diff --git a/Tools/windows/PACKAGING.md b/Tools/windows/PACKAGING.md
index dd85b4e4..b2948799 100644
--- a/Tools/windows/PACKAGING.md
+++ b/Tools/windows/PACKAGING.md
@@ -141,6 +141,9 @@ powershell.exe -NoProfile -File "$env:LOCALAPPDATA\GraphCode\current\GraphCode-S
 ```
 
 Uninstall preserves user data by default; `-RemoveUserData` opts into removal.
+Close GraphCode and end its terminal sessions first: Uninstall refuses, without
+changing anything, while processes run from the installation (see
+[Uninstall with GraphCode still running](#uninstall-with-graphcode-still-running)).
 Authenticate signed setup before uninstall too. Setup never changes PowerShell
 execution policy or certificate stores; organization policy may restrict
 execution. Do not disable that policy to bypass a signature failure.
@@ -180,6 +183,33 @@ native Windows file-sharing lock. It isolates daemon and shortcut operations;
 the real-product packaging gate separately exercises scheduled-daemon
 install/upgrade/rollback/uninstall.
 
+## Uninstall with GraphCode still running
+
+Uninstall removes the installation completely or changes nothing. Before
+touching the daemon, scheduled task, PATH, or shortcut it lists every process
+running from the installation root. Terminal session hosts (`zmx.exe`), the
+shell, and the CLI are the user's live work, so Uninstall never kills them: it
+refuses with exit code 1, names each process and PID, and explains how to end
+the sessions (`<installed>\bin\zmx.exe ls`, then `zmx.exe kill <name>`) and to
+rerun Uninstall from a terminal outside GraphCode. Only the installed daemon is
+stopped automatically, as before.
+
+After stopping the daemon, Uninstall re-checks for processes, confirms that
+every installed file can be opened exclusively, and then renames the whole
+installation root to a sibling `.GraphCode-uninstall-<id>` directory in one
+step. Any failure up to and including the PATH and shortcut removal moves the
+installation back, restores PATH and the shortcut, and restarts the daemon if
+it was running. Only after the integration is gone is the renamed directory
+deleted; if a file is opened in that brief window, Uninstall still succeeds and
+warns with the leftover directory to delete. User data is preserved by default
+in every outcome.
+
+`Packaging.Uninstall.Tests.ps1` reproduces a live session host launched from
+the installed `bin\zmx.exe`, a runtime DLL held open by another process, a
+failed task removal after the rename, and a clean uninstall. It models the
+scheduler and user PATH; the real-product packaging gate exercises the real
+scheduled-daemon uninstall.
+
 ## Signed package integrity
 
 Signing is opt-in: `-SignCertificate <thumbprint>` requires a trusted code-signing
diff --git a/Tools/windows/PackageRuntime.ps1 b/Tools/windows/PackageRuntime.ps1
index eccb1eef..70e614a6 100644
--- a/Tools/windows/PackageRuntime.ps1
+++ b/Tools/windows/PackageRuntime.ps1
@@ -451,12 +451,127 @@ function Install-Package([bool] $upgrade) {
     Close-Package
   }
 }
+function Get-FullInstallRoot {
+  $ExecutionContext.SessionState.Path.GetUnresolvedProviderPathFromPSPath($InstallRoot).TrimEnd("\")
+}
+function Get-InstallRootProcesses {
+  $root = (Get-FullInstallRoot) + "\"
+  @(Get-CimInstance Win32_Process -ErrorAction SilentlyContinue | Where-Object {
+      $_.ExecutablePath -and
+      [IO.Path]::GetFullPath($_.ExecutablePath).StartsWith($root, [StringComparison]::OrdinalIgnoreCase)
+    })
+}
+function Assert-InstallRootIdle([bool] $daemonManaged) {
+  # Session hosts (zmx), the shell, and the CLI are the user's work: refuse rather than kill them.
+  $daemon = Join-Path (Get-FullInstallRoot) "bin\graphcoded.exe"
+  $blocking = @(Get-InstallRootProcesses | Where-Object {
+      -not ($daemonManaged -and [IO.Path]::GetFullPath($_.ExecutablePath) -ieq $daemon)
+    })
+  if ($blocking.Count -eq 0) { return }
+  $summary = @($blocking | Group-Object Name | Sort-Object Name | ForEach-Object {
+      "$($_.Name) (PID $((@($_.Group | ForEach-Object { $_.ProcessId }) | Sort-Object) -join ', '))"
+    }) -join "; "
+  $zmx = Join-Path $InstallRoot "bin\zmx.exe"
+  Fail ("Uninstall changed nothing: $($blocking.Count) GraphCode process(es) are still running from " +
+    "$InstallRoot`: $summary. Close GraphCode, end its terminal sessions (list them with " +
+    "`"$zmx`" ls and stop each with `"$zmx`" kill NAME), then run Uninstall again from a " +
+    "terminal outside GraphCode.")
+}
+function Find-LockedInstallFile([string] $root) {
+  foreach ($file in @(Get-ChildItem -LiteralPath $root -File -Recurse -Force)) {
+    $access = if ($file.IsReadOnly) { [IO.FileAccess]::Read } else { [IO.FileAccess]::ReadWrite }
+    try {
+      # Exclusive opens fail for any open handle and, with write access, for mapped images.
+      $stream = [IO.File]::Open($file.FullName, [IO.FileMode]::Open, $access, [IO.FileShare]::None)
+      $stream.Dispose()
+    } catch {
+      $failure = $_.Exception
+      while ($failure.InnerException) { $failure = $failure.InnerException }
+      return "$($file.FullName) ($($failure.Message))"
+    }
+  }
+  return $null
+}
 function Uninstall-Package {
-  if (-not $NoScheduledTask) { Stop-InstalledDaemon; Remove-DaemonTask }
+  $daemonManaged = -not $NoScheduledTask
+  $installed = Test-Path -LiteralPath $InstallRoot
+  if ($installed) { Assert-InstallRootIdle $daemonManaged }
+  $daemonWasRunning = $false
+  if ($daemonManaged) {
+    $daemonWasRunning = @(Get-InstalledDaemons).Count -gt 0
+    Stop-InstalledDaemon
+  }
   $bin = Join-Path $InstallRoot "bin"
-  Set-UserPath $bin $false
-  Set-Shortcut $false
-  if (Test-Path $InstallRoot) { Remove-Item $InstallRoot -Recurse -Force }
+  $parent = Split-Path (Get-FullInstallRoot) -Parent
+  $removed = $null
+  $shortcutBackup = $null
+  $pathAttempted = $false
+  $shortcutAttempted = $false
+  $oldPath = $null
+  try {
+    if ($installed) {
+      # Re-check after stopping the daemon, then take the whole tree out of service with
+      # one rename so a held file can never leave a half-deleted installation behind.
+      Assert-InstallRootIdle $daemonManaged
+      $locked = Find-LockedInstallFile $InstallRoot
+      if ($locked) {
+        Fail "Uninstall changed nothing: an installed file is in use: $locked. Close the program using it, then run Uninstall again."
+      }
+      $removed = Join-Path $parent ".GraphCode-uninstall-$([guid]::NewGuid())"
+      Move-InstallDirectory $InstallRoot $removed
+    }
+    $shortcutBackup = Join-Path ([IO.Path]::GetTempPath()) "GraphCode-uninstall-shortcut-$([guid]::NewGuid())"
+    New-Item -ItemType Directory -Force -Path $shortcutBackup | Out-Null
+    Save-Shortcut $shortcutBackup
+    $oldPath = [Environment]::GetEnvironmentVariable("Path", "User")
+    if ($daemonManaged) { Remove-DaemonTask }
+    $pathAttempted = $true
+    Set-UserPath $bin $false
+    $shortcutAttempted = $true
+    Set-Shortcut $false
+  } catch {
+    $failure = $_
+    $rollbackErrors = [Collections.Generic.List[string]]::new()
+    $restored = $true
+    if ($removed -and (Test-Path -LiteralPath $removed)) {
+      try { Move-InstallDirectory $removed $InstallRoot } catch {
+        $restored = $false
+        $rollbackErrors.Add("restoring the installation from '$removed': $($_.Exception.Message)")
+      }
+    }
+    if ($pathAttempted) {
+      try { [Environment]::SetEnvironmentVariable("Path", $oldPath, "User") } catch {
+        $rollbackErrors.Add("restoring user PATH: $($_.Exception.Message)")
+      }
+    }
+    $keepShortcutBackup = $false
+    if ($shortcutAttempted) {
+      try { Restore-Shortcut $shortcutBackup } catch {
+        $keepShortcutBackup = $true
+        $rollbackErrors.Add("restoring shortcuts from '$shortcutBackup': $($_.Exception.Message)")
+      }
+    }
+    if ($daemonWasRunning -and $restored) {
+      try { Start-DaemonTask } catch {
+        $rollbackErrors.Add("restarting the daemon: $($_.Exception.Message)")
+      }
+    }
+    if (-not $keepShortcutBackup -and $shortcutBackup -and (Test-Path -LiteralPath $shortcutBackup)) {
+      Remove-Item -LiteralPath $shortcutBackup -Recurse -Force -ErrorAction SilentlyContinue
+    }
+    if ($rollbackErrors.Count) {
+      Fail "Uninstall failed: $($failure.Exception.Message) Rollback incomplete: $($rollbackErrors -join '; ')."
+    }
+    throw $failure
+  }
+  if ($shortcutBackup -and (Test-Path -LiteralPath $shortcutBackup)) {
+    Remove-Item -LiteralPath $shortcutBackup -Recurse -Force -ErrorAction SilentlyContinue
+  }
+  if ($removed) {
+    try { Remove-Item -LiteralPath $removed -Recurse -Force } catch {
+      Write-Warning "GraphCode packaging: GraphCode was uninstalled, but leftover files remain at '$removed': $($_.Exception.Message) Delete that directory after closing the program using it."
+    }
+  }
   $data = Join-Path $env:USERPROFILE ".graphcode"
   if ($RemoveUserData -and -not $KeepUserData) {
     Remove-Item $data -Recurse -Force -ErrorAction SilentlyContinue
diff --git a/Tools/windows/Tests/Packaging.Uninstall.Tests.ps1 b/Tools/windows/Tests/Packaging.Uninstall.Tests.ps1
new file mode 100644
index 00000000..63746aef
--- /dev/null
+++ b/Tools/windows/Tests/Packaging.Uninstall.Tests.ps1
@@ -0,0 +1,156 @@
+[CmdletBinding()]
+param()
+
+# Uninstall must either remove the whole installation or change nothing. The live-session
+# case reproduces the Dev Box D10 failure: a zmx session host launched from the installed
+# bin keeps bin\zmx.exe locked while Uninstall runs.
+$ErrorActionPreference = "Stop"
+$repoRoot = (Resolve-Path (Join-Path $PSScriptRoot "..\..\..")).Path
+$fixture = Join-Path $repoRoot ".build\packaging-uninstall-$([guid]::NewGuid())"
+$tokens = $null
+$errors = $null
+$ast = [Management.Automation.Language.Parser]::ParseFile(
+  (Join-Path $repoRoot "Tools\windows\PackageRuntime.ps1"), [ref]$tokens, [ref]$errors)
+if ($errors.Count) { throw "Packaging script has parse errors: $errors" }
+foreach ($definition in $ast.FindAll({
+      param($node) $node -is [Management.Automation.Language.FunctionDefinitionAst]
+    }, $false)) {
+  . ([scriptblock]::Create($definition.Extent.Text))
+}
+if (-not (Get-Command Uninstall-Package -CommandType Function -ErrorAction SilentlyContinue)) {
+  throw "Packaging helper is missing: Uninstall-Package"
+}
+
+# The machine-wide surfaces (scheduler, registry PATH) are modelled; files, shortcuts and
+# processes are real and live under the fixture.
+function Get-InstalledDaemons {
+  if ($state.daemon) { @([pscustomobject]@{ ProcessId = 0 }) } else { @() }
+}
+function Stop-InstalledDaemon { $state.stops++; $state.daemon = $false }
+function Test-DaemonTask([string] $name) { $state.task }
+function Remove-DaemonTask {
+  if ($case -eq "task-removal-failure") { throw "injected task removal failure" }
+  $state.task = $false
+}
+function Start-DaemonTask { $state.starts++; $state.task = $true; $state.daemon = $true }
+function Set-UserPath([string] $bin, [bool] $add) { $state.path = $add }
+
+function Assert([bool] $condition, [string] $message) {
+  if (-not $condition) { throw "$case`: $message" }
+}
+function Get-TreeDigest([string] $root) {
+  @(Get-ChildItem -LiteralPath $root -File -Recurse -Force | Sort-Object FullName | ForEach-Object {
+      "$($_.FullName.Substring($root.Length))=$((Get-FileHash -LiteralPath $_.FullName -Algorithm SHA256).Hash)"
+    }) -join "`n"
+}
+
+$oldProfile = $env:USERPROFILE
+$oldAppData = $env:APPDATA
+$NoScheduledTask = $false
+$RemoveUserData = $false
+$KeepUserData = $false
+$failures = [Collections.Generic.List[string]]::new()
+$executed = 0
+try {
+  foreach ($case in @("live-session", "locked-file", "task-removal-failure", "success")) {
+    $session = $null
+    $lock = $null
+    try {
+      $caseRoot = Join-Path $fixture $case
+      $InstallRoot = Join-Path $caseRoot "GraphCode\current"
+      $env:USERPROFILE = Join-Path $caseRoot "user"
+      $env:APPDATA = Join-Path $env:USERPROFILE "AppData\Roaming"
+      $bin = Join-Path $InstallRoot "bin"
+      New-Item -ItemType Directory -Force -Path $bin, (Join-Path $InstallRoot "licenses") | Out-Null
+      Copy-Item (Join-Path $env:SystemRoot "System32\PING.EXE") (Join-Path $bin "zmx.exe")
+      foreach ($name in @("graphcoded.exe", "graphcode.exe", "graphcode-windows.exe", "_FoundationICU.dll")) {
+        Set-Content (Join-Path $bin $name) "payload $name"
+      }
+      foreach ($name in @("GraphCode-Setup.ps1", "manifest.json", "metadata.json", "licenses\ZMX-LICENSE.txt")) {
+        Set-Content (Join-Path $InstallRoot $name) "payload $name"
+      }
+      $shortcut = Join-Path $env:APPDATA "Microsoft\Windows\Start Menu\Programs\GraphCode.lnk"
+      New-Item -ItemType Directory -Force -Path (Split-Path $shortcut -Parent) | Out-Null
+      Set-Content $shortcut "installed shortcut"
+      $userData = Join-Path $env:USERPROFILE ".graphcode\graph.json"
+      New-Item -ItemType Directory -Force -Path (Split-Path $userData -Parent) | Out-Null
+      Set-Content $userData '{"projects":["kept"]}'
+      $installBefore = Get-TreeDigest $InstallRoot
+      $dataBefore = Get-TreeDigest (Split-Path $userData -Parent)
+      $state = @{ daemon = $true; task = $true; path = $true; stops = 0; starts = 0 }
+
+      if ($case -eq "live-session") {
+        $session = Start-Process -FilePath (Join-Path $bin "zmx.exe") -ArgumentList "-n", "120", "127.0.0.1" `
+          -WindowStyle Hidden -PassThru
+        $deadline = [DateTime]::UtcNow.AddSeconds(10)
+        while (-not (Get-CimInstance Win32_Process -Filter "ProcessId=$($session.Id)" -ErrorAction SilentlyContinue) -and
+          [DateTime]::UtcNow -lt $deadline) { Start-Sleep -Milliseconds 100 }
+        Assert (-not $session.HasExited) "the fixture session host did not start"
+      }
+      if ($case -eq "locked-file") {
+        # A runtime DLL held open by a process that is not itself launched from the install root.
+        $lock = [IO.File]::Open((Join-Path $bin "_FoundationICU.dll"),
+          [IO.FileMode]::Open, [IO.FileAccess]::Read, [IO.FileShare]::Read)
+      }
+
+      $errorMessage = $null
+      $output = $null
+      try { $output = Uninstall-Package *>&1 | Out-String } catch { $errorMessage = $_.Exception.Message }
+      $debris = @(Get-ChildItem -LiteralPath (Split-Path $InstallRoot -Parent) -Force -Directory |
+        Where-Object { $_.Name -ne "current" })
+      Assert ($debris.Count -eq 0) "left transaction debris: $($debris.Name -join ', ')"
+      Assert ((Get-TreeDigest (Split-Path $userData -Parent)) -ceq $dataBefore) "changed preserved user data"
+
+      if ($case -eq "success") {
+        Assert (-not $errorMessage) "failed: $errorMessage"
+        Assert (-not (Test-Path -LiteralPath $InstallRoot)) "left the installation behind"
+        Assert (-not $state.task -and -not $state.daemon -and -not $state.path) "left daemon, task or PATH integration"
+        Assert (-not (Test-Path -LiteralPath $shortcut)) "left the Start-menu shortcut"
+        Assert ($output -match "User data preserved") "did not report preserved user data: $output"
+        $executed++
+        continue
+      }
+
+      Assert ([bool] $errorMessage) "succeeded although the installation could not be removed"
+      Assert ((Test-Path -LiteralPath $InstallRoot) -and (Get-TreeDigest $InstallRoot) -ceq $installBefore) `
+        "left a partial installation: $errorMessage"
+      Assert ($state.task -and $state.path) "removed the task or PATH entry before failing: $errorMessage"
+      Assert ((Test-Path -LiteralPath $shortcut) -and (Get-Content $shortcut) -eq "installed shortcut") `
+        "removed the Start-menu shortcut before failing: $errorMessage"
+      Assert $state.daemon "left the daemon stopped after refusing: $errorMessage"
+      switch ($case) {
+        "live-session" {
+          Assert ($errorMessage -match "changed nothing" -and $errorMessage -match "zmx\.exe" -and
+            $errorMessage -match "PID $($session.Id)\b" -and $errorMessage -match " kill ") `
+            "did not name the running session host with an actionable fix: $errorMessage"
+          Assert ($state.stops -eq 0) "stopped the daemon before refusing up front"
+          Assert (-not $session.HasExited) "killed the user's live session host"
+        }
+        "locked-file" {
+          Assert ($errorMessage -match "changed nothing" -and $errorMessage -match "_FoundationICU\.dll") `
+            "did not name the file in use: $errorMessage"
+          Assert ($state.starts -eq 1) "did not restart the daemon it stopped"
+        }
+        "task-removal-failure" {
+          Assert ($errorMessage -match "injected task removal failure") "lost the initiating failure: $errorMessage"
+          Assert ($state.starts -eq 1) "did not restart the daemon it stopped"
+        }
+      }
+      $executed++
+    } catch {
+      $failures.Add("$_")
+    } finally {
+      if ($lock) { $lock.Dispose() }
+      if ($session -and -not $session.HasExited) { $session.Kill(); $session.WaitForExit() }
+    }
+  }
+  if ($failures.Count) { throw "RED: Uninstall lifecycle contract failed:`n$($failures -join "`n")" }
+  if ($executed -ne 4) { throw "Uninstall lifecycle contract executed $executed of 4 cases" }
+  Write-Output "Uninstall live-session refusal and all-or-nothing removal contracts (4 cases): PASS"
+} finally {
+  $env:USERPROFILE = $oldProfile
+  $env:APPDATA = $oldAppData
+  if (Test-Path -LiteralPath $fixture) {
+    Remove-Item -LiteralPath $fixture -Recurse -Force -ErrorAction SilentlyContinue
+  }
+}
diff --git a/Tools/windows/Tests/ValidationRunner.Tests.ps1 b/Tools/windows/Tests/ValidationRunner.Tests.ps1
index b1bb6207..3e9127a2 100644
--- a/Tools/windows/Tests/ValidationRunner.Tests.ps1
+++ b/Tools/windows/Tests/ValidationRunner.Tests.ps1
@@ -3051,7 +3051,7 @@ try {
   if ($runnerSource -notmatch '(?s)"packaging" \{\s*if \(\$PackagingPart -ne "real"\) \{\s*& .*?Packaging\.Standalone\.Tests\.ps1.*?Packaging\.Tests\.ps1') {
     throw "RED: packaging validation does not run standalone setup contracts"
   }
-  foreach ($contract in @("Packaging.ScriptSigning.Tests.ps1", "Packaging.Scheduler.Tests.ps1")) {
+  foreach ($contract in @("Packaging.ScriptSigning.Tests.ps1", "Packaging.Scheduler.Tests.ps1", "Packaging.Uninstall.Tests.ps1")) {
     if ($runnerSource -notmatch ('(?s)"packaging" \{\s*if \(\$PackagingPart -ne "real"\) \{\s*& .*?' + [regex]::Escape($contract) + '.*?Packaging\.Tests\.ps1')) {
       throw "RED: packaging validation does not run $contract"
     }
diff --git a/Tools/windows/validate.ps1 b/Tools/windows/validate.ps1
index 5432272d..3bc5d31b 100644
--- a/Tools/windows/validate.ps1
+++ b/Tools/windows/validate.ps1
@@ -1299,6 +1299,7 @@ function Invoke-Task([string] $name) {
         & (Join-Path $repoRoot "Tools\windows\Tests\Packaging.ScriptSigning.Tests.ps1")
         & (Join-Path $repoRoot "Tools\windows\Tests\Packaging.Scheduler.Tests.ps1")
         & (Join-Path $repoRoot "Tools\windows\Tests\Packaging.Rollback.Tests.ps1")
+        & (Join-Path $repoRoot "Tools\windows\Tests\Packaging.Uninstall.Tests.ps1")
         & (Join-Path $repoRoot "Tools\windows\Tests\Packaging.Standalone.Tests.ps1")
       }
       if ($PackagingPart -ne "contracts") {
diff --git a/Tools/windows/validation-matrix.md b/Tools/windows/validation-matrix.md
index 091f66bf..22270fc7 100644
--- a/Tools/windows/validation-matrix.md
+++ b/Tools/windows/validation-matrix.md
@@ -20,6 +20,7 @@ The Windows port must have runnable commands before implementation fleets begin.
 | Native SignTool PS1 signature and tamper detection (SDK required) | `pwsh Tools\windows\Tests\Packaging.ScriptSigning.Tests.ps1` |
 | Native missing/idle task stop and deletion | `pwsh Tools\windows\Tests\Packaging.Scheduler.Tests.ps1` |
 | Failed-upgrade preservation and recoverable rollback | `pwsh Tools\windows\Tests\Packaging.Rollback.Tests.ps1` |
+| Uninstall refusal with live sessions/locked files and all-or-nothing removal | `pwsh Tools\windows\Tests\Packaging.Uninstall.Tests.ps1` |
 | Standalone setup under PowerShell 5.1 and 7 | `pwsh Tools\windows\Tests\Packaging.Standalone.Tests.ps1` |
 | Release publishing: signing gates, asset labeling, workflow contract | `pwsh Tools\windows\Tests\Release.Tests.ps1` |
 | Product/investigation provider pin consistency | `pwsh Tools\windows\Tests\ProviderPins.Tests.ps1` |