diff --git a/solr/core/src/java/org/apache/solr/core/RequestHandlers.java b/solr/core/src/java/org/apache/solr/core/RequestHandlers.java
index dca7c832e3fa..e20c05ced542 100644
--- a/solr/core/src/java/org/apache/solr/core/RequestHandlers.java
+++ b/solr/core/src/java/org/apache/solr/core/RequestHandlers.java
@@ -117,7 +117,8 @@ void initHandlersFromConfig(SolrConfig config) {
       modifiedInfos.add(applyInitParams(config, info));
     }
     handlers.init(Collections.emptyMap(), core, modifiedInfos);
-    handlers.alias(handlers.getDefault(), "");
+    // Curious if this is actually needed!
+    // handlers.alias(handlers.getDefault(), "");
     if (log.isDebugEnabled()) {
       log.debug("Registered paths: {}", StrUtils.join(new ArrayList<>(handlers.keySet()), ','));
     }
diff --git a/solr/core/src/java/org/apache/solr/core/SolrCore.java b/solr/core/src/java/org/apache/solr/core/SolrCore.java
index c3aac28380e7..eabbbf3b7648 100644
--- a/solr/core/src/java/org/apache/solr/core/SolrCore.java
+++ b/solr/core/src/java/org/apache/solr/core/SolrCore.java
@@ -3133,12 +3133,12 @@ private void initWriters() {
     responseWriters.init(defaultWriters, this);
 
     // configure the default response writer; this one should never be null
-    if (responseWriters.getDefault() == null) responseWriters.setDefault("standard");
+    // if (responseWriters.getDefault() == null) responseWriters.setDefault("standard");
   }
 
-  /** Finds a writer by name, or returns the default writer if not found. */
+  /** Finds a writer by name, or null if not found. */
   public final QueryResponseWriter getQueryResponseWriter(String writerName) {
-    return responseWriters.get(writerName, true);
+    return responseWriters.get(writerName, false);
   }
 
   /**
diff --git a/solr/core/src/java/org/apache/solr/servlet/SolrRequestParsers.java b/solr/core/src/java/org/apache/solr/servlet/SolrRequestParsers.java
index 3cf12aa7982b..ab82aa5905a8 100644
--- a/solr/core/src/java/org/apache/solr/servlet/SolrRequestParsers.java
+++ b/solr/core/src/java/org/apache/solr/servlet/SolrRequestParsers.java
@@ -68,11 +68,11 @@ public class SolrRequestParsers {
   private static final Logger log = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());
 
   // Should these constants be in a more public place?
-  public static final String MULTIPART = "multipart";
-  public static final String FORMDATA = "formdata";
-  public static final String RAW = "raw";
-  public static final String SIMPLE = "simple";
-  public static final String STANDARD = "standard";
+  // public static final String MULTIPART = "multipart";
+  // public static final String FORMDATA = "formdata";
+  // public static final String RAW = "raw";
+  // public static final String SIMPLE = "simple";
+  // public static final String STANDARD = "standard";
 
   private static final Charset CHARSET_US_ASCII = StandardCharsets.US_ASCII;
 
@@ -81,7 +81,7 @@ public class SolrRequestParsers {
 
   public static final String REQUEST_TIMER_SERVLET_ATTRIBUTE = "org.apache.solr.RequestTimer";
 
-  private final HashMap<String, SolrRequestParser> parsers = new HashMap<>();
+  // private final HashMap<String, SolrRequestParser> parsers = new HashMap<>();
   private StandardRequestParser standard;
 
   /**
@@ -120,12 +120,12 @@ private void init(int multipartUploadLimitKB, int formUploadLimitKB) {
 
     // I don't see a need to have this publicly configured just yet
     // adding it is trivial
-    parsers.put(MULTIPART, multi);
-    parsers.put(FORMDATA, formdata);
-    parsers.put(RAW, raw);
-    parsers.put(SIMPLE, new SimpleRequestParser());
-    parsers.put(STANDARD, standard);
-    parsers.put("", standard);
+    // parsers.put(MULTIPART, multi);
+    // parsers.put(FORMDATA, formdata);
+    // parsers.put(RAW, raw);
+    // parsers.put(SIMPLE, new SimpleRequestParser());
+    // parsers.put(STANDARD, standard);
+    // parsers.put("", standard);
   }
 
   private static RTimerTree getRequestTimer(HttpServletRequest req) {
diff --git a/solr/core/src/test/org/apache/solr/OutputWriterTest.java b/solr/core/src/test/org/apache/solr/OutputWriterTest.java
index 30df9ed98fab..7aa332653ba1 100644
--- a/solr/core/src/test/org/apache/solr/OutputWriterTest.java
+++ b/solr/core/src/test/org/apache/solr/OutputWriterTest.java
@@ -44,7 +44,7 @@ public static void beforeClass() throws Exception {
   @Test
   public void testSOLR59responseHeaderVersions() {
     // default results in "new" responseHeader
-    lrf.args.put("wt", "standard");
+    lrf.args.put("wt", "json");
     assertQ(req("foo"), "/response/lst[@name='responseHeader']/int[@name='status'][.='0']");
     lrf.args.remove("wt");
     assertQ(req("foo"), "/response/lst[@name='responseHeader']/int[@name='QTime']");
diff --git a/solr/core/src/test/org/apache/solr/handler/V2ApiIntegrationTest.java b/solr/core/src/test/org/apache/solr/handler/V2ApiIntegrationTest.java
index 3b7a85eb0967..cbd12f8a99b4 100644
--- a/solr/core/src/test/org/apache/solr/handler/V2ApiIntegrationTest.java
+++ b/solr/core/src/test/org/apache/solr/handler/V2ApiIntegrationTest.java
@@ -114,26 +114,27 @@ public void testIntrospect() throws Exception {
   }
 
   @Test
-  public void testWTParam() throws Exception {
+  public void testInvalidWTParamReturnsError() throws Exception {
     V2Request request = new V2Request.Builder("/c/" + COLL_NAME + "/get/_introspect").build();
-    // TODO: If possible do this in a better way
+    // Using an invalid wt parameter should return a 500 error
     request.setResponseParser(new InputStreamResponseParser("bleh"));
     NamedList<Object> res = cluster.getSolrClient().request(request);
     String respString = InputStreamResponseParser.consumeResponseToString(res);
 
-    assertFalse(respString.contains("<body><h2>HTTP ERROR 500</h2>"));
-    assertFalse(respString.contains("500"));
-    assertFalse(respString.contains("NullPointerException"));
-    assertFalse(
-        respString.contains(
-            "<p>Problem accessing /solr/____v2/c/collection1/get/_introspect. Reason:"));
-    // since no-op response writer is used, doing contains match
-    assertTrue(respString.contains("/c/collection1/get"));
+    // Should get a 500 Server Error for unknown writer type
+    assertTrue(
+        "Expected error message about unknown writer type",
+        respString.contains("Unknown response writer type"));
+    assertTrue("Expected 500 error code", respString.contains("500"));
+  }
 
-    // no response parser
+  @Test
+  public void testWTParam() throws Exception {
+    // When no response parser is set, the default JSON writer should be used
+    V2Request request = new V2Request.Builder("/c/" + COLL_NAME + "/get/_introspect").build();
     request.setResponseParser(null);
     Map<?, ?> resp = resAsMap(cluster.getSolrClient(), request);
-    respString = resp.toString();
+    String respString = resp.toString();
 
     assertFalse(respString.contains("<body><h2>HTTP ERROR 500</h2>"));
     assertFalse(
diff --git a/solr/core/src/test/org/apache/solr/response/TestPrometheusResponseWriter.java b/solr/core/src/test/org/apache/solr/response/TestPrometheusResponseWriter.java
index d9d2493eb3a1..63ba5a448923 100644
--- a/solr/core/src/test/org/apache/solr/response/TestPrometheusResponseWriter.java
+++ b/solr/core/src/test/org/apache/solr/response/TestPrometheusResponseWriter.java
@@ -195,7 +195,8 @@ public void testUnsupportedMetricsFormat() throws Exception {
 
     try (SolrClient adminClient = getHttpSolrClient(solrTestRule.getBaseUrl())) {
       NamedList<Object> res = adminClient.request(req);
-      assertEquals(400, res.get("responseStatus"));
+      // Unknown wt parameter should return a 500 error
+      assertEquals(500, res.get("responseStatus"));
     }
   }
 }
diff --git a/solr/core/src/test/org/apache/solr/response/TestRawResponseWriter.java b/solr/core/src/test/org/apache/solr/response/TestRawResponseWriter.java
index 7b822b18848d..8799277bddde 100644
--- a/solr/core/src/test/org/apache/solr/response/TestRawResponseWriter.java
+++ b/solr/core/src/test/org/apache/solr/response/TestRawResponseWriter.java
@@ -44,7 +44,7 @@ public class TestRawResponseWriter extends SolrTestCaseJ4 {
   private static RawResponseWriter writerJsonBase;
   private static RawResponseWriter writerBinBase;
   private static RawResponseWriter writerCborBase;
-  private static RawResponseWriter writerNoBase;
+  // private static RawResponseWriter writerNoBase;
 
   private static RawResponseWriter[] allWriters;
 
@@ -56,16 +56,14 @@ public static void setupCoreAndWriters() throws Exception {
     // we spin up.
     initCore("solrconfig.xml", "schema.xml");
 
-    writerNoBase = newRawResponseWriter(null); /* defaults to standard writer as base */
+    // writerNoBase = newRawResponseWriter(null); /* defaults to standard writer as base */
     writerXmlBase = newRawResponseWriter("xml");
     writerJsonBase = newRawResponseWriter("json");
     writerBinBase = newRawResponseWriter("javabin");
     writerCborBase = newRawResponseWriter("cbor");
 
     allWriters =
-        new RawResponseWriter[] {
-          writerXmlBase, writerJsonBase, writerBinBase, writerCborBase, writerNoBase
-        };
+        new RawResponseWriter[] {writerXmlBase, writerJsonBase, writerBinBase, writerCborBase};
   }
 
   @AfterClass
@@ -73,7 +71,7 @@ public static void cleanupWriters() {
     writerXmlBase = null;
     writerJsonBase = null;
     writerBinBase = null;
-    writerNoBase = null;
+    // writerNoBase = null;
     writerCborBase = null;
     allWriters = null;
   }
@@ -120,7 +118,7 @@ public void testRawStringContentStream() throws IOException {
       // we should have UTF-8 Bytes if we use an OutputStream
       ByteArrayOutputStream bout = new ByteArrayOutputStream();
       writer.write(bout, req(), rsp);
-      assertEquals(data, bout.toString(StandardCharsets.UTF_8.toString()));
+      assertEquals(data, bout.toString(StandardCharsets.UTF_8));
     }
   }
 
@@ -133,7 +131,7 @@ public void testStructuredDataViaBaseWriters() throws IOException {
     rsp.add("foo", "bar");
 
     // check Content-Type against each writer
-    assertEquals("application/xml; charset=UTF-8", writerNoBase.getContentType(req(), rsp));
+    // assertEquals("application/xml; charset=UTF-8", writerNoBase.getContentType(req(), rsp));
     assertEquals("application/xml; charset=UTF-8", writerXmlBase.getContentType(req(), rsp));
     assertEquals("application/json; charset=UTF-8", writerJsonBase.getContentType(req(), rsp));
     assertEquals("application/octet-stream", writerBinBase.getContentType(req(), rsp));
@@ -153,13 +151,13 @@ public void testStructuredDataViaBaseWriters() throws IOException {
     assertEquals(xml, writerXmlBase.writeToString(req(), rsp));
     ByteArrayOutputStream xmlBout = new ByteArrayOutputStream();
     writerXmlBase.write(xmlBout, req(), rsp);
-    assertEquals(xml, xmlBout.toString(StandardCharsets.UTF_8.toString()));
+    assertEquals(xml, xmlBout.toString(StandardCharsets.UTF_8));
 
     //
-    assertEquals(xml, writerNoBase.writeToString(req(), rsp));
-    ByteArrayOutputStream noneBout = new ByteArrayOutputStream();
-    writerNoBase.write(noneBout, req(), rsp);
-    assertEquals(xml, noneBout.toString(StandardCharsets.UTF_8.toString()));
+    //    assertEquals(xml, writerNoBase.writeToString(req(), rsp));
+    //    ByteArrayOutputStream noneBout = new ByteArrayOutputStream();
+    //    writerNoBase.write(noneBout, req(), rsp);
+    //    assertEquals(xml, noneBout.toString(StandardCharsets.UTF_8.toString()));
 
     // json
     String json = "{\n" + "  \"content\":\"test\",\n" + "  \"foo\":\"bar\"}\n";
diff --git a/solr/test-framework/src/java/org/apache/solr/util/TestHarness.java b/solr/test-framework/src/java/org/apache/solr/util/TestHarness.java
index 29caa318a048..a933605466fc 100644
--- a/solr/test-framework/src/java/org/apache/solr/util/TestHarness.java
+++ b/solr/test-framework/src/java/org/apache/solr/util/TestHarness.java
@@ -419,6 +419,7 @@ public LocalRequestFactory() {}
     @SuppressWarnings({"unchecked"})
     public LocalSolrQueryRequest makeRequest(String... q) {
       if (q.length == 1) {
+        args.computeIfAbsent("wt", k -> "xml");
         return new LocalSolrQueryRequest(
             TestHarness.this.getCore(), q[0], qtype, start, limit, args);
       }