The Constitution doesn't require Congress to negotiate the agreements. That is up to the Executive Branch. Fast Track doesn't give the Executive Branch the authority to enter into those agreements. They must still be approved by Congress. It only is an agreement by Congress that it will consider the trade agreement without introducing amendments.
Even that limitation doesn't prevent Congress from saying that it won't approve a trade agreement unless the Executive Branch makes changes to what has been negotiated.
The courts have upheld Fast Track. It is constitutional.
I tend to agree, and you said it better than I could. This fastidious rectal examination of Fast Track appears mentally unbalanced.
"Fast Track" {Trade Promotion Authority} turns the separate Constitutional authority granted to Congress and the President upside down and backwards. The idea of administration "Fast Track" authority on foreign trade epitomizes the government envisioned by Orwell in his "1984" prediction{?}. Being a well educated lawyer, you MUST know that. What's the deal?? Peace and love, George.
Good reading. This statement has been entered into the Congressional Record.