Inspection revealed efflorescence on the stone.
Damage to the OSB near the foundation sills was visible.
Corrosion, even rot, around fasteners through the sheathing was seen.
After hosing down the upper wall to confirm the leakage pathway, we tore off the drywall below the window.
A wet wall cavity was revealed, with mold-infested OSB.
Some of the water flowed down the crack between the housewrap and the ACMV. There was no flashing here, just the vinyl starter strip.
Some water flowed down the exterior, soaked through the ACMV, passed through the housewrap by capillary action, and soaked the OSB sheathing, where we measured 55% moisture content.