diff --git a/CHANGELOG.md b/CHANGELOG.md
index 46bed68f00..10502c5f18 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -33,6 +33,8 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 - Run model tests against both JSON mappers instead of picking one at random ([#2085](https://github.com/opensearch-project/opensearch-java/pull/2085))
 - Fix currentSize calculation in BulkIngester ([#2113](https://github.com/opensearch-project/opensearch-java/pull/2113))
 - Use protocol version from response (rather than request) ([#2118](https://github.com/opensearch-project/opensearch-java/pull/2118))
+- Fix `ShardFailure` serializing/deserializing `index`/`node`/`shard` instead of the server's `_index`/`_node`/`_shard` keys, causing `MissingRequiredPropertyException` and silently dropped fields ([#2037](https://github.com/opensearch-project/opensearch-java/pull/2037))
+- Fix `PathHierarchyTokenizer` optional fields incorrectly marked required causing deserialization failure ([#2038](https://github.com/opensearch-project/opensearch-java/pull/2038))
 
 ### Changed
 - Updated API spec download URL to `https://api-spec.opensearch.org` ([#2116](https://github.com/opensearch-project/opensearch-java/pull/2116))
diff --git a/java-client/src/generated/java/org/opensearch/client/opensearch/_types/DerivedField.java b/java-client/src/generated/java/org/opensearch/client/opensearch/_types/DerivedField.java
index eb2e081559..41602d50a2 100644
--- a/java-client/src/generated/java/org/opensearch/client/opensearch/_types/DerivedField.java
+++ b/java-client/src/generated/java/org/opensearch/client/opensearch/_types/DerivedField.java
@@ -68,9 +68,6 @@ public class DerivedField implements PlainJsonSerializable, ToCopyableBuilder<De
     @Nullable
     private final Boolean ignoreMalformed;
 
-    @Nonnull
-    private final String name;
-
     @Nullable
     private final String prefilterField;
 
@@ -88,7 +85,6 @@ public class DerivedField implements PlainJsonSerializable, ToCopyableBuilder<De
     private DerivedField(Builder builder) {
         this.format = builder.format;
         this.ignoreMalformed = builder.ignoreMalformed;
-        this.name = ApiTypeHelper.requireNonNull(builder.name, this, "name");
         this.prefilterField = builder.prefilterField;
         this.properties = ApiTypeHelper.unmodifiable(builder.properties);
         this.script = ApiTypeHelper.requireNonNull(builder.script, this, "script");
@@ -115,14 +111,6 @@ public final Boolean ignoreMalformed() {
         return this.ignoreMalformed;
     }
 
-    /**
-     * Required - API name: {@code name}
-     */
-    @Nonnull
-    public final String name() {
-        return this.name;
-    }
-
     /**
      * API name: {@code prefilter_field}
      */
@@ -176,9 +164,6 @@ protected void serializeInternal(JsonGenerator generator, JsonpMapper mapper) {
             generator.write(this.ignoreMalformed);
         }
 
-        generator.writeKey("name");
-        generator.write(this.name);
-
         if (this.prefilterField != null) {
             generator.writeKey("prefilter_field");
             generator.write(this.prefilterField);
@@ -222,7 +207,6 @@ public static class Builder extends ObjectBuilderBase implements CopyableBuilder
         private String format;
         @Nullable
         private Boolean ignoreMalformed;
-        private String name;
         @Nullable
         private String prefilterField;
         @Nullable
@@ -235,7 +219,6 @@ public Builder() {}
         private Builder(DerivedField o) {
             this.format = o.format;
             this.ignoreMalformed = o.ignoreMalformed;
-            this.name = o.name;
             this.prefilterField = o.prefilterField;
             this.properties = _mapCopy(o.properties);
             this.script = o.script;
@@ -245,7 +228,6 @@ private Builder(DerivedField o) {
         private Builder(Builder o) {
             this.format = o.format;
             this.ignoreMalformed = o.ignoreMalformed;
-            this.name = o.name;
             this.prefilterField = o.prefilterField;
             this.properties = _mapCopy(o.properties);
             this.script = o.script;
@@ -276,15 +258,6 @@ public final Builder ignoreMalformed(@Nullable Boolean value) {
             return this;
         }
 
-        /**
-         * Required - API name: {@code name}
-         */
-        @Nonnull
-        public final Builder name(String value) {
-            this.name = value;
-            return this;
-        }
-
         /**
          * API name: {@code prefilter_field}
          */
@@ -373,7 +346,6 @@ public DerivedField build() {
     protected static void setupDerivedFieldDeserializer(ObjectDeserializer<DerivedField.Builder> op) {
         op.add(Builder::format, JsonpDeserializer.stringDeserializer(), "format");
         op.add(Builder::ignoreMalformed, JsonpDeserializer.booleanDeserializer(), "ignore_malformed");
-        op.add(Builder::name, JsonpDeserializer.stringDeserializer(), "name");
         op.add(Builder::prefilterField, JsonpDeserializer.stringDeserializer(), "prefilter_field");
         op.add(Builder::properties, JsonpDeserializer.stringMapDeserializer(JsonData._DESERIALIZER), "properties");
         op.add(Builder::script, Script._DESERIALIZER, "script");
@@ -385,7 +357,6 @@ public int hashCode() {
         int result = 17;
         result = 31 * result + Objects.hashCode(this.format);
         result = 31 * result + Objects.hashCode(this.ignoreMalformed);
-        result = 31 * result + this.name.hashCode();
         result = 31 * result + Objects.hashCode(this.prefilterField);
         result = 31 * result + Objects.hashCode(this.properties);
         result = 31 * result + this.script.hashCode();
@@ -400,7 +371,6 @@ public boolean equals(Object o) {
         DerivedField other = (DerivedField) o;
         return Objects.equals(this.format, other.format)
             && Objects.equals(this.ignoreMalformed, other.ignoreMalformed)
-            && this.name.equals(other.name)
             && Objects.equals(this.prefilterField, other.prefilterField)
             && Objects.equals(this.properties, other.properties)
             && this.script.equals(other.script)
diff --git a/java-client/src/generated/java/org/opensearch/client/opensearch/_types/ShardFailure.java b/java-client/src/generated/java/org/opensearch/client/opensearch/_types/ShardFailure.java
index c46b364053..cfd6855b87 100644
--- a/java-client/src/generated/java/org/opensearch/client/opensearch/_types/ShardFailure.java
+++ b/java-client/src/generated/java/org/opensearch/client/opensearch/_types/ShardFailure.java
@@ -92,7 +92,7 @@ public static ShardFailure of(Function<ShardFailure.Builder, ObjectBuilder<Shard
     }
 
     /**
-     * API name: {@code index}
+     * API name: {@code _index}
      */
     @Nullable
     public final String index() {
@@ -100,7 +100,7 @@ public final String index() {
     }
 
     /**
-     * API name: {@code node}
+     * API name: {@code _node}
      */
     @Nullable
     public final String node() {
@@ -123,7 +123,7 @@ public final ErrorCause reason() {
     }
 
     /**
-     * Required - API name: {@code shard}
+     * Required - API name: {@code _shard}
      */
     public final int shard() {
         return this.shard;
@@ -149,12 +149,12 @@ public void serialize(JsonGenerator generator, JsonpMapper mapper) {
 
     protected void serializeInternal(JsonGenerator generator, JsonpMapper mapper) {
         if (this.index != null) {
-            generator.writeKey("index");
+            generator.writeKey("_index");
             generator.write(this.index);
         }
 
         if (this.node != null) {
-            generator.writeKey("node");
+            generator.writeKey("_node");
             generator.write(this.node);
         }
 
@@ -164,7 +164,7 @@ protected void serializeInternal(JsonGenerator generator, JsonpMapper mapper) {
         generator.writeKey("reason");
         this.reason.serialize(generator, mapper);
 
-        generator.writeKey("shard");
+        generator.writeKey("_shard");
         generator.write(this.shard);
 
         if (this.status != null) {
@@ -227,7 +227,7 @@ public Builder copy() {
         }
 
         /**
-         * API name: {@code index}
+         * API name: {@code _index}
          */
         @Nonnull
         public final Builder index(@Nullable String value) {
@@ -236,7 +236,7 @@ public final Builder index(@Nullable String value) {
         }
 
         /**
-         * API name: {@code node}
+         * API name: {@code _node}
          */
         @Nonnull
         public final Builder node(@Nullable String value) {
@@ -271,7 +271,7 @@ public final Builder reason(Function<ErrorCause.Builder, ObjectBuilder<ErrorCaus
         }
 
         /**
-         * Required - API name: {@code shard}
+         * Required - API name: {@code _shard}
          */
         @Nonnull
         public final Builder shard(int value) {
@@ -313,11 +313,11 @@ public ShardFailure build() {
     );
 
     protected static void setupShardFailureDeserializer(ObjectDeserializer<ShardFailure.Builder> op) {
-        op.add(Builder::index, JsonpDeserializer.stringDeserializer(), "index");
-        op.add(Builder::node, JsonpDeserializer.stringDeserializer(), "node");
+        op.add(Builder::index, JsonpDeserializer.stringDeserializer(), "_index");
+        op.add(Builder::node, JsonpDeserializer.stringDeserializer(), "_node");
         op.add(Builder::primary, JsonpDeserializer.booleanDeserializer(), "primary");
         op.add(Builder::reason, ErrorCause._DESERIALIZER, "reason");
-        op.add(Builder::shard, JsonpDeserializer.integerDeserializer(), "shard");
+        op.add(Builder::shard, JsonpDeserializer.integerDeserializer(), "_shard");
         op.add(Builder::status, JsonpDeserializer.stringDeserializer(), "status");
     }
 
diff --git a/java-client/src/generated/java/org/opensearch/client/opensearch/_types/analysis/PathHierarchyTokenizer.java b/java-client/src/generated/java/org/opensearch/client/opensearch/_types/analysis/PathHierarchyTokenizer.java
index c6f3d02aba..3c1077be9a 100644
--- a/java-client/src/generated/java/org/opensearch/client/opensearch/_types/analysis/PathHierarchyTokenizer.java
+++ b/java-client/src/generated/java/org/opensearch/client/opensearch/_types/analysis/PathHierarchyTokenizer.java
@@ -47,7 +47,6 @@
 import org.opensearch.client.json.JsonpMapper;
 import org.opensearch.client.json.ObjectBuilderDeserializer;
 import org.opensearch.client.json.ObjectDeserializer;
-import org.opensearch.client.util.ApiTypeHelper;
 import org.opensearch.client.util.CopyableBuilder;
 import org.opensearch.client.util.ObjectBuilder;
 import org.opensearch.client.util.ToCopyableBuilder;
@@ -61,27 +60,30 @@ public class PathHierarchyTokenizer extends TokenizerBase
         TokenizerDefinitionVariant,
         ToCopyableBuilder<PathHierarchyTokenizer.Builder, PathHierarchyTokenizer> {
 
-    private final int bufferSize;
+    @Nullable
+    private final Integer bufferSize;
 
-    @Nonnull
+    @Nullable
     private final String delimiter;
 
     @Nullable
     private final String replacement;
 
-    private final boolean reverse;
+    @Nullable
+    private final Boolean reverse;
 
-    private final int skip;
+    @Nullable
+    private final Integer skip;
 
     // ---------------------------------------------------------------------------------------------
 
     private PathHierarchyTokenizer(Builder builder) {
         super(builder);
-        this.bufferSize = ApiTypeHelper.requireNonNull(builder.bufferSize, this, "bufferSize");
-        this.delimiter = ApiTypeHelper.requireNonNull(builder.delimiter, this, "delimiter");
+        this.bufferSize = builder.bufferSize;
+        this.delimiter = builder.delimiter;
         this.replacement = builder.replacement;
-        this.reverse = ApiTypeHelper.requireNonNull(builder.reverse, this, "reverse");
-        this.skip = ApiTypeHelper.requireNonNull(builder.skip, this, "skip");
+        this.reverse = builder.reverse;
+        this.skip = builder.skip;
     }
 
     public static PathHierarchyTokenizer of(Function<PathHierarchyTokenizer.Builder, ObjectBuilder<PathHierarchyTokenizer>> fn) {
@@ -97,16 +99,17 @@ public TokenizerDefinition.Kind _tokenizerDefinitionKind() {
     }
 
     /**
-     * Required - API name: {@code buffer_size}
+     * API name: {@code buffer_size}
      */
-    public final int bufferSize() {
+    @Nullable
+    public final Integer bufferSize() {
         return this.bufferSize;
     }
 
     /**
-     * Required - API name: {@code delimiter}
+     * API name: {@code delimiter}
      */
-    @Nonnull
+    @Nullable
     public final String delimiter() {
         return this.delimiter;
     }
@@ -120,38 +123,48 @@ public final String replacement() {
     }
 
     /**
-     * Required - API name: {@code reverse}
+     * API name: {@code reverse}
      */
-    public final boolean reverse() {
+    @Nullable
+    public final Boolean reverse() {
         return this.reverse;
     }
 
     /**
-     * Required - API name: {@code skip}
+     * API name: {@code skip}
      */
-    public final int skip() {
+    @Nullable
+    public final Integer skip() {
         return this.skip;
     }
 
     protected void serializeInternal(JsonGenerator generator, JsonpMapper mapper) {
         generator.write("type", "path_hierarchy");
         super.serializeInternal(generator, mapper);
-        generator.writeKey("buffer_size");
-        generator.write(this.bufferSize);
+        if (this.bufferSize != null) {
+            generator.writeKey("buffer_size");
+            generator.write(this.bufferSize);
+        }
 
-        generator.writeKey("delimiter");
-        generator.write(this.delimiter);
+        if (this.delimiter != null) {
+            generator.writeKey("delimiter");
+            generator.write(this.delimiter);
+        }
 
         if (this.replacement != null) {
             generator.writeKey("replacement");
             generator.write(this.replacement);
         }
 
-        generator.writeKey("reverse");
-        generator.write(this.reverse);
+        if (this.reverse != null) {
+            generator.writeKey("reverse");
+            generator.write(this.reverse);
+        }
 
-        generator.writeKey("skip");
-        generator.write(this.skip);
+        if (this.skip != null) {
+            generator.writeKey("skip");
+            generator.write(this.skip);
+        }
     }
 
     // ---------------------------------------------------------------------------------------------
@@ -171,11 +184,15 @@ public static Builder builder() {
      * Builder for {@link PathHierarchyTokenizer}.
      */
     public static class Builder extends TokenizerBase.AbstractBuilder<Builder> implements CopyableBuilder<Builder, PathHierarchyTokenizer> {
+        @Nullable
         private Integer bufferSize;
+        @Nullable
         private String delimiter;
         @Nullable
         private String replacement;
+        @Nullable
         private Boolean reverse;
+        @Nullable
         private Integer skip;
 
         public Builder() {}
@@ -211,19 +228,19 @@ protected Builder self() {
         }
 
         /**
-         * Required - API name: {@code buffer_size}
+         * API name: {@code buffer_size}
          */
         @Nonnull
-        public final Builder bufferSize(int value) {
+        public final Builder bufferSize(@Nullable Integer value) {
             this.bufferSize = value;
             return this;
         }
 
         /**
-         * Required - API name: {@code delimiter}
+         * API name: {@code delimiter}
          */
         @Nonnull
-        public final Builder delimiter(String value) {
+        public final Builder delimiter(@Nullable String value) {
             this.delimiter = value;
             return this;
         }
@@ -238,19 +255,19 @@ public final Builder replacement(@Nullable String value) {
         }
 
         /**
-         * Required - API name: {@code reverse}
+         * API name: {@code reverse}
          */
         @Nonnull
-        public final Builder reverse(boolean value) {
+        public final Builder reverse(@Nullable Boolean value) {
             this.reverse = value;
             return this;
         }
 
         /**
-         * Required - API name: {@code skip}
+         * API name: {@code skip}
          */
         @Nonnull
-        public final Builder skip(int value) {
+        public final Builder skip(@Nullable Integer value) {
             this.skip = value;
             return this;
         }
@@ -293,11 +310,11 @@ protected static void setupPathHierarchyTokenizerDeserializer(ObjectDeserializer
     @Override
     public int hashCode() {
         int result = super.hashCode();
-        result = 31 * result + Integer.hashCode(this.bufferSize);
-        result = 31 * result + this.delimiter.hashCode();
+        result = 31 * result + Objects.hashCode(this.bufferSize);
+        result = 31 * result + Objects.hashCode(this.delimiter);
         result = 31 * result + Objects.hashCode(this.replacement);
-        result = 31 * result + Boolean.hashCode(this.reverse);
-        result = 31 * result + Integer.hashCode(this.skip);
+        result = 31 * result + Objects.hashCode(this.reverse);
+        result = 31 * result + Objects.hashCode(this.skip);
         return result;
     }
 
@@ -309,10 +326,10 @@ public boolean equals(Object o) {
         if (this == o) return true;
         if (o == null || this.getClass() != o.getClass()) return false;
         PathHierarchyTokenizer other = (PathHierarchyTokenizer) o;
-        return this.bufferSize == other.bufferSize
-            && this.delimiter.equals(other.delimiter)
+        return Objects.equals(this.bufferSize, other.bufferSize)
+            && Objects.equals(this.delimiter, other.delimiter)
             && Objects.equals(this.replacement, other.replacement)
-            && this.reverse == other.reverse
-            && this.skip == other.skip;
+            && Objects.equals(this.reverse, other.reverse)
+            && Objects.equals(this.skip, other.skip);
     }
 }
diff --git a/java-codegen/opensearch-openapi.yaml b/java-codegen/opensearch-openapi.yaml
index b4829f72a0..56f04a451b 100644
--- a/java-codegen/opensearch-openapi.yaml
+++ b/java-codegen/opensearch-openapi.yaml
@@ -38878,8 +38878,6 @@ components:
     _common___DerivedField:
       type: object
       properties:
-        name:
-          type: string
         type:
           type: string
         script:
@@ -38893,7 +38891,6 @@ components:
         format:
           type: string
       required:
-        - name
         - script
         - type
     _common___DFIIndependenceMeasure:
@@ -40834,22 +40831,22 @@ components:
     _common___ShardFailure:
       type: object
       properties:
-        index:
+        _index:
           $ref: '#/components/schemas/_common___IndexName'
-        node:
+        _node:
           type: string
         reason:
           $ref: '#/components/schemas/_common___ErrorCause'
-        shard:
+        _shard:
           type: integer
         status:
           type: string
         primary:
           type: boolean
       required:
+        - _shard
         - primary
         - reason
-        - shard
     _common___ShardInfo:
       type: object
       properties:
@@ -45956,10 +45953,6 @@ components:
             skip:
               $ref: '#/components/schemas/_common___StringifiedInteger'
           required:
-            - buffer_size
-            - delimiter
-            - reverse
-            - skip
             - type
     _common.analysis___PatternAnalyzer:
       type: object