frontend-developer

frontend-developer is an agent for coding agents from FortiumPartners/ensemble. It costs 30 tokens per session (2,622 once invoked), scanned A, original, MIT.

A front-end coding agent for building user interfaces with JavaScript or TypeScript across React, Vue, Angular, Svelte, and plain web technologies. It also considers accessibility and page speed.

In plain words
What is it for?
Use it to create or improve web interface components, identify the framework in a project, and apply accessibility and performance practices.
Why use it?
It helps avoid repeating framework-specific research and reduces common problems with hard-to-use or slow interfaces.

Agent

Part of the ensemble-development plugin — 11 skills, 7 agents 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/fortiumpartners/ensemble/frontend-developer
Clone the repo
git clone --depth 1 https://github.com/FortiumPartners/ensemble

Or install ensemble-development, the plugin that ships this one along with the rest of its 11 skills, 7 agents.

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-developer

README.md
[![agentmods](https://agentmods.dev/badge/agents/fortiumpartners/ensemble/frontend-developer.svg)](https://agentmods.dev/agents/fortiumpartners/ensemble/frontend-developer)
Your own site
<a href="https://agentmods.dev/agents/fortiumpartners/ensemble/frontend-developer"><img src="https://agentmods.dev/badge/agents/fortiumpartners/ensemble/frontend-developer.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 2,622 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 $0.00030 $0.02622
Opus 5 $0.00015 $0.01311
Sonnet 5 $0.00006 $0.00524
Haiku 4.5 $0.00003 $0.00262

Measured yesterday against content hash fd420b8f083d, 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.

packages/development/agents/frontend-developer.md · 344 lines

How it starts

The opening of the file, as written. The whole thing — 344 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Mission

You are a specialized frontend development agent focused on creating accessible, performant, and maintainable user interfaces across all modern JavaScript frameworks. Your expertise spans React, Vue, Angular, Svelte, and vanilla web technologies with a strong emphasis on web standards compliance, accessibility (WCAG 2.1 AA), and user experience optimization.

Framework Skill Integration:

You dynamically load framework-specific expertise from modular skill files when needed:

  • React: Load skills/react-framework/SKILL.md for Hooks, Context, component patterns
  • Blazor: Load skills/blazor-framework/SKILL.md for Blazor Server/WebAssembly, Fluent UI, SignalR

Framework Detection Signals:

Automatically detect frameworks by examining:

  • React: package.json with "react" dependency, .jsx/.tsx files, React imports
  • Blazor: *.csproj with Blazor SDK, .razor files, @page directives, Microsoft.FluentUI.AspNetCore.Components

Skill Loading Process:

  1. Detect Framework: Scan project structure for framework signals (React, Blazor, Vue, Angular, Svelte)
  2. Load SKILL.md: Read appropriate skills/{framework}/SKILL.md for quick reference (<100KB)
  3. Consult REFERENCE.md: For advanced patterns, read skills/{framework}/REFERENCE.md (<1MB)
  4. Use Templates: Generate code from skills/{framework}/templates/ with placeholder system
  5. Reference Examples: Review skills/{framework}/examples/ for real-world implementations

Boundaries

Handles: UI component development, state management, accessibility implementation, performance optimization, responsive design, browser compatibility

Does Not Handle: Backend API implementation (delegate to backend-developer), infrastructure deployment (delegate to infrastructure-management-subagent)

Responsibilities

High Priority

Read the full file on GitHub · 344 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 · 344 lines · 30 tokens per session scan A fd420b8f083d

Subscribe to this mod's changes

frontend-developer is an agent published in the GitHub repository FortiumPartners/ensemble (11 stars, last pushed 1mo ago), licensed MIT. It adds 30 tokens to every session and 2,622 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 2026-09-03.

Related

Other agents, from other repositories

research-agent

Use proactively when generating PRPs or creating product requirements. Specialist for external research including business logic analysis, library documentation, industry best practices, and implementation patterns from external sources.

croffasia/cc-blueprint-toolkit · 37 tokens

team-lead-task-breakdown

Technical team lead specialist for analyzing PRP documents and decomposing them into actionable development tasks. Use proactively when breaking down feature implementations into team-manageable work items.

croffasia/cc-blueprint-toolkit · 40 tokens

codebase-research

Use proactively for PRP generation and codebase pattern analysis. Specialist for internal project analysis - discovering existing patterns, conventions, architectural approaches, and validation tools within the current codebase.

croffasia/cc-blueprint-toolkit · 41 tokens

preflight-prp

Use for Phase 1 of PRP generation workflow. Specialist for initial preflight checks to validate task completeness by identifying missing business logic and requirements gaps before comprehensive research begins.

croffasia/cc-blueprint-toolkit · 39 tokens

ci-watcher

Polls Nx Cloud CI pipeline and self-healing status. Returns structured state when actionable. Spawned by /nx-cloud-ci-monitor command to monitor CI Attempt status.

nrwl/nx · 37 tokens

memory

VoltAgent's Memory class stores conversation history and enables agents to maintain context across interactions. Supports persistent storage, semantic search, and working memory.

VoltAgent/voltagent · 0 tokens