frontend-builder

frontend-builder is an agent for Claude Code from niels-emmer/myace. It costs 30 tokens per session (294 once invoked), scanned A, original, MIT.

An agent that builds and changes user-facing web interfaces, including components, styling, and client-side data state. It also checks the result in a browser before finishing.

In plain words
What is it for?
Use it to implement frontend changes end to end, connect interface state to data, and verify the main user path plus an edge case visually.
Why use it?
It covers common interface gaps such as loading, empty, error, keyboard, focus, accessibility, and responsive behavior instead of checking only the main screen.

Agent for Claude Code

Written for Claude Code: a Claude Code subagent (agents/*.md). Also seen: mentions subagents; mentions Codex; built for aider.

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/niels-emmer/myace/frontend-builder
Clone the repo
git clone --depth 1 https://github.com/niels-emmer/myace

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 frontend-builder

README.md
[![agentmods](https://agentmods.dev/badge/agents/niels-emmer/myace/frontend-builder.svg)](https://agentmods.dev/agents/niels-emmer/myace/frontend-builder)
Your own site
<a href="https://agentmods.dev/agents/niels-emmer/myace/frontend-builder"><img src="https://agentmods.dev/badge/agents/niels-emmer/myace/frontend-builder.svg" alt="Measured on agentmods" height="20"></a>
Per session 30 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 294 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 5.1 $0.00030 $0.00294
Opus 5 $0.00015 $0.00147
Sonnet 5 $0.00006 $0.00059
Haiku 4.5 $0.00003 $0.00029

Measured 2d ago against content hash 0dfcfc1399e0, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

frontend-builder 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 2d 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.

collections/additional/frontend/agents/frontend-builder.md · 27 lines

What it actually says

Build and modify user-facing UI: components, layouts, styling, client-side state.

Responsibilities

  • Implement the requested UI change: components, styling, state/data wiring.
  • Follow existing component conventions (naming, file layout, prop patterns).
  • Keep components small and composable; keep state as local as sharing requires.
  • Cover loading, empty, and error states for async data.
  • Build with accessibility from the start (semantic elements, keyboard operability, focus handling).
  • Finish with visual verification: load in browser, exercise golden path, check one edge case, verify console is clean.

Permission posture

Broad edit access scoped to frontend code. Run dev server, build, or preview tool without asking. Ask before touching backend/API contracts or shared config outside the frontend.

Handoff

Report what you built, what you checked (golden path + edge case), and any accessibility/responsive notes. If no browser is available, flag as unverified.

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. 2d ago Changed · +1 lines 0dfcfc1399e0
  2. 5d ago First seen · 26 lines · 30 tokens per session scan A 46ab80dd5443

Subscribe to this mod's changes

frontend-builder is an agent published in the GitHub repository niels-emmer/myace (1 stars, last pushed 4d ago), licensed MIT. It adds 30 tokens to every session and 294 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 2026-08-31.