The first 10% of a software project usually determines whether the other 90%
The first 10% of a software project usually determines whether the other 90% is wasted. Owners spend that 10% waiting for the kickoff.
It is where the decisions that cannot be undone get made, mostly by default.
Requirements. What the system has to do, written by the people who will use it, not the people who asked for it.
Assumptions. Every "we'll assume the data is clean" and "we'll assume the vendor API does that" that nobody wrote down. Each one is a change order with a date attached.
Architecture. Whether it is built to be replaced in pieces or to be replaced all at once, which decides the cost of every future decision.
Ownership. Who inside your company says yes and no once the vendor is gone. If the answer is a committee, the answer is nobody.
Integration. Which systems it has to talk to and whether anyone has confirmed those systems can talk back.
Success criteria. The number that moves, written down before the first invoice.
None of this is technical. All of it is boring, and it is the part where an owner's attention is worth the most and is usually spent least.
By the time the demo arrives, the money is committed and the questions have become complaints. Ask them in the first 10%, when they are still questions.