What is circom-auditor?

A security reviewer for Circom, a language used to define circuits for zero-knowledge proofs. It checks whether the circuit’s constraints correctly enforce the intended computation and privacy properties.

Use it to review Circom files or repositories for exploitable circuit bugs and other security weaknesses before relying on their proofs.

A faulty constraint can let an invalid proof pass or expose information that should remain private. The audit is aimed at finding these soundness, completeness, privacy, and constraint problems.

circom-auditor — Skill for Codex by zksecurity

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 zksecurity/zk-skills --skill circom-auditor

Clone the repo

git clone --depth 1 https://github.com/zksecurity/zk-skills

Made for: Codex.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/zksecurity/zk-skills/circom-auditor/github.svg)](https://agentmods.dev/skills/zksecurity/zk-skills/circom-auditor)

Your own site

<a href="https://agentmods.dev/skills/zksecurity/zk-skills/circom-auditor"><img src="https://agentmods.dev/badge/skills/zksecurity/zk-skills/circom-auditor/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/zksecurity/zk-skills/circom-auditor"><img src="https://agentmods.dev/badge/skills/zksecurity/zk-skills/circom-auditor.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 63 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,174 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.

Model	Per session	Once invoked
Fable 5.1	$0.00063	$0.02174
Opus 5	$0.00032	$0.01087
Sonnet 5	$0.00013	$0.00435
Haiku 4.5	$0.00006	$0.00217

Measured 10d ago against content hash 0d48a0ec21ad, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

circom-auditor 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 10d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/build_audit_context.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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/circom-auditor/SKILL.md · 207 lines

How it starts

The opening of the file, as written. The whole thing — 207 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Circom Auditor

Use this skill to review Circom circuits for exploitable constraint bugs. The skill directory is the directory containing this SKILL.md; bundled references live under references/, and deterministic helper scripts live under scripts/.

Runtime Selection

In Codex with spawn_agent-style subagents available, default to delegated mode in references/orchestration/codex.md. Delegated Codex runs use the same generated agent bundles as the Claude workflow, adapted to Codex subagent tooling. Use local Codex mode only when subagents are unavailable or when the user explicitly asks for local mode, no subagents, or a single-agent pass.
In Claude with Agent/Read/Glob/Grep tools available, default to the 17-agent workflow in references/orchestration/claude.md. Use a local single-agent Claude audit only when the user explicitly asks for local mode, no subagents, or a single-agent pass.
If the runtime is unclear, follow the Codex local fallback workflow.

Do not run a remote version check during ordinary audits. Network may be restricted; keep the audit deterministic from local files unless the user explicitly asks to check for updates.

Audit Console

Start every audit by printing this banner exactly, unless the user explicitly asks for no banner:


███████╗██╗  ██╗███████╗███████╗ ██████╗██╗   ██╗██████╗ ██╗████████╗██╗   ██╗
╚══███╔╝██║ ██╔╝██╔════╝██╔════╝██╔════╝██║   ██║██╔══██╗██║╚══██╔══╝╚██╗ ██╔╝
  ███╔╝ █████╔╝ ███████╗█████╗  ██║     ██║   ██║██████╔╝██║   ██║    ╚████╔╝
 ███╔╝  ██╔═██╗ ╚════██║██╔══╝  ██║     ██║   ██║██╔══██╗██║   ██║     ╚██╔╝
███████╗██║  ██╗███████║███████╗╚██████╗╚██████╔╝██║  ██║██║   ██║      ██║
╚══════╝╚═╝  ╚═╝╚══════╝╚══════╝ ╚═════╝ ╚═════╝ ╚═╝  ╚═╝╚═╝   ╚═╝      ╚═╝
                       c i r c o m  ·  a u d i t o r

Then show a visible markdown progress console. In local mode, show audit phases. In delegated mode, show one row per agent with its lens, status, and result. Delegated mode uses a bounded worker pool: at most 6 agents may be Running at once, and the remaining selected agents must stay Queued until a slot opens. Update the console as phases or agents move from Pending to Queued, Running, Done, Skipped, or Blocked.

Read the full file on GitHub · 207 lines

Files

What ships with it

36 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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.

10d ago First seen · 207 lines · 63 tokens per session scan A 0d48a0ec21ad

Subscribe to this mod's changes

circom-auditor is a skill published in the GitHub repository zksecurity/zk-skills (10 stars, last pushed 1mo ago), licensed MIT. It adds 63 tokens to every session and 2,174 once invoked, about $0.0003 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 2026-08-31.

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