We might modify bank design to produce a prompt bank from a non-prompt bank by reserving space. Some call on a non-prompt bank could acquire and reserve some specified amount of space to be directly held by some new sort of bank which would allocate that space upon ordinary requests. This new bank is prompt although of a different internal behavior than the current prompt banks that conceptually ask for space from their superior banks instead of having it ready at hand. This idea is a bit like the faulty battery version of meters but the fault does not seem to apply here. The call to make the prompt bank would be non-prompt since it might require appeal to user agents. The factory would thus not be in a position to make this call, but the requestor to the factory would be.
It seems curious that the extra hair cannot be delegated to the factory, especially as it has to do with factory theory. This logical reason seems to be that in bottoming out the process of acquiring new space, it is impermissible to “borrow space” which is just what is required in conventional programming. The extra space to be borrowed here is the space to hold the activation record for that factory that awaits resolution of space among the user agents. Conventional programming would merely use a new stack frame, but we account even for that space.
Another place to look for ideas is the treatment of kept segments. Some segment keys are sensory and others are not. The primitive apparatus of sensory keys helps the factory ensure that components of a factory convey no unaudited outgoing channels. The key idea there may be: “The sensory version of a segment key is a segment key without authority to invoke a segment keeper.”.
Another new idea that should go in with this change is to eliminate the two kinds of banks and provide prompt and non-prompt orders to a single sort of bank. I think that this makes for less code, less documentation and certainly fewer slots to hold bank keys. Most bank call sites are already designed with some idea of whether the bank is prompt or not, and in this case the site can statically choose which sort of buy to order space with. This note is a preliminary design of such a plan.