diff --git a/code-reviews/Server/findings.md b/code-reviews/Server/findings.md
index 5087c06..4083d7b 100644
--- a/code-reviews/Server/findings.md
+++ b/code-reviews/Server/findings.md
@@ -7,7 +7,7 @@
 | Review date | 2026-05-18 |
 | Commit reviewed | `6c64030` |
 | Status | Reviewed |
-| Open findings | 12 |
+| Open findings | 8 |
 
 ## Checklist coverage
 
@@ -48,13 +48,13 @@
 | Severity | Medium |
 | Category | Design-document adherence |
 | Location | `src/MxGateway.Server/Program.cs:24`, `src/MxGateway.Server/GatewayApplication.cs` |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** `gateway.md:583` and CLAUDE.md state the first version "terminates orphaned workers on startup." No code in MxGateway.Server enumerates or kills leftover `MxGateway.Worker.exe` processes at startup — a grep for `orphan`/`reattach`/`terminate` finds nothing. After an unclean gateway crash, x86 worker processes (each holding an MXAccess COM instance) leak and survive indefinitely, and a restarted gateway does not reclaim or kill them.
 
 **Recommendation:** Add a startup hosted service that finds and kills stale worker processes (by executable path / a well-known argument or environment marker) before the server accepts sessions, or update the design docs if reattachment/cleanup is deliberately deferred.
 
-**Resolution:** _(open)_
+**Resolution:** Resolved 2026-05-18. Confirmed against source: no code path enumerated or killed leftover workers. Added `IRunningProcessInspector` / `SystemRunningProcessInspector` (a testable seam over `Process.GetProcessesByName`/`Kill`), `OrphanWorkerTerminator` (kills processes matched by the configured worker executable path, or by image name when the x64 gateway cannot introspect the x86 worker's `MainModule`, skipping the current process and tolerating per-process kill failures), and `OrphanWorkerCleanupHostedService` (best-effort `IHostedService`). The hosted service is registered in `AddWorkerProcessLauncher` ahead of `AddGatewaySessions` so cleanup runs before the server accepts sessions. `gateway.md` updated to describe the implemented behavior. Regression tests: `OrphanWorkerTerminatorTests` (`KillsWorkerProcessesMatchingConfiguredExecutablePath`, `KillsImageNameMatchWhenExecutablePathUnreadable`, `DoesNotKillUnrelatedProcessSharingImageName`, `DoesNotKillCurrentProcess`, `ContinuesWhenOneKillThrows`).
 
 ### Server-003
 
@@ -78,13 +78,13 @@
 | Severity | Medium |
 | Category | Code organization & conventions |
 | Location | `src/MxGateway.Server/Security/Authentication/ApiKeyAdminCommandLineParser.cs:227-233`, `src/MxGateway.Server/Security/Authentication/ApiKeyAdminCliRunner.cs:53-77`, `src/MxGateway.Server/Dashboard/DashboardApiKeyManagementService.cs:21-67` |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** `ParseScopes` accepts any comma-separated strings and `CreateKeyAsync` persists them verbatim; neither the CLI nor the dashboard create path validates scopes against `GatewayScopes`. A typo or non-canonical name (e.g. CLAUDE.md's example `--scopes session,invoke,event,metadata,admin`, which does not match the resolver's `session:open`/`invoke:read`/etc.) silently creates a key whose scope strings the authorization resolver never checks for — the key is unusable for those RPCs with no error at creation time.
 
 **Recommendation:** Validate every requested scope against the `GatewayScopes` catalog at create time in both the CLI parser/runner and `DashboardApiKeyManagementService.ValidateCreateRequest`, rejecting unknown scope strings.
 
-**Resolution:** _(open)_
+**Resolution:** Resolved 2026-05-18. Confirmed against source: `ParseScopes` split unvalidated strings into the create command and `ValidateCreateRequest` checked only key id and display name. Added `GatewayScopes.All` (the canonical scope catalog) and `GatewayScopes.IsKnown(string)`. `ApiKeyAdminCommandLineParser.Parse` now runs `ValidateScopes` for create-key commands and fails the parse listing the unknown scope(s) and valid set; `DashboardApiKeyManagementService.ValidateCreateRequest` rejects requests carrying any non-canonical scope. Revoke/rotate paths are unaffected (no scope input). Regression tests: `ApiKeyAdminCommandLineParserTests.Parse_CreateKeyCommand_RejectsUnknownScope`, `Parse_CreateKeyCommand_AcceptsAllCanonicalScopes`, and `DashboardApiKeyManagementServiceTests.CreateAsync_UnknownScope_DoesNotCallStore`.
 
 ### Server-005
 
@@ -93,13 +93,13 @@
 | Severity | Medium |
 | Category | Error handling & resilience |
 | Location | `src/MxGateway.Server/Galaxy/GalaxyHierarchyRefreshService.cs:22-28`, `src/MxGateway.Server/Galaxy/GalaxyHierarchyCache.cs:184` |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** `GalaxyHierarchyCache.RefreshCoreAsync` only catches `SqlException` and `InvalidOperationException`. The initial `cache.RefreshAsync` call in `GalaxyHierarchyRefreshService.ExecuteAsync` is wrapped only for `OperationCanceledException`. A transient non-`SqlException` failure on the first refresh (e.g. a `Win32Exception`/`TimeoutException` from connection establishment, or another `DbException` subtype) escapes both layers, faults the `BackgroundService`, and — with default host behavior — stops the whole gateway. The periodic-tick loop does catch general exceptions, so only the first load is exposed.
 
 **Recommendation:** Broaden the `catch` in `RefreshCoreAsync` to all non-cancellation exceptions (record `Unavailable`/`Stale` and still complete `_firstLoad`), or wrap the initial `RefreshAsync` in `GalaxyHierarchyRefreshService` with the same general `catch` the tick loop uses.
 
-**Resolution:** _(open)_
+**Resolution:** Resolved 2026-05-18. Confirmed against source: the initial `RefreshAsync` in `ExecuteAsync` was guarded only for `OperationCanceledException`, and `RefreshCoreAsync` filtered its catch to `SqlException or InvalidOperationException`. Both recommended layers applied: `GalaxyHierarchyRefreshService.ExecuteAsync` now catches every non-cancellation exception on the initial load (logs a warning; the periodic tick retries), and `GalaxyHierarchyCache.RefreshCoreAsync` broadens its catch to all non-cancellation exceptions so the cache still records `Stale`/`Unavailable` and completes `_firstLoad`. The now-unused `Microsoft.Data.SqlClient` using was removed. Regression test: `GalaxyHierarchyRefreshServiceTests.ExecuteAsync_WhenFirstRefreshThrowsNonCancellationException_DoesNotFaultBackgroundService`.
 
 ### Server-006
 
@@ -108,13 +108,13 @@
 | Severity | Medium |
 | Category | Correctness & logic bugs |
 | Location | `src/MxGateway.Server/Sessions/SessionManager.cs:84-114` |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** In `OpenSessionAsync`, `_metrics.SessionOpened()` (line 89) increments the `_openSessions` gauge before `TryAutoSubscribeAlarmsAsync` runs. If auto-subscribe throws (which it does when `Alarms.RequireSubscribeOnOpen` is true and the worker rejects the subscription), the `catch` block disposes and removes the session and records `_metrics.Fault(...)` but never calls `SessionClosed`/`SessionRemoved`. The `mxgateway.sessions.open` gauge permanently over-counts by one for every such failed open.
 
 **Recommendation:** In the `catch` block, when the session had reached the point where `SessionOpened()` was recorded, also call `_metrics.SessionRemoved()` — or move the `SessionOpened()` call to after auto-subscribe succeeds.
 
-**Resolution:** _(open)_
+**Resolution:** Resolved 2026-05-18. Confirmed against source: the `catch` block in `OpenSessionAsync` recorded `Fault(...)` and removed the session but never decremented the open-session gauge after `SessionOpened()` had run. Added a `sessionOpenedRecorded` flag set immediately after `_metrics.SessionOpened()`; the `catch` block now calls `_metrics.SessionRemoved()` when that flag is set, restoring the gauge for a post-`SessionOpened()` failure (e.g. an auto-subscribe rejection with `RequireSubscribeOnOpen=true`). Regression test: `SessionManagerAlarmAutoSubscribeTests.OpenSessionAsync_DoesNotLeakOpenSessionGauge_WhenAutoSubscribeFailsWithRequireOn`.
 
 ### Server-007
 
diff --git a/gateway.md b/gateway.md
index 931e0ee..a22300c 100644
--- a/gateway.md
+++ b/gateway.md
@@ -579,8 +579,11 @@ Policy:
 - command exceptions return structured command fault with HRESULT if known,
 - stale sessions are closed by lease timeout,
 - stuck workers are killed by process id,
-- gateway restart should not attempt to reattach old workers unless explicitly
-  designed; first version should terminate orphaned workers on startup.
+- gateway restart does not reattach old workers; `OrphanWorkerCleanupHostedService`
+  runs `OrphanWorkerTerminator` once on startup — before the server accepts
+  sessions — to kill leftover `MxGateway.Worker.exe` processes (matched by the
+  configured worker executable path, or by image name when the x64 gateway cannot
+  introspect the x86 worker's module) left behind by a previous unclean run.
 
 Because each client owns one worker, a crash or leak affects only that session.
 
diff --git a/src/MxGateway.Server/Dashboard/DashboardApiKeyManagementService.cs b/src/MxGateway.Server/Dashboard/DashboardApiKeyManagementService.cs
index 50758cf..485952a 100644
--- a/src/MxGateway.Server/Dashboard/DashboardApiKeyManagementService.cs
+++ b/src/MxGateway.Server/Dashboard/DashboardApiKeyManagementService.cs
@@ -1,6 +1,7 @@
 using System.Security.Claims;
 using Microsoft.Data.Sqlite;
 using MxGateway.Server.Security.Authentication;
+using MxGateway.Server.Security.Authorization;
 
 namespace MxGateway.Server.Dashboard;
 
@@ -171,6 +172,15 @@ public sealed class DashboardApiKeyManagementService(
             return "Display name is required.";
         }
 
+        string[] unknownScopes = request.Scopes
+            .Where(scope => !GatewayScopes.IsKnown(scope))
+            .ToArray();
+        if (unknownScopes.Length > 0)
+        {
+            return $"Unknown scope(s): {string.Join(", ", unknownScopes)}. "
+                + $"Valid scopes are: {string.Join(", ", GatewayScopes.All)}.";
+        }
+
         return null;
     }
 
diff --git a/src/MxGateway.Server/Galaxy/GalaxyHierarchyCache.cs b/src/MxGateway.Server/Galaxy/GalaxyHierarchyCache.cs
index afc1a06..fe2db2b 100644
--- a/src/MxGateway.Server/Galaxy/GalaxyHierarchyCache.cs
+++ b/src/MxGateway.Server/Galaxy/GalaxyHierarchyCache.cs
@@ -1,5 +1,4 @@
 using Google.Protobuf.WellKnownTypes;
-using Microsoft.Data.SqlClient;
 using Microsoft.Extensions.Logging;
 using MxGateway.Contracts.Proto.Galaxy;
 using MxGateway.Server.Dashboard;
@@ -181,8 +180,13 @@ public sealed class GalaxyHierarchyCache : IGalaxyHierarchyCache
         {
             throw;
         }
-        catch (Exception exception) when (exception is SqlException or InvalidOperationException)
+        catch (Exception exception)
         {
+            // Catch every non-cancellation failure — not just SqlException /
+            // InvalidOperationException. A TimeoutException or Win32Exception
+            // from connection establishment, or another DbException subtype,
+            // must still degrade gracefully to Stale/Unavailable and complete
+            // _firstLoad rather than escape and fault the refresh BackgroundService.
             _logger?.LogWarning(exception, "Galaxy hierarchy cache refresh failed.");
             GalaxyHierarchyCacheEntry failed = previous with
             {
diff --git a/src/MxGateway.Server/Galaxy/GalaxyHierarchyRefreshService.cs b/src/MxGateway.Server/Galaxy/GalaxyHierarchyRefreshService.cs
index 629a601..b629eb3 100644
--- a/src/MxGateway.Server/Galaxy/GalaxyHierarchyRefreshService.cs
+++ b/src/MxGateway.Server/Galaxy/GalaxyHierarchyRefreshService.cs
@@ -26,6 +26,15 @@ public sealed class GalaxyHierarchyRefreshService(
         {
             return;
         }
+        catch (Exception exception)
+        {
+            // A transient first-load failure (e.g. a TimeoutException or
+            // Win32Exception from connection establishment, or a DbException
+            // subtype the cache does not catch) must not fault this
+            // BackgroundService and stop the whole gateway. The cache records
+            // its own Unavailable/Stale status; the periodic tick below retries.
+            logger.LogWarning(exception, "Initial Galaxy hierarchy cache load failed; will retry on the refresh interval.");
+        }
 
         using PeriodicTimer timer = new(interval, _timeProvider);
         try
diff --git a/src/MxGateway.Server/Security/Authentication/ApiKeyAdminCommandLineParser.cs b/src/MxGateway.Server/Security/Authentication/ApiKeyAdminCommandLineParser.cs
index 235edbb..3eb3073 100644
--- a/src/MxGateway.Server/Security/Authentication/ApiKeyAdminCommandLineParser.cs
+++ b/src/MxGateway.Server/Security/Authentication/ApiKeyAdminCommandLineParser.cs
@@ -1,3 +1,5 @@
+using MxGateway.Server.Security.Authorization;
+
 namespace MxGateway.Server.Security.Authentication;
 
 public static class ApiKeyAdminCommandLineParser
@@ -95,6 +97,12 @@ public static class ApiKeyAdminCommandLineParser
             return ApiKeyAdminParseResult.Fail(validationError);
         }
 
+        string? scopeError = ValidateScopes(kind, scopes);
+        if (scopeError is not null)
+        {
+            return ApiKeyAdminParseResult.Fail(scopeError);
+        }
+
         return ApiKeyAdminParseResult.Success(new ApiKeyAdminCommand(
             Kind: kind,
             Json: json,
@@ -152,6 +160,23 @@ public static class ApiKeyAdminCommandLineParser
         return null;
     }
 
+    private static string? ValidateScopes(ApiKeyAdminCommandKind kind, IReadOnlySet<string> scopes)
+    {
+        if (kind != ApiKeyAdminCommandKind.CreateKey)
+        {
+            return null;
+        }
+
+        string[] unknown = scopes.Where(scope => !GatewayScopes.IsKnown(scope)).ToArray();
+        if (unknown.Length == 0)
+        {
+            return null;
+        }
+
+        return $"Unknown scope(s): {string.Join(", ", unknown)}. "
+            + $"Valid scopes are: {string.Join(", ", GatewayScopes.All)}.";
+    }
+
     private static string KindName(ApiKeyAdminCommandKind kind)
     {
         return kind switch
diff --git a/src/MxGateway.Server/Security/Authorization/GatewayScopes.cs b/src/MxGateway.Server/Security/Authorization/GatewayScopes.cs
index f2205da..3c7be03 100644
--- a/src/MxGateway.Server/Security/Authorization/GatewayScopes.cs
+++ b/src/MxGateway.Server/Security/Authorization/GatewayScopes.cs
@@ -10,4 +10,28 @@ public static class GatewayScopes
     public const string EventsRead = "events:read";
     public const string MetadataRead = "metadata:read";
     public const string Admin = "admin";
+
+    /// <summary>
+    ///     The complete catalog of canonical scope strings the gateway authorization
+    ///     resolver recognizes. Key-creation paths (CLI and dashboard) validate requested
+    ///     scopes against this set so a typo or non-canonical name cannot persist a key
+    ///     whose scope strings the resolver never matches.
+    /// </summary>
+    public static readonly IReadOnlySet<string> All = new HashSet<string>(
+        [
+            SessionOpen,
+            SessionClose,
+            InvokeRead,
+            InvokeWrite,
+            InvokeSecure,
+            EventsRead,
+            MetadataRead,
+            Admin,
+        ],
+        System.StringComparer.Ordinal);
+
+    /// <summary>Determines whether the supplied scope string is a recognized canonical scope.</summary>
+    /// <param name="scope">Scope string to check.</param>
+    /// <returns><see langword="true"/> when the scope is canonical; otherwise <see langword="false"/>.</returns>
+    public static bool IsKnown(string scope) => All.Contains(scope);
 }
diff --git a/src/MxGateway.Server/Sessions/SessionManager.cs b/src/MxGateway.Server/Sessions/SessionManager.cs
index 3ea5a3f..7fbd22d 100644
--- a/src/MxGateway.Server/Sessions/SessionManager.cs
+++ b/src/MxGateway.Server/Sessions/SessionManager.cs
@@ -68,6 +68,7 @@ public sealed class SessionManager : ISessionManager
         EnsureSessionCapacity();
 
         GatewaySession? session = null;
+        bool sessionOpenedRecorded = false;
         try
         {
             session = CreateSession(request, clientIdentity);
@@ -86,6 +87,7 @@ public sealed class SessionManager : ISessionManager
             session.AttachWorkerClient(workerClient);
             session.MarkReady();
             _metrics.SessionOpened();
+            sessionOpenedRecorded = true;
 
             await TryAutoSubscribeAlarmsAsync(session, cancellationToken).ConfigureAwait(false);
 
@@ -100,6 +102,14 @@ public sealed class SessionManager : ISessionManager
                 await session.DisposeAsync().ConfigureAwait(false);
             }
 
+            // If SessionOpened() already incremented the open-session gauge,
+            // a failure after that point (e.g. auto-subscribe rejection) must
+            // decrement it again so mxgateway.sessions.open does not leak.
+            if (sessionOpenedRecorded)
+            {
+                _metrics.SessionRemoved();
+            }
+
             ReleaseSessionSlot();
             _metrics.Fault(SessionManagerErrorCode.OpenFailed.ToString());
             _logger.LogWarning(
diff --git a/src/MxGateway.Server/Workers/IRunningProcessInspector.cs b/src/MxGateway.Server/Workers/IRunningProcessInspector.cs
new file mode 100644
index 0000000..f12bf76
--- /dev/null
+++ b/src/MxGateway.Server/Workers/IRunningProcessInspector.cs
@@ -0,0 +1,29 @@
+namespace MxGateway.Server.Workers;
+
+/// <summary>
+///     Abstraction over OS process enumeration and termination. Exists so the
+///     orphan-worker cleanup logic can be unit-tested without spawning real
+///     processes.
+/// </summary>
+public interface IRunningProcessInspector
+{
+    /// <summary>
+    ///     Enumerates currently running processes whose image name (without the
+    ///     <c>.exe</c> extension) matches <paramref name="processName"/>.
+    /// </summary>
+    /// <param name="processName">Process image name to match, without extension.</param>
+    /// <returns>The matching running processes.</returns>
+    IReadOnlyList<RunningProcessInfo> GetProcessesByName(string processName);
+
+    /// <summary>Forcibly terminates the process with the given identifier.</summary>
+    /// <param name="processId">Identifier of the process to terminate.</param>
+    void Kill(int processId);
+}
+
+/// <summary>Identifying information for a running process candidate.</summary>
+/// <param name="ProcessId">Operating-system process identifier.</param>
+/// <param name="ExecutablePath">
+///     Fully-qualified path to the process main module, or <see langword="null"/>
+///     when it could not be read (e.g. access denied).
+/// </param>
+public sealed record RunningProcessInfo(int ProcessId, string? ExecutablePath);
diff --git a/src/MxGateway.Server/Workers/OrphanWorkerCleanupHostedService.cs b/src/MxGateway.Server/Workers/OrphanWorkerCleanupHostedService.cs
new file mode 100644
index 0000000..8b71d11
--- /dev/null
+++ b/src/MxGateway.Server/Workers/OrphanWorkerCleanupHostedService.cs
@@ -0,0 +1,30 @@
+namespace MxGateway.Server.Workers;
+
+/// <summary>
+///     Hosted service that terminates leftover MXAccess worker processes once on
+///     gateway startup, before the server begins accepting sessions.
+/// </summary>
+public sealed class OrphanWorkerCleanupHostedService(
+    OrphanWorkerTerminator terminator,
+    ILogger<OrphanWorkerCleanupHostedService> logger) : IHostedService
+{
+    /// <inheritdoc />
+    public Task StartAsync(CancellationToken cancellationToken)
+    {
+        try
+        {
+            terminator.TerminateOrphans();
+        }
+        catch (Exception exception)
+        {
+            // Orphan cleanup is best-effort; a failure here must not prevent
+            // the gateway from starting.
+            logger.LogWarning(exception, "Orphan worker cleanup failed on startup.");
+        }
+
+        return Task.CompletedTask;
+    }
+
+    /// <inheritdoc />
+    public Task StopAsync(CancellationToken cancellationToken) => Task.CompletedTask;
+}
diff --git a/src/MxGateway.Server/Workers/OrphanWorkerTerminator.cs b/src/MxGateway.Server/Workers/OrphanWorkerTerminator.cs
new file mode 100644
index 0000000..a344e8b
--- /dev/null
+++ b/src/MxGateway.Server/Workers/OrphanWorkerTerminator.cs
@@ -0,0 +1,138 @@
+using Microsoft.Extensions.Logging.Abstractions;
+using Microsoft.Extensions.Options;
+using MxGateway.Server.Configuration;
+using MxGateway.Server.Metrics;
+
+namespace MxGateway.Server.Workers;
+
+/// <summary>
+///     Terminates leftover MXAccess worker processes on gateway startup.
+///     <para>
+///         Per <c>gateway.md</c> ("first version should terminate orphaned workers
+///         on startup") and CLAUDE.md, a gateway restart does not reattach old
+///         workers. After an unclean gateway crash, x86 worker processes — each
+///         holding an MXAccess COM instance on an STA — survive indefinitely. This
+///         terminator finds those processes by executable name/path and kills them
+///         before the restarted gateway accepts sessions.
+///     </para>
+/// </summary>
+public sealed class OrphanWorkerTerminator
+{
+    private readonly IRunningProcessInspector _inspector;
+    private readonly GatewayMetrics _metrics;
+    private readonly WorkerOptions _workerOptions;
+    private readonly ILogger<OrphanWorkerTerminator> _logger;
+
+    /// <summary>Initializes a new instance of the <see cref="OrphanWorkerTerminator"/> class.</summary>
+    /// <param name="gatewayOptions">Gateway configuration options.</param>
+    /// <param name="inspector">Running-process inspector.</param>
+    /// <param name="metrics">Gateway metrics collector.</param>
+    /// <param name="logger">Optional logger for diagnostic output.</param>
+    public OrphanWorkerTerminator(
+        IOptions<GatewayOptions> gatewayOptions,
+        IRunningProcessInspector inspector,
+        GatewayMetrics metrics,
+        ILogger<OrphanWorkerTerminator>? logger = null)
+    {
+        ArgumentNullException.ThrowIfNull(gatewayOptions);
+        _inspector = inspector ?? throw new ArgumentNullException(nameof(inspector));
+        _metrics = metrics ?? throw new ArgumentNullException(nameof(metrics));
+        _workerOptions = gatewayOptions.Value.Worker;
+        _logger = logger ?? NullLogger<OrphanWorkerTerminator>.Instance;
+    }
+
+    /// <summary>
+    ///     Finds and kills every leftover worker process. Safe to call once at
+    ///     startup before any session-owned worker is launched.
+    /// </summary>
+    /// <returns>The number of orphan worker processes that were terminated.</returns>
+    public int TerminateOrphans()
+    {
+        string? configuredPath = ResolveConfiguredExecutablePath();
+        string processName = ResolveProcessName(configuredPath);
+        int currentProcessId = Environment.ProcessId;
+
+        int terminated = 0;
+        foreach (RunningProcessInfo candidate in _inspector.GetProcessesByName(processName))
+        {
+            if (candidate.ProcessId == currentProcessId)
+            {
+                continue;
+            }
+
+            if (!IsOrphanWorker(candidate, configuredPath))
+            {
+                continue;
+            }
+
+            try
+            {
+                _inspector.Kill(candidate.ProcessId);
+                _metrics.WorkerKilled("OrphanStartupCleanup");
+                terminated++;
+                _logger.LogWarning(
+                    "Terminated orphan worker process {ProcessId} ({ExecutablePath}) left over from a previous gateway run.",
+                    candidate.ProcessId,
+                    candidate.ExecutablePath ?? processName);
+            }
+            catch (Exception exception)
+            {
+                // The process may have already exited, or be inaccessible.
+                // A failure to kill one orphan must not block gateway startup.
+                _logger.LogWarning(
+                    exception,
+                    "Failed to terminate orphan worker process {ProcessId}.",
+                    candidate.ProcessId);
+            }
+        }
+
+        if (terminated > 0)
+        {
+            _logger.LogInformation("Terminated {Count} orphan worker process(es) on startup.", terminated);
+        }
+
+        return terminated;
+    }
+
+    private static bool IsOrphanWorker(RunningProcessInfo candidate, string? configuredPath)
+    {
+        // When the executable path is readable, require an exact match against
+        // the configured worker path so unrelated processes that merely share
+        // the image name are never killed.
+        if (candidate.ExecutablePath is { } path)
+        {
+            return configuredPath is not null
+                && string.Equals(path, configuredPath, StringComparison.OrdinalIgnoreCase);
+        }
+
+        // A null path means the x64 gateway could not introspect the module —
+        // the expected case for the x86 worker. Image-name match is the only
+        // signal available; treat it as an orphan.
+        return true;
+    }
+
+    private string? ResolveConfiguredExecutablePath()
+    {
+        try
+        {
+            return Path.GetFullPath(_workerOptions.ExecutablePath);
+        }
+        catch (Exception exception) when (exception is ArgumentException
+            or NotSupportedException
+            or PathTooLongException)
+        {
+            _logger.LogWarning(
+                exception,
+                "Configured worker executable path '{ExecutablePath}' is not a valid filesystem path; "
+                + "orphan cleanup will match by image name only.",
+                _workerOptions.ExecutablePath);
+            return null;
+        }
+    }
+
+    private static string ResolveProcessName(string? configuredPath)
+    {
+        string source = configuredPath ?? "MxGateway.Worker.exe";
+        return Path.GetFileNameWithoutExtension(source);
+    }
+}
diff --git a/src/MxGateway.Server/Workers/SystemRunningProcessInspector.cs b/src/MxGateway.Server/Workers/SystemRunningProcessInspector.cs
new file mode 100644
index 0000000..de5ed61
--- /dev/null
+++ b/src/MxGateway.Server/Workers/SystemRunningProcessInspector.cs
@@ -0,0 +1,55 @@
+using System.Diagnostics;
+
+namespace MxGateway.Server.Workers;
+
+/// <summary>
+///     <see cref="IRunningProcessInspector"/> backed by <see cref="Process"/>.
+/// </summary>
+public sealed class SystemRunningProcessInspector : IRunningProcessInspector
+{
+    /// <inheritdoc />
+    public IReadOnlyList<RunningProcessInfo> GetProcessesByName(string processName)
+    {
+        List<RunningProcessInfo> results = [];
+        Process[] processes = Process.GetProcessesByName(processName);
+        try
+        {
+            foreach (Process process in processes)
+            {
+                results.Add(new RunningProcessInfo(process.Id, TryGetExecutablePath(process)));
+            }
+        }
+        finally
+        {
+            foreach (Process process in processes)
+            {
+                process.Dispose();
+            }
+        }
+
+        return results;
+    }
+
+    /// <inheritdoc />
+    public void Kill(int processId)
+    {
+        using Process process = Process.GetProcessById(processId);
+        process.Kill(entireProcessTree: true);
+    }
+
+    private static string? TryGetExecutablePath(Process process)
+    {
+        try
+        {
+            return process.MainModule?.FileName;
+        }
+        catch (Exception exception) when (exception is InvalidOperationException
+            or System.ComponentModel.Win32Exception
+            or NotSupportedException)
+        {
+            // Access to the main module can be denied (e.g. a 64-bit gateway
+            // querying a 32-bit worker, or a process owned by another user).
+            return null;
+        }
+    }
+}
diff --git a/src/MxGateway.Server/Workers/WorkerServiceCollectionExtensions.cs b/src/MxGateway.Server/Workers/WorkerServiceCollectionExtensions.cs
index d387573..062cb40 100644
--- a/src/MxGateway.Server/Workers/WorkerServiceCollectionExtensions.cs
+++ b/src/MxGateway.Server/Workers/WorkerServiceCollectionExtensions.cs
@@ -11,6 +11,13 @@ public static class WorkerServiceCollectionExtensions
         services.AddSingleton<IWorkerStartupProbe, WorkerProcessStartedProbe>();
         services.AddSingleton<IWorkerProcessLauncher, WorkerProcessLauncher>();
 
+        // Terminate workers leaked by a previous unclean gateway run before the
+        // server accepts sessions. Registered ahead of AddGatewaySessions so the
+        // cleanup hosted service starts before the session subsystem.
+        services.AddSingleton<IRunningProcessInspector, SystemRunningProcessInspector>();
+        services.AddSingleton<OrphanWorkerTerminator>();
+        services.AddHostedService<OrphanWorkerCleanupHostedService>();
+
         return services;
     }
 }
diff --git a/src/MxGateway.Tests/Galaxy/GalaxyHierarchyRefreshServiceTests.cs b/src/MxGateway.Tests/Galaxy/GalaxyHierarchyRefreshServiceTests.cs
new file mode 100644
index 0000000..f0759f2
--- /dev/null
+++ b/src/MxGateway.Tests/Galaxy/GalaxyHierarchyRefreshServiceTests.cs
@@ -0,0 +1,64 @@
+using Microsoft.Extensions.Logging.Abstractions;
+using Microsoft.Extensions.Options;
+using MxGateway.Server.Galaxy;
+
+namespace MxGateway.Tests.Galaxy;
+
+/// <summary>
+///     Server-005 regression: the initial <c>RefreshAsync</c> call in
+///     <see cref="GalaxyHierarchyRefreshService"/> must not let a transient,
+///     non-cancellation first-load failure (e.g. a <see cref="TimeoutException"/>
+///     or <see cref="System.ComponentModel.Win32Exception"/> from connection
+///     establishment) escape and fault the host <c>BackgroundService</c>.
+/// </summary>
+public sealed class GalaxyHierarchyRefreshServiceTests
+{
+    [Fact]
+    public async Task ExecuteAsync_WhenFirstRefreshThrowsNonCancellationException_DoesNotFaultBackgroundService()
+    {
+        ThrowingCache cache = new(new TimeoutException("connection establishment timed out"));
+        GalaxyHierarchyRefreshService service = CreateService(cache);
+
+        using CancellationTokenSource cts = new();
+
+        await service.StartAsync(cts.Token);
+        await cts.CancelAsync();
+
+        // The background loop must have stopped cleanly: ExecuteTask completes
+        // (RanToCompletion or Canceled) rather than faulting on the first refresh.
+        Task? executeTask = service.ExecuteTask;
+        Assert.NotNull(executeTask);
+        await executeTask;
+        Assert.False(executeTask.IsFaulted);
+        Assert.Equal(1, cache.RefreshCallCount);
+
+        await service.StopAsync(CancellationToken.None);
+    }
+
+    private static GalaxyHierarchyRefreshService CreateService(IGalaxyHierarchyCache cache)
+    {
+        GalaxyRepositoryOptions options = new()
+        {
+            DashboardRefreshIntervalSeconds = 3600,
+        };
+        return new GalaxyHierarchyRefreshService(
+            cache,
+            Options.Create(options),
+            NullLogger<GalaxyHierarchyRefreshService>.Instance);
+    }
+
+    private sealed class ThrowingCache(Exception toThrow) : IGalaxyHierarchyCache
+    {
+        public int RefreshCallCount { get; private set; }
+
+        public GalaxyHierarchyCacheEntry Current => GalaxyHierarchyCacheEntry.Empty;
+
+        public Task RefreshAsync(CancellationToken cancellationToken)
+        {
+            RefreshCallCount++;
+            throw toThrow;
+        }
+
+        public Task WaitForFirstLoadAsync(CancellationToken cancellationToken) => Task.CompletedTask;
+    }
+}
diff --git a/src/MxGateway.Tests/Gateway/Dashboard/DashboardApiKeyManagementServiceTests.cs b/src/MxGateway.Tests/Gateway/Dashboard/DashboardApiKeyManagementServiceTests.cs
index 818b481..f69eeeb 100644
--- a/src/MxGateway.Tests/Gateway/Dashboard/DashboardApiKeyManagementServiceTests.cs
+++ b/src/MxGateway.Tests/Gateway/Dashboard/DashboardApiKeyManagementServiceTests.cs
@@ -112,6 +112,33 @@ public sealed class DashboardApiKeyManagementServiceTests
             && entry.Details == "rotated");
     }
 
+    /// <summary>
+    ///     Server-004 regression: the dashboard create path must reject a request
+    ///     carrying a non-canonical scope string rather than persisting a key whose
+    ///     scope the authorization resolver never matches.
+    /// </summary>
+    [Fact]
+    public async Task CreateAsync_UnknownScope_DoesNotCallStore()
+    {
+        FakeApiKeyAdminStore adminStore = new();
+        DashboardApiKeyManagementService service = CreateService(adminStore);
+
+        DashboardApiKeyManagementRequest request = CreateRequest() with
+        {
+            Scopes = new HashSet<string>(
+                [GatewayScopes.SessionOpen, "invoke", "metadata"],
+                StringComparer.Ordinal),
+        };
+
+        DashboardApiKeyManagementResult result = await service.CreateAsync(
+            CreateAuthorizedUser(),
+            request,
+            CancellationToken.None);
+
+        Assert.False(result.Succeeded);
+        Assert.Equal(0, adminStore.CreateCount);
+    }
+
     private static DashboardApiKeyManagementService CreateService(
         FakeApiKeyAdminStore? adminStore = null,
         FakeApiKeyAuditStore? auditStore = null,
diff --git a/src/MxGateway.Tests/Gateway/Sessions/SessionManagerAlarmAutoSubscribeTests.cs b/src/MxGateway.Tests/Gateway/Sessions/SessionManagerAlarmAutoSubscribeTests.cs
index 89dfc84..e4c3175 100644
--- a/src/MxGateway.Tests/Gateway/Sessions/SessionManagerAlarmAutoSubscribeTests.cs
+++ b/src/MxGateway.Tests/Gateway/Sessions/SessionManagerAlarmAutoSubscribeTests.cs
@@ -125,6 +125,44 @@ public sealed class SessionManagerAlarmAutoSubscribeTests
                 CreateOpenRequest(), "client-1", CancellationToken.None));
     }
 
+    /// <summary>
+    ///     Server-006 regression: when auto-subscribe throws after
+    ///     <c>SessionOpened()</c> incremented the open-session gauge, the failed
+    ///     open must not leave <c>mxgateway.sessions.open</c> over-counted.
+    /// </summary>
+    [Fact]
+    public async Task OpenSessionAsync_DoesNotLeakOpenSessionGauge_WhenAutoSubscribeFailsWithRequireOn()
+    {
+        AlarmAutoSubscribeWorkerClient worker = new()
+        {
+            SubscribeAlarmsReplyFactory = _ => new MxCommandReply
+            {
+                Kind = MxCommandKind.SubscribeAlarms,
+                ProtocolStatus = new ProtocolStatus
+                {
+                    Code = ProtocolStatusCode.MxaccessFailure,
+                    Message = "wnwrap subscribe failed",
+                },
+            },
+        };
+        using GatewayMetrics metrics = new();
+        SessionManager manager = NewManager(
+            worker,
+            alarms: new AlarmsOptions
+            {
+                Enabled = true,
+                SubscriptionExpression = @"\\HOST\Galaxy!Area1",
+                RequireSubscribeOnOpen = true,
+            },
+            metrics: metrics);
+
+        await Assert.ThrowsAsync<SessionManagerException>(
+            async () => await manager.OpenSessionAsync(
+                CreateOpenRequest(), "client-1", CancellationToken.None));
+
+        Assert.Equal(0, metrics.GetSnapshot().OpenSessions);
+    }
+
     [Fact]
     public async Task OpenSessionAsync_Throws_WhenEnabledButNoExpressionAndRequireOn()
     {
@@ -161,7 +199,8 @@ public sealed class SessionManagerAlarmAutoSubscribeTests
 
     private static SessionManager NewManager(
         AlarmAutoSubscribeWorkerClient worker,
-        AlarmsOptions alarms)
+        AlarmsOptions alarms,
+        GatewayMetrics? metrics = null)
     {
         FakeSessionWorkerClientFactory factory = new(worker);
         GatewayOptions options = new GatewayOptions
@@ -183,7 +222,7 @@ public sealed class SessionManagerAlarmAutoSubscribeTests
             new SessionRegistry(),
             factory,
             Options.Create(options),
-            new GatewayMetrics());
+            metrics ?? new GatewayMetrics());
     }
 
     private static SessionOpenRequest CreateOpenRequest()
diff --git a/src/MxGateway.Tests/Gateway/Workers/OrphanWorkerTerminatorTests.cs b/src/MxGateway.Tests/Gateway/Workers/OrphanWorkerTerminatorTests.cs
new file mode 100644
index 0000000..4f68dfd
--- /dev/null
+++ b/src/MxGateway.Tests/Gateway/Workers/OrphanWorkerTerminatorTests.cs
@@ -0,0 +1,137 @@
+using Microsoft.Extensions.Options;
+using MxGateway.Server.Configuration;
+using MxGateway.Server.Metrics;
+using MxGateway.Server.Workers;
+
+namespace MxGateway.Tests.Gateway.Workers;
+
+/// <summary>
+///     Server-002 regression: per <c>gateway.md</c> the gateway must terminate
+///     orphaned worker processes on startup. These tests pin that the terminator
+///     kills leftover workers (matched by executable path, or by image name when
+///     the path is unreadable) without touching unrelated processes or itself.
+/// </summary>
+public sealed class OrphanWorkerTerminatorTests
+{
+    private const string WorkerExecutablePath = @"C:\app\src\MxGateway.Worker\bin\x86\Release\MxGateway.Worker.exe";
+
+    [Fact]
+    public void TerminateOrphans_KillsWorkerProcessesMatchingConfiguredExecutablePath()
+    {
+        FakeProcessInspector inspector = new(
+        [
+            new RunningProcessInfo(101, WorkerExecutablePath),
+            new RunningProcessInfo(102, WorkerExecutablePath),
+        ]);
+        OrphanWorkerTerminator terminator = CreateTerminator(inspector);
+
+        int killed = terminator.TerminateOrphans();
+
+        Assert.Equal(2, killed);
+        Assert.Equal([101, 102], inspector.KilledProcessIds.Order());
+    }
+
+    [Fact]
+    public void TerminateOrphans_KillsImageNameMatchWhenExecutablePathUnreadable()
+    {
+        // The x64 gateway cannot introspect the x86 worker's main module, so the
+        // path comes back null. Image-name match is the only signal — and it is
+        // exactly the orphan worker case, so the process must still be killed.
+        FakeProcessInspector inspector = new(
+        [
+            new RunningProcessInfo(201, ExecutablePath: null),
+        ]);
+        OrphanWorkerTerminator terminator = CreateTerminator(inspector);
+
+        int killed = terminator.TerminateOrphans();
+
+        Assert.Equal(1, killed);
+        Assert.Equal([201], inspector.KilledProcessIds);
+    }
+
+    [Fact]
+    public void TerminateOrphans_DoesNotKillUnrelatedProcessSharingImageName()
+    {
+        // A process with the same image name but a different executable path is
+        // not our worker and must be left alone.
+        FakeProcessInspector inspector = new(
+        [
+            new RunningProcessInfo(301, @"C:\other\place\MxGateway.Worker.exe"),
+        ]);
+        OrphanWorkerTerminator terminator = CreateTerminator(inspector);
+
+        int killed = terminator.TerminateOrphans();
+
+        Assert.Equal(0, killed);
+        Assert.Empty(inspector.KilledProcessIds);
+    }
+
+    [Fact]
+    public void TerminateOrphans_DoesNotKillCurrentProcess()
+    {
+        FakeProcessInspector inspector = new(
+        [
+            new RunningProcessInfo(Environment.ProcessId, WorkerExecutablePath),
+        ]);
+        OrphanWorkerTerminator terminator = CreateTerminator(inspector);
+
+        int killed = terminator.TerminateOrphans();
+
+        Assert.Equal(0, killed);
+        Assert.Empty(inspector.KilledProcessIds);
+    }
+
+    [Fact]
+    public void TerminateOrphans_ContinuesWhenOneKillThrows()
+    {
+        FakeProcessInspector inspector = new(
+        [
+            new RunningProcessInfo(401, WorkerExecutablePath),
+            new RunningProcessInfo(402, WorkerExecutablePath),
+        ])
+        {
+            ThrowOnKillProcessId = 401,
+        };
+        OrphanWorkerTerminator terminator = CreateTerminator(inspector);
+
+        int killed = terminator.TerminateOrphans();
+
+        Assert.Equal(1, killed);
+        Assert.Contains(402, inspector.KilledProcessIds);
+    }
+
+    private static OrphanWorkerTerminator CreateTerminator(IRunningProcessInspector inspector)
+    {
+        GatewayOptions options = new()
+        {
+            Worker = new WorkerOptions
+            {
+                ExecutablePath = WorkerExecutablePath,
+            },
+        };
+        return new OrphanWorkerTerminator(
+            Options.Create(options),
+            inspector,
+            new GatewayMetrics());
+    }
+
+    private sealed class FakeProcessInspector(IReadOnlyList<RunningProcessInfo> processes)
+        : IRunningProcessInspector
+    {
+        public List<int> KilledProcessIds { get; } = [];
+
+        public int? ThrowOnKillProcessId { get; init; }
+
+        public IReadOnlyList<RunningProcessInfo> GetProcessesByName(string processName) => processes;
+
+        public void Kill(int processId)
+        {
+            if (ThrowOnKillProcessId == processId)
+            {
+                throw new InvalidOperationException("Process has already exited.");
+            }
+
+            KilledProcessIds.Add(processId);
+        }
+    }
+}
diff --git a/src/MxGateway.Tests/Security/Authentication/ApiKeyAdminCommandLineParserTests.cs b/src/MxGateway.Tests/Security/Authentication/ApiKeyAdminCommandLineParserTests.cs
index de43c31..99e3e47 100644
--- a/src/MxGateway.Tests/Security/Authentication/ApiKeyAdminCommandLineParserTests.cs
+++ b/src/MxGateway.Tests/Security/Authentication/ApiKeyAdminCommandLineParserTests.cs
@@ -52,6 +52,56 @@ public sealed class ApiKeyAdminCommandLineParserTests
         Assert.Contains("events:read", result.Command.Scopes);
     }
 
+    /// <summary>
+    ///     Server-004 regression: a create-key command with a non-canonical scope
+    ///     string (e.g. CLAUDE.md's stale <c>invoke</c> instead of <c>invoke:read</c>)
+    ///     must be rejected at parse time rather than silently persisting an
+    ///     unusable scope the authorization resolver never matches.
+    /// </summary>
+    [Fact]
+    public void Parse_CreateKeyCommand_RejectsUnknownScope()
+    {
+        ApiKeyAdminParseResult result = ApiKeyAdminCommandLineParser.Parse(
+            [
+                "apikey",
+                "create-key",
+                "--key-id",
+                "operator01",
+                "--display-name",
+                "Operator",
+                "--scopes",
+                "session:open,invoke,metadata",
+            ]);
+
+        Assert.True(result.IsApiKeyCommand);
+        Assert.Null(result.Command);
+        Assert.NotNull(result.Error);
+        Assert.Contains("invoke", result.Error, StringComparison.Ordinal);
+        Assert.Contains("metadata", result.Error, StringComparison.Ordinal);
+    }
+
+    /// <summary>Verifies a create-key command with only canonical scopes parses successfully.</summary>
+    [Fact]
+    public void Parse_CreateKeyCommand_AcceptsAllCanonicalScopes()
+    {
+        ApiKeyAdminParseResult result = ApiKeyAdminCommandLineParser.Parse(
+            [
+                "apikey",
+                "create-key",
+                "--key-id",
+                "operator01",
+                "--display-name",
+                "Operator",
+                "--scopes",
+                "session:open,session:close,invoke:read,invoke:write,invoke:secure,events:read,metadata:read,admin",
+            ]);
+
+        Assert.True(result.IsApiKeyCommand);
+        Assert.Null(result.Error);
+        Assert.NotNull(result.Command);
+        Assert.Equal(8, result.Command.Scopes.Count);
+    }
+
     /// <summary>
     /// Verifies create key without display name returns error.
     /// </summary>