The party evoker has a Shield Guardian.
In the last session he hit 14th level and obtained Overchannel.
It is clear to me that if he used Overchannel when casting a spell on the Guardian, to be stored in the Guardian, that this would count as one use of Overchannel for him for the day.
But it is not clear to me when the spell was re-cast by the Guardian whether it would obtain the maximum damage that the feature allows.
The guardian can store spells according to the following (emphasis mine):
Spell Storing. A spellcaster who wears the shield guardian's amulet can cause the guardian to store one spell of 4th level or lower. To do so, the wearer must cast the spell on the guardian. The spell has no effect but is stored within the guardian. When commanded to do so by the wearer or when a situation arises that was predefined by the spellcaster, the guardian casts the stored spell with any parameters set by the original caster, requiring no components.
On the one hand, Overchannel says "When you cast a wizard spell" and on the re-cast it is the Guardian casting the spell, not the Evoker, and the Guardian does not have the Overchannel feature.
On the other hand, the spell is stored "with any parameters set by the original caster", which some say "means any of the choices that would be made when the spell is cast", and this might include the choice to use Overchannel.
So would an Evoker's Guardian be able to store the spell specifically as Overchanneled for maximum damage, or would it emerge as a rolled-damage spell?