What is building-native-ui?

A development guide for building mobile app interfaces with Expo Router, a framework for organising screens and navigation in Expo apps.

It helps build screens, navigation, native tabs, forms, animations, search, media features, storage, icons, gradients, and visual effects.

It gives developers patterns for common interface work instead of requiring them to design navigation, styling, controls, and device features from scratch.

building-native-ui — Skill for Claude Code and Codex by happycapy-ai

Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo

git clone --depth 1 https://github.com/happycapy-ai/Happycapy-skills

agentmods

npx agentmods add skills/happycapy-ai/happycapy-skills/building-native-ui

Made for: Claude Code, Codex.

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/happycapy-ai/happycapy-skills/building-native-ui/github.svg)](https://agentmods.dev/skills/happycapy-ai/happycapy-skills/building-native-ui)

Your own site

<a href="https://agentmods.dev/skills/happycapy-ai/happycapy-skills/building-native-ui"><img src="https://agentmods.dev/badge/skills/happycapy-ai/happycapy-skills/building-native-ui/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/happycapy-ai/happycapy-skills/building-native-ui"><img src="https://agentmods.dev/badge/skills/happycapy-ai/happycapy-skills/building-native-ui.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 31 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,452 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 95% copy Near-identical to another mod 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	$0.00031	$0.02452
Opus 5	$0.00015	$0.01226
Sonnet 5	$0.00006	$0.00490
Haiku 4.5	$0.00003	$0.00245

Measured 12d ago against content hash e6b278b3a889, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

building-native-ui 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 12d 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.

Origin

This is a copy

95% identical to building-native-ui — 3 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/building-native-ui/SKILL.md · 321 lines

How it starts

The opening of the file, as written. The whole thing — 321 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Expo UI Guidelines

References

Consult these resources as needed:

references/
  animations.md          Reanimated: entering, exiting, layout, scroll-driven, gestures
  controls.md            Native iOS: Switch, Slider, SegmentedControl, DateTimePicker, Picker
  form-sheet.md          Form sheets with footers via Stack and react-native-screens
  gradients.md           CSS gradients via experimental_backgroundImage (New Arch only)
  icons.md               SF Symbols via expo-image (sf: source), names, animations, weights
  media.md               Camera, audio, video, and file saving
  route-structure.md     Route conventions, dynamic routes, groups, folder organization
  search.md              Search bar with headers, useSearch hook, filtering patterns
  storage.md             SQLite, AsyncStorage, SecureStore
  tabs.md                NativeTabs, migration from JS tabs, iOS 26 features
  toolbar-and-headers.md Stack headers and toolbar buttons, menus, search (iOS only)
  visual-effects.md      Blur (expo-blur) and liquid glass (expo-glass-effect)
  webgpu-three.md        3D graphics, games, GPU visualizations with WebGPU and Three.js
  zoom-transitions.md    Apple Zoom: fluid zoom transitions with Link.AppleZoom (iOS 18+)

Running the App

CRITICAL: Always try Expo Go first before creating custom builds.

Most Expo apps work in Expo Go without any custom native code. Before running npx expo run:ios or npx expo run:android:

Start with Expo Go: Run npx expo start and scan the QR code with Expo Go
Check if features work: Test your app thoroughly in Expo Go
Only create custom builds when required - see below

When Custom Builds Are Required

You need npx expo run:ios/android or eas build ONLY when using:

Local Expo modules (custom native code in modules/)
Apple targets (widgets, app clips, extensions via @bacons/apple-targets)
Third-party native modules not included in Expo Go
Custom native configuration that can't be expressed in app.json

Read the full file on GitHub · 321 lines

Files

What ships with it

14 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.

12d ago First seen · 321 lines · 31 tokens per session scan A e6b278b3a889

Subscribe to this mod's changes

building-native-ui is a skill published in the GitHub repository happycapy-ai/Happycapy-skills (139 stars, last pushed 8d ago), licensed MIT. It adds 31 tokens to every session and 2,452 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 95% identical to building-native-ui, differing in 3 lines, and is treated as a copy.

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