I am working on a plan for a timber frame house sitting on a concrete slab on grade. The homeowner wants the slab to be used as the finished floor (with radiant heat). I was wondering what options I have to tie the interior posts to the concrete with the tie being at least somewhat concealed (the more concealed the better). I was planning on raising the frame in bents. Any help would be greatly appreciated!

Jamie,

Do you need a hold down (for wind, seismic, lateral loads) - or just a locator?

If just a locator, you might be able to use a piece of rebar or pipe that is epoxied into the floor and then into the post.

If you need a hold down, you'll need to design the connection for the uplift or lateral loads that you are working with - and that could be a simple bolt / pin connection that would be easy to hide, or something more involved like a T or U plate that could be visible.

A method I have used for interior posts in that very scenario is to fabricate 8"x8" "frames" from 2"x2" steel tubing. This leaves a 4x4" opening that a 4x4" stub tenon on the bottom of your post will sit in to prevent lateral movement. The steel frames are secured to the concrete using one of several methods available. Baseboard trim hides the steel afterwards.
And, like Mike said, to hold the posts down, I weld steel strapping to the outside face of perimeter post bases and posts with at least one hidden face. Wall framing hides these straps.
(I have pictures but never caught on on on how to post)
Take care with the slab though. Point loads at post locations, especially the perimeter and corners, put your slab in danger of cracking. Are you in frost country?

Timberlinx have a wedge anchor connector with hidden fasteners and wood plugs. I've used them and you don't know they are there inside the bottom of the post...and no uplift!

Rooster

Well it will be built in the prairies where wind and seismic aren't an issue. Just snow! So in this situation hold down type fasteners might be unnecessary? For exterior posts is there a specific product that you would recommend? Thanks!

Thanks for all the info. I am definitely in frost country. I was planning on laying a 24" x 8" strip footing approx 4.5 feet below grade and then an ICF concrete wall on top up to grade. Would you think this would be sufficient to support at the point loads?

4.5' seems a little shallow to me for the prairies. Code where I am is 5' and I know it can get colder out there. The local building dept can help you with that.
Wind or no wind you still need to anchor the building down to it's foundation.
Timberlinx are a fine product and certainly would do the job. The thing is they use a beefy threaded 7/8" rod that you would need to either install when you pour the slab (which would be a stressful exercise given the accuracy required and the impending setting-up of the floor) or drilling for anchors afterward while not drilling into the heating tubes.
Also remember that the post bottoms should not rest directly on the concrete. The end grain will suck up moisture from the floor. A barrier of some kind needs to go between the two.

That sounds good. Thanks so much for all the helpful info!