🪴 Brain

Claudex Loop

5 min read

Claudex Loop

🗒️ chaseai-yt/claudex-loop — a Claude Code plugin that makes two rival models harden a plan before a line of code exists, then swap jobs to build it. Claude locks intent with you; OpenAI Codex — a different provider’s model — attacks the locked plan round after round until it can’t find anything else wrong. MIT.

🚀 The invariant that makes it work: whoever made the thing never checks the thing. Plan by Claude → attacked by Codex. Code by Codex → reviewed by Claude. Code by Claude → inspected by Codex. No model grades its own work, on any path.

Description

🧩 The four phases:

PhaseWhat happensWhat makes it different
🔍 0 — RECONClaude scouts before asking anything — explores the codebase and living docs, or on greenfield researches prior art, stacks and known pitfalls (research depth is a gate you control, up to multi-agent deep research)Opens with an Assumptions Ledger you batch-confirm in one reply, so the interview never wastes questions the code already answered
🎯 1 — INTERROGATEA visible decision map splits open decisions into load-bearing (asked one at a time) and cosmetic (batched, veto-by-exception)Every question must justify itself: why it matters, a committed recommendation, and what breaks if we guess wrong. Escape hatch: “accept all remaining recommendations”
⚔️ 2 — REVIEWCodex reviews PLAN.md in a read-only sandbox → VERDICT: APPROVED or REVISE with concrete flaws. Claude arbitrates (rejecting bad critiques with logged reasons), revises, and resumes the same Codex sessionThe reviewer remembers its prior findings and attacks its own accepted fixes. Bounded by MAX_ROUNDS — a flagged deadlock beats a fake “approved”
🔨 3 — BUILD (optional)You pick the builder. Codex builds (full write access) → Claude reads the whole diff like a contributor PR and runs the proof test itself. Or Claude builds → a fresh read-only Codex session cross-inspects the diff against the planSkipping the inspection requires an explicit, logged opt-out

You enter at four points only: confirming the ledger, answering the interview, signing off the converged plan, and approving the final diff.

Two artifacts every run: PLAN.md (the what) and PLAN-REVIEW-LOG.md (the round-by-round argument — the why).

Download or use

/plugin marketplace add chaseai-yt/claudex-loop
/plugin install claudex-loop@claudex-loop

Skills arrive namespaced: /claudex-loop:claudex-loop, /claudex-loop:codex-review, /claudex-loop:codex-build. Intent triggering works regardless — “claudex this plan” fires the right skill. Manual copy into ~/.claude/skills/ gives you bare skill names instead.

Prerequisites:

  • Codex CLI ≥ 0.130 — npm install -g @openai/codex@latest
  • Authenticated — codex login once (any ChatGPT account, Free through Max)
  • Don’t pin a model — ChatGPT-account auth rejects gpt-5.x-codex variants; the skills use your config default and echo the active model at kickoff so you can veto before a round burns

Reasoning for

This is the cleanest packaging I’ve seen of the idea that a model can’t grade its own plan — it turns “get a second opinion” into an enforced protocol with a written argument transcript. It slots directly into the planning gap in Agentic Coding and is a concrete instance of the cross-model patterns in Swarm Research — Orchestrating Coding Agents.

The receipts are what sell it. From the first end-to-end greenfield run (a solo-creator CRM):

  • 55 findings across 5 rounds — converging 26 → 15 → 12 → 2 → 0
  • 1 fatal — an access-path architecture that could not be built as written, and read as completely plausible
  • ~6 wrong models that would have shipped and corrupted data weeks later
  • ~7 missing subsystems, including a homepage feature with no backing data source
  • What survived untouched: every product decision from the interview — the review only ever attacked how it would break

Worth pairing with Ponytail (YAGNI-first code) so the hardened plan doesn’t get built bigger than it needs to be.

Tunables

SkillVarDefaultMeaning
claudex-loopresearchasknone / web / deep — pre-answers the Phase 0 research gate
review skillsMAX_ROUNDS5Hard cap on review rounds
review skillsPLAN_FILEPLAN.mdWhere the plan lives
allLOG_FILEPLAN-REVIEW-LOG.mdThe argument transcript
codex-buildSPEC_FILEPLAN.mdThe frozen spec Codex implements
codex-buildMAX_FIX_ROUNDS2Fix rounds before Claude takes over
codex-buildPROOF_CMDfrom specThe exact test command that counts as proof

Pass e.g. rounds=3 when invoking to override.

⚠️ Safety

Review (phases 0–2) — Codex runs read-only every round: -s read-only on the first call, -c sandbox_mode="read-only" on every resume. This matters: the resume subcommand doesn’t accept -s, so without forcing read-only it inherits your config.toml sandbox default, which may be danger-full-access. The skills handle it for you.

codex-build (phase 3) deliberately inverts this — Codex gets full write access, which is why the skill gates it hard: clean git tree before launch, Claude reads every line of the diff and runs the proof itself, bounded fix rounds, human-gated commits. Resume calls need the long --dangerously-bypass-approvals-and-sandbox flag, and always resume by explicit thread_id, never --last.

Alternatives considered

  • Plan mode alone — same model writes and grades; that’s the echo chamber this exists to break.
  • Superpowers brainstorming / spec-first skills — great at reaching a plan, but the plan is still single-model. Claudex Loop is the adversarial layer you bolt on after.
  • Manual “ask another model” — works, but nothing accumulates: no session memory of prior findings, no arbitration log, no bounded convergence.

Predecessors: this repo was grill-me-codex, then crucible; GitHub redirects the old URLs and the old skills live in legacy/. Act 1 of the legacy skills is © Matt Pocock (MIT); phase 3’s Codex-as-builder pattern is adapted from Peter Steinberger’s codex-first.

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