diff --git a/apps/web/src/components/chat/MessagesTimeline.tsx b/apps/web/src/components/chat/MessagesTimeline.tsx
index 64ca547ee1ae1baffca05c446677f193d4449cc5..26a2881322ba9f0d6230edf90725e6b419ba14f2 100644
--- a/apps/web/src/components/chat/MessagesTimeline.tsx
+++ b/apps/web/src/components/chat/MessagesTimeline.tsx
@@ -623,7 +623,11 @@ export const MessagesTimeline = memo(function MessagesTimeline({
       listRef,
       timestampFormat,
       routeThreadKey,
-      threadRef: parseScopedThreadKey(routeThreadKey),
+      // Must be referentially stable: ChatMarkdown keys its react-markdown
+      // component map on threadRef, and a fresh object here remounts every
+      // rendered markdown node whenever this memo recomputes (e.g. on each
+      // activity delta while the thread is working).
+      threadRef: citationThreadRef,
       markdownCwd,
       resolvedTheme,
       workspaceRoot,
@@ -648,6 +652,7 @@ export const MessagesTimeline = memo(function MessagesTimeline({
       listRef,
       timestampFormat,
       routeThreadKey,
+      citationThreadRef,
       markdownCwd,
       resolvedTheme,
       workspaceRoot,