVM / 200 Forge, zero failures/errors/skips. All five packaged @Mod versions, the forced Scala-compilation guard and dev config remain correct. Sources total 213 Java files and 9 Scala files / 1,196 nonblank Scala lines. Next: assess the remaining compiler startup/model shell before selecting another extraction; retained ScalaSignature model bridges remain the Java-source limit.

2026-09-03 — compiler startup

• Added seven Forge characterization tests for the ASMMixinCompiler singleton startup, passing against untouched Scala and committed first as e9d81d6. They execute reflective definition and transformer invocation on isolated launch loaders, verify the live transformer-exception set, exercise sanity-checker byte loading and freeze loader, member-accessibility and independent mutable-map behavior.
• Moved reflection lookup/access, map construction and sanity warmup into Java CompilerBootstrap while retaining the singleton's field names, descriptors, modifiers, accessors and initialization order. The packaged inventory grows from 436 to 437 only for the helper; the shared classfile ledger covers it and no effective divergence was added.
• Saved the reference source/jar, reports, 102 generated outputs and checks in ignored run/migration-compiler-startup-reference/. Clean verification after stopping Gradle matches 431 non-target class APIs, 3,653 non-target method bodies, all five compiler closures and every output name/hash. Formatting, checkstyle, build and Forge pass: 333 JVM / 207 Forge, zero failures/errors/skips. All five packaged @Mod versions, the forced Scala-compilation guard and dev config remain correct. Sources total 214 Java files and 9 Scala files / 1,188 nonblank Scala lines.
• Audited the preserved Java-rewriter defects against current registrations and supplied consumers. The ABI inventory exposes only ProjectRed's external Scala-trait registration, which bypasses this path; current Java mixins have no wide state fields and the Forge registration suite remains green. Wide getter maxima, primitive-array analysis and malformed inherited-call casts are real but dormant for current consumers. Abstract Java mixins and Java-path side filtering remain required before the microblock traits can move, and will be separate behavior targets.

2026-09-03 — abstract Java mixins

• Added two Forge characterizations before changing behavior and committed them as 3556725. They freeze the old abstract-input rejection before parent or method inspection and prove that concrete Java mixins already preserve virtual dispatch when their base class is abstract.
• registerJavaTrait now accepts abstract inputs. Declared abstract methods remain on the generated interface so concrete methods can call them, but no static helper or MixinInfo.methods entry is emitted until a child mixin supplies the implementation. The no-argument mixin constructor may directly call a superclass constructor with arguments; registration removes that receiver/argument/call sequence while retaining subsequent state initialization. Constructor parameters and missing direct superclass calls still fail before publication.
• The feature fixture executes a two-layer generated composite over an abstract base with an int constructor. It verifies base-argument forwarding, post-super field initialization, parent metadata, abstract-contract exceptions, interface dispatch from the base and parent mixin, and final concrete instantiation. Existing Scala-trait registration and all current Java mixin outputs are unchanged.
• Saved the pre-change jar/source, reports, 106 generated outputs and checks in ignored run/migration-abstract-java-reference/. Clean verification after stopping Gradle matches all 432 class APIs, 3,643 non-target method bodies and all five compiler closures. The 106 existing dump names/hashes match exactly; the abstract-layer fixture adds six outputs. Formatting, checkstyle, build and Forge pass: 333 JVM / 210 Forge, zero failures/errors/skips. All five packaged @Mod versions, the forced Scala-compilation guard and dev config remain correct. Sources stay at 214 Java files and 9 Scala files / 1,188 nonblank Scala lines. Next: Java-path @SideOnly member filtering, characterized first as its own compiler behavior target.

2026-09-03 — Java mixin side filtering

• Expanded the Forge Java-trait fixture against the untouched implementation and committed it first as a481859. It proves that the old Java path retained runtime-visible and runtime-invisible client annotations on a dedicated server: both methods execute, both fields keep initialized state, and a client-marked constructor runs its body.
• registerJavaTrait now filters opposite-side fields and methods before building field metadata, method signatures or helper bodies. It reads both annotation tables and retains current-side members. When the no-argument constructor is absent, the helper receives an empty $init$; generated composites construct normally without executing side-specific initialization. The regressions cover a method body that would otherwise fail primitive-array analysis and input already processed by Forge's real side transformer. External Scala traits still use the unchanged ScalaSignature path.
• This deliberately changes the previously ignored Java annotation, so the divergence ledger records it. No audited Java trait depends on retaining an opposite-side member; the change supplies the remaining compiler prerequisite for a Java ProjectRed LightMicroblock, whose renderDynamic is client-only while the trait is selected both ways.
• Saved the pre-change jar/source, Forge report and 112 generated outputs under ignored run/migration-java-side-only-reference/. Clean verification after stopping Gradle keeps all 437 packaged classes, matches 432 class APIs, 3,643 non-target method bodies and all five compiler closures. All 112 reference dump names remain: 109 hashes are exact and only the SideOnly fixture's trait, helper and composite change; four outputs are new for the already-stripped-constructor fixture. Formatting, checkstyle, build and Forge pass: 333 JVM / 211 Forge, zero failures/errors/skips. All five packaged @Mod versions, the forced Scala-compilation guard and dev config remain correct. Sources stay at 214 Java files and 9 Scala files / 1,188 nonblank Scala lines. Next: microblock/MicroblockTraits.scala, characterized before conversion.

2026-09-03 — Common microblock trait implementation

• Committed seven JVM and two Forge characterization tests first as d6eb56b. A frozen Scala 2.11.5 concrete CommonMicroblockClient, compiled under Java 8 against the unchanged jar, exercises all three trait helper bridges. Tests pin initialization, signed shape/slot handling and virtual shift operands, fresh immutable partial-box lists with shared bounds, dynamic class/material lookup, render-pass gating, common cuboid face masks and particle callback evaluation order. Forge verifies generated common parts and the original NoSuchMethodError when the missing-material client icon fallback reaches server-stripped Block.getIcon; the test does not turn that existing limitation into a fix.
• Moved eight implementation methods to package-private MicroblockTraitLogic.java. Particle callbacks were already Java delegates. Retained the three Scala trait declarations, exact inheritance/signature metadata and $class bridges: Scala parent collection does not recognize Java interfaces as Scala traits, and Java registration does not incorporate implemented Scala interfaces into linearization. Both prior Java-mixin prerequisites remain useful, but are insufficient to remove this multiple-inheritance shell without another compiler behavior target.
• Saved the reference jar, source, reports and generated dumps under ignored run/migration-microblock-traits-reference/. The clean comparison preserves all 437 original class/member APIs, all 17 ScalaSignature payloads and 3,674 non-target method bodies; only the new helper raises the class inventory to 438. All 116 generated dump names/hashes are exact, including external Scala and pass-through fixtures. No new effective divergence is introduced.
• Formatting, checkstyle, build and Forge pass both normally and after stopping Gradle for a clean rebuild: 340 JVM / 213 Forge tests, zero failures/errors/skips. The forced Scala-compilation guard and all five packaged @Mod versions remain verified. Sources total 215 Java files and 9 Scala files / 1,170 nonblank Scala lines. Next: microblock/FaceMicroblockTraits.scala implementation, with characterization before conversion. GPU rendering and full client selection remain on the manual checklist.

2026-09-03 — Face microblock trait implementation

• Committed five JVM and three Forge characterization tests first as dc845bc. The frozen Scala 2.11.5 face-client consumer was compiled under Java 8 against the untouched jar. Tests verify actual emitted face indices, position, pass and bounds for all six slots and 64 masks; negative-pass bypass; material caching and repeated virtual slot evaluation between opaque draws; and null-material failure timing. Forge pins all 42 valid shape bounds, the existing signed-byte indexing failures, null entries/live replacement of the public bounds array, singleton identity and material solidity independent of the side argument.
• Moved rendering, bounds lookup and solidity to package-private FaceMicroblockTraitLogic.java. The Scala declarations, inheritance metadata, $class helpers and singleton accessor remain; Extra Utilities' runtime face-client type check and the external Scala registration path are preserved. No compiler algorithm or existing behavior was changed, and no new divergence entry is needed.
• Saved the pre-port jar/source, reports and 116 generated dumps in ignored run/migration-face-traits-reference/. Clean verification preserves all 438 original class/member APIs, all 17 ScalaSignature payloads and 3,688 non-target method bodies. All 116 generated names and SHA-256 hashes match; only the new helper increases the jar inventory to 439 classes. Formatting, checkstyle, build and Forge pass normally and after stopping Gradle for a clean rebuild: 345 JVM / 216 Forge tests, zero failures/errors/skips. The forced Scala-compilation guard and all five packaged @Mod versions remain verified. Sources total 216 Java files and 9 Scala files / 1,144 nonblank Scala lines.
• Added a manual face-cover check using Stone, Glass and ProjectRed Inverted White Lamp materials. Headless tests prove per-face dispatch, not GPU output. Next: microblock/CornerMicroblockTraits.scala implementation, characterized before conversion.

2026-09-03 — Corner microblock trait implementation

• Committed three JVM and three Forge characterization tests first as 82da452. A frozen Scala 2.11.5 corner implementor, compiled under Java 8 against the untouched jar, pins the virtual shape setter/getter and seven-slot offset, including byte truncation and out-of-range integer behavior. Forge covers all 56 supported corner bounds, singleton/type identity, signed-index failures, null/live-replaced bounds arrays and generated NBT/description round-trips for the packed shape and material name.
• Moved shape packing, bounds lookup and slot decoding to package-private CornerMicroblockTraitLogic.java. The Scala trait declaration, inheritance metadata, $class helper and singleton accessor remain. No compiler algorithm, validation or existing behavior changed; no new divergence entry is needed.
• Saved reference jar/source, reports and 116 generated dumps under ignored run/migration-corner-traits-reference/. Clean verification preserves all 439 original class/member APIs, all 17 ScalaSignature payloads and 3,692 non-target method bodies. All 116 generated names and SHA-256 hashes match; only the helper raises the inventory to 440 classes. Formatting, checkstyle, build and Forge pass normally and after stopping Gradle for a clean rebuild: 348 JVM / 219 Forge tests, zero failures/errors/skips. The forced Scala-compilation guard and all five packaged @Mod versions remain verified. Sources total 217 Java files and 9 Scala files / 1,144 nonblank Scala lines.
• Next: EdgeMicroblock in microblock/EdgeMicroblockTraits.scala; characterize and port the post traits separately. Client/GPU and full-pack validation remain on the existing manual checklist.

2026-09-03 — Edge microblock trait implementation

• Committed three JVM and three Forge characterization tests first as 5e020e5. A frozen Scala 2.11.5 implementor, compiled under Java 8 against the untouched jar, pins virtual shape access, byte truncation/integer overflow and the fifteen-slot offset. Generated tests cover all 84 edge bounds and NBT/description round-trips, singleton/type identity, inherited redstone non-conduction, signed-index failures and live/null/replaced bounds arrays.
• Moved only EdgeMicroblock shape packing, bounds lookup and slot decoding to package-private EdgeMicroblockTraitLogic.java. Retained the Scala declaration, inheritance metadata, $class bridge, singleton accessor and TEdgePart default. Both post traits in the same file are untouched. No compiler algorithm or existing behavior changed; no new divergence entry is needed.
• Saved the reference jar/source, reports and 116 generated dumps in ignored run/migration-edge-trait-reference/. Clean verification preserves all 440 original class/member APIs, all 17 ScalaSignature payloads and 3,696 non-target method bodies. All 116 generated dump names and hashes match; only the helper raises the inventory to 441 classes. Formatting, checkstyle, build and Forge pass normally and after stopping Gradle for a clean rebuild: 351 JVM / 222 Forge tests, zero failures/errors/skips. The forced Scala-compilation guard and all five packaged @Mod versions remain verified. Sources total 218 Java files and 9 Scala files / 1,144 nonblank Scala lines.
• Next: PostMicroblock in the same file; characterize its occlusion ordering, axis bounds, item identity, torch support and generated state before extraction. PostMicroblockClient follows separately. The existing manual Stone Strip / ProjectRed Red Alloy Wire and illuminated-strip checks cover the remaining client/full-pack gate.

2026-09-03 — Post microblock trait implementation

• Committed six JVM and four Forge characterization tests first as afd6c69. Frozen Scala 2.11.5 post/face implementors compiled under Java 8 against the untouched jar pin virtual calls, failure ordering and a real superclass predecessor. Tests cover post-first and aligned-face bypasses, normal/partial box rejection before super, superclass results/exceptions, fresh read-only lists and partial-list delegation. Forge covers all nine supported post bounds, signed/live/null array behavior, torch support, edge-item drops/picking, NBT/descriptions, crossing posts and aligned/non-overlapping face covers.
• Extracted seven method bodies to package-private PostMicroblockTraitLogic.java; retained Scala declarations, metadata, singleton access and the synthetic super accessor. Java returns an occlusion decision or requests the original Scala super call, preserving short-circuit ordering without exposing a new accessor or allocating a callback. The returned list still uses the same Scala Seq-to-Java conversion. PostMicroblockClient is untouched; no compiler algorithm, existing behavior or effective compatibility difference changed.
• Saved reference source/jar, reports and 116 generated dumps under ignored run/migration-post-trait-reference/. Clean verification preserves all 441 original class/member APIs, all 17 ScalaSignature payloads and 3,696 non-target method bodies. All 116 generated names/hashes match; the helper alone raises the jar inventory to 442 classes. Formatting, checkstyle, build and Forge pass normally and after stopping Gradle for a clean rebuild: 357 JVM / 226 Forge tests, zero failures/errors/skips. The forced Scala-compilation guard and all five packaged @Mod versions remain verified. Sources total 219 Java files and 9 Scala files / 1,140 nonblank Scala lines.
• Next: PostMicroblockClient; characterize render dispatch, lifecycle super ordering, shrink/split/reset behavior and size/transparency/axis tie-breaks before conversion. Client/GPU and full-pack checks remain manual.

2026-09-03 — Post microblock client implementation

• Committed eight JVM characterization tests and one Forge test first as 47885d1. Frozen Scala 2.11.5 client forwarders and lifecycle predecessors pin the exact -1 render branch, material reuse, live second-segment changes, repeated virtual size/transparency/axis reads, superclass ordering/exceptions and equality receiver dispatch (even on the same reference). Tests also pin collection foreach, neighbour order, fresh bounds copies, split reuse/reset and malformed face failures. Forge exercises real cover/post geometry across all three axes through the client helper.
• Extracted five behavior methods to PostMicroblockClientLogic.java; retained Scala state/inheritance metadata, accessors and lifecycle/super forwarders. The named Java callback preserves foreach and replaces the internal Scala anonymous callback under the existing shared classfile policy. No algorithm fix or new effective divergence was introduced. In particular, the second split segment still copies physical bounds rather than the already face-clipped first segment; the new Forge check records that reference behavior.
• Saved source/jar, reports and 116 generated dumps in ignored run/migration-post-client-reference/. Clean checks preserve all 441 retained class/member APIs, all 17 ScalaSignature payloads, 3,703 non-target method bodies and all 116 generated names/hashes. Two Java classes replace one Scala callback, bringing the jar inventory to 443 classes. Formatting, checkstyle, build and Forge pass normally and after stopping Gradle for a clean rebuild: 365 JVM / 227 Forge tests, zero failures/errors/skips. The forced Scala-compilation guard and all five packaged @Mod versions remain verified. Sources total 220 Java files and 9 Scala files / 1,104 nonblank Scala lines.
• Expanded the existing manual post check with Stone, Glass and ProjectRed Inverted White Lamp examples. The dedicated server strips the client factory entry point; helper/geometry coverage does not establish actual client generation or GPU output. Next: HollowMicroblock, followed separately by HollowMicroblockClient.