Pages 361-362 – Rare Rules, Always Fight First/Last
Add the following paragraphs to the end of this Rare Rules entry:

‘Note that it doesn’t matter how many rules are affecting a unit
that enable it to fight first, or how many rules are affecting it that
say it cannot be selected to fight until after all other units have
done so – if a unit is under the effects of one or more of both
kinds of ability simultaneously, that unit instead fights as if none
of those rules are affecting it.

Note that the Counter-offensive Stratagem requires you to select
a unit that is eligible to fight. This means that if a unit is under
the effects of a rule that says that it is not eligible to fight until
after all other eligible units have done so, then unless that unit is
also under the effects of a rule that lets it fight first, you will not
be able to select that unit to use the Counter-offensive Stratagem.

Some examples of rules that always allow a unit to strike first
include Martial Superiority and Veil of Time (see Codex: Space
Marines), Precognitive Strike (see Codex: Necrons), etc. Also
note, as per the core rules, that units that have charged fight first
in the Fight phase, and for the purposes of this Rare Rule this is
considered to be a rule that lets a unit always strike first.

Some examples of rules that always make a unit strike last (or say
a unit cannot be selected to fight until after all other eligible units
have done so) include Tempormortis (see Codex: Space Marines),
The Armour of Russ (see Codex Supplement: Space Wolves),
Obeisance Generators (see Codex: Necrons), etc.’