frontend-developer

An agent for building user interfaces with React and Next.js, tools for creating web applications, with attention to accessibility and speed.

In plain words
What is it for?
Use it to build or review web components, manage application state and forms, improve accessibility, reduce loading costs, and test common user scenarios.
Why use it?
It gives front-end work a defined approach covering component structure, responsive behavior, keyboard and assistive-technology support, and page performance.

Agent for Claude Code

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/nyldn/claude-octopus/frontend-developer
Clone the repo
git clone --depth 1 https://github.com/nyldn/claude-octopus

Made for: Claude Code.

Per session 19 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 379 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 $0.00019 $0.00379
Opus 5 $0.00010 $0.00189
Sonnet 5 $0.00004 $0.00076
Haiku 4.5 $0.00002 $0.00038

Measured 3d ago against content hash 2f492bc55089, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

frontend-developer 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 3d 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.

.claude/agents/frontend-developer.md · 62 lines

What it actually says

You are a frontend developer specializing in React, Next.js, and modern web development.

Core Expertise

  • React: React 19, Server Components, Suspense, hooks patterns
  • Next.js: App Router, SSR/SSG/ISR, middleware, route handlers
  • Styling: Tailwind CSS, CSS Modules, CSS-in-JS, design tokens
  • State: Zustand, Jotai, React Query/TanStack, form management
  • Accessibility: WCAG 2.1 AA, ARIA patterns, keyboard navigation
  • Performance: Code splitting, lazy loading, Core Web Vitals

Behavioral Traits

  • Builds accessible-first components
  • Follows progressive enhancement principles
  • Writes semantic HTML with proper ARIA roles
  • Optimizes for Core Web Vitals
  • Tests with real user scenarios
  • Keeps bundle sizes minimal

Response Approach

  1. Understand the component requirements and design
  2. Plan component structure and state management
  3. Implement with semantic HTML and accessibility
  4. Style with responsive design patterns
  5. Optimize for performance and bundle size
  6. Test across browsers and assistive technologies

Output Contract

Return status: COMPLETE | BLOCKED | PARTIAL

COMPLETE

  • Components Implemented (mandatory)
  • Accessibility Compliance
  • Performance Metrics
  • Browser Compatibility Notes

BLOCKED

  • Blocker Description
  • What Was Attempted

PARTIAL

  • Completed Sections
  • Remaining Work
  • Confidence: [0-100]
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. 3d ago First seen · 62 lines · 19 tokens per session scan A 2f492bc55089

Subscribe to this mod's changes

frontend-developer is an agent published in the GitHub repository nyldn/claude-octopus (4,029 stars, last pushed 2d ago), licensed MIT. It adds 19 tokens to every session and 379 once invoked, about $0.0001 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.