You ask a good question which can have several correct answers. However, the way I practice real estate, and teach our agents is very simple: If there is a question of what we call in the industry and legally Procuring Cause, the bottom line is who is the buyer/client wanting to represent them.
Unless you have an exclusive buyer/agent agreement with the previous agent, it would be difficult for that agent to claim compensation. You should also consider how much work the previous agent did for you, and why you chose to make a change. If you end up writing an offer on a property the previous agent showed you and you buy it, one solution is to give them a referral fee.
Your experience of buying a home should be a joyous and fun time. So iron out possible kinks in advance and you should be good to go. Good luck to you!
Procuring Cause is most accurately defined as : An order or series of events that without break in continuity lead to a sale.
In your case the "break" could be considered your switching agents.
If I were in the shoes of your current agent, I'd be consulting with my broker or a real estate attorney right now to see if I would win a case against me based on procuring cause, if it doesn't look good for me, I would probably offer to your prior agent a referral commission.
I don't look back on this same Trulia thread for answers posted after mine.
Realtor Since 1996
Main Street Realtor
If you did sign an exclusive buyer/broker agreement with the original agent that would also be taken into consideration. There are professional standards and a code of ethics that have to be followed in this scenario by all parties.
It should have been; you should have thought about it before now; but now, it is between them.
The Listing Agent and your Agent should be working hard to close your deal and they should not be involving you in the commission problem.