@Jonathan and Nibaldo: You may be interested in also looking into this issue, since you have a good understanding of how the syntax highlighting engine works.

I tried to make an example to reproduce the problem, but without success.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE language SYSTEM "language.dtd">
<language name="Test" kateversion="5.0" version="1" section="Scripts" extensions="*.test" license="MIT">
  <highlighting>
    <contexts>
      <context name="base" attribute="Normal" lineEndContext="#stay">
        <RegExpr String="(.)" context="a" attribute="Normal" lookAhead="1"/> <!-- a -->
      </context>
      <context name="a" attribute="Normal" lineEndContext="#stay">
        <RegExpr String="(%1b)" context="b" attribute="Normal" dynamic="1" lookAhead="1"/> <!-- ab -->
      </context>
      <context name="b" attribute="Label" lineEndContext="#stay" dynamic="true">
        <StringDetect String="%1" context="#stay" attribute="Keyword" dynamic="true"/>  <!-- ab -->
      </context>
    </contexts>
    <itemDatas>
      <itemData name="Normal"	defStyleNum="dsNormal"/>
      <itemData name="Keyword"	  defStyleNum="dsKeyword"/>
      <itemData name="Label"	  defStyleNum="dsString"/>
    </itemDatas>
  </highlighting>
</language>

With

ab
ca
ab

All `ab` are Keyword

@Ivsn: if you read this, could you please comment and try again?

I submitted this bug because of the problem I had when I was adding syntax highlighting from my own markup language. It was several years ago and I don't remember now details of the problem. The syntax highlight file is here:

https://github.com/igagis/stob/blob/master/syntaxHighlight/katepart/stob.xml

and there is a TODO: comment there for that problem.

I will have a look when I have time and try to recall what I was trying to achieve there.

Just for info, there is a small spec of how syntax highlighting of my markup language is supposed to work:
https://github.com/igagis/stob/blob/master/syntaxHighlight/katepart/stob.xml

And the markup file I was using to test syntax highlighting was this one:
https://github.com/igagis/stob/blob/master/syntaxHighlight/test.stob

I don't know when I'll have time to refresh my memory about all this, I'll try to do it during next week and let you know.

I could not figure out what was wrong. The bug is very old, from 2016, so, perhaps it was already fixed since then.
Please close the bug.

Ok thanks for getting back. In that case we currently have no real issue and we close it. If this issue appears again, let's reopen.