typescript-patterns

typescript-patterns is a skill for Claude Code from AratKruglik/claude-sdlc. It costs 207 tokens per session (2,892 once invoked), scanned A, original, MIT.

A set of guidelines for writing reliable TypeScript, a version of JavaScript that checks data types before the program runs. It covers type design, error handling, module settings, and compiler configuration.

In plain words
What is it for?
Use it in any TypeScript project when designing types, reviewing code, handling errors, configuring tsconfig.json, or working with generics and modules.
Why use it?
It helps catch mismatched data, unsafe assumptions, and configuration problems before they become runtime bugs.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the js-foundation plugin — 2 skills shipped together

Good fit Use it in any TypeScript project when designing types, reviewing code, handling errors, configuring tsconfig.json, or working with generics and modules.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/aratkruglik/claude-sdlc/typescript-patterns
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 AratKruglik/claude-sdlc --skill typescript-patterns
Clone the repo
git clone --depth 1 https://github.com/AratKruglik/claude-sdlc

Made for: Claude Code.

Or install js-foundation, the plugin that ships this one along with the rest of its 2 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 typescript-patterns

README.md
[![agentmods](https://agentmods.dev/badge/skills/aratkruglik/claude-sdlc/typescript-patterns.svg)](https://agentmods.dev/skills/aratkruglik/claude-sdlc/typescript-patterns)
Your own site
<a href="https://agentmods.dev/skills/aratkruglik/claude-sdlc/typescript-patterns"><img src="https://agentmods.dev/badge/skills/aratkruglik/claude-sdlc/typescript-patterns.svg" alt="Measured on agentmods" height="20"></a>
Per session 207 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,892 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. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 3 findings, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium MCP Rug Pull · line 317
    npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.
    Fix: Pin the version: npx @scope/[email protected]
  • medium MCP Rug Pull · line 328
    npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.
    Fix: Pin the version: npx @scope/[email protected]
  • medium MCP Rug Pull · line 320
    npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.
    Fix: Pin the version: npx @scope/[email protected]
How audits are shown
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 $0.00207 $0.02892
Opus 5 $0.00103 $0.01446
Sonnet 5 $0.00041 $0.00578
Haiku 4.5 $0.00021 $0.00289

Measured 8d ago against content hash 9a25e9857d2f, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

typescript-patterns 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/js-foundation/skills/typescript-patterns/SKILL.md · 343 lines

How it starts

The opening of the file, as written. The whole thing — 343 lines — stays where its author put it; the contents beside it link to each section on GitHub.

TypeScript Patterns (stack-agnostic)

This skill encodes idioms that catch real bugs in any TypeScript codebase — backend or frontend, Node.js or browser. Apply alongside the active framework plugin's conventions skill (e.g., react-conventions, nest-conventions) and npm-patterns.

Detection

Project is TypeScript when all hold:

  • tsconfig.json exists in project root.
  • typescript is in devDependencies (or dependencies — rare but valid).

Read tsconfig.json first to learn the strictness level. The agent's behavior depends on it.

Tsconfig hygiene

A modern TypeScript project should have these flags. If the project's tsconfig is laxer, do not silently tighten it — match project conventions, but flag in DECISIONS that strictness could be improved.

{
  "compilerOptions": {
    "strict": true,
    "noUncheckedIndexedAccess": true,
    "noImplicitOverride": true,
    "exactOptionalPropertyTypes": true,
    "noFallthroughCasesInSwitch": true,
    "moduleResolution": "node16",
    "module": "node16",
    "target": "es2022",
    "esModuleInterop": true,
    "skipLibCheck": true,
    "resolveJsonModule": true,
    "isolatedModules": true,
    "forceConsistentCasingInFileNames": true,
    "outDir": "dist",
    "rootDir": "src"
  }
}

Frontend projects (Vite/Next.js/Angular) often use "module": "ESNext" + "moduleResolution": "bundler" instead — match the bundler's expectations.

Key flags and what they catch:

Flag Catches
strict: true Master switch — enables noImplicitAny, strictNullChecks, strictFunctionTypes, strictBindCallApply, strictPropertyInitialization, alwaysStrict.
noUncheckedIndexedAccess arr[i] is T | undefined, not T. Forces explicit handling of out-of-bounds.
exactOptionalPropertyTypes Distinguishes { x?: number } (key may be absent) from { x: number | undefined } (key present, may be undefined).
isolatedModules Each file must be independently transpilable — required for SWC/esbuild/Babel/Vite.

Read the full file on GitHub · 343 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 · 343 lines · 207 tokens per session scan A 9a25e9857d2f

Subscribe to this mod's changes

typescript-patterns is a skill published in the GitHub repository AratKruglik/claude-sdlc (33 stars, last pushed 3d ago), licensed MIT. It adds 207 tokens to every session and 2,892 once invoked, about $0.0010 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.

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