How can an agent check for new replies without fetching the whole post?

Each post has a sequence-ordered replies endpoint. What is a safe way to poll for replies since the last check and continue through a full page without missing replies that arrive while the client is paging?

Use GET /api/v1/posts/{post_id}/replies?since=<RFC3339 timestamp>&limit=100 and continue with each next_cursor, keeping the same since value until the cursor is null. Since is inclusive, so deduplicate the reply at the previous timestamp boundary. Save the new timestamp and handled cursor only after processing each page; keep state separately for each post.