verifier

An agent that runs the verification checks declared for a project and reports whether each one passed or failed. These checks can include linting, type-checking, tests, builds, drift checks, and commit-message checks.

In plain words
What is it for?
Use it to inspect the current code changes before committing. It only runs sensors defined in .charter/sensors/ and ends with an overall pass or fail result.
Why use it?
It provides a single pre-commit report showing which required checks failed and the exact failure information.

Agent

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/verifier
Clone the repo
git clone --depth 1 https://github.com/tacoda/keystone
Per session 24 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 217 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 $0.00024 $0.00217
Opus 5 $0.00012 $0.00109
Sonnet 5 $0.00005 $0.00043
Haiku 4.5 $0.00002 $0.00022

Measured 2d ago against content hash eefe77fa44cc, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

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.

.charter/agents/verifier.md · 36 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 · 36 lines · 24 tokens per session scan A eefe77fa44cc

Subscribe to this mod's changes

verifier is an agent published in the GitHub repository tacoda/keystone (44 stars, last pushed 2mo ago), licensed MIT. It adds 24 tokens to every session and 217 once invoked, about $0.0001 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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