diff --git a/src/query/service/src/interpreters/hook/compact_hook.rs b/src/query/service/src/interpreters/hook/compact_hook.rs
index 26f68d3f49313..4a95619d95c58 100644
--- a/src/query/service/src/interpreters/hook/compact_hook.rs
+++ b/src/query/service/src/interpreters/hook/compact_hook.rs
@@ -100,7 +100,7 @@ async fn do_hook_compact(
                         return Ok(());
                     }
                     CompactionLimits {
-                        segment_limit: None,
+                        segment_limit: Some(compaction_num_block_hint as usize),
                         block_limit: Some(compaction_num_block_hint as usize),
                     }
                 }
diff --git a/src/query/storages/fuse/src/operations/mutation/mutator/block_compact_mutator.rs b/src/query/storages/fuse/src/operations/mutation/mutator/block_compact_mutator.rs
index 769140540786a..8bf86b8caa143 100644
--- a/src/query/storages/fuse/src/operations/mutation/mutator/block_compact_mutator.rs
+++ b/src/query/storages/fuse/src/operations/mutation/mutator/block_compact_mutator.rs
@@ -311,6 +311,7 @@ pub struct SegmentCompactChecker {
 
     compacted_segment_cnt: usize,
     compacted_block_cnt: u64,
+    compacted_perfect_block_cnt: u64,
 }
 
 impl SegmentCompactChecker {
@@ -320,8 +321,9 @@ impl SegmentCompactChecker {
             total_block_count: 0,
             thresholds,
             cluster_key_id,
-            compacted_block_cnt: 0,
             compacted_segment_cnt: 0,
+            compacted_block_cnt: 0,
+            compacted_perfect_block_cnt: 0,
         }
     }
 
@@ -360,10 +362,13 @@ impl SegmentCompactChecker {
         }
 
         self.compacted_segment_cnt += segments.len();
-        self.compacted_block_cnt += segments
+        (self.compacted_block_cnt, self.compacted_perfect_block_cnt) = segments
             .iter()
-            .map(|(_, info)| info.summary.block_count)
-            .sum::<u64>();
+            .map(|(_, info)| (info.summary.block_count, info.summary.perfect_block_count))
+            .fold(
+                (self.compacted_block_cnt, self.compacted_perfect_block_cnt),
+                |(b_sum, p_sum), (b, p)| (b_sum + b, p_sum + p),
+            );
         true
     }
 
@@ -415,15 +420,29 @@ impl SegmentCompactChecker {
         self.generate_part(final_segments, parts);
     }
 
+    /// Check if compaction limit is reached.
     pub fn is_limit_reached(&self, num_segment_limit: usize, num_block_limit: usize) -> bool {
-        let residual_segment_cnt = self.segments.len();
-        let residual_block_cnt: u64 = self
+        let (compacted_block_cnt, compacted_perfect_block_cnt) = self
             .segments
             .iter()
-            .map(|(_, info)| info.summary.block_count)
-            .sum();
-        self.compacted_segment_cnt + residual_segment_cnt >= num_segment_limit
-            || self.compacted_block_cnt + residual_block_cnt >= num_block_limit as u64
+            .map(|(_, info)| (info.summary.block_count, info.summary.perfect_block_count))
+            .fold(
+                (self.compacted_block_cnt, self.compacted_perfect_block_cnt),
+                |(b_sum, p_sum), (b, p)| (b_sum + b, p_sum + p),
+            );
+        let compacted_imperfect_block_cnt = compacted_block_cnt - compacted_perfect_block_cnt;
+        // When the total number of *imperfect blocks* reaches (num_block_limit - 1)
+        // and total selected blocks reach num_block_limit, we trigger compaction.
+        //
+        // Because `compact_num_block_hint` was intentionally increased by +1 during its calculation,
+        // to slightly expand the compaction range and include previously un-compacted segments.
+        if compacted_imperfect_block_cnt >= num_block_limit.saturating_sub(1) as u64
+            && compacted_block_cnt >= num_block_limit as u64
+        {
+            return true;
+        }
+
+        self.compacted_segment_cnt + self.segments.len() >= num_segment_limit
     }
 }
 
diff --git a/tests/sqllogictests/suites/base/09_fuse_engine/09_0041_auto_compaction.test b/tests/sqllogictests/suites/base/09_fuse_engine/09_0041_auto_compaction.test
index 51dfb9e866df6..7c9404369b6e0 100644
--- a/tests/sqllogictests/suites/base/09_fuse_engine/09_0041_auto_compaction.test
+++ b/tests/sqllogictests/suites/base/09_fuse_engine/09_0041_auto_compaction.test
@@ -108,3 +108,35 @@ select info:average_depth from clustering_information('i15760', 't1')
 
 statement ok
 drop table t1 all;
+
+#ISSUE 18859
+statement ok
+create table t2(a int) row_per_block=5;
+
+statement ok
+insert into t2 select number from numbers(2);
+
+statement ok
+insert into t2 select number from numbers(12);
+
+statement ok
+insert into t2 select number from numbers(2);
+
+query T
+select block_count, row_count from fuse_segment('i15760', 't2');
+----
+1 2
+2 12
+1 2
+
+statement ok
+insert into t2 select number from numbers(2);
+
+# after auto compaction
+query T
+select block_count, row_count from fuse_segment('i15760', 't2');
+----
+3 18
+
+statement ok
+drop table t2 all;