---
phase: 06-global-site-selection
plan: 04
subsystem: tab-viewmodels
tags: [wpf, mvvm, community-toolkit, global-sites, override-pattern]

# Dependency graph
requires:
  - 06-01 (FeatureViewModelBase.OnGlobalSitesChanged virtual hook)
provides:
  - PermissionsViewModel.OnGlobalSitesChanged (multi-site: pre-populates SelectedSites)
  - StorageViewModel.OnGlobalSitesChanged (single-site: pre-fills SiteUrl)
  - SearchViewModel.OnGlobalSitesChanged (single-site: pre-fills SiteUrl)
  - DuplicatesViewModel.OnGlobalSitesChanged (single-site: pre-fills SiteUrl)
  - FolderStructureViewModel.OnGlobalSitesChanged (single-site: pre-fills SiteUrl)
  - TransferViewModel.OnGlobalSitesChanged (single-site: pre-fills SourceSiteUrl)
affects:
  - 06-05-per-tab-override (consumes GlobalSites in RunOperationAsync as fallback)

# Tech tracking
tech-stack:
  added: []
  patterns:
    - "partial void OnXxxChanged — CommunityToolkit partial property change notification used to detect local user input and set override flag"
    - "_hasLocalSiteOverride / _hasLocalSourceSiteOverride field pattern — prevents global site changes from overwriting user's local entry"
    - "Tenant switch resets override flag — ensures fresh tenant starts with global site pre-fill active"

key-files:
  created: []
  modified:
    - SharepointToolbox/ViewModels/Tabs/PermissionsViewModel.cs
    - SharepointToolbox/ViewModels/Tabs/StorageViewModel.cs
    - SharepointToolbox/ViewModels/Tabs/SearchViewModel.cs
    - SharepointToolbox/ViewModels/Tabs/DuplicatesViewModel.cs
    - SharepointToolbox/ViewModels/Tabs/FolderStructureViewModel.cs
    - SharepointToolbox/ViewModels/Tabs/TransferViewModel.cs

key-decisions:
  - "PermissionsViewModel uses _hasLocalSiteOverride to guard SelectedSites; site picker dialog sets flag to true, tenant switch resets it to false"
  - "Single-site VMs use partial void OnSiteUrlChanged to detect local typing; clearing the field reverts to global, non-empty different value sets override"
  - "BulkMembersViewModel excluded: confirmed no SiteUrl field (CSV-driven per-row site URLs)"
  - "SettingsViewModel, BulkSitesViewModel, TemplatesViewModel excluded per CONTEXT decisions — not modified"

# Metrics
duration: 2min
completed: 2026-04-07
requirements-completed:
  - SITE-01
  - SITE-02
---

# Phase 06 Plan 04: Tab ViewModels Global Site Consumption Summary

**All 6 consuming tab ViewModels wired to override OnGlobalSitesChanged — PermissionsViewModel pre-populates SelectedSites (multi-site), 4 single-site tabs pre-fill SiteUrl, TransferViewModel pre-fills SourceSiteUrl, all with local-override protection via _hasLocalSiteOverride flag**

## Performance

- **Duration:** ~2 min
- **Started:** 2026-04-07T08:06:19Z
- **Completed:** 2026-04-07T08:08:35Z
- **Tasks:** 3
- **Files modified:** 6

## Accomplishments

- PermissionsViewModel: Added `OnGlobalSitesChanged` override that pre-populates `SelectedSites` from global sites when no local override is active
- PermissionsViewModel: Site picker dialog (`ExecuteOpenSitePicker`) now sets `_hasLocalSiteOverride = true` before clearing/repopulating SelectedSites
- PermissionsViewModel: `OnTenantSwitched` resets `_hasLocalSiteOverride = false` so new tenant immediately uses global sites
- StorageViewModel, SearchViewModel, DuplicatesViewModel, FolderStructureViewModel: Added identical `OnGlobalSitesChanged` + `partial void OnSiteUrlChanged` + `_hasLocalSiteOverride` pattern
- TransferViewModel: Added `OnGlobalSitesChanged` + `partial void OnSourceSiteUrlChanged` + `_hasLocalSourceSiteOverride` pattern for `SourceSiteUrl`
- BulkMembersViewModel confirmed excluded — no `SiteUrl` field, CSV-driven, no changes made
- All 134 tests pass (0 failures, 22 skipped — same baseline as plan 06-01)
- Build succeeds with 0 errors, 0 warnings

## Task Commits

Each task was committed atomically:

1. **Task 1: Update PermissionsViewModel for multi-site global consumption** - `1bf47b5` (feat)
2. **Task 2: Update single-site tab VMs (Storage, Search, Duplicates, FolderStructure)** - `6a2e4d1` (feat)
3. **Task 3: Update TransferViewModel and verify BulkMembersViewModel excluded** - `0a91dd4` (feat)

## Files Created/Modified

- `SharepointToolbox/ViewModels/Tabs/PermissionsViewModel.cs` — Added `_hasLocalSiteOverride`, `OnGlobalSitesChanged`, updated `ExecuteOpenSitePicker` and `OnTenantSwitched`
- `SharepointToolbox/ViewModels/Tabs/StorageViewModel.cs` — Added `_hasLocalSiteOverride`, `OnGlobalSitesChanged`, `OnSiteUrlChanged`, updated `OnTenantSwitched`
- `SharepointToolbox/ViewModels/Tabs/SearchViewModel.cs` — Added `_hasLocalSiteOverride`, `OnGlobalSitesChanged`, `OnSiteUrlChanged`, updated `OnTenantSwitched`
- `SharepointToolbox/ViewModels/Tabs/DuplicatesViewModel.cs` — Added `_hasLocalSiteOverride`, `OnGlobalSitesChanged`, `OnSiteUrlChanged`, updated `OnTenantSwitched`
- `SharepointToolbox/ViewModels/Tabs/FolderStructureViewModel.cs` — Added `_hasLocalSiteOverride`, `OnGlobalSitesChanged`, `OnSiteUrlChanged`, updated `OnTenantSwitched`
- `SharepointToolbox/ViewModels/Tabs/TransferViewModel.cs` — Added `_hasLocalSourceSiteOverride`, `OnGlobalSitesChanged`, `OnSourceSiteUrlChanged`, updated `OnTenantSwitched`

## Decisions Made

- Used `partial void OnSiteUrlChanged` (CommunityToolkit partial method) to detect user typing — this fires for every programmatic and user-driven change, so the guard `value != GlobalSites[0].Url` ensures global pre-fills don't incorrectly set the override flag
- When user clears SiteUrl (empty string), the override resets and global is re-applied immediately — design choice to make clearing feel like "go back to global"
- PermissionsViewModel pattern differs from single-site VMs: it has no `OnSiteUrlChanged` because its authoritative input is `SelectedSites` (managed by site picker dialog), not free text

## Deviations from Plan

None — plan executed exactly as written. BulkMembersViewModel was confirmed to have no `SiteUrl` field as expected.

## Issues Encountered

None.

## User Setup Required

None — no external service configuration required.

## Self-Check: PASSED

All 7 expected files found. All 3 task commits verified in git log.

## Next Phase Readiness

- All 6 consuming tab VMs now react to `GlobalSitesChangedMessage` automatically
- Local override pattern is consistent across all tabs — users can type freely without clearing global state
- Plan 06-05 (per-tab override enforcement in RunOperationAsync) can proceed
- No blockers