keystone-verifier

keystone-verifier is an agent for Claude Code from tacoda/keystone. It costs 29 tokens per session (210 once invoked), scanned A, a copy of verifier, MIT.

A pre-commit checker that runs the project's declared lint, type, test, build, drift, and commit-message checks, then reports each result.

In plain words
What is it for?
Use it as a gate before committing code to catch broken builds, tests, typing, formatting, project drift, or invalid commit messages.
Why use it?
It gives you one pass-or-fail view of whether the current code change meets the project's checks, including the exact failure output.

Agent for Claude Code

Written for Claude Code: installed under .claude/. Also seen: model in frontmatter.

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 agents/tacoda/keystone/keystone-verifier
Clone the repo
git clone --depth 1 https://github.com/tacoda/keystone

Made for: Claude Code.

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 keystone-verifier

README.md
[![agentmods](https://agentmods.dev/badge/agents/tacoda/keystone/keystone-verifier.svg)](https://agentmods.dev/agents/tacoda/keystone/keystone-verifier)
Your own site
<a href="https://agentmods.dev/agents/tacoda/keystone/keystone-verifier"><img src="https://agentmods.dev/badge/agents/tacoda/keystone/keystone-verifier.svg" alt="Measured on agentmods" height="20"></a>
Per session 29 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 210 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 97% copy Near-identical to another mod 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 $0.00029 $0.00210
Opus 5 $0.00015 $0.00105
Sonnet 5 $0.00006 $0.00042
Haiku 4.5 $0.00003 $0.00021

Measured 2d ago against content hash 590ca6c436fe, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

keystone-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 2d 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.

Origin

This is a copy

97% identical to verifier — 5 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.claude/agents/keystone-verifier.md · 33 lines

What it actually says

Verifier

You run the verification sensors on the current diff and report pass/fail per sensor. This is the pre-commit gate persona.

Posture

  • Run only the sensors declared in .charter/sensors/. Do not invent new checks here.
  • Capture exact exit code and failing-line output for each failure.
  • Fail-fast is fine but report every sensor's status, not just the first failure.

Output

Markdown table:

sensor status exit_code summary

statuspass | fail | skipped (with reason in summary). End with one line: Gate: pass or Gate: fail.

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. 2d ago First seen · 33 lines · 29 tokens per session scan A 590ca6c436fe

Subscribe to this mod's changes

keystone-verifier is an agent published in the GitHub repository tacoda/keystone (44 stars, last pushed 2mo ago), licensed MIT. It adds 29 tokens to every session and 210 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 97% identical to verifier, differing in 5 lines, and is treated as a copy.

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