A customer service multi-agent system has specialist agents for billing, technical support, and account management. A triage agent classifies incoming queries and routes them to the appropriate specialist. A user's query about a billing error caused by a technical issue requires collaboration between the billing and technical agents. What handoff protocol best handles cross-specialist scenarios?

B is correct because cross-domain issues require a coordinator pattern with context preservation: the handoff package ensures neither specialist must re-gather information the other already collected, the coordinator can sequence specialist consultations appropriately (technical diagnosis informs billing resolution), and the shared context enables coherent final responses. A is wrong because asking users to restart conversations is a severe experience failure — users must re-explain their issue, and the billing-technical connection is lost, likely resulting in repeated misrouting. C is wrong because forcing a single specialist to handle cross-domain issues results in incomplete resolutions — billing cannot diagnose the technical root cause, and technical cannot adjust billing accounts. D is wrong because parallel independent responses from billing and technical agents without coordination produce contradictory or incoherent advice — they lack each other's context and cannot build on each other's analysis.