If there is any foreseeable need that the format will benefit from being executable, I would make the magic bytes looks like this: #!/usr/bin/whatever^@^@^@^

If there is any foreseeable need that the format will benefit from being executable, I would make the magic bytes looks like this: #!/usr/bin/whatever^@^@^@^@^@[HDR] A hash bang path terminated by a null, followed by some (aligned) binary material with version information and whatnot, all fitting into around 32 bytes. The header format could allow for variability in the path; the #! and [HDR] part could be enough to give it identify it.