Desktop app: Message thread duplicates in scroll view, creates phantom scroll height

Environment:

• Claude Code Desktop (Mac)
• Version: Latest

Symptom:
Thread renders duplicate messages in the scrollable area, creating excessive scrollbar height relative to actual content.

Reproducibility:

• Frequent (happens most threads at certain length)
• Scrollbar height appears 3-4x larger than actual message content
• Excessive scrolling required to navigate thread

Impact:

• Navigation becomes tedious, but context window unaffected
• Appears to be rendering/virtualization issue only

Evidence:

• Screenshot attached: scrollbar height indicates phantom duplicate DOM elements
• Clear pattern: scrollable area much larger than visible content

Root Cause Hypothesis:
Message list virtualization component isn't cleaning up old rendered items as new messages arrive. Virtual list accumulates duplicate DOM nodes.

Workaround:
None identified yet.

Note:
User reports correlation with enabling/disabling unidentified plugin, suggesting DOM manipulation is involved.