Component: L15H13_ATTN
Hook: blocks.15.attn.hook_z
Layer: 15
Head: 13
Role: Primary B-transfer head. At the final query position, this head selectively reads the second operand B and transfers B-dependent information into the last-token residual stream. Corrupt-B patching through this head strongly shifts the model toward the B-corrupted answer.
Additional note: Operand-transfer head at Layer 15. Second-to-last survivor of iterative head pruning. Paper Fig. 5 states that this head attends from the last token to the second operand B.