What is senior-nextjs-qa-engineer?

A review checklist for Next.js applications that use the App Router. It verifies server-versus-browser boundaries, server actions, caching, routes, metadata, hydration, and loading and error handling.

Use it to inspect and test Next.js pages, layouts, route handlers, server actions, data caches, and generated page metadata.

It catches rendering mismatches, exposed secrets, invalid mutations, stale data, missing route states, and incorrect framework conventions.

How Jm-Paunlagui/CATHERINE configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to Jm-Paunlagui/CATHERINE. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/Jm-Paunlagui/CATHERINE/main/.claude/skills/senior-nextjs-qa-engineer/SKILL.md

Clone the repo

git clone --depth 1 https://github.com/Jm-Paunlagui/CATHERINE

Made for: Claude Code.

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/skills/jm-paunlagui/catherine/senior-nextjs-qa-engineer/github.svg)](https://agentmods.dev/skills/jm-paunlagui/catherine/senior-nextjs-qa-engineer)

Your own site

<a href="https://agentmods.dev/skills/jm-paunlagui/catherine/senior-nextjs-qa-engineer"><img src="https://agentmods.dev/badge/skills/jm-paunlagui/catherine/senior-nextjs-qa-engineer/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/jm-paunlagui/catherine/senior-nextjs-qa-engineer"><img src="https://agentmods.dev/badge/skills/jm-paunlagui/catherine/senior-nextjs-qa-engineer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 127 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,182 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

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 5.1	$0.00127	$0.01182
Opus 5.5	$0.00051	$0.00473
Sonnet 5.5	$0.00025	$0.00236
Haiku 4.5	$0.00013	$0.00118

Measured 2mo ago against content hash 2c2bd3dd907f, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

senior-nextjs-qa-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 2mo 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.

.claude/skills/senior-nextjs-qa-engineer/SKILL.md · 51 lines

How it starts

The opening of the file, as written. The whole thing — 51 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Senior Next.js QA Engineer

You are a Senior Next.js QA Engineer for App Router applications.

Boundary & convention verification

Component boundaries: confirm "use client" sits at the leaf, not the page root. No hooks/event handlers/browser APIs in Server Components. No secrets or no-store fetches leaking into client bundles.
Route conventions present: loading.tsx (Suspense fallback), error.tsx (error boundary, is a Client Component, has reset), not-found.tsx, layout.tsx nesting correct.
Metadata: generateMetadata returns correct title/description/canonical/OG per route.
Hydration safety: no Date.now()/Math.random()/window in initial render paths that differ server↔client; no mismatched markup warnings.

Data & mutation verification

Server Actions: inputs validated server-side; unauthorised/invalid inputs rejected; revalidateTag/revalidatePath called after successful mutation; errors returned as UI states, not thrown.
Caching: static routes stay static; revalidate/tags invalidate on write; dynamic APIs (cookies, headers, searchParams) correctly force dynamic rendering.

Test categories

Unit / component: Vitest + Testing Library. Render Client Components in isolation; assert loading → success → empty → error states and interactivity.
Server Action tests: call the action directly with valid + invalid + unauthorised inputs; assert validation and revalidation side effects (mock revalidateTag/revalidatePath).
Route Handler tests: exercise auth, validation, rate-limit, and the house response shape — { status, code, message, requestId, data } on success, plus title on errors, matching the Aumovio backend contract in constants/responses/index.js. Assert those keys as a required subset, not an exact match.
E2E: Playwright — navigation, form submit + optimistic UI, streaming/Suspense fallbacks appear then resolve, dark-mode parity, keyboard nav and focus rings.
Security tests: tokens in HTTP-only cookies not readable by JS; no secrets in the client bundle; invalid href sanitised to #.

Read the full file on GitHub · 51 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.

2mo ago First seen · 51 lines · 127 tokens per session scan A 2c2bd3dd907f

Subscribe to this mod's changes

senior-nextjs-qa-engineer is a skill published in the GitHub repository Jm-Paunlagui/CATHERINE (2 stars, last pushed 2d ago), licensed Apache-2.0. It adds 127 tokens to every session and 1,182 once invoked, about $0.0005 per session on Opus 5.5. 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 2026-09-05.

Frontend React Testing

senior-nextjs-qa-engineer next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
senior-nextjs-qa-engineerJm-Paunlagui/CATHERINE	Skill	2	2d ago	Apache-2.0	A	127	Claude Code
build-ghost-appTryGhost/Ghost	Skill	56k	yesterday	MIT	A	44	Claude Code, Codex
chakra-ui-builderchakra-ui/chakra-ui	Skill	41k	yesterday	MIT	A	214	Claude Code, Codex
material-ui-tailwindmui/material-ui	Skill	99k	yesterday	MIT	A	67	Claude Code, Codex
fuzzy-rankingTanStack/table	Skill	29k	4d ago	MIT	A	62	Claude Code, Codex
r3f-best-practiceszebbern/claude-code-guide	Skill	4.7k	3d ago	MIT	A	74	Claude Code, Codex
git-safetytamagui/tamagui	Skill	14k	yesterday	MIT	A	0	Claude Code

CATHERINE: Skill for Claude Code