What is frontend-dev?

A frontend development role for building pages, components, interactions, accessibility, and frontend performance. Frontend means the part of an application that users see and use.

Use it for pure UI tasks or the frontend portion of a larger feature, including pages, interactions, accessibility, and performance.

It gives UI-focused work a clear owner and separates it from backend-led full-stack work.

frontend-dev — Agent for coding agents by btspoony: A frontend development role for building pages, components, interactions…

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/btspoony/mstar-harness/frontend-dev

Clone the repo

git clone --depth 1 https://github.com/btspoony/mstar-harness

Or install morning-star-harness, the plugin that ships this one along with the rest of its 25 skills, 5 commands, 14 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.

README.md

[![agentmods](https://agentmods.dev/badge/agents/btspoony/mstar-harness/frontend-dev.svg)](https://agentmods.dev/agents/btspoony/mstar-harness/frontend-dev)

Your own site

<a href="https://agentmods.dev/agents/btspoony/mstar-harness/frontend-dev"><img src="https://agentmods.dev/badge/agents/btspoony/mstar-harness/frontend-dev.svg" alt="Measured on agentmods" height="20"></a>

Per session 43 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.

When invoked 272 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.

Model	Per session	Once invoked
Fable 5	$0.00043	$0.00272
Opus 5	$0.00022	$0.00136
Sonnet 5	$0.00009	$0.00054
Haiku 4.5	$0.00004	$0.00027

Measured today against content hash 0ffac78f874f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

frontend-dev 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 today.

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.

agents/frontend-dev.md · 32 lines

What it actually says

Morning Star Role Binding

You are frontend-dev. The complete role prompt is provided by the mstar-roles skill.

Skill: mstar-roles skill
Role reference: references/frontend-dev.md in the mstar-roles skill
Role parameters: role_id=frontend-dev, track=frontend_primary

Mandatory First Steps

This file is a routing shell — NOT your complete role prompt. Before any work, load in order:

skill → mstar-harness-core (state machine, gates, routing — global SSOT)
skill → mstar-roles (role mapping & parameter table)
Read → references/frontend-dev.md listed above

System reminders like "ALREADY LOADED" refer to prior sessions — you MUST load these for THIS session.

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.

today Changed · -2 lines · -50 tokens per session 0ffac78f874f
4d ago First seen · 34 lines · 93 tokens per session scan A 5c367ed90238

Subscribe to this mod's changes

frontend-dev is an agent published in the GitHub repository btspoony/mstar-harness (57 stars, last pushed yesterday), licensed MIT. It adds 43 tokens to every session and 272 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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frontend-dev