seeded (instead of random) ed25519 private key generation?

[getify]

I'm looking to generate/compute an ed25519 private key from a known seed/iv. I don't see a method for that on the ed25519 API. Is there a way to do this, perhaps with the abstract API or the utils? I don't fully understand the underlying math involved, so without a dedicated API method for this I couldn't work out how to do it. Thank you.

[paulmillr]

If the seed is not reused for other applications, you can use it directly, as private key. It needs to be 32 bytes, that's mostly it.

Otherwise, a suggested method to convert seed to a private key could look like this:

import { hkdf } from '@noble/hashes/hkdf';
import { sha256 } from '@noble/hashes/sha256';
let seed = ...; // uint8array
const edKey = hkdf(sha256, seed, undefined, 'my-app-name', 32);

ed25519-keygen package also provides bip32 hierarchical wallets built on top of seed: https://github.com/paulmillr/ed25519-keygen?tab=readme-ov-file#hdkey