Back when I had time to think about extensible programming, I predicted that the most likely route to its realization was some vendor creating a new version of a wholly-owned toolchain. After all, if Microsoft had decided that VB.NET source code would be stored as XML, in a format that allowed for arbitrary extension points, everyone else would be saying, "Gosh, that's cool," and racing to catch up. But tools like Jester (a mutation tester for Java) are forcing me to re-think: while a uniform representation of source code would make what they do easier, it's clearly not essential. Now, would someone please create an extensible debugger for me? Please?