what should i do here? whole house needs major renos so can't replace siding right now. should i be patching this somehow?

If not replacing siding, buy some flashing to cover the exposed metal part at the top of the siding, screw it into the brick with some masonry screws and caulk the top edge and side edges of the flashing as well as the screws holding the flashing in place. You'll also need to find a way to seal the sides of the siding that don't extend all the way to the wall, maybe a deep piece of z flashing that you then also would screw into the wall and go over the top of the siding. Then you'd caulk every side of that flashing as well. At this point you'll think to yourself, why the hell didn't I just replace this little chunk of siding and save myself all this trouble if I'm going to eventually replace the siding anyway?

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