windows/welcome/src/SilverOS.Welcome.Core/Apply/AccountService.cs

@@ -6,13 +6,20 @@ public sealed class AccountService(IProcessRunner runner) : IAccountService
         // Daily account = Standard User (Users group only — NOT Administrators).
         await Ps($"$p=ConvertTo-SecureString '{Esc(password)}' -AsPlainText -Force; " +
                  $"New-LocalUser -Name '{Esc(user)}' -Password $p -FullName '{Esc(user)}' -AccountNeverExpires; " +
-                 $"Add-LocalGroupMember -Group 'Users' -Member '{Esc(user)}'", ct);
+                 $"Add-LocalGroupMember -Group 'Users' -Member '{Esc(user)}'", "Daily account creation", ct);
         // Separate elevation account.
         await Ps($"$a=ConvertTo-SecureString '{Esc(adminPassword)}' -AsPlainText -Force; " +
                  $"New-LocalUser -Name 'SilverOS Admin' -Password $a -AccountNeverExpires; " +
-                 $"Add-LocalGroupMember -Group 'Administrators' -Member 'SilverOS Admin'", ct);
+                 $"Add-LocalGroupMember -Group 'Administrators' -Member 'SilverOS Admin'", "Admin account creation", ct);
+    }
+
+    // $ErrorActionPreference='Stop' turns the (otherwise non-terminating) cmdlet errors into a
+    // non-zero exit so EnsureSuccess can surface them instead of silently continuing.
+    private async Task Ps(string script, string operation, CancellationToken ct)
+    {
+        var r = await runner.RunAsync("powershell.exe",
+            $"-NoProfile -ExecutionPolicy Bypass -Command \"$ErrorActionPreference='Stop'; {script}\"", ct);
+        r.EnsureSuccess(operation);
     }
-    private Task Ps(string script, CancellationToken ct) =>
-        runner.RunAsync("powershell.exe", $"-NoProfile -ExecutionPolicy Bypass -Command \"{script}\"", ct);
     private static string Esc(string s) => s.Replace("'", "''");
 }

windows/welcome/src/SilverOS.Welcome.Core/Apply/BitLockerService.cs

@@ -1,7 +1,7 @@
 namespace SilverOS.Welcome.Core.Apply;
 public sealed class BitLockerService(IProcessRunner runner) : IBitLockerService
 {
-    public Task EnableAsync(string pin, CancellationToken ct = default)
+    public async Task EnableAsync(string pin, CancellationToken ct = default)
     {
         var p = pin.Replace("'", "''");
 
@@ -32,9 +32,15 @@ public sealed class BitLockerService(IProcessRunner runner) : IBitLockerService
             "$kp=(Get-BitLockerVolume -MountPoint $mp).KeyProtector; ",
             "if ($kp | Where-Object { $_.KeyProtectorType -eq 'TpmPin' }) { ",
             "$kp | Where-Object { $_.KeyProtectorType -eq 'Tpm' } | ForEach-Object { ",
-            "Remove-BitLockerKeyProtector -MountPoint $mp -KeyProtectorId $_.KeyProtectorId | Out-Null } }");
+            "Remove-BitLockerKeyProtector -MountPoint $mp -KeyProtectorId $_.KeyProtectorId | Out-Null } }; ",
+            // Outcome check: fail loudly (non-zero exit) if a TPM+PIN protector is not present at
+            // the end — this is what actually matters (a benign non-terminating warning alone
+            // must not pass, and a real failure must not stay silent).
+            "$ok=(Get-BitLockerVolume -MountPoint $mp).KeyProtector | Where-Object { $_.KeyProtectorType -eq 'TpmPin' }; ",
+            "if (-not $ok) { Write-Error 'TPM+PIN protector not present after enrollment'; exit 1 }");
 
-        return runner.RunAsync("powershell.exe",
+        var r = await runner.RunAsync("powershell.exe",
             $"-NoProfile -ExecutionPolicy Bypass -Command \"{script}\"", ct);
+        r.EnsureSuccess("BitLocker enrollment");
     }
 }

windows/welcome/src/SilverOS.Welcome.Core/Apply/BootstrapService.cs

@@ -4,12 +4,21 @@ public sealed class BootstrapService(IProcessRunner runner) : IBootstrapService
     public async Task TearDownAsync(string bootstrapUser, CancellationToken ct = default)
     {
         const string key = "'HKLM:\\SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Winlogon'";
+        // DefaultPassword may legitimately be absent → keep its per-cmdlet -EA SilentlyContinue.
         await Ps($"Set-ItemProperty {key} -Name AutoAdminLogon -Value 0; " +
-                 $"Remove-ItemProperty {key} -Name DefaultPassword -EA SilentlyContinue", ct);
+                 $"Remove-ItemProperty {key} -Name DefaultPassword -EA SilentlyContinue", "Disable auto-logon", ct);
         var u = Esc(bootstrapUser);
-        await Ps($"Remove-LocalUser -Name '{u}' -EA SilentlyContinue", ct);
+        await Ps($"Remove-LocalUser -Name '{u}' -EA SilentlyContinue", "Remove bootstrap account", ct);
     }
     private static string Esc(string s) => s.Replace("'", "''");
-    private Task Ps(string s, CancellationToken ct) =>
-        runner.RunAsync("powershell.exe", $"-NoProfile -ExecutionPolicy Bypass -Command \"{s}\"", ct);
+
+    // $ErrorActionPreference='Stop' surfaces unexpected hard errors (e.g. a bad registry path);
+    // the intentional per-cmdlet -EA SilentlyContinue above still overrides it for the known
+    // best-effort cleanups.
+    private async Task Ps(string s, string operation, CancellationToken ct)
+    {
+        var r = await runner.RunAsync("powershell.exe",
+            $"-NoProfile -ExecutionPolicy Bypass -Command \"$ErrorActionPreference='Stop'; {s}\"", ct);
+        r.EnsureSuccess(operation);
+    }
 }

windows/welcome/src/SilverOS.Welcome.Core/Apply/ProcessResultExtensions.cs

@@ -0,0 +1,20 @@
+namespace SilverOS.Welcome.Core.Apply;
+
+internal static class ProcessResultExtensions
+{
+    /// <summary>
+    /// Throws an <see cref="InvalidOperationException"/> with a scrubbed message when the
+    /// process exited non-zero, so a failed privileged step surfaces to the wizard (and a
+    /// failed apply does not proceed to bootstrap teardown) instead of failing silently.
+    /// </summary>
+    public static void EnsureSuccess(in this ProcessResult result, string operation)
+    {
+        if (result.ExitCode == 0) return;
+        var firstLine = (result.StdErr ?? string.Empty)
+            .Split('\n')
+            .Select(l => l.Trim())
+            .FirstOrDefault(l => l.Length > 0) ?? string.Empty;
+        if (firstLine.Length > 200) firstLine = firstLine[..200];
+        throw new InvalidOperationException($"{operation} failed (exit {result.ExitCode}): {firstLine}");
+    }
+}

windows/welcome/tests/SilverOS.Welcome.Tests/ApplyServicesTests.cs

@@ -11,6 +11,35 @@ public class ApplyServicesTests
         return m;
     }
 
+    private static Mock<IProcessRunner> Fail()
+    {
+        var m = new Mock<IProcessRunner>();
+        m.Setup(r => r.RunAsync(It.IsAny<string>(), It.IsAny<string>(), It.IsAny<CancellationToken>()))
+         .ReturnsAsync(new ProcessResult(1, "", "the operation failed"));
+        return m;
+    }
+
+    [Fact]
+    public async Task AccountService_throws_on_nonzero_exit()
+    {
+        await Assert.ThrowsAsync<InvalidOperationException>(() =>
+            new AccountService(Fail().Object).CreateAccountsAsync("alice", "pw", "apw"));
+    }
+
+    [Fact]
+    public async Task BitLockerService_throws_on_nonzero_exit()
+    {
+        await Assert.ThrowsAsync<InvalidOperationException>(() =>
+            new BitLockerService(Fail().Object).EnableAsync("123456"));
+    }
+
+    [Fact]
+    public async Task BootstrapService_throws_on_nonzero_exit()
+    {
+        await Assert.ThrowsAsync<InvalidOperationException>(() =>
+            new BootstrapService(Fail().Object).TearDownAsync("sm-bootstrap"));
+    }
+
     [Fact]
     public async Task AccountService_creates_standard_daily_and_admin()
     {