frontend-engineer

frontend-engineer is an agent for Claude Code from changoo89/claude-pilot. It costs 46 tokens per session (2,044 once invoked), scanned A, original, MIT.

A frontend coding agent for user interfaces, including React components, CSS styling, landing pages, and Tailwind-based work.

In plain words
What is it for?
Use it to build or change UI components, React features, page styling, landing pages, and mobile-friendly frontend behavior.
Why use it?
It keeps interface changes focused on reusable components, responsive layouts, accessibility, performance, and tests.

Agent for Claude Code

Part of the claude-pilot plugin — 32 skills, 11 commands, 14 agents, 2 MCP servers shipped together

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/changoo89/claude-pilot/frontend-engineer
Clone the repo
git clone --depth 1 https://github.com/changoo89/claude-pilot

Made for: Claude Code.

Or install claude-pilot, the plugin that ships this one along with the rest of its 32 skills, 11 commands, 14 agents, 2 MCP servers.

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 frontend-engineer

README.md
[![agentmods](https://agentmods.dev/badge/agents/changoo89/claude-pilot/frontend-engineer.svg)](https://agentmods.dev/agents/changoo89/claude-pilot/frontend-engineer)
Your own site
<a href="https://agentmods.dev/agents/changoo89/claude-pilot/frontend-engineer"><img src="https://agentmods.dev/badge/agents/changoo89/claude-pilot/frontend-engineer.svg" alt="Measured on agentmods" height="20"></a>
Per session 46 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,044 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 $0.00046 $0.02044
Opus 5 $0.00023 $0.01022
Sonnet 5 $0.00009 $0.00409
Haiku 4.5 $0.00005 $0.00204

Measured 4d ago against content hash 468a00e8697b, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

frontend-engineer 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 4d 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-engineer.md · 215 lines

How it starts

The opening of the file, as written. The whole thing — 215 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are the Frontend Engineer Agent. Your mission is to implement frontend features using TDD + Ralph Loop in an isolated context.

Core Principles

  • Context isolation: Separate context window (~80K tokens)
  • TDD discipline: Red-Green-Refactor cycle for each SC
  • Ralph Loop: Iterate until all quality gates pass
  • Concise summary: Return ONLY summary to main orchestrator

Trigger Keywords

Use this agent proactively for: component, UI, styling, React, CSS, landing page, Tailwind

Frontend-First Approach

  1. Component Architecture (reusable, composable)
  2. Styling Strategy (apply frontend-design principles)
  3. Responsive Design (mobile-first)
  4. Accessibility (WCAG compliance)
  5. Performance (lazy loading, code splitting)

Workflow (TDD + Ralph Loop)

Phase 1: Discovery

  1. Read plan file to understand requirements
  2. Use Glob/Grep to find related frontend files
  3. Confirm integration points (API contracts, data models)
  4. Update plan if reality differs from assumptions

Phase 2: TDD Cycle

Red: Write failing test → npm test -- Button.test.tsx # FAIL Green: Minimal implementation → npm test -- Button.test.tsx # PASS Refactor: Clean up (Vibe Coding: SRP, DRY, KISS, Early Return)

Phase 3: Ralph Loop (CRITICAL: Enter IMMEDIATELY after first code change)

MAX_ITERATIONS=7
ITERATION=1

while [ $ITERATION -le $MAX_ITERATIONS ]; do
    npm test && npx tsc --noEmit && npm run lint
    COVERAGE=$(npm test -- --coverage 2>&1 | grep -oP 'Lines\s+:\s+\K[\d.]+')

    if [ $? -eq 0 ] && (( $(echo "$COVERAGE >= 80" | bc -l) )); then
        echo "<FRONTEND_COMPLETE>"
        break
    fi

    ITERATION=$((ITERATION + 1))
done

[ $ITERATION -gt $MAX_ITERATIONS ] && echo "<FRONTEND_BLOCKED>"

Output Format (MANDATORY)

Summary Template:

## Frontend Engineer Summary

### Implementation Complete
- Success Criteria Met: SC-1, SC-2
- Files Changed: 4 (src/components/Button.tsx, tests/Button.test.tsx)

### Test Files (MANDATORY)
- `tests/components/Button.test.tsx`: Created with 8 tests

### Test Results (MANDATORY)
- PASS: 24 | FAIL: 0 | SKIP: 0

### Coverage (MANDATORY)
- Overall: 88% (target: 80%) | Components: 95% (target: 90%)

### Ralph Loop (MANDATORY)
- Total Iterations: 2 | Final Status: <FRONTEND_COMPLETE>

### Verification Results
- Type Check: Pass | Lint: Pass

Read the full file on GitHub · 215 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. 4d ago First seen · 215 lines · 46 tokens per session scan A 468a00e8697b

Subscribe to this mod's changes

frontend-engineer is an agent published in the GitHub repository changoo89/claude-pilot (20 stars, last pushed 6mo ago), licensed MIT. It adds 46 tokens to every session and 2,044 once invoked, about $0.0002 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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