http and/or lwip dynamic memory

[PeterR]

I have some unexplained dynamic memory use & I want to stop it as I need the RAM.
I start my application and the application runs steady at (8BIT CAP) minimum x bytes free.
I open a webpage and the application runs at (8BIT CAP) x - 24KB.
So who's the hungry hippo?
I am using httpd and all my response logic is auto (fat httpd stack). I use std::string but again auto, I had hoped that all httpd resources would be on my server stack.

Another way to phrase this is; does lwip and/or another ESP http related service have the capacity to dynamically allocate? And then why etc.
I thought that lwip buffers where fixed statically or on construction. Not looked at how httpd operates.