Imported from tuncoglu/SourDough (SourDoughMobile/AGENTS.md). Install upstream with npx skills add tuncoglu/SourDough --skill SourDoughMobile. Copyright stays with the author.

Just Dough It — Architecture

Routes (app/)

• Landing (index.tsx, "/") — Three-card picker: bread, yogurt, or lacto-fermentation. Footer links to saved recipes, about, and settings.

Tabs (app/(tabs)/)

• Sourdough (bread.tsx, "/bread") — Bread recipe calculator with flour blends, pre-ferments, cold proof, ready-by planner. NOTE: the tab screen is deliberately named "bread" — a group index at (tabs)/index.tsx would collide with the landing route "/".
• Yogurt (yogurt.tsx) — Yogurt incubation calculator with 10 culture types, milk picker, yield & nutrition
• Lacto-ferment (ferments.tsx) — Vegetable fermentation with salt calculator, 25+ vegetables, day-by-day timeline
• History (history.tsx) — Saved recipes with search, filter chips, edit, duplicate, delete
• Settings (settings.tsx) — Default values, water hardness override, theme (light/dark/system), units (metric/imperial)
• About (about.tsx) — App overview, privacy notice, and acknowledgements

Calculation Engines (src/lib/)

• calculations.ts — Bread FDT (mass-weighted specific heat), ingredient weights, Q10 fermentation model, cold proof
• yogurtCalculations.ts — Yogurt incubation (Q10), yield (evaporation + straining), nutrition, timeline
• lactoCalculations.ts — Lacto-fermentation salt (dry/brine/mash methods), Q10 duration, pH timeline, safety
• blendUtils.ts — Flour blend protein (weighted avg), ferment factors by category, validation
• unitConversion.ts — Metric/imperial display conversion (g↔oz, °C↔°F). Engine always uses metric internally.

State Management

• Hooks (src/hooks/) — UI state and orchestration (useCalculatorInputs, useStarterTracker, useYogurtCalculator, etc.)
• useLocation — shared context provider mounted in app/_layout.tsx; runs location detection once for all three calculator tabs (GPS, weather, water hardness, postcode refinement)
• Stores (src/store/) — AsyncStorage persistence (recipeStore, settingsStore, starterStore)
• settingsCache.ts — In-memory cache for settings with 60s TTL to avoid re-reading AsyncStorage

Theme (src/theme/)

• LightColors / DarkColors palettes with warm bakery aesthetic
• useAppTheme() hook provides colors, themeMode (system/light/dark), unitSystem (metric/imperial)
• Spacing, FontSize, BorderRadius design tokens

Key Patterns

• Expo SDK 56, React Native 0.85, TypeScript
• File-based routing via expo-router
• Pure calculation functions (no React dependency) — testable without RN runtime
• Unit conversion at display boundary only — all internal math is metric (g, °C)