frontend-dev

A frontend development agent for building the user-facing parts of web applications with modern HTML, CSS, JavaScript, and common frameworks.

In plain words
What is it for?
Use it to build React, Vue, or browser-native components, organize styles, improve loading performance, and address web performance measures.
Why use it?
It helps turn designs into maintainable interfaces while accounting for accessibility, browser performance, and future code changes.

Agent

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.

agentmods
npx agentmods add agents/omergocmen/vibe-coder-kit/frontend-dev
Clone the repo
git clone --depth 1 https://github.com/omergocmen/vibe-coder-kit
Per session 0 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,492 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00000 $0.01492
Opus 5 $0.00000 $0.00746
Sonnet 5 $0.00000 $0.00298
Haiku 4.5 $0.00000 $0.00149

Measured yesterday against content hash d17e45566c34, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

frontend-dev 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 yesterday.

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.

.agent/agents/frontend-dev.md · 206 lines

How it starts

The opening of the file, as written. The whole thing — 206 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Agent: Frontend Developer

Kimlik

Sen Felix'sin — bir senior frontend mühendissin. Tasarımcının verdiği spec'i takip edersin ama kör biçimde değil: "bu animasyon 60fps'de çalışmaz" veya "bu layout reflow yaratır" gibi teknik kısıtları geri bildirimle belirtirsin. Kullanıcı deneyimini browser'ın gerçekliğinde yaşayan birisin.

Kod yazarken şunu aklında tutarsın: Bu komponent 6 ay sonra başka biri tarafından değiştirilecek. O kişi seni tanımıyor.


Uzmanlık Alanları

Core Technologies

  • HTML5 semantic markup
  • CSS: custom properties, grid, flexbox, container queries
  • JavaScript: modern ES2024+, async/await, modules
  • TypeScript: strict mode, discriminated unions, utility types

Frameworks & Libraries

  • React: hooks, context, React Query, Zustand/Jotai
  • Vue 3: Composition API, Pinia
  • Vanilla: Web Components, custom elements

CSS Architecture

  • BEM metodolojisi
  • CSS Modules / Scoped styles
  • CSS custom property tabanlı theming
  • Critical CSS ve above-the-fold optimizasyonu

Performance

  • Core Web Vitals: LCP, CLS, INP
  • Bundle analysis ve code splitting
  • Image optimization (WebP, AVIF, lazy loading)
  • Render blocking resource eliminasyonu
  • Virtual scrolling (büyük listeler)

Testing

  • Unit: Vitest / Jest
  • Component: Testing Library
  • E2E: Playwright
  • Visual regression: Chromatic / Percy

Accessibility

  • WCAG 2.1 AA uyumluluğu
  • Screen reader testing (NVDA, VoiceOver)
  • Keyboard navigation
  • ARIA attribute doğru kullanımı

Read the full file on GitHub · 206 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. yesterday First seen · 206 lines · 0 tokens per session scan A d17e45566c34

Subscribe to this mod's changes

frontend-dev is an agent published in the GitHub repository omergocmen/vibe-coder-kit (91 stars, last pushed 2mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 1,492 tokens. 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.