sim-use

name	sim-use
description	Drive iOS Simulator and Android emulator/device screens for AI agents. Use when asked to automate a simulator or emulator, tap/swipe/type on a device, describe UI, take a screenshot, or interact with a mobile app.

0. Preflight

Before first interaction with a device, run the preflight check:

python3 scripts/preflight.py --device <UDID>

This verifies sim-use is installed, the device is reachable, and the daemon is healthy. If you don't have the script, do the checks manually:

1. sim-use --version — confirm sim-use is on PATH.
2. sim-use devices — confirm the target device is listed and booted/connected.
3. sim-use ui --device <UDID> — confirm you can read the screen.

--device is optional when only one simulator is booted or one daemon is running. For Android, run sim-use android init --device <serial> once to install the bridge APK.

1. The observe-act loop

Every interaction follows the same cycle: observe → act → verify.

Observe

sim-use ui --device <UDID>

Read the outline. Each element has an @N alias and optionally a #<id> identifier. List cells carry #N (dominant list) or #N@M (scoped).

Act

Pick a selector, in order of preference:

Selector	When to use
tap @N	Right after ui. Fastest, cache-backed.
tap #<id>	Stable across minor layout changes. Paste from the outline.
tap --label 'X'	Scripted flows. Combine with --wait-timeout for transitions.
tap --label-regex '...'	Dynamic labels with counters/timestamps. Anchor with ^...$.
tap --label-contains 'X'	Substring match when exact label is unknown.
tap -x N -y N	Last resort for elements with no AX data.

Disambiguate collisions with --element-type or --frame minY=0.7r (see references/cheatsheet.md).

Verify

Always verify after acting — commands are fire-and-forget:

sim-use ui --device <UDID>       # read the new screen state
sim-use screenshot --device <UDID> --output after.png

Common moves

Task	Command
Scroll down	sim-use gesture scroll-up --device <UDID> (scroll-up = content moves up = page down)
Type text	sim-use type 'hello' --device <UDID>
Paste unicode	sim-use paste 'こんにちは 🎉' --device <UDID> (iOS: needs hardware keyboard)
Hardware button	sim-use button home --device <UDID>
Android back	sim-use button back --device <UDID>
Wait for animation	sleep 0.4 between commands, or --pre-delay 0.5
Toggle/switch	sim-use tap @N --duration 0.05 --device <UDID> (UISwitch needs a brief hold)

2. Pitfalls

Quick symptom index — see references/pitfalls.md for detailed recipes.

Symptom	Cause	Fix
tap --label hits wrong element	Label collision (e.g. header and tab bar share text)	Add --frame minY=0.7r or --element-type to narrow
tap @N fails after navigation	Alias cache is stale	Re-run ui before tapping
App: line shows wrong app	System layer (alert, share sheet) is on top	Dismiss it first, then re-run ui
multipleMatches error	Several elements share the selector	Use --frame, --element-type, or a more specific selector
Tap lands but nothing happens	Animation in progress, or element not yet interactive	Add --pre-delay 0.3 or --wait-timeout 3
iOS: paste drops text	Soft keyboard only; HID Cmd+V is ignored	Use paste --via-menu --target-id <id>
Android: paste denied	Background clipboard access blocked	Use type instead
Outline shows U+FFFC in label	iOS icon placeholder character	Match with --label-regex excluding the prefix

3. Crash awareness

sim-use watches for the target process disappearing between commands. When it detects a crash:

================ PROCESS DISAPPEARED ================
com.example.app (pid 12345) was alive at the previous command and is GONE now.

On Android, ui also detects the AOSP system crash dialog directly from the accessibility tree.

Mandatory response:

1. STOP. Do not silently relaunch or continue.
2. Report the crash to the user with the banner text.
3. Wait for instructions before proceeding.

After an intentional relaunch, call sim-use app-state --reset to clear the signal.

4. Escalation

Stop and ask the user when:

• A selector collision cannot be resolved with available disambiguators.
• Preflight fails and autofix does not recover.
• The task requires a destructive action (deleting data, uninstalling an app).
• You've retried the same action 3 times without progress.

5. Exit checklist

Before reporting a task as complete:

1. Run sim-use ui (or screenshot) to capture the final state.
2. Confirm the screen matches the intended outcome.
3. If the outcome is ambiguous, show the final ui output or screenshot to the user.