What is react-native-brownfield-migration?

A guide for gradually adding React Native screens or features to an existing native iOS or Android app, known as a brownfield migration.

Use it to set up the integration, package React Native artifacts, connect them to native hosts, and add features one screen at a time.

It gives teams a staged path for adopting React Native without replacing the whole native application at once.

react-native-brownfield-migration — Skill for Claude Code and Codex by callstackincubator: A guide for gradually adding React Native screens

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods

npx agentmods add skills/callstackincubator/agent-skills/react-native-brownfield-migration

Any agent

npx skills add callstackincubator/agent-skills --skill react-native-brownfield-migration

Clone the repo

git clone --depth 1 https://github.com/callstackincubator/agent-skills

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/callstackincubator/agent-skills/react-native-brownfield-migration.svg)](https://agentmods.dev/skills/callstackincubator/agent-skills/react-native-brownfield-migration)

Your own site

<a href="https://agentmods.dev/skills/callstackincubator/agent-skills/react-native-brownfield-migration"><img src="https://agentmods.dev/badge/skills/callstackincubator/agent-skills/react-native-brownfield-migration.svg" alt="Measured on agentmods" height="20"></a>

Per session 70 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,577 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. Scan, not verified.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5	$0.00070	$0.01577
Opus 5	$0.00035	$0.00788
Sonnet 5	$0.00014	$0.00315
Haiku 4.5	$0.00007	$0.00158

Measured 4d ago against content hash a01b34e0e03a, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

react-native-brownfield-migration scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 4d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/react-native-brownfield-migration/SKILL.md · 119 lines

How it starts

The opening of the file, as written. The whole thing — 119 lines — stays where its author put it; the contents beside it link to each section on GitHub.

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 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:

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

Agent Guardrails (Global)

Apply these rules across all reference files:

Select one path first (Expo or bare) and do not mix steps.
Use placeholders from the docs (<framework_target_name>, <android_module_name>, <registered_module_name>) and resolve from project files.
Validate each packaging command before moving to host integration.
Prefer official docs for long platform snippets and CLI option details.
Keep host apps isolated from direct React Native APIs when possible (facade approach).
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

Read the full file on GitHub · 119 lines

Files

What ships with it

11 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

4d ago First seen · 119 lines · 70 tokens per session scan A a01b34e0e03a

Subscribe to this mod's changes

react-native-brownfield-migration is a skill published in the GitHub repository callstackincubator/agent-skills (1,634 stars, last pushed 27d ago), licensed MIT. It adds 70 tokens to every session and 1,577 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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