ProjectDiscovery shares the engineering evolution of Neo, their agentic security assessment platform, across three architectural phases. Starting from a single agent with a sandbox, they moved to an orchestrator with specialized subagents, and finally to a three-phase plan→execute→verify architecture with parallel subagents. Key lessons include: start simple and split only when context or duration breaks, subagents trade context problems for coordination problems, execution and verification require separate agents with different goals, and parallelism belongs at the worker layer not the orchestrator layer. The current system handles tasks up to 14.7 hours, 2,154 steps, and 2,398 tool calls, with Thorough and Fast execution modes exposed to users.
