diff --git a/engine/iouring/consts.go b/engine/iouring/consts.go
index 7c055f9..09693fe 100644
--- a/engine/iouring/consts.go
+++ b/engine/iouring/consts.go
@@ -52,12 +52,6 @@ const (
 	acceptMultishot = 1 << 0
 )
 
-// Recv flags.
-const (
-	recvMultishot = 1 << 1
-	msgPeek       = 0x2
-)
-
 // Mmap offsets for ring buffers.
 const (
 	offSQRing = 0
diff --git a/engine/iouring/cqe.go b/engine/iouring/cqe.go
index d453aaf..0cc1cb9 100644
--- a/engine/iouring/cqe.go
+++ b/engine/iouring/cqe.go
@@ -15,7 +15,6 @@ const (
 	udRecv    uint64 = 0x02 << 56
 	udSend    uint64 = 0x03 << 56
 	udClose   uint64 = 0x04 << 56
-	udPeek    uint64 = 0x05 << 56
 	udProvide uint64 = 0x06 << 56
 	udMask    uint64 = 0xFF << 56
 	fdMask    uint64 = (1 << 56) - 1
diff --git a/engine/iouring/sqe.go b/engine/iouring/sqe.go
index c289ddd..879597b 100644
--- a/engine/iouring/sqe.go
+++ b/engine/iouring/sqe.go
@@ -63,17 +63,6 @@ func prepProvideBuffers(sqePtr unsafe.Pointer, addr unsafe.Pointer, bufLen int,
 	*(*uint16)(unsafe.Pointer(&sqe[28])) = bufID
 }
 
-func prepRecvPeek(sqePtr unsafe.Pointer, fd int, buf []byte) {
-	sqe := (*[sqeSize]byte)(sqePtr)
-	sqe[0] = opRECV
-	*(*int32)(unsafe.Pointer(&sqe[4])) = int32(fd)
-	if len(buf) > 0 {
-		*(*uint64)(unsafe.Pointer(&sqe[16])) = uint64(uintptr(unsafe.Pointer(&buf[0])))
-		*(*uint32)(unsafe.Pointer(&sqe[24])) = uint32(len(buf))
-	}
-	*(*uint32)(unsafe.Pointer(&sqe[28])) = msgPeek // msg_flags at offset 28
-}
-
 func setSQEUserData(sqePtr unsafe.Pointer, data uint64) {
 	*(*uint64)(unsafe.Pointer(uintptr(sqePtr) + 32)) = data
 }
diff --git a/engine/iouring/worker.go b/engine/iouring/worker.go
index 7d8db2d..953aa7f 100644
--- a/engine/iouring/worker.go
+++ b/engine/iouring/worker.go
@@ -164,8 +164,6 @@ func (w *Worker) processCQE(ctx context.Context, c *completionEntry) {
 		w.handleSend(c, fd)
 	case udClose:
 		w.handleClose(fd)
-	case udPeek:
-		w.handlePeek(c, fd)
 	case udProvide:
 		// Buffer provide completion, no action needed
 	}
@@ -196,57 +194,36 @@ func (w *Worker) handleAccept(ctx context.Context, c *completionEntry, listenFD
 	w.conns[newFD] = cs
 	w.activeConns.Add(1)
 
-	if w.cfg.Protocol == engine.Auto {
-		sqe := w.ring.GetSQE()
-		if sqe != nil {
-			prepRecvPeek(sqe, newFD, cs.buf[:detect.MinPeekBytes])
-			setSQEUserData(sqe, encodeUserData(udPeek, newFD))
-		}
-	} else {
+	if w.cfg.Protocol != engine.Auto {
 		cs.protocol = w.cfg.Protocol
 		cs.detected = true
 		w.initProtocol(cs)
-		w.tier.PrepareRecv(w.ring, newFD, cs.buf)
 	}
+	// For Auto mode, cs.detected is false; the first handleRecv will
+	// detect the protocol from the received data before processing it.
+	w.tier.PrepareRecv(w.ring, newFD, cs.buf)
 
 	if !cqeHasMore(c.Flags) && !w.tier.SupportsMultishotAccept() {
 		w.tier.PrepareAccept(w.ring, listenFD)
 	}
 }
 
-func (w *Worker) handlePeek(c *completionEntry, fd int) {
-	cs, ok := w.conns[fd]
-	if !ok {
-		return
-	}
-
-	if c.Res < int32(detect.MinPeekBytes) {
-		sqe := w.ring.GetSQE()
-		if sqe != nil {
-			prepRecvPeek(sqe, fd, cs.buf[:24])
-			setSQEUserData(sqe, encodeUserData(udPeek, fd))
-		}
-		return
-	}
-
-	proto, err := detect.Detect(cs.buf[:c.Res])
-	if err == detect.ErrInsufficientData {
-		sqe := w.ring.GetSQE()
-		if sqe != nil {
-			prepRecvPeek(sqe, fd, cs.buf[:24])
-			setSQEUserData(sqe, encodeUserData(udPeek, fd))
-		}
-		return
-	}
+// detectProtocol performs protocol detection on the first received bytes.
+// Returns true if detection succeeded and the data should be processed.
+func (w *Worker) detectProtocol(cs *connState, data []byte) bool {
+	proto, err := detect.Detect(data)
 	if err != nil {
-		w.closeConn(fd)
-		return
+		if err == detect.ErrInsufficientData {
+			// Need more data — re-arm recv. The data is already in cs.buf
+			// so we don't lose it; the next recv appends after it.
+			return false
+		}
+		return false
 	}
-
 	cs.protocol = proto
 	cs.detected = true
 	w.initProtocol(cs)
-	w.tier.PrepareRecv(w.ring, fd, cs.buf)
+	return true
 }
 
 func (w *Worker) initProtocol(cs *connState) {
@@ -285,6 +262,15 @@ func (w *Worker) handleRecv(c *completionEntry, fd int) {
 		}
 	}
 
+	// Auto protocol detection on first recv (no MSG_PEEK needed).
+	if !cs.detected {
+		if !w.detectProtocol(cs, data) {
+			// Need more data or unknown protocol — re-arm recv.
+			w.tier.PrepareRecv(w.ring, fd, cs.buf)
+			return
+		}
+	}
+
 	writeFn := w.makeWriteFn(fd)
 
 	var processErr error
diff --git a/protocol/h2/stream/flowcontrol.go b/protocol/h2/stream/flowcontrol.go
index 93a4300..53d0a53 100644
--- a/protocol/h2/stream/flowcontrol.go
+++ b/protocol/h2/stream/flowcontrol.go
@@ -4,7 +4,7 @@ import (
 	"sync/atomic"
 )
 
-const windowUpdateThreshold = 16384
+const windowUpdateThreshold = 1024
 
 // ConsumeSendWindow decrements connection and stream windows after sending DATA.
 func (m *Manager) ConsumeSendWindow(streamID uint32, n int32) {
@@ -51,39 +51,24 @@ func (m *Manager) AccumulateWindowUpdate(streamID uint32, increment uint32) {
 // Returns true if updates were sent.
 func (m *Manager) FlushWindowUpdates(writer FrameWriter, force bool) bool {
 	m.windowUpdateMu.Lock()
+	defer m.windowUpdateMu.Unlock()
 
-	connUpdate := m.pendingConnWindowUpdate
-	needsConnFlush := force || connUpdate >= windowUpdateThreshold
-
-	streamUpdates := make(map[uint32]uint32)
-	for sid, pending := range m.pendingStreamUpdates {
-		if pending != nil && *pending > 0 {
-			if force || *pending >= windowUpdateThreshold {
-				streamUpdates[sid] = *pending
-			}
-		}
-	}
+	flushed := false
 
-	if needsConnFlush {
+	connUpdate := m.pendingConnWindowUpdate
+	if connUpdate > 0 && (force || connUpdate >= windowUpdateThreshold) {
 		m.pendingConnWindowUpdate = 0
-	}
-	for sid := range streamUpdates {
-		if m.pendingStreamUpdates[sid] != nil {
-			*m.pendingStreamUpdates[sid] = 0
-		}
-	}
-
-	m.windowUpdateMu.Unlock()
-
-	flushed := false
-	if needsConnFlush && connUpdate > 0 {
 		_ = writer.WriteWindowUpdate(0, connUpdate)
 		flushed = true
 	}
 
-	for sid, increment := range streamUpdates {
-		_ = writer.WriteWindowUpdate(sid, increment)
-		flushed = true
+	for sid, pending := range m.pendingStreamUpdates {
+		if pending != nil && *pending > 0 && (force || *pending >= windowUpdateThreshold) {
+			val := *pending
+			*pending = 0
+			_ = writer.WriteWindowUpdate(sid, val)
+			flushed = true
+		}
 	}
 
 	return flushed
diff --git a/protocol/h2/stream/manager.go b/protocol/h2/stream/manager.go
index 6a609b2..56f212b 100644
--- a/protocol/h2/stream/manager.go
+++ b/protocol/h2/stream/manager.go
@@ -102,6 +102,10 @@ func (m *Manager) DeleteStream(id uint32) {
 	}
 	delete(m.streams, id)
 	m.priorityTree.RemoveStream(id)
+
+	m.windowUpdateMu.Lock()
+	delete(m.pendingStreamUpdates, id)
+	m.windowUpdateMu.Unlock()
 }
 
 // StreamCount returns the number of streams in the manager.