This synthesis records claims and practices from the cited sources; reported outcomes and product capabilities have not been independently verified.
Coordinator agents excel at batching work into 3–5 parallel streams with cross-model review (max 5 rounds) and adversarial verification. Production systems require versioned memory, concurrency control, five-stage loops with objective pass/fail verification. Task-level routing yields ~30% savings; heavy front-loaded planning prevents downstream chaos. Cold outbound GTM decomposes into four persistent agents (list builder, copywriter, campaign manager, infrastructure manager), each owning one artifact. Reliable multi-agent handoffs rest on three mechanisms: naming as join key, task-state-as-trigger (completion fires webhook waking next bot), 'blocking out loud' (agents post missing input and stop rather than guess). Claude Code as orchestrator with tools like ColdIQ MCP cut campaign builds from two days to one prompt and ~20 minutes. Ars Umbris functions as meta-harness, connecting multiple agent harnesses via MCP adapters to one durable workspace state. Parallelizing adversarial and browser-driven test runs across many instances makes exhaustive pre-release stress testing economically viable even for small teams, eliminating the tradeoff between thoroughness and resource constraints.