A gated tool for testing the security and robustness of CAPTCHA systems, including local synthetic challenges.

It is used to evaluate CAPTCHA security, benchmark the ReCAP agent, test a local CAPTCHA agent, and measure how well CAPTCHA challenges resist automated solving.

It helps identify weaknesses in CAPTCHA protection under controlled test conditions.

captcha — Skill for Claude Code by grahama1970

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 grahama1970/agent-skills --skill captcha

Clone the repo

git clone --depth 1 https://github.com/grahama1970/agent-skills

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/grahama1970/agent-skills/captcha/github.svg)](https://agentmods.dev/skills/grahama1970/agent-skills/captcha)

Your own site

<a href="https://agentmods.dev/skills/grahama1970/agent-skills/captcha"><img src="https://agentmods.dev/badge/skills/grahama1970/agent-skills/captcha/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/grahama1970/agent-skills/captcha"><img src="https://agentmods.dev/badge/skills/grahama1970/agent-skills/captcha.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 60 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,643 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 unknown 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	$0.00060	$0.02643
Opus 5	$0.00030	$0.01321
Sonnet 5	$0.00012	$0.00529
Haiku 4.5	$0.00006	$0.00264

Measured 9d ago against content hash 5b6b78750dd8, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

captcha 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 9d ago.

The scan reads SKILL.md. This mod also ships 29 executable files (run.sh, sanity.sh, scripts/fcaptcha_reference_eval.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/captcha/SKILL.md · 287 lines

The source is not reproduced here

No licence file

Read it on GitHub

Files

What ships with it

57 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.

9d ago First seen · 287 lines · 60 tokens per session scan A 5b6b78750dd8

Subscribe to this mod's changes

captcha is a skill published in the GitHub repository grahama1970/agent-skills (6 stars, last pushed today), with no licence file. It adds 60 tokens to every session and 2,643 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 2026-09-03.

Security Testing

research-engineer

An uncompromising Academic Research Engineer. Operates with absolute scientific rigor, objective criticism, and zero flair. Focuses on theoretical correctness, formal verification, and optimal implementation across any required technology.

davila7/claude-code-templates · 43 tokens

tika-eval-compare

Compare extracts from two Tika builds over a corpus to detect regressions in content, encoding, exceptions, and embedded-document handling. Use for "compare before/after extracts", "eval this change against the corpus".

apache/tika · 50 tokens

neuron-evaluation-engineer

Create and run AI evaluations with datasets, assertions, and output drivers in Neuron AI. Use this skill whenever the user mentions evaluation, testing AI systems, creating evaluators, dataset-driven testing, assertion-based validation, or wants to measure AI system performance. Also trigger for tasks involving…

neuron-core/neuron-ai · 77 tokens

captcha