A guide for finding untested edge cases—unusual inputs or situations that can make software fail. It examines test coverage, meaning which parts of the code are checked by tests.

It is for reviewing test coverage, finding possible failure cases, and checking whether a change is tested well enough.

It helps reveal gaps in tests before those overlooked cases become bugs.

bugmagnet — Skill for Claude Code by pvillega

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 pvillega/claude-templates --skill bugmagnet

Clone the repo

git clone --depth 1 https://github.com/pvillega/claude-templates

Made for: Claude Code.

Or install ct, the plugin that ships this one along with the rest of its 38 skills, 7 agents, 7 hooks.

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/pvillega/claude-templates/bugmagnet.svg)](https://agentmods.dev/skills/pvillega/claude-templates/bugmagnet)

Your own site

<a href="https://agentmods.dev/skills/pvillega/claude-templates/bugmagnet"><img src="https://agentmods.dev/badge/skills/pvillega/claude-templates/bugmagnet.svg" alt="Measured on agentmods" height="20"></a>

Per session 156 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 909 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	$0.00156	$0.00909
Opus 5	$0.00078	$0.00454
Sonnet 5	$0.00031	$0.00182
Haiku 4.5	$0.00016	$0.00091

Measured 8d ago against content hash f6c30c2284a5, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

bugmagnet 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 8d 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.

plugins/ct/skills/bugmagnet/SKILL.md · 104 lines

The source is not reproduced here

No licence file

Read it on GitHub

Files

What ships with it

1 file 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.

references/edge-cases.md 11 KB

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.

8d ago First seen · 104 lines · 156 tokens per session scan A f6c30c2284a5

Subscribe to this mod's changes

bugmagnet is a skill published in the GitHub repository pvillega/claude-templates (23 stars, last pushed 1mo ago), with no licence file. It adds 156 tokens to every session and 909 once invoked, about $0.0008 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.

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

bugmagnet