Tristan has discovered stairs.
Jen and Tom told everyone that they understood the dangers of wishing Tristan would start to crawl. Besides, he’s been doing his rolling and commando “slither” for a long time. Perhaps he would just skip the crawling phase. Well, no such luck. While the rolling and slithering continues, he has added crawling and climbing to his repertoire. And, as pictured above, stairs do not seem to be an obstacle.