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How to test iOS apps with GStack iOS

This is the end-to-end walkthrough for the iOS QA capability that ships with gstack: install the canonical Swift templates into your app, connect a real iPhone over USB, and drive it from any agent (Claude Code locally, or any HTTP-capable agent over Tailscale). No simulators, no XCTest harness, no WebDriverAgent.

Everything below has been verified end-to-end on a real iPhone 17 Pro Max running iOS 26.5. The same flow works on any iOS 16+ device.

What you'll need

  • macOS with Xcode 16.0+ installed (xcrun devicectl --version must succeed). Xcode 16 ships the CoreDevice tunnel devicectl uses to reach the device over USB.
  • A real iPhone running iOS 16 or later. Unlocked, paired with your Mac, with Developer Mode enabled in Settings → Privacy & Security.
  • An Apple developer team — the free personal team works fine for live-device debug deploys. You'll need the team ID (e.g. 623FYQ2M88), not the certificate ID. Find it in Xcode → Settings → Accounts → your Apple ID → team list. The setup signs the app for your device on first deploy via -allowProvisioningUpdates -allowProvisioningDeviceRegistration.
  • gstack installed (./setup complete; bin/gstack-ios-qa-daemon must be on disk and executable).
  • Bun runtime on PATH (bun --version). The Mac-side daemon is a bun process.

For the optional remote-agent (Tailscale) mode, you'll additionally need Tailscale installed on the Mac with /var/run/tailscale.sock readable.

Architecture in one breath

┌─────────────────┐   tailnet (opt)    ┌──────────────────────┐   USB CoreDevice    ┌─────────────────────┐
│ Remote agent    │ ─────────────────▶ │ gstack-ios-qa-daemon │ ──────────────────▶ │ iOS app StateServer │
│ (Claude, GPT,   │  bearer + session  │  (Mac, bun/TS)       │  IPv6 ULA tunnel    │  (loopback only)    │
│  OpenClaw, ...) │                    │                      │                     │                     │
└─────────────────┘                    └──────────────────────┘                     └─────────────────────┘
  • iOS app embeds a StateServer (DebugBridge SPM library, #if DEBUG only) listening on ::1 + 127.0.0.1 port 9999. Bearer-token gated. Boot token rotates within ~5 seconds of daemon spawn so anything scraping os_log past then sees a dead credential.
  • Mac daemon brokers traffic over the CoreDevice IPv6 tunnel that xcrun devicectl opens automatically when a paired device is connected.
  • In Tailscale mode, the daemon exposes a separate listener bound to your tailnet IP, with capability tiers (observe / interact / mutate / restore) enforced per session token. Tokens are minted explicitly by the Mac owner via gstack-ios-qa-mint; remote callers never auto-allowlist.

The iOS StateServer is loopback-only always, even in remote mode. Identity validation happens Mac-side because the iPhone has no way to validate a Tailscale identity.

Step 1: Add the DebugBridge templates to your iOS app

The templates live at ~/.claude/skills/gstack/ios-qa/templates/ after ./setup. The fastest install is to invoke the /ios-qa skill in Claude Code from your app's root — it reads your Swift source, codegens typed @Observable state accessors, and lays down the templates with your bundle ID. Or do it by hand:

  1. Copy these into a DebugBridge/ SPM package inside your app workspace:

    • Sources/DebugBridgeCore/StateServer.swift (from StateServer.swift.template)
    • Sources/DebugBridgeCore/DebugBridgeManager.swift (from DebugBridgeManager.swift.template)
    • Sources/DebugBridgeTouch/DebugBridgeTouch.m + Sources/DebugBridgeTouch/include/DebugBridgeTouch.h (from the two .template files)
    • Sources/DebugBridgeUI/Bridges.swift (from Bridges.swift.template)
    • Sources/DebugBridgeUI/DebugOverlay.swift (from DebugOverlay.swift.template)
    • Package.swift (from Package.swift.template)

  2. Add the package as a local dependency of your app. Depend on the DebugBridgeUI product with condition: .when(configuration: .debug). DebugBridgeCore and DebugBridgeTouch come in transitively.

  3. In your @main App init, gate the wiring on #if DEBUG:

    #if DEBUG
import DebugBridgeCore
StateServer.shared.start()
#if canImport(UIKit)
import DebugBridgeUI
DebugBridgeUIWiring.installAll()
#endif
#endif

The three Swift targets split as: DebugBridgeCore is cross-platform (so swift build on a CI Mac host can validate the bulk of the code without UIKit), DebugBridgeUI and DebugBridgeTouch are iOS-only (they link UIKit). DebugBridgeTouch is Objective-C — it carries the KIF-derived UITouch synthesis with the iOS 18+ _UIHitTestContext fix that makes SwiftUI Button taps actually fire.

The structural Release-build guard is the .when(configuration: .debug) clause in Package.swift. SwiftPM refuses to link any DebugBridge* target in a Release build, so the bridge cannot ship to TestFlight even if you forget to clean up.

Step 2: Build + install to the device

From the app's project directory:

xcodebuild \
  -scheme YourAppScheme \
  -configuration Debug \
  -destination 'generic/platform=iOS' \
  -derivedDataPath /tmp/build \
  -allowProvisioningUpdates -allowProvisioningDeviceRegistration \
  CODE_SIGN_STYLE=Automatic \
  DEVELOPMENT_TEAM=YOUR_TEAM_ID \
  build

Then install + launch:

UDID=$(xcrun devicectl list devices 2>/dev/null | awk 'NR>2 && $0!="" {print $(NF-2); exit}')
xcrun devicectl device install app --device "$UDID" /tmp/build/Build/Products/Debug-iphoneos/YourApp.app
xcrun devicectl device process launch --device "$UDID" --terminate-existing your.bundle.id

If the phone is locked you'll get FBSOpenApplicationServiceErrorDomain error 1 — Locked. Unlock and retry. First-time installs surface a Trust dialog on the phone; tap Trust, then re-run.

Step 3: Start the Mac-side daemon

Two options.

Option A — let the skill spawn it. Run /ios-qa in Claude Code from anywhere; the skill spawns the daemon on demand, bootstraps the tunnel, rotates the boot token, and exposes the device through the proxy. Cleanest path for local-USB use.

Option B — start it yourself. Run:

gstack-ios-qa-daemon

The daemon prints READY: port=<n> pid=<pid> once both loopback listeners are bound. The default port is 9099. Spawners can read that line with a ~5 second timeout to confirm readiness; you can also point curl at the printed port.

Either way the daemon takes an exclusive flock on ~/.gstack/ios-qa-daemon.pid — running it twice from two Claude Code sessions is safe; the second invocation discovers the running daemon's port and joins.

Set these env vars to target a specific device or bundle:

GSTACK_IOS_TARGET_UDID=248C3A58-B843-5BDB-8F5D-89ADB7D7BF6A
GSTACK_IOS_TARGET_BUNDLE_ID=com.yourorg.yourapp
GSTACK_IOS_DAEMON_PORT=9099       # loopback listener port; default 9099

If GSTACK_IOS_TARGET_UDID is unset, the daemon picks the first paired connected device.

Step 4: Drive the device

Once the daemon is running, you have an HTTP surface at http://127.0.0.1:9099 (or [::1]:9099). The skill flow does this for you, but the raw endpoints are:

Endpoint What it does Auth
GET /healthz Version probe. none (loopback)
POST /auth/rotate Daemon-only; rotates the boot token to an in-memory-only value. boot token
POST /session/acquire Acquire the per-device session lock. Returns {session_id, ttl_seconds}. bearer
POST /session/release Release the lock. bearer + session
GET /screenshot Capture a PNG of the active window. Returns {png_base64: "..."}. bearer
GET /elements Accessibility-tree snapshot. bearer
GET /state/snapshot Dump every @Snapshotable field as JSON. bearer
POST /state/restore Atomically restore a full snapshot. bearer + session, mutate tier
POST /tap {x,y} Synthesize a real UITouch at window coordinates. SwiftUI Buttons fire. bearer + session, interact tier
POST /swipe {from_x,from_y,to_x,to_y} Scroll the nearest enclosing UIScrollView. bearer + session, interact tier
POST /type {text} Set text on the current first responder. bearer + session, interact tier

Mutating requests require both an Authorization: Bearer <token> header AND an X-Session-Id header. Read endpoints (/screenshot, /elements, GET /state/*) only need the bearer.

The state snapshot is opt-in per field via a @Snapshotable property wrapper on your canonical state struct. Fields you don't annotate never appear in the snapshot, which keeps tokens, PII, and auth state out of recorded fixtures by default.

Step 5: Make remote agents work (optional)

To let an agent on another machine drive the device, run the daemon with --tailnet:

gstack-ios-qa-daemon --tailnet

The daemon probes /var/run/tailscale.sock first; if the socket is missing or unreadable, it refuses to open the tailnet listener at all (loopback still runs). Remote mode never half-starts.

Then mint a session token for the identity that should be able to connect:

gstack-ios-qa-mint grant --remote 'alice@example.com' --capability interact
gstack-ios-qa-mint grant --remote 'tag:ci' --capability mutate --ttl 86400 --note 'nightly'
gstack-ios-qa-mint list

Capability tiers are nested: observe (read endpoints only) ⊂ interact (taps, swipes, type) ⊂ mutate (POST /state/*) ⊂ restore (POST /state/restore). Pick the smallest tier that does the job. The allowlist file is at ~/.gstack/ios-qa-allowlist.json (mode 0600) — the daemon reads it on every /auth/mint request, so changes take effect immediately without restarting.

The remote agent then hits POST /auth/mint against the daemon's tailnet listener. The daemon canonicalizes the caller's identity via tailscaled's WhoIs endpoint, checks the allowlist, and returns a short-lived session token (1 hour default, 24 hour cap). Every authenticated mutating request lands in ~/.gstack/security/ios-qa-audit.jsonl; rejected requests land in ~/.gstack/security/attempts.jsonl.

Step 6: Ship a release build

Before you ship to TestFlight or the App Store, run /ios-clean. It removes the DebugBridge SPM dependency and strips the #if DEBUG wiring from your @main App. The structural guard in Package.swift (condition: .when(configuration: .debug)) means a Release build wouldn't link the bridge even if you forgot to clean up, but /ios-clean gives you a tidy diff to review and ship.

Common failures

Symptom What broke
xcodebuild fails with Could not locate device support files for iOS X.Y Run xcodebuild -downloadPlatform iOS to fetch the device support package for your iPhone's iOS version (~8GB).
Install succeeds, process launch fails with Locked The phone is locked. Unlock and retry.
First install on a paired device fails with no clear error The phone needs to Trust the Mac. Open Settings → General → VPN & Device Management on the phone and confirm.
Developer Mode toggle missing from Settings → Privacy Connect the device to Xcode → Window → Devices and Simulators once, or try any devicectl device install against it. iOS will surface the toggle after the first attempt.
xcrun devicectl device copy from returns ERROR 7000 The source path is wrong — boot token lives at tmp/gstack-ios-qa.token inside the app's data container (NSTemporaryDirectory), not at the path's root.
/healthz returns 200 but /tap returns ok:true with no UI change The phone is paired but the StateServer port may have changed across launches. Re-resolve the CoreDevice IPv6 (dscacheutil -q host -a name '<DeviceName>.coredevice.local').
403 identity_not_allowed from /auth/mint The remote caller's identity isn't on the Mac's allowlist. Run gstack-ios-qa-mint grant --remote <identity> --capability interact on the Mac.
Daemon won't open the tailnet listener Tailscale isn't installed, or /var/run/tailscale.sock is unreadable. Fix Tailscale, then restart the daemon. Loopback still runs in the meantime.
SwiftUI Button tap returns ok:true but the action never fires You're on iOS 17 or older where _UIHitTestContext doesn't exist. The DebugBridgeTouch implementation falls back to plain hitTest: which doesn't resolve into SwiftUI's gesture container. Update to iOS 18+ on the device, or tap a UIKit control instead.

What this gets you

You can write an agent loop in any language that speaks HTTP. Take a screenshot, ask a model what to do, send a tap. Capture state snapshots before and after to record deterministic fixtures for /ios-fix regression tests. Add a colleague to the allowlist and they drive your iPhone from their laptop over Tailscale without ever touching the hardware. Plug the same daemon into CI by minting a tag:ci session token with mutate-tier capability and a 24-hour TTL.

The whole stack is a Mac you already own, an iPhone you already own, a free Apple developer account, and gstack. No paid testing service. No simulator drift. The thing the user sees is what the agent drives.