diff --git a/solr/CHANGES.txt b/solr/CHANGES.txt
index 54b21307a4b..cf4cf82ed50 100644
--- a/solr/CHANGES.txt
+++ b/solr/CHANGES.txt
@@ -247,6 +247,10 @@ Bug Fixes
   this issue reverts the default replica placement policy to the 'legacy' assignment policy that was the default until
   Solr 7.4. (Gus Heck, Andrzej Bialecki, Bram Van Dam, shalin)
 
+* SOLR-13255 : ClasscastException when URPs try to read a String field which returns a ByteArrayUTF8CHarSequence . This is a regression
+  in release 7.7 (noble)
+
+
 Improvements
 ----------------------
 
diff --git a/solr/contrib/langid/src/test/org/apache/solr/update/processor/LanguageIdentifierUpdateProcessorFactoryTestCase.java b/solr/contrib/langid/src/test/org/apache/solr/update/processor/LanguageIdentifierUpdateProcessorFactoryTestCase.java
index 9fc3eb10b04..a74c80fea77 100644
--- a/solr/contrib/langid/src/test/org/apache/solr/update/processor/LanguageIdentifierUpdateProcessorFactoryTestCase.java
+++ b/solr/contrib/langid/src/test/org/apache/solr/update/processor/LanguageIdentifierUpdateProcessorFactoryTestCase.java
@@ -17,16 +17,19 @@
 package org.apache.solr.update.processor;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.List;
+
 import org.apache.solr.SolrTestCaseJ4;
 import org.apache.solr.common.SolrInputDocument;
 import org.apache.solr.common.params.ModifiableSolrParams;
+import org.apache.solr.common.util.ByteArrayUtf8CharSequence;
 import org.apache.solr.core.SolrCore;
+import org.apache.solr.response.SolrQueryResponse;
+import org.apache.solr.servlet.SolrRequestParsers;
 import org.junit.Before;
 import org.junit.BeforeClass;
 import org.junit.Test;
-import org.apache.solr.response.SolrQueryResponse;
-import org.apache.solr.servlet.SolrRequestParsers;
 
 public abstract class LanguageIdentifierUpdateProcessorFactoryTestCase extends SolrTestCaseJ4 {
 
@@ -383,6 +386,25 @@ public abstract class LanguageIdentifierUpdateProcessorFactoryTestCase extends S
    */
   private SolrInputDocument process(SolrInputDocument origDoc) {
     SolrInputDocument modifiedDoc = origDoc.deepCopy();
+    if (random().nextBoolean()) {
+      modifiedDoc.forEach((s, f) -> {
+        Object rawVal = f.getRawValue();
+        if (rawVal instanceof Collection) {
+          Collection rawValue = (Collection) rawVal;
+          ArrayList<Object> newVal = new ArrayList<>(rawValue.size());
+          for (Object o : rawValue) {
+            if (o instanceof String) {
+              newVal.add(new ByteArrayUtf8CharSequence((String) o));
+            } else {
+              newVal.add(rawVal);
+            }
+          }
+          f.setValue(newVal);
+        } else if (rawVal instanceof String) {
+          f.setValue(new ByteArrayUtf8CharSequence((String) rawVal));
+        }
+      });
+    }
     liProcessor.process(modifiedDoc);
     return modifiedDoc;
   }
diff --git a/solr/core/src/java/org/apache/solr/update/DocumentBuilder.java b/solr/core/src/java/org/apache/solr/update/DocumentBuilder.java
index 86f555ca9c2..90694ff62b2 100644
--- a/solr/core/src/java/org/apache/solr/update/DocumentBuilder.java
+++ b/solr/core/src/java/org/apache/solr/update/DocumentBuilder.java
@@ -135,7 +135,7 @@ public class DocumentBuilder {
     // Load fields from SolrDocument to Document
     for( SolrInputField field : doc ) {
 
-      if (field.getFirstValue() instanceof SolrDocumentBase) {
+      if (field.getFirstRawValue() instanceof SolrDocumentBase) {
         if (ignoreNestedDocs) {
           continue;
         }
@@ -159,7 +159,9 @@ public class DocumentBuilder {
       // load each field value
       boolean hasField = false;
       try {
-        for( Object v : field ) {
+        Iterator it = field.getRawIterator();
+        while (it.hasNext()) {
+          Object v = it.next();
           if( v == null ) {
             continue;
           }
diff --git a/solr/solrj/src/java/org/apache/solr/common/SolrInputField.java b/solr/solrj/src/java/org/apache/solr/common/SolrInputField.java
index 5d99d92d92c..8b4add6523b 100644
--- a/solr/solrj/src/java/org/apache/solr/common/SolrInputField.java
+++ b/solr/solrj/src/java/org/apache/solr/common/SolrInputField.java
@@ -21,6 +21,8 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Iterator;
 
+import static org.apache.solr.common.util.ByteArrayUtf8CharSequence.convertCharSeq;
+
 /**
  *
  * @since solr 1.3
@@ -111,11 +113,11 @@ public class SolrInputField implements Iterable<Object>, Serializable
     if( value instanceof Collection ) {
       Collection c = (Collection<Object>)value;
       if( c.size() > 0 ) {
-        return c.iterator().next();
+        return convertCharSeq(c.iterator().next());
       }
       return null;
     }
-    return value;
+    return convertCharSeq(value);
   }
 
   /**
@@ -123,6 +125,28 @@ public class SolrInputField implements Iterable<Object>, Serializable
    * will be a collection.
    */
   public Object getValue() {
+    return convertCharSeq(value);
+  }
+
+
+  /**
+   * Return a value as is without converting and CharSequence Objects
+   */
+  public Object getRawValue() {
+    return value;
+  }
+
+  /**
+   * Return the first value as is without converting and CharSequence Objects
+   */
+  public Object getFirstRawValue() {
+    if (value instanceof Collection) {
+      Collection c = (Collection<Object>) value;
+      if (c.size() > 0) {
+        return c.iterator().next();
+      }
+      return null;
+    }
     return value;
   }
 
@@ -132,12 +156,12 @@ public class SolrInputField implements Iterable<Object>, Serializable
    */
   @SuppressWarnings("unchecked")
   public Collection<Object> getValues() {
-    if( value instanceof Collection ) {
-      return (Collection<Object>)value;
+    if (value instanceof Collection) {
+      return convertCharSeq((Collection<Object>) value);
     }
     if( value != null ) {
       Collection<Object> vals = new ArrayList<>(1);
-      vals.add( value );
+      vals.add(convertCharSeq(value));
       return vals;
     }
     return null;
@@ -165,8 +189,33 @@ public class SolrInputField implements Iterable<Object>, Serializable
   }
 
   @Override
+  public Iterator<Object> iterator(){
+    if( value instanceof Collection ) {
+      return (convertCharSeq ((Collection)value)).iterator();
+    }
+    return new Iterator<Object>() {
+      boolean nxt = (value!=null);
+
+      @Override
+      public boolean hasNext() {
+        return nxt;
+      }
+
+      @Override
+      public Object next() {
+        nxt = false;
+        return convertCharSeq(value);
+      }
+
+      @Override
+      public void remove() {
+        throw new UnsupportedOperationException();
+      }
+    };
+
+  }
   @SuppressWarnings("unchecked")
-  public Iterator<Object> iterator() {
+  public Iterator<Object> getRawIterator() {
     if( value instanceof Collection ) {
       return ((Collection)value).iterator();
     }
diff --git a/solr/solrj/src/java/org/apache/solr/common/util/ByteArrayUtf8CharSequence.java b/solr/solrj/src/java/org/apache/solr/common/util/ByteArrayUtf8CharSequence.java
index c9a05cb1548..7a4abe2c303 100644
--- a/solr/solrj/src/java/org/apache/solr/common/util/ByteArrayUtf8CharSequence.java
+++ b/solr/solrj/src/java/org/apache/solr/common/util/ByteArrayUtf8CharSequence.java
@@ -73,6 +73,10 @@ public class ByteArrayUtf8CharSequence implements Utf8CharSequence {
     return buf[offset + idx];
   }
 
+  /**
+   * this is for internal use to get a cached string value.
+   * returns null if There is no cached String value
+   */
   public String getStringOrNull() {
     return utf16;
   }
@@ -209,6 +213,7 @@ public class ByteArrayUtf8CharSequence implements Utf8CharSequence {
   public static Object convertCharSeq(Object o) {
     if (o == null) return null;
     if (o instanceof Utf8CharSequence) return ((Utf8CharSequence) o).toString();
+    if (o instanceof Collection) return convertCharSeq((Collection) o);
     return o;
   }
 
diff --git a/solr/solrj/src/java/org/apache/solr/common/util/JavaBinCodec.java b/solr/solrj/src/java/org/apache/solr/common/util/JavaBinCodec.java
index 9535ee16357..4295d25148b 100644
--- a/solr/solrj/src/java/org/apache/solr/common/util/JavaBinCodec.java
+++ b/solr/solrj/src/java/org/apache/solr/common/util/JavaBinCodec.java
@@ -357,7 +357,7 @@ public class JavaBinCodec implements PushWriter {
       return true;
     }
     if (val instanceof SolrInputField) {
-      return writeKnownType(((SolrInputField) val).getValue());
+      return writeKnownType(((SolrInputField) val).getRawValue());
     }
     if (val instanceof IteratorWriter) {
       writeIterator((IteratorWriter) val);