Native Companion Expo Boundary

Decision Record

Status: Proposed / future.

Decision: Use Expo for a native companion app only when mobile-native capabilities are validated by Mobile Launchpad PWA usage and Studio View JSON renderer maturity.

This is not an implementation approval. Do not initialize Expo, React Native, or a native app project from this document.

Why Expo Fits A Future Companion

Expo can be a practical future path for a solo builder or small team because it offers:

fast iteration across iOS and Android;
managed native capabilities before deeper native code is justified;
OTA-oriented iteration for app-shell code within platform policy limits;
mature patterns for camera, media, push, sharing, files, deep links, and permissions;
a smoother path from prototype to store builds than a fully custom native setup.

Native Capabilities That May Justify Expo

Capability	Device Studio use case
Camera	Capture receipts, whiteboards, product states, places, or visual notes.
Photo library	Attach images to Studios, Sources, or AI context with explicit consent.
Push notifications	Approval requests, AI run completion, connector alerts, and digest prompts.
Share extension	Save links, text, images, files, and screenshots into a Studio.
Files	Upload or preview user-selected documents with clear retention boundaries.
Contacts	Optional relationship context only after strict permission and privacy review.
Background upload	Large media capture flows after user intent is clear.
Deep links	Open Studio, View, approval, capture, or AI routes from notifications and links.
Biometric auth	Confirm high-impact approvals or sensitive local access.

Boundary

The native app should be a companion shell around Device Studio capabilities. It should not become the full Prox OS runtime.

Appropriate native responsibilities:

host Mobile Launchpad;
render Studio View JSON with trusted blocks;
provide native capture and share affordances;
receive notifications and deep links;
mediate permissions and high-impact actions;
hand off complex editing to Web Studio.

Inappropriate native responsibilities:

execute arbitrary remote JavaScript or React bundles;
host a general third-party app runtime;
expose native APIs directly to user-generated experiences;
replace the Web Studio editing surface;
launch an unreviewed app marketplace;
bypass app-store payment or content policies;
ship before privacy policy, permission copy, and store review posture exist.

Launch Triggers

Start an Expo exploration only when all of these are true:

Mobile Launchpad PWA has validated high-frequency use.
Capture, notifications, or share extension are clear product needs.
Permission descriptions and privacy policy are ready for mobile review.
A store review plan exists for dynamic views, UGC, payments, and native API boundaries.
Studio View JSON renderer is stable enough to share with native.
High-impact mobile actions have audit, confirmation, and rollback posture.

Consequences

Positive consequences:

Prox OS can add mobile-native capture and notification loops without moving the whole platform away from Web Studio.
The same Studio View JSON contract can serve PWA and native companion surfaces.
Native work stays tied to validated needs.

Trade-offs:

Native release cycles and store review create operational overhead.
Permission, privacy, and content policy obligations become more visible.
The team must maintain a mobile renderer in addition to the web renderer.
Dynamic view governance must be stricter on native than on desktop web.

Non-goals

No Expo project now.
No React Native app now.
No native marketplace now.
No native mini app runtime now.
No payment, billing, or store-submission implementation from this document.