Setup aborts at Phase 5/11 (Full) because SearchHighlightOff cannot write the protected SearchSettings key on Windows build 28000

從 steps/registry-taskbar-search.ps1 開始，將 SearchHighlightOff 與相鄰的 WidgetServiceOff 步驟進行比較，後者已經處理受保護的 Windows 設定。在 Windows 11 build 28000 上執行 Full setup 動作，或者如果儲存庫提供了相應測試，則新增一個有針對性的回歸測試。當這個受保護的登錄值不再中止 setup 且後續階段繼續執行時，即表示完成。

Summary

On Windows 11 build 28000, the Full action aborts at Phase 5/11 because the SearchHighlightOff tweak cannot write HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\SearchSettings\IsDynamicSearchBoxEnabled. Windows blocks value writes to that key at the kernel level, even for an elevated administrator.

Because the SearchHighlightOff step is not marked BestEffort (unlike the adjacent WidgetServiceOff step), this single un-writable cosmetic setting terminates the entire run, so Phases 6–11 (Edge, fonts, Terminal, PowerShell profile, Copilot, WSL) never execute.

Environment

Item	Value
Windows	Windows 11, build 28000 (Microsoft Windows NT 10.0.28000.0)
PowerShell	7.6.6 (Core)
winget	v1.29.380
Setup entry point	irm https://aka.ms/devconfig/full/setup.ps1 | iex
Resolved commit	06200f0819136c528e09533e3c8afac7e5f46ed7 (branch main)
Action	Full
Elevation	Yes — verified IsInRole(Administrator) = True for the running process

Steps to reproduce

1. On Windows 11 build 28000, run irm https://aka.ms/devconfig/full/setup.ps1 | iex from an elevated PowerShell 7 session.
2. Let setup complete Phases 1–4 and the first four steps of Phase 5.

Actual result

Phase 5/11 -- Taskbar, search & start tweaks
  ...
  -> Disable Show search highlights...

Calm OS setup stopped early.
  Windows blocked changing HKCU:\SOFTWARE\Microsoft\Windows\CurrentVersion\SearchSettings\IsDynamicSearchBoxEnabled. Administrator access or Windows policy may restrict this setting.
  (_registry.ps1 line 50)
  Nothing already applied was undone -- running this again picks up where it left off.

The underlying exception is an UnauthorizedAccessException ("Attempted to perform an unauthorized operation./ 未经授权操作") raised by New-ItemProperty at steps/_registry.ps1:48, caught and rethrown with the friendly message at steps/_registry.ps1:50-52.

Re-running simply reproduces the identical failure, so Full can never advance past Phase 5 on this build.

Root cause

Windows on this build protects the SearchSettings key against value writes, independent of ACLs. The key is owned by the user and its ACL grants the user, SYSTEM and Administrators KEY_ALL_ACCESS (KA), with no Deny ACE — yet every value write is refused.

Note the key carries an explicit ACE for a MicrosoftWindows.Client.CBS AppContainer SID (S-1-15-3-1024-1086922356-207614091-3724853071-841836187-4018695103-34218837-3164163255-155871754), which is the search/taskbar package (SearchHost.exe runs from MicrosoftWindows.Client.CBS_cw5n1h2txyewy).

Methods attempted, all failing

Method	Result
New-ItemProperty (PowerShell, elevated)	Access is denied
reg.exe add HKCU\...\SearchSettings /v IsDynamicSearchBoxEnabled /t REG_DWORD /d 0 /f	ERROR: Access is denied.
[Microsoft.Win32.RegistryKey]::SetValue() via OpenSubKey($true)	Attempted to perform an unauthorized operation.
Rewrote the key ACL (removed the AppContainer ACE, granted the current user explicit FullControl)	ACL change succeeded, write still failed
Stopped WSearch service and killed SearchHost.exe	write still failed
Wrote a different, brand-new value name in the same key	failed
Modified an existing value (WebSearchInstalledVersion)	failed
Created a new subkey	succeeded (so it is specifically value writes that are blocked)
Wrote HKLM\SOFTWARE\Policies\Microsoft\Windows\Windows Search	succeeded (proves elevation is fine)
Wrote HKCU\...\Explorer\Advanced	succeeded (proves general HKCU writes are fine)

SearchSettings has no policy mirror on this build (HKLM\SOFTWARE\Policies\Microsoft\Windows\CurrentVersion\SearchSettings does not exist), so there is no supported policy-based way to set this value either.

Expected result

Either of:

1. SearchHighlightOff should be marked BestEffort = $true, like the WidgetServiceOff step in the very same file, so a platform-protected cosmetic setting cannot abort the whole run; or
2. If the value is genuinely un-writable on current builds, the step should be removed or its apply-path changed to a supported API.

Suggested fix

In windows-dev-config/steps/registry-taskbar-search.ps1, the file already acknowledges this exact class of problem for Widgets:

# Windows may protect the Widgets policy even from an administrator.
@{
    Name        = 'WidgetServiceOff'
    KeyPath     = 'HKLM\SOFTWARE\Policies\Microsoft\Dsh'
    ValueName   = 'AllowNewsAndInterests'
    Value       = 0
    Description = 'Disable Widgets'
    BestEffort  = $true
}

The SearchHighlightOff tweak immediately above it has the same exposure but lacks the flag:

@{
    Name        = 'SearchHighlightOff'
    KeyPath     = 'HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\SearchSettings'
    ValueName   = 'IsDynamicSearchBoxEnabled'
    Value       = 0
    Description = 'Disable Show search highlights'
}

Adding BestEffort = $true (or removing the tweak) would let Full continue on builds where Windows protects this key.

Additional notes

• Verified against the current main: steps/registry-taskbar-search.ps1 is byte-identical to the copy setup installed, so the issue is present in the latest code.
• Related prior report: #109 ("Disable Widget service errors on fresh Windows 11 PC") — the same class of failure, which is presumably why WidgetServiceOff was given BestEffort. SearchHighlightOff appears to have been missed.
• No existing issue appears to cover IsDynamicSearchBoxEnabled / SearchSettings specifically.