Problem/Motivation
By design the regions Page top and Page bottom are hidden from the Block UI (see https://www.drupal.org/project/drupal/issues/2639802) and other regions are also hidden by defaults on certain themes, (like First Sidebar on Claro and Seven). The problem is that they appear on the Context module's Blocks Reaction. Even if you add blocks to these regions, they do not appear, so it is not necessary to show them at all.
Steps to reproduce
Enable the Context module and create new context with a reaction "Blocks" - you will see Page top and Page bottom regions (Or First Sidebar, depending on your default theme). Try adding Powered by Drupal block in one of the regions, save and go to the page where the context should appear - the block will not be visible.
Proposed resolution
Unset these hidden blocks from the Blocks reaction.

| Comment | File | Size | Author |
|---|---|---|---|
| #2 | 3273252-2.patch | 635 bytes | hmendes |
Issue fork context-3273252
Show commands
Start within a Git clone of the project using the version control instructions.
Or, if you do not have SSH keys set up on git.drupalcode.org:
Comments
Comment #2
hmendes commentedSending a patch, please review.
Comment #3
andregp commented@hmendes, Thanks for the patch. It worked fine for Bartik but had side-effects on Claro and Seven, both of them lost the "First sidebar" region after the patch was applied.
Comment #4
hmendes commentedAndre, thank you for the review.
I was wondering, the regions that now appears in both Claro and Seven (Bartic also) are the same regions that appears when you go to the Block Layout page (/admin/structure/block) when you have the themes enabled, so I understand that now it is correctly showing only the regions that the theme has... isn't it?
Comment #5
andregp commented@hmendes, Oh, okay that makes sense. With further investigation I noticed that 'First Sidebar', or
sidebar_first, is listed as a hidden region on both Claro and Seven info.yml files so makes sense they shouldn't appear among the Context Reaction regions.I updated the IS accordingly and I'm moving this to RTBC.
Congrats :)
Comment #6
andregp commentedForgot to update issue tittle.
Comment #8
paulocsFixed! Thanks.