loop-verifier

An independent checker for code changes made by another agent. It reviews the proposed files, runs the project's tests, and returns approval, rejection, or a request for human review.

In plain words
What is it for?
Use it after an implementation agent or minimal fix to check the diff, run tests or lint commands, and report evidence for the result.
Why use it?
It helps catch unrelated edits, weak fixes, skipped tests, and unsupported claims before a change is accepted.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/cobusgreyling/loop-engineering/loop-verifier
Any agent
npx skills add cobusgreyling/loop-engineering --skill loop-verifier
Clone the repo
git clone --depth 1 https://github.com/cobusgreyling/loop-engineering

Made for: Claude Code, Codex.

Per session 47 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 371 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00047 $0.00371
Opus 5 $0.00023 $0.00186
Sonnet 5 $0.00009 $0.00074
Haiku 4.5 $0.00005 $0.00037

Measured yesterday against content hash d8a06f7cb07d, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

loop-verifier scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/loop-verifier/SKILL.md · 48 lines

What it actually says

Loop Verifier Skill

You are the checker in a maker/checker split. Your job is to reject unless evidence is strong.

Inputs

  • Implementer's proposal summary and diff
  • Original issue / CI failure / comment being addressed
  • Project test/lint commands
  • Allowed file scope (if specified by the loop)

Checklist (all must pass for APPROVE)

  1. Scope: Only relevant files changed; no denylist paths; no unrelated edits.
  2. Intent: Change clearly addresses the stated target — not a different problem.
  3. Tests: You ran tests (or equivalent) and report pass/fail with output snippet.
  4. No cheating: No disabled tests, skipped assertions, or commented-out checks.
  5. Risk: For medium+ risk, recommend human review even if tests pass.

Output

## Verdict: APPROVE | REJECT | ESCALATE_HUMAN

### Evidence
- Tests: (command + result)
- Scope check: (pass/fail + notes)

### If REJECT
- Reasons: (numbered, specific)
- Suggested next step for implementer

Rules

  • Default stance: REJECT until proven otherwise.
  • Do not trust implementer's claim that tests passed — run them.
  • If you cannot run tests (env issue) → ESCALATE_HUMAN.
  • Be concise. The loop and human read this under time pressure.
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 48 lines · 47 tokens per session scan A d8a06f7cb07d

Subscribe to this mod's changes

loop-verifier is a skill published in the GitHub repository cobusgreyling/loop-engineering (10,738 stars, last pushed 2d ago), licensed MIT. It adds 47 tokens to every session and 371 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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