Is the html context available when using myst_substitutions?

[OriolAbril]

I would like to use myst_substitutions to include information from the post directive defined by ablog. I know how to access posts and metadata from the abog key in the html_context but I am not able to access this context when using myst_substitutions. I also have not been able to find this information maybe in a different part of env made available to myst_substitutions?