diff --git a/core/src/main/java/org/spongepowered/configurate/ConfigValue.java b/core/src/main/java/org/spongepowered/configurate/ConfigValue.java
index 2cd9835ad..36f5aa9fa 100644
--- a/core/src/main/java/org/spongepowered/configurate/ConfigValue.java
+++ b/core/src/main/java/org/spongepowered/configurate/ConfigValue.java
@@ -20,6 +20,8 @@
 
 /**
  * The value in a {@link ConfigurationNode}.
+ *
+ * @since 4.0.0
  */
 interface ConfigValue<N extends ScopedConfigurationNode<N>, A extends AbstractConfigurationNode<N, A>> {
 
diff --git a/core/src/main/java/org/spongepowered/configurate/ListConfigValue.java b/core/src/main/java/org/spongepowered/configurate/ListConfigValue.java
index b42004186..c46457fe8 100644
--- a/core/src/main/java/org/spongepowered/configurate/ListConfigValue.java
+++ b/core/src/main/java/org/spongepowered/configurate/ListConfigValue.java
@@ -124,7 +124,7 @@ public void set(@Nullable Object value) {
         if (!(value instanceof Collection)) {
             value = Collections.singleton(value);
         }
-        final Collection<@Nullable ?> valueAsList = (Collection<@Nullable ?>) value;
+        final Collection<? extends @Nullable Object> valueAsList = (Collection<? extends @Nullable Object>) value;
         final List<A> newValue = new ArrayList<>(valueAsList.size());
 
         int count = 0;
diff --git a/core/src/main/java/org/spongepowered/configurate/loader/AbstractConfigurationFormat.java b/core/src/main/java/org/spongepowered/configurate/loader/AbstractConfigurationFormat.java
index d8eaf5da5..fc67226d2 100644
--- a/core/src/main/java/org/spongepowered/configurate/loader/AbstractConfigurationFormat.java
+++ b/core/src/main/java/org/spongepowered/configurate/loader/AbstractConfigurationFormat.java
@@ -79,14 +79,14 @@ public Set<String> supportedExtensions() {
     }
 
     @Override
-    public ConfigurationLoader<@NonNull ?> create(final Path file) {
+    public ConfigurationLoader<? extends @NonNull Object> create(final Path file) {
         return this.builderMaker.get()
             .path(file)
             .build();
     }
 
     @Override
-    public ConfigurationLoader<@NonNull ?> create(final Path file, final ConfigurationNode options) {
+    public ConfigurationLoader<? extends @NonNull Object> create(final Path file, final ConfigurationNode options) {
         return this.builderMaker.get()
             .from(LoaderOptionSource.node(options))
             .path(file)
@@ -94,14 +94,14 @@ public Set<String> supportedExtensions() {
     }
 
     @Override
-    public ConfigurationLoader<@NonNull ?> create(final URL url) {
+    public ConfigurationLoader<? extends @NonNull Object> create(final URL url) {
         return this.builderMaker.get()
             .url(url)
             .build();
     }
 
     @Override
-    public ConfigurationLoader<@NonNull ?> create(final URL url, final ConfigurationNode options) {
+    public ConfigurationLoader<? extends @NonNull Object> create(final URL url, final ConfigurationNode options) {
         return this.builderMaker.get()
             .from(LoaderOptionSource.node(options))
             .url(url)
diff --git a/core/src/main/java/org/spongepowered/configurate/loader/ConfigurationFormat.java b/core/src/main/java/org/spongepowered/configurate/loader/ConfigurationFormat.java
index bef1c10af..b86b59d1f 100644
--- a/core/src/main/java/org/spongepowered/configurate/loader/ConfigurationFormat.java
+++ b/core/src/main/java/org/spongepowered/configurate/loader/ConfigurationFormat.java
@@ -93,7 +93,7 @@ static Set<ConfigurationFormat> supportedFormats() {
      * @return a newly configured loader
      * @since 4.2.0
      */
-    default ConfigurationLoader<@NonNull ?> create(Path file) {
+    default ConfigurationLoader<? extends @NonNull Object> create(Path file) {
         return create(file, BasicConfigurationNode.factory().createNode());
     }
 
@@ -105,7 +105,7 @@ static Set<ConfigurationFormat> supportedFormats() {
      * @return a newly configured loader
      * @since 4.2.0
      */
-    ConfigurationLoader<@NonNull ?> create(Path file, ConfigurationNode options);
+    ConfigurationLoader<? extends @NonNull Object> create(Path file, ConfigurationNode options);
 
     /**
      * Create a new loader configured to load from the provided URL,
@@ -117,7 +117,7 @@ static Set<ConfigurationFormat> supportedFormats() {
      * @return a newly configured loader
      * @since 4.2.0
      */
-    default ConfigurationLoader<@NonNull ?> create(URL url) {
+    default ConfigurationLoader<? extends @NonNull Object> create(URL url) {
         return create(url, BasicConfigurationNode.factory().createNode());
     }
 
@@ -131,6 +131,6 @@ static Set<ConfigurationFormat> supportedFormats() {
      * @return a newly configured loader
      * @since 4.2.0
      */
-    ConfigurationLoader<@NonNull?> create(URL url, ConfigurationNode options);
+    ConfigurationLoader<? extends @NonNull Object> create(URL url, ConfigurationNode options);
 
 }
diff --git a/core/src/main/java/org/spongepowered/configurate/reactive/TransactionalRegistration.java b/core/src/main/java/org/spongepowered/configurate/reactive/TransactionalRegistration.java
index f445a6d94..bc08d8f1d 100644
--- a/core/src/main/java/org/spongepowered/configurate/reactive/TransactionalRegistration.java
+++ b/core/src/main/java/org/spongepowered/configurate/reactive/TransactionalRegistration.java
@@ -24,6 +24,7 @@
  * A registration that is transaction-aware.
  *
  * @param <V> value type
+ * @since 4.0.0
  */
 interface TransactionalRegistration<V> extends AbstractProcessor.Registration<V> {
 
diff --git a/core/src/main/java/org/spongepowered/configurate/reference/ValueReferenceImpl.java b/core/src/main/java/org/spongepowered/configurate/reference/ValueReferenceImpl.java
index f644b79c7..c1543900a 100644
--- a/core/src/main/java/org/spongepowered/configurate/reference/ValueReferenceImpl.java
+++ b/core/src/main/java/org/spongepowered/configurate/reference/ValueReferenceImpl.java
@@ -33,7 +33,7 @@
 import java.util.concurrent.Executor;
 import java.util.function.Function;
 
-class ValueReferenceImpl<@Nullable T, N extends ScopedConfigurationNode<N>> implements ValueReference<T, N>, Publisher<T> {
+class ValueReferenceImpl<T extends @Nullable Object, N extends ScopedConfigurationNode<N>> implements ValueReference<T, N>, Publisher<T> {
 
     // Information about the reference
     private final ManualConfigurationReference<N> root;
diff --git a/core/src/main/java/org/spongepowered/configurate/serialize/OptionalSerializer.java b/core/src/main/java/org/spongepowered/configurate/serialize/OptionalSerializer.java
index 4d2fd8feb..91ea4909b 100644
--- a/core/src/main/java/org/spongepowered/configurate/serialize/OptionalSerializer.java
+++ b/core/src/main/java/org/spongepowered/configurate/serialize/OptionalSerializer.java
@@ -55,6 +55,7 @@ public Optional<?> deserialize(final AnnotatedType type, final ConfigurationNode
     }
 
     @Override
+    @SuppressWarnings("NullableOptional") // needed for type signature
     public void serialize(final AnnotatedType type, final @Nullable Optional<?> obj, final ConfigurationNode node) throws SerializationException {
         if (obj == null || !obj.isPresent()) {
             node.set(null);
diff --git a/core/src/main/java/org/spongepowered/configurate/serialize/TypeSerializerCollection.java b/core/src/main/java/org/spongepowered/configurate/serialize/TypeSerializerCollection.java
index 874dffd29..bb1bd78bb 100644
--- a/core/src/main/java/org/spongepowered/configurate/serialize/TypeSerializerCollection.java
+++ b/core/src/main/java/org/spongepowered/configurate/serialize/TypeSerializerCollection.java
@@ -501,6 +501,11 @@ public TypeSerializerCollection build() {
         }
     }
 
+    /**
+     * A serializer registration.
+     *
+     * @since 4.2.0
+     */
     interface RegisteredSerializer {
 
         boolean matches(Type test);
diff --git a/format/jackson/src/main/java/org/spongepowered/configurate/jackson/JacksonVisitor.java b/format/jackson/src/main/java/org/spongepowered/configurate/jackson/JacksonVisitor.java
index 7f2494fdd..d2787fe0d 100644
--- a/format/jackson/src/main/java/org/spongepowered/configurate/jackson/JacksonVisitor.java
+++ b/format/jackson/src/main/java/org/spongepowered/configurate/jackson/JacksonVisitor.java
@@ -24,6 +24,7 @@
 
 import java.io.IOException;
 
+@SuppressWarnings("AlmostJavadoc")
 final class JacksonVisitor implements ConfigurationVisitor<JsonGenerator, Void, ConfigurateException> {
 
     static final ThreadLocal<JacksonVisitor> INSTANCE = ThreadLocal.withInitial(JacksonVisitor::new);
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index ddac8f13c..a4492c984 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -2,7 +2,7 @@
 assertj="3.25.1"
 autoValue="1.10.4"
 checkerQual="3.42.0"
-checkstyle="10.12.5"
+checkstyle="10.12.7"
 geantyref = "1.3.14"
 errorprone="2.24.1"
 indra = "3.1.3"
@@ -10,7 +10,7 @@ junit="5.10.1"
 ktlint="0.49.1"
 ktfmt="0.46"
 pmd = "6.55.0"
-spotless = "6.23.2"
+spotless = "6.23.3"
 
 [libraries]
 # Shared
@@ -47,7 +47,7 @@ guice-runtime = "com.google.inject:guice:5.0.1"
 
 # Formats
 gson = "com.google.code.gson:gson:2.8.0" # Fixed version, to avoid using API not present in older MC
-jackson = "com.fasterxml.jackson.core:jackson-core:2.16.0"
+jackson = "com.fasterxml.jackson.core:jackson-core:2.16.1"
 
 # Tool
 clikt = "com.github.ajalt:clikt:2.8.0"
@@ -55,7 +55,7 @@ jansi = "org.fusesource.jansi:jansi:2.4.1"
 
 # Build
 build-codenarc = { module = "org.codenarc:CodeNarc", version = "3.3.0-groovy-4.0" }
-build-codenarcGroovy = { module = "org.apache.groovy:groovy-all", version = "4.0.16" }
+build-codenarcGroovy = { module = "org.apache.groovy:groovy-all", version = "4.0.17" }
 build-errorprone = "net.ltgt.gradle:gradle-errorprone-plugin:3.1.0"
 build-forbiddenApis = "de.thetaphi:forbiddenapis:3.6"
 build-goomph = "com.diffplug.gradle:goomph:3.44.0"