diff --git a/proxy/shadowsocks_2022/inbound.go b/proxy/shadowsocks_2022/inbound.go
index eaa637d30..ca07fa3ae 100644
--- a/proxy/shadowsocks_2022/inbound.go
+++ b/proxy/shadowsocks_2022/inbound.go
@@ -146,9 +146,8 @@ func (i *Inbound) processTCP(ctx context.Context, conn net.Conn, dispatcher rout
 	}
 
 	if len(reqHeader.EarlyData) > 0 {
-		earlyBuf := buf.New()
-		earlyBuf.Write(reqHeader.EarlyData)
-		if err := link.Writer.WriteMultiBuffer(buf.MultiBuffer{earlyBuf}); err != nil {
+		mb := buf.MergeBytes(nil, reqHeader.EarlyData)
+		if err := link.Writer.WriteMultiBuffer(mb); err != nil {
 			return err
 		}
 	}
diff --git a/proxy/shadowsocks_2022/inbound_multi.go b/proxy/shadowsocks_2022/inbound_multi.go
index 45df40e53..f46bf72a7 100644
--- a/proxy/shadowsocks_2022/inbound_multi.go
+++ b/proxy/shadowsocks_2022/inbound_multi.go
@@ -283,9 +283,8 @@ func (i *MultiUserInbound) processTCP(ctx context.Context, conn net.Conn, dispat
 	}
 
 	if len(reqHeader.EarlyData) > 0 {
-		earlyBuf := buf.New()
-		earlyBuf.Write(reqHeader.EarlyData)
-		if err := link.Writer.WriteMultiBuffer(buf.MultiBuffer{earlyBuf}); err != nil {
+		mb := buf.MergeBytes(nil, reqHeader.EarlyData)
+		if err := link.Writer.WriteMultiBuffer(mb); err != nil {
 			return err
 		}
 	}
@@ -361,15 +360,11 @@ func (i *MultiUserInbound) processUDP(ctx context.Context, conn stat.Connection,
 			} else {
 				sessionItem.Unlock()
 				// Decrypt EIH
-				identitySubkey := DeriveIdentitySubKey(i.masterPSK, rawHeader[:8], i.method.KeySaltLength)
-				idBlock, err := i.method.NewBlock(identitySubkey)
-				if err != nil {
-					b.Release()
-					continue
-				}
-
 				var decryptedHash [16]byte
-				idBlock.Decrypt(decryptedHash[:], packetBytes[16:32])
+				i.udpMasterCipher.Decrypt(decryptedHash[:], packetBytes[16:32])
+				for k := 0; k < 16; k++ {
+					decryptedHash[k] ^= rawHeader[k]
+				}
 
 				user, ok := i.usersByHash.Load(decryptedHash)
 				if !ok || user == nil {
diff --git a/proxy/shadowsocks_2022/outbound.go b/proxy/shadowsocks_2022/outbound.go
index 71d21475d..ff1be9f06 100644
--- a/proxy/shadowsocks_2022/outbound.go
+++ b/proxy/shadowsocks_2022/outbound.go
@@ -47,7 +47,7 @@ func NewClient(ctx context.Context, config *ClientConfig) (*Outbound, error) {
 	}
 
 	finalPSK := pskList[len(pskList)-1]
-	udpCodec, err := NewUDPPacketCodec(method, finalPSK)
+	udpCodec, err := NewUDPPacketCodec(method, pskList)
 	if err != nil {
 		return nil, errors.New("failed to create udp packet codec").Base(err)
 	}
diff --git a/proxy/shadowsocks_2022/packet.go b/proxy/shadowsocks_2022/packet.go
index f0d1daba7..fc906aeb8 100644
--- a/proxy/shadowsocks_2022/packet.go
+++ b/proxy/shadowsocks_2022/packet.go
@@ -17,8 +17,10 @@ import (
 
 type UDPCodec struct {
 	method           *CipherMethod
+	pskList          [][]byte
 	psk              []byte
 	blockCipher      cipher.Block
+	blockCiphers     []cipher.Block
 	chachaCipher     cipher.AEAD
 	clientBodyCipher cipher.AEAD
 	clientSessionID  uint64
@@ -48,11 +50,23 @@ func newUDPCodec(method *CipherMethod, psk []byte) (*UDPCodec, error) {
 	return c, nil
 }
 
-func NewUDPPacketCodec(method *CipherMethod, psk []byte) (*UDPCodec, error) {
-	c, err := newUDPCodec(method, psk)
+func NewUDPPacketCodec(method *CipherMethod, pskList [][]byte) (*UDPCodec, error) {
+	finalPSK := pskList[len(pskList)-1]
+	c, err := newUDPCodec(method, finalPSK)
 	if err != nil {
 		return nil, err
 	}
+	c.pskList = pskList
+	if len(pskList) > 1 && !method.IsChaCha {
+		c.blockCiphers = make([]cipher.Block, len(pskList))
+		for i, psk := range pskList {
+			c.blockCiphers[i], err = method.NewBlock(psk)
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+
 	var sessID [8]byte
 	if _, err := io.ReadFull(rand.Reader, sessID[:]); err != nil {
 		return nil, err
@@ -60,7 +74,7 @@ func NewUDPPacketCodec(method *CipherMethod, psk []byte) (*UDPCodec, error) {
 	c.clientSessionID = binary.BigEndian.Uint64(sessID[:])
 
 	if !method.IsChaCha {
-		clientBodyKey := DeriveSessionSubKey(psk, sessID[:], method.KeySaltLength)
+		clientBodyKey := DeriveSessionSubKey(finalPSK, sessID[:], method.KeySaltLength)
 		c.clientBodyCipher, err = method.NewAEAD(clientBodyKey)
 		if err != nil {
 			return nil, err
@@ -130,21 +144,50 @@ func (c *UDPCodec) EncodeClientPacket(dest net.Destination, payload []byte) (*bu
 	}
 
 	// AES mode:
-	// 16B Encrypted Header + (11B header + padding + dest + payload + 16B AEAD tag)
-	totalLen := 16 + 11 + paddingLen + addrPortLen + len(payload) + AEADTagSize
+	var sessBytes [8]byte
+	binary.BigEndian.PutUint64(sessBytes[:], sessID)
+
+	var rawHeader [16]byte
+	copy(rawHeader[:8], sessBytes[:])
+	binary.BigEndian.PutUint64(rawHeader[8:16], packetID)
+
+	eihCount := 0
+	if len(c.pskList) > 1 {
+		eihCount = len(c.pskList) - 1
+	}
+
+	totalLen := 16 + eihCount*16 + 11 + paddingLen + addrPortLen + len(payload) + AEADTagSize
 	if totalLen > buf.Size {
 		return nil, ErrPacketTooLarge
 	}
 
 	outBuf := buf.New()
 
-	var rawHeader [16]byte
-	binary.BigEndian.PutUint64(rawHeader[:8], sessID)
-	binary.BigEndian.PutUint64(rawHeader[8:16], packetID)
+	if len(c.pskList) > 1 {
+		// Multi-user / Relay mode:
+		// 1. Header (16B) encrypted with first hop's block cipher
+		var encryptedHeader [16]byte
+		c.blockCiphers[0].Encrypt(encryptedHeader[:], rawHeader[:])
+		outBuf.Write(encryptedHeader[:])
 
-	var encryptedHeader [16]byte
-	c.blockCipher.Encrypt(encryptedHeader[:], rawHeader[:])
-	outBuf.Write(encryptedHeader[:])
+		// 2. Multi-hop EIHs for intermediate hops
+		for i := 0; i < len(c.pskList)-1; i++ {
+			nextPSK := c.pskList[i+1]
+			pskHash := DeriveUserPSKHash(nextPSK)
+			var eihPlain [16]byte
+			for k := 0; k < 16; k++ {
+				eihPlain[k] = pskHash[k] ^ rawHeader[k]
+			}
+			var encryptedEIH [16]byte
+			c.blockCiphers[i].Encrypt(encryptedEIH[:], eihPlain[:])
+			outBuf.Write(encryptedEIH[:])
+		}
+	} else {
+		// Single-user mode:
+		var encryptedHeader [16]byte
+		c.blockCipher.Encrypt(encryptedHeader[:], rawHeader[:])
+		outBuf.Write(encryptedHeader[:])
+	}
 
 	bodyAead := c.clientBodyCipher
 
@@ -163,7 +206,8 @@ func (c *UDPCodec) EncodeClientPacket(dest net.Destination, payload []byte) (*bu
 	}
 	outBuf.Write(payload)
 
-	plainBytes := outBuf.Bytes()[16:]
+	headerOffset := 16 + eihCount*16
+	plainBytes := outBuf.Bytes()[headerOffset:]
 	bodyNonce := rawHeader[4:16]
 	outBuf.Extend(int32(bodyAead.Overhead()))
 	bodyAead.Seal(plainBytes[:0], bodyNonce, plainBytes, nil)
diff --git a/proxy/shadowsocks_2022/shadowsocks_2022_test.go b/proxy/shadowsocks_2022/shadowsocks_2022_test.go
index f6f930a27..bcec78d50 100644
--- a/proxy/shadowsocks_2022/shadowsocks_2022_test.go
+++ b/proxy/shadowsocks_2022/shadowsocks_2022_test.go
@@ -272,7 +272,7 @@ func TestUDPCodec(t *testing.T) {
 			psk := make([]byte, method.KeySaltLength)
 			_, _ = rand.Read(psk)
 
-			clientCodec, err := NewUDPPacketCodec(method, psk)
+			clientCodec, err := NewUDPPacketCodec(method, [][]byte{psk})
 			common.Must(err)
 			serverCodec, err := NewUDPServerCodec(method, psk, time.Minute)
 			common.Must(err)
@@ -360,3 +360,66 @@ func TestMultiUserManager(t *testing.T) {
 		t.Fatal("user1 should have been removed")
 	}
 }
+
+func TestLargeStreamTransfer(t *testing.T) {
+	method, err := GetCipherMethod(MethodAES128GCM)
+	common.Must(err)
+	sessionKey := make([]byte, 16)
+	_, _ = rand.Read(sessionKey)
+
+	clientAead, err := method.NewAEAD(sessionKey)
+	common.Must(err)
+	serverAead, err := method.NewAEAD(sessionKey)
+	common.Must(err)
+
+	r, w := io.Pipe()
+	defer r.Close()
+	defer w.Close()
+
+	writer := NewStreamWriter(w, clientAead)
+	reader := NewStreamReader(r, serverAead)
+
+	const totalSize = 100 * 1024 // 100 KB
+	data := make([]byte, totalSize)
+	_, _ = rand.Read(data)
+
+	errCh := make(chan error, 1)
+	go func() {
+		// Write using Write (which splits by MaxPacketSize = 65535)
+		_, werr := writer.Write(data)
+		if werr != nil {
+			errCh <- werr
+			return
+		}
+		_ = w.Close()
+		errCh <- nil
+	}()
+
+	var received []byte
+	for {
+		mb, rerr := reader.ReadMultiBuffer()
+		if !mb.IsEmpty() {
+			for _, b := range mb {
+				received = append(received, b.Bytes()...)
+			}
+			buf.ReleaseMulti(mb)
+		}
+		if rerr != nil {
+			if rerr == io.EOF {
+				break
+			}
+			t.Fatalf("ReadMultiBuffer error: %v", rerr)
+		}
+	}
+
+	if werr := <-errCh; werr != nil {
+		t.Fatalf("writer error: %v", werr)
+	}
+
+	if len(received) != totalSize {
+		t.Fatalf("received size mismatch: got %d, want %d", len(received), totalSize)
+	}
+	if !bytes.Equal(received, data) {
+		t.Fatal("received data does not match sent data")
+	}
+}
diff --git a/proxy/shadowsocks_2022/stream.go b/proxy/shadowsocks_2022/stream.go
index 3e21734e7..14afd66dc 100644
--- a/proxy/shadowsocks_2022/stream.go
+++ b/proxy/shadowsocks_2022/stream.go
@@ -119,8 +119,16 @@ func (w *StreamWriter) Write(p []byte) (int, error) {
 func (w *StreamWriter) WriteMultiBuffer(mb buf.MultiBuffer) error {
 	defer buf.ReleaseMulti(mb)
 	for _, b := range mb {
-		if err := w.WriteChunk(b.Bytes()); err != nil {
-			return err
+		p := b.Bytes()
+		for len(p) > 0 {
+			chunkSize := len(p)
+			if chunkSize > MaxPacketSize {
+				chunkSize = MaxPacketSize
+			}
+			if err := w.WriteChunk(p[:chunkSize]); err != nil {
+				return err
+			}
+			p = p[chunkSize:]
 		}
 	}
 	return nil
@@ -168,7 +176,7 @@ func (r *StreamReader) Read(p []byte) (int, error) {
 	IncreaseNonce(r.nonce[:])
 
 	payloadLen := int(binary.BigEndian.Uint16(decryptedLen))
-	if payloadLen == 0 {
+	if payloadLen == 0 || payloadLen > MaxPacketSize {
 		return 0, ErrInvalidRequest
 	}
 
@@ -194,11 +202,10 @@ func (r *StreamReader) Read(p []byte) (int, error) {
 
 func (r *StreamReader) ReadMultiBuffer() (buf.MultiBuffer, error) {
 	if r.cached > 0 {
-		b := buf.New()
-		b.Write(r.buffer[r.offset : r.offset+r.cached])
+		mb := buf.MergeBytes(nil, r.buffer[r.offset:r.offset+r.cached])
 		r.cached = 0
 		r.offset = 0
-		return buf.MultiBuffer{b}, nil
+		return mb, nil
 	}
 
 	if _, err := io.ReadFull(r.reader, r.lenBuf[:]); err != nil {
@@ -212,7 +219,7 @@ func (r *StreamReader) ReadMultiBuffer() (buf.MultiBuffer, error) {
 	IncreaseNonce(r.nonce[:])
 
 	payloadLen := int(binary.BigEndian.Uint16(decryptedLen))
-	if payloadLen == 0 {
+	if payloadLen == 0 || payloadLen > MaxPacketSize {
 		return nil, ErrInvalidRequest
 	}
 
@@ -227,9 +234,8 @@ func (r *StreamReader) ReadMultiBuffer() (buf.MultiBuffer, error) {
 	}
 	IncreaseNonce(r.nonce[:])
 
-	b := buf.New()
-	b.Write(decryptedPayload)
-	return buf.MultiBuffer{b}, nil
+	mb := buf.MergeBytes(nil, decryptedPayload)
+	return mb, nil
 }
 
 type ClientRequestHeader struct {
@@ -282,31 +288,27 @@ func ReadClientRequestHeader(conn io.Reader, reader *StreamReader) (*ClientReque
 	}
 	IncreaseNonce(reader.Nonce())
 
-	b := buf.New()
-	b.Write(plainVar)
-	defer b.Release()
-
-	dest, err := ReadAddressPort(b)
+	dest, addrLen, err := parseAddressPort(plainVar)
 	if err != nil {
 		return nil, err
 	}
+	dest.Network = net.Network_TCP
 
-	var padLenBytes [2]byte
-	if _, err := b.Read(padLenBytes[:]); err != nil {
-		return nil, err
+	offset := addrLen
+	if len(plainVar) < offset+2 {
+		return nil, ErrPacketTooShort
 	}
-	paddingLen := int(binary.BigEndian.Uint16(padLenBytes[:]))
-	if int(b.Len()) < paddingLen {
+	paddingLen := int(binary.BigEndian.Uint16(plainVar[offset : offset+2]))
+	offset += 2
+
+	if len(plainVar) < offset+paddingLen {
 		return nil, ErrNoPadding
 	}
-	if paddingLen > 0 {
-		b.Advance(int32(paddingLen))
-	}
+	offset += paddingLen
 
 	var earlyData []byte
-	if b.Len() > 0 {
-		earlyData = make([]byte, b.Len())
-		copy(earlyData, b.Bytes())
+	if len(plainVar) > offset {
+		earlyData = plainVar[offset:]
 	}
 
 	return &ClientRequestHeader{