OS (usually security-based) patches and hotfixes that Microsoft releases to the community normally consist of, in my understanding, a series of updated DLLs or other binaries.
How does Microsoft, and other companies like it, ensure that that hotfixes don't clash with each other? Do they always go for a cumulative patch approach, where a single hotfix will includes all of the fixes in previous hotfixes? This doesn't seem to be the case, because many hotfixes seem to be focused on fixing specific problems. If they are focused hotfixes, how do they prevent one hotfix from trashing another one (e.g. incompatible DLLs being installed with each other).
I have always admired Microsoft's ability to manage this process. The company I work for is much smaller, and when I worked on the patch process a few years ago, we always went for the cumulative approach, where a single patch immediately superseded all previous patches based on that release. This meant that the patches got progressively larger in size, until the next "official" release came out.
What are some good practices for managing patch dependencies?