diff --git a/metropolis/pkg/logtree/zap.go b/metropolis/pkg/logtree/zap.go
new file mode 100644
index 0000000..7790cd0
--- /dev/null
+++ b/metropolis/pkg/logtree/zap.go
@@ -0,0 +1,141 @@
+package logtree
+
+import (
+	"encoding/json"
+	"fmt"
+	"strconv"
+	"strings"
+	"time"
+
+	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
+
+	"source.monogon.dev/metropolis/pkg/logbuffer"
+)
+
+// Zapify turns a LeveledLogger into a zap.Logger which pipes its output into the
+// LeveledLogger. The message, severity and caller are carried over. Extra fields
+// are appended as JSON to the end of the log line.
+func Zapify(logger LeveledLogger, minimumLevel zapcore.Level) *zap.Logger {
+	p, ok := logger.(*leveledPublisher)
+	if !ok {
+		// Fail fast, as this is a programming error.
+		panic("Expected *leveledPublisher in LeveledLogger from supervisor")
+	}
+
+	ec := zapcore.EncoderConfig{
+		MessageKey:   "message",
+		LevelKey:     "level",
+		TimeKey:      "time",
+		CallerKey:    "caller",
+		EncodeLevel:  zapcore.LowercaseLevelEncoder,
+		EncodeTime:   zapcore.EpochTimeEncoder,
+		EncodeCaller: zapcore.ShortCallerEncoder,
+	}
+	s := zapSink{
+		publisher: p,
+	}
+	s.buffer = logbuffer.NewLineBuffer(4096, s.consumeLine)
+	zc := zapcore.NewCore(zapcore.NewJSONEncoder(ec), s.buffer, minimumLevel)
+	return zap.New(zc, zap.AddCaller())
+}
+
+type zapSink struct {
+	publisher *leveledPublisher
+	buffer    *logbuffer.LineBuffer
+}
+
+func (z *zapSink) consumeLine(l *logbuffer.Line) {
+	ze, err := parseZapJSON(l.Data)
+	if err != nil {
+		z.publisher.Warningf("failed to parse zap JSON: %v: %q", err, l.Data)
+		return
+	}
+	message := ze.message
+	if len(ze.extra) > 0 {
+		message += " " + ze.extra
+	}
+	e := &entry{
+		origin: z.publisher.node.dn,
+		leveled: &LeveledPayload{
+			timestamp: ze.time,
+			severity:  ze.severity,
+			messages:  []string{message},
+			file:      ze.file,
+			line:      ze.line,
+		},
+	}
+	z.publisher.node.tree.journal.append(e)
+	z.publisher.node.tree.journal.notify(e)
+}
+
+type zapEntry struct {
+	message  string
+	severity Severity
+	time     time.Time
+	file     string
+	line     int
+	extra    string
+}
+
+func parseZapJSON(s string) (*zapEntry, error) {
+	entry := make(map[string]any)
+	if err := json.Unmarshal([]byte(s), &entry); err != nil {
+		return nil, fmt.Errorf("invalid JSON: %v", err)
+	}
+	message, ok := entry["message"].(string)
+	if !ok {
+		return nil, fmt.Errorf("no message field")
+	}
+	level, ok := entry["level"].(string)
+	if !ok {
+		return nil, fmt.Errorf("no level field")
+	}
+	t, ok := entry["time"].(float64)
+	if !ok {
+		return nil, fmt.Errorf("no time field")
+	}
+	caller, ok := entry["caller"].(string)
+	if !ok {
+		return nil, fmt.Errorf("no caller field")
+	}
+
+	callerParts := strings.Split(caller, ":")
+	if len(callerParts) != 2 {
+		return nil, fmt.Errorf("invalid caller")
+	}
+	callerDirFile := strings.Split(callerParts[0], "/")
+	callerFile := callerDirFile[len(callerDirFile)-1]
+	callerLineS := callerParts[1]
+	callerLine, _ := strconv.Atoi(callerLineS)
+
+	var severity Severity
+	switch level {
+	case "warn":
+		severity = WARNING
+	case "error", "dpanic", "panic", "fatal":
+		severity = ERROR
+	default:
+		severity = INFO
+	}
+
+	secs := int64(t)
+	nsecs := int64((t - float64(secs)) * 1e9)
+
+	delete(entry, "message")
+	delete(entry, "level")
+	delete(entry, "time")
+	delete(entry, "caller")
+	extra := []byte{}
+	if len(entry) > 0 {
+		extra, _ = json.Marshal(entry)
+	}
+	return &zapEntry{
+		message:  message,
+		severity: severity,
+		time:     time.Unix(secs, nsecs),
+		file:     callerFile,
+		line:     callerLine,
+		extra:    string(extra),
+	}, nil
+}