It depends on the wording of your buyer-broker agreement, and this is one where you want the actual document read by an attorney in your state rather than a general answer, because commission claims and assignment rights are governed by state contract law and state real estate licensing rules.
The mechanism, though: most buyer-broker agreements define the triggering event as the buyer acquiring an interest in property, and many extend that to acquisition by an entity the buyer controls or an assignee. That language exists specifically because buyers assign into LLCs all the time. If your agreement has it, assigning to your partner entity almost certainly triggers the fee. If it doesn't, you have an argument, and the agent has a different argument based on procuring cause, which is a doctrine about who brought the deal about. Neither of those gets resolved cleanly in a forum post.
On the second question, the assignment itself sits outside the buyer representation in most cases. Your agent represented you in acquiring the contract. Once you assign, the assignee has no agreement with your agent unless they sign one. Some agents will ask you to disclose an intended assignment up front and will want it addressed in the agreement, partly because assigning contracts can touch licensing rules depending on how it's marketed and how often you do it, and those rules differ by state.
The thing that bites people in this structure is the seller side. Many purchase contracts restrict assignment or require seller consent, and a seller who finds out mid-escrow that the buyer changed can slow or kill the closing. Check the assignment clause in the purchase contract before you worry about the commission clause.
