askvortsov replacing the hasher completely would break previously stored password hashes
Actually no. Since Argon2 is another hash supported by PHP. The hash value itself contains an identifier for the hash method used, and PHP will use that when calling password_verify. When using the base Laravel/PHP hasher, the selected algorithm merely applies to new hashes.
Same applies for the number of hashing rounds. If you change it, it applies to new hashes, but old hashes will still work and will not be updated automatically.
