App Spec

App Spec

Produce the two documents that govern your entire build. This still happens in Claude chat.

When to Use

• You've completed the app-vision skill
• You're ready to create the project repo
• You need a CLAUDE.md and app spec before touching Claude Code

Document 1: CLAUDE.md

This file lives in the root of your repo. Claude Code reads it automatically at the start of every session. It contains rules, not descriptions.

Required Sections

# [App Name] - Development Rules

## Core Principles
- Use native SwiftUI components exclusively unless explicitly told to build custom
- Target iOS [version]
- Follow Apple HIG for all spacing, typography, layout, and interaction patterns
- Use SF Symbols for all icons unless a custom asset is specified
- Use system fonts unless a specific typeface is called out

## Navigation
- [Tab-based / Single stack / Other] navigation pattern
- List every navigation path: what presents what, and how (push, sheet, menu)
- Define presentation rules:
  - Sheets for: [creation, editing, multi-step flows]
  - Menus for: [action lists, quick selections]
  - Pickers for: [constrained value selection]
  - Context menus for: [long-press actions on list items]

## Architecture
- SwiftUI + [SwiftData / Core Data / UserDefaults] for persistence
- [MVVM / other] pattern
- File structure conventions:
  - /Components for shared components
  - /Models for data models
  - /Views/[Feature] for feature-specific views

## Color and Theming
- Primary tint: [hex or semantic description]
- Support light and dark mode from day one
- Use semantic colors (Color.primary, Color.secondary) for text
- [Liquid Glass / Material / other] treatment for system chrome

## Custom Components (the exceptions)
- List ONLY the components that cannot be built with native SwiftUI
- Each one gets a name and a one-line description of what it does
- These will be specced in detail during the build phase

## What NOT to Do
- Do not wrap native components in custom abstractions
- Do not use UIKit unless SwiftUI has no equivalent
- Do not create custom navigation transitions unless specified
- Do not add animations beyond SwiftUI defaults unless specified
- Do not hardcode strings

Writing Rules for CLAUDE.md

Be prescriptive, not descriptive. "Use .sheet with .presentationDetents" not "consider using sheets."

Be specific about navigation. Every screen-to-screen transition should be defined. "Plus button in toolbar opens New Project sheet" not "user can create projects."

List custom components explicitly. If it's not on the list, Claude Code should use native SwiftUI. This is the single most important rule for quality.

Include a What NOT to Do section. This prevents the most common Claude Code mistakes. Add to it as you discover patterns.

Document 2: App Spec

A screen-by-screen map. One to three sentences per screen. Not a PRD. Not a 40-page document.

Format

# [App Name] App Spec

## [Screen Name]
- What the user sees (layout, content, key UI elements)
- What the user can do (interactions, gestures, buttons)
- Where it leads (navigation: what opens when you tap what)
- Edge cases (empty state, loading state, error state)

## [Next Screen]
...

Per-Screen Checklist

Each screen entry should answer:

• [ ] What content is displayed?
• [ ] What are the primary actions?
• [ ] What secondary actions exist (context menu, toolbar menu)?
• [ ] What happens when the list is empty?
• [ ] What navigation paths lead TO this screen?
• [ ] What navigation paths lead FROM this screen?

Example Entry

## Projects Home (Tab 1)
- Scrollable list of active projects in a LazyVStack. Each row: project
  name (headline weight), circular progress ring (24pt), yarn color swatch.
- Long press on a row: context menu with Edit, Duplicate, Archive, Delete.
- Toolbar: plus button (top right) opens New Project sheet.
- Empty state: centered illustration + "Start your first project" CTA button.
- Tapping a row pushes to Project Detail.

Verification

Your spec is ready when:

• [ ] Every screen from the vision is represented
• [ ] Every navigation path is defined (you can trace a path from any screen to any other screen)
• [ ] Empty states are called out for every screen that displays a list
• [ ] Custom components are listed in CLAUDE.md (and there are as few as possible)
• [ ] The CLAUDE.md could be handed to a stranger and they'd know the rules

Output

Two files ready to drop into your repo:

1. CLAUDE.md (in project root)
2. APP_SPEC.md (in project root)

Next Step

Create your Xcode project, drop both files in, commit, and move to the scaffolding skill.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: troyjthomas
• Source: troyjthomas/ios-agent-skills
• License: MIT

Install and usage instructions live in the source repository linked above.