for investigative analysis over large, messy evidence collections where hosted frontier models are ruled out, CLEO admits only the tools, guardrails, memory policies, and loop components that measurably improve accuracy on an expert-validated dataset. The resulting harness reaches an 83.8% pass rate on held-out data — within 1.2 points of the strongest out-of-the-box Claude Code SDK baseline — while being two orders of magnitude smaller and auditable. The fleet's own harness-first playbook, measured.