> why, what do you want to achieve; there are already such hooks
The original request was
sorry for the noise :
is there in mkiv a very last macro ?
I mean something like
\IamCallAtTheReallyEnd{..}
which does absolutly nothing to the pdf , and  after  which mkiv ends
without calls any other macro

Peter suggest to use \everylastshipout;
but this

\def\LuigisWhateverShouldHappen{\immediate\write16{BOOOM!}Something
Luigi want to do for some unknown reason.\immediate\write16{BOOOM!}}

\appendtoks\LuigisWhateverShouldHappen \to \everylastshipout
\starttext
hello
\stoptext

write
Something Luigi want to do for some unknown reason.

near the bottom of pdf (and I don't want it)
and BOOM! on log (which is a way to say that this macro was called)


Aditya suggests to put nothing to print in
\LuigisWhateverShouldHappen
and I said that it's no a robust solution .


BTW, for a specific document, this is actually a solution -- just need a bit
of test --

I'm almost sure that there is no solutions much differents from this one.
>From luatex.web , around line 22423 :

@ We don't want to leave |main_control| immediately when a |stop| command
is sensed, because it may be necessary to invoke an \.{\\output} routine
several times before things really grind to a halt. (The output routine
might even say `\.{\\gdef\\end\{...\}}', to prolong the life of the job.)
Therefore |its_all_over| is |true| only when the current page
and contribution list are empty, and when the last output was not a
``dead cycle.''


-- 
luigi