TL is lining you up for PIP/termination. The other guy on the team is likely his buddy. Come review time, you will be shown as an IC that struggles to deliver, and the other guy will get all the credit.
Been there, seen that. Start looking for other teams internally ASAP.
I've been the other guy in this scenario before.. because it's a deprecated tool, this is a low risk way to demonstrate some reliability improvements, and a way for the TL to 'scratch the itch' of reducing risk. The other guy's improvements will be built into the new tool.
Been there, seen that. Start looking for other teams internally ASAP.