diff --git a/agent/history.go b/agent/history.go
index 2b5d619..5925193 100644
--- a/agent/history.go
+++ b/agent/history.go
@@ -8,8 +8,6 @@ import (
 	"os"
 	"slices"
 	"strings"
-	"time"
-	"strconv"
 
 	"ollie/backend"
 )
@@ -653,9 +651,12 @@ func (s *History) contextDebug() string {
 	return sb.String()
 }
 
-// NewResponseID generates a unique identifier for a single assistant response.
+// NewResponseID generates a UUIDv4 for a single assistant response.
 func NewResponseID() string {
-	b := make([]byte, 3)
+	b := make([]byte, 16)
 	rand.Read(b) //nolint:errcheck
-		return "resp_" + strconv.FormatInt(time.Now().UnixNano(), 10) + "_" + fmt.Sprintf("%06x", b)
+	b[6] = (b[6] & 0x0f) | 0x40 // version 4
+	b[8] = (b[8] & 0x3f) | 0x80 // variant 10xx
+	return fmt.Sprintf("%08x-%04x-%04x-%04x-%012x",
+		b[0:4], b[4:6], b[6:8], b[8:10], b[10:16])
 }