## Implementation Evidence

Date: 2026-07-21
Host: macOS arm64

### Behavior verification

- Focused interactive-instruction and startup tests:
  - Command: `dotnet test MeetingAssistant.Tests/MeetingAssistant.Tests.csproj --filter 'FullyQualifiedName~InstructionBuilder|FullyQualifiedName~ApplicationStartupRegistersDetectedHostOperatingSystemOnce' --no-restore --nologo`
  - Result: passed, 11/11.
- The focused tests cover Windows guidance, macOS guidance, unsupported-host fallback, custom-prompt retention, and singleton startup detection.

### Build and spec verification

- Portable application build:
  - Command: `dotnet build MeetingAssistant/MeetingAssistant.csproj -f net10.0 --no-restore --nologo`
  - Result: succeeded with 0 warnings and 0 errors.
- OpenSpec validation:
  - Command: `openspec validate detect-host-operating-system --strict`
  - Result: valid.
- Diff check:
  - Command: `git diff --check`
  - Result: passed.

### Broader test result and known limitations

- Full portable test project:
  - Command: `dotnet test MeetingAssistant.Tests/MeetingAssistant.Tests.csproj --no-restore --nologo`
  - Result: 422 passed, 9 failed.
  - The 9 failures are the pre-existing macOS failures identified before this change: Windows/GDI+ image rendering, Windows-path expectations, and Windows user-environment behavior. None exercise the new host detection or platform instruction output.
- Windows target:
  - Restore with `EnableWindowsTargeting=true` succeeded.
  - Native Windows build cannot complete on macOS because the Windows SDK attempts to execute `MakePri.exe` and returns `Exec format error`. Windows CI or a Windows host remains the appropriate verification environment for that target.

### Refactoring review

- DRY review consolidated shared platform-guidance policy text and reused the production detector in the startup test.
- SOLID review found no actionable issue.
- KISS review found no actionable simplification.

The live Meeting Assistant process was not restarted or modified during verification.