An assertion that has returned is no longer watching

await stream.Should().Within(...).Emit() reads as one thing: wait for this, then carry on. The "carry on" half quietly meant something weaker. The wait handed control back to the test and released its subscription a moment later, on another thread.

Almost always that gap is invisible. It is not invisible to a test whose next question is "is anything still subscribed to this?" — and that question is common, because it is how you check that a cache entry can be reclaimed, that a claim was released, or that an idle sweep is allowed to run. Such a test would ask, get the answer "yes, something is", and fail; and because the gap is a handful of instructions wide, it would only do so on a loaded machine, a few runs in a hundred. One landed in this repository's own suite: a cached stream entry refused to be released because the only thing still holding it was the assertion that had just returned.

What changes

The wait now releases its subscription before it settles, so "the assertion returned" means "the assertion is no longer watching". A test may rely on that with no grace period, no polling, and no retry.

Nothing else about the assertions changes: they still never resume your test on the thread that signalled, and a fault arriving after a wait has already settled is still reported rather than dropped.