There are several issues which show this is is a 'tainted' situation.

The original "lack of cooperation" from Off-shore development and subsequent assumption of a potentially lucrative project/product by the OP is either laudable - or the first salvo in this escalating game of deceit.

Bringing the project back in house could be seen as "empire-building" from another perspective. From a managment point of view your squeeky wheel has cost them money they felt was not actually needed. Apparently, someone was, more or less happy with the production - even with the failures, uncooperative track record and the distress caused to the customer - managment was content, until the OP caught the attention of upper management.

The project is now being fast tracked but this time managment is being proactive. They appear to want to prevent another case of one person/one team ownership.

I would suggest, since you have done what you set out to do (fixed the bottle-neck and satisfied the original customer)... maybe its time to move on?

I agree - it may be time to have a one-on-one with the new manager. But instead of holding on to this "tainted" hot potatoe - it might be time to see if you can be reassigned to the next troubled project?

If the new manager is really cutting you out of the picture, taking credit for your sucesses - this gives him the chance to he needs. But it also gives you a chance to gracefully step away from situation which you currently find toxic or at least see which way the wind is blowing. The one thing you do not want to do is cast the impression of desparation or move this into a situation which can, in anyway, be painted as a threat to "take my toys and go home".

Jobs are hard to find but they are not worth what you seem to be going through. Someone has to be the adult, in a no win situation it might be better to withdraw gracefully rather than force a confrontation that (based on relative "power") - you will lose.

If you can get the manager to document your contributions to the success of the project, since it was brought back in-house, thats even better. It'll make a great recommendation while you (discreetly) search for a better position.