diff --git a/MCPForUnity/Editor/Helpers/CodexConfigHelper.cs b/MCPForUnity/Editor/Helpers/CodexConfigHelper.cs
index 45ae5a39e..4ed1b8811 100644
--- a/MCPForUnity/Editor/Helpers/CodexConfigHelper.cs
+++ b/MCPForUnity/Editor/Helpers/CodexConfigHelper.cs
@@ -36,7 +36,7 @@ public static string BuildCodexServerBlock(string uvPath)
             if (useHttpTransport)
             {
                 // HTTP mode: Use url field
-                string httpUrl = HttpEndpointUtility.GetMcpRpcUrl();
+                string httpUrl = GetCodexHttpUrl();
                 unityMCP["url"] = new TomlString { Value = httpUrl };
 
                 // Enable Codex's Rust MCP client for HTTP/SSE transport
@@ -191,7 +191,7 @@ private static TomlTable CreateUnityMcpTable(string uvPath)
             if (useHttpTransport)
             {
                 // HTTP mode: Use url field
-                string httpUrl = HttpEndpointUtility.GetMcpRpcUrl();
+                string httpUrl = GetCodexHttpUrl();
                 unityMCP["url"] = new TomlString { Value = httpUrl };
             }
             else
@@ -229,6 +229,17 @@ private static TomlTable CreateUnityMcpTable(string uvPath)
             return unityMCP;
         }
 
+        private static string GetCodexHttpUrl()
+        {
+            // Codex has intermittently failed the MCP handshake when configured with hostname-based
+            // loopback URLs such as localhost/::1, even though Unity MCP itself is reachable.
+            // Keep normalizing loopback hosts to 127.0.0.1 for Codex until the client routes them
+            // reliably again. If Codex fixes that behavior in the future, this is the workaround
+            // to revisit or remove before changing shared endpoint generation.
+            return HttpEndpointUtility.GetMcpRpcUrl()
+                .Replace("http://localhost:", "http://127.0.0.1:");
+        }
+
         /// <summary>
         /// Ensures the features table contains the rmcp_client flag for HTTP/SSE transport.
         /// </summary>