Slim Twig Flush

1

I need to send some flush while the page is being processed using slim with twig.

I need to render a page and still flush it

2

You could try the flush tag to tell Twig to flush the output buffer:

https://twig.symfony.com/doc/3.x/tags/flush.html

A custom middleware could convert the flushed output buffer to a PSR-7 stream.