KiltMC · IcyNova4 · Feb 16, 2026
diff --git a/build.gradle.kts b/build.gradle.kts
@@ -78,6 +78,12 @@ loom {
             "MISSING_INJECTOR_DESC_SINGLETARGET" to "error"
         ))
     }
+
+    runs {
+        configureEach {
+            vmArg("--add-modules=jdk.zipfs")
+        }
+    }
 }
 
 allprojects {
@@ -690,4 +696,4 @@ fun getVersionMetadata(): String {
         System.getenv("GITHUB_SHA") ?: grgit.head().abbreviatedId
 
     return "+build.${commitHash.subSequence(0, 6)}${if (System.getenv("GITHUB_RUN_NUMBER") == null) "-local" else if (!isRelease()) "-nightly" else ""}"
-}
+}
diff --git a/src/main/java/xyz/bluspring/kilt/mixin/compat/fabric_api/ModNioResourcePackMixin.java b/src/main/java/xyz/bluspring/kilt/mixin/compat/fabric_api/ModNioResourcePackMixin.java
@@ -0,0 +1,24 @@
+package xyz.bluspring.kilt.mixin.compat.fabric_api;
+
+import net.fabricmc.fabric.impl.resource.loader.ModNioResourcePack;
+import net.fabricmc.loader.api.ModContainer;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Redirect;
+
+import java.nio.file.Path;
+import java.nio.file.ProviderNotFoundException;
+import java.util.Collections;
+import java.util.List;
+
+@Mixin(value = ModNioResourcePack.class, remap = false)
+public class ModNioResourcePackMixin {
+    @Redirect(method = "create", at = @At(value = "INVOKE", target = "Lnet/fabricmc/loader/api/ModContainer;getRootPaths()Ljava/util/List;"))
+    private static List<Path> kilt$skipMissingJarFileSystems(ModContainer instance) {
+        try {
+            return instance.getRootPaths();
+        } catch (ProviderNotFoundException exception) {
+            return Collections.emptyList();
+        }
+    }
+}
diff --git a/src/main/java/xyz/bluspring/kilt/mixin/compat/fabric_api/ServerLanguageUtilMixin.java b/src/main/java/xyz/bluspring/kilt/mixin/compat/fabric_api/ServerLanguageUtilMixin.java
@@ -0,0 +1,24 @@
+package xyz.bluspring.kilt.mixin.compat.fabric_api;
+
+import net.fabricmc.fabric.impl.resource.loader.ServerLanguageUtil;
+import net.fabricmc.loader.api.ModContainer;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Redirect;
+
+import java.nio.file.Path;
+import java.nio.file.ProviderNotFoundException;
+import java.util.Collections;
+import java.util.List;
+
+@Mixin(value = ServerLanguageUtil.class, remap = false)
+public class ServerLanguageUtilMixin {
+    @Redirect(method = "getModLanguageFiles", at = @At(value = "INVOKE", target = "Lnet/fabricmc/loader/api/ModContainer;getRootPaths()Ljava/util/List;"))
+    private static List<Path> kilt$skipMissingJarFileSystems(ModContainer instance) {
+        try {
+            return instance.getRootPaths();
+        } catch (ProviderNotFoundException exception) {
+            return Collections.emptyList();
+        }
+    }
+}
diff --git a/src/main/kotlin/xyz/bluspring/kilt/loader/KiltLoader.kt b/src/main/kotlin/xyz/bluspring/kilt/loader/KiltLoader.kt
@@ -420,7 +420,7 @@ class KiltLoader : KnitModLoader<ForgeMod>(Kilt.MOD_ID, "Forge") {
                 if (url.file.contains(".jar") && url.file.contains("!/META-INF/mods.toml")) // Prevent Fabric mods with broken Forge metadata from loading in the dev env
                     continue
 
-                val path = Path(url.path.removePrefix("file:/"))
+                val path = url.toURI().toPath()
 
                 val toml = tomlParser.parse(url)
                 modsList.addAll(parseModsToml(path, toml, null, isBuiltIn = true))
@@ -524,6 +524,7 @@ class KiltLoader : KnitModLoader<ForgeMod>(Kilt.MOD_ID, "Forge") {
             launch(Dispatchers.Default) {
                 // Load Forge scan data immediately, then we can assign it when we need to.
                 val forgeScanData = ModFileScanData()
+                val forgeScanDataLock = Any()
 
                 KiltHelper.getForgeClassNodes().asFlow().collect {
                     val visitor = ModClassVisitor()
@@ -543,7 +544,9 @@ class KiltLoader : KnitModLoader<ForgeMod>(Kilt.MOD_ID, "Forge") {
                         if (mod.modFile == null) { // This is usually a Forge built-in, we don't have to worry about scanning this.
                             // If it is in fact a built-in, let's assign the scan data.
                             if (mod.definition.isBuiltin) {
-                                forgeScanData.addModFileInfo(ModFileInfo(mod))
+                                synchronized(forgeScanDataLock) {
+                                    forgeScanData.addModFileInfo(ModFileInfo(mod))
+                                }
                                 mod.scanData = forgeScanData
                             }
 
@@ -670,6 +673,13 @@ class KiltLoader : KnitModLoader<ForgeMod>(Kilt.MOD_ID, "Forge") {
 
                     Kilt.logger.debug("Automatically registered event ${annotation.clazz.className} from mod ID $modId under bus ${busType.name}")
                 } catch (e: Throwable) {
+                    ModLoadingContext.kiltActiveModId = null
+
+                    if (isEnvironmentClassLoadingIssue(e)) {
+                        Kilt.logger.debug("Skipping automatic event registration for ${annotation.clazz.className} due to environment mismatch.")
+                        return@collect
+                    }
+
                     Kilt.logger.error("Failed to register event ${annotation.clazz.className} from mod ${mod.modId}!")
                     val ex = RuntimeException("Failed to register event ${annotation.clazz.className} from mod ${mod.modId}!", e)
                     ex.printStackTrace()
@@ -785,6 +795,15 @@ class KiltLoader : KnitModLoader<ForgeMod>(Kilt.MOD_ID, "Forge") {
 
                     ModLoadingContext.kiltActiveModId = null
                 } catch (e: Throwable) {
+                    ModLoadingContext.kiltActiveModId = null
+
+                    val envMismatch = isEnvironmentClassLoadingIssue(e) || isEnvironmentClassLoadingIssue(extraThrowable)
+                    if (envMismatch) {
+                        Kilt.logger.debug("Skipping mod class ${it.clazz.className} for ${mod.modId} due to environment mismatch.")
+                        hasErrored = true
+                        return@collect
+                    }
+
                     e.printStackTrace()
                     if (extraThrowable != null)
                         exception.addSuppressed(extraThrowable)
@@ -802,6 +821,23 @@ class KiltLoader : KnitModLoader<ForgeMod>(Kilt.MOD_ID, "Forge") {
         }
     }
 
+    private fun isEnvironmentClassLoadingIssue(throwable: Throwable?): Boolean {
+        var current = throwable
+        while (current != null) {
+            val message = current.message
+            if (message != null &&
+                message.startsWith("Cannot load class ") &&
+                (message.contains("in environment type SERVER") || message.contains("in environment type CLIENT"))
+            ) {
+                return true
+            }
+
+            current = current.cause
+        }
+
+        return false
+    }
+
     private fun loadTransformers(mod: ForgeMod) {
         if (mod.modFile == null || mod.definition.isBuiltin) {
             val accessTransformer = KiltLoader::class.java.getResource("META-INF/accesstransformer.cfg")
@@ -935,4 +971,4 @@ class KiltLoader : KnitModLoader<ForgeMod>(Kilt.MOD_ID, "Forge") {
             runCatching { this.createDirectories() }
         }
     }
-}
+}
diff --git a/src/main/kotlin/xyz/bluspring/kilt/loader/remap/KiltRemapper.kt b/src/main/kotlin/xyz/bluspring/kilt/loader/remap/KiltRemapper.kt
@@ -46,7 +46,10 @@ import xyz.bluspring.kilt.util.KiltHelper
 import xyz.bluspring.knit.loader.mod.ModDefinition
 import xyz.bluspring.knit.loader.util.*
 import java.io.File
+import java.net.URI
 import java.nio.file.Path
+import java.nio.file.Paths
+import java.nio.file.ProviderNotFoundException
 import java.nio.file.StandardOpenOption
 import java.util.*
 import java.util.function.Consumer
@@ -90,6 +93,57 @@ object KiltRemapper {
     else
         FabricLoader.getInstance().mappingResolver
 
+    private fun ClassProvider.Builder.addLibrarySafe(path: Path) {
+        val isDirectory = runCatching { path.isDirectory() }.getOrDefault(false)
+        if (!isDirectory) {
+            val isRegularFile = runCatching { path.isRegularFile() }.getOrDefault(false)
+            if (!isRegularFile) {
+                return
+            }
+
+            val name = path.fileName?.toString()?.lowercase(Locale.ROOT)
+            val isArchive = name?.endsWith(".jar") == true || name?.endsWith(".zip") == true || name?.endsWith(".jmod") == true
+            if (!isArchive) {
+                return
+            }
+        }
+
+        try {
+            addLibrary(path)
+            return
+        } catch (_: ProviderNotFoundException) {
+            // Some classpath entries are backed by non-default file systems in dev runs.
+            // Normalize them to a physical path that AutoRenamingTool can open.
+        }
+
+        val fallbackPath = runCatching {
+            val uri = path.toUri()
+            when (uri.scheme) {
+                "jar" -> {
+                    val nested = uri.toString().removePrefix("jar:").substringBefore("!/")
+                    Paths.get(URI(nested))
+                }
+                "file" -> Paths.get(uri)
+                else -> null
+            }
+        }.getOrNull()
+
+        if (fallbackPath != null) {
+            try {
+                addLibrary(fallbackPath)
+                return
+            } catch (exception: ProviderNotFoundException) {
+                throw RuntimeException(
+                    "Failed to add class library path '$path' (uri=${runCatching { path.toUri() }.getOrNull()}) " +
+                            "using fallback '$fallbackPath' (uri=${runCatching { fallbackPath.toUri() }.getOrNull()})",
+                    exception
+                )
+            }
+        }
+
+        throw RuntimeException("Could not normalize class library path '$path' (uri=${runCatching { path.toUri() }.getOrNull()}).")
+    }
+
     // This is created automatically using https://github.com/BluSpring/srg2intermediary
     // srg -> intermediary
     val srgIntermediaryMapping: IMappingFile = this::class.java.getResourceAsStream("/srg_intermediary.tiny")!!.buffered().use { IMappingFile.load(it) }
@@ -284,7 +338,7 @@ object KiltRemapper {
                 // in order to use mods lmao
                 *modLoadingQueue.map { mod -> mod.path }.toTypedArray()
             ).forEach {
-                addLibrary(it)
+                addLibrarySafe(it)
             }
         }.build()
 
@@ -298,7 +352,7 @@ object KiltRemapper {
             ClassProvider.builder().apply {
                 // time to add Intermediary mappings to the mix! :,D
                 if (FabricLoader.getInstance().isDevelopmentEnvironment && !forceProductionRemap) {
-                    addLibrary(intermediaryMap)
+                    intermediaryMap?.let { addLibrarySafe(it) }
                 }
 
                 // IMPORTANT: this cannot be a flow or use merge, otherwise the order isn't retained. srgGamePath MUST be at the top of the list.
@@ -314,7 +368,7 @@ object KiltRemapper {
                     // in order to use mods lmao
                     *modLoadingQueue.map { mod -> mod.path }.toTypedArray()
                 ).forEach {
-                    addLibrary(it)
+                    addLibrarySafe(it)
                 }
             }.build()
         }
@@ -717,9 +771,9 @@ object KiltRemapper {
         val startTime = System.currentTimeMillis()
 
         val classProvider = ClassProvider.builder().apply {
-            this.addLibrary(gameFile)
+            this.addLibrarySafe(gameFile)
             for (path in getGameClassPath()) {
-                this.addLibrary(path)
+                this.addLibrarySafe(path)
             }
         }.build()
         val srgRemapper = EnhancedRemapper(classProvider, mappingFile, logConsumer)

diff --git a/src/main/resources/Kilt.mixins.json b/src/main/resources/Kilt.mixins.json
@@ -67,7 +67,9 @@
         "compat.fabric_api.BlockInitTrackerMixin",
         "compat.fabric_api.FabricItemMixin",
         "compat.fabric_api.Int2ObjectMapTrackerMixin",
+        "compat.fabric_api.ModNioResourcePackMixin",
         "compat.fabric_api.PackRepositoryMixin",
+        "compat.fabric_api.ServerLanguageUtilMixin",
         "compat.forge.alexscaves.PotionUtilsMixin",
         "compat.forge.blueprint.RemoldedResourceManagerMixin",
         "compat.forge.decocraft.JsonParserMixin",