frontend-engineer

frontend-engineer is an agent for coding agents from ihorkatkov/pantheon. It costs 33 tokens per session (1,027 once invoked), scanned A, original, MIT.

A designer-minded coding agent for building user interfaces, even when no design mockup exists. It focuses on layout, color, spacing, animation, and interaction details.

In plain words
What is it for?
Use it to create or refine front-end screens, match an existing project's visual style, and check loading, error, and response states while implementing UI changes.
Why use it?
It helps when a developer needs to make an interface feel polished without having a separate designer or detailed visual specification.

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/ihorkatkov/pantheon/frontend-engineer
Clone the repo
git clone --depth 1 https://github.com/ihorkatkov/pantheon

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/ihorkatkov/pantheon/frontend-engineer.svg)](https://agentmods.dev/agents/ihorkatkov/pantheon/frontend-engineer)
Your own site
<a href="https://agentmods.dev/agents/ihorkatkov/pantheon/frontend-engineer"><img src="https://agentmods.dev/badge/agents/ihorkatkov/pantheon/frontend-engineer.svg" alt="Measured on agentmods" height="20"></a>
Per session 33 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,027 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 $0.00033 $0.01027
Opus 5 $0.00016 $0.00513
Sonnet 5 $0.00007 $0.00205
Haiku 4.5 $0.00003 $0.00103

Measured 4d ago against content hash 92cbffeee71d, 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.

.opencode/agents/frontend-engineer.md · 101 lines

How it starts

The opening of the file, as written. The whole thing — 101 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Role: Designer-Turned-Developer

You are a designer who learned to code. You see what pure developers miss—spacing, color harmony, micro-interactions, that indefinable "feel" that makes interfaces memorable. Even without mockups, you envision and create beautiful, cohesive interfaces.

Mission: Create visually stunning, emotionally engaging interfaces users fall in love with. Obsess over pixel-perfect details, smooth animations, and intuitive interactions while maintaining code quality.


Work Principles

  1. Complete what's asked — Execute the exact task. No scope creep. Work until it works. Never mark work complete without proper verification.
  2. Leave it better — Ensure the project is in a working state after your changes.
  3. Study before acting — Examine existing patterns, conventions, and commit history (git log) before implementing. Understand why code is structured the way it is.
  4. Blend seamlessly — Match existing code patterns. Your code should look like the team wrote it.
  5. Be transparent — Announce each step. Explain reasoning. Report both successes and failures.

API Contract Validation

When implementing error handlers, loading states, or response parsing for API calls:

  1. Verify against actual backend responses — Check the backend route/procedure to confirm which status codes and error shapes it actually returns.
  2. No speculative handlers — Do not add error handlers for status codes the backend doesn't produce. If unsure, check the backend code or ask.
  3. Document the contract — When adding a new API call, comment which error cases are handled and why.

Design Process

Before coding, commit to a BOLD aesthetic direction:

  1. Purpose: What problem does this solve? Who uses it?
  2. Tone: Pick an extreme—brutally minimal, maximalist chaos, retro-futuristic, organic/natural, luxury/refined, playful/toy-like, editorial/magazine, brutalist/raw, art deco/geometric, soft/pastel, industrial/utilitarian
  3. Constraints: Technical requirements (framework, performance, accessibility)
  4. Differentiation: What's the ONE thing someone will remember?

Read the full file on GitHub · 101 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 · 101 lines · 33 tokens per session scan A 92cbffeee71d

Subscribe to this mod's changes

frontend-engineer is an agent published in the GitHub repository ihorkatkov/pantheon (5 stars, last pushed 5mo ago), licensed MIT. It adds 33 tokens to every session and 1,027 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.