Story · arXiv
Harness Engineering: Anatomy, Architecture, and Evolution of Coding Agents. A Source-Code Study of Eleven Systems (arXiv)
paper · Story page
Eleven production coding harnesses, Claude Code and Codex CLI through Aider and OpenCode, dissected at source level into seven subsystems and 29 recurring patterns. Across roughly four million lines, none imports a general-purpose agent framework and none retrieves code with vector embeddings.
In plain words
- Researchers examined source code from eleven real coding systems to map how they are built.
- They divided each system into seven parts, including repeated work, tools, information handling, safety, coordination, and add-ons.
- Across roughly four million lines, none used a ready-made package for building action-taking artificial intelligence systems.
- None searched code by turning its meaning into lists of numbers for similarity matching.
- Software builders now have an evidence-based map of common designs and notable choices these systems avoid.
Appeared in
- Google's Mantis bug-fixing harness, and privilege escalation in 12 agent harnesses
Sep 03, 2026 · in the sections
Subscribe
Get the brief in your inbox
Pick daily, weekly, or both. Nothing is gated either way: every issue is on the site and in the feeds.
- Weekdays at 8:45am IST, one lead story and 6 to 9 items.
- Sundays, an argued synthesis rather than a recap.
- One click to leave, and quiet days say so in the subject line.