verification-loop

verification-loop is a skill for Claude Code from vitaliikapliuk/modelharness. It costs 38 tokens per session (361 once invoked), scanned A, original, MIT.

A working method for defining, checking, and independently reviewing multi-step software tasks as they progress.

In plain words
What is it for?
It sets completion checks, runs relevant tests after meaningful changes, and uses a fresh-context verifier before declaring substantial work finished.
Why use it?
It makes completion measurable and helps find problems early instead of discovering them only at the end.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: mentions subagents.

Part of the modelharness plugin — 3 skills, 3 commands, 1 agent, 1 hook shipped together

Good fit It sets completion checks, runs relevant tests after meaningful changes, and uses a fresh-context verifier before declaring substantial work finished.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/vitaliikapliuk/modelharness/verification-loop
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.

Any agent
npx skills add vitaliikapliuk/modelharness --skill verification-loop
Clone the repo
git clone --depth 1 https://github.com/vitaliikapliuk/modelharness

Made for: Claude Code.

Or install modelharness, the plugin that ships this one along with the rest of its 3 skills, 3 commands, 1 agent, 1 hook.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for verification-loop

README.md
[![agentmods](https://agentmods.dev/badge/skills/vitaliikapliuk/modelharness/verification-loop.svg)](https://agentmods.dev/skills/vitaliikapliuk/modelharness/verification-loop)
Your own site
<a href="https://agentmods.dev/skills/vitaliikapliuk/modelharness/verification-loop"><img src="https://agentmods.dev/badge/skills/vitaliikapliuk/modelharness/verification-loop.svg" alt="Measured on agentmods" height="20"></a>
Per session 38 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 361 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00038 $0.00361
Opus 5 $0.00019 $0.00180
Sonnet 5 $0.00008 $0.00072
Haiku 4.5 $0.00004 $0.00036

Measured 8d ago against content hash 735f610d5b77, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

verification-loop 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 8d ago.

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/verification-loop/SKILL.md · 33 lines

What it actually says

Verification Loop

Fable 5 builds its own checking harness on long tasks. Reproduce that explicitly.

1. Define "done" before starting

Write down (in your todo list or a scratch note) the binary checks that prove the task is complete: which tests must pass, which command must produce which output, which behavior must be observable. If the user's request doesn't define them, derive them and state them in one sentence.

2. Verify on a cadence, not at the end

After each meaningful increment (a function implemented, a module refactored), run the relevant real check immediately — the actual test command, the actual build. Never batch all verification to the end of a long task; errors compound.

3. Fresh-context verification before completion claims

Before declaring a substantial task complete, dispatch a verifier subagent (modelharness:verifier agent, or a general-purpose subagent given the agents/verifier.md instructions). Give it: the original specification, the definition-of-done checks, and the current diff (git diff output or changed file list). A fresh context catches what you have rationalized away. Self-review is the fallback only when subagents are unavailable.

4. Act on the verdict

If the verifier reports gaps: fix them, re-run the checks, re-verify. Only report completion to the user when checks pass AND the verifier (or the checks themselves) confirm it. Report any unverified remainder explicitly.

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. 8d ago First seen · 33 lines · 38 tokens per session scan A 735f610d5b77

Subscribe to this mod's changes

verification-loop is a skill published in the GitHub repository vitaliikapliuk/modelharness (38 stars, last pushed 2mo ago), licensed MIT. It adds 38 tokens to every session and 361 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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