WITH ev AS (
  SELECT person_id, timestamp, event FROM events
  WHERE timestamp > now() - INTERVAL 14 DAY
    AND properties.$pathname LIKE '/chat%'
    AND event IN ('chat_session_selected', 'composer_draft_started',
      'chat_message_sent', 'composer_send_blocked', 'chat_history_panel_toggled',
      'sidebar_nav_clicked', 'scroll_to_bottom_clicked', 'chat_file_upload_started',
      'voice_input_started', 'composer_add_menu_opened', 'chat_question_queued',
      'artifact_downloaded', 'generative_ui_interacted')
), seq AS (
  SELECT person_id, timestamp, event,
    leadInFrame(event) OVER w AS next_event,
    leadInFrame(timestamp) OVER w AS next_ts
  FROM ev
  WINDOW w AS (PARTITION BY person_id ORDER BY timestamp
    ROWS BETWEEN CURRENT ROW AND 1 FOLLOWING)
)
SELECT next_event, count() AS n,
  round(quantile(0.5)(dateDiff('millisecond', timestamp, next_ts)) / 1000, 1) AS p50_s,
  round(quantile(0.25)(dateDiff('millisecond', timestamp, next_ts)) / 1000, 1) AS p25_s,
  countIf(dateDiff('millisecond', timestamp, next_ts) < 3000) AS within_3s
FROM seq
WHERE event = 'chat_session_selected'
  AND next_ts > timestamp AND dateDiff('minute', timestamp, next_ts) < 10
GROUP BY next_event ORDER BY n DESC LIMIT 15

SELECT properties.reason AS reason, count() AS n
FROM events
WHERE event = 'composer_send_blocked' AND timestamp > now() - INTERVAL 7 DAY
GROUP BY reason ORDER BY n DESC