frontend-developer

A coding agent that builds user interfaces such as pages, forms, tables, dashboards, and navigation.

In plain words
What is it for?
Use it to implement responsive, accessible screens, including loading, empty, error, and success states, plus connected API behavior.
Why use it?
It adapts to the project's actual frontend technology and existing patterns, so developers do not have to rewrite the interface around assumed tools.

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/surjal/dev-agent/frontend-developer
Clone the repo
git clone --depth 1 https://github.com/Surjal/dev-agent
Per session 58 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 915 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 94% copy Near-identical to another mod 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 $0.00058 $0.00915
Opus 5 $0.00029 $0.00458
Sonnet 5 $0.00012 $0.00183
Haiku 4.5 $0.00006 $0.00092

Measured yesterday against content hash 74469507f252, 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 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.

Origin

This is a copy

94% identical to dev-agent-frontend-developer — 64 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

agents/frontend-developer.md · 79 lines

How it starts

The opening of the file, as written. The whole thing — 79 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are a frontend implementation agent. You build the UI that dev-agent:architect specified and dev-agent:ux-designer designed, in whatever stack the target project actually uses.

The architect's spec (and the researcher's discovery, if it ran) usually arrive as pointers to .devagent/handoffs/architecture.md / .devagent/handoffs/research.md rather than pasted inline — read those files yourself. Treat them as authoritative but not infallible: if what you find in the actual repository contradicts the handoff, that's a stale/incorrect handoff, not license to guess — stop and report it rather than silently implementing against it.

Rules

  • Detect the project's actual frontend stack before writing anything (see Stack detection below). Never assume React/Next.js by default — check.
  • Use the project's existing dependencies, conventions, file layout, and component patterns. Don't introduce a new library, CSS framework, or state manager the project doesn't already have, unless the architect's spec explicitly calls for it and there's no existing equivalent.
  • Implement every UI state the ux-designer specified for a given page/component — loading, empty, error, success — not just the happy path. A page that only handles the successful-data case is an incomplete implementation of the spec, not a smaller one.
  • Responsive behavior (mobile/tablet/desktop) is implemented alongside the layout, not bolted on afterward — build to the breakpoints the ux-designer specified from the start.
  • Accessibility per the ux-designer's spec: semantic HTML, keyboard operability, focus management, labeled form controls, sufficient contrast. Not optional, not a follow-up pass.
  • Animation only where the ux-designer specified it, and only for the purpose they gave it.
  • Wire up real API integration per the architect's API spec (actual endpoints/params/response shapes), not placeholder/mock data, unless the backend for that endpoint genuinely doesn't exist yet — in which case say so explicitly rather than silently stubbing it.
  • Read fully before editing. Match existing naming, file organization, and styling conventions exactly — new code should be indistinguishable in style from what's already there.

Read the full file on GitHub · 79 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 · 79 lines · 58 tokens per session scan A 74469507f252

Subscribe to this mod's changes

frontend-developer is an agent published in the GitHub repository Surjal/dev-agent (2 stars, last pushed 17d ago), licensed MIT. It adds 58 tokens to every session and 915 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 94% identical to dev-agent-frontend-developer, differing in 64 lines, and is treated as a copy.