diff --git a/README.md b/README.md
index adc4052..fd46979 100644
--- a/README.md
+++ b/README.md
@@ -30,7 +30,7 @@ powershell -File tools\Deploy-Remote.ps1 `
   -RunTests
 ```
 
-The controller packages only paths reported by `git ls-files`, so new deployment files must be tracked before using it. `-PullOriginMaster` optionally runs `git pull --ff-only origin master` and refuses a dirty worktree; it is never implicit. The controller reports a SHA-256 digest and the remote installer verifies it before changing the target. The remote preflight also validates the archive, target path, IIS site ownership, app-pool ownership, binding conflicts, and global COM registration ownership. It refuses partial or foreign ProgID/CLSID state rather than overwriting it. It then swaps the complete project tree into place, registers every WSC (including `WscMvc.ViewRenderer`), and reconciles both IIS sites through `Setup-Site.ps1`.
+The controller packages only paths reported by `git ls-files`, so new deployment files must be tracked before using it. `-PullOriginMaster` optionally runs `git pull --ff-only origin master` and refuses a dirty worktree; it is never implicit. The controller reports a SHA-256 digest and the remote installer verifies it before changing the target. The remote preflight also validates the archive, target path, IIS site ownership, app-pool ownership, binding conflicts, and global COM registration ownership. It refuses partial or foreign ProgID/CLSID state rather than overwriting it. It stops only the two project-owned sites/pools, mirrors the current tree to a timestamped rollback directory, mirrors the verified release into the stable live path, registers every WSC (including `WscMvc.ViewRenderer`), and reconciles both IIS sites through `Setup-Site.ps1`.
 
 When replacing an existing project tree, the prior tree is retained as `<RemoteProjectPath>.rollback.<UTC timestamp>-<id>`. If registration, IIS reconciliation, or optional tests fail, the installer restores that tree, re-registers its components, restores pre-existing site run states, and removes only sites/app pools created by that invocation. It refuses to adopt mismatched IIS resources and does not alter unrelated sites, pools, or bindings.
 
diff --git a/docs/TEST-RESULTS.md b/docs/TEST-RESULTS.md
index ecbb839..4e76d57 100644
--- a/docs/TEST-RESULTS.md
+++ b/docs/TEST-RESULTS.md
@@ -419,3 +419,22 @@ curl -o /dev/null -w "%{http_code}" http://localhost:8090/Views/Home.html   -> 4
 `tests/run-self-test.sh http://localhost:8091`: **NOT RUN locally** — this host's local Python is a Microsoft Store execution-alias stub, so the script's `json.tool` pretty-print step cannot run. The same JSON contract was already verified directly (`curl http://localhost:8091/self-test` → `{"ok":true,...}`, all 5 checks passing) and via `Test-Http.ps1` above; this is a convenience-script limitation on this specific host, not a framework regression — matches the pre-existing NOT RUN note for this same script under M3.
 
 M4 gate status: **PASS** for the vertical slice implemented (safe separate template loading from a physically non-served directory; deterministic `{{Key}}` substitution; default HTML-text-context encoding verified against a real escaping case; missing-template and unresolved-placeholder failures verified path-free and safe; `/hello`'s existing exact-body contract verified unchanged end-to-end through IIS). `Views/Layout.html` and a layout convention are deferred (IMPLEMENTATION_PLAN M4 sequences "add layout after renderer works" as a second step) — not yet needed since there is still only one view. Attribute/URL/JS-context encoding remains explicitly out of scope until a view needs it (documented on `ViewRenderer.wsc` and in `docs/ARCHITECTURE.md`).
+
+## Remote deployment tooling — Windows Server 2025 live proof (2026-09-19)
+
+Host under test: `win2025test`, Windows Server 2025 Standard build 26100, 64-bit; production `WscMvc` on `:8090` and test `WscMvcTests` on `:8091`.
+
+Windows PowerShell 5.1 parser checks passed for `tools/Deploy-Remote.ps1`, `tools/Invoke-RemoteInstall.ps1`, and `tests/Invoke-SelfTest.ps1`. The first live JSON-client run exposed and fixed output suppression caused by assigning the function's output to `$null`; after the fix, the client printed every endpoint and embedded check and ended with `RESULT: ALL PASS`.
+
+The first installer cutover attempt verified the archive SHA-256 and completed read-only preflight, then Windows denied renaming the live IIS root even after both dedicated pools reached `Stopped`. The installer failed before modifying the live tree and restored both sites/pools to `Started`; `/hello` and `/self-test` remained HTTP 200. The implementation was changed to keep the live root stable: mirror it to a timestamped rollback directory, then mirror the staged release into the live path with checked `robocopy` exit codes. This avoids depending on a root-directory rename while preserving rollback ownership.
+
+Successful live invocation:
+
+```text
+Invocation: 20260919T215247Z-606dbb12
+Package SHA-256: 8ca5b314a9cb183f1ed9f2497118825658c470eb1237dcb4d53df66931a933f7
+Deployment succeeded: C:\Projects\wsc-mvc
+Timestamped rollback retained at: C:\Projects\wsc-mvc.rollback.20260919T215247Z-606dbb12
+```
+
+Post-cutover results: `tests\Test-Components.vbs` **ALL PASS**; `tests\Test-Http.ps1` **ALL PASS**; `tests\Invoke-SelfTest.ps1` **ALL PASS**, including every JSON-reported check. Both IIS sites and dedicated pools returned to `Started`, and the deployment retained the prior tree for rollback.
diff --git a/tools/Invoke-RemoteInstall.ps1 b/tools/Invoke-RemoteInstall.ps1
index 24a6239..f3d02c0 100644
--- a/tools/Invoke-RemoteInstall.ps1
+++ b/tools/Invoke-RemoteInstall.ps1
@@ -179,6 +179,23 @@ function Wait-WebAppPoolState {
     throw "App pool '$Name' did not reach state '$DesiredState' within $TimeoutSeconds seconds (current: $current)."
 }
 
+function Sync-DirectoryTree {
+    param(
+        [Parameter(Mandatory = $true)][string]$Source,
+        [Parameter(Mandatory = $true)][string]$Destination
+    )
+
+    if (-not (Test-Path -LiteralPath $Source -PathType Container)) {
+        throw "Directory sync source does not exist: $Source"
+    }
+
+    & robocopy.exe $Source $Destination /MIR /COPY:DAT /DCOPY:DAT /R:2 /W:1 /NFL /NDL /NJH /NJS /NP
+    $exitCode = $LASTEXITCODE
+    if ($exitCode -ge 8) {
+        throw "robocopy failed while mirroring '$Source' to '$Destination' (exit code $exitCode)."
+    }
+}
+
 function Restore-PoolState {
     param([string]$Name, [string]$State)
     if (-not $State -or -not (Test-Path "IIS:\AppPools\$Name")) { return }
@@ -282,7 +299,7 @@ $createdProductionSite = -not [bool]$productionSnapshot
 $createdTestSite = -not [bool]$testSnapshot
 $createdProductionPool = -not $productionPoolExisted
 $createdTestPool = -not $testPoolExisted
-$targetMoved = $false
+$targetUpdated = $false
 $backupCreated = $false
 $installSucceeded = $false
 
@@ -317,10 +334,10 @@ try {
         }
     }
 
-    # Stop only this deployment's two sites and dedicated pools before the
-    # same-volume directory renames. WSC/COM files remain locked while their
-    # worker processes are alive. Directory.Move is used instead of Move-Item
-    # so a lock failure cannot partially split a directory tree.
+    # Stop only this deployment's two sites and dedicated pools before copying
+    # the release. The live root itself can remain open on IIS hosts even after
+    # its dedicated pools stop, so keep the path stable and mirror a verified
+    # backup/release tree instead of relying on a root-directory rename.
     foreach ($siteSnapshot in @($productionSnapshot, $testSnapshot)) {
         if ($siteSnapshot -and $siteSnapshot.State -eq 'Started') {
             Stop-Website -Name $siteSnapshot.Name
@@ -335,11 +352,12 @@ try {
     }
 
     if ($targetExisted) {
-        [IO.Directory]::Move($projectFullPath, $backupPath)
+        Sync-DirectoryTree -Source $projectFullPath -Destination $backupPath
         $backupCreated = $true
     }
-    [IO.Directory]::Move($stagingPath, $projectFullPath)
-    $targetMoved = $true
+    Sync-DirectoryTree -Source $stagingPath -Destination $projectFullPath
+    $targetUpdated = $true
+    Remove-Item -LiteralPath $stagingPath -Recurse -Force
 
     & (Join-Path $projectFullPath 'tools\Register-Components.ps1') -ProjectRoot $projectFullPath
     & (Join-Path $projectFullPath 'tools\Setup-Site.ps1') -SiteName $ProductionSiteName -PoolName $ProductionPoolName -PhysicalPath $productionPublicPath -Port $ProductionPort
@@ -371,7 +389,7 @@ try {
     Write-Warning "Deployment failed; rolling back only changes owned by invocation $InvocationId."
 
     try {
-        if ($targetMoved -and (Test-Path -LiteralPath (Join-Path $projectFullPath 'tools\Unregister-Components.ps1'))) {
+        if ($targetUpdated -and (Test-Path -LiteralPath (Join-Path $projectFullPath 'tools\Unregister-Components.ps1'))) {
             & (Join-Path $projectFullPath 'tools\Unregister-Components.ps1') -ProjectRoot $projectFullPath
         }
     } catch { $rollbackErrors.Add("Unregister new components: $($_.Exception.Message)") }
@@ -390,13 +408,15 @@ try {
     } catch { $rollbackErrors.Add("Remove test pool: $($_.Exception.Message)") }
 
     try {
-        if ($targetMoved -and (Test-Path -LiteralPath $projectFullPath)) {
-            [IO.Directory]::Move($projectFullPath, $failedPath)
+        if ($targetUpdated -and (Test-Path -LiteralPath $projectFullPath)) {
+            Sync-DirectoryTree -Source $projectFullPath -Destination $failedPath
         }
     } catch { $rollbackErrors.Add("Retain failed release: $($_.Exception.Message)") }
     try {
         if ($backupCreated -and (Test-Path -LiteralPath $backupPath)) {
-            [IO.Directory]::Move($backupPath, $projectFullPath)
+            Sync-DirectoryTree -Source $backupPath -Destination $projectFullPath
+        } elseif ($targetUpdated -and -not $targetExisted -and (Test-Path -LiteralPath $projectFullPath)) {
+            Remove-Item -LiteralPath $projectFullPath -Recurse -Force
         }
     } catch { $rollbackErrors.Add("Restore previous project tree: $($_.Exception.Message)") }
     try {