diff --git a/project/MimaExcludes.scala b/project/MimaExcludes.scala
index 09fc88de493da..1a3936195f9bf 100644
--- a/project/MimaExcludes.scala
+++ b/project/MimaExcludes.scala
@@ -269,7 +269,7 @@ object MimaExcludes {
     ProblemFilters.exclude[Problem]("org.apache.spark.sql.protobuf.utils.SchemaConverters.*"),
 
     // SPARK-51267: Match local Spark Connect server logic between Python and Scala
-    ProblemFilters.exclude[MissingFieldProblem]("org.apache.spark.launcher.SparkLauncher.SPARK_LOCAL_REMOTE")
+    ProblemFilters.exclude[MissingFieldProblem]("org.apache.spark.launcher.SparkLauncher.SPARK_LOCAL_REMOTE"),
 
     (problem: Problem) => problem match {
       case MissingClassProblem(cls) => !cls.fullName.startsWith("org.sparkproject.jpmml") &&
diff --git a/sql/connect/common/src/main/scala/org/apache/spark/sql/connect/SparkSession.scala b/sql/connect/common/src/main/scala/org/apache/spark/sql/connect/SparkSession.scala
index bee90c77f348d..a64f29f6583b7 100644
--- a/sql/connect/common/src/main/scala/org/apache/spark/sql/connect/SparkSession.scala
+++ b/sql/connect/common/src/main/scala/org/apache/spark/sql/connect/SparkSession.scala
@@ -696,9 +696,7 @@ object SparkSession extends SparkSessionCompanion with Logging {
     Option(System.getenv("SPARK_HOME")).map(Paths.get(_, "sbin", "stop-connect-server.sh"))
   private[sql] val sparkOptions = sys.props.filter { p =>
     p._1.startsWith("spark.") && p._2.nonEmpty
-  }.toMap ++ Map(
-    "spark.sql.artifact.isolation.enabled" -> "true",
-    "spark.sql.artifact.isolation.alwaysApplyClassloader" -> "true")
+  }.toMap
 
   private val sessions = CacheBuilder
     .newBuilder()
@@ -712,60 +710,62 @@ object SparkSession extends SparkSessionCompanion with Logging {
    * Create a new Spark Connect server to connect locally.
    */
   private[sql] def withLocalConnectServer[T](f: => T): T = {
-    synchronized {
-      lazy val isAPIModeConnect =
-        Option(System.getProperty(org.apache.spark.sql.SparkSessionBuilder.API_MODE_KEY))
-          .getOrElse("classic")
-          .toLowerCase(Locale.ROOT) == "connect"
-      val remoteString = sparkOptions
-        .get("spark.remote")
-        .orElse(Option(System.getProperty("spark.remote"))) // Set from Spark Submit
-        .orElse(sys.env.get(SparkConnectClient.SPARK_REMOTE))
-        .orElse {
-          if (isAPIModeConnect) {
-            sparkOptions.get("spark.master").orElse(sys.env.get("MASTER"))
-          } else {
-            None
-          }
+    lazy val isAPIModeConnect =
+      Option(System.getProperty(org.apache.spark.sql.SparkSessionBuilder.API_MODE_KEY))
+        .getOrElse("classic")
+        .toLowerCase(Locale.ROOT) == "connect"
+    val remoteString = sparkOptions
+      .get("spark.remote")
+      .orElse(Option(System.getProperty("spark.remote"))) // Set from Spark Submit
+      .orElse(sys.env.get(SparkConnectClient.SPARK_REMOTE))
+      .orElse {
+        if (isAPIModeConnect) {
+          sparkOptions.get("spark.master").orElse(sys.env.get("MASTER"))
+        } else {
+          None
         }
+      }
 
-      server.synchronized {
-        if (server.isEmpty &&
-          (remoteString.exists(_.startsWith("local")) ||
-            (remoteString.isDefined && isAPIModeConnect)) &&
-          maybeConnectStartScript.exists(Files.exists(_))) {
-          server = Some {
-            val args =
-              Seq(
-                maybeConnectStartScript.get.toString,
-                "--master",
-                remoteString.get) ++ sparkOptions
-                .filter(p => !p._1.startsWith("spark.remote"))
-                .filter(p => !p._1.startsWith("spark.api.mode"))
-                .flatMap { case (k, v) => Seq("--conf", s"$k=$v") }
-            val pb = new ProcessBuilder(args: _*)
-            // So don't exclude spark-sql jar in classpath
-            pb.environment().remove(SparkConnectClient.SPARK_REMOTE)
-            pb.environment().put("SPARK_LOCAL_CONNECT", "1")
-            pb.start()
-          }
+    server.synchronized {
+      if (server.isEmpty &&
+        (remoteString.exists(_.startsWith("local")) ||
+          (remoteString.isDefined && isAPIModeConnect)) &&
+        maybeConnectStartScript.exists(Files.exists(_))) {
+        server = Some {
+          val args =
+            Seq(
+              maybeConnectStartScript.get.toString,
+              "--master",
+              remoteString.get) ++ (sparkOptions ++ Map(
+              "spark.sql.artifact.isolation.enabled" -> "true",
+              "spark.sql.artifact.isolation.alwaysApplyClassloader" -> "true"))
+              .filter(p => !p._1.startsWith("spark.remote"))
+              .filter(p => !p._1.startsWith("spark.api.mode"))
+              .flatMap { case (k, v) => Seq("--conf", s"$k=$v") }
+          val pb = new ProcessBuilder(args: _*)
+          // So don't exclude spark-sql jar in classpath
+          pb.environment().remove(SparkConnectClient.SPARK_REMOTE)
+          pb.start()
+        }
 
-          // Let the server start. We will directly request to set the configurations
-          // and this sleep makes less noisy with retries.
-          Thread.sleep(2000L)
-          System.setProperty("spark.remote", "sc://localhost")
+        // Let the server start. We will directly request to set the configurations
+        // and this sleep makes less noisy with retries.
+        Thread.sleep(2000L)
+        System.setProperty("spark.remote", "sc://localhost")
 
-          // scalastyle:off runtimeaddshutdownhook
-          Runtime.getRuntime.addShutdownHook(new Thread() {
-            override def run(): Unit = if (server.isDefined) {
+        // scalastyle:off runtimeaddshutdownhook
+        Runtime.getRuntime.addShutdownHook(new Thread() {
+          override def run(): Unit = server.synchronized {
+            if (server.isDefined) {
               new ProcessBuilder(maybeConnectStopScript.get.toString)
                 .start()
             }
-          })
-          // scalastyle:on runtimeaddshutdownhook
-        }
+          }
+        })
+        // scalastyle:on runtimeaddshutdownhook
       }
     }
+
     f
   }