Again a little bit of information and a question, expecting a good answer. These typically run to about 18 posts until there is enough to discuss and get a useful answer.
if I add 3 feet long angle or flat plat 38x4.8mm, diagonal around lower corners and one at top of opening extending one foot screw with hiltihit Hy 150 12" o/c attached skech
Ok add all this reinforcing. What are your loads? Many a basement wall has no reinforcing and also has window openings. What is so different here? What is the wall concrete compressive strength? How thick, How tall, horizontal span? To ask few.
it is 9' high 8" thick concrete wall, load on wall is 1800 plf and 8' backfill height , reinforcement 2-15M horizontal rebars ( top middle bottom) 1-15M vertical rebar at 24" 0/c , 32 Mpa at 56 days compressive strength.
If the wall is 9' high, the backfill height appears less than 8'.
Check the wall as built. It may be okay without any further reinforcement. With 2-15M horizontal bars top, the proposed horizontal strap above the window does very little. If the wall spans vertically, the maximum moment is located where the vertical steel is undiminished, much lower than the bottom of window . Moment at the underside of window is considerably less, so the loss of a couple of vertical bars may be okay.
If you did need reinforcing, I would be looking at vertical carbon fiber strips. They are only about $400 a piece installed around here and don't protrude into the potential finished room space.
