Across the publicly documented 2025–2026 enterprise deployments, single-agent architectures with structured tool-calling outperform multi-agent orchestrations on accuracy, cost, and MTTD for tasks below approximately 12 distinct tool-domains; multi-agent only pays back above that threshold and only when inter-agent state is bounded by a shared structured artifact rather than free-text handoff.

Claim created at publish; review on 60-day cadence. The 'approximately 12' figure is a heuristic derived from the documented deployment record, not a measured constant from a controlled trial; it is expected to refine to an 8–15 band as more enterprise deployment data enters the public record. Anchor sources: Anthropic building-effective-agents guidance (Dec 2024, explicit caution against premature multi-agent complexity); OpenAI Agents SDK production guidance (single-orchestrator pattern documented as default); Microsoft AutoGen Magentic-One paper (arXiv:2411.04468, multi-agent benchmark methodology showing audit complexity); LangGraph production case studies (structured-artifact state pattern in highest-performing deployments). Salesforce Agentforce and ServiceNow Agent Studio are correctly classified as single-orchestrator architectures for the purposes of this claim; they do not provide evidence for or against the multi-agent threshold. Trigger conditions to revisit before next cadence: (a) a peer-reviewed benchmark overturning the ~12 tool-domain threshold using 50+ enterprise deployments with a methodology that separates tool-domain count from task complexity — would move status to Partial or Not holding depending on the direction; (b) a frontier capability shift eliminating delegation-hop overhead through native multi-agent coordination at inference time rather than at the application layer — would move the threshold upward and narrow the single-agent advantage below it; (c) publication of additional enterprise deployment data that refines the single-number heuristic to the expected 8–15 band — would move status to Partial as the band supersedes the single number without invalidating the directional finding. The claim is expected to shift from Holding to Partial within 60 days as the band refinement is the most likely near-term development; this is not a weakness in the claim but the intended review posture.