diff --git a/tentacle/src/session.rs b/tentacle/src/session.rs
index 10ec6682..5d275f17 100644
--- a/tentacle/src/session.rs
+++ b/tentacle/src/session.rs
@@ -10,7 +10,7 @@ use std::{
     time::Duration,
 };
 use tokio::io::{AsyncRead, AsyncWrite};
-use tokio_util::codec::{Framed, FramedParts, FramedRead, FramedWrite, LengthDelimitedCodec};
+use tokio_util::codec::{Framed, FramedParts, LengthDelimitedCodec};
 use yamux::{Control, Session as YamuxSession, StreamHandle};
 
 use crate::{
@@ -36,6 +36,19 @@ pub trait AsyncRw: AsyncWrite + AsyncRead {}
 
 impl<T: AsyncRead + AsyncWrite> AsyncRw for T {}
 
+fn split_spawn_framed<T, U>(
+    part: FramedParts<T, U>,
+) -> (
+    futures::stream::SplitSink<Framed<T, U>, bytes::Bytes>,
+    futures::stream::SplitStream<Framed<T, U>>,
+)
+where
+    T: AsyncRead + AsyncWrite,
+    U: crate::traits::Codec,
+{
+    Framed::from_parts(part).split()
+}
+
 /// Event generated/received by the Session
 pub(crate) enum SessionEvent {
     /// Session close event
@@ -432,13 +445,13 @@ impl Session {
 
         match proto.spawn {
             Some(ref spawn) => {
-                let (read, write) = crate::runtime::split(raw_part.io);
+                let mut part = FramedParts::new(raw_part.io, (proto.codec)());
+                part.read_buf = raw_part.read_buf;
+                part.write_buf = raw_part.write_buf;
+                let (write, read) = split_spawn_framed(part);
                 let read_part = {
-                    let mut frame = FramedRead::new(read, (proto.codec)());
-                    *frame.read_buffer_mut() = raw_part.read_buf;
-
                     SubstreamReadPart {
-                        substream: frame,
+                        substream: read,
                         before_receive: before_receive_fn,
                         proto_id,
                         stream_id: self.next_stream,
@@ -455,7 +468,7 @@ impl Session {
                 .proto_id(proto_id)
                 .stream_id(self.next_stream)
                 .config(self.config)
-                .build(FramedWrite::new(write, (proto.codec)()));
+                .build(write);
 
                 crate::runtime::spawn(write_part.for_each(|_| future::ready(())));
                 spawn.spawn(self.context.clone(), &self.service_control, read_part);
@@ -800,6 +813,37 @@ impl Stream for Session {
     }
 }
 
+#[cfg(all(test, not(target_family = "wasm")))]
+mod tests {
+    use super::split_spawn_framed;
+    use bytes::{Bytes, BytesMut};
+    use futures::StreamExt;
+    use tokio::io::duplex;
+    use tokio_util::codec::{Encoder, FramedParts, LengthDelimitedCodec};
+
+    #[tokio::test]
+    async fn split_spawn_framed_reads_buffered_first_frame() {
+        let (io, _peer) = duplex(64);
+        let mut codec = LengthDelimitedCodec::new();
+        let mut read_buf = BytesMut::new();
+        codec
+            .encode(Bytes::from_static(b"init"), &mut read_buf)
+            .expect("encode buffered first frame");
+
+        let mut parts = FramedParts::new(io, codec);
+        parts.read_buf = read_buf;
+
+        let (_write, mut read) = split_spawn_framed(parts);
+        let first = read
+            .next()
+            .await
+            .expect("buffered frame should be available")
+            .expect("buffered frame should decode");
+
+        assert_eq!(first.freeze(), Bytes::from_static(b"init"));
+    }
+}
+
 pub(crate) struct SessionMeta {
     config: SessionConfig,
     protocol_configs_by_name: HashMap<String, Arc<Meta>>,
diff --git a/tentacle/src/substream.rs b/tentacle/src/substream.rs
index 2be804c1..391e366e 100644
--- a/tentacle/src/substream.rs
+++ b/tentacle/src/substream.rs
@@ -1,4 +1,7 @@
-use futures::{SinkExt, StreamExt, channel::mpsc, prelude::*, stream::iter};
+use futures::{
+    SinkExt, StreamExt, channel::mpsc, prelude::*, stream::SplitSink, stream::SplitStream,
+    stream::iter,
+};
 use log::debug;
 use std::{
     collections::VecDeque,
@@ -8,7 +11,7 @@ use std::{
     task::{Context, Poll},
 };
 use tokio::io::AsyncWrite;
-use tokio_util::codec::{Framed, FramedRead, FramedWrite, length_delimited::LengthDelimitedCodec};
+use tokio_util::codec::{Framed, length_delimited::LengthDelimitedCodec};
 
 use crate::{
     ProtocolId, StreamId,
@@ -589,7 +592,7 @@ impl SubstreamBuilder {
 /* Code organization under read-write separation */
 
 pub(crate) struct SubstreamWritePart<U> {
-    substream: FramedWrite<crate::runtime::WriteHalf<StreamHandle>, U>,
+    substream: SplitSink<Framed<StreamHandle, U>, bytes::Bytes>,
     id: StreamId,
     proto_id: ProtocolId,
 
@@ -748,7 +751,7 @@ where
             Poll::Ready(None) => {
                 // Must be session close
                 self.dead = true;
-                if let Poll::Ready(Err(e)) = Pin::new(self.substream.get_mut()).poll_shutdown(cx) {
+                if let Poll::Ready(Err(e)) = Pin::new(&mut self.substream).poll_close(cx) {
                     log::trace!("sub stream poll shutdown err {}", e)
                 }
                 Poll::Ready(None)
@@ -777,7 +780,7 @@ where
 
     fn close_proto_stream(&mut self, cx: &mut Context) {
         self.event_receiver.close();
-        if let Poll::Ready(Err(e)) = Pin::new(self.substream.get_mut()).poll_shutdown(cx) {
+        if let Poll::Ready(Err(e)) = Pin::new(&mut self.substream).poll_close(cx) {
             log::trace!("sub stream poll shutdown err {}", e)
         }
         if !self.context.closed.load(Ordering::SeqCst) {
@@ -860,8 +863,7 @@ where
 
 /// Protocol Stream read part
 pub struct SubstreamReadPart {
-    pub(crate) substream:
-        FramedRead<crate::runtime::ReadHalf<StreamHandle>, Box<dyn Codec + Send + 'static>>,
+    pub(crate) substream: SplitStream<Framed<StreamHandle, Box<dyn Codec + Send + 'static>>>,
     pub(crate) before_receive: Option<BeforeReceive>,
     pub(crate) proto_id: ProtocolId,
     pub(crate) stream_id: StreamId,
@@ -964,7 +966,7 @@ impl SubstreamWritePartBuilder {
 
     pub fn build<U>(
         self,
-        substream: FramedWrite<crate::runtime::WriteHalf<StreamHandle>, U>,
+        substream: SplitSink<Framed<StreamHandle, U>, bytes::Bytes>,
     ) -> SubstreamWritePart<U>
     where
         U: Codec,