Hundreds of developers around the Googleplex rejoice.

Isn’t Bazel based off another tool they use internally?

Yes. My guess is that over a long enough period of time, the internal build system will migrate to Bazel. But I don’t think it will happen soon. Large migrations are always a pain, but Bazel does make it easier (since you can isolate dependencies very well and migrate bottom-up).

I don’t work there, but I have talked to Googlers working on build systems.

Bazel is just the open source name of the internal Google build system, it is the same codebase.

From what I understand, the two tools have some very significant differences at this point. They may be the same codebase in a broad sense, and may share a lot of code, but I bet they are using something like Copybara to synchronize them.

https://github.com/google/copybara