diff --git a/files/constants.php b/files/constants.php
index f8de8181..33be7e65 100644
--- a/files/constants.php
+++ b/files/constants.php
@@ -160,6 +160,7 @@
 const PHPFHIR_TEST_CLASSNAME_VERSION_CONFIG = PHPFHIR_CLASSNAME_VERSION_CONFIG . 'Test';
 const PHPFHIR_TEST_ENCODING_CLASSNAME_UNSERIALIZE_CONFIG = PHPFHIR_ENCODING_CLASSNAME_UNSERIALIZE_CONFIG . 'Test';
 const PHPFHIR_TEST_ENCODING_CLASSNAME_SERIALIZE_CONFIG = PHPFHIR_ENCODING_CLASSNAME_SERIALIZE_CONFIG . 'Test';
+const PHPFHIR_TEST_ENCODING_CLASSSNAME_XML_WRITER = PHPFHIR_ENCODING_CLASSNAME_XML_WRITER . 'Test';
 
 // Test constant names
 const PHPFHIR_TEST_CONSTANT_INTEGRATION_ENDPOINT = 'PHPFHIR_TEST_INTEGRATION_ENDPOINT';
diff --git a/files/funcs.php b/files/funcs.php
index 91cd65b5..41a9206f 100644
--- a/files/funcs.php
+++ b/files/funcs.php
@@ -19,13 +19,22 @@
 /**
  * require_with is used to ensure a clean context per required template file.
  *
- * @param string $requiredFile
+ * @param string $_filename
  * @param array $vars
  * @return mixed
  */
-function require_with(string $requiredFile, array $vars): mixed
+function require_with(string $_filename, array $vars): mixed
 {
-    $num = extract($vars, EXTR_OVERWRITE);
+    if (array_key_exists('_filename', $vars)) {
+        throw new \InvalidArgumentException('Cannot set "_filename" as key in $vars array.');
+    } else if (array_key_exists('_realpath', $vars)) {
+        throw new \InvalidArgumentException('Cannot set "_realpath" as key in $vars array.');
+    }
+    $_realpath = realpath($_filename);
+    if (false === $_realpath) {
+        throw new \RuntimeException(sprintf('Unable to resolve path for file "%s"', $_filename));
+    }
+    $num = extract($vars);
     if ($num !== count($vars)) {
         throw new \RuntimeException(
             sprintf(
@@ -37,8 +46,8 @@ function require_with(string $requiredFile, array $vars): mixed
         );
     }
     // unset vars defined by this func
-    unset($vars, $num);
-    return require $requiredFile;
+    unset($vars, $num, $_filename);
+    return require $_realpath;
 }
 
 /**
@@ -64,12 +73,9 @@ function pretty_var_export(mixed $var, int $indent = 0, bool $indentFirst = fals
     foreach ($var as $k => $v) {
         $literal = false;
         $indentFirst = is_int($k);
-        // TODO: if it works, is it really a shit idea?  Probably.
-        if ('libxmlOptMask' === $k) {
-            $k = 'libxmlOpts';
-            $literal = true;
-        } else if ('xhtmlLibxmlOptMask' === $k) {
-            $k = 'xhtmlLibxmlOpts';
+        // handle output of option mask constant names.
+        if (is_string($k) && str_ends_with($k, 'OptMask')) {
+            $k = str_replace('OptMask', 'Opts', $k);
             $literal = true;
         }
         $out = sprintf("%s\n%s%s => %s,",
diff --git a/template/core/encoding/class_xml_writer.php b/template/core/encoding/class_xml_writer.php
index f55ca315..fd4a0a51 100644
--- a/template/core/encoding/class_xml_writer.php
+++ b/template/core/encoding/class_xml_writer.php
@@ -41,13 +41,21 @@ final class <?php echo PHPFHIR_ENCODING_CLASSNAME_XML_WRITER; ?> extends \XMLWri
 {
     private const _MEM = 'memory';
 
-    /** @var bool */
+    private <?php echo $serializeConfigClass->getEntityName(); ?> $_config;
     private bool $_docStarted = false;
-    /** @var bool */
     private bool $_rootOpen = false;
-    /** @var null|string */
     private null|string $_open = null;
 
+    /**
+     * <?php echo $coreFile->getEntityName(); ?> constructor.
+     *
+     * @param <?php echo $serializeConfigClass->getFullyQualifiedName(true); ?> $config
+     */
+    public function __construct(<?php echo $serializeConfigClass->getEntityName(); ?> $config)
+    {
+        $this->_config = $config;
+    }
+
     /**
      * @see https://www.php.net/manual/en/xmlwriter.openmemory.php
      *
@@ -132,23 +140,24 @@ public function isRootOpen(): bool
     }
 
     /**
-     * @param <?php echo $serializeConfigClass->getFullyQualifiedName(true); ?> $config
      * @param string $name
      * @param string|null $sourceXMLNS
      * @return bool
      */
-    public function openRootNode(<?php echo PHPFHIR_ENCODING_CLASSNAME_SERIALIZE_CONFIG; ?> $config, string $name, null|string $sourceXMLNS): bool
+    public function openRootNode(string $name, null|string $sourceXMLNS): bool
     {
         if (null === $this->_open) {
             throw new \LogicException('Must open write destination before writing root node');
         } else if (!$this->_docStarted) {
             throw new \LogicException('Document must be started before writing root node');
+        } else if ($this->_rootOpen) {
+            throw new \LogicException('Root node is already open');
         }
         if (!$this->startElement($name)) {
             return false;
         }
-        if ($config->getOverrideSourceXMLNS() || null === $sourceXMLNS) {
-            $ns = (string)$config->getRootXMLNS();
+        if ($this->_config->getOverrideSourceXMLNS() || null === $sourceXMLNS) {
+            $ns = (string)$this->_config->getRootXMLNS();
         } else {
             $ns = $sourceXMLNS;
         }
diff --git a/template/core/tests/encoding/test_class_serialize_config.php b/template/core/tests/encoding/test_class_serialize_config.php
index 808581f2..ff41d6c5 100644
--- a/template/core/tests/encoding/test_class_serialize_config.php
+++ b/template/core/tests/encoding/test_class_serialize_config.php
@@ -16,7 +16,6 @@
  * limitations under the License.
  */
 
-
 use DCarbone\PHPFHIR\Utilities\ImportUtils;
 
 /** @var \DCarbone\PHPFHIR\Config $config */
@@ -43,7 +42,7 @@
 
 class <?php echo PHPFHIR_TEST_ENCODING_CLASSNAME_SERIALIZE_CONFIG; ?> extends TestCase
 {
-    public function testEmptyConstruct()
+    public function testCanConstructWithoutParams()
     {
         $sc = new <?php echo $serializeConfigClass->getEntityName(); ?>();
         $this->assertFalse($sc->getOverrideSourceXMLNS());
@@ -51,7 +50,7 @@ public function testEmptyConstruct()
         $this->assertEquals(<?php echo PHPFHIR_DEFAULT_LIBXML_OPTS ?>, $sc->getXHTMLLibxmlOpts());
     }
 
-    public function testValuedConstruct()
+    public function testCanConstructWithValidValues()
     {
         $sc = new <?php echo $serializeConfigClass->getEntityName(); ?>(overrideSourceXMLNS: true, rootXMLNS: 'urn:foo:bar', xhtmlLibxmlOpts: 123);
         $this->assertTrue($sc->getOverrideSourceXMLNS());
diff --git a/template/core/tests/encoding/test_class_unserialize_config.php b/template/core/tests/encoding/test_class_unserialize_config.php
index 205889ab..8e3fd541 100644
--- a/template/core/tests/encoding/test_class_unserialize_config.php
+++ b/template/core/tests/encoding/test_class_unserialize_config.php
@@ -16,7 +16,6 @@
  * limitations under the License.
  */
 
-
 use DCarbone\PHPFHIR\Utilities\ImportUtils;
 
 /** @var \DCarbone\PHPFHIR\Config $config */
@@ -42,14 +41,14 @@
 
 class <?php echo PHPFHIR_TEST_ENCODING_CLASSNAME_UNSERIALIZE_CONFIG; ?> extends TestCase
 {
-    public function testEmptyConstruct()
+    public function testCanConstructWithoutParams()
     {
         $uc = new <?php echo $unserializeConfigClass->getEntityName(); ?>();
         $this->assertEquals(<?php echo PHPFHIR_DEFAULT_LIBXML_OPTS; ?>, $uc->getLibxmlOpts());
         $this->assertEquals(512, $uc->getJSONDecodeMaxDepth());
     }
 
-    public function testValuedConstruct()
+    public function testCanConstructWithValidValues()
     {
         $uc = new <?php echo $unserializeConfigClass->getEntityName(); ?>(libxmlOpts: 123, jsonDecodeMaxDepth: 456);
         $this->assertEquals(123, $uc->getLibxmlOpts());
diff --git a/template/core/tests/encoding/test_class_xml_writer.php b/template/core/tests/encoding/test_class_xml_writer.php
new file mode 100644
index 00000000..bd0470ab
--- /dev/null
+++ b/template/core/tests/encoding/test_class_xml_writer.php
@@ -0,0 +1,143 @@
+<?php declare(strict_types=1);
+
+/*
+ * Copyright 2025 Daniel Carbone (daniel.p.carbone@gmail.com)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+use DCarbone\PHPFHIR\Utilities\ImportUtils;
+
+/** @var \DCarbone\PHPFHIR\Config $config */
+/** @var \DCarbone\PHPFHIR\CoreFile $coreFile */
+
+$imports = $coreFile->getImports();
+$imports->addCoreFileImportsByName(
+    PHPFHIR_ENCODING_CLASSNAME_SERIALIZE_CONFIG,
+    PHPFHIR_ENCODING_CLASSNAME_XML_WRITER,
+);
+
+$coreFiles = $config->getCoreFiles();
+
+$xmlWriterClass = $coreFiles->getCoreFileByEntityName(PHPFHIR_ENCODING_CLASSNAME_XML_WRITER);
+$serializeConfigClass = $coreFiles->getCoreFileByEntityName(PHPFHIR_ENCODING_CLASSNAME_SERIALIZE_CONFIG);
+
+ob_start();
+echo "<?php\n\n";?>
+namespace <?php echo $coreFile->getFullyQualifiedNamespace(false); ?>;
+
+<?php echo $config->getBasePHPFHIRCopyrightComment(false); ?>
+
+<?php echo ImportUtils::compileImportStatements($imports); ?>
+use PHPUnit\Framework\TestCase;
+
+class <?php echo PHPFHIR_TEST_ENCODING_CLASSSNAME_XML_WRITER; ?> extends TestCase
+{
+    public function testCanConstructWithDefaultConfig()
+    {
+        $sc = new <?php echo $serializeConfigClass->getEntityName(); ?>();
+        $xw = new <?php echo $xmlWriterClass->getEntityName(); ?>($sc);
+        $this->assertFalse($xw->isOpen());
+        $this->assertNull($xw->getWriteDestination());
+        $this->assertFalse($xw->isDocStarted());
+        $this->assertFalse($xw->isRootOpen());
+    }
+
+    public function testCanGetMemoryWriteDestination()
+    {
+        $sc = new <?php echo $serializeConfigClass->getEntityName(); ?>();
+        $xw = new <?php echo $xmlWriterClass->getEntityName(); ?>($sc);
+        $this->assertTrue($xw->openMemory());
+        $this->assertEquals('memory', $xw->getWriteDestination());
+    }
+
+    public function testCanGetUriWriteDestination()
+    {
+        $sc = new <?php echo $serializeConfigClass->getEntityName(); ?>();
+        $xw = new <?php echo $xmlWriterClass->getEntityName(); ?>($sc);
+        $this->assertTrue($xw->openUri('php://memory'));
+        $this->assertEquals('php://memory', $xw->getWriteDestination());
+    }
+
+    public function testCannotOpenMemoryTwice()
+    {
+        $this->expectException(\LogicException::class);
+        $sc = new <?php echo $serializeConfigClass->getEntityName(); ?>();
+        $xw = new <?php echo $xmlWriterClass->getEntityName(); ?>($sc);
+        $this->assertTrue($xw->openMemory());
+        $xw->openMemory();
+    }
+
+    public function testCannotOpenUriTwice()
+    {
+        $this->expectException(\LogicException::class);
+        $sc = new <?php echo $serializeConfigClass->getEntityName(); ?>();
+        $xw = new <?php echo $xmlWriterClass->getEntityName(); ?>($sc);
+        $this->assertTrue($xw->openUri('php://memory'));
+        $xw->openUri('php://memory');
+    }
+
+    public function testCannotOpenMixedTwice()
+    {
+        $this->expectException(\LogicException::class);
+        $sc = new <?php echo $serializeConfigClass->getEntityName(); ?>();
+        $xw = new <?php echo $xmlWriterClass->getEntityName(); ?>($sc);
+        $this->assertTrue($xw->openMemory());
+        $xw->openUri('php://memory');
+    }
+
+    public function testCanStartDocument()
+    {
+        $sc = new <?php echo $serializeConfigClass->getEntityName(); ?>();
+        $xw = new <?php echo $xmlWriterClass->getEntityName(); ?>($sc);
+        $this->assertFalse($xw->isDocStarted());
+        $this->assertTrue($xw->openMemory());
+        $this->assertTrue($xw->startDocument());
+        $this->assertTrue($xw->isDocStarted());
+    }
+
+    public function testCannotStartDocumentTwice()
+    {
+        $this->expectException(\LogicException::class);
+        $sc = new <?php echo $serializeConfigClass->getEntityName(); ?>();
+        $xw = new <?php echo $xmlWriterClass->getEntityName(); ?>($sc);
+        $this->assertTrue($xw->openMemory());
+        $this->assertTrue($xw->startDocument());
+        $xw->startDocument();
+    }
+
+    public function testCanOpenRootNode()
+    {
+        $sc = new <?php echo $serializeConfigClass->getEntityName(); ?>();
+        $xw = new <?php echo $xmlWriterClass->getEntityName(); ?>($sc);
+        $this->assertTrue($xw->openMemory());
+        $this->assertTrue($xw->startDocument());
+        $this->assertFalse($xw->isRootOpen());
+        $this->assertTrue($xw->openRootNode('root', null));
+        $this->assertTrue($xw->isRootOpen());
+    }
+
+    public function testCannotOpenRootNodeTwice()
+    {
+        $this->expectException(\LogicException::class);
+        $sc = new <?php echo $serializeConfigClass->getEntityName(); ?>();
+        $xw = new <?php echo $xmlWriterClass->getEntityName(); ?>($sc);
+        $this->assertTrue($xw->openMemory());
+        $this->assertTrue($xw->startDocument());
+        $this->assertFalse($xw->isRootOpen());
+        $this->assertTrue($xw->openRootNode('root', null));
+        $this->assertTrue($xw->isRootOpen());
+        $this->assertTrue($xw->openRootNode('root', null));
+    }
+}
+<?php return ob_get_clean();
diff --git a/template/core/tests/test_class_version_config.php b/template/core/tests/test_class_version_config.php
index 02e87537..ac16d3ae 100644
--- a/template/core/tests/test_class_version_config.php
+++ b/template/core/tests/test_class_version_config.php
@@ -46,7 +46,7 @@
 
 class <?php echo PHPFHIR_TEST_CLASSNAME_VERSION_CONFIG; ?> extends TestCase
 {
-    public function testEmptyConstruct()
+    public function testCanConstructWithoutParams()
     {
         $vc = new <?php echo $versionConfigClass->getEntityName(); ?>();
         $uc = $vc->getUnserializeConfig();
@@ -60,7 +60,7 @@ public function testEmptyConstruct()
         $this->assertEquals(<?php echo PHPFHIR_DEFAULT_LIBXML_OPTS; ?>, $sc->getXHTMLLibxmlOpts());
     }
 
-    public function testArrayConstruct()
+    public function testCanConstructWithValidMapParams()
     {
         $vc = new <?php echo $versionConfigClass->getEntityName(); ?>(
             unserializeConfig: ['libxmlOpts' => 456, 'jsonDecodeMaxDepth' => 789],
@@ -77,7 +77,7 @@ public function testArrayConstruct()
         $this->assertEquals(123, $sc->getXHTMLLibxmlOpts());
     }
 
-    public function testValuedConstruct()
+    public function testCanConstructWithValidObjectParams()
     {
         $vc = new <?php echo $versionConfigClass->getEntityName(); ?>(
             unserializeConfig: new <?php echo $unserializeConfigClass->getEntityName(); ?>(),
diff --git a/template/versions/types/class_default.php b/template/versions/types/class_default.php
index 14c5b805..787435b2 100644
--- a/template/versions/types/class_default.php
+++ b/template/versions/types/class_default.php
@@ -31,7 +31,7 @@
 
 // build file header
 echo require_with(
-    PHPFHIR_TEMPLATE_VERSION_TYPES_DIR . DIRECTORY_SEPARATOR . 'header.php',
+    PHPFHIR_TEMPLATE_VERSION_TYPES_DIR . '/header.php',
     [
         'version' => $version,
         'type' => $type,
@@ -99,7 +99,7 @@
 // -- end field properties
 
 echo require_with(
-    PHPFHIR_TEMPLATE_VERSION_TYPES_METHODS_DIR . DIRECTORY_SEPARATOR . 'constructor.php',
+    PHPFHIR_TEMPLATE_VERSION_TYPES_METHODS_DIR . '/constructor.php',
     [
         'version' => $version,
         'type' => $type,
@@ -134,7 +134,7 @@ public function _getResourceType(): string
 
     if ($type->getKind()->isOneOf(TypeKindEnum::PRIMITIVE, TypeKindEnum::LIST)) :
         echo require_with(
-            PHPFHIR_TEMPLATE_VERSION_TYPES_PROPERTIES_DIR . DIRECTORY_SEPARATOR . 'methods' . DIRECTORY_SEPARATOR . 'primitive.php',
+            PHPFHIR_TEMPLATE_VERSION_TYPES_PROPERTIES_DIR . '/methods/primitive.php',
             [
                 'version' => $version,
                 'type' => $type
@@ -142,7 +142,7 @@ public function _getResourceType(): string
         );
     else :
         echo require_with(
-            PHPFHIR_TEMPLATE_VERSION_TYPES_PROPERTIES_DIR . DIRECTORY_SEPARATOR . 'methods' . DIRECTORY_SEPARATOR . 'default.php',
+            PHPFHIR_TEMPLATE_VERSION_TYPES_PROPERTIES_DIR . '/methods/default.php',
             [
                 'version' => $version,
                 'type' => $type,
@@ -157,7 +157,7 @@ public function _getResourceType(): string
     echo "\n";
 
     echo require_with(
-        PHPFHIR_TEMPLATE_VERSION_TYPES_VALIDATION_DIR . DIRECTORY_SEPARATOR . 'methods.php',
+        PHPFHIR_TEMPLATE_VERSION_TYPES_VALIDATION_DIR . '/methods.php',
         [
             'version' => $version,
             'type' => $type,
@@ -169,7 +169,7 @@ public function _getResourceType(): string
     echo "\n";
 
     echo require_with(
-        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . DIRECTORY_SEPARATOR . 'xml.php',
+        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . '/xml.php',
         [
             'version' => $version,
             'type'     => $type,
@@ -179,7 +179,7 @@ public function _getResourceType(): string
     echo "\n";
 
     echo require_with(
-        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . DIRECTORY_SEPARATOR . 'json.php',
+        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . '/json.php',
         [
             'version' => $version,
             'type' => $type,
diff --git a/template/versions/types/class_resource_container.php b/template/versions/types/class_resource_container.php
index e10d68de..b1439c21 100644
--- a/template/versions/types/class_resource_container.php
+++ b/template/versions/types/class_resource_container.php
@@ -38,7 +38,7 @@
 
 // build file header
 echo require_with(
-    PHPFHIR_TEMPLATE_VERSION_TYPES_DIR . DIRECTORY_SEPARATOR . 'header.php',
+    PHPFHIR_TEMPLATE_VERSION_TYPES_DIR . '/header.php',
     [
         'version' => $version,
         'type' => $type,
@@ -107,7 +107,7 @@ public function setContainedType(null|<?php echo $versionContainedTypeInterface-
 
 <?php
 echo require_with(
-        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . DIRECTORY_SEPARATOR . 'xml' . DIRECTORY_SEPARATOR . 'unserialize' . DIRECTORY_SEPARATOR . 'header.php',
+        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . '/xml/unserialize/header.php',
     [
         'version' => $version,
         'type' => $type,
@@ -165,7 +165,7 @@ public function xmlSerialize(null|<?php echo PHPFHIR_ENCODING_CLASSNAME_XML_WRIT
 <?php
 // unserialize portion
 echo require_with(
-        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . DIRECTORY_SEPARATOR . 'json' . DIRECTORY_SEPARATOR . 'unserialize' . DIRECTORY_SEPARATOR . 'header.php',
+        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . '/json/unserialize/header.php',
     [
         'version' => $version,
         'type' => $type,
diff --git a/template/versions/types/class_xhtml.php b/template/versions/types/class_xhtml.php
index 74867a90..e7551b2c 100644
--- a/template/versions/types/class_xhtml.php
+++ b/template/versions/types/class_xhtml.php
@@ -34,7 +34,7 @@
 
 // build file header
 echo require_with(
-    PHPFHIR_TEMPLATE_VERSION_TYPES_DIR . DIRECTORY_SEPARATOR . 'header.php',
+    PHPFHIR_TEMPLATE_VERSION_TYPES_DIR . '/header.php',
     [
         'version' => $version,
         'type' => $type,
@@ -148,7 +148,7 @@ public function getXMLReader(int $libxmlOpts): null|\XMLReader
 <?php
 // unserialize portion
 echo require_with(
-        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . DIRECTORY_SEPARATOR . 'xml' . DIRECTORY_SEPARATOR . 'unserialize' . DIRECTORY_SEPARATOR . 'header.php',
+    PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . '/xml/unserialize/header.php',
     [
         'version' => $version,
         'type' => $type,
@@ -159,32 +159,15 @@ public function getXMLReader(int $libxmlOpts): null|\XMLReader
         return $type;
     }
 
-    /**
-     * @param null|<?php echo $xmlWriterClass->getFullyQualifiedName(true); ?> $xw
-     * @param null|<?php echo $serializeConfigClass->getFullyQualifiedName(true); ?> $config
-     * @return <?php echo $xmlWriterClass->getFullyQualifiedName(true); ?>
-
-     */
-    public function xmlSerialize(null|<?php echo PHPFHIR_ENCODING_CLASSNAME_XML_WRITER; ?> $xw = null, null|<?php echo PHPFHIR_ENCODING_CLASSNAME_SERIALIZE_CONFIG; ?> $config = null): <?php echo PHPFHIR_ENCODING_CLASSNAME_XML_WRITER; ?>
-
-    {
-        if (null === $xw) {
-            $xw = new <?php echo PHPFHIR_ENCODING_CLASSNAME_XML_WRITER; ?>();
-        }
-        if (!$xw->isOpen()) {
-            $xw->openMemory();
-        }
-        if (!$xw->isDocStarted()) {
-            $docStarted = true;
-            $xw->startDocument();
-        }
-        if (null === $config) {
-            $config = (new <?php echo PHPFHIR_VERSION_CLASSNAME_VERSION; ?>())->getConfig()->getSerializeConfig();
-        }
-        if (!$xw->isRootOpen()) {
-            $rootOpened = true;
-            $xw->openRootNode($config, 'XHTML', $this->_getSourceXMLNS());
-        }
+<?php
+echo require_with(
+    PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . '/xml/serialize/header.php',
+        [
+        'version' => $version,
+        'type' => $type,
+    ]
+);
+?>
         $xr = $this->getXMLReader($config->getXHTMLLibxmlOpts());
         if (null === $xr) {
             return $xw;
@@ -203,13 +186,7 @@ public function xmlSerialize(null|<?php echo PHPFHIR_ENCODING_CLASSNAME_XML_WRIT
     }
 
 <?php echo require_with(
-    PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR
-    . DIRECTORY_SEPARATOR
-    . 'json'
-    . DIRECTORY_SEPARATOR
-    . 'unserialize'
-    . DIRECTORY_SEPARATOR
-    . 'header.php',
+    PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . '/json/unserialize/header.php',
     [
         'version' => $version,
         'type'     => $type,
diff --git a/template/versions/types/methods/constructor.php b/template/versions/types/methods/constructor.php
index 126cdd9f..1500d807 100644
--- a/template/versions/types/methods/constructor.php
+++ b/template/versions/types/methods/constructor.php
@@ -105,7 +105,7 @@ public function __construct(<?php foreach($type->getAllPropertiesIndexedIterator
         continue;
     }
     echo require_with(
-        PHPFHIR_TEMPLATE_VERSION_TYPES_CONSTRUCTORS_DIR . DIRECTORY_SEPARATOR . 'default_property_setter_call.php',
+        PHPFHIR_TEMPLATE_VERSION_TYPES_CONSTRUCTORS_DIR . '/default_property_setter_call.php',
         [
             'type' => $type,
             'property' => $property
diff --git a/template/versions/types/properties/methods/primitive.php b/template/versions/types/properties/methods/primitive.php
index b4ad1f94..d65ae729 100644
--- a/template/versions/types/properties/methods/primitive.php
+++ b/template/versions/types/properties/methods/primitive.php
@@ -50,11 +50,11 @@ public function getValue(): <?php echo TypeHintUtils::primitivePHPValueTypeHint(
     case PrimitiveTypeEnum::MARKDOWN: // TODO: markdown lib, maybe?
     case PrimitiveTypeEnum::UUID: // TODO: implement uuid lib?
     case PrimitiveTypeEnum::URL: // TODO: create specific URL type?
-        $typeFile = __DIR__ . DIRECTORY_SEPARATOR . 'primitive' . DIRECTORY_SEPARATOR . 'string_type.php';
+        $typeFile = __DIR__ . DIRECTORY_SEPARATOR . 'primitive/string_type.php';
         break;
 
     case PrimitiveTypeEnum::BOOLEAN:
-        $typeFile = __DIR__ . DIRECTORY_SEPARATOR . 'primitive' . DIRECTORY_SEPARATOR . 'bool_type.php';
+        $typeFile = __DIR__ . DIRECTORY_SEPARATOR . 'primitive/bool_type.php';
         break;
 
     // int types
@@ -62,35 +62,35 @@ public function getValue(): <?php echo TypeHintUtils::primitivePHPValueTypeHint(
     case PrimitiveTypeEnum::INTEGER64:
     case PrimitiveTypeEnum::POSITIVE_INTEGER:
     case PrimitiveTypeEnum::NEGATIVE_INTEGER:
-        $typeFile = __DIR__ . DIRECTORY_SEPARATOR . 'primitive' . DIRECTORY_SEPARATOR . 'integer_type.php';
+        $typeFile = __DIR__ . DIRECTORY_SEPARATOR . 'primitive/integer_type.php';
         break;
 
     // treat uint64's as strings for the moment.
     case PrimitiveTypeEnum::UNSIGNED_INTEGER:
-        $typeFile = __DIR__ . DIRECTORY_SEPARATOR . 'primitive' . DIRECTORY_SEPARATOR . 'unsigned_integer_type.php';
+        $typeFile = __DIR__ . DIRECTORY_SEPARATOR . 'primitive/unsigned_integer_type.php';
         break;
 
     case PrimitiveTypeEnum::DECIMAL:
-        $typeFile = __DIR__ . DIRECTORY_SEPARATOR . 'primitive' . DIRECTORY_SEPARATOR . 'decimal_type.php';
+        $typeFile = __DIR__ . DIRECTORY_SEPARATOR . 'primitive/decimal_type.php';
         break;
 
     // date types
     case PrimitiveTypeEnum::DATE:
-        $typeFile = __DIR__ . DIRECTORY_SEPARATOR . 'primitive' . DIRECTORY_SEPARATOR . 'date_type.php';
+        $typeFile = __DIR__ . DIRECTORY_SEPARATOR . 'primitive/date_type.php';
         break;
     case PrimitiveTypeEnum::DATETIME:
-        $typeFile = __DIR__ . DIRECTORY_SEPARATOR . 'primitive' . DIRECTORY_SEPARATOR . 'datetime_type.php';
+        $typeFile = __DIR__ . DIRECTORY_SEPARATOR . 'primitive/datetime_type.php';
         break;
     case PrimitiveTypeEnum::TIME:
-        $typeFile = __DIR__ . DIRECTORY_SEPARATOR . 'primitive' . DIRECTORY_SEPARATOR . 'time_type.php';
+        $typeFile = __DIR__ . DIRECTORY_SEPARATOR . 'primitive/time_type.php';
         break;
     case PrimitiveTypeEnum::INSTANT:
-        $typeFile = __DIR__ . DIRECTORY_SEPARATOR . 'primitive' . DIRECTORY_SEPARATOR . 'instant_type.php';
+        $typeFile = __DIR__ . DIRECTORY_SEPARATOR . 'primitive/instant_type.php';
         break;
 
     case PrimitiveTypeEnum::BASE64_BINARY:
         // TODO: add content decoding?
-        $typeFile = __DIR__ . DIRECTORY_SEPARATOR . 'primitive' . DIRECTORY_SEPARATOR . 'base64_binary_type.php';
+        $typeFile = __DIR__ . DIRECTORY_SEPARATOR . 'primitive/base64_binary_type.php';
         break;
 
     default:
diff --git a/template/versions/types/serialization/json.php b/template/versions/types/serialization/json.php
index 68690d00..0bd2c7d9 100644
--- a/template/versions/types/serialization/json.php
+++ b/template/versions/types/serialization/json.php
@@ -26,13 +26,7 @@
 ob_start();
 
 echo require_with(
-    PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR
-    . DIRECTORY_SEPARATOR
-    . 'json'
-    . DIRECTORY_SEPARATOR
-    . 'unserialize'
-    . DIRECTORY_SEPARATOR
-    . 'header.php',
+    PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . '/json/unserialize/header.php',
     [
         'version' => $version,
         'type'     => $type,
@@ -42,13 +36,7 @@
 echo "\n";
 
 echo require_with(
-    PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR
-    . DIRECTORY_SEPARATOR
-    . 'json'
-    . DIRECTORY_SEPARATOR
-    . 'unserialize'
-    . DIRECTORY_SEPARATOR
-    . 'body.php',
+    PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . '/json/unserialize/body.php',
     [
         'version' => $version,
         'type'     => $type,
@@ -59,13 +47,7 @@
 
 if ($typeKind->isOneOf(TypeKindEnum::PRIMITIVE, TypeKindEnum::LIST)) :
     echo require_with(
-        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR
-        . DIRECTORY_SEPARATOR
-        . 'json'
-        . DIRECTORY_SEPARATOR
-        . 'serialize'
-        . DIRECTORY_SEPARATOR
-        . 'primitive.php',
+        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . '/json/serialize/primitive.php',
         [
             'version' => $version,
             'type'     => $type,
@@ -73,13 +55,7 @@
     );
 else:
     echo require_with(
-        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR
-        . DIRECTORY_SEPARATOR
-        . 'json'
-        . DIRECTORY_SEPARATOR
-        . 'serialize'
-        . DIRECTORY_SEPARATOR
-        . 'default.php',
+        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . '/json/serialize/default.php',
         [
             'version' => $version,
             'type' => $type,
diff --git a/template/versions/types/serialization/xml.php b/template/versions/types/serialization/xml.php
index bb88cb48..fa5742d9 100644
--- a/template/versions/types/serialization/xml.php
+++ b/template/versions/types/serialization/xml.php
@@ -25,7 +25,7 @@
 
 // unserialize portion
 echo require_with(
-        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . DIRECTORY_SEPARATOR . 'xml' . DIRECTORY_SEPARATOR . 'unserialize' . DIRECTORY_SEPARATOR . 'header.php',
+        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . '/xml/unserialize/header.php',
     [
         'version' => $version,
         'type' => $type,
@@ -34,7 +34,7 @@
 
 if (count($type->getAllPropertiesIndexedIterator()) > 0) :
     echo require_with(
-        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . DIRECTORY_SEPARATOR . 'xml' . DIRECTORY_SEPARATOR . 'unserialize' . DIRECTORY_SEPARATOR . 'body.php',
+        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . '/xml/unserialize/body.php',
         [
             'version' => $version,
             'type' => $type,
@@ -48,7 +48,7 @@
 <?php
 // serialize portion
 echo require_with(
-        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . DIRECTORY_SEPARATOR . 'xml' . DIRECTORY_SEPARATOR . 'serialize' . DIRECTORY_SEPARATOR . 'header.php',
+        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . '/xml/serialize/header.php',
     [
         'version' => $version,
         'type' => $type,
@@ -57,7 +57,7 @@
 
 if ($type->hasLocalProperties()) {
     echo require_with(
-        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . DIRECTORY_SEPARATOR . 'xml' . DIRECTORY_SEPARATOR . 'serialize' . DIRECTORY_SEPARATOR . 'body.php',
+        PHPFHIR_TEMPLATE_VERSION_TYPES_SERIALIZATION_DIR . '/xml/serialize/body.php',
         [
             'version' => $version,
             'type' => $type,
diff --git a/template/versions/types/serialization/xml/serialize/header.php b/template/versions/types/serialization/xml/serialize/header.php
index b0d062cb..273cb1f7 100644
--- a/template/versions/types/serialization/xml/serialize/header.php
+++ b/template/versions/types/serialization/xml/serialize/header.php
@@ -37,8 +37,11 @@
     public function xmlSerialize(null|<?php echo PHPFHIR_ENCODING_CLASSNAME_XML_WRITER; ?> $xw = null, null|<?php echo PHPFHIR_ENCODING_CLASSNAME_SERIALIZE_CONFIG; ?> $config = null): <?php echo PHPFHIR_ENCODING_CLASSNAME_XML_WRITER; ?>
 
     {
+        if (null === $config) {
+            $config = (new <?php echo PHPFHIR_VERSION_CLASSNAME_VERSION; ?>())->getConfig()->getSerializeConfig();
+        }
         if (null === $xw) {
-            $xw = new <?php echo PHPFHIR_ENCODING_CLASSNAME_XML_WRITER; ?>();
+            $xw = new <?php echo PHPFHIR_ENCODING_CLASSNAME_XML_WRITER; ?>($config);
         }
         if (!$xw->isOpen()) {
             $xw->openMemory();
@@ -47,11 +50,8 @@ public function xmlSerialize(null|<?php echo PHPFHIR_ENCODING_CLASSNAME_XML_WRIT
             $docStarted = true;
             $xw->startDocument();
         }
-        if (null === $config) {
-            $config = (new <?php echo PHPFHIR_VERSION_CLASSNAME_VERSION; ?>())->getConfig()->getSerializeConfig();
-        }
         if (!$xw->isRootOpen()) {
             $rootOpened = true;
-            $xw->openRootNode($config, '<?php echo NameUtils::getTypeXMLElementName($type); ?>', $this->_getSourceXMLNS());
+            $xw->openRootNode('<?php echo NameUtils::getTypeXMLElementName($type); ?>', $this->_getSourceXMLNS());
         }
 <?php return ob_get_clean();
\ No newline at end of file