Purchased a BA 11.3 pistol upper w/ 11.3 hanson barrel... adding a MI Combact 10.5 rail this week. and SBA3 brace.

My question comes to measuring the pistol so as to not register as SBR..

My understanding is it has to be 26" or longer to not be SBR? And that is from end of buffer tube (w/o brace on ) to end of muzzle or muzzle device..
I have a a2 standard birdcage going on it. and will measure 26.5 from end of tube to end of muzzle device.

Is this legal for pistol? I know the AFT ... OR um.. ATF keeps looking at changing the rules.

Barrel less than 16", with a brace instead of stock is a pistol (as far as I understand it).  Are you wanting to put a vertical grip on it?  I think that's when the 26" overall length comes into play.  I also believe the measurment is from muzzle crown (or end of muzzle device if pinned) to end of bare receiver extension.

Methinks you are confusing SBR with the act of adding a vertical grip to a "pistol" with an OAL exceeding 26" which works around it being considered an AOW.

An AR pistol can have any length barrel, unless your state has a restriction on barrel length, but shorter barrels are popular for ease of handling and compactness, etc.

An SBR is a firearm with a barrel shorter than 16" that also has a buttstock.

A muzzle device can only be factored in the length of a barrel if it is permanently attached to the barrel.

Your "pistol" is fine, for now.  Who knows what kind of shenanegans the AFT/ATF, POS's, SFB's, etc, etc, etc will try in the future.