crash-analysis

crash-analysis is a skill for Claude Code, Codex from daedalus/fuzzer. It costs 162 tokens per session (2,015 once invoked), scanned C, original, MIT.

A crash investigation guide for failures found by fuzzing, a method that feeds software many unusual inputs to uncover bugs.

In plain words
What is it for?
Use it to investigate crashes such as segmentation faults, create regression tests, minimize failing inputs, and record findings.
Why use it?
It organizes crash evidence so you can reproduce a failure, classify it, and work out what caused it.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to investigate crashes such as segmentation faults, create regression tests, minimize failing inputs, and record findings.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/daedalus/fuzzer/crash-analysis
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 daedalus/fuzzer --skill crash-analysis
Clone the repo
git clone --depth 1 https://github.com/daedalus/fuzzer

Made for: Claude Code, 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.

agentmods badge for crash-analysis

README.md
[![agentmods](https://agentmods.dev/badge/skills/daedalus/fuzzer/crash-analysis/github.svg)](https://agentmods.dev/skills/daedalus/fuzzer/crash-analysis)
Your own site
<a href="https://agentmods.dev/skills/daedalus/fuzzer/crash-analysis"><img src="https://agentmods.dev/badge/skills/daedalus/fuzzer/crash-analysis/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 crash-analysis

Your own site · 80×15
<a href="https://agentmods.dev/skills/daedalus/fuzzer/crash-analysis"><img src="https://agentmods.dev/badge/skills/daedalus/fuzzer/crash-analysis.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 162 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,015 The whole file, excluding the scripts and references it only reads on demand.
Security scan C 1 finding. 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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00162 $0.02015
Opus 5.5 $0.00065 $0.00806
Sonnet 5.5 $0.00032 $0.00403
Haiku 4.5 $0.00016 $0.00201

Measured 15d ago against content hash 52e506378b5d, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade C, and why

crash-analysis scanned grade C 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 15d 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.

Recursive force deletehighDestructive command

rm -rf with a variable or a broad path is one typo away from removing the wrong tree.

> Mistake: running ``rm -rf crashes/*`` between analysis sessions.
skills/crash-analysis/SKILL.md · 183 lines

How it starts

The opening of the file, as written. The whole thing — 183 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Crash Analysis

Reproduce, classify, and attribute crash artifacts from fuzzing campaigns using the project's sidecar format and existing analysis tooling.


When to Use This Skill

  • "analyze this crash"
  • "why did it segfault"
  • "build a regression test for this crash"
  • "generate a FINDINGS.md entry for this bug"
  • "root cause this SIGFPE"
  • "find the mutation site"
  • "ASAN heap-buffer-overflow" / "UAF" / "UAF in libfoo"
  • "crash forensics"
  • "crash report" / "crash artifact"
  • "minimize this crash input"

Crash Artifact Format

The fuzzer writes a quintet of sidecar files per crash (via save_crash in adapters/filesystem.py):

crashes/
  crash_<ts>_<cluster_id>_<san>_<err>.bin   ← raw input bytes (only file counted as "crash")
  crash_<ts>_<cluster_id>_<san>_<err>.txt   ← human-readable report (target, returncode, GDB replay)
  crash_<ts>_<cluster_id>_<san>_<err>.json  ← same fields, machine-readable (CrashMetadata.to_dict())
  crash_<ts>_<cluster_id>_<san>_<err>.hex   ← xxd-style hexdump + text repr
  crash_<ts>_<cluster_id>_<san>_<err>.sh    ← base64 reproducer script

<san>_<err> is e.g. addr_heapbufferoverflow, or sig_signal11 without a sanitizer report (_crash_name_parts).

The .bin is the authoritative input; the .txt and .json carry the same triage fields (sanitizer, error_type, fault_addr, frames, registers, gdb_replay, nearest_corpus, raw_stderr) — .txt for humans, .json for dashboards and downstream tooling. The two are written together by save_crash; treat them as a single artifact.


Core Methodology

1. Discover

Glob crashes/*.bin to enumerate inputs. Each .bin already has a companion .json sidecar with the parsed triage fields — read those directly:

jq '{returncode, sanitizer, error_type, fault_addr}' crashes/*.json

The .json is written by save_crash and mirrors CrashMetadata.to_dict() (sanitizer, error_type, fault_addr, frames, registers, gdb_replay, nearest_corpus_file, raw_stderr, target_sha256, returncode). No re-parse of the .txt is needed.

Read the full file on GitHub · 183 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. 15d ago Changed · +3 lines 52e506378b5d
  2. 1mo ago First seen · 180 lines · 162 tokens per session scan C 6dd8e5fca8be

Subscribe to this mod's changes

crash-analysis is a skill published in the GitHub repository daedalus/fuzzer (45 stars, last pushed today), licensed MIT. It adds 162 tokens to every session and 2,015 once invoked, about $0.0006 per session on Opus 5.5. A static security scan graded it C with 1 finding (recursive force delete). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-04.

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