回复：you can file 1040 and still covered by the treaty

Why do you use 1040 NR? you can use 1040 even if you're covered by the treaty. If you've lived in the US for >183 days in a calendar year, you're considered as a resident for tax purpose, but you can still pay no tax as long as you're covered by the treaty.

Another tax benefit if you file 1040 is you can claim child tax credit (if you have at least one child and income under certain threshold).

You can use three forms
1040,
8833:Treaty based return position
8812:additonal child tax credit.

1040: on the top of the form, write " treaty-based return position"
on item 7: filled "wages"
on item 21: filled "(wages)", write"us-china tax treaty"
therefore, total taxable wages = 0

A friend of my did it for the past three years.