XML syntax for Sublime Text 4 with python syntax highlighting in <exec>...</exec> tags.

XML (Python).sublime-syntax

%YAML 1.2
---
name: XML (Python)
scope: text.xml.python
version: 2

extends: Packages/XML/XML.sublime-syntax

# file_extensions:
#   - xml

contexts:

###[ XML TAGS ]###############################################################

  tag:
    - meta_prepend: true
    - include: python-tags

###[ PYTHON XML TAGS ]########################################################

  python-tags:
    - match: (<)(exec|virtual|condition|validate)(?=[/<>\s])
      captures:
        1: punctuation.definition.tag.begin.xml
        2: entity.name.tag.localname.xml
      push: python-tag-content

  python-tag-content:
    - meta_scope: meta.tag.xml
    - match: '>'
      pop: 1
      scope: meta.tag.xml punctuation.definition.tag.end.xml
      embed_scope: meta.embedded.python.xml source.python.embedded.xml
      embed: Packages/Python/Python.sublime-syntax
      escape: (?=(</)(exec|virtual|condition|validate)[/<>\s])
    - match: />
      scope: punctuation.definition.tag.end.xml
      pop: 1
    - match: \?>
      scope: invalid.illegal.bad-tag-end.xml
      pop: 1
    - include: tag-end-missing-pop
    - include: tag-attribute