diff --git a/s3stream/src/main/java/com/automq/stream/s3/compact/operator/DataBlockWriter.java b/s3stream/src/main/java/com/automq/stream/s3/compact/operator/DataBlockWriter.java
index 60477bb82..7621d7536 100644
--- a/s3stream/src/main/java/com/automq/stream/s3/compact/operator/DataBlockWriter.java
+++ b/s3stream/src/main/java/com/automq/stream/s3/compact/operator/DataBlockWriter.java
@@ -88,6 +88,7 @@ public void copyWrite(List<StreamDataBlock> dataBlock) {
 
     public CompletableFuture<Void> forceUpload() {
         uploadWaitingList();
+        writer.copyOnWrite();
         return CompletableFuture.allOf(waitingUploadBlockCfs.values().toArray(new CompletableFuture[0]));
     }
 
diff --git a/s3stream/src/main/java/com/automq/stream/s3/operator/MemoryS3Operator.java b/s3stream/src/main/java/com/automq/stream/s3/operator/MemoryS3Operator.java
index db514773e..0a42d1ef8 100644
--- a/s3stream/src/main/java/com/automq/stream/s3/operator/MemoryS3Operator.java
+++ b/s3stream/src/main/java/com/automq/stream/s3/operator/MemoryS3Operator.java
@@ -66,6 +66,11 @@ public CompletableFuture<Void> write(ByteBuf part) {
                 return CompletableFuture.completedFuture(null);
             }
 
+            @Override
+            public void copyOnWrite() {
+
+            }
+
             @Override
             public boolean hasBatchingPart() {
                 return false;
diff --git a/s3stream/src/main/java/com/automq/stream/s3/operator/MultiPartWriter.java b/s3stream/src/main/java/com/automq/stream/s3/operator/MultiPartWriter.java
index eda8db035..0091973ce 100644
--- a/s3stream/src/main/java/com/automq/stream/s3/operator/MultiPartWriter.java
+++ b/s3stream/src/main/java/com/automq/stream/s3/operator/MultiPartWriter.java
@@ -88,6 +88,13 @@ public CompletableFuture<Void> write(ByteBuf data) {
         return objectPart.getFuture();
     }
 
+    @Override
+    public void copyOnWrite() {
+        if (objectPart != null) {
+            objectPart.copyOnWrite();
+        }
+    }
+
     @Override
     public boolean hasBatchingPart() {
         return objectPart != null;
@@ -157,7 +164,7 @@ private List<CompletedPart> genCompleteParts() {
 
     class ObjectPart {
         private final int partNumber = nextPartNumber.getAndIncrement();
-        private final CompositeByteBuf partBuf = DirectByteBufAlloc.compositeByteBuffer();
+        private CompositeByteBuf partBuf = DirectByteBufAlloc.compositeByteBuffer();
         private CompletableFuture<Void> lastRangeReadCf = CompletableFuture.completedFuture(null);
         private final CompletableFuture<CompletedPart> partCf = new CompletableFuture<>();
         private long size;
@@ -174,6 +181,17 @@ public void write(ByteBuf data) {
             this.lastRangeReadCf = lastRangeReadCf.thenAccept(nil -> partBuf.addComponent(true, data));
         }
 
+        public void copyOnWrite() {
+            int size = partBuf.readableBytes();
+            if (size > 0) {
+                ByteBuf buf = DirectByteBufAlloc.byteBuffer(size);
+                buf.writeBytes(partBuf.duplicate());
+                CompositeByteBuf copy = DirectByteBufAlloc.compositeByteBuffer().addComponent(true, buf);
+                this.partBuf.release();
+                this.partBuf = copy;
+            }
+        }
+
         public void readAndWrite(String sourcePath, long start, long end) {
             size += end - start;
             // TODO: parallel read and sequence add.
diff --git a/s3stream/src/main/java/com/automq/stream/s3/operator/ProxyWriter.java b/s3stream/src/main/java/com/automq/stream/s3/operator/ProxyWriter.java
index b58413ab1..89ca78d3d 100644
--- a/s3stream/src/main/java/com/automq/stream/s3/operator/ProxyWriter.java
+++ b/s3stream/src/main/java/com/automq/stream/s3/operator/ProxyWriter.java
@@ -62,6 +62,15 @@ public CompletableFuture<Void> write(ByteBuf part) {
         }
     }
 
+    @Override
+    public void copyOnWrite() {
+        if (multiPartWriter != null) {
+            multiPartWriter.copyOnWrite();
+        } else {
+            objectWriter.copyOnWrite();
+        }
+    }
+
     @Override
     public void copyWrite(String sourcePath, long start, long end) {
         if (multiPartWriter == null) {
@@ -110,6 +119,18 @@ public CompletableFuture<Void> write(ByteBuf part) {
             return cf;
         }
 
+        @Override
+        public void copyOnWrite() {
+            int size = data.readableBytes();
+            if (size > 0) {
+                ByteBuf buf = DirectByteBufAlloc.byteBuffer(size);
+                buf.writeBytes(data.duplicate());
+                CompositeByteBuf copy = DirectByteBufAlloc.compositeByteBuffer().addComponent(true, buf);
+                this.data.release();
+                this.data = copy;
+            }
+        }
+
         @Override
         public void copyWrite(String sourcePath, long start, long end) {
             throw new UnsupportedOperationException();
diff --git a/s3stream/src/main/java/com/automq/stream/s3/operator/Writer.java b/s3stream/src/main/java/com/automq/stream/s3/operator/Writer.java
index 3a89bf87c..70b09de2d 100644
--- a/s3stream/src/main/java/com/automq/stream/s3/operator/Writer.java
+++ b/s3stream/src/main/java/com/automq/stream/s3/operator/Writer.java
@@ -53,6 +53,12 @@ public interface Writer {
      */
     CompletableFuture<Void> write(ByteBuf part);
 
+    /**
+     * Make a copy of all cached buffer and release old one to prevent outside modification to underlying data and
+     * avoid holding buffer reference for too long.
+     */
+    void copyOnWrite();
+
     /**
      * Copy a part of the object.
      *