markst3v3ns@ -- Thanks for reporting this issue. Could you please share the sample .APK file to reproduce the issue along with the screen cast for the better understanding of the issue.

Also, please share the device details where the issue is reproduced.

Thanks!

Right, what you describe is the behavior if verification fails, which is roughly speaking falling back to showing the web content in a Chrome Custom Tab.https://developers.google.com/web/updates/2017/10/using-twa#deploy_your_assetlinksjson_to_prove_ownership_of_the_domain describes how to troubleshoot Digital Asset Links.

Apk and screenshot attached. The hash in the asset links file: https://my.agcore.co.uk/.well-known/assetlinks.json is from the key used to sign the apk. The app was created with classes from the custom-tabs-client github example slightly modified to only use Chrome Canary. Screenshot taken on Pixel 2 with Android 8.1 and Chrome Canary 67.0.3389.0.

Deleted: device-2018-04-06-103010.png 65.8 KB

	device-2018-04-06-103010.png 65.8 KB View Download

Deleted: twa-test.apk 1.3 MB

twa-test.apk 1.3 MB Download

Thank you for providing more feedback. Adding the requester to the cc list.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Thanks!

It appears that Chrome fetches this URL to verify: https://digitalassetlinks.googleapis.com/v1/assetlinks:check?source.web.site=https%3A%2F%2Fmy.agcore.co.uk%2F&target.androidApp.packageName=com.example.twa&target.androidApp.certificate.sha256Fingerprint=AD%3A8F%3AB5%3A55%3AF2%3A6F%3AB2%3AB7%3AAA%3AF2%3A8F%3A46%3A23%3A3C%3A67%3AFC%3A9A%3ABC%3A7C%3A15%3A22%3AB1%3ABF%3AEB%3A31%3A7F%3A3F%3A12%3ACF%3A8A%3AF7%3A8F&relation=delegate_permission%2Fcommon.handle_all_urls

which returns a 400 error. The correct URL doesn't have a slash at the end of the web site to verify (just https://my.agcore.co.uk).

+Peter who worked on issue 800422.

Good to know what the problem was! So will this be fixed server side at digitalassetlinks.googleapis.com or client side?

Client-side in Chrome.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/08bb73244fe60b9f6f1e1e4c636a88931730f918

commit 08bb73244fe60b9f6f1e1e4c636a88931730f918
Author: Peter E Conn <peconn@chromium.org>
Date: Tue Apr 17 16:06:28 2018

🤝 Remove trailing slash from Origin.

GURLUtils.getOrigin returns an origin formatted with a trailing slash
because it calls GURL::GetOrigin which returns a GURL, then serializes
this URL. This seems to be incorrect behaviour as more generally an
origin is serialized without a trailing slash.

GURLUtils.getOrigin is used by AwGeolocationPermissions.java where the
returned value is saved to the user's Android Preferences. This means
that changing its behaviour would be tricky.

For now, I'm updating Origin.java to serialize without a trailing
slash and documenting the deviance in behaviour between the two.

Bug:  827161 
Change-Id: Ia70f8a60263742b28477f969cc075dcb97062f48
Reviewed-on: https://chromium-review.googlesource.com/1013483
Reviewed-by: Matt Menke <mmenke@chromium.org>
Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Commit-Queue: Peter Conn <peconn@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551351}
[modify] https://crrev.com/08bb73244fe60b9f6f1e1e4c636a88931730f918/chrome/android/java/src/org/chromium/chrome/browser/browserservices/Origin.java
[modify] https://crrev.com/08bb73244fe60b9f6f1e1e4c636a88931730f918/chrome/android/javatests/src/org/chromium/chrome/browser/browserservices/OriginTest.java
[modify] https://crrev.com/08bb73244fe60b9f6f1e1e4c636a88931730f918/net/android/java/src/org/chromium/net/GURLUtils.java

markst3v3ns, provided this change doesn't break something and get reverted, this should be available for you to try in Chrome Dev in a few days.

Thanks!

I can confirm its fixed in Chrome Canary 68.0.3434.0

Cool, thanks for verifying!