Chrome debugger doesn't step through code properly

[mercmobily]

I am studying lit-html. I read the code, read how it all works, and am trying to figure out what does what and where.
One of my best weapons normally is the Chrome debugger. I intended to create a template, render it, and understand exactly what happened by stepping through the code.
The problem is that Chrome (I am using 69) doesn't seem to allow me to do that. When I hover on variable names, the debugger seems to think that "fragment" is "ragment". Try and step into this code and see what I mean:

import { html, render } from 'lit-html'

var name = 'Tony'
var r = html`<h1 .value="${name}" href="${name}">Hello ${name} and again ${name}</h1>`
var r1 = render(r, document.body)
console.log(r, r1)

You basically.. .can't. Is there a trick, or anything, to make stepping through work?
I am also worried I won't be able to step through code to debug a real-life project..

[LarsDenBakker]

How are you serving the project to the browser? Are you running it all natively as a module, or through some build step?

[mercmobily]

Ah, it happens when I use Polymer Serve. If I use a straight web server with no building/manipulation what so ever) there is no weirdness!
Here is an example of what I am seeing with polymer serve:

[web-padawan]

Duplicate of Polymer/tools#389

[mercmobily]

Apologies.