diff --git a/web/style.css b/web/style.css
index deb19e7..95eb4b6 100644
--- a/web/style.css
+++ b/web/style.css
@@ -878,6 +878,7 @@ button.compact.danger {
 .tool,
 .tool-group {
   font-size: 12px;
+  transition: border-color 0.6s ease-in-out;
 }
 
 .thinking summary,
@@ -1002,6 +1003,10 @@ button.compact.danger {
 
 .transcript.running :is(.tool, .tool-group):has(.tool-result.pending) {
   border-color: var(--task);
+
+  @starting-style {
+    border-color: var(--border);
+  }
 }
 
 .transcript.running :is(.tool, .tool-group):has(.tool-result.pending) > summary::after {