Does Zen have a concept similar to stream entry? Stream entry feels like a milestone where some very significant things happen and the practitioner cannot slide backwards from it. Do Zen sutras describe the concept of stream entry by that or any other name?
I'm not sure if it corresponds in every respect with stream entry but in Japanese Zen they generally distinguish Kenshō, the initial seeing of one's nature, from full Buddhahood so I think it is at least analogous to stream entry.

I'm not sure how this is talked about in forms of Zen outside of Japan (such as Chinese Chan, Vietnamese Zen, and Korean Seon) however, as I think the explicit distinction between Kenshō and Satori is a distinctively Japanese idea.