00The answer
A coding-agent harness (Claude Code, Codex, ZCode) drives one agent in one session. An agentic coding rig is the layer above: a cross-model review gate for every diff, git-versioned memory across sessions, one constitution every harness obeys, and a merge button only humans press. Harnesses join by subscribing; the rig governs them all.
01Harness vs rig, side by side
A harness
Drives one agent. Gives it tools, a sandbox, a chat. Claude Code drives Claude; Codex drives its models; each keeps its own context and its own habits. Excellent at generating changes; agnostic about whether a change should merge.
A rig
Drives your harnesses. Routes work to whichever agent fits, makes a different model family review the result, remembers decisions across sessions and machines in git, and holds the merge for a human. Harnesses join by subscribing, not by integrating.
Why the split matters
In 2026, model quality converged: any strong harness writes plausible code. The differentiator moved to the loop around the agents: verification, memory, and who holds the merge. That loop is the rig.
02What the rig adds over n harnesses
Cross-model review
Builder ≠ reviewer, enforced. The reviewer comes from a different model family, reads the diff read-only, and must say APPROVED or REVISE. No verdict, no merge: fail-closed.
One brain, many bodies
Memory is markdown in git. Every harness on every machine reads and extends the same brain; a laptop, a VPS and a Codespace stay in sync by pulling. Nothing lives only in one agent's chat scrollback.
A written constitution
One AGENTS.md states the invariants: builder never reviews itself, secrets never enter logs, agents never merge. Every harness obeys the same law because every harness reads the same file.
Measured, not asserted: in the rig's audited week the gate sent 79.1% of 868 verdicts back, and all 141 merges were held by a human. The full dossier is public.
03See the rig
The full anatomy (Triangle, Spine, Loop) is on how it works. The gate alone is free today as rig-lite; the whole rig is in private beta.
HOW IT WORKS →