fix(patrol_mcp): pass device serial to screenshot command (fails with multiple devices attached)

[godzeit]

Problem

The screenshot MCP tool shells out to capture the device screen without ever targeting a specific device:

• Android: adb exec-out screencap -p (no -s <serial>).
• iOS: xcrun simctl io booted screenshot ... (booted instead of the actual UDID).

ScreenshotService.handleScreenshotRequest(Device? device) already receives the patrol_cli Device for the active session, but only uses it to pick the platform (ScreenshotPlatform.fromDevice) — the device identity itself is discarded before the command is built.

Repro (Android, 2+ devices/emulators attached — common when running parallel emulators)

$ adb exec-out screencap -p
error: more than one device/emulator

With -s <serial> both devices return a valid PNG; without it the tool call fails outright. On iOS the failure mode is worse — with 2+ booted simulators, booted picks whichever simctl considers "the" booted device, which may silently be the wrong one instead of erroring.

Verified live against patrol_mcp 0.1.4 while running Patrol against a production Flutter monorepo with parallel Android emulators.

Fix

• ScreenshotPlatform now exposes argsFor(Device device) instead of a static args list, and builds the command with the device's identity:
  • Android: adb -s <device.id> exec-out screencap -p
  • iOS: xcrun simctl io <device.id> screenshot --type=png /dev/stdout (Device.id is the simulator UDID on iOS, per ios_test_backend.dart, which already does simctl ... device.id instead of booted)
• _captureScreenshot now takes the Device and threads it through to argsFor.

This aligns with how patrol_cli itself already targets devices — e.g. android_test_backend.dart sets 'ANDROID_SERIAL': device.id when running tests, and ios_test_backend.dart passes device.id (not booted) to simctl. The MCP screenshot tool was the odd one out.

Related gap fixed in the same package: native-tree

While auditing patrol_mcp for the same class of bug, NativeTreeService._setupConnection calls Adb().forwardPorts(fromHost: port, toDevice: port) without a device argument. The adb package's forwardPorts already accepts an optional device serial (see packages/adb/lib/src/adb.dart) specifically to disambiguate when more than one device is attached. Passed device: device.id here too, since it's the same root cause and a one-line fix in a file already touched by this class of bug.

Changes

• packages/patrol_mcp/lib/src/screenshot_service.dart — pass device serial/UDID to adb/simctl.
• packages/patrol_mcp/lib/src/native_tree_service.dart — pass device serial to Adb().forwardPorts.
• packages/patrol_mcp/CHANGELOG.md — unreleased entry.

Verification

dart analyze lib/src/screenshot_service.dart lib/src/native_tree_service.dart
# No issues found!

No test/ directory exists yet for patrol_mcp, so no existing test coverage was touched; happy to add coverage if maintainers point me at the preferred pattern for exercising Process.start args in this package.

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[zoskar]

@godzeit Thanks for the contribution!

[zoskar]

I pushed multi device support in general to TODO, thanks for contribution 💪