diff --git a/src/OpenClaw.SetupEngine/SetupContext.cs b/src/OpenClaw.SetupEngine/SetupContext.cs
index 5c5f5ef05..32b1118bc 100644
--- a/src/OpenClaw.SetupEngine/SetupContext.cs
+++ b/src/OpenClaw.SetupEngine/SetupContext.cs
@@ -173,7 +173,7 @@ public sealed class LocalAiConfig
 public sealed class WslConfig
 {
     private static readonly System.Text.RegularExpressions.Regex s_linuxUserNamePattern =
-        new("^[a-z_][a-z0-9_-]{0,31}$", System.Text.RegularExpressions.RegexOptions.Compiled);
+        new(@"\A[a-z_][a-z0-9_-]{0,31}\z", System.Text.RegularExpressions.RegexOptions.Compiled);
 
     public string User { get; set; } = "openclaw";
     public bool Systemd { get; set; } = true;
@@ -185,8 +185,9 @@ public sealed class WslConfig
     public string? Memory { get; set; }
     public string? Swap { get; set; }
 
-    public static bool IsValidLinuxUserName(string value)
-        => s_linuxUserNamePattern.IsMatch(value);
+    public static bool IsValidLinuxUserName(string? value)
+        => !string.IsNullOrWhiteSpace(value)
+            && s_linuxUserNamePattern.IsMatch(value);
 }
 
 // ─── Gateway Configuration ───
diff --git a/src/OpenClaw.SetupEngine/SetupWizardRunner.cs b/src/OpenClaw.SetupEngine/SetupWizardRunner.cs
index c7ecc7bb8..44fbcdcd9 100644
--- a/src/OpenClaw.SetupEngine/SetupWizardRunner.cs
+++ b/src/OpenClaw.SetupEngine/SetupWizardRunner.cs
@@ -120,6 +120,10 @@ internal static bool ShouldReplaceOperatorDeviceId(
 
     internal async Task<StepResult> SuspendReloadModeAsync()
     {
+        var invalidUser = RejectInvalidLinuxUser();
+        if (invalidUser is not null)
+            return invalidUser;
+
         try
         {
             // PATH prefix references $PATH. Pipe the script so wsl.exe cannot expand it on argv.
@@ -128,6 +132,7 @@ internal async Task<StepResult> SuspendReloadModeAsync()
                 $"{_ctx.WslPathPrefix} && openclaw config set gateway.reload.mode off",
                 TimeSpan.FromSeconds(15),
                 // This bounded handoff must finish so we know whether restoration is required.
+                // Stdin keeps the username and $PATH out of the wsl.exe argument vector.
                 ct: CancellationToken.None,
                 inputViaStdin: true);
             if (result.ExitCode != 0)
@@ -154,6 +159,10 @@ internal async Task<StepResult> SuspendReloadModeAsync()
 
     private async Task<StepResult> RunCoreAsync(CancellationToken ct)
     {
+        var invalidUser = RejectInvalidLinuxUser();
+        if (invalidUser is not null)
+            return invalidUser;
+
         var registry = new GatewayRegistry(_ctx.DataDir, logger: new SetupOpenClawLogger(_ctx.Logger));
         registry.Load();
 
@@ -645,6 +654,10 @@ private async Task TryCancelWizardAsync(OpenClawGatewayClient client, string ses
 
     internal async Task<StepResult> RestoreReloadModeAsync()
     {
+        var invalidUser = RejectInvalidLinuxUser();
+        if (invalidUser is not null)
+            return invalidUser;
+
         var reloadMode = ConfigureGatewayStep.GetEffectiveReloadMode(_ctx.Config.Gateway);
         try
         {
@@ -823,6 +836,16 @@ private async Task<CommandResult> RunReloadModeRestorationCommandAsync(string re
         }
     }
 
+    private StepResult? RejectInvalidLinuxUser()
+    {
+        var user = _ctx.Config.Wsl.User;
+        if (WslConfig.IsValidLinuxUserName(user))
+            return null;
+
+        return StepResult.Terminal(
+            $"Invalid WSL user '{user}'. Use a Linux username matching [a-z_][a-z0-9_-]{{0,31}}.");
+    }
+
     internal static bool IsStartupMigrationLeaseContention(CommandResult result) =>
         !result.TimedOut && result.ExitCode != 0
         && (result.Stdout.Contains(StartupMigrationLeaseDiagnostic, StringComparison.Ordinal)
diff --git a/tests/OpenClaw.SetupEngine.Tests/SetupStepsTests.cs b/tests/OpenClaw.SetupEngine.Tests/SetupStepsTests.cs
index 00bfe8659..df32cf4bc 100644
--- a/tests/OpenClaw.SetupEngine.Tests/SetupStepsTests.cs
+++ b/tests/OpenClaw.SetupEngine.Tests/SetupStepsTests.cs
@@ -4014,6 +4014,7 @@ private static int GetFreeTcpPort()
     [InlineData("BadUser")]
     [InlineData("bad user")]
     [InlineData("bad$user")]
+    [InlineData("openclaw\n")]
     public async Task ConfigureWsl_RejectsInvalidLinuxUserName(string user)
     {
         var ctx = CreateContext();
@@ -4361,6 +4362,35 @@ var value when value.Contains("curl -s") => Ok("200"),
             "config set gateway.reload.mode off",
             commands.WslCalls[0].Command);
         Assert.Contains("curl -s", commands.WslCalls[1].Command);
+        Assert.True(commands.WslCalls[0].InputViaStdin);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("bad\"user")]
+    [InlineData("bad$(id)")]
+    [InlineData("openclaw\n")]
+    public async Task SetupWizard_RejectsInvalidLinuxUserBeforeAnyWslCommand(string? user)
+    {
+        var commands = new FakeCommandRunner(
+            _ => Ok(),
+            (_, _, _) => Fail("WSL must not run for an invalid Linux user"));
+        var ctx = CreateContext(
+            new SetupConfig { Wsl = new WslConfig { User = user! } },
+            commands);
+        ctx.DistroName = "test-distro";
+
+        var suspend = await new SetupWizardRunner(ctx).SuspendReloadModeAsync();
+        var restore = await new SetupWizardRunner(ctx).RestoreReloadModeAsync();
+        var run = await new SetupWizardRunner(ctx).RunAsync(CancellationToken.None);
+
+        Assert.Equal(StepOutcome.FailedTerminal, suspend.Outcome);
+        Assert.Equal(StepOutcome.FailedTerminal, restore.Outcome);
+        Assert.Equal(StepOutcome.FailedTerminal, run.Outcome);
+        Assert.Contains("Invalid WSL user", run.Message);
+        Assert.Contains("Invalid WSL user", suspend.Message);
+        Assert.Contains("Invalid WSL user", restore.Message);
+        Assert.Empty(commands.WslCalls);
     }
 
     [Fact]
@@ -7147,7 +7177,8 @@ private static void AssertReloadRestorationCompleted(
     {
         Assert.Contains(
             commands.WslCalls,
-            call => call.Command.Contains("config set gateway.reload.mode 'hybrid'"));
+            call => call.Command.Contains("config set gateway.reload.mode 'hybrid'")
+                && call.InputViaStdin);
         Assert.Contains(
             commands.WslCalls,
             call => call.Command.Contains("openclaw gateway restart"));