If I am understanding the problem correctly (and I’m honestly not at 100% there) I don’t think Multi is at fault here. Repo.transact (and Repo.transaction) would have the same problem since they all share the same SQL transaction handling. It appears to mark the connection as failed and that is what triggers the rollback on next (or possibly final?) retry: db_connection/lib/db_connection.ex at 165ce62b9636ae56d4a0f0810c2aa3803b3cff1e · elixir-ecto/db_connection · GitHub

run/3 and transaction/3 can be nested multiple times. If a transaction is
rolled back or a nested transaction fun raises the transaction is marked as
failed. All calls except run/3, transaction/3, rollback/2, close/3 and
close!/3 will raise an exception inside a failed transaction until the outer
transaction call returns. All transaction/3 calls will return
{:error, :rollback} if the transaction failed or connection closed and
rollback/2 is not called for that transaction/3.

And some logs visualizing the transformation of the error. Looks like it does pass through until the final retry (also a short circuit probably would be preferable for this case, not sure if that’s practical though)

[Oban.Repo.transaction] attempt=1
[Oban.Repo.transaction] rescued error=Postgrex.Error message=ERROR 22P02 (invalid_text_representation) invalid input value for enum oban_job_state: “bogus”
*[Oban.Repo.transaction] attempt=2
[Oban.Repo.transaction] rescued error=DBConnection.ConnectionError message=transaction rolling back
[Oban.Repo.transaction] attempt=3
[Oban.Repo.transaction] rescued error=DBConnection.ConnectionError message=connection is closed because of an error, disconnect or timeout
[Oban.Repo.transaction] attempt=4
[Oban.Repo.transaction] rescued error=DBConnection.ConnectionError message=connection is closed because of an error, disconnect or timeout
[Oban.Repo.transaction] attempt=5
[Oban.Repo.transaction] rescued error=DBConnection.ConnectionError message=connection is closed because of an error, disconnect or timeout
[Oban.Repo.transaction] max retries reached, reraising
Expected exception Postgrex.Error but got DBConnection.ConnectionError (connection is closed because of an error, disconnect or timeout)