User A and User B's workload are on the same VLAN, but connected through a transparent layer 2 bridge in use B's ARP table. Which MAC address is reported for user A's workstation?

The bridge port MAC facing User A's segment is learned internally by the bridge as the ingress MAC, but it is not the address that User B's ARP table records for User A.

The bridge's overall management or base MAC is used for traffic directed at the bridge itself, not for forwarded user traffic appearing in downstream ARP caches.

In a bridge that performs MAC substitution, User A's actual workstation MAC is not propagated across the bridge, so it does not appear in User B's ARP table.

When a Layer 2 bridge performs connection proxying or MAC address substitution - common in transparent security appliances and certain load balancer deployments - frames forwarded toward User B originate from the bridge's own port MAC on User B's segment. User B's ARP table therefore records that bridge port MAC as the Layer 2 address for User A's IP, not User A's workstation MAC.