/react-native-brownfield-migration

name: react-native-brownfield-migration
description: Implements an accepted incremental brownfield migration from native iOS or Android to React Native or Expo using @callstack/react-native-brownfield. Use after the brownfield path has been selected, when setting up the integration, packaging XCFramework or AAR artifacts, or adding React Native surfaces to native hosts.
license: MIT

Migrating to React Native

Use this skill only after the decision to adopt brownfield migration has been made. When the user is still choosing between brownfield, greenfield, a checkpoint-based path, defer, or no migration, use [assess-react-native-migration](../assess-react-native-migration/SKILL.md) first.

Overview

Prescriptive workflow for incremental adoption of React Native in existing native apps using `@callstack/react-native-brownfield`, from initial setup through phased host integration.

• Expo track
• Bare React Native track

Use one track per task unless the user explicitly asks for migration or comparison.

Migration Strategy

Use this strategy for brownfield migration planning and execution:

1. Assess app state and select Expo or bare path. 2. Perform initial setup with `@callstack/react-native-brownfield`. 3. Package RN artifacts (`XCFramework`/`AAR`) from the RN source app. 4. Integrate one RN surface into the host app and validate startup/runtime. 5. Repeat integration by feature/screen for incremental rollout.

Agent Guardrails (Global)

Apply these rules across all reference files:

1. Select one path first (Expo or bare) and do not mix steps. 2. Use placeholders from the docs (`<framework_target_name>`, `<android_module_name>`, `<registered_module_name>`) and resolve from project files. 3. Validate each packaging command before moving to host integration. 4. Run `npx brownfield <command> --help` before relying on any flag table in these references; help output wins. 5. Write stable project settings once into `brownfield.config.*` instead of repeating flags — see [cli-and-config.md][cli-and-config]. 6. Prefer official docs for long platform snippets and CLI option details. 7. Keep host apps isolated from direct React Native APIs when possible (facade approach). 8. For startup/runtime verification, use `agent-device` to open the host app, navigate to the RN surface, capture snapshots/screenshots, and collect device evidence. If it is missing and verification needs it, install it through the environment's approved/trusted path or ask the user to install or enable it.

Canonical Docs

• [Quick Start](https://oss.callstack.com/react-native-brownfield/docs/getting-started/quick-start.md)
• [Expo Integration](https://oss.callstack.com/react-native-brownfield/docs/getting-started/expo.md)
• [iOS Integration](https://oss.callstack.com/react-native-brownfield/docs/getting-started/ios.md)
• [Android Integration](https://oss.callstack.com/react-native-brownfield/docs/getting-started/android.md)
• [Brownfield CLI](https://oss.callstack.com/react-native-brownfield/docs/cli/brownfield.md)
• [Configuration](https://oss.callstack.com/react-native-brownfield/docs/api-reference/configuration.md)
• [Guidelines](https://oss.callstack.com/react-native-brownfield/docs/guides/guidelines.md)
• [Troubleshooting](https://oss.callstack.com/react-native-brownfield/docs/guides/troubleshooting.md)

Path Selection Gate (Must Run First)

Before selecting any reference file, classify the project:

1. If no React Native app exists yet, use Expo creation path:

• [expo-create-app.md][expo-create-app] -> [expo-quick-start.md][expo-quick-start]

2. If React Native app exists, inspect `package.json` and `app.json`:

• Expo if `expo` is present or Expo plugin workflow is requested.
• Bare RN if native folders and direct RN CLI workflow are used without Expo path requirements.

3. If still unclear, ask one disambiguation question. 4. Continue with exactly one path.

When to Apply

Reference this package when:

• Implementing an accepted incremental migration from native-only apps to React Native or Expo
• Creating brownfield integration flows for Expo or bare React Native projects
• Performing initial setup with `@callstack/react-native-brownfield`
• Generating iOS XCFramework artifacts from a React Native app
• Generating and publishing Android AAR artifacts from a React Native app
• Integrating generated artifacts into host iOS/Android apps

Quick Reference

| File | Description | |------|-------------| | [quick-start.md][quick-start] | Shared preflight and mandatory path-selection gate | | [cli-and-config.md][cli-and-config] | CLI commands, full flag sets, config file, artifact layout, codegen side effects | | [runtime-api.md][runtime-api] | Host <-> RN API surface (JS, Swift, Kotlin) and reference apps | | [expo-create-app.md][expo-create-app] | Scaffold a new Expo app before Expo brownfield setup | | [expo-quick-start.md][expo-quick-start] | Expo plugin setup and packaging readiness | | [expo-ios-integration.md][expo-ios-integration] | Expo iOS packaging and host startup integration | | [expo-android-integration.md][expo-android-integration] | Expo Android packaging, publish, and host integration | | [bare-quick-start.md][bare-quick-start] | Bare React Native baseline setup | | [bare-ios-xcframework-generation.md][bare-ios-xcframework-generation] | Bare iOS XCFramework generation | | [bare-android-aar-generation.md][bare-android-aar-generation] | Bare Android AAR generation and publish | | [bare-ios-native-integration.md][bare-ios-native-integration] | Bare iOS host integration | | [bare-android-native-integration.md][bare-android-native-integration] | Bare Android host integration |

Problem -> Skill Mapping

| Problem | Start With | |---------|------------| | Need migration path decision first | [assess-react-native-migration](../assess-react-native-migration/SKILL.md) | | Need Expo vs bare path decision | [quick-start.md][quick-start] | | Need a CLI flag, the config file shape, o