Assistants are the easiest thing in software to demonstrate and the hardest to be responsible for. A demo answers a question. A product spends somebody's money, cancels somebody's access and sends an email with a company's name on it.

Ledger is an assistant inside a subscription billing platform, 

built to design that boundary rather than describe it. It is a Wizard of Oz 

prototype: no model, no retrieval, every response written by hand. 

The company and the data are invented. The rules are not.

Every rule in it exists because somebody, somewhere, is going to click confirm at half past four on a Friday and mean it.

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