Thanks for the detailed report and video. This is a confirmed issue - long agent sessions accumulate internal state that progressively slows down text rendering, which is exactly what your recording shows.
Workaround:
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Start fresh agent sessions periodically. Closing the current chat tab and starting a new one resets the renderer state that causes the slowdown. This is the most effective mitigation right now.
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Check your
state.vscdbfile size. Over time, this internal database can grow to several GB and compound the sluggishness. On Windows, check:%APPDATA%\Cursor\User\globalStorage\state.vscdb. Important: back up this file before deleting it — removing it will clear your chat history and workspace state, but it will restore normal performance if it has grown large.
A few other users have reported the same pattern:
Our team is actively working on retention limits and performance improvements for long sessions.