Conflicting validity of a transaction among miners

Question

What happens to an unconfirmed Bitcoin transaction if miner A verifies it as valid and miner B claims it is an invalid transaction?

Answer 1

To be clear there are nodes (which validate) and miners, which compute the block hashes, let's assume you meant nodes.

What happens to an unconfirmed Bitcoin transaction if miner A verifies it as valid and miner B claims it is an invalid transaction?

If nodes disagree on the validity of a transaction, then they are not following the same consensus rules, and a hard fork occurs. That is, the chain of blocks diverges at that point because one node has a block that the other does not. Any subsequent blocks on each chain will have a different hash, and the chains will never be compatible. This is true for any group of nodes following a set of consensus rules.