| name | designer-runtime |
| description | Pilot local iOS Simulators for UI/design/QA work on macOS, especially Flutter or native iOS visual verification. Use explicitly when Codex needs to list booted simulators, launch or stop a simulator app, run or hot reload Flutter through a background unified_exec terminal, inspect accessibility hierarchy with idb, tap/type/swipe, capture screenshots, crop screenshots, or provide visual proof from an iOS Simulator. |
Designer Runtime
Use this skill for direct local iOS Simulator piloting from Designer or QA agents. It is macOS-only and prerequisite-gated: use it only when the host is macOS with Xcode command-line tools and an iOS Simulator runtime available. Keep it small and evidence-oriented: interact with the app, capture proof, report what changed or failed.
Before starting, confirm the required host tools are available. xcrun is required for simulator discovery and app launch; idb is required for hierarchy and interaction commands; and ImageMagick's magick is required for selector crops and manual crops. Flutter loops additionally require flutter. If a prerequisite is missing, stop with an actionable blocker rather than installing software or mutating host configuration.
Prefer existing XcodeBuildMCP simulator tools when they are available for a native iOS app. Use Codex's background shell session support for long-running Flutter/dev-server processes. Use the bundled designer-sim script for ad-hoc idb interaction, screenshot capture, and crop evidence.
Guardrails
- Use one simulator per active loop and run commands sequentially.
- Do not erase, delete, or shut down simulators.
- Do not kill Simulator, CoreSimulator, or CoreSimulator services.
- Do not run project-wide build/analyze/test/format commands while parallel edits may still be active unless the parent asks for a verification sync point.
- Keep long-running app processes in one background terminal session and poll that session for output instead of wrapping it in tmux.
- Capture screenshots or logs for product blockers and include absolute paths in the result.
- Prefer selector-based taps/crops when accessibility labels or identifiers are available; use coordinates only when the hierarchy is insufficient.
Scripts
The scripts live in this skill's scripts/ directory. Run them by absolute path if they are not on PATH.
designer-sim devices
designer-sim hierarchy --device-id <UDID>
designer-sim screenshot --device-id <UDID> --out /tmp/proof.png
designer-sim screenshot --device-id <UDID> --selector '{"text":"Continue"}' --out /tmp/continue.png
designer-sim tap-on --device-id <UDID> --selector '{"text":"Continue"}'
designer-sim tap --device-id <UDID> --x 120 --y 240
designer-sim text --device-id <UDID> --text "hello"
designer-sim swipe --device-id <UDID> --from 180,700 --to 180,220
designer-sim launch --device-id <UDID> --bundle-id com.example.app
designer-sim terminate --device-id <UDID> --bundle-id com.example.app
designer-sim open-url --device-id <UDID> --url myapp://debug
Flutter Loop
-
Start the app in a background terminal with the shell tool's session mode, from the app workdir:
flutter run -d <UDID>
-
Poll the session output until Flutter reports the app is running or shows a concrete failure.
-
Inspect state with designer-sim hierarchy or designer-sim screenshot.
-
Make one interaction at a time with designer-sim tap-on, tap, text, or swipe.
-
After code edits, send r to the same background session to hot reload, then poll for the reload result.
-
Capture final proof with designer-sim screenshot --out <absolute-path>.
-
Stop the app by sending q or Ctrl-C to the same background session when the loop is done.
Do not use tmux for this workflow unless the user explicitly asks for it or the shell session tool is unavailable.
Selector JSON
Selectors are small JSON objects. Common keys:
{"text":"Continue"}
{"label":"Settings"}
{"id":"save-button"}
{"name":"Close"}
{"value":"Selected"}
Matching is case-insensitive exact text by default. Add "contains": true for substring matching:
{"text":"continue", "contains": true}
Visual Proof
Use screenshot paths under /tmp/codex-designer-runtime/ or another absolute path. For final reports, include:
- device UDID or simulator name
- command or flow tested
- screenshot path
- observed blocker, if any
