Is there any reason not to salt and hash before using bcrypt

Question

I’ve seen some recommendations suggesting that you shouldn’t manually salt and hash a password before passing it into bcrypt, but I’m not sure why.

• Would manually salting interfere with bcrypt’s built-in salting mechanism?
• Could double hashing weaken security instead of strengthening it?
• Is there any scenario where adding an extra layer of hashing before bcrypt is beneficial?

I want to ensure I’m implementing bcrypt correctly without introducing unnecessary complexity or vulnerabilities.