passing attributes into bpatcher

This seems like something that should be easy but I can't figure out. I'm trying to pass an attribute to a patcher wrapped in a bpatcher.

The patch can be initialised like this [ my-patch @key value ], so I assumed that inside a bpatcher it would be [ bpatcher my-patch @args @key value ]. But the attributes don't appear in the patcherargs, either as arguments or attributes. They seem to just be ignored completely. Using quotes, ie [ bpatcher my-patch @args "@key value" ] doesn't make any difference.

Can I do this without manually adding them to the inspector window?