It's been over a month since the last Windows 10 Mobile Insider Preview, build 10512, rolled out - and the very newest release, build 10536, was actually supposed to arrive last week, but was delayed due to the last-minute discovery of a serious bug. Earlier today, Microsoft said that a new revision of 10536 was looking like a good candidate for release tomorrow - but in fact, it's available right now.
If your device is currently on build 10512, Microsoft says that you'll have to perform two rounds of updates to complete the full process - first the jump to build 10536.1000; then a second update bumping this up to 10536.1004. Microsoft says that "this process will take a bit more time than usual but this has all the important fixes for build 10536 so you will want to make sure you take BOTH updates."
If you're currently on Windows Phone 8.1, you can upgrade directly to the newest Windows 10 Mobile build - but whatever your starting point, you can only grab this newest build as long as you're signed up to the Windows Insider Fast ring. Those on the Slow ring will have to wait until the build has been tested more thoroughly before Microsoft considers it for further deployment.
If you're on the Fast ring, the update is rolling out now - let us know how you get on.