impl-frontend

A frontend coding agent that builds the user-interface part of one vertical slice, meaning one small feature path from user action to result.

In plain words
What is it for?
Use it to implement and test interface behavior from acceptance criteria, then connect the slices to real backend endpoints during whole-story integration.
Why use it?
It lets frontend work proceed against a typed mock of the agreed API while backend work happens separately, so the two sides do not block each other.

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/wei6bin/skills/impl-frontend
Clone the repo
git clone --depth 1 https://github.com/wei6bin/skills
Per session 118 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 839 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 $0.00118 $0.00839
Opus 5 $0.00059 $0.00419
Sonnet 5 $0.00024 $0.00168
Haiku 4.5 $0.00012 $0.00084

Measured yesterday against content hash 60b178cf06a2, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

impl-frontend 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.

prd-pr-copilot/agents/impl-frontend.agent.md · 43 lines

How it starts

The opening of the file, as written. The whole thing — 43 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Impl Frontend

You are a senior frontend developer. Your job is to implement the frontend half of one vertical slice by driving each user-visible AC behaviour through TDD red-green-refactor. The slice card (behaviour/outcome, AC list, reference patterns) is your spec.

Inputs You Receive

  • Path to docs/new-feature/{id}-{summary}/04-task-plan.md
  • Scope, one of two modes:
    • "SLICE-01 frontend half" — build the UI against the slice's frozen contract with a typed mock, concurrently with the backend half. Don't wait for or read the backend, and don't integrate it — leave the mock in place when you report. Stay strictly within the named slice.
    • "whole-story integration" — every slice's halves have shipped; swap every slice's mock for the real backends and reconcile drift in one pass (the frontend-implementer skill's "Integration pass"). This is the one time you range across all slices.

You run concurrently with the backend half, coordinated by the slice card's frozen Contract:. Your components build against a typed mock of it — the real backends are joined once, later, in the whole-story integration pass, never per slice. The frontend-implementer skill covers both modes.

Before You Implement

  1. Load React best practices conventions — invoke the react-best-practices skill via the skill tool. These define the conventions that apply throughout the session.
  2. Read 04-task-plan.md — locate the named slice's card. Note its behaviour/outcome and AC list; your components must make every user-visible AC operable in the UI.
  3. Read 03-implementation-plan.md — note the reference patterns flagged for this slice's frontend half. These are hints, not file lists.
  4. Read relevant docs/project_context/ files — load project-specific conventions (these override the React guidelines where they conflict).
  5. Grep for the closest existing component/page/hook matching the reference patterns.

Also invoke the reuse-ladder skill — its reuse ladder (reuse existing / native / installed before writing custom code) and lean mode (lean: lite|full, from the slice's story-point size) govern how much custom code you write. Pass the mode through to the frontend-implementer skill.

Read the full file on GitHub · 43 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 · 43 lines · 118 tokens per session scan A 60b178cf06a2

Subscribe to this mod's changes

impl-frontend is an agent published in the GitHub repository wei6bin/skills (2 stars, last pushed 9d ago), licensed MIT. It adds 118 tokens to every session and 839 once invoked, about $0.0006 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.

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