React Router Loader Boundary Review

React Router Loader Boundary Review is a skill for Claude Code from s977043/river-review. It costs 39 tokens per session (982 once invoked), scanned A, original, MIT.

A review rule for React Router framework-mode route data loading. It checks whether navigation data belongs in a loader and whether server-only and browser-only code stay on the correct side.

In plain words
What is it for?
It reviews route loaders and clientLoaders, checking initial navigation data, server/client API boundaries, and missing HydrateFallback handling.
Why use it?
It prevents route data from being fetched late in useEffect, which can cause duplicate requests, race conditions, or hydration mismatches. Hydration is the browser attaching behavior to server-rendered HTML.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the river-review plugin — 139 skills, 18 commands, 5 agents, 3 hooks shipped together

Good fit It reviews route loaders and clientLoaders, checking initial navigation data, server/client API boundaries, and missing HydrateFallback handling.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/s977043/river-review/react-router-loader-boundary
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.

Any agent
npx skills add s977043/river-review --skill react-router-loader-boundary
Clone the repo
git clone --depth 1 https://github.com/s977043/river-review

Made for: Claude Code.

Or install river-review, the plugin that ships this one along with the rest of its 139 skills, 18 commands, 5 agents, 3 hooks.

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 React Router Loader Boundary Review

README.md
[![agentmods](https://agentmods.dev/badge/skills/s977043/river-review/react-router-loader-boundary/github.svg)](https://agentmods.dev/skills/s977043/river-review/react-router-loader-boundary)
Your own site
<a href="https://agentmods.dev/skills/s977043/river-review/react-router-loader-boundary"><img src="https://agentmods.dev/badge/skills/s977043/river-review/react-router-loader-boundary/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.

agentmods 80×15 button for React Router Loader Boundary Review

Your own site · 80×15
<a href="https://agentmods.dev/skills/s977043/river-review/react-router-loader-boundary"><img src="https://agentmods.dev/badge/skills/s977043/river-review/react-router-loader-boundary.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 39 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 982 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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00039 $0.00982
Opus 5.5 $0.00016 $0.00393
Sonnet 5.5 $0.00008 $0.00196
Haiku 4.5 $0.00004 $0.00098

Measured 1mo ago against content hash cefcbbfbd4e6, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

React Router Loader Boundary Review 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 1mo 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.

plugin-dist/river-review/skills/midstream/react-router-loader-boundary/SKILL.md · 73 lines

What it actually says

Pattern declaration

Primary pattern: Reviewer Secondary patterns: Inversion Why: React Router framework mode の data loading 規約への適合をチェックリスト型で検査する

Goal / 目的

  • ルート遷移で確定するデータが useEffect + fetch でコンポーネント取得されること(二重フェッチ・レース・hydration mismatch の温床)を防ぐ。
  • loader / clientLoader の境界違反(loader 内のクライアント専用 API、clientLoader 内のサーバー専用 API)を検出する。

Non-goals / 扱わないこと

  • action / mutation の規約(react-router-action-contract のスコープ)。
  • data mode / declarative mode のコード(framework mode のルートモジュールのみ対象)。
  • 一般的な React パフォーマンス(modern-web 系 skill のスコープ)。

Pre-execution Gate / 実行前ゲート

このスキルは以下の条件がすべて満たされない限りNO_REVIEWを返す。

  • 差分が React Router framework mode のルートモジュール(loader / clientLoader / action の export、または routes 配下)に関係する
  • diff コンテキストが利用可能である

ゲート不成立時の出力: NO_REVIEW: react-router-loader-boundary — framework mode ルートの変更なし

False-positive guards / 抑制条件

  • useEffect + fetch が ナビゲーションに紐づかない データの場合は指摘しない(ポーリング、WebSocket、リアルタイム更新、サードパーティ SDK 初期化)。「URL / ルート遷移で確定するデータか」で判定する。
  • 親ルートの loader で取得済みデータを子が利用する設計は正当。
  • data mode / declarative mode のコードには適用しない(モード誤判定が最大の誤検出源)。

Rule / ルール

  • ルート遷移で確定する初期データは loader(SSR、サーバー専用 API はクライアントバンドルから自動除去される)に置く。
  • ブラウザ専用データは clientLoader に置き、hydrate する場合は HydrateFallback を定義する(clientLoader.hydrate = true as const の as const 欠落も指摘)。
  • loader 内でクライアント専用 API(window / localStorage 等)、clientLoader 内でサーバー専用 API(DB 直接アクセス等)を使っていないか確認する。
  • loader の返却値はシリアライズ可能型に限る(class instance の返却を指摘)。

Evidence / 根拠の取り方

  • 指摘は <file>:<line> で差分に紐づけ、該当する公式規約(reactrouter.com/start/framework/data-loading)を 1 行で添える。
  • ナビゲーション紐づきの判断が割れる場合は断定せず questions で返す。

Output / 出力(短文版の推奨)

コメントは日本語で返す。

  • Finding: どの境界規約に反しているか(1文)
  • Impact: 二重フェッチ / hydration mismatch / バンドル漏えい等の影響
  • Fix: loader / clientLoader への移動案(最小)

Sources / 出典

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 1mo ago First seen · 73 lines · 39 tokens per session scan A cefcbbfbd4e6

Subscribe to this mod's changes

React Router Loader Boundary Review is a skill published in the GitHub repository s977043/river-review (7 stars, last pushed yesterday), licensed MIT. It adds 39 tokens to every session and 982 once invoked, about $0.0002 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 2026-09-03.

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