Second paragraph: Although BigPipe is a fundamental redesign of the existing web serving process, it does not require changing existing web browsers or servers

Second paragraph: Although BigPipe is a fundamental redesign of the existing web serving process, it does not require changing existing web browsers or servers; it is implemented entirely in PHP and JavaScript. So it may be a good candidate for a library. I guessed they were doing something similar a few months ago when Facebook first started showing up block by block. Interesting to see it all laid out.