diff --git a/backend/ai-core/internal/orchestrator/synthesizer.go b/backend/ai-core/internal/orchestrator/synthesizer.go
index ef88759..986c070 100644
--- a/backend/ai-core/internal/orchestrator/synthesizer.go
+++ b/backend/ai-core/internal/orchestrator/synthesizer.go
@@ -171,6 +171,7 @@ func (s *Synthesizer) emitToolProgress(eventCh chan<- model.StreamEvent, name, s
 	if eventCh == nil {
 		return
 	}
+	defer func() { recover() }() // channel may be closed by caller
 	select {
 	case eventCh <- model.StreamEvent{
 		Type: model.StreamToolProgress,