diff --git a/build.gradle b/build.gradle
index 6b50fc0d6..7c0b03a21 100644
--- a/build.gradle
+++ b/build.gradle
@@ -38,6 +38,14 @@ allprojects {
             url = 'https://libraries.minecraft.net'
         }
 
+        maven {
+            url "https://repo.spongepowered.org/repository/maven-public/"
+            name "SpongePowered maven"
+            content {
+                includeGroup "org.spongepowered"
+            }
+        }
+
         // TODO remove
         mavenLocal()
     }
diff --git a/gradle.properties b/gradle.properties
index f2e784977..4873e3690 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -6,7 +6,7 @@ modlauncher_version=10.0.9
 securejarhandler_version=2.1.23
 bootstraplauncher_version=1.1.2
 asm_version=9.5
-mixin_version=0.8.5
+mixin_version=0.8.6-SNAPSHOT
 terminalconsoleappender_version=1.2.0
 nightconfig_version=3.6.4
 jetbrains_annotations_version=24.0.1
diff --git a/loader/src/main/java/net/neoforged/fml/loading/FMLLoader.java b/loader/src/main/java/net/neoforged/fml/loading/FMLLoader.java
index a1efb7d2e..3e9cbc7a1 100644
--- a/loader/src/main/java/net/neoforged/fml/loading/FMLLoader.java
+++ b/loader/src/main/java/net/neoforged/fml/loading/FMLLoader.java
@@ -164,7 +164,7 @@ public static List<ITransformationService.Resource> completeScan(IModuleLayerMan
         loadingModList = backgroundScanHandler.getLoadingModList();
         if (loadingModList.getErrors().isEmpty()) {
             // Add extra mixin configs
-            extraMixinConfigs.forEach(DeferredMixinConfigRegistration::addMixinConfig);
+            extraMixinConfigs.forEach(DeferredMixinConfigRegistration::addCommandLineMixinConfig);
         }
         return List.of(modValidator.getModResources());
     }
diff --git a/loader/src/main/java/net/neoforged/fml/loading/LoadingModList.java b/loader/src/main/java/net/neoforged/fml/loading/LoadingModList.java
index b790639c5..2021b3101 100644
--- a/loader/src/main/java/net/neoforged/fml/loading/LoadingModList.java
+++ b/loader/src/main/java/net/neoforged/fml/loading/LoadingModList.java
@@ -80,11 +80,11 @@ public void addCoreMods()
     }
 
     public void addMixinConfigs() {
-        modFiles.stream()
-                .map(ModFileInfo::getFile)
-                .map(ModFile::getMixinConfigs)
-                .flatMap(List::stream)
-                .forEach(DeferredMixinConfigRegistration::addMixinConfig);
+        for (var fileInfo : modFiles) {
+            for (var config : fileInfo.getFile().getMixinConfigs()) {
+                DeferredMixinConfigRegistration.addModMixinConfig(config, fileInfo.getFile());
+            }
+        }
     }
 
     public void addAccessTransformers()
diff --git a/loader/src/main/java/net/neoforged/fml/loading/mixin/DeferredMixinConfigRegistration.java b/loader/src/main/java/net/neoforged/fml/loading/mixin/DeferredMixinConfigRegistration.java
index ef821f703..55cc76dd1 100644
--- a/loader/src/main/java/net/neoforged/fml/loading/mixin/DeferredMixinConfigRegistration.java
+++ b/loader/src/main/java/net/neoforged/fml/loading/mixin/DeferredMixinConfigRegistration.java
@@ -5,16 +5,18 @@
 
 package net.neoforged.fml.loading.mixin;
 
+import net.neoforged.neoforgespi.locating.IModFile;
 import org.spongepowered.asm.launch.GlobalProperties;
 import org.spongepowered.asm.launch.MixinBootstrap;
 import org.spongepowered.asm.mixin.Mixins;
+import org.spongepowered.asm.mixin.extensibility.IMixinConfigSource;
 
 import java.util.ArrayList;
 import java.util.List;
 
 public class DeferredMixinConfigRegistration {
     private static boolean added = false;
-    private static final List<String> mixinConfigs = new ArrayList<>();
+    private static final List<MixinToAdd> mixinConfigs = new ArrayList<>();
 
     static {
         // Register our platform agent first
@@ -24,17 +26,38 @@ public class DeferredMixinConfigRegistration {
         MixinBootstrap.getPlatform().addContainer(new FMLMixinContainerHandle());
     }
 
-    public static void addMixinConfig(String config) {
+    private record MixinToAdd(String config, IMixinConfigSource source) {}
+
+    public static void addCommandLineMixinConfig(String config) {
+        addMixinConfig(config, new MixinConfigSource(config, "Mixin config passed via --fml.mixinConfig " + config));
+    }
+
+    public static void addModMixinConfig(String config, IModFile file) {
+        String sourceId;
+        if (file.getModInfos().size() == 1) {
+            // Single mod, use the modid
+            sourceId = file.getModInfos().get(0).getModId();
+        } else {
+            // Else use file name...
+            sourceId = file.getFileName();
+        }
+
+        addMixinConfig(config, new MixinConfigSource(sourceId, "Mixin config loaded from mod file " + file.getFilePath()));
+    }
+
+    private static void addMixinConfig(String config, IMixinConfigSource source) {
         if (added) {
             throw new IllegalStateException("Too late to add mixin configs!");
         }
 
-        mixinConfigs.add(config);
+        mixinConfigs.add(new MixinToAdd(config, source));
     }
 
     static void registerConfigs() {
         added = true;
-        mixinConfigs.forEach(Mixins::addConfiguration);
+        mixinConfigs.forEach(c -> {
+            Mixins.addConfiguration(c.config(), c.source());
+        });
         mixinConfigs.clear();
     }
 }
diff --git a/loader/src/main/java/net/neoforged/fml/loading/mixin/FMLMixinContainerHandle.java b/loader/src/main/java/net/neoforged/fml/loading/mixin/FMLMixinContainerHandle.java
index b0f0a5ab5..e87074671 100644
--- a/loader/src/main/java/net/neoforged/fml/loading/mixin/FMLMixinContainerHandle.java
+++ b/loader/src/main/java/net/neoforged/fml/loading/mixin/FMLMixinContainerHandle.java
@@ -15,6 +15,16 @@
  * No attribute because we directly load the mixin configs in {@link FMLMixinPlatformAgent}.
  */
 public class FMLMixinContainerHandle implements IContainerHandle {
+    @Override
+    public String getId() {
+        return "fml";
+    }
+
+    @Override
+    public String getDescription() {
+        return "FMLMixinContainerHandle, a dummy source used by FML to inject mixin configs from mods at the right time.";
+    }
+
     @Override
     public String getAttribute(String name) {
         return null;
diff --git a/loader/src/main/java/net/neoforged/fml/loading/mixin/MixinConfigSource.java b/loader/src/main/java/net/neoforged/fml/loading/mixin/MixinConfigSource.java
new file mode 100644
index 000000000..09b48556a
--- /dev/null
+++ b/loader/src/main/java/net/neoforged/fml/loading/mixin/MixinConfigSource.java
@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) NeoForged and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
+package net.neoforged.fml.loading.mixin;
+
+import org.spongepowered.asm.mixin.extensibility.IMixinConfigSource;
+
+record MixinConfigSource(String id, String description) implements IMixinConfigSource {
+    @Override
+    public String getId() {
+        return id;
+    }
+
+    @Override
+    public String getDescription() {
+        return description;
+    }
+}