I have a crack on my front derailleur braze on on my carbon bike.  The crack is narrow and is not all the way through the braze on tab - on inspection it does not appear to be deep.  Unlike most bikes, the braze on is actually moulded as part of the frame and not riveted or bolted on - so a replacement is not an easy option.

I was considering repair options, and wondered if using your Black Epoxy Repair filler would suffice or of there was a better recommendation?

The tab holds the front derailleur onto the bike - so the stress of the derailleur moving the chain between chain rings is all it has to deal with.  It is an electronic shifter, so there aren't any additional forces from a cable that a mechanical shifter would cause.

Thanks
Steve