Limrun Xcode

Remote Xcode build

Build Apple projects on Limrun's remote Xcode, from any environment (Linux, Windows, macOS, VM, container). lim xcode build syncs your sources to a remote Xcode instance, builds there, and (when a simulator is attached) installs and relaunches the app. Never fall back to local Xcode, local simulators, or local build tools. Your job doesn't end at a green build: get the app running, verify it works, and iterate until the user is satisfied.

For driving the app once it's running (tap, type, element tree, screenshot, record), use the limrun-ios-simulator skill. For Bazel workspaces, use limrun-xcode-bazel instead of this skill.

Auth and CLI

Install if needed: npm install --global lim. Auth is lim login or LIM_API_KEY (it may be set outside the project, so don't ask for it just because it's missing from .env or the shell). The CLI is the source of truth: the commands in this skill are verified, but if a flag errors or you need one not shown here, check --help instead of guessing:

lim xcode --help
lim xcode build --help

Build

Instead of xcodebuild, build with:

lim xcode build .

This creates or reuses the remembered Xcode target, syncs the current directory, and streams the build logs through stdout and stderr.

Use --scheme and --workspace if the project has multiple schemes or uses a workspace file:

lim xcode build . --scheme MyApp --workspace MyApp.xcworkspace

Use --configuration Debug or --configuration Release for a specific Xcode configuration. If omitted, Limrun uses limbuild's project-type default: Debug for native Xcode builds, Release for React Native / Expo builds.

lim xcode build . --configuration Debug

Pick the Xcode version

A sandbox builds with its node's default Xcode. To build with another installed major (Xcode 27 beta is available beside the default), set a preference once for the workspace; every later build, test, RBE session and new sandbox follows it, and the flag overrides it for one command:

lim xcode version list      # versions the sandbox can build with; * marks the one in use
lim xcode version set 27    # prefer 27 for this workspace; switches the remembered sandbox now
lim xcode build .           # builds with 27
lim xcode version           # "27.0 (27A5252f)" shows the sandbox's current Xcode
lim xcode build . --xcode-version 26   # one-off override, not remembered
lim xcode version unset     # forget the preference; the sandbox goes back to the node default

For scripting, lim xcode version list --quiet prints one selectable major per line and --json returns { installed, bound, preferred } (installed[].betaSeed carries the beta seed). The table marks the Xcode in use with *. lim xcode version set does not record a major the node lacks (the error lists the available ones) but keeps it when the sandbox is merely busy.

When the sandbox is on another major than the workspace prefers, the next build says so and switches it first. Switching invalidates the build cache made with the other version (the next build starts cold) and is refused while a build, sync or lim xcode rbe stack is running. A major the node does not have fails with the available list; only majors are selectable. App Store uploads from a beta Xcode are rejected by Apple, so keep --upload-to-appstore on the default.

--dev-server-url is only supported with --configuration Debug for React Native / Expo builds. It's a post-install launch URL: limbuild validates it is a parseable absolute URL, then opens it unchanged after installing on the attached simulator. Framework-specific skills construct the correct URL.

lim xcode build . --configuration Debug --dev-server-url '<absolute-url>'

If the app launches without using the expected URL, open it explicitly to separate build/install issues from URL routing:

lim ios open-url --id <ios-instance-id> '<absolute-url>'

Generated Xcode projects (XcodeGen)

If the repo has a project.yml and the .xcodeproj is gitignored, do not run xcodegen locally and do not treat the missing project as an error. The remote sandbox generates the project from project.yml before building:

lim xcode build .

The spec is found at the repo root or one directory down (like ios/), no flags needed. The project regenerates on every build, so project.yml edits take effect by just rebuilding. A committed or force-synced .xcodeproj always wins: the sandbox only generates when the sync didn't supply one.

If the repo's codegen produces gitignored inputs the build needs (a generated local Swift package, config-derived sources), run that step locally first and force-sync its output with --include:

make generate   # or whatever the repo's codegen step is
lim xcode build . --include '^ios/GeneratedKit/'

--include takes a regular expression like --ignore, not gitignore syntax. To reach files under a directory that is ignored as a whole, the pattern must also match the directory path itself, as above.

Run on a simulator

lim xcode build is build-and-install. Don't attach a simulator until the user needs to see or interact with the app. Check / attach:

lim xcode get             # is a simulator already attached?
lim ios create --attach   # attach one (installs the last build immediately)

Add --no-open when you have no browser to show the user; it skips opening the stream URL locally and still prints it for sharing.

If the attach output includes a signed stream URL, share it with the user as a Markdown link, such as [Live simulator](<signed-stream-url>).

When a simulator is attached, every successful lim xcode build automatically reinstalls and relaunches the app, no separate install step. To tap, type, read the element tree, screenshot, or record, switch to limrun-ios-simulator.

Run tests (XCTest)

lim xcode test builds the scheme's test targets on the sandbox, runs them on an attached simulator (unit and UI targets alike), and streams one line per test case. The exec exits non-zero when any test fails, so it works as a CI gate.

lim xcode test .
lim xcode test ./MyProject --scheme MyApp

It auto-acquires a simulator-backed target like lim xcode build --ios and reuses the instances on repeat runs, so iterating is fast. The scheme must have a test action configured (shared schemes from Xcode have one when the project has test targets). --xcode-version 27 builds the tests with that Xcode; the simulator keeps the fleet default runtime, so the run warns and proceeds (runtime-dependent failures are possible).

Select a subset with xcodebuild's identifier format Target[/Class[/method]]; repeat the flag for multiple entries. The two flags are mutually exclusive:

lim xcode test . --only-testing MyAppTests/LoginTests/testValidLogin
lim xcode test . --skip-testing MyAppUITests

A bare target name selects or skips that whole target. An --only-testing entry naming a target the build did not produce fails the run instead of silently running everything.

For machine consumption, --json streams the raw per-case events as NDJSON and ends with a {"exitCode": N} record:

lim xcode test . --json > results.ndjson

--build-only compiles the test targets without acquiring a simulator; the products stay on the sandbox for a later run.

If UI tests fail at the very first interaction on an instance that has run many suites back to back, prefer fresh instances with --inactivity-timeout 30m on the next run.

Signed device builds (IPA)

Prefer Apple cloud signing when the user has an App Store Connect team API key. Apple creates or reuses a cloud-managed certificate and provisioning profile, so the user does not need to supply a p12 or .mobileprovision:

lim xcode build . --sdk iphoneos --configuration Release \
  --signing-method release-testing --team-id "$APPLE_TEAM_ID" \
  --asc-key-id "$ASC_KEY_ID" --asc-issuer-id "$ASC_ISSUER_ID" \
  --asc-key AuthKey.p8 \
  --upload myapp.ipa

Signing methods:

• debugging: development-signed IPA for registered development devices.
• release-testing: distribution-signed IPA for registered test devices.
• app-store-connect: distribution-signed IPA for App Store Connect.

Cloud signing requires a device SDK (--sdk iphoneos or --sdk watchos), a team API key with an issuer ID, and --team-id matching that key's Apple Developer team. For distribution methods, the API key must be an Admin key or have Access to cloud-managed distribution certificates enabled. A Cloud signing permission error means that permission is missing. No Account for Team means the team ID and API key do not match. Failed Registering Bundle Identifier means the bundle ID belongs to another team and cannot be registered automatically.

Cloud signing takes entitlements only from --entitlements, never from the project's .entitlements file: the archive is unsigned and the export preserves entitlements only from an existing code signature. Any app using capabilities (HealthKit, CloudKit, app groups, push) MUST pass the flag or the capability is silently stripped from the IPA. A bare path targets the app; <bundleId>=<path> targets an embedded bundle (widget, watch app); repeat per bundle:

lim xcode build . --sdk iphoneos --configuration Release \
  --signing-method release-testing --team-id VMBY3VYW4U \
  --asc-key-id 2X9R4HXF34 --asc-issuer-id "$ASC_ISSUER_ID" \
  --asc-key AuthKey.p8 \
  --entitlements ./MyApp/MyApp.entitlements \
  --entitlements com.example.myapp.widgets=./Widgets/Widgets.entitlements \
  --upload myapp.ipa

The plist values must be fully expanded (no $(AppIdentifierPrefix); write the concrete prefix), must omit export-managed keys (application-identifier, com.apple.developer.team-identifier, get-task-allow, beta-reports-active), and every capability must be enabled on the App ID in the developer portal or the export fails naming it.

Manual signing remains available when the user already has a p12 and profiles:

lim xcode build . --sdk iphoneos --configuration Release \
  --certificate-p12 dist.p12 --certificate-password "$P12_PASSWORD" \
  --provisioning-profile app.mobileprovision \
  --upload myapp.ipa

The upload output includes a download URL for the signed IPA. A SUCCEEDED build means the signature already passed Apple's verifier on the server, so don't re-verify the IPA yourself unless the user asks. Invalid signing fails the build loudly instead of producing a broken artifact.

If the app embeds extensions (WidgetKit widgets, share sheets, intents) or a watch app, App Store signing needs one provisioning profile per bundle id, all issued for the same distribution certificate. Repeat --provisioning-profile once per bundle; each profile is matched to its bundle by the application-identifier inside it, so order doesn't matter:

lim xcode build . --sdk iphoneos --configuration Release \
  --certificate-p12 dist.p12 --certificate-password "$P12_PASSWORD" \
  --provisioning-profile app.mobileprovision \
  --provisioning-profile widgets.mobileprovision \
  --upload myapp.ipa

With multiple profiles, every profile must carry an explicit (non-wildcard) bundle id. A signing preflight failed: no provisioning profile covers ... error names the embedded bundle that lacks a profile; ask the user for a profile with exactly that bundle id.

Use a p12 that includes its full CA chain, not just the leaf certificate. If needed, re-export it with the chain:

openssl pkcs12 -export -inkey dist.key -in dist.pem -certfile wwdr.pem -out dist-chain.p12

Failure strings to recognize in the build output:

• Unknown issuer hash: the p12 lacks its CA chain; re-export it with the chain as above.
• code signature verification failed: the platform's post-sign check rejected the artifact. Not a problem in the user's code; retry, and report it if it persists.
• p12 password errors: --certificate-password doesn't match the file; ask the user for the right password.

Upload to App Store Connect

To upload the signed IPA to App Store Connect for TestFlight or App Store distribution, pass --upload-to-appstore with the App Store Connect API key flags on a signed device build:

lim xcode build . --sdk iphoneos --configuration Release \
  --certificate-p12 dist.p12 --certificate-password "$P12_PASSWORD" \
  --provisioning-profile app.mobileprovision \
  --upload-to-appstore --asc-key-id "$ASC_KEY_ID" --asc-issuer-id "$ASC_ISSUER_ID" \
  --asc-key AuthKey.p8

Cloud signing can sign and upload with the same API key:

lim xcode build . --sdk iphoneos --configuration Release \
  --signing-method app-store-connect --team-id "$APPLE_TEAM_ID" \
  --asc-key-id "$ASC_KEY_ID" --asc-issuer-id "$ASC_ISSUER_ID" \
  --asc-key AuthKey.p8 \
  --upload-to-appstore --auto-build-number

--upload-to-appstore requires either cloud signing or the manual signing flags, plus --asc-key-id and --asc-key. Combine it with --upload <asset-name> when the user also wants the IPA in Asset Storage.

Device IPAs carry the app's symbols (Symbols/ next to Payload/), so App Store Connect symbolicates crash reports without a separate dSYM upload. This needs the build to produce dSYMs: --configuration Release does by default; Debug does not, and the IPA then simply ships without symbols.

Collect from the user (all three live in App Store Connect under Users and Access, Integrations tab, App Store Connect API):

• --asc-key-id: the Key ID next to their API key. If they don't have one, point them at Team Keys with the Developer role: the least-privileged role that can upload builds. Creating team keys needs an Admin account.
• --asc-issuer-id: the Issuer ID at the TOP of the Integrations page (a team value, not per-key). Cloud signing requires a team key and this flag. For manual signing plus upload, omit it for individual API keys.
• --asc-key: path to the downloaded .p8 file. Apple keeps no copy and the download link disappears after leaving the page; if the user lost it, they must generate a new key. Never commit the .p8 or paste its content into files; pass a filesystem path.

By default the build returns as soon as the upload commits and leaves Apple's processing verdict to App Store Connect (processing routinely takes many minutes). Pass --asc-wait-timeout <seconds> (max 1800) to watch for the verdict before returning. Read the outcome from the final lines:

• App Store Connect: upload accepted.: done; the build appears in TestFlight once Apple finishes.
• App Store Connect: uploaded, still processing on Apple's side (upload <id>).: the exit code is 0 and the upload succeeded; Apple is still processing. Do NOT retry the build.
• App Store Connect upload failed; the build and signing succeeded.: exit code 1 with Apple's error text earlier in the log. Only the delivery failed.

Failure strings to recognize:

• Apple text about the bundle version being already used: bump CFBundleVersion (Expo: expo.ios.buildNumber in app.json) and rebuild.
• HTTP 401: key ID / issuer ID / .p8 mismatch, or a revoked key.
• HTTP 403: the key's role cannot upload builds; it needs the Developer role or higher.
• no App Store Connect app with bundle id: the app record doesn't exist; the user must create it in App Store Connect manually (the API cannot).
• Build later stuck at "Missing Compliance" in TestFlight: the app doesn't answer the export-compliance question at build time. Set ITSAppUsesNonExemptEncryption to NO in Info.plist (Expo: expo.ios.config.usesNonExemptEncryption: false in app.json) and rebuild.

For hands-off delivery to testers, the app's internal TestFlight group must have automatic distribution enabled (create-only setting) and the compliance key above must be set; then no post-upload steps exist at all.

Preview builds

Only create a reusable preview asset when the user asks for a preview build or when you're opening a PR. Build and upload:

ASSET_NAME="<bundle id / pr number / or any session identifier>.zip"
lim xcode build . --upload ${ASSET_NAME}
# Debug preview build:
lim xcode build . --configuration Debug --upload ${ASSET_NAME}

Build uploads default to a 14-day TTL: each build pushes the asset's expiry to 14 days from that upload. Pass --upload-ttl with a Go duration (e.g. 720h; 1d is invalid) to change it.

Then construct the preview link and include it in your last message (and in the PR, if you're opening one):

https://console.limrun.com/preview?asset=${ASSET_NAME}&platform=ios

Gotchas

• Build errors are your job to fix. If a build fails, read the error output, fix the code, and rebuild. Don't ask the user to fix build errors.
• Instance ID for lim ios commands. They resolve the current instance from the git worktree of your cwd and can fail with No instance ID provided and no recent ios instance found. Get the ID from lim xcode get and pass --id <ios-instance-id>; full recipe in limrun-ios-simulator's "Targeting the right instance" section.
• Bundle ID discovery. If you don't know the bundle ID, check the Xcode project files or run lim ios list-apps after a successful build.
• Auth errors on an authenticated command mean the session expired or LIM_API_KEY is wrong; ask the user to run lim login or provide a key.
• Build settings override Limrun's defaults. --build-setting KEY=VALUE accepts any environment-style key and replaces the managed value with the same key. Device builds already use standard architectures (an embedded watch app keeps arm64_32) and disable coverage instrumentation, so App Store uploads need no extra settings.
• Artifact not found after a successful build. The server resolves the built .app on its own, including when the scheme name differs from the product name (scheme "MyApp Dev" building MyApp-dev.app). If an upload still fails with built artifact not found, pass the full bundle filename explicitly with --artifact-name MyApp-dev.app (including the .app extension); the server then takes that name from the build products verbatim.
• Keep synced files small. A single ~2MB+ file can fail the client-side sync with ENOMEM before the build starts; compress large assets.
• Symlinks sync when relative and in-root. A symlink whose target is an absolute path is skipped with a warning; recreate it with a relative target if the build needs it. A relative link escaping the synced folder fails the sync; --ignore it or sync from the repo root that contains the target.
• Signing failures are loud and specific. Unknown issuer hash means the p12 lacks its CA chain, so re-export it with the chain; code signature verification failed means the platform's post-sign check rejected the artifact, which is not a code problem, so retry or report it.