diff --git a/contract/plugin.go b/contract/plugin.go
index 9105256..9bc8ea0 100644
--- a/contract/plugin.go
+++ b/contract/plugin.go
@@ -24,7 +24,8 @@ type Plugin struct {
 	conn            net.Conn                              // the underlying unix sock file connection
 	pending         map[uint64]chan isFSMToPlugin_Payload // the outstanding requests from the contract
 	requestContract map[uint64]*Contract                  // maps request IDs to their contract context for concurrent operations
-	l               sync.Mutex                            // thread safety
+	l               sync.Mutex                            // thread safety for pending/requestContract maps
+	writeMu         sync.Mutex                            // thread safety for concurrent writes to the socket connection
 	config          Config                                // general app config
 }
 
@@ -266,6 +267,12 @@ func (p *Plugin) sendLengthPrefixed(bz []byte) *PluginError {
 	// create the length prefix (4 bytes, big endian)
 	lengthPrefix := make([]byte, 4)
 	binary.BigEndian.PutUint32(lengthPrefix, uint32(len(bz)))
+	// serialize writes: ListenForInbound() spawns a goroutine per inbound message, and each
+	// can independently write to the shared connection (either as a direct FSM response or
+	// via a nested StateRead/StateWrite call). Without this lock, concurrent writers can
+	// interleave mid-message and corrupt the length-prefixed framing on the wire.
+	p.writeMu.Lock()
+	defer p.writeMu.Unlock()
 	// write the message (length prefixed)
 	if _, er := p.conn.Write(append(lengthPrefix, bz...)); er != nil {
 		return ErrFailedPluginWrite(er)