Recursive Agent Harnesses

Recursive Agent Harnesses (RAH): harness recursion extends model recursion for long-context coding agents

A new arXiv preprint introduces the Recursive Agent Harness (RAH), a pattern where a parent agent generates executable scripts that spawn parallel subagent harnesses with filesystem tools, code execution, and planning capabilities. The authors frame this as 'harness recursion', a code-first extension of model recursion from recursive language models. Evaluated on the Oolong-Synthetic long-context benchmark, RAH improves over the Codex coding-agent baseline from 71.75% to 81.36% with GPT-5 as backbone, and reaches 89.77% with Claude Sonnet 4.5. The work connects emerging production patterns (e.g., Anthropic's dynamic workflows) to a formal architectural concept.