App icon generation

Platform requirements (non-negotiable)

Generation — mark, then pack

Never generate per-platform. Always: one 1024² RGBA master → deterministic fan-out.

1. Route the mark generation (see skills/logo/SKILL.md) — no text; subject-only.
2. Matte with BiRefNet if the chosen provider returned opaque.
3. Deterministic export via pipeline/export.ts::exportAppIconBundle (pure sharp — no external CLI dependency):
   • iOS: AppIcon.appiconset/Contents.json + every required PNG (iPhone/iPad/Mac/Watch/marketing). 1024 marketing variant flattened onto brand primary color (App Store rejects alpha). iOS 18 dark/tinted appearances emitted when ios_18_appearances: true.
   • Android: mipmap-{mdpi,hdpi,xhdpi,xxhdpi,xxxhdpi}/ic_launcher.png + mipmap-anydpi-v26/ic_launcher.xml pointing to ic_launcher_foreground + ic_launcher_background + ic_launcher_monochrome (foreground-derived via greyscale+threshold; the final themed-icon result should still be audited manually for complex marks).
   • PWA: 192.png, 512.png, 512-maskable.png (80% safe-zone padding) + manifest-snippet.json.
   • visionOS: 1024² master.png + a README describing the 3-layer parallax split that Xcode's Reality Composer Pro or a manual Photoshop step produces.
   • Favicon bonus: .ico (16/32/48 multi-res) via optional png-to-ico; falls back to separate PNGs with a warning if the dep is absent.

Prompt scaffold

A [flat vector | isometric 3D | glyph | soft gradient] app icon representing [SUBJECT, concrete noun phrase].
Bold, memorable silhouette. High contrast.
Subject fills 70-80% of frame, centered.
No text, no labels, no wordmark.
Palette: [#primary, #secondary, #accent].
Solid pure white background.
1:1 square, 1024x1024.

For platform styling: iOS-style rounded square backdrop or Android-style adaptive foreground on transparent can be added to steer, but the mark should be subject-only — backdrop is applied deterministically in export.

Android 13 monochrome derivation

Heuristic (see Open Question G11 in SYNTHESIS.md): sharp(foreground).greyscale().threshold(128).tint('#000'). Works for bold single-subject marks; audit visually for complex marks.

Validation

• 1024 marketing variant: opaque, dimensions exact, file <1MB.
• Android foreground: tight-bbox inside 72dp of 108dp.
• PWA maskable: subject inside 80% center circle.
• Contrast at 16×16 (renders to "favicon-ish" size): WCAG AA vs both white and dark card.
• No text detected by OCR (app icons must be text-free).

Output

app-icon/
├── master.png                      # 1024² RGBA
├── ios/AppIcon.appiconset/         # Contents.json + all sizes
├── ios/AppIcon-1024-opaque.png     # App Store marketing
├── android/mipmap-*/ic_launcher.png
├── android/mipmap-anydpi-v26/ic_launcher.xml
├── android/drawable/ic_launcher_{foreground,background,monochrome}.png
├── pwa/{192,512,512-maskable}.png
├── pwa/manifest-snippet.json
├── visionos/{front,middle,back}.png   # if parallax
└── meta.json