"I still work in Boston. I take the train in 3+ days a week and work from home when I don't go to the office. "
MA will tax you as an RI resident only on work actually (physically) performed within MA. Income you earn on the days you work remotely from RI is not taxed by MA.
The income you earned on the days you lived in RI and physically worked in MA is the only income that is taxed by both states.
The income you earned prior to your move to RI is taxable only by MA.
Note that when you are filing two part-year resident state returns, TT recommends that you complete the "old" state return first, before you do the return for your current state.
How do I file a part-year state return? (intuit.com)
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
