Expo

Create dev and preview builds for your Expo React Native app.

Set up with an agent

Paste one prompt and your coding agent does the rest.

Setup prompt

Set up Revyl for this Expo app.

Read https://docs.revyl.com/frameworks/expo.md and follow it. It's the current Revyl guide for this, so prefer it over anything you remember about Revyl.

`revyl init` writes the dev loop's `development` recipe with EAS, which needs my Expo login or `EXPO_TOKEN`, so ask me before using it. If this project doesn't already build with EAS, install `expo-dev-client` and change the `development` recipes to `expo prebuild` plus a Debug simulator build (`xcodebuild -configuration Debug -sdk iphonesimulator`) and `./gradlew assembleDebug`. If the app runs on both platforms, start with iOS.

You're done when the app runs in the Revyl dev loop on a cloud simulator or emulator, and a JavaScript change hot reloads.

Ask me before anything that needs my login or approval.

Build Guidance

To use the Dev Loop, a build is required only on native code changes (new native modules, Podfile/Gradle changes, build configuration). JS/TS changes hot reload via Metro — see Dev Loop: Hot reload and rebuild configuration for the full breakdown.

Build via Revyl CLI

Prerequisites

Node.js 18+
Expo CLI (npx expo)
EAS CLI (npx eas-cli) only when your authored recipe uses EAS
Revyl CLI installed and authenticated (revyl auth login)

Setup

Initialize the project using the Revyl CLI:

revyl init

This detects Expo and writes named profiles with the applicable iOS and Android recipes. Review or fill in the app IDs, commands, and output paths before the first build. See Types of Builds for more information.

Choose a build approach

Approach	Recipe	Expo authentication
Native prebuild (default in dashboard setup)	Run `expo prebuild`, then Xcode or Gradle directly	None required solely for Expo
EAS local build	Run `eas-cli build --local`	Use Expo login or `EXPO_TOKEN` locally; store encrypted `EXPO_TOKEN` for unattended remote builds

Choosing the Expo framework does not itself require EXPO_TOKEN. Add that secret only when the selected build command uses EAS or another project step needs it. The dashboard leaves commands and secret references directly editable; create any required secret inline or in the Library.

Development builds power the dev loop. Preview builds are for testing and starting sessions when the Metro server isn't needed.

Run Build

Run one profile/platform recipe in the cloud:

revyl build --profile development --platform ios

Profile names and their ios or android recipes live under build.profiles in .revyl/config.yaml. There is no active/default profile. See Configuration for selection and recipe fields.

This command automatically builds and uploads the app to Revyl, where you can use it to start sessions.

Advanced Configuration

When you run revyl init, Revyl makes a best-effort guess at your configuration. This section covers configuration in more detail.

EAS setup

This section applies only when an authored recipe uses EAS. Your eas.json needs at least two profiles: one that includes the development client and one that does not. See the following eas.json file as reference:

{
  "build": {
    "development": {
      "developmentClient": true,
      "distribution": "internal",
      "ios": {
        "simulator": true
      },
      "android": {
        "buildType": "apk"
      }
    },
    "preview": {
      "distribution": "internal",
      "ios": {
        "simulator": true
      },
      "android": {
        "buildType": "apk"
      }
    }
  }
}

Note that the iOS simulator is enabled for both profiles, and developmentClient is set to true only for the development profile. Revyl executes the command arrays in .revyl/config.yaml as authored; it does not rewrite eas.json or switch EAS profiles during a build.

Build Commands and Hot Reload Setup

revyl init creates a .revyl/config.yaml file in the root of your project. Each named profile contains the ordered setup/build commands and output path used by revyl build.

Configure these build settings using the Configuration page.

Expo dev-client hot reload needs a URL scheme baked into the native dev build. This is normally set as part of revyl init. The scheme is the custom URL prefix for your app, such as myapp-dev://. Revyl uses that scheme to open the Expo dev client on the cloud device and connect it to Metro.

If you use app.json, set expo.scheme before creating the dev build:

{
  "expo": {
    "scheme": "myapp-dev"
  }
}

Troubleshooting

Dev loop

Expo projects use full hot reload via a Revyl relay to your local Metro server. JS/TS changes appear on the device within seconds. Press [r] only when native dependencies change.

How detection works

The CLI looks for two things in the current directory:

"expo" in package.json dependencies or devDependencies
At least one project indicator: app.json, app.config.js, app.config.ts, eas.json, or .expo/ directory

If both are present, the Expo provider matches at confidence 0.9 — the highest of any provider. This means Expo wins over Swift (0.7) and Android (0.6) when all three detect the same directory.

If either condition fails (common in monorepos), the Expo provider returns nil and lower-confidence providers may match instead. See the monorepo section below.

URL schemes

Hot reload deep-links the dev client to your local Metro server via a custom URL scheme:

myapp://expo-development-client/?url=https://hr-abc123.revyl.ai

This requires a custom URL scheme (myapp://) registered in the dev client binary.

Where to find your scheme

Check app.json under expo.scheme:

{
  "expo": {
    "scheme": "myapp"
  }
}

Or in app.config.js / app.config.ts:

export default {
  expo: {
    scheme: "myapp",
  }
};

Keep this value in the Expo app configuration. It is baked into the development client and attached to the resulting build metadata; it is not an authored .revyl/config.yaml field.

Why universal links don't work

Apps that only use universal links (https://example.com/...) for deep linking cannot use those for hot reload. Apple's associated domains system requires a live HTTPS domain serving an apple-app-site-association file. Revyl hot reload uses short-lived relay hosts that are not suitable as stable associated domains. Custom URL schemes (myapp://) bypass this entirely — no server verification needed.

No URL scheme in the app

If your app has no expo.scheme (common in apps that only use universal links), you need to add one. The name is arbitrary and only affects the dev client:

{
  "expo": {
    "scheme": "myapp-dev"
  }
}

After adding the scheme, rebuild the dev client — the scheme is baked into the native binary and recorded with the build at build time. If initialization also generated the wrong framework or recipe, run revyl init --detect from the app directory, edit the generated profile as needed, and run revyl config validate.

Checking existing schemes without rebuilding

The dev client may already have a scheme registered by expo-dev-client. Check the iOS build:

grep -r "CFBundleURLSchemes" ios/ --include="*.plist" -A3

If this returns something like exp+myslug, that scheme is already baked into the client. Build it with revyl build so the artifact carries the same scheme metadata.

Generated scheme prefixes

Expo dev clients can register URL schemes in two formats:

Base scheme: myapp:// — registered when expo.scheme is set in app.json
Prefixed scheme: exp+myapp:// — auto-registered by expo-dev-client based on the app slug

Which form exists depends on the Expo SDK and the addGeneratedScheme setting at build time. If the selected build lacks scheme metadata or the registered scheme is wrong, configure expo.scheme (and addGeneratedScheme when applicable) in the Expo app and rebuild the development client.

Monorepo setup

In monorepos (Turborepo, Nx, pnpm workspaces), the Expo app typically lives in a subdirectory like apps/native/, apps/mobile/, or packages/app/.

Run from the Expo app directory

All Revyl commands must run from the directory containing the Expo app's package.json — not the monorepo root.

cd apps/native
revyl init --detect
revyl dev --platform ios

The CLI resolves the working directory by calling FindRepoRoot, which walks up from the current directory looking for .revyl/. If the monorepo root also has a .revyl/ directory (common for CI test configs), make sure you're in the correct subdirectory.

Why detection fails in monorepos

Two things go wrong:

Hoisted dependencies — Package managers like pnpm, Yarn, and npm may hoist expo to the root node_modules/ or use workspace:* protocol in the local package.json. The Expo provider reads the local package.json and checks for "expo" in dependencies or devDependencies. If it's not there, the provider returns nil (no match).
Native directories match other providers — Every Expo project with prebuild has ios/ containing .xcodeproj files (triggering the Swift provider at confidence 0.7) and android/ containing build.gradle (triggering the Android provider at confidence 0.6). When the Expo provider returns nil, these become the top matches.

The result: revyl init detects "Swift/iOS (coming soon)" and "Android (coming soon)" instead of Expo.

Fix: Rerun detection from the Expo app directory:

cd apps/native
revyl init --detect

If detection remains ambiguous, edit build.framework and the generated profile recipes in .revyl/config.yaml, then run revyl config validate. If expo is genuinely missing from the local package.json, add it:

npx expo install expo

The generated .revyl/config.yaml should have build.framework: expo and a named development profile with the applicable iOS and/or Android recipes. The custom URL scheme remains in the Expo app configuration, not the Revyl YAML.

What to expect when the deep link opens

After revyl dev starts, the CLI opens a deep link to connect the dev client to your local Metro server. You may notice:

A confirmation dialog -- iOS shows "Open in [Your App]?" with Cancel and Open buttons. This is a standard iOS security prompt for URL scheme handoffs. Tap Open to proceed. (On cloud simulators this currently requires a manual tap; future CLI versions will auto-accept it.)
The app briefly restarts -- The dev client may close and reopen as it disconnects from its cached state and reconnects to the tunnel URL. This looks jarring but is normal Expo dev client behavior. The app is reloading to fetch the JS bundle from your local Metro server instead of its built-in bundle.
Sometimes no restart at all -- If the dev client is already in a fresh state (first launch after install), it may connect seamlessly without closing. The behavior varies by Expo SDK version and whether the app was previously running.

Once the app is back up and showing your app's UI, hot reload is active. Edit a file locally, save, and the change appears on the device within seconds.

If the app closes and doesn't come back, check the Metro/Expo terminal output for JavaScript errors. A crash during bundle loading usually means a missing native module or environment variable issue -- not a Revyl problem.

Dynamic config (app.config.js / app.config.ts)

Dynamic Expo config must still resolve a custom scheme. Verify the evaluated configuration with Expo tooling. For managed builds, Revyl reads the registered scheme from the compiled app and attaches it as artifact metadata. If inspection is unavailable, the build and upload still succeed, but that artifact cannot start an Expo dev loop until compatible scheme metadata is available.

The scheme is the custom URL prefix baked into the Expo dev client, such as myapp-dev://. Revyl uses it to open the installed dev client on the cloud device and connect it to Metro for hot reload.

Configure the scheme in app.config.js or app.config.ts, then run detection from the app directory:

revyl init --detect

If the generated framework or recipe is still wrong, edit the named profile in .revyl/config.yaml and run revyl config validate.

If you add or change the scheme, rebuild the Expo dev client once. After that, JS/TS changes can hot reload through revyl dev without another build.

Custom dev server port

If Metro runs on a non-default port (common in monorepos with multiple Metro instances), pass it for the invocation:

revyl dev --platform ios --port 8082

Dev loop walkthrough

You need the prerequisites above and a dev client build of your Expo or React Native project.

Step 1: Configure hot reload

revyl init

Initialization detects the framework and writes named build profiles. In a monorepo, run revyl init --detect from the Expo app directory. If detection still needs correction, edit build.framework and the generated development profile, then run revyl config validate.

Configure the custom URL scheme in the Expo app before building the development client; the scheme is attached to the build artifact rather than authored in .revyl/config.yaml. See Configuration Files for the profile schema and Dev Loop Framework Guides for framework-specific setup.

Step 2: Upload a dev build

Upload a development client build. It lands on the Revyl branch named after your Git branch, which the first upload creates, or on the app's default branch outside a Git checkout:

revyl build --profile development --platform ios

For Expo, this is a dev client build. For bare React Native, it's your debug build.

revyl build runs in the cloud. The dev loop remains local unless you use revyl dev --remote.

revyl dev resolves one named profile/platform recipe, runs on the branch named after your Git branch, and installs that branch's default build. Pass --branch <name> to both build and dev to use another branch. For every branch and build rule, see Dev Loop.

Step 3: Start the dev loop

revyl dev --profile development --platform ios

You may omit the flags when the result is deterministic. revyl dev first prefers one unique development-like profile and then accepts only a sole eligible profile or platform. It prompts for remaining choices interactively and fails with the valid choices non-interactively. This is invocation-time selection, not an active/default profile.

This:

Starts your local dev server (Expo via npx expo start --dev-client, or Metro via npx react-native start)
Creates a Revyl relay to expose it to cloud devices
Installs the dev client build on a cloud device
Opens the device session in your browser

Normal runs keep advisory HMR diagnostics quiet so they do not look like startup failures. If you are troubleshooting relay or HMR internals, run with revyl dev --debug to print the diagnostic probes.

Now edit code locally and see changes reflected on the device instantly.

Platform and build overrides

revyl dev --profile development --platform android  # Explicit recipe
revyl dev --no-open                       # Don't open browser (headless/SSH)
revyl dev --profile development --platform ios --build  # Fresh local build
revyl dev --profile development --platform ios --remote # Remote build
revyl dev --build-version-id <id>         # Use one exact build
revyl dev --context ios-main              # Named context for parallel loops
revyl dev --force-hot-reload              # Diagnostic launch after Expo relay transport
revyl dev --no-build --tunnel "<expo-dev-client-link>"  # Reuse an Expo tunnel

The selected recipe remains fixed for the dev context. Forced builds, remote builds, and later revyl dev rebuild operations all use that same recipe.

If Revyl starts Expo and verifies relay transport but times out proving the first Expo manifest, retry with --force-hot-reload first. This launches after the relay and dev server start, skipping only the manifest and bundle proof. If the app loads, keep working; if the dev client shows a project load error, restart Expo/Metro or capture revyl device report --session-id <id> --json.

If you already run Expo with its own tunnel, you can collapse the manual device start + deep-link step into one command:

npx expo start --tunnel --dev-client
revyl dev --no-build --app-id <app-id> --tunnel "<deep-link-from-expo>"

--no-build reuses an existing build and keeps rebuilds off for this session. Add --branch <name> to require a specific branch's build.

--tunnel accepts either the full Expo dev-client link or the raw https://... tunnel URL. Passing the full dev-client link does not depend on an authored scheme field in the local Revyl config. Prefer the Revyl relay first in cloud-agent environments; use Expo tunnel fallback only after device screenshots or revyl device report --session-id <id> --json show force mode still did not load through the relay.

Step 4: Interact with the device

Use revyl device commands to observe, act, and verify in a tight loop.

# Observe
revyl device screenshot --out before.png

# Act
revyl device tap --target "Sign In button"
revyl device type --target "email field" --text "user@example.com"
revyl device type --target "password field" --text "secret123"
revyl device tap --target "Log In"

# Verify
revyl device screenshot --out after.png

Always follow the observe-act-verify pattern: screenshot before an action, take the action, then screenshot again to confirm the result.

Scroll through content with swipe:

revyl device swipe --target "product list" --direction down

Step 5: Verify flows live

While the dev loop is active, verify outcomes with device commands:

revyl device validation -s 0 "Home screen shows the signed-in user"

Step 6: Create tests from the session

After verifying a flow manually, convert the device session into a regression test:

revyl test create checkout-flow --from-session <session-id> --platform ios
revyl test open checkout-flow

Step 7: Promote to regression

Once the test is stable, push and run it:

revyl test push checkout-flow --force
revyl test run checkout-flow

Device-first flow

Start a plain device session first, then attach and run the dev loop on it:

revyl device start --platform ios
revyl dev attach active --context checkout
revyl dev --context checkout            # reuses the attached session

When the dev loop exits, the attached session stays running. Run revyl dev --context checkout again to resume, or revyl dev stop to detach.

Context management

revyl dev list                         # List dev contexts in the current worktree
revyl dev use ios-main                 # Switch the current context
revyl dev status                       # Show context status (JSON)
revyl dev rebuild                      # Trigger a rebuild
revyl dev stop                         # Stop the current context
revyl dev stop --all                   # Stop all contexts

All developers push builds to a shared app container (the app_id in config). Each developer gets their own cloud device session, relay URL, and local server. For JS projects, multiple developers can share the same dev build and still see their own code changes.

Build Guidance

Build via Revyl CLI

Prerequisites

Setup

Choose a build approach

Run Build

Advanced Configuration

EAS setup

Build Commands and Hot Reload Setup

Troubleshooting

Dev loop

How detection works

URL schemes

Where to find your scheme

Why universal links don't work

No URL scheme in the app

Checking existing schemes without rebuilding

Generated scheme prefixes

Monorepo setup

Run from the Expo app directory

Why detection fails in monorepos

What to expect when the deep link opens

Dynamic config (app.config.js / app.config.ts)

Custom dev server port

Dev loop walkthrough

Step 1: Configure hot reload

Step 2: Upload a dev build

Step 3: Start the dev loop

Platform and build overrides

Step 4: Interact with the device

Step 5: Verify flows live

Step 6: Create tests from the session

Step 7: Promote to regression

Device-first flow

Context management

Resources

On this page

Build GuidanceCopy Anchor Link

Build via Revyl CLICopy Anchor Link

PrerequisitesCopy Anchor Link

SetupCopy Anchor Link

Choose a build approachCopy Anchor Link

Run BuildCopy Anchor Link

Advanced ConfigurationCopy Anchor Link

EAS setupCopy Anchor Link

Build Commands and Hot Reload SetupCopy Anchor Link

TroubleshootingCopy Anchor Link

Build fails or times out

Download links expired

iOS or Android APK app won't install

Dev loopCopy Anchor Link

How detection worksCopy Anchor Link

URL schemesCopy Anchor Link

Where to find your schemeCopy Anchor Link

Why universal links don't workCopy Anchor Link

No URL scheme in the appCopy Anchor Link

Checking existing schemes without rebuildingCopy Anchor Link

Generated scheme prefixesCopy Anchor Link

Monorepo setupCopy Anchor Link

Run from the Expo app directoryCopy Anchor Link

Why detection fails in monoreposCopy Anchor Link

What to expect when the deep link opensCopy Anchor Link

Dynamic config (app.config.js / app.config.ts)Copy Anchor Link

Custom dev server portCopy Anchor Link

Dev loop walkthroughCopy Anchor Link

Step 1: Configure hot reloadCopy Anchor Link

Step 2: Upload a dev buildCopy Anchor Link

Step 3: Start the dev loopCopy Anchor Link

Platform and build overridesCopy Anchor Link

Step 4: Interact with the deviceCopy Anchor Link

Step 5: Verify flows liveCopy Anchor Link

Step 6: Create tests from the sessionCopy Anchor Link

Step 7: Promote to regressionCopy Anchor Link

Device-first flowCopy Anchor Link

Context managementCopy Anchor Link

Team sharingCopy Anchor Link

ResourcesCopy Anchor Link

On this page

Build Guidance

Build via Revyl CLI

Prerequisites

Setup

Choose a build approach

Run Build

Advanced Configuration

EAS setup

Build Commands and Hot Reload Setup

Troubleshooting

Dev loop

How detection works

URL schemes

Where to find your scheme

Why universal links don't work

No URL scheme in the app

Checking existing schemes without rebuilding

Generated scheme prefixes

Monorepo setup

Run from the Expo app directory

Why detection fails in monorepos

What to expect when the deep link opens

Dynamic config (app.config.js / app.config.ts)

Custom dev server port

Dev loop walkthrough

Step 1: Configure hot reload

Step 2: Upload a dev build

Step 3: Start the dev loop

Platform and build overrides

Step 4: Interact with the device

Step 5: Verify flows live

Step 6: Create tests from the session

Step 7: Promote to regression

Device-first flow

Context management

Team sharing

Resources