diff --git a/flint-spark-integration/src/main/scala/org/opensearch/flint/app/FlintInstance.scala b/flint-spark-integration/src/main/scala/org/opensearch/flint/app/FlintInstance.scala
index aa417e61a..f9e8dd693 100644
--- a/flint-spark-integration/src/main/scala/org/opensearch/flint/app/FlintInstance.scala
+++ b/flint-spark-integration/src/main/scala/org/opensearch/flint/app/FlintInstance.scala
@@ -120,7 +120,12 @@ object FlintInstance {
         "state" -> job.state,
         // update last update time
         "lastUpdateTime" -> currentTime,
-        "excludeJobIds" -> job.excludedJobIds,
+        // Convert a Seq[String] into a comma-separated string, such as "id1,id2".
+        // This approach is chosen over serializing to an array format (e.g., ["id1", "id2"])
+        // because it simplifies client-side processing. With a comma-separated string,
+        // clients can easily ignore this field if it's not in use, avoiding the need
+        // for array parsing logic. This makes the serialized data more straightforward to handle.
+        "excludeJobIds" -> job.excludedJobIds.mkString(","),
         "jobStartTime" -> job.jobStartTime))
   }
 }
diff --git a/flint-spark-integration/src/test/scala/org/opensearch/flint/app/FlintInstanceTest.scala b/flint-spark-integration/src/test/scala/org/opensearch/flint/app/FlintInstanceTest.scala
index caf5a84d4..12c2ae5bc 100644
--- a/flint-spark-integration/src/test/scala/org/opensearch/flint/app/FlintInstanceTest.scala
+++ b/flint-spark-integration/src/test/scala/org/opensearch/flint/app/FlintInstanceTest.scala
@@ -46,7 +46,9 @@ class FlintInstanceTest extends SparkFunSuite with Matchers {
     json should include(""""sessionId":"session-789"""")
     json should include(""""state":"RUNNING"""")
     json should include(s""""lastUpdateTime":$currentTime""")
-    json should include(""""excludeJobIds":["job-101","job-202"]""")
+    json should include(
+      """"excludeJobIds":"job-101,job-202""""
+    ) // Check for comma-separated string
     json should include(""""jobStartTime":1620000001000""")
     json should include(""""error":""""")
   }