Arcee AI Open-Sourced 'nac', a Long-Running Agent Harness, and Argues Harnesses Are Becoming a New Kind of Inference Runtime

Arcee AI Blog·low signalXBlueskyLinkedInCopy link

Arcee AI published NAC on 2026-08-13 (Apache-2.0, Rust, github.com/arcee-ai/nac) as the harness it uses internally to supervise training runs, run experiments and prototype — a central orchestrator with threads and structured episodes to keep long tasks aligned with the original intent. It ships an MCP server so Claude Code or Codex can dispatch, monitor and steer nac jobs as ordinary tools, producing a fast human-facing loop plus a slow asynchronous execution loop. Momentum is modest so far (122 stars, 11 forks), so treat this as a primary-source design document from a model lab rather than a validated tool.