aflpp

aflpp is a skill for Claude Code from marduk191/qwen3_mcp. It costs 33 tokens per session (5,238 once invoked), scanned A, a copy of aflpp, MIT.

A tool for fuzz testing C and C++ programs by repeatedly sending them changed or unexpected input. Fuzz testing looks for crashes and other failures automatically.

In plain words
What is it for?
Use it to test mature C or C++ codebases, try many input variations, and increase test coverage when another fuzzer has stopped finding new paths.
Why use it?
It helps find bugs that ordinary tests may miss, and can spread the testing work across multiple computer cores.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: positional $N argument.

Part of the testing-handbook-skills plugin — 15 skills shipped together

Good fit Use it to test mature C or C++ codebases, try many input variations, and increase test coverage when another fuzzer has stopped finding new paths.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/marduk191/qwen3_mcp/aflpp
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 marduk191/qwen3_mcp --skill aflpp
Clone the repo
git clone --depth 1 https://github.com/marduk191/qwen3_mcp

Made for: Claude Code.

Or install testing-handbook-skills, the plugin that ships this one along with the rest of its 15 skills.

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 aflpp

README.md
[![agentmods](https://agentmods.dev/badge/skills/marduk191/qwen3_mcp/aflpp/github.svg)](https://agentmods.dev/skills/marduk191/qwen3_mcp/aflpp)
Your own site
<a href="https://agentmods.dev/skills/marduk191/qwen3_mcp/aflpp"><img src="https://agentmods.dev/badge/skills/marduk191/qwen3_mcp/aflpp/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.

agentmods 80×15 button for aflpp

Your own site · 80×15
<a href="https://agentmods.dev/skills/marduk191/qwen3_mcp/aflpp"><img src="https://agentmods.dev/badge/skills/marduk191/qwen3_mcp/aflpp.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 33 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 5,238 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin 81% 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 $0.00033 $0.05238
Opus 5 $0.00016 $0.02619
Sonnet 5 $0.00007 $0.01048
Haiku 4.5 $0.00003 $0.00524

Measured 10d ago against content hash cb4aa4b4f64b, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

aflpp scanned grade A with 1 finding 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.

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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

curl -O https://raw.githubusercontent.com/AFLplusplus/AFLplusplus/stable/utils/argv_fuzzing/argv-fuzz-inl.h
Origin

This is a copy

81% identical to aflpp — 138 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.

skills/testing-handbook-skills/skills/aflpp/SKILL.md · 641 lines

How it starts

The opening of the file, as written. The whole thing — 641 lines — stays where its author put it; the contents beside it link to each section on GitHub.

AFL++

AFL++ is a fork of the original AFL fuzzer that offers better fuzzing performance and more advanced features while maintaining stability. A major benefit over libFuzzer is that AFL++ has stable support for running fuzzing campaigns on multiple cores, making it ideal for large-scale fuzzing efforts.

When to Use

Fuzzer Best For Complexity
AFL++ Multi-core fuzzing, diverse mutations, mature projects Medium
libFuzzer Quick setup, single-threaded, simple harnesses Low
LibAFL Custom fuzzers, research, advanced use cases High

Choose AFL++ when:

  • You need multi-core fuzzing to maximize throughput
  • Your project can be compiled with Clang or GCC
  • You want diverse mutation strategies and mature tooling
  • libFuzzer has plateaued and you need more coverage
  • You're fuzzing production codebases that benefit from parallel execution

Quick Start

extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
    // Call your code with fuzzer-provided data
    check_buf((char*)data, size);
    return 0;
}

Compile and run:

# Setup AFL++ wrapper script first (see Installation)
./afl++ docker afl-clang-fast++ -DNO_MAIN=1 -O2 -fsanitize=fuzzer harness.cc main.cc -o fuzz
mkdir seeds && echo "aaaa" > seeds/minimal_seed
./afl++ docker afl-fuzz -i seeds -o out -- ./fuzz

Installation

AFL++ has many dependencies including LLVM, Python, and Rust. We recommend using a current Debian or Ubuntu distribution for fuzzing with AFL++.

Method When to Use Supported Compilers
Ubuntu/Debian repos Recent Ubuntu, basic features only Ubuntu 23.10: Clang 14 & GCC 13Debian 12: Clang 14 & GCC 12
Docker (from Docker Hub) Specific AFL++ version, Apple Silicon support As of 4.35c: Clang 19 & GCC 11
Docker (from source) Test unreleased features, apply patches Configurable in Dockerfile
From source Avoid Docker, need specific patches Adjustable via LLVM_CONFIG env var

Read the full file on GitHub · 641 lines

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. 10d ago First seen · 641 lines · 33 tokens per session scan A cb4aa4b4f64b

Subscribe to this mod's changes

aflpp is a skill published in the GitHub repository marduk191/qwen3_mcp (13 stars, last pushed 7mo ago), licensed MIT. It adds 33 tokens to every session and 5,238 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). It is 81% identical to aflpp, differing in 138 lines, and is treated as a copy.

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