The CMT was maintaining a standalone repository for one class, disjoint_sets, of which the only internal boost usage was in graph and graph_parallel (which depends on graph). disjoint_sets has been moved into boostorg/graph on develop. The superproject has a PR to remove it as a submodule, and the boostdep tools has a PR to remove it from an exclusion list. The path to the header has been preserved, so external usage will remain unaffected for those who download boost as a package, as disjoint_sets is header-only. If you experience any issues on develop relating to the header boost/pending/disjoint_sets.hpp, make sure you have the latest boostorg/graph, and you can manually remove libs/disjoint_sets from your sandbox, that should resolve it until the other PR in the superproject comes along. Even after that is merged, I'm not sure how the defunct disjoint_sets will be handled in sandboxes and may still need to be manually removed. There is no useful content in disjoint_sets at this point. I had experienced some complaints from b2 about being unable to link the header because it was coming from the old repository when I staged this change. Thanks, Jim