Mutagen is a fast, continuous, multidirectional file synchronization tool. It can safely, scalably, and efficiently synchronize filesystem contents between arbitrary pairs of locations in near real-time. Support is currently implemented for locations on local filesystems, SSH-accessible filesystems, and Docker container filesystems. Mutagen is designed specifically to support remote development scenarios, with configurable behaviors specifically designed to help developers edit code locally while building, running, or packaging it in a remote environment.