Route notes
Why this routing works
This routing uses an open-jaw structure across the Atlantic: fly San Francisco to New York City, continue to Paris, then make your own overland connection back to Boston before the final domestic legs through Portland to San Francisco. That setup works well when the trip does not need to return from the same city it arrived into overseas.
With 4 nights in New York City and 20 nights in Paris, the timing is weighted toward one longer international stay while keeping the first stop shorter and easy to fit before the transatlantic segment. The overland break between Paris and Boston is the key planning feature here, since the ticket resumes in Boston rather than Paris.
On the return side, Boston to Portland to San Francisco keeps the final travel in separate domestic segments instead of requiring a single nonstop back to California. In economy, this kind of multi-stop ticket can be a practical way to combine a transatlantic open jaw with additional U.S. city pairs inside one 5-week plan.
For April departures in the apr-jun season, the main logistics consideration is simply keeping enough spacing between the short New York stop, the long Paris stay, and the self-arranged arrival into Boston so the ticketed segments line up cleanly from start to finish.