> This is why contract law exists, doesn't it?

When I worked with non-trivial (>$1m) contracts, I learned that the sooner you start pointing to contract language, the sooner the relationship breaks down. “Working with” partners through shortfalls and giving second chances resulted in much more long term success than sticking to the letter of the contract.

Part of the reason, I think, is simple human relationship-building. And a big part of that is trust. Trust and credit also play into it directly - the vendor knows we didn’t penalize them when they delivered a feature a month late, so they’re willing to surge when we have a requirement pop up that needs fixing quicker than we agreed to.