diff --git a/backend/controller/remoteBrowser.go b/backend/controller/remoteBrowser.go
index 7e91eb06..038bbb2e 100644
--- a/backend/controller/remoteBrowser.go
+++ b/backend/controller/remoteBrowser.go
@@ -14,7 +14,6 @@ import (
 	"math/rand"
 	"net/http"
 	"net/url"
-	"strings"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -927,8 +926,10 @@ func (m *RemoteBrowserController) ServeVictim(g *gin.Context) {
 			m.Logger.Debugw(evt.Message, "campaign_id", campaignID, "recipient_id", recipientID)
 			// persist the script log line as a recipient event so it shows in
 			// the campaign timeline for this recipient. runner diagnostics are
-			// only for the editor panel and are kept out of the timeline.
-			if !isInternalRunnerLog(evt.Message) {
+			// only for the editor panel and are kept out of the timeline. the
+			// runner marks its own diagnostics Internal, so classification does
+			// not depend on the message text.
+			if !evt.Internal {
 				logMsg := evt.Message
 				if evt.Data != nil {
 					if b, mErr := json.Marshal(evt.Data); mErr == nil {
@@ -1973,30 +1974,6 @@ func (m *RemoteBrowserController) saveCaptureEvent(
 	}
 }
 
-// internalRunnerLogPrefixes tag the log lines the runner emits about its own
-// operation. They help while testing a script in the editor but are noise in a
-// recipient timeline, so they are not saved as recipient events.
-var internalRunnerLogPrefixes = []string{
-	"[session]",
-	"[chrome]",
-	"[dbg]",
-	"[screenshot]",
-	"[domDump]",
-	"[waitForEvent]",
-	"[stream]",
-}
-
-// isInternalRunnerLog reports whether msg is a runner diagnostic rather than a
-// line the script author wrote with log().
-func isInternalRunnerLog(msg string) bool {
-	for _, p := range internalRunnerLogPrefixes {
-		if strings.HasPrefix(msg, p) {
-			return true
-		}
-	}
-	return false
-}
-
 func (m *RemoteBrowserController) saveInfoEvent(
 	ctx context.Context,
 	campaignID *uuid.UUID,
diff --git a/backend/remotebrowser/emitter.go b/backend/remotebrowser/emitter.go
index 145f4fb2..a3f3b6c1 100644
--- a/backend/remotebrowser/emitter.go
+++ b/backend/remotebrowser/emitter.go
@@ -15,6 +15,13 @@ type RunEvent struct {
 	Message string `json:"message,omitempty"` // for type=log/error/info
 	Data    any    `json:"data,omitempty"`    // for type=log: optional second arg from log(msg, data)
 	Time    string `json:"time"`
+	// Internal marks a runner diagnostic (session, chrome, capture, frame, ...)
+	// as opposed to a line the script author wrote with log(). Only script logs
+	// are recorded on the recipient timeline; internal logs stay in the editor
+	// panel. This is set by the runner, never derived from the message text, so
+	// a log line whose text happens to start with a reserved word is classified
+	// by where it came from, not by what it says.
+	Internal bool `json:"internal,omitempty"`
 }
 
 // channelEmitter sends events to a buffered channel. All methods are safe to
@@ -36,11 +43,24 @@ func (e *channelEmitter) emit(key string, value any) {
 	})
 }
 
+// log emits a runner diagnostic. These show in the editor panel but are kept
+// off the recipient timeline. Every non script caller in the runner uses this.
 func (e *channelEmitter) log(msg string, data ...any) {
+	e.sendLog(msg, true, data...)
+}
+
+// scriptLog emits a line the automation script author wrote with log(). These
+// are recorded on the recipient timeline. Only the goja log() binding uses this.
+func (e *channelEmitter) scriptLog(msg string, data ...any) {
+	e.sendLog(msg, false, data...)
+}
+
+func (e *channelEmitter) sendLog(msg string, internal bool, data ...any) {
 	evt := RunEvent{
-		Type:    "log",
-		Message: msg,
-		Time:    time.Now().UTC().Format(time.RFC3339Nano),
+		Type:     "log",
+		Message:  msg,
+		Internal: internal,
+		Time:     time.Now().UTC().Format(time.RFC3339Nano),
 	}
 	if len(data) > 0 {
 		evt.Data = data[0]
diff --git a/backend/remotebrowser/runner.go b/backend/remotebrowser/runner.go
index a3c831e1..7a5d36e8 100644
--- a/backend/remotebrowser/runner.go
+++ b/backend/remotebrowser/runner.go
@@ -486,9 +486,9 @@ func (r *Runner) Run(ctx context.Context) error {
 	vm.Set("log", func(call goja.FunctionCall) goja.Value {
 		msg := vmArgStr(call.Argument(0))
 		if len(call.Arguments) > 1 && !goja.IsUndefined(call.Argument(1)) && !goja.IsNull(call.Argument(1)) {
-			emitter.log(msg, call.Argument(1).Export())
+			emitter.scriptLog(msg, call.Argument(1).Export())
 		} else {
-			emitter.log(msg)
+			emitter.scriptLog(msg)
 		}
 		return goja.Undefined()
 	})