Expo App Development

Use this capability whenever you work on the framework layer of an Expo app — the part that decides where files live, how a URL becomes a screen, what the native binary contains, what happens between launch and first paint, and how the app reaches a device. It owns the app; it does not own the components inside it.

It does not own what a component is. Composition, props contracts, extracted hooks, state placement, memoization, loading and error surfaces, list virtualization, and test-hook naming belong to a React component development capability. It does not own how a surface looks: design tokens, colour, typography, spacing, themes, and stylesheet structure belong to a React component styling capability. Log levels, error-handling structure, and capture semantics belong to a software instrumentation capability — this skill covers only the Expo wiring of an error tracker. End-to-end test authoring belongs to an end-to-end testing capability — this skill covers only the Expo prerequisites for a run. Where a rule here has a counterpart in one of those, this skill states the Expo-layer mechanic and names the owner rather than restating its reasoning.

Version discipline. Expo breaks between SDK releases, and an API surface frozen into a rule rots within one of them. Every version-sensitive statement in this skill names the SDK it was verified against, and where a surface is known to move, the rule is a lookup — consult the installed SDK's versioned documentation — rather than a fixed import path or component name. Treat an unversioned claim about Expo, in this skill or anywhere else, as suspect.

Scope of the routing sections. Expo also ships surfaces this skill deliberately excludes, because no rule here was derived for them: API routes (+api.ts), server output and web deployment, native module authoring, brownfield integration, DOM components, and App Clips. Where a task reaches one of those, say so rather than extrapolating from the rules below.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

Project Layout

See project-layout.md for: