diff --git a/components/ideas/idea-timeline.tsx b/components/ideas/idea-timeline.tsx
index b81eb42..5e17b94 100644
--- a/components/ideas/idea-timeline.tsx
+++ b/components/ideas/idea-timeline.tsx
@@ -128,7 +128,13 @@ export function IdeaTimeline({
   const showChatInput = planMd !== null
 
   return (
-    <div className="space-y-4" {...debugProps('idea-timeline', 'IdeaTimeline', 'components/ideas/idea-timeline.tsx')}>
+    <div {...debugProps('idea-timeline', 'IdeaTimeline', 'components/ideas/idea-timeline.tsx')}>
+      {showChatInput && (
+        <div className="sticky top-0 z-10 bg-background border-b border-border pb-3 mb-4" data-debug-id="idea-timeline__chat-input">
+          <UserChatInput ideaId={ideaId} isDemo={isDemo} />
+        </div>
+      )}
+      <div className="space-y-4">
       {merged.length === 0 ? (
         <p className="text-sm text-muted-foreground py-8 text-center italic">
           Nog geen activiteit op dit idee.
@@ -252,8 +258,7 @@ export function IdeaTimeline({
           })}
         </ol>
       )}
-
-      {showChatInput && <UserChatInput ideaId={ideaId} isDemo={isDemo} />}
+      </div>
     </div>
   )
 }