fix: fixed race condition in clone

encoder.go

@@ -281,10 +281,6 @@ var _jsonPool = sync.Pool{New: func() interface{} {
 	return &jsonEncoder{}
 }}
 
-func getJSONEncoder() *jsonEncoder {
-	return _jsonPool.Get().(*jsonEncoder)
-}
-
 func putJSONEncoder(enc *jsonEncoder) {
 	if enc.reflectBuf != nil {
 		enc.reflectBuf.Free()
@@ -546,7 +542,7 @@ func (enc *jsonEncoder) Clone() zapcore.Encoder {
 }
 
 func (enc *jsonEncoder) clone() *jsonEncoder {
-	clone := getJSONEncoder()
+	clone := &jsonEncoder{}
 	clone.EncoderConfig = enc.EncoderConfig
 	clone.spaced = enc.spaced
 	clone.openNamespaces = enc.openNamespaces

encoder_concurrency_test.go

@@ -0,0 +1,32 @@
+package logging
+
+import (
+	"io"
+	"sync"
+	"testing"
+
+	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
+)
+
+// Regression test for a data race in jsonEncoder.clone(): getJSONEncoder()
+// hands out a pooled *jsonEncoder that a concurrent clone() call is still
+// mutating. Triggered by concurrent Logger.With + log emission on the same
+// base logger (the pattern loopagent's Thread.log exercised). Run with -race.
+func TestEncoderConcurrentWithAndLog(t *testing.T) {
+	core := zapcore.NewCore(NewEncoder(1, false), zapcore.AddSync(io.Discard), zap.DebugLevel)
+	base := zap.New(core).Named("base").With(zap.String("thread_id", "t-1"), zap.String("agent_id", "a-1"))
+
+	var wg sync.WaitGroup
+	for i := 0; i < 8; i++ {
+		wg.Add(1)
+		go func(n int) {
+			defer wg.Done()
+			for j := 0; j < 2000; j++ {
+				derived := base.With(zap.Int("n", n))
+				derived.Info("hello", zap.String("j", string(rune(j))))
+			}
+		}(i)
+	}
+	wg.Wait()
+}