This file name is layout.pug(parent):
doctype html
html
head
title knowledgebase
body
block content
br
hr
footer
p Copyright © 2018
And this file name is index.pug(child):
extends layout
block content
h1 articles
h1 #{title}
At first I thought everything was good with your code, then I looked closely at what was pasted here.
If inspect the code in layout.pug you'll see that there's a leading space on every line. Make sure that
doctype htmlandhtml(which are your root elements in the parent template) have ZERO spaces at the start of the line.Otherwise your code looks good and should work as expected.