Skip redirect set lookup for non-3xx responses

client/src/main/java/org/asynchttpclient/netty/handler/intercept/Interceptors.java

@@ -125,7 +125,7 @@ public boolean exitAfterIntercept(Channel channel, NettyResponseFuture<?> future
             return continue100Interceptor.exitAfterHandling100(channel, future);
         }
 
-        if (Redirect30xInterceptor.REDIRECT_STATUSES.contains(statusCode)) {
+        if (Redirect30xInterceptor.isRedirect(statusCode)) {
             return redirect30xInterceptor.exitAfterHandlingRedirect(channel, future, response, request, statusCode, realm);
         }
 

client/src/main/java/org/asynchttpclient/netty/handler/intercept/Redirect30xInterceptor.java

@@ -18,6 +18,7 @@
 import io.netty.channel.Channel;
 import io.netty.handler.codec.http.HttpHeaders;
 import io.netty.handler.codec.http.HttpResponse;
+import io.netty.handler.codec.http.HttpStatusClass;
 import io.netty.handler.codec.http.HttpUtil;
 import io.netty.handler.codec.http.cookie.Cookie;
 import org.asynchttpclient.AsyncHttpClientConfig;
@@ -70,6 +71,16 @@ public class Redirect30xInterceptor {
         REDIRECT_STATUSES.add(PERMANENT_REDIRECT_308);
     }
 
+    /**
+     * Whether {@code statusCode} is a redirect this interceptor follows. Only a 3xx can be, and the class
+     * check takes an {@code int}, so it keeps the {@link #REDIRECT_STATUSES} lookup, which boxes, off the
+     * responses that make up almost all traffic. The set is still consulted rather than inlined here because
+     * it is public and mutable, so an extra 3xx status a caller registered stays honoured.
+     */
+    static boolean isRedirect(int statusCode) {
+        return HttpStatusClass.REDIRECTION.contains(statusCode) && REDIRECT_STATUSES.contains(statusCode);
+    }
+
     private final ChannelManager channelManager;
     private final AsyncHttpClientConfig config;
     private final NettyRequestSender requestSender;

client/src/test/java/org/asynchttpclient/netty/handler/intercept/Redirect30xInterceptorTest.java

@@ -0,0 +1,52 @@
+/*
+ *    Copyright (c) 2026 AsyncHttpClient Project. All rights reserved.
+ *
+ *    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.
+ */
+package org.asynchttpclient.netty.handler.intercept;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * Tests {@link Redirect30xInterceptor#isRedirect(int)}: the 3xx class check and the
+ * {@link Redirect30xInterceptor#REDIRECT_STATUSES} membership must agree, so a 3xx that is not a followed
+ * redirect is rejected just like a non-3xx status.
+ */
+public class Redirect30xInterceptorTest {
+
+    @Test
+    public void acceptsTheFollowedRedirectStatuses() {
+        for (int statusCode : new int[]{301, 302, 303, 307, 308}) {
+            assertTrue(Redirect30xInterceptor.isRedirect(statusCode), statusCode + " should be a redirect");
+        }
+    }
+
+    @Test
+    public void rejects3xxStatusesThatAreNotFollowed() {
+        // in the 3xx class, but not redirects this interceptor acts on: 304 in particular must fall through
+        // to the normal response path rather than be treated as a redirect
+        for (int statusCode : new int[]{300, 304, 305, 306, 399}) {
+            assertFalse(Redirect30xInterceptor.isRedirect(statusCode), statusCode + " should not be a redirect");
+        }
+    }
+
+    @Test
+    public void rejectsStatusesOutsideThe3xxClass() {
+        for (int statusCode : new int[]{100, 200, 204, 299, 400, 404, 500}) {
+            assertFalse(Redirect30xInterceptor.isRedirect(statusCode), statusCode + " should not be a redirect");
+        }
+    }
+}