web: screenshot --crop-on is refused (CROP_TARGET_NOT_ACCEPTED / PENDING_PIXEL_IDENTITY_EVIDENCE); what evidence would unblock it? #2583

agent-device 0.21.0, --platform web via agent-device web setup (agent-browser 0.27.1), Node 24.18, macOS. Target: expo export --platform web of the react-native-paper example app served on 127.0.0.1 (callstack/react-native-paper#5115).

open and a full-page screenshot work on web (1280x577 returned). --crop-on, which is the basis of the per-component loop that works on iOS simulators and Android emulators, is refused:

npx agent-device@0.21.0 screenshot web-crop.png --crop-on 'id="surface-example-elevated"' --platform web --session web --json
→ UNSUPPORTED_OPERATION: screenshot --crop-on is not accepted on web targets
   details: { "reason": "CROP_TARGET_NOT_ACCEPTED", "rejectionReason": "PENDING_PIXEL_IDENTITY_EVIDENCE" }

The docs do say crop-on is "currently accepted on iOS simulators and Android emulators", so this is expected behaviour, not a bug. Filing it as a request: the rejectionReason suggests it is waiting on evidence that the web node rect maps to pixels reliably; if there is a way to contribute that evidence, or a timeline, it would decide whether a web leg of a cross-platform visual suite can reuse the same per-section loop or has to diff full viewports.