> But I think there is tension between the Unix mechanisms and interactive applications that's not easy to resolve.

I would say that the platonic ideal of the pipe Unix mechanism has no buffering, and the buffer is only there as a performance optimization.

> What's `less | grep` or `vim | grep`... do we need to send input back through the pipe now?

Well, this is "interactive" in the timing sense. It still has one-way data flow. That's how I interpreted you and how I used the word.

If you meant truly interactive, then I think you're talking about something unrelated to the post.

You're right that it does not take input from the user. But I think you're in agreement with me that not everything is pipe-able.

The buffer in Unix (or rather C?) file output goes back to the beginning of time. It's not the pipe that's buffering.

Anyways, as soon as your mental model of these command line utilities includes the buffering then the behavior makes sense. How friendly it is can be debated. Trying to make it work with timers feels wrong and would introduce more complexity and deviate from some people's mental model.