diff --git a/metadaptb.go b/metadaptb.go
index 867dedb..c91db72 100644
--- a/metadaptb.go
+++ b/metadaptb.go
@@ -2,6 +2,7 @@ package hopp
 
 import "io"
 import "net"
+import "bytes"
 import "errors"
 import "context"
 import "git.tebibyte.media/sashakoshka/hopp/tape"
@@ -58,9 +59,10 @@ func (this *b) newTrans(underlying Stream) *transB {
 }
 
 type transB struct {
-	sizeLimit int64
-	underlying Stream
-	currentData io.Reader
+	sizeLimit     int64
+	underlying    Stream
+	currentData   io.Reader
+	currentWriter *writerB
 }
 
 func (this *transB) Close() error {
@@ -75,6 +77,24 @@ func (this *transB) Send(method uint16, data []byte) error {
 	return encodeMessageB(this.underlying, this.sizeLimit, method, data)
 }
 
+func (this *transB) SendWriter(method uint16) (io.WriteCloser, error) {
+	if this.currentWriter != nil {
+		this.currentWriter.Close()
+	}
+	// TODO: come up with a fix that allows us to pipe data through the
+	// writer. as of now, it just reads whatever is written into a buffer
+	// and sends the message on close. we should probably introduce chunked
+	// encoding to METADAPT-B to fix this. the implementation would be
+	// simpler than on METADAPT-A, but most of the code could just be
+	// copied over.
+	writer := &writerB {
+		parent: this,
+		method: method,
+	}
+	this.currentWriter = writer
+	return writer, nil
+}
+
 func (this *transB) Receive() (uint16, []byte, error) {
 	// get a reader for the next message
 	method, size, data, err := this.receiveReader()
@@ -105,6 +125,20 @@ func (this *transB) receiveReader() (uint16, int64, io.Reader, error) {
 	return method, size, data, nil
 }
 
+type writerB struct {
+	parent *transB
+	buffer bytes.Buffer
+	method uint16
+}
+
+func (this *writerB) Write(data []byte) (int, error) {
+	return this.buffer.Write(data)
+}
+
+func (this *writerB) Close() error {
+	return this.parent.Send(this.method, this.buffer.Bytes())
+}
+
 // MultiConn represens a multiplexed stream-oriented transport for use in
 // [AdaptB].
 type MultiConn interface {