I was not able to produce some minimal reproduction of this bug, but I'll try to explain my findings.

URL rendering in an GHCS application went wrong. Instead of

https://some-host.io/api/v1/local

I got:

htocalhttps://some-host.io/api/v1

when building with ghcjs and -dedupe.

The url gets build here.

I was able to fix that behaviour, by either removing -dedupe or by doing the mappending with Strings:

eskimor/servant@2410eb3

I should note that the project is an Obelisk project and uses this version of the reflex-platform.

I was not able to reproduce this with a toy application that just does some string concatenation, also obviously there are lots of Text values mappended in the application without any issues.