harden

harden is a skill for Claude Code from wpgaurav/claude-code-skills. It costs 32 tokens per session (2,264 once invoked), scanned A, a copy of harden, MIT.

An interface testing and improvement guide for handling errors, unusual inputs, different languages, and real-world usage conditions.

In plain words
What is it for?
Use it to check edge cases, API and validation errors, text overflow, right-to-left languages, special characters, dates, numbers, and currencies.
Why use it?
It helps find failures that only appear with long text, empty data, network problems, permission errors, many items, or translations that take more space.

Skill for Claude Code

Written for Claude Code: argument-hint in frontmatter. Also seen: positional $N argument.

Needs its repository: it reads a path above its own folder, which exists only inside the repository. The line is Adapted from [impeccable](https://github.com/pbakaus/impeccable) by Paul Bakaus, used under the Apache License 2.0. Modified for this collection; see [NOTICE.md.

Good fit Use it to check edge cases, API and validation errors, text overflow, right-to-left languages, special characters, dates, numbers, and currencies.

Compare 6 skills from other repositories ↓
Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/wpgaurav/claude-code-skills
agentmods
npx agentmods add skills/wpgaurav/claude-code-skills/harden

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.

agentmods badge for harden

README.md
[![agentmods](https://agentmods.dev/badge/skills/wpgaurav/claude-code-skills/harden.svg)](https://agentmods.dev/skills/wpgaurav/claude-code-skills/harden)
Your own site
<a href="https://agentmods.dev/skills/wpgaurav/claude-code-skills/harden"><img src="https://agentmods.dev/badge/skills/wpgaurav/claude-code-skills/harden.svg" alt="Measured on agentmods" height="20"></a>
Per session 32 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,264 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 92% 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 $0.00032 $0.02264
Opus 5 $0.00016 $0.01132
Sonnet 5 $0.00006 $0.00453
Haiku 4.5 $0.00003 $0.00226

Measured 8d ago against content hash 5239f8239630, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

harden 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.

Origin

This is a copy

92% identical to harden — 12 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.

harden/SKILL.md · 360 lines

How it starts

The opening of the file, as written. The whole thing — 360 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Adapted from impeccable by Paul Bakaus, used under the Apache License 2.0. Modified for this collection; see NOTICE.md for what changed.

Strengthen interfaces against edge cases, errors, internationalization issues, and real-world usage scenarios that break idealized designs.

Assess Hardening Needs

Identify weaknesses and edge cases:

  1. Test with extreme inputs:

    • Very long text (names, descriptions, titles)
    • Very short text (empty, single character)
    • Special characters (emoji, RTL text, accents)
    • Large numbers (millions, billions)
    • Many items (1000+ list items, 50+ options)
    • No data (empty states)
  2. Test error scenarios:

    • Network failures (offline, slow, timeout)
    • API errors (400, 401, 403, 404, 500)
    • Validation errors
    • Permission errors
    • Rate limiting
    • Concurrent operations
  3. Test internationalization:

    • Long translations (German is often 30% longer than English)
    • RTL languages (Arabic, Hebrew)
    • Character sets (Chinese, Japanese, Korean, emoji)
    • Date/time formats
    • Number formats (1,000 vs 1.000)
    • Currency symbols

CRITICAL: Designs that only work with perfect data aren't production-ready. Harden against reality.

Hardening Dimensions

Systematically improve resilience:

Text Overflow & Wrapping

Long text handling:

/* Single line with ellipsis */
.truncate {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

/* Multi-line with clamp */
.line-clamp {
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

/* Allow wrapping */
.wrap {
  word-wrap: break-word;
  overflow-wrap: break-word;
  hyphens: auto;
}

Flex/Grid overflow:

/* Prevent flex items from overflowing */
.flex-item {
  min-width: 0; /* Allow shrinking below content size */
  overflow: hidden;
}

/* Prevent grid items from overflowing */
.grid-item {
  min-width: 0;
  min-height: 0;
}

Read the full file on GitHub · 360 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. 8d ago First seen · 360 lines · 32 tokens per session scan A 5239f8239630

Subscribe to this mod's changes

harden is a skill published in the GitHub repository wpgaurav/claude-code-skills (3 stars, last pushed 17d ago), licensed MIT. It adds 32 tokens to every session and 2,264 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 92% identical to harden, differing in 12 lines, and is treated as a copy.

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