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Result Log: 2026-03-10 16:27:26 CST

Goal

Diagnose and fix the reproduced Chrome-to-Notepad switch failure.

Investigation

Controlled live comparison

From Chrome foreground:
- App.switch("Calculator") passed
- App.switch("Notepad") failed
That narrowed the issue from a generic browser-to-desktop switch failure to a more specific focus-path defect.

Focus diagnosis probe

Added research/experiments/switch_focus_diagnose.py
Sequential runs showed:
- with Chrome foreground and Notepad target, the foreground remained Chrome for the full observation window
- the Win32 path completed without exception, so the old code never entered the fallback focus path

Root cause

bring_window_to_top() only used _focus_window_fallback() on exceptions.
It did not fall back when the Win32 path returned cleanly but still failed to move the actual foreground.

Patch

bring_window_to_top() now calls _focus_window_fallback() whenever GetForegroundWindow() still does not equal the target after the Win32 path completes.

Verification

Local

tests/test_app_service.py
- pass
full suite
- 183 passed in 5.58s

Live

reloaded the hot worker with DevServer(mode="reload")
reran the exact Chrome-to-Notepad path
App.switch("Notepad")
- pass
follow-up Snapshot
- pass
- foreground window was *wmcp-type-probe-1773117083.txt - Notepad

Methodology Takeaway

A first attempt to compare Notepad and Calculator probes in parallel was invalid because both manipulated the same shared desktop state.
UI-state-changing experiments must be run sequentially.