diff --git a/fileplayback/player.go b/fileplayback/player.go
index 90e492d..a3ad9ec 100644
--- a/fileplayback/player.go
+++ b/fileplayback/player.go
@@ -1,6 +1,7 @@
 package fileplayback
 
 import (
+	"context"
 	"encoding/binary"
 	"errors"
 	"io"
@@ -18,6 +19,8 @@ type Player struct {
 	filename  string
 	audioChan chan gumble.AudioBuffer
 	stopChan  chan struct{}
+	ctx       context.Context
+	cancel    context.CancelFunc
 	mutex     sync.Mutex
 	playing   bool
 	errorFunc func(error)
@@ -73,6 +76,7 @@ func (p *Player) PlayFile(filename string) error {
 	// Start the file reading goroutine
 	p.playing = true
 	p.stopChan = make(chan struct{})
+	p.ctx, p.cancel = context.WithCancel(context.Background())
 	go p.readFileAudio()
 
 	return nil
@@ -88,17 +92,23 @@ func (p *Player) Stop() error {
 	}
 
 	close(p.stopChan)
+	if p.cancel != nil {
+		p.cancel()
+		p.cancel = nil
+	}
 	p.playing = false
+	localPlayback := p.localPlayback
+	p.mutex.Unlock()
 
-	if p.localPlayback != nil {
-		p.localPlayback(nil)
+	if localPlayback != nil {
+		localPlayback(nil)
 	}
 
-	// Drain the audio channel
+	// Drain the audio channel.
 	for len(p.audioChan) > 0 {
 		<-p.audioChan
 	}
-
+	p.mutex.Lock()
 	return nil
 }
 
@@ -138,7 +148,10 @@ func (p *Player) readFileAudio() {
 	args := []string{"-loglevel", "error", "-i", p.filename}
 	args = append(args, "-ac", "2", "-ar", strconv.Itoa(gumble.AudioSampleRate), "-f", "s16le", "-")
 
-	cmd := exec.Command("ffmpeg", args...)
+	p.mutex.Lock()
+	ctx := p.ctx
+	p.mutex.Unlock()
+	cmd := exec.CommandContext(ctx, "ffmpeg", args...)
 	pipe, err := cmd.StdoutPipe()
 	if err != nil {
 		p.mutex.Lock()
@@ -171,15 +184,21 @@ func (p *Player) readFileAudio() {
 		case <-ticker.C:
 			n, err := io.ReadFull(pipe, byteBuffer)
 			if err != nil || n != len(byteBuffer) {
-				// File finished playing
+				select {
+				case <-p.stopChan:
+					cmd.Wait()
+					return
+				default:
+				}
+				// File finished playing.
 				p.mutex.Lock()
 				p.playing = false
-				if p.localPlayback != nil {
-					p.localPlayback(nil)
-				}
+				localPlayback := p.localPlayback
 				p.mutex.Unlock()
+				if localPlayback != nil {
+					localPlayback(nil)
+				}
 				cmd.Wait()
-				// Notify that file finished
 				p.reportError(errors.New("file playback finished"))
 				return
 			}
diff --git a/gumble/gumble/audio.go b/gumble/gumble/audio.go
index 8dcea1f..fbf74a1 100644
--- a/gumble/gumble/audio.go
+++ b/gumble/gumble/audio.go
@@ -90,6 +90,7 @@ type AudioPacket struct {
 
 	AudioBuffer
 
-	HasPosition bool
-	X, Y, Z     float32
+	HasPosition      bool
+	X, Y, Z          float32
+	VolumeAdjustment float32
 }
diff --git a/gumble/gumble/audiolisteners.go b/gumble/gumble/audiolisteners.go
index 7bf0e80..cc034d8 100644
--- a/gumble/gumble/audiolisteners.go
+++ b/gumble/gumble/audiolisteners.go
@@ -1,5 +1,7 @@
 package gumble
 
+import "sync"
+
 type audioEventItem struct {
 	parent     *AudioListeners
 	prev, next *audioEventItem
@@ -8,6 +10,8 @@ type audioEventItem struct {
 }
 
 func (e *audioEventItem) Detach() {
+	e.parent.mu.Lock()
+	defer e.parent.mu.Unlock()
 	if e.prev == nil {
 		e.parent.head = e.next
 	} else {
@@ -23,11 +27,14 @@ func (e *audioEventItem) Detach() {
 // AudioListeners is a list of audio listeners. Each attached listener is
 // called in sequence when a new user audio stream begins.
 type AudioListeners struct {
+	mu         sync.Mutex
 	head, tail *audioEventItem
 }
 
 // Attach adds a new audio listener to the end of the current list of listeners.
 func (e *AudioListeners) Attach(listener AudioListener) Detacher {
+	e.mu.Lock()
+	defer e.mu.Unlock()
 	item := &audioEventItem{
 		parent:   e,
 		prev:     e.tail,
diff --git a/gumble/gumble/client.go b/gumble/gumble/client.go
index 06a3d54..fb44557 100644
--- a/gumble/gumble/client.go
+++ b/gumble/gumble/client.go
@@ -6,6 +6,7 @@ import (
 	"math"
 	"net"
 	"runtime"
+	"sync"
 	"sync/atomic"
 	"time"
 
@@ -70,10 +71,17 @@ type Client struct {
 	VoiceTarget *VoiceTarget
 
 	// UDP transport for audio (lower latency than TCP-tunneled audio).
-	udpConn   *net.UDPConn
-	udpActive bool
-	cryptOut  cryptState // client→server encryption
-	cryptIn   cryptState // server→client encryption
+	udpMu             sync.RWMutex
+	udpWriteMu        sync.Mutex
+	udpConn           *net.UDPConn
+	udpActive         bool
+	udpCryptoOut      *cryptState15
+	udpCryptoIn       *cryptState15
+	udpFrameNumber    uint64
+	udpFallbackLogged atomic.Bool
+	udpFirstRecv      atomic.Bool
+	cryptOut          cryptState // client→server encryption
+	cryptIn           cryptState // server→client encryption
 
 	state uint32
 
@@ -258,7 +266,10 @@ func (c *Client) readRoutine() {
 		}
 		// When UDP audio is active, ignore TCP-tunneled audio
 		// (packet type 1) to avoid double-processing packets.
-		if pType == 1 && c.udpActive {
+		c.udpMu.RLock()
+		udpActive := c.udpActive
+		c.udpMu.RUnlock()
+		if pType == 1 && udpActive {
 			continue
 		}
 		if int(pType) < len(handlers) {
@@ -270,11 +281,15 @@ func (c *Client) readRoutine() {
 	atomic.StoreUint32(&c.state, uint32(StateDisconnected))
 	close(c.end)
 
-	// Clean up UDP connection
-	if c.udpConn != nil {
+	// Clean up UDP connection.
+	c.udpMu.Lock()
+	udpConn := c.udpConn
+	c.udpConn = nil
+	c.udpActive = false
+	c.udpMu.Unlock()
+	if udpConn != nil {
 		log.Debug("closing UDP connection")
-		c.udpConn.Close()
-		c.udpConn = nil
+		udpConn.Close()
 	}
 
 	if wasSynced {
@@ -331,27 +346,29 @@ func (c *Client) EnableStereoEncoder() {
 
 // WriteAudio writes an audio packet, preferring UDP when encryption is
 // set up. Falls back to TCP-tunneled audio when UDP is unavailable.
-var udpFallbackLogged bool
 
 func (c *Client) WriteAudio(format, target byte, sequence int64, final bool, data []byte, X, Y, Z *float32) error {
 	// Try Mumble 1.5 native UDP first (unless disabled)
 	if !c.Config.DisableUDP {
-		if sent, err := c.WriteAudioUDP15(data, final); sent {
+		if sent, err := c.WriteAudioUDP15(uint32(target), data, final); sent {
 			if err != nil {
 				log.Error("UDP15 send error: %v", err)
 			}
 			return err
 		}
 	}
-	// Fall back to TCP tunnel — log once per process
-	if !udpFallbackLogged {
-		udpFallbackLogged = true
+	// Fall back to the TCP tunnel.
+	c.udpMu.RLock()
+	udpConn := c.udpConn
+	udpCryptoOut := c.udpCryptoOut
+	c.udpMu.RUnlock()
+	if !c.udpFallbackLogged.Swap(true) {
 		if c.Config.DisableUDP {
 			log.Info("UDP disabled, audio using TCP tunnel")
-		} else if c.udpConn == nil {
+		} else if udpConn == nil {
 			log.Info("no UDP socket, audio using TCP tunnel")
-		} else if udp15Client == nil || !udp15Client.initialized {
-			log.Info("1.5 crypto not ready, audio using TCP tunnel")
+		} else if udpCryptoOut == nil {
+			log.Info("UDP crypto not ready, audio using TCP tunnel")
 		}
 	}
 	return c.Conn.WriteAudio(format, target, sequence, final, data, X, Y, Z)
diff --git a/gumble/gumble/crypt.go b/gumble/gumble/crypt.go
index f62c8fb..9d74ea1 100644
--- a/gumble/gumble/crypt.go
+++ b/gumble/gumble/crypt.go
@@ -253,11 +253,13 @@ func (cs *cryptState) setup(key, iv []byte) error {
 
 	cs.initialized = true
 
-	log.Info("cryptState setup: key=%s iv=%s encIV=%s nonce_prefix=%s",
-		hex.EncodeToString(cs.key[:]),
-		hex.EncodeToString(iv),
-		hex.EncodeToString(encIV[:]),
-		hex.EncodeToString(cs.nonce[:]))
+	if log.Enabled(log.LevelDebug) {
+		log.Debug("cryptState setup: key=%s iv=%s encIV=%s nonce_prefix=%s",
+			hex.EncodeToString(cs.key[:]),
+			hex.EncodeToString(iv),
+			hex.EncodeToString(encIV[:]),
+			hex.EncodeToString(cs.nonce[:]))
+	}
 
 	return nil
 }
@@ -302,8 +304,10 @@ func (c *Client) handleCryptSetup(buffer []byte) error {
 		c.cryptOut.setup(packet.Key, packet.ClientNonce)
 		c.cryptIn.setup(packet.Key, packet.ServerNonce)
 
-		// Also set up Mumble 1.5 native UDP crypto.
-		SetUDP15Crypto(packet.Key, packet.ClientNonce, packet.ServerNonce)
+		// Also set up per-client Mumble 1.5 native UDP crypto.
+		if err := c.setUDP15Crypto(packet.Key, packet.ClientNonce, packet.ServerNonce); err != nil {
+			return err
+		}
 
 		if wasInit {
 			log.Debug("CryptSetup updated (key rotation)")
@@ -316,17 +320,19 @@ func (c *Client) handleCryptSetup(buffer []byte) error {
 		log.Debug("received CryptSetup with incomplete fields, waiting for full key exchange")
 	}
 
-	if c.cryptOut.initialized && c.udpConn != nil && !c.udpActive {
-		// Only start UDP reader if 1.5 crypto is also ready.
-		if udp15Client != nil && udp15Client.initialized {
-			c.udpActive = true
-			log.Info("UDP crypto ready (1.5 native), starting UDP reader and pinger")
-			go c.udpReadRoutine()
-			go c.udpPingRoutine()
-		} else {
-			log.Info("legacy crypto ready, waiting for 1.5 crypto before starting UDP")
-		}
-	} else if c.cryptOut.initialized && c.udpConn == nil {
+	c.udpMu.Lock()
+	udpReady := c.udpCryptoOut != nil
+	startUDP := c.cryptOut.initialized && c.udpConn != nil && !c.udpActive && udpReady
+	if startUDP {
+		c.udpActive = true
+	}
+	noUDPConn := c.udpConn == nil
+	c.udpMu.Unlock()
+	if startUDP {
+		log.Info("UDP crypto ready (1.5 native), starting UDP reader and pinger")
+		go c.udpReadRoutine()
+		go c.udpPingRoutine()
+	} else if c.cryptOut.initialized && noUDPConn {
 		log.Warn("crypto ready but no UDP socket — audio will use TCP tunnel")
 	}
 
diff --git a/gumble/gumble/handlers.go b/gumble/gumble/handlers.go
index 3e87d99..5ac2c89 100644
--- a/gumble/gumble/handlers.go
+++ b/gumble/gumble/handlers.go
@@ -10,8 +10,8 @@ import (
 	"time"
 
 	"git.stormux.org/storm/barnard/gumble/gumble/MumbleProto"
-	"git.stormux.org/storm/barnard/log"
 	"git.stormux.org/storm/barnard/gumble/gumble/varint"
+	"git.stormux.org/storm/barnard/log"
 	"google.golang.org/protobuf/proto"
 )
 
@@ -231,25 +231,41 @@ func (c *Client) dispatchPLC(user *User, audioTarget byte, decoder AudioDecoder)
 
 // dispatchAudio sends an audio packet to all registered audio listeners.
 func (c *Client) dispatchAudio(user *User, packet *AudioPacket) {
-	c.volatile.Lock()
-	for item := c.Config.AudioListeners.head; item != nil; item = item.next {
-		c.volatile.Unlock()
+	listeners := &c.Config.AudioListeners
+	listeners.mu.Lock()
+	type delivery struct {
+		listener AudioListener
+		ch       chan *AudioPacket
+		new      bool
+	}
+	var deliveries []delivery
+	for item := listeners.head; item != nil; item = item.next {
 		ch := item.streams[user]
-		if ch == nil {
-			ch = make(chan *AudioPacket)
+		newStream := ch == nil
+		if newStream {
+			bufferSize := c.Config.Buffers
+			if bufferSize < 1 {
+				bufferSize = 1
+			}
+			ch = make(chan *AudioPacket, bufferSize)
 			item.streams[user] = ch
+		}
+		deliveries = append(deliveries, delivery{item.listener, ch, newStream})
+	}
+	listeners.mu.Unlock()
+
+	for _, delivery := range deliveries {
+		if delivery.new {
 			log.Debug("new audio stream from %s (session=%d)", user.Name, user.Session)
-			streamEvent := AudioStreamEvent{
-				Client: c,
-				User:   user,
-				C:      ch,
-			}
-			item.listener.OnAudioStream(&streamEvent)
+			delivery.listener.OnAudioStream(&AudioStreamEvent{Client: c, User: user, C: delivery.ch})
+		}
+		select {
+		case delivery.ch <- packet:
+		default:
+			// Never allow a slow listener to block protocol processing.
+			log.Debug("dropping buffered audio for slow listener (session=%d)", user.Session)
 		}
-		ch <- packet
-		c.volatile.Lock()
 	}
-	c.volatile.Unlock()
 }
 
 func (c *Client) handleAuthenticate(buffer []byte) error {
diff --git a/gumble/gumble/udp.go b/gumble/gumble/udp.go
index 22fb675..8c9a767 100644
--- a/gumble/gumble/udp.go
+++ b/gumble/gumble/udp.go
@@ -32,7 +32,9 @@ func (c *Client) startUDP() error {
 		return nil
 	}
 
+	c.udpMu.Lock()
 	c.udpConn = conn
+	c.udpMu.Unlock()
 	log.Info("UDP socket connected to %s", conn.RemoteAddr())
 	// The UDP reader and pinger will be started once CryptSetup is received.
 	return nil
@@ -44,15 +46,23 @@ func (c *Client) udpReadRoutine() {
 	log.Info("UDP reader started (1.5 native format)")
 	buf := make([]byte, maxUDPPacketSize)
 	var packetCount uint64
+	c.udpMu.RLock()
+	udpConn := c.udpConn
+	c.udpMu.RUnlock()
+	if udpConn == nil {
+		return
+	}
 	for {
-		n, addr, err := c.udpConn.ReadFromUDP(buf)
+		n, addr, err := udpConn.ReadFromUDP(buf)
 		if err != nil {
 			log.Warn("UDP read error (stopping reader): %v", err)
 			return
 		}
 		packetCount++
-		log.Info("UDP recv #%d: %d bytes from %s hex=%s",
-			packetCount, n, addr, hex.EncodeToString(buf[:n]))
+		if log.Enabled(log.LevelDebug) {
+			log.Debug("UDP recv #%d: %d bytes from %s hex=%s",
+				packetCount, n, addr, hex.EncodeToString(buf[:n]))
+		}
 		packet := make([]byte, n)
 		copy(packet, buf[:n])
 		c.HandleUDPPacket15(packet, packetCount)
@@ -79,8 +89,12 @@ func (c *Client) udpPingRoutine() {
 // sendUDPPing sends a Mumble 1.5 native UDP ping.
 // Uses standard protobuf varint encoding (not Mumble's custom varint).
 func (c *Client) sendUDPPing() {
-	cs := udp15Client
-	if cs == nil || !cs.initialized || c.udpConn == nil {
+	c.udpWriteMu.Lock()
+	defer c.udpWriteMu.Unlock()
+	c.udpMu.RLock()
+	cs, udpConn := c.udpCryptoOut, c.udpConn
+	c.udpMu.RUnlock()
+	if cs == nil || udpConn == nil {
 		return
 	}
 	// Type byte 0x01 = UDPPing, field 1 = timestamp (protobuf varint, milliseconds).
@@ -98,6 +112,5 @@ func (c *Client) sendUDPPing() {
 	if err != nil {
 		return
 	}
-	c.udpConn.Write(encrypted)
+	udpConn.Write(encrypted)
 }
-
diff --git a/gumble/gumble/udp15.go b/gumble/gumble/udp15.go
index e4e8f98..2a0d24c 100644
--- a/gumble/gumble/udp15.go
+++ b/gumble/gumble/udp15.go
@@ -3,8 +3,11 @@ package gumble
 import (
 	"bytes"
 	"crypto/aes"
+	"encoding/binary"
 	"encoding/hex"
 	"errors"
+	"math"
+	"sync"
 
 	"git.stormux.org/storm/barnard/gumble/gumble/varint"
 	"git.stormux.org/storm/barnard/log"
@@ -35,13 +38,14 @@ func pbEncodeVarint(buf []byte, v uint64) int {
 // and the number of bytes consumed (0 on error).
 func pbDecodeVarint(buf []byte) (uint64, int) {
 	var v uint64
-	var s uint
 	for i, b := range buf {
-		v |= uint64(b&0x7F) << s
+		if i == 10 || (i == 9 && b > 1) {
+			return 0, 0 // overflow
+		}
+		v |= uint64(b&0x7F) << (7 * i)
 		if b < 0x80 {
 			return v, i + 1
 		}
-		s += 7
 	}
 	return 0, 0 // truncated
 }
@@ -59,23 +63,16 @@ func pbDecodeVarint(buf []byte) (uint64, int) {
 // encodeUDPAudio builds a MumbleUDP.Audio protobuf message.
 // If session == 0, sender_session is omitted (used for outbound).
 // Uses standard protobuf varint encoding, not Mumble's custom varint.
-func encodeUDPAudio(session uint32, frameNumber uint32, opusData []byte, terminator bool) []byte {
+func encodeUDPAudio(target uint32, frameNumber uint64, opusData []byte, terminator bool) []byte {
 	var buf bytes.Buffer
 	var tmp [10]byte // max protobuf varint size
 
-	// Field 1: target = 0 (normal speech).  Always encoded so the server
-	// sees the oneof Header choice, matching the reference client.
+	// Field 1 selects the target header oneof.
 	n := pbEncodeVarint(tmp[:], uint64((1<<3)|0))
 	buf.Write(tmp[:n])
-	n = pbEncodeVarint(tmp[:], 0)
+	n = pbEncodeVarint(tmp[:], uint64(target))
 	buf.Write(tmp[:n])
 
-	if session != 0 {
-		n := pbEncodeVarint(tmp[:], uint64((3<<3)|0))
-		buf.Write(tmp[:n])
-		n = pbEncodeVarint(tmp[:], uint64(session))
-		buf.Write(tmp[:n])
-	}
 	n = pbEncodeVarint(tmp[:], uint64((4<<3)|0))
 	buf.Write(tmp[:n])
 	n = pbEncodeVarint(tmp[:], uint64(frameNumber))
@@ -99,7 +96,9 @@ func encodeUDPAudio(session uint32, frameNumber uint32, opusData []byte, termina
 
 // decodeUDPAudio parses a MumbleUDP.Audio protobuf message.
 // Uses standard protobuf varint decoding, not Mumble's custom varint.
-func decodeUDPAudio(data []byte) (session uint32, frameNumber uint32, opusData []byte, terminator bool) {
+func decodeUDPAudio(data []byte) (session uint32, frameNumber uint64, opusData []byte, terminator bool, context uint32, position *[3]float32, volumeAdjustment float32) {
+	var positionValues [3]float32
+	positionCount := 0
 	pos := 0
 	for pos < len(data) {
 		key, n := pbDecodeVarint(data[pos:])
@@ -118,10 +117,12 @@ func decodeUDPAudio(data []byte) (session uint32, frameNumber uint32, opusData [
 			}
 			pos += n
 			switch fieldNum {
+			case 2:
+				context = uint32(val)
 			case 3:
 				session = uint32(val)
 			case 4:
-				frameNumber = uint32(val)
+				frameNumber = val
 			case 16:
 				terminator = val != 0
 			}
@@ -131,18 +132,43 @@ func decodeUDPAudio(data []byte) (session uint32, frameNumber uint32, opusData [
 				return
 			}
 			pos += n
-			if int(length) > len(data)-pos {
+			if length > uint64(len(data)-pos) {
 				return
 			}
+			end := pos + int(length)
 			if fieldNum == 5 {
-				opusData = make([]byte, length)
-				copy(opusData, data[pos:pos+int(length)])
+				opusData = append(opusData[:0], data[pos:end]...)
+			} else if fieldNum == 6 && length == 12 {
+				for i := range positionValues {
+					positionValues[i] = math.Float32frombits(binary.LittleEndian.Uint32(data[pos+i*4:]))
+				}
+				positionCount = 3
 			}
-			pos += int(length)
+			pos = end
+		case 1:
+			if len(data)-pos < 8 {
+				return
+			}
+			pos += 8
+		case 5:
+			if len(data)-pos < 4 {
+				return
+			}
+			value := math.Float32frombits(binary.LittleEndian.Uint32(data[pos:]))
+			if fieldNum == 6 && positionCount < len(positionValues) {
+				positionValues[positionCount] = value
+				positionCount++
+			} else if fieldNum == 7 {
+				volumeAdjustment = value
+			}
+			pos += 4
 		default:
-			return // unknown wire type, bail
+			return // invalid wire type
 		}
 	}
+	if positionCount == len(positionValues) {
+		position = &positionValues
+	}
 	return
 }
 
@@ -160,6 +186,7 @@ const (
 
 // cryptState15 implements Mumble 1.5 native UDP encryption.
 type cryptState15 struct {
+	mu          sync.Mutex
 	key         [16]byte
 	encryptIV   [16]byte
 	decryptIV   [16]byte
@@ -170,6 +197,8 @@ type cryptState15 struct {
 // setup15 initializes 1.5-style crypto from CryptSetup.
 // clientNonce → encryptIV, serverNonce → decryptIV.
 func (cs *cryptState15) setup15(key, clientNonce, serverNonce []byte) error {
+	cs.mu.Lock()
+	defer cs.mu.Unlock()
 	if len(key) != 16 || len(clientNonce) != 16 || len(serverNonce) != 16 {
 		return errors.New("gumble: invalid crypto key/nonce")
 	}
@@ -178,10 +207,12 @@ func (cs *cryptState15) setup15(key, clientNonce, serverNonce []byte) error {
 	copy(cs.decryptIV[:], serverNonce)
 	cs.initialized = true
 
-	log.Info("cryptState15 setup: key=%s encryptIV=%s decryptIV=%s",
-		hex.EncodeToString(cs.key[:]),
-		hex.EncodeToString(cs.encryptIV[:]),
-		hex.EncodeToString(cs.decryptIV[:]))
+	if log.Enabled(log.LevelDebug) {
+		log.Debug("cryptState15 setup: key=%s encryptIV=%s decryptIV=%s",
+			hex.EncodeToString(cs.key[:]),
+			hex.EncodeToString(cs.encryptIV[:]),
+			hex.EncodeToString(cs.decryptIV[:]))
+	}
 
 	return nil
 }
@@ -189,6 +220,8 @@ func (cs *cryptState15) setup15(key, clientNonce, serverNonce []byte) error {
 // encrypt15 encrypts plaintext for Mumble 1.5 native UDP.
 // Returns [iv_byte(1)][tag(3)][ciphertext].
 func (cs *cryptState15) encrypt15(plaintext []byte) ([]byte, error) {
+	cs.mu.Lock()
+	defer cs.mu.Unlock()
 	if !cs.initialized {
 		return nil, errors.New("gumble: crypto not initialized")
 	}
@@ -210,6 +243,8 @@ func (cs *cryptState15) encrypt15(plaintext []byte) ([]byte, error) {
 // decrypt15 decrypts a Mumble 1.5 native UDP packet.
 // Matches wumble's decrypt: advances IV when decrypt_iv[0]+1 == iv_byte.
 func (cs *cryptState15) decrypt15(packet []byte) ([]byte, error) {
+	cs.mu.Lock()
+	defer cs.mu.Unlock()
 	if !cs.initialized {
 		return nil, errors.New("gumble: crypto not initialized")
 	}
@@ -309,8 +344,6 @@ func backupIV(iv []byte) {
 	}
 }
 
-
-
 // ---------------------------------------------------------------------------
 // OCB variant for Mumble 1.5 native UDP.
 // Matches the implementation in Wumble's crypt_state.cr.
@@ -480,70 +513,46 @@ func xorBytes(dst, a, b []byte) {
 	}
 }
 
-// ---------------------------------------------------------------------------
-// Global 1.5 crypto state.
-// ---------------------------------------------------------------------------
-
-var udp15Client *cryptState15
-var udp15Server *cryptState15
-
-// SetUDP15Crypto installs the 1.5 native UDP crypto state from CryptSetup.
-// udp15Client: encrypts with client_nonce (outbound).
-// udp15Server: decrypts with server_nonce (inbound).
-func SetUDP15Crypto(key, clientNonce, serverNonce []byte) {
-	csClient := &cryptState15{}
-	if err := csClient.setup15(key, clientNonce, serverNonce); err != nil {
-		log.Error("SetUDP15Crypto client: %v", err)
-		return
+// setUDP15Crypto installs per-client 1.5 UDP crypto state from CryptSetup.
+func (c *Client) setUDP15Crypto(key, clientNonce, serverNonce []byte) error {
+	outbound := &cryptState15{}
+	if err := outbound.setup15(key, clientNonce, serverNonce); err != nil {
+		return err
 	}
-	udp15Client = csClient
-
-	// Server state: we only use decryptIV (to decrypt server→client packets).
-	// The server encrypts with server_nonce, so our decryptIV must be server_nonce.
-	csServer := &cryptState15{}
-	copy(csServer.key[:], key)
-	copy(csServer.decryptIV[:], serverNonce)
-	csServer.initialized = true
-	udp15Server = csServer
-
+	inbound := &cryptState15{}
+	// Server-to-client packets use serverNonce as decryptIV.
+	if err := inbound.setup15(key, clientNonce, serverNonce); err != nil {
+		return err
+	}
+	c.udpWriteMu.Lock()
+	c.udpMu.Lock()
+	c.udpCryptoOut = outbound
+	c.udpCryptoIn = inbound
+	c.udpFrameNumber = 0
+	c.udpMu.Unlock()
+	c.udpWriteMu.Unlock()
 	log.Info("Mumble 1.5 native UDP crypto initialized")
-}
-
-// ---------------------------------------------------------------------------
-// Frame number tracking.
-// ---------------------------------------------------------------------------
-
-var udp15FrameNumber uint32
-
-// nextFrameNumber returns the next frame number for outbound 1.5 UDP audio.
-func nextFrameNumber() uint32 {
-	n := udp15FrameNumber
-	udp15FrameNumber++
-	return n
+	return nil
 }
 
 // ---------------------------------------------------------------------------
 // WriteAudioUDP15 writes an encrypted audio packet using Mumble 1.5 native UDP.
 // Returns true if sent, false if TCP should be used.
-func (c *Client) WriteAudioUDP15(data []byte, final bool) (bool, error) {
-	cs := udp15Client
-	if cs == nil || !cs.initialized {
+func (c *Client) WriteAudioUDP15(target uint32, data []byte, final bool) (bool, error) {
+	// Encryption and socket writes must remain ordered: otherwise a later
+	// packet can reach the server before the packet with the preceding IV.
+	c.udpWriteMu.Lock()
+	defer c.udpWriteMu.Unlock()
+	c.udpMu.Lock()
+	cs, udpConn := c.udpCryptoOut, c.udpConn
+	frameNum := c.udpFrameNumber
+	c.udpFrameNumber++
+	c.udpMu.Unlock()
+	if cs == nil || udpConn == nil {
 		return false, nil
 	}
 
-	// Snapshot udpConn to avoid race with disconnect cleanup nil'ing it.
-	udpConn := c.udpConn
-	if udpConn == nil {
-		return false, nil
-	}
-
-	frameNum := nextFrameNumber()
-
-	// Build MumbleUDP.Audio: type byte 0x00 + protobuf.
-	// Matches reference client: 0x00 + target=0 + frame_number + opus_data [+ is_terminator]
-	payload := append([]byte{0x00}, encodeUDPAudio(0, frameNum, data, final)...)
-
-	// Encrypt with 1.5 format.
+	payload := append([]byte{0x00}, encodeUDPAudio(target, frameNum, data, final)...)
 	encrypted, err := cs.encrypt15(payload)
 	if err != nil {
 		log.Error("UDP15 encrypt failed: %v", err)
@@ -562,21 +571,20 @@ func (c *Client) WriteAudioUDP15(data []byte, final bool) (bool, error) {
 }
 
 // HandleUDPPacket15 processes an incoming Mumble 1.5 native UDP packet.
-var firstUDP15Recv bool
-
 func (c *Client) HandleUDPPacket15(packet []byte, pktNum uint64) {
 	if len(packet) < udp15HeaderSize {
 		log.Warn("UDP15 #%d: packet too short (%d bytes)", pktNum, len(packet))
 		return
 	}
 
-	if !firstUDP15Recv {
-		firstUDP15Recv = true
-		log.Info("UDP15 #%d: first packet received! hex=%s", pktNum, hex.EncodeToString(packet))
+	if !c.udpFirstRecv.Swap(true) && log.Enabled(log.LevelDebug) {
+		log.Debug("UDP15 #%d: first packet received! hex=%s", pktNum, hex.EncodeToString(packet))
 	}
 
-	cs := udp15Server
-	if cs == nil || !cs.initialized {
+	c.udpMu.RLock()
+	cs := c.udpCryptoIn
+	c.udpMu.RUnlock()
+	if cs == nil {
 		log.Warn("UDP15 #%d: crypto not initialized", pktNum)
 		return
 	}
@@ -587,7 +595,7 @@ func (c *Client) HandleUDPPacket15(packet []byte, pktNum uint64) {
 		return
 	}
 
-	log.Info("UDP15 #%d: decrypt OK, plaintext_len=%d", pktNum, len(plaintext))
+	log.Debug("UDP15 #%d: decrypt OK, plaintext_len=%d", pktNum, len(plaintext))
 
 	// Check type byte (0x00 = Audio, 0x01 = Ping)
 	if len(plaintext) < 1 {
@@ -604,8 +612,8 @@ func (c *Client) HandleUDPPacket15(packet []byte, pktNum uint64) {
 
 	// MumbleUDP.Audio protobuf format (1.5 native).
 	if msgType == 0x00 {
-		session, frameNum, opusData, terminator := decodeUDPAudio(plaintext)
-		c.dispatchOpus15(pktNum, session, int64(frameNum), opusData, terminator)
+		session, frameNum, opusData, terminator, context, position, volumeAdjustment := decodeUDPAudio(plaintext)
+		c.dispatchOpus15(pktNum, session, int64(frameNum), opusData, terminator, context, position, volumeAdjustment)
 		return
 	}
 
@@ -620,7 +628,7 @@ func (c *Client) HandleUDPPacket15(packet []byte, pktNum uint64) {
 
 // dispatchOpus15 processes a decoded MumbleUDP.Audio frame and dispatches
 // the decoded PCM to audio listeners.
-func (c *Client) dispatchOpus15(pktNum uint64, session uint32, frameNum int64, opusData []byte, terminator bool) {
+func (c *Client) dispatchOpus15(pktNum uint64, session uint32, frameNum int64, opusData []byte, terminator bool, context uint32, position *[3]float32, volumeAdjustment float32) {
 	if len(opusData) == 0 && !terminator {
 		log.Info("UDP15 #%d: no opus data (session=%d frame=%d), skipping", pktNum, session, frameNum)
 		return
@@ -654,7 +662,7 @@ func (c *Client) dispatchOpus15(pktNum uint64, session uint32, frameNum int64, o
 		return
 	}
 
-	c.decodeAndDispatch(pktNum, user, decoder, frameNum, opusData)
+	c.decodeAndDispatch(pktNum, user, decoder, frameNum, opusData, context, position, volumeAdjustment)
 }
 
 // handleLegacyUDPVoice parses the legacy UDPVoice format (type byte 0x80)
@@ -699,11 +707,11 @@ func (c *Client) handleLegacyUDPVoice(pktNum uint64, data []byte) {
 	log.Info("UDP15 #%d: legacy voice session=%d seq=%d opus_len=%d term=%v",
 		pktNum, session, seq, len(opusData), terminator)
 
-	c.dispatchOpus15(pktNum, uint32(session), seq, opusData, terminator)
+	c.dispatchOpus15(pktNum, uint32(session), seq, opusData, terminator, 0, nil, 0)
 }
 
 // decodeAndDispatch decodes an Opus frame and dispatches PCM to audio listeners.
-func (c *Client) decodeAndDispatch(pktNum uint64, user *User, decoder AudioDecoder, frameNum int64, opusData []byte) {
+func (c *Client) decodeAndDispatch(pktNum uint64, user *User, decoder AudioDecoder, frameNum int64, opusData []byte, context uint32, position *[3]float32, volumeAdjustment float32) {
 	// Detect sequence gaps.
 	if user.audioSequenceValid {
 		gap := frameNum - user.audioSequence
@@ -732,14 +740,19 @@ func (c *Client) decodeAndDispatch(pktNum uint64, user *User, decoder AudioDecod
 		return
 	}
 
-	log.Info("UDP15 #%d: Opus OK for %s, pcm_samples=%d", pktNum, user.Name, len(pcm))
+	log.Debug("UDP15 #%d: Opus OK for %s, pcm_samples=%d", pktNum, user.Name, len(pcm))
 
 	event := AudioPacket{
-		Client:      c,
-		Sender:      user,
-		Target:      &VoiceTarget{ID: 0},
-		Sequence:    frameNum,
-		AudioBuffer: AudioBuffer(pcm),
+		Client:           c,
+		Sender:           user,
+		Target:           &VoiceTarget{ID: context},
+		Sequence:         frameNum,
+		AudioBuffer:      AudioBuffer(pcm),
+		VolumeAdjustment: volumeAdjustment,
+	}
+	if position != nil {
+		event.HasPosition = true
+		event.X, event.Y, event.Z = position[0], position[1], position[2]
 	}
 	c.dispatchAudio(user, &event)
 }
diff --git a/gumble/gumble/udp15_test.go b/gumble/gumble/udp15_test.go
index f23867c..e3ea5ce 100644
--- a/gumble/gumble/udp15_test.go
+++ b/gumble/gumble/udp15_test.go
@@ -2,7 +2,9 @@ package gumble
 
 import (
 	"bytes"
+	"encoding/binary"
 	"encoding/hex"
+	"math"
 	"testing"
 )
 
@@ -40,9 +42,9 @@ func TestOCB15RoundTrip(t *testing.T) {
 	}{
 		{"empty", []byte{}},
 		{"1 byte", []byte{0x41}},
-		{"15 bytes", []byte("hello world 1234")},   // 15
-		{"16 bytes", []byte("hello world 12345")},   // exactly 1 block
-		{"17 bytes", []byte("hello world 123456")},  // 1 full + 1 partial
+		{"15 bytes", []byte("hello world 1234")},              // 15
+		{"16 bytes", []byte("hello world 12345")},             // exactly 1 block
+		{"17 bytes", []byte("hello world 123456")},            // 1 full + 1 partial
 		{"32 bytes", []byte("hello world 12345678901234567")}, // exactly 2 blocks
 		{"33 bytes", []byte("hello world 123456789012345678")},
 		{"100 bytes", bytes.Repeat([]byte{0x41}, 100)},
@@ -140,13 +142,13 @@ func TestUDPAudioProtobuf(t *testing.T) {
 	}
 
 	for _, tt := range tests {
-		encoded := encodeUDPAudio(tt.session, tt.frameNumber, tt.opusData, tt.terminator)
-		session, frameNum, opusData, terminator := decodeUDPAudio(encoded)
+		encoded := encodeUDPAudio(uint32(tt.session), uint64(tt.frameNumber), tt.opusData, tt.terminator)
+		session, frameNum, opusData, terminator, _, _, _ := decodeUDPAudio(encoded)
 
-		if session != tt.session {
-			t.Errorf("session: got %d, want %d", session, tt.session)
+		if session != 0 {
+			t.Errorf("outbound packet unexpectedly contains session %d", session)
 		}
-		if frameNum != tt.frameNumber {
+		if frameNum != uint64(tt.frameNumber) {
 			t.Errorf("frameNumber: got %d, want %d", frameNum, tt.frameNumber)
 		}
 		if !bytes.Equal(opusData, tt.opusData) {
@@ -158,6 +160,39 @@ func TestUDPAudioProtobuf(t *testing.T) {
 	}
 }
 
+func TestUDPAudioProtobufIncomingFields(t *testing.T) {
+	var packet bytes.Buffer
+	writeVarint := func(v uint64) {
+		var buf [10]byte
+		n := pbEncodeVarint(buf[:], v)
+		packet.Write(buf[:n])
+	}
+	writeVarint(2<<3 | 0) // context
+	writeVarint(3)
+	writeVarint(3<<3 | 0) // sender_session
+	writeVarint(123)
+	writeVarint(4<<3 | 0) // frame_number
+	writeVarint(1 << 32)
+	writeVarint(5<<3 | 2) // opus_data
+	writeVarint(2)
+	packet.Write([]byte{0xaa, 0xbb})
+	writeVarint(6<<3 | 2) // packed positional_data
+	writeVarint(12)
+	for _, f := range []uint32{math.Float32bits(1), math.Float32bits(2), math.Float32bits(3)} {
+		var buf [4]byte
+		binary.LittleEndian.PutUint32(buf[:], f)
+		packet.Write(buf[:])
+	}
+
+	session, frame, opusData, terminator, context, position, _ := decodeUDPAudio(packet.Bytes())
+	if session != 123 || frame != 1<<32 || !bytes.Equal(opusData, []byte{0xaa, 0xbb}) || terminator || context != 3 {
+		t.Fatalf("decoded unexpected audio: session=%d frame=%d opus=%x terminator=%v context=%d", session, frame, opusData, terminator, context)
+	}
+	if position == nil || *position != [3]float32{1, 2, 3} {
+		t.Fatalf("position = %v, want [1 2 3]", position)
+	}
+}
+
 func mustDecodeHex(s string) []byte {
 	b, err := hex.DecodeString(s)
 	if err != nil {
diff --git a/gumble/gumbleopenal/stream.go b/gumble/gumbleopenal/stream.go
index 88eb976..b7ebdb0 100644
--- a/gumble/gumbleopenal/stream.go
+++ b/gumble/gumbleopenal/stream.go
@@ -536,7 +536,7 @@ func (s *Stream) processAudioPacket(packet *gumble.AudioPacket, user *gumble.Use
 	rawPtr := 0
 	if isStereo {
 		// Process stereo samples as pairs
-		for i := 0; i < samples*2; i += 2 {
+		for i := 0; i < samples; i += 2 {
 			// Process left channel with saturation protection
 			sample := packet.AudioBuffer[i]
 			if boost > 1 {
diff --git a/log/log.go b/log/log.go
index c73aea6..4003911 100644
--- a/log/log.go
+++ b/log/log.go
@@ -7,6 +7,7 @@ import (
 	"io"
 	"os"
 	"sync"
+	"sync/atomic"
 	"time"
 )
 
@@ -40,10 +41,16 @@ type Logger interface {
 	Log(level Level, format string, args ...interface{})
 }
 
-var (
-	mu     sync.Mutex
-	logger Logger = &nopLogger{}
-)
+type loggerState struct {
+	logger Logger
+	level  Level
+}
+
+var logger atomic.Pointer[loggerState]
+
+func init() {
+	logger.Store(&loggerState{logger: &nopLogger{}, level: LevelError + 1})
+}
 
 type nopLogger struct{}
 
@@ -51,21 +58,28 @@ func (n *nopLogger) Log(level Level, format string, args ...interface{}) {}
 
 // SetLogger sets the destination for log messages. Pass nil to disable.
 func SetLogger(l Logger) {
-	mu.Lock()
-	defer mu.Unlock()
+	state := &loggerState{logger: l, level: LevelDebug}
 	if l == nil {
-		logger = &nopLogger{}
-	} else {
-		logger = l
+		state.logger = &nopLogger{}
+		state.level = LevelError + 1
+	} else if writer, ok := l.(*WriterLogger); ok {
+		state.level = writer.level
 	}
+	logger.Store(state)
+}
+
+// Enabled reports whether messages at level will be emitted. Callers should
+// use it to avoid computing expensive log arguments when logging is disabled.
+func Enabled(level Level) bool {
+	return level >= logger.Load().level
 }
 
 // WriterLogger is a simple Logger that writes to an io.Writer.
 type WriterLogger struct {
-	mu     sync.Mutex
-	w      io.Writer
-	level  Level
-	buf    []byte
+	mu    sync.Mutex
+	w     io.Writer
+	level Level
+	buf   []byte
 }
 
 // NewWriterLogger creates a logger that writes to w, filtering below level.
@@ -88,29 +102,29 @@ func (wl *WriterLogger) Log(level Level, format string, args ...interface{}) {
 }
 
 func Debug(format string, args ...interface{}) {
-	mu.Lock()
-	l := logger
-	mu.Unlock()
-	l.Log(LevelDebug, format, args...)
+	state := logger.Load()
+	if LevelDebug >= state.level {
+		state.logger.Log(LevelDebug, format, args...)
+	}
 }
 
 func Info(format string, args ...interface{}) {
-	mu.Lock()
-	l := logger
-	mu.Unlock()
-	l.Log(LevelInfo, format, args...)
+	state := logger.Load()
+	if LevelInfo >= state.level {
+		state.logger.Log(LevelInfo, format, args...)
+	}
 }
 
 func Warn(format string, args ...interface{}) {
-	mu.Lock()
-	l := logger
-	mu.Unlock()
-	l.Log(LevelWarn, format, args...)
+	state := logger.Load()
+	if LevelWarn >= state.level {
+		state.logger.Log(LevelWarn, format, args...)
+	}
 }
 
 func Error(format string, args ...interface{}) {
-	mu.Lock()
-	l := logger
-	mu.Unlock()
-	l.Log(LevelError, format, args...)
+	state := logger.Load()
+	if LevelError >= state.level {
+		state.logger.Log(LevelError, format, args...)
+	}
 }