Русско-англо-русский юридический словарь

on the anvil. In a formative but immature or unready state; being prepared, discussed, planned, etc., but not yet ready. The details of the proposed merger are still on the anvil, but we should see something ready before the end of the summer. I've had a couple of projects on the anvil recently, but nothing has taken any definite shape yet. (Farlex Dictionary of Idioms)

in the works – (informal) in preparation, e.g. Various amendments to the Act are in the works. (Common Mistakes in Business English, Harward Communications)