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rn-fundamentals

rn-fundamentals is a skill for Claude Code from lukedj78/dev-flow. It costs 137 tokens per session (1,445 once invoked), scanned A, original, MIT.

A set of starting rules for building React Native apps with Expo, a toolchain for making mobile apps with JavaScript or TypeScript. It sets the expected project structure, language, package manager, and Expo workflow.

In plain words
What is it for?
Use it when starting an Expo or React Native project, choosing between managed and bare workflows, or deciding on the app's architecture and core tools.
Why use it?
It prevents foundational choices from changing between projects or being made inconsistently. It also explains when Expo's managed workflow is unsuitable.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: reads .claude/ paths; mentions CLAUDE.md; mentions Claude Code.

Part of the dev-flow plugin — 46 skills shipped together

not rated 6 +1 yesterday A scan 137 tokens original MIT
View the source file lukedj78/dev-flow
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 skills/lukedj78/dev-flow/rn-fundamentals
Any agent
npx skills add lukedj78/dev-flow --skill rn-fundamentals
Clone the repo
git clone --depth 1 https://github.com/lukedj78/dev-flow

Made for: Claude Code.

Or install dev-flow, the plugin that ships this one along with the rest of its 46 skills.

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 rn-fundamentals

README.md
[![agentmods](https://agentmods.dev/badge/skills/lukedj78/dev-flow/rn-fundamentals.svg)](https://agentmods.dev/skills/lukedj78/dev-flow/rn-fundamentals)
Your own site
<a href="https://agentmods.dev/skills/lukedj78/dev-flow/rn-fundamentals"><img src="https://agentmods.dev/badge/skills/lukedj78/dev-flow/rn-fundamentals.svg" alt="Measured on agentmods" height="20"></a>
Per session 137 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,445 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 5.1 $0.00137 $0.01445
Opus 5 $0.00068 $0.00723
Sonnet 5 $0.00027 $0.00289
Haiku 4.5 $0.00014 $0.00145

Measured 6d ago against content hash ce61050ac196, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

rn-fundamentals 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 6d 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.

rn-fundamentals/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.

rn-fundamentals — foundational rules for React Native + Expo

This skill is the prerequisite read for any RN/Expo work. It sets the four non-negotiables and points you to deeper concept material when needed.

The 4 non-negotiables

  1. Expo managed workflow is the default. Bare workflow / react-native init only if there is a documented native dependency Expo cannot wrap.
  2. Latest stable Expo SDK — 57.0.16 on 2026-08-26 (npm view expo dist-tags); [VERIFY] at bootstrap time, quarterly cadence. New Architecture is on and not optional from SDK 55 onward — do not set newArchEnabled: it is ignored, and confirmed absent from @expo/[email protected]'s ExpoConfig schema (zero occurrences), so it is not merely discouraged — there is no key to set. Hermes is the engine.
  3. TypeScript is mandatory. tsconfig.json extends expo/tsconfig.base — confirmed shipping at the root of [email protected], and it sets moduleResolution: "bundler" (which is why relative imports here need no .js extension). ⚠️ blank-typescript is our choice, not the CLI's default. From [email protected]'s own help: "NPM template to use: default, blank, blank-typescript, tabs, bare-minimum. Default: default" — and default is the one it labels "recommended for most app developers". Pass -t blank-typescript explicitly or you get something else.
  4. npm is the package manager. ⚠️ This is a house rule, not the CLI's preference: [email protected] resolves the package manager from your environment — the --use-npm / --use-yarn / --use-pnpm flags are gone (zero occurrences in the package). Invoking it with npx gets you npm because npx is npm, not because the CLI prefers it. No Yarn, no pnpm in this set.
  5. ⚠️ create-expo-app@4 writes agent files by default — AGENTS.md, CLAUDE.md and .claude/settings.json, opt out with --no-agents-md. On a dev-flow project decide deliberately: a scaffolded CLAUDE.md sitting next to .workflow/ is a second set of instructions nobody reconciled.

Read the full file on GitHub · 51 lines

Files

What ships with it

6 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. 6d ago First seen · 51 lines · 137 tokens per session scan A ce61050ac196

Subscribe to this mod's changes

rn-fundamentals is a skill published in the GitHub repository lukedj78/dev-flow (6 stars, last pushed yesterday), licensed MIT. It adds 137 tokens to every session and 1,445 once invoked, about $0.0007 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.

Code GenerationFrontendMobileReactagent-skillsagentic-workflowai-agentsclaude-codeexpo
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