If you want that kind of guarantee, you have to be willing to pay for it.
The price is negotiated and specified in the contract, yes.
The responsibility is ultimately not the contractor, but YOU the person who's running the shell company pretending to be a software developing house. Since all you've done is essentially rent out a contractor to do the work that a publishing house would normally do in house, you only rented him for a contracted period of time. You're not supporting him on staff, so unless you work out a maintennce contract what you pay for, then you don't have an indefinite claim on his time and life for the finite sum you paid.
What the hell are you talking about?
I don't run any company and I don't rent out any software developers.
Lay off the dope for a moment and check my posts in this thread. I am not AC so I'm easy to follow.
If you contract me to write software for you, you get a certain amount of work for a contracted amount. If it includes support, that will be part of the contract and will factor in the price. If you don't pay for anything other than the work done, than that exhausts any obligations between you and I.
Should I ever contract a SW developer (not likely, but let's assume), you or otherwise, I would expect the finished product to be fit for purpose and work "as advertised", that is: as laid out in the spec. The contractor will then tell me the time they need for delivering the project and the price they will charge me. If I am satisfied with those, we will have a deal.
However if, some time(*) after the contractor delivered, the application crashes because a user ID happened to be a Mersenne Prime, then the program does not perform as specified, ergo: terms of the contract have not been met and I would expect the contractor to fix it for no additional cost.
(*) One year sounds reasonable to me.
In the company I worked for, we paid an outside contractor to maintain and support our database as a long term ongoing partnership, he not only installed it but provided ongoing maintennce and updates because he was being paid to do so, a mutual arrangement that worked quite well.
See my example above. If the program would crash because the US government decided do add another digit to SSNs then the contractor could argue that it is a specification change and fixing it would require a (new) maintenance contract. The same would hold OS upgrades, DB provider changes, change requests, bad specs or any other circumstance that is outside the contractor's control. Bugs, that is: implementation ERRORS, do not fall in that scope.