context deadline exceeded on mobile_click_on_screen_at_coordinates and mobile_list_elements_on_screen when screen contains large accessibility tree (iOS simulator)

[pawelkw]

Summary

On iOS simulator, any interaction via mobile_click_on_screen_at_coordinates or mobile_list_elements_on_screen fails with context deadline exceeded when the current screen contains
a large number of UI elements (e.g. a scrollable list with hundreds of rows). mobile_take_screenshot is unaffected.

Environment

• mobile-mcp version: latest (npx)
• Platform: iOS simulator
• Device: iPhone 17 Pro simulator, iOS 26.1
• Host OS: macOS Darwin 25.3.0 (Apple Silicon)
• App under test: Native iOS app with a UITableView station-selection screen (~300+ rows)

Steps to Reproduce

1. Launch an iOS app that displays a long scrollable list (e.g. a UITableView with 200+ rows)
2. Call mobile_list_elements_on_screen — observe timeout
3. Call mobile_click_on_screen_at_coordinates at any coordinate on the same screen — observe timeout

Errors Observed

mobile_list_elements_on_screen:
failed to dump UI from device XXXX-XXXX-XXXX-XXXX-XXXXXX: failed to get source:
failed to fetch endpoint source?format=json&excluded_attributes=:
Get "http://localhost:13001/source?format=json&excluded_attributes=": context deadline exceeded

mobile_click_on_screen_at_coordinates:
failed to tap on device XXXX-XXXX-XXXX-XXXX-XXXXXX:
failed to post to endpoint session/xxxxxxxxxx/actions:
Post "http://localhost:13001/session/.../actions": context deadline exceeded

Expected Behaviour

• mobile_list_elements_on_screen either returns a paginated/truncated result or increases its timeout to handle large trees
• mobile_click_on_screen_at_coordinates performs a coordinate-based tap without requiring a full accessibility tree traversal — the tap should succeed regardless of list size

Actual Behaviour

Both calls hang and then fail. The WDA process (PID visible on port 13001) enters a broken state where it accepts new connections but all subsequent requests also time out,
requiring the process to be killed manually.

mobile_take_screenshot continues to work on the same screen, confirming the simulator and WDA process are alive — the issue is specifically with the accessibility tree endpoints.

Workaround

• Avoid mobile_list_elements_on_screen on large-list screens; use mobile_take_screenshot instead
• Use a search/filter input to reduce the list to a small number of items before attempting mobile_click_on_screen_at_coordinates
• Kill the WDA process (kill -9 ) after a timeout to restore functionality on other screens

Suggested Fix

For mobile_click_on_screen_at_coordinates: send the tap as a W3C Actions API pointer event at the given coordinates without first fetching the accessibility tree. The coordinates
are already known — no element lookup should be required.

For mobile_list_elements_on_screen: consider adding a snapshotMaxDepth cap to the WDA source request, as recommended in the
https://appium.github.io/appium-xcuitest-driver/latest/guides/wda-slowness/.

[gmegidish]

@pawelkw interesting! thank you for the bug report. I'll try to take a look what can cause it. I know that if we removed isVisible, then wda is 10x faster when grabbing view tree.

Question to you, are you using this on an app you developed? is "get-task-allow" boolean enabled on your app?

[pawelkw]

Yes, its an app we develop. Not sure about that flag, I'd have to check tomorrow. Would that flag make things better?

[pawelkw]

Anything we can do to fix it on our side? Can I force the isVisible check in WDA from my side?