Le forum de XCAS

1: ∂(v(t),t) [enter] returns diff(v(t),t,1)
2: ∫(entry(-1),x) [enter] Xcas is closed

now
1: ∂(v(t),t) [enter] returns diff(v(t),t,1)
2: ∫(ans(-1),t) [enter] returns 0, The expected result is v(t)

The crash will be fixed by returning an error. It's too complicated to support entry in highly recursive algorithms like integration.