The Inquisitive Rogue's Insightful Fighting feature says:
At 3rd level, you gain the ability to decipher an opponent’s tactics and develop a counter to them. As a bonus action, you make a Wisdom (Insight) check against a creature you can see that isn’t incapacitated, contested by the target’s Charisma (Deception) check. If you succeed, you can use your Sneak Attack against that target even if you don't have advantage on the attack roll, but not if you have disadvantage on it.
This benefit lasts for 1 minute or until you successfully use this feature against a different target.
And the Tactical Assessment maneuver says:
When you make an Intelligence (Investigation), an Intelligence (History), or a Wisdom (Insight) check, you can expend one superiority die and add the superiority die to the ability check.
So I was wondering whether I could use the maneuver since Insightful Fighting makes a Wisdom (Insight) check.
Best Answer
Yes, Tactical Assessment can apply to any insight check.
As you've quoted, Insightful Fighting lets the character use a bonus action to attempt an Wisdom (Insight) ability check.
and the battle master's Tactical Assessment applies to those checks.
Using this battle master maneuver doesn't require any sort of action. There is no restriction that the maneuver must be used in battle, or that an insight check must be used in a non-combat roleplay encounter. The only general restriction on maneuvers is that multiple maneuvers can't apply to one attack.
However, an insight check isn't an attack, it's an ability check. So everything checks out.