diff --git a/src/frontend/planner_test/tests/testdata/watermark.yaml b/src/frontend/planner_test/tests/testdata/watermark.yaml
index 0d15aefde3636..f94fa39dddd30 100644
--- a/src/frontend/planner_test/tests/testdata/watermark.yaml
+++ b/src/frontend/planner_test/tests/testdata/watermark.yaml
@@ -52,26 +52,26 @@
       └─StreamAppendOnlyHashAgg { group_key: [t.ts, t.v1], aggs: [count(t.v2), count], output_watermarks: [t.ts] }
         └─StreamExchange { dist: HashShard(t.ts, t.v1) }
           └─StreamTableScan { table: t, columns: [t.ts, t.v1, t.v2, t._row_id], pk: [t._row_id], dist: UpstreamHashShard(t._row_id) }
-- name: hash join
+- name: inner window join
   sql: |
     create table t1 (ts timestamp with time zone, v1 int, v2 int, watermark for ts as ts - INTERVAL '1' SECOND) append only;
     create table t2 (ts timestamp with time zone, v1 int, v2 int, watermark for ts as ts - INTERVAL '1' SECOND) append only;
     select t1.ts as t1_ts, t2.ts as ts2, t1.v1 as t1_v1, t1.v2 as t1_v2, t2.v1 as t2_v1, t2.v2 as t2_v2 from t1, t2 where t1.ts = t2.ts;
   stream_plan: |
     StreamMaterialize { columns: [t1_ts, ts2, t1_v1, t1_v2, t2_v1, t2_v2, t1._row_id(hidden), t2._row_id(hidden)], stream_key: [t1._row_id, t2._row_id, t1_ts], pk_columns: [t1._row_id, t2._row_id, t1_ts], pk_conflict: "NoCheck", watermark_columns: [t1_ts, ts2] }
-    └─StreamAppendOnlyHashJoin { type: Inner, predicate: t1.ts = t2.ts, output_watermarks: [t1.ts, t2.ts], output: [t1.ts, t2.ts, t1.v1, t1.v2, t2.v1, t2.v2, t1._row_id, t2._row_id] }
+    └─StreamWindowJoin { type: Inner, predicate: t1.ts = t2.ts, output_watermarks: [t1.ts, t2.ts], output: [t1.ts, t2.ts, t1.v1, t1.v2, t2.v1, t2.v2, t1._row_id, t2._row_id] }
       ├─StreamExchange { dist: HashShard(t1.ts) }
       | └─StreamTableScan { table: t1, columns: [t1.ts, t1.v1, t1.v2, t1._row_id], pk: [t1._row_id], dist: UpstreamHashShard(t1._row_id) }
       └─StreamExchange { dist: HashShard(t2.ts) }
         └─StreamTableScan { table: t2, columns: [t2.ts, t2.v1, t2.v2, t2._row_id], pk: [t2._row_id], dist: UpstreamHashShard(t2._row_id) }
-- name: left semi hash join
+- name: left semi window join
   sql: |
     create table t1 (ts timestamp with time zone, v1 int, v2 int, watermark for ts as ts - INTERVAL '1' SECOND) append only;
     create table t2 (ts timestamp with time zone, v1 int, v2 int, watermark for ts as ts - INTERVAL '1' SECOND) append only;
     select t1.ts as t1_ts, t1.v1 as t1_v1, t1.v2 as t1_v2 from t1 where exists (select * from t2 where t1.ts = t2.ts);
   stream_plan: |
     StreamMaterialize { columns: [t1_ts, t1_v1, t1_v2, t1._row_id(hidden)], stream_key: [t1._row_id, t1_ts], pk_columns: [t1._row_id, t1_ts], pk_conflict: "NoCheck", watermark_columns: [t1_ts] }
-    └─StreamHashJoin { type: LeftSemi, predicate: t1.ts = t2.ts, output_watermarks: [t1.ts], output: all }
+    └─StreamWindowJoin { type: LeftSemi, predicate: t1.ts = t2.ts, output_watermarks: [t1.ts], output: all }
       ├─StreamExchange { dist: HashShard(t1.ts) }
       | └─StreamTableScan { table: t1, columns: [t1.ts, t1.v1, t1.v2, t1._row_id], pk: [t1._row_id], dist: UpstreamHashShard(t1._row_id) }
       └─StreamExchange { dist: HashShard(t2.ts) }
diff --git a/src/frontend/src/optimizer/plan_node/stream_hash_join.rs b/src/frontend/src/optimizer/plan_node/stream_hash_join.rs
index 866d9fe8e87b1..db191c34cee77 100644
--- a/src/frontend/src/optimizer/plan_node/stream_hash_join.rs
+++ b/src/frontend/src/optimizer/plan_node/stream_hash_join.rs
@@ -283,7 +283,18 @@ impl StreamHashJoin {
 
 impl fmt::Display for StreamHashJoin {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let mut builder = if self.clean_left_state_conjunction_idx.is_some()
+        let (ljk, rjk) = self
+            .eq_join_predicate
+            .eq_indexes()
+            .first()
+            .cloned()
+            .expect("first join key");
+
+        let mut builder = if self.left().watermark_columns().contains(ljk)
+            && self.right().watermark_columns().contains(rjk)
+        {
+            f.debug_struct("StreamWindowJoin")
+        } else if self.clean_left_state_conjunction_idx.is_some()
             && self.clean_right_state_conjunction_idx.is_some()
         {
             f.debug_struct("StreamIntervalJoin")