[Bug] scroll_to causes MCP server connection closed and process crash

[charliewwdev]

Environment

• flutter-skill version: v0.9.5 (flutter-skill-macos-arm64-v0.9.5)
• Flutter: 3.32.2 / Dart 3.8.1
• Platform: iOS Simulator (iPhone 16 Pro, BCCC538A-B4BB-45F4-8F80-9F9C44B9ED8B)
• Claude Code MCP integration

Steps to Reproduce

1. Connect to a running Flutter app via connect_app(uri="ws://127.0.0.1:50000/{token}/ws")
2. Successfully use other tools (tap, native_screenshot, get_interactable_elements, go_back)
3. Call scroll_to with a widget key that is off-screen

Expected Behavior

scroll_to scrolls the list to bring the target element into view and returns success.

Actual Behavior

1. scroll_to returns: MCP error -32000: Connection closed
2. After the error, all flutter-skill MCP tools become unavailable with Error: No such tool available: mcp__flutter-skill__native_screenshot
3. The MCP server process crashes entirely — tools disappear from the MCP tool registry
4. Requires full Claude Code restart to recover

Impact

• Critical: any call to scroll_to terminates the entire MCP server session
• Workaround: use swipe instead of scroll_to for scrolling

Additional Context

The crash occurs specifically when the element is off-screen. The error log shows:

E002: Element "settings_dark_mode" is off-screen (coords: 67, 967).

Immediately followed by scroll_to call → Connection closed → server crash.

[charliewwdev]

Fixed in v0.9.31 🎉

Root cause: Scrollable.ensureVisible() was called on a potentially unmounted BuildContext, throwing an unhandled exception that propagated through the VM Service connection and crashed the MCP server.

Fix (two layers of protection):

1. Flutter binding (lib/flutter_skill.dart): The _performScroll method now checks element.mounted before calling Scrollable.ensureVisible(), and adds a 5-second timeout to prevent hanging.

2. MCP server (bf_interaction.dart): scroll_to now wraps the call with an 8-second timeout and returns a helpful error with a suggestion to use swipe() instead if the element is unreachable.

Example error response (instead of a crash):

{
  "success": false,
  "error": "scroll_to timed out — element may be unreachable.",
  "suggestion": "Use swipe(direction: 'up') to scroll manually, then retry scroll_to once the element is closer to the viewport."
}

Please update to flutter_skill: ^0.9.31 in your pubspec.yaml.