I've been on H1B for 2 years (greater than 183 days). I filed dual status the first year. I undertand that this year I have to file my taxes as a resident. Can I still claim treaty benefits between US and my country of residence? That is, can I file 1040(R) and form 8833? If no, then what's the most beneficial way for me to file my taxes as an H1B with substantial residency.

Thank you.

Generally, once you start filing as a resident alien, you LOSE all treaty benefits.

There are exceptions, but they are rare.