Issue #7: implement local api key admin cli

Verified with dotnet build src\\MxGateway.sln, dotnet test src\\MxGateway.Worker.Tests\\MxGateway.Worker.Tests.csproj -p:Platform=x86, and dotnet test src\\MxGateway.sln --no-build.

docs/WorkerFrameProtocol.md

@@ -0,0 +1,54 @@
+# Worker Frame Protocol
+
+The gateway uses the worker frame protocol to move `WorkerEnvelope` protobuf
+messages over a bidirectional named pipe. The frame layer is deliberately small:
+it handles message boundaries, size limits, protobuf parsing, and envelope
+validation before higher-level worker client code routes commands, replies,
+events, and faults.
+
+## Frame Format
+
+Each frame starts with a four-byte little-endian unsigned payload length,
+followed by the serialized `WorkerEnvelope` payload:
+
+```text
+uint32 little-endian payload_length
+payload_length bytes protobuf WorkerEnvelope
+```
+
+The reader rejects zero-length payloads and payloads larger than the configured
+maximum before allocating the payload buffer. The default maximum is 16 MiB,
+matching the gateway process design.
+
+## Envelope Validation
+
+`WorkerFrameReader` and `WorkerFrameWriter` validate each envelope against the
+owning session before returning or writing it:
+
+- `protocol_version` must match the configured worker protocol version,
+- `session_id` must match the owning gateway session,
+- the envelope must contain one typed `body` value.
+
+Protocol violations throw `WorkerFrameProtocolException` with a
+`WorkerFrameProtocolErrorCode` so callers can distinguish malformed frames,
+oversized frames, protocol version mismatches, and session mismatches.
+
+## Verification
+
+Run the focused tests after changing the frame protocol:
+
+```bash
+dotnet test src/MxGateway.Tests/MxGateway.Tests.csproj --filter WorkerFrameProtocolTests
+```
+
+Run the gateway build because the frame protocol is part of
+`MxGateway.Server`:
+
+```bash
+dotnet build src/MxGateway.Server/MxGateway.Server.csproj
+```
+
+## Related Documentation
+
+- [Gateway Process Detailed Design](./gateway-process-design.md)
+- [Protobuf Contracts](./Contracts.md)

docs/WorkerProcessLauncher.md

@@ -0,0 +1,62 @@
+# Worker Process Launcher
+
+The gateway uses `WorkerProcessLauncher` to validate and start one worker
+process for a gateway session. The launcher owns process start semantics only;
+pipe handshaking and `WorkerReady` validation remain part of the worker client
+startup path.
+
+## Launch Inputs
+
+`WorkerProcessLaunchRequest` carries the per-session bootstrap values:
+
+- `SessionId`,
+- `PipeName`,
+- `ProtocolVersion`,
+- `Nonce`,
+- optional `PipeReservation` cleanup handle.
+
+The launcher passes `SessionId`, `PipeName`, and `ProtocolVersion` as command
+line arguments:
+
+```text
+--session-id <sessionId> --pipe-name <pipeName> --protocol-version <version>
+```
+
+The launcher sets the nonce through the `MXGATEWAY_WORKER_NONCE` environment
+variable. The nonce is not included in `WorkerProcessCommandLine` so logs and
+diagnostics can report the launch command without exposing the secret.
+
+## Validation And Cleanup
+
+Before starting the process, the launcher validates that the configured worker
+path exists, has a `.exe` extension, contains a valid Windows Portable
+Executable header, and matches the configured `RequiredArchitecture`.
+
+After the process starts, `IWorkerStartupProbe` waits for startup readiness.
+The default probe only verifies that the worker did not exit immediately. The
+worker client replaces this probe when pipe connection, hello, and
+`WorkerReady` handling are implemented.
+
+If startup fails or exceeds `WorkerOptions.StartupTimeoutSeconds`, the launcher
+kills the worker process tree, disposes the process handle, disposes the
+optional pipe reservation, records a worker kill metric, and reports a
+`WorkerProcessLaunchException`.
+
+## Verification
+
+Run the focused launcher tests after changing process launch behavior:
+
+```bash
+dotnet test src/MxGateway.Tests/MxGateway.Tests.csproj --filter WorkerProcessLauncherTests
+```
+
+Run the gateway build because the launcher is part of `MxGateway.Server`:
+
+```bash
+dotnet build src/MxGateway.Server/MxGateway.Server.csproj
+```
+
+## Related Documentation
+
+- [Gateway Process Detailed Design](./gateway-process-design.md)
+- [Worker Frame Protocol](./WorkerFrameProtocol.md)

docs/gateway-dashboard-design.md

@@ -105,6 +105,12 @@ Do not let Razor components directly mutate gateway session or worker objects.
 Create a small read-only dashboard service that projects gateway state into
 plain DTOs.
 
+`GatewayMetrics.GetSnapshot()` is the metrics input for the first dashboard
+projection. It carries current session and worker gauges, command and event
+counters, queue depth, and fault totals. The dashboard reads that snapshot
+instead of reading raw `Meter` instruments because exporter configuration is an
+operations concern, not a UI dependency.
+
 Suggested service:
 
 ```csharp
@@ -361,4 +367,3 @@ The first dashboard slice should implement:
 8. workers page with worker table.
 9. 1-second realtime refresh through Blazor Server.
 10. redaction tests for secrets.
-

docs/gateway-process-design.md

@@ -360,6 +360,15 @@ Before launch, validate:
 - worker file version or product version is acceptable,
 - worker is expected to be x86.
 
+`WorkerProcessLauncher` implements the first validation layer now: it resolves
+the worker executable path, requires a `.exe`, validates the Windows Portable
+Executable header, and verifies the configured processor architecture. It passes
+only `--session-id`, `--pipe-name`, and `--protocol-version` on the command
+line. The per-session nonce is set through `MXGATEWAY_WORKER_NONCE` so the
+command line remains safe to log. Startup failures and startup timeouts kill and
+dispose the worker process and the pre-created pipe reservation before the
+session manager observes the failure.
+
 ## Worker IPC
 
 The gateway creates the pipe server before launching the worker.
@@ -589,6 +598,20 @@ The gateway should split the key into a stable key id and secret component,
 load the key record by id, hash the presented secret, and compare using a
 constant-time comparison.
 
+`ApiKeyParser` accepts only `authorization: Bearer mxgw_<key-id>_<secret>`.
+Malformed headers fail before any database lookup. The parsed raw secret is
+kept only long enough for `ApiKeySecretHasher` to compute an HMAC-SHA256 hash
+using the configured `Authentication:PepperSecretName` lookup in application
+configuration. The raw secret is not stored in the auth database, identity
+model, logs, or verification result.
+
+`ApiKeyVerifier` loads the stored key record by key id, rejects revoked keys,
+hashes the presented secret, and compares the stored and presented hashes with
+`CryptographicOperations.FixedTimeEquals`. A successful verification returns an
+`ApiKeyIdentity` with key id, key prefix, display name, and scopes. Failure
+results distinguish malformed credentials, missing keys, revoked keys, missing
+pepper configuration, and hash mismatch for internal authorization handling.
+
 Recommended scopes:
 
 - `session:open`
@@ -608,10 +631,44 @@ gRPC admin API. It should initialize the auth database, create keys, list keys
 without secrets, revoke keys, rotate keys, and print raw secrets only once at
 creation.
 
+`MxGateway.Server` exposes local API-key administration as an `apikey`
+subcommand before the web host starts:
+
+```bash
+MxGateway.Server apikey init-db --sqlite-path C:\ProgramData\MxGateway\gateway-auth.db
+MxGateway.Server apikey create-key --key-id operator01 --display-name Operator --scopes session:open,events:read
+MxGateway.Server apikey list-keys --json
+MxGateway.Server apikey revoke-key --key-id operator01
+MxGateway.Server apikey rotate-key --key-id operator01 --json
+```
+
+The subcommands accept `--sqlite-path`, `--pepper`, and `--json`. `--pepper`
+sets the local `MxGateway:ApiKeyPepper` configuration value for the command
+process; deployments should normally provide the pepper through the configured
+secret source. `create-key` and `rotate-key` print the full raw API key exactly
+once. `list-keys` never prints raw secrets or `secret_hash` values.
+
 SQLite auth storage should use startup migrations with a `schema_version` table.
 Migrations should run inside transactions and fail startup if the database
 schema is newer than the running binary understands.
 
+The v1 auth store uses `Microsoft.Data.Sqlite` and creates the
+`schema_version`, `api_keys`, and `api_key_audit` tables through
+`SqliteAuthStoreMigrator`. `AuthStoreMigrationHostedService` runs those
+migrations at gateway startup when API-key authentication and
+`Authentication:RunMigrationsOnStartup` are enabled. A database with a newer
+schema version fails startup instead of being modified by an older gateway
+binary.
+
+`IApiKeyStore` reads stored key records and exposes an active-key lookup that
+excludes rows with `revoked_utc` set. Hash verification belongs to the API-key
+hashing layer, but the store preserves the `secret_hash` bytes, display name,
+scopes, timestamps, and revocation state needed by that layer.
+
+`IApiKeyAuditStore` appends audit events to `api_key_audit` and returns recent
+events for diagnostics and future administrative tools. Audit records store key
+ids and event metadata only; they do not store raw API key secrets.
+
 Commands requiring authorization:
 
 - writes,
@@ -664,6 +721,26 @@ Metrics:
 
 Do not log credential values or full tag values by default.
 
+The gateway registers `GatewayMetrics` as the in-process metrics foundation.
+It emits .NET `Meter` instruments for collectors and keeps a
+`GatewayMetricsSnapshot` for dashboard projection. The snapshot exists because
+the dashboard needs current counters and queue depths without depending on a
+specific metrics exporter.
+
+HTTP request handling uses `UseGatewayRequestLoggingScope()` to attach common
+structured log fields when request metadata is present:
+
+- `SessionId`,
+- `ClientIdentity`,
+- `WorkerProcessId`,
+- `CorrelationId`,
+- `CommandMethod`.
+
+`GatewayLogRedactor` redacts API key secrets and command values before they are
+added to log state. Value logging remains opt-in and redacted by default so
+secured writes, authentication commands, and ordinary tag values do not leak
+through diagnostics.
+
 ## Configuration
 
 Suggested configuration shape:

docs/mxaccess-worker-instance-design.md

@@ -26,6 +26,33 @@ Style guides:
 - [C# Style Guide](./style-guides/CSharpStyleGuide.md)
 - [Protobuf Style Guide](./style-guides/ProtobufStyleGuide.md)
 
+## Build And Test
+
+Build the SDK-style worker project with the .NET SDK MSBuild entry point. The
+project targets .NET Framework 4.8, but the SDK resolver comes from the .NET SDK
+installation:
+
+```powershell
+dotnet msbuild src\MxGateway.Worker\MxGateway.Worker.csproj /restore /p:Configuration=Debug /p:Platform=x86
+```
+
+`docs/toolchain-links.md` records the Visual Studio MSBuild executable for
+classic .NET Framework and COM interop builds:
+
+```powershell
+& "C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\MSBuild\Current\Bin\MSBuild.exe" src\MxGateway.Worker\MxGateway.Worker.csproj /p:Configuration=Debug /p:Platform=x86
+```
+
+Run the worker tests with the same platform target:
+
+```powershell
+dotnet test src\MxGateway.Worker.Tests\MxGateway.Worker.Tests.csproj -p:Platform=x86
+```
+
+The only MXAccess interop reference belongs in `MxGateway.Worker`. Gateway and
+test projects may reference the worker project for metadata and scaffold tests,
+but they must not reference `ArchestrA.MXAccess.dll` directly.
+
 ## Responsibilities
 
 The worker owns:
@@ -87,6 +114,21 @@ Startup sequence:
 If validation fails before MXAccess creation, exit quickly with a non-zero exit
 code. If MXAccess creation fails, send `WorkerFault` when possible and exit.
 
+The bootstrap layer returns structured exit codes before it creates pipes,
+starts the STA, or touches MXAccess:
+
+| Exit code | Name | Meaning |
+|-----------|------|---------|
+| `0` | `Success` | Required bootstrap options are valid. |
+| `1` | `UnexpectedFailure` | A non-bootstrap exception reaches the process boundary. |
+| `2` | `InvalidArguments` | Required arguments are missing or unknown arguments are present. |
+| `3` | `InvalidProtocolVersion` | `--protocol-version` is not numeric or does not match the supported worker protocol. |
+| `4` | `MissingNonce` | `MXGATEWAY_WORKER_NONCE` is absent or empty. |
+
+Bootstrap logs use `WorkerConsoleLogger` key/value output. `WorkerLogRedactor`
+redacts fields whose names indicate nonce, secret, password, token,
+credential, or API key values before the message is written.
+
 ## Internal Components
 
 ```text

gateway.md

@@ -45,6 +45,10 @@ Detailed follow-up docs:
 - `docs/gateway-process-design.md` covers the .NET 10 gateway process,
   session manager, worker supervision, gRPC API, event streaming, fault model,
   security, observability, and test strategy.
+- `docs/WorkerFrameProtocol.md` covers the gateway-side named-pipe frame
+  reader/writer and `WorkerEnvelope` validation rules.
+- `docs/WorkerProcessLauncher.md` covers worker executable validation, process
+  launch arguments, nonce handling, and startup cleanup behavior.
 - `docs/mxaccess-worker-instance-design.md` covers each .NET Framework 4.8 x86
   MXAccess worker instance, including STA ownership, message pumping, COM
   lifetime, command dispatch, event sinks, conversion, and shutdown.
@@ -97,6 +101,13 @@ Responsibilities:
 
 The gateway must never instantiate or call MXAccess directly.
 
+The gateway observability foundation lives in `MxGateway.Server.Diagnostics`
+and `MxGateway.Server.Metrics`. Structured logging scopes carry session,
+worker, correlation, command, and client identity fields with redaction applied
+before values enter log state. `GatewayMetrics` exposes counters, gauges, and
+histograms through .NET `Meter` and a snapshot API that dashboard services can
+project without binding to a metrics exporter.
+
 ### Worker Process
 
 Runtime:

src/MxGateway.Contracts/MxGateway.Contracts.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net10.0</TargetFramework>
+    <TargetFrameworks>net10.0;net48</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
@@ -17,6 +17,7 @@
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>
+    <PackageReference Include="System.Runtime.CompilerServices.Unsafe" Version="6.1.2" />
   </ItemGroup>
 
 </Project>

src/MxGateway.Server/Diagnostics/GatewayLogRedactor.cs

@@ -0,0 +1,78 @@
+namespace MxGateway.Server.Diagnostics;
+
+public static class GatewayLogRedactor
+{
+    public const string RedactedValue = "[redacted]";
+
+    private static readonly HashSet<string> SensitiveCommandMethods = new(StringComparer.OrdinalIgnoreCase)
+    {
+        "AuthenticateUser",
+        "WriteSecured",
+        "WriteSecured2"
+    };
+
+    public static bool IsCredentialBearingCommand(string? commandMethod)
+    {
+        return commandMethod is not null
+            && SensitiveCommandMethods.Contains(commandMethod);
+    }
+
+    public static string? RedactApiKey(string? authorizationHeader)
+    {
+        if (string.IsNullOrWhiteSpace(authorizationHeader))
+        {
+            return authorizationHeader;
+        }
+
+        const string bearerPrefix = "Bearer ";
+        if (!authorizationHeader.StartsWith(bearerPrefix, StringComparison.OrdinalIgnoreCase))
+        {
+            return RedactedValue;
+        }
+
+        string token = authorizationHeader[bearerPrefix.Length..].Trim();
+
+        if (!token.StartsWith("mxgw_", StringComparison.OrdinalIgnoreCase))
+        {
+            return $"{bearerPrefix}{RedactedValue}";
+        }
+
+        string[] tokenParts = token.Split('_', 3, StringSplitOptions.RemoveEmptyEntries);
+        if (tokenParts.Length < 2)
+        {
+            return $"{bearerPrefix}mxgw_{RedactedValue}";
+        }
+
+        return $"{bearerPrefix}mxgw_{tokenParts[1]}_{RedactedValue}";
+    }
+
+    public static string? RedactClientIdentity(string? clientIdentity)
+    {
+        if (string.IsNullOrWhiteSpace(clientIdentity))
+        {
+            return clientIdentity;
+        }
+
+        return clientIdentity.Contains("mxgw_", StringComparison.OrdinalIgnoreCase)
+            ? RedactApiKey(clientIdentity)
+            : clientIdentity;
+    }
+
+    public static object? RedactCommandValue(
+        string? commandMethod,
+        object? value,
+        bool valueLoggingEnabled = false)
+    {
+        if (value is null)
+        {
+            return null;
+        }
+
+        if (!valueLoggingEnabled || IsCredentialBearingCommand(commandMethod))
+        {
+            return RedactedValue;
+        }
+
+        return value;
+    }
+}

src/MxGateway.Server/Diagnostics/GatewayLogScope.cs

@@ -0,0 +1,33 @@
+namespace MxGateway.Server.Diagnostics;
+
+public sealed record GatewayLogScope(
+    string? SessionId = null,
+    int? WorkerProcessId = null,
+    ulong? CorrelationId = null,
+    string? CommandMethod = null,
+    string? ClientIdentity = null)
+{
+    public IReadOnlyDictionary<string, object?> ToDictionary()
+    {
+        Dictionary<string, object?> values = [];
+
+        AddIfPresent(values, "SessionId", SessionId);
+        AddIfPresent(values, "WorkerProcessId", WorkerProcessId);
+        AddIfPresent(values, "CorrelationId", CorrelationId);
+        AddIfPresent(values, "CommandMethod", CommandMethod);
+        AddIfPresent(values, "ClientIdentity", GatewayLogRedactor.RedactClientIdentity(ClientIdentity));
+
+        return values;
+    }
+
+    private static void AddIfPresent(
+        Dictionary<string, object?> values,
+        string key,
+        object? value)
+    {
+        if (value is not null)
+        {
+            values[key] = value;
+        }
+    }
+}

src/MxGateway.Server/Diagnostics/GatewayLoggerExtensions.cs

@@ -0,0 +1,16 @@
+using Microsoft.Extensions.Logging;
+
+namespace MxGateway.Server.Diagnostics;
+
+public static class GatewayLoggerExtensions
+{
+    public static IDisposable? BeginGatewayScope(
+        this ILogger logger,
+        GatewayLogScope scope)
+    {
+        ArgumentNullException.ThrowIfNull(logger);
+        ArgumentNullException.ThrowIfNull(scope);
+
+        return logger.BeginScope(scope.ToDictionary());
+    }
+}

src/MxGateway.Server/Diagnostics/GatewayRequestLoggingMiddlewareExtensions.cs

@@ -0,0 +1,57 @@
+using Microsoft.Extensions.Primitives;
+
+namespace MxGateway.Server.Diagnostics;
+
+public static class GatewayRequestLoggingMiddlewareExtensions
+{
+    public const string SessionIdHeaderName = "x-session-id";
+    public const string WorkerProcessIdHeaderName = "x-worker-process-id";
+    public const string CorrelationIdHeaderName = "x-correlation-id";
+    public const string CommandMethodHeaderName = "x-command-method";
+
+    public static IApplicationBuilder UseGatewayRequestLoggingScope(this IApplicationBuilder app)
+    {
+        ArgumentNullException.ThrowIfNull(app);
+
+        return app.Use(async (context, next) =>
+        {
+            ILogger logger = context.RequestServices
+                .GetRequiredService<ILoggerFactory>()
+                .CreateLogger("MxGateway.Request");
+
+            using IDisposable? scope = logger.BeginGatewayScope(new GatewayLogScope(
+                SessionId: ReadHeader(context, SessionIdHeaderName),
+                WorkerProcessId: ReadInt32Header(context, WorkerProcessIdHeaderName),
+                CorrelationId: ReadUInt64Header(context, CorrelationIdHeaderName),
+                CommandMethod: ReadHeader(context, CommandMethodHeaderName),
+                ClientIdentity: ReadHeader(context, "authorization")));
+
+            await next(context);
+        });
+    }
+
+    private static string? ReadHeader(HttpContext context, string headerName)
+    {
+        return context.Request.Headers.TryGetValue(headerName, out StringValues values)
+            ? values.ToString()
+            : null;
+    }
+
+    private static int? ReadInt32Header(HttpContext context, string headerName)
+    {
+        string? value = ReadHeader(context, headerName);
+
+        return int.TryParse(value, out int parsedValue)
+            ? parsedValue
+            : null;
+    }
+
+    private static ulong? ReadUInt64Header(HttpContext context, string headerName)
+    {
+        string? value = ReadHeader(context, headerName);
+
+        return ulong.TryParse(value, out ulong parsedValue)
+            ? parsedValue
+            : null;
+    }
+}

src/MxGateway.Server/GatewayApplication.cs

@@ -1,5 +1,9 @@
 using MxGateway.Contracts;
 using MxGateway.Server.Configuration;
+using MxGateway.Server.Diagnostics;
+using MxGateway.Server.Metrics;
+using MxGateway.Server.Security.Authentication;
+using MxGateway.Server.Workers;
 
 namespace MxGateway.Server;
 
@@ -10,6 +14,7 @@ public static class GatewayApplication
         WebApplicationBuilder builder = CreateBuilder(args);
         WebApplication app = builder.Build();
 
+        app.UseGatewayRequestLoggingScope();
         app.MapGatewayEndpoints();
 
         return app;
@@ -20,7 +25,10 @@ public static class GatewayApplication
         WebApplicationBuilder builder = WebApplication.CreateBuilder(args);
 
         builder.Services.AddGatewayConfiguration();
+        builder.Services.AddSqliteAuthStore();
         builder.Services.AddHealthChecks();
+        builder.Services.AddSingleton<GatewayMetrics>();
+        builder.Services.AddWorkerProcessLauncher();
 
         return builder;
     }

src/MxGateway.Server/Metrics/GatewayMetrics.cs

@@ -0,0 +1,306 @@
+using System.Diagnostics.Metrics;
+
+namespace MxGateway.Server.Metrics;
+
+public sealed class GatewayMetrics : IDisposable
+{
+    public const string MeterName = "MxGateway.Server";
+
+    private readonly object _syncRoot = new();
+    private readonly Meter _meter;
+    private readonly Counter<long> _sessionsOpenedCounter;
+    private readonly Counter<long> _sessionsClosedCounter;
+    private readonly Counter<long> _commandsStartedCounter;
+    private readonly Counter<long> _commandsSucceededCounter;
+    private readonly Counter<long> _commandsFailedCounter;
+    private readonly Counter<long> _eventsReceivedCounter;
+    private readonly Counter<long> _queueOverflowsCounter;
+    private readonly Counter<long> _faultsCounter;
+    private readonly Counter<long> _workerKillsCounter;
+    private readonly Counter<long> _workerExitsCounter;
+    private readonly Counter<long> _heartbeatFailuresCounter;
+    private readonly Counter<long> _streamDisconnectsCounter;
+    private readonly Histogram<double> _workerStartupLatencyHistogram;
+    private readonly Histogram<double> _commandLatencyHistogram;
+    private readonly Histogram<double> _eventStreamSendLatencyHistogram;
+    private readonly Dictionary<string, long> _commandFailuresByMethod = new(StringComparer.OrdinalIgnoreCase);
+    private readonly Dictionary<string, long> _eventsByFamily = new(StringComparer.OrdinalIgnoreCase);
+
+    private int _openSessions;
+    private int _workersRunning;
+    private int _eventQueueDepth;
+    private long _sessionsOpened;
+    private long _sessionsClosed;
+    private long _commandsStarted;
+    private long _commandsSucceeded;
+    private long _commandsFailed;
+    private long _eventsReceived;
+    private long _queueOverflows;
+    private long _faults;
+    private long _workerKills;
+    private long _workerExits;
+    private long _heartbeatFailures;
+    private long _streamDisconnects;
+    private bool _disposed;
+
+    public GatewayMetrics()
+    {
+        _meter = new Meter(MeterName, typeof(GatewayMetrics).Assembly.GetName().Version?.ToString());
+        _sessionsOpenedCounter = _meter.CreateCounter<long>("mxgateway.sessions.opened");
+        _sessionsClosedCounter = _meter.CreateCounter<long>("mxgateway.sessions.closed");
+        _commandsStartedCounter = _meter.CreateCounter<long>("mxgateway.commands.started");
+        _commandsSucceededCounter = _meter.CreateCounter<long>("mxgateway.commands.succeeded");
+        _commandsFailedCounter = _meter.CreateCounter<long>("mxgateway.commands.failed");
+        _eventsReceivedCounter = _meter.CreateCounter<long>("mxgateway.events.received");
+        _queueOverflowsCounter = _meter.CreateCounter<long>("mxgateway.queues.overflows");
+        _faultsCounter = _meter.CreateCounter<long>("mxgateway.faults");
+        _workerKillsCounter = _meter.CreateCounter<long>("mxgateway.workers.killed");
+        _workerExitsCounter = _meter.CreateCounter<long>("mxgateway.workers.exited");
+        _heartbeatFailuresCounter = _meter.CreateCounter<long>("mxgateway.heartbeats.failed");
+        _streamDisconnectsCounter = _meter.CreateCounter<long>("mxgateway.grpc.streams.disconnected");
+        _workerStartupLatencyHistogram = _meter.CreateHistogram<double>("mxgateway.workers.startup.duration", "ms");
+        _commandLatencyHistogram = _meter.CreateHistogram<double>("mxgateway.commands.duration", "ms");
+        _eventStreamSendLatencyHistogram = _meter.CreateHistogram<double>("mxgateway.events.stream_send.duration", "ms");
+
+        _meter.CreateObservableGauge("mxgateway.sessions.open", GetOpenSessions);
+        _meter.CreateObservableGauge("mxgateway.workers.running", GetWorkersRunning);
+        _meter.CreateObservableGauge("mxgateway.events.queue.depth", GetEventQueueDepth);
+    }
+
+    public void SessionOpened()
+    {
+        lock (_syncRoot)
+        {
+            _openSessions++;
+            _sessionsOpened++;
+        }
+
+        _sessionsOpenedCounter.Add(1);
+    }
+
+    public void SessionClosed()
+    {
+        lock (_syncRoot)
+        {
+            if (_openSessions > 0)
+            {
+                _openSessions--;
+            }
+
+            _sessionsClosed++;
+        }
+
+        _sessionsClosedCounter.Add(1);
+    }
+
+    public void WorkerStarted(TimeSpan startupDuration)
+    {
+        lock (_syncRoot)
+        {
+            _workersRunning++;
+        }
+
+        _workerStartupLatencyHistogram.Record(startupDuration.TotalMilliseconds);
+    }
+
+    public void WorkerStopped(string reason)
+    {
+        lock (_syncRoot)
+        {
+            if (_workersRunning > 0)
+            {
+                _workersRunning--;
+            }
+
+            _workerExits++;
+        }
+
+        _workerExitsCounter.Add(1, new KeyValuePair<string, object?>("reason", reason));
+    }
+
+    public void WorkerKilled(string reason)
+    {
+        lock (_syncRoot)
+        {
+            _workerKills++;
+        }
+
+        _workerKillsCounter.Add(1, new KeyValuePair<string, object?>("reason", reason));
+    }
+
+    public void CommandStarted(string method)
+    {
+        lock (_syncRoot)
+        {
+            _commandsStarted++;
+        }
+
+        _commandsStartedCounter.Add(1, new KeyValuePair<string, object?>("method", method));
+    }
+
+    public void CommandSucceeded(string method, TimeSpan duration)
+    {
+        lock (_syncRoot)
+        {
+            _commandsSucceeded++;
+        }
+
+        KeyValuePair<string, object?> methodTag = new("method", method);
+        _commandsSucceededCounter.Add(1, methodTag);
+        _commandLatencyHistogram.Record(duration.TotalMilliseconds, methodTag);
+    }
+
+    public void CommandFailed(string method, string category, TimeSpan duration)
+    {
+        lock (_syncRoot)
+        {
+            _commandsFailed++;
+            Increment(_commandFailuresByMethod, method);
+        }
+
+        KeyValuePair<string, object?> methodTag = new("method", method);
+        KeyValuePair<string, object?> categoryTag = new("category", category);
+        _commandsFailedCounter.Add(1, methodTag, categoryTag);
+        _commandLatencyHistogram.Record(duration.TotalMilliseconds, methodTag, categoryTag);
+    }
+
+    public void EventReceived(string sessionId, string family)
+    {
+        lock (_syncRoot)
+        {
+            _eventsReceived++;
+            Increment(_eventsByFamily, family);
+        }
+
+        _eventsReceivedCounter.Add(
+            1,
+            new KeyValuePair<string, object?>("session_id", sessionId),
+            new KeyValuePair<string, object?>("family", family));
+    }
+
+    public void RecordEventStreamSend(string family, TimeSpan duration)
+    {
+        _eventStreamSendLatencyHistogram.Record(
+            duration.TotalMilliseconds,
+            new KeyValuePair<string, object?>("family", family));
+    }
+
+    public void SetEventQueueDepth(int depth)
+    {
+        if (depth < 0)
+        {
+            throw new ArgumentOutOfRangeException(nameof(depth), depth, "Queue depth cannot be negative.");
+        }
+
+        lock (_syncRoot)
+        {
+            _eventQueueDepth = depth;
+        }
+    }
+
+    public void QueueOverflow(string queueName)
+    {
+        lock (_syncRoot)
+        {
+            _queueOverflows++;
+        }
+
+        _queueOverflowsCounter.Add(1, new KeyValuePair<string, object?>("queue", queueName));
+    }
+
+    public void Fault(string category)
+    {
+        lock (_syncRoot)
+        {
+            _faults++;
+        }
+
+        _faultsCounter.Add(1, new KeyValuePair<string, object?>("category", category));
+    }
+
+    public void HeartbeatFailed(string sessionId)
+    {
+        lock (_syncRoot)
+        {
+            _heartbeatFailures++;
+        }
+
+        _heartbeatFailuresCounter.Add(1, new KeyValuePair<string, object?>("session_id", sessionId));
+    }
+
+    public void StreamDisconnected(string reason)
+    {
+        lock (_syncRoot)
+        {
+            _streamDisconnects++;
+        }
+
+        _streamDisconnectsCounter.Add(1, new KeyValuePair<string, object?>("reason", reason));
+    }
+
+    public GatewayMetricsSnapshot GetSnapshot()
+    {
+        lock (_syncRoot)
+        {
+            return new GatewayMetricsSnapshot(
+                OpenSessions: _openSessions,
+                WorkersRunning: _workersRunning,
+                EventQueueDepth: _eventQueueDepth,
+                SessionsOpened: _sessionsOpened,
+                SessionsClosed: _sessionsClosed,
+                CommandsStarted: _commandsStarted,
+                CommandsSucceeded: _commandsSucceeded,
+                CommandsFailed: _commandsFailed,
+                EventsReceived: _eventsReceived,
+                QueueOverflows: _queueOverflows,
+                Faults: _faults,
+                WorkerKills: _workerKills,
+                WorkerExits: _workerExits,
+                HeartbeatFailures: _heartbeatFailures,
+                StreamDisconnects: _streamDisconnects,
+                CommandFailuresByMethod: new Dictionary<string, long>(_commandFailuresByMethod, StringComparer.OrdinalIgnoreCase),
+                EventsByFamily: new Dictionary<string, long>(_eventsByFamily, StringComparer.OrdinalIgnoreCase));
+        }
+    }
+
+    public void Dispose()
+    {
+        if (_disposed)
+        {
+            return;
+        }
+
+        _meter.Dispose();
+        _disposed = true;
+    }
+
+    private int GetOpenSessions()
+    {
+        lock (_syncRoot)
+        {
+            return _openSessions;
+        }
+    }
+
+    private int GetWorkersRunning()
+    {
+        lock (_syncRoot)
+        {
+            return _workersRunning;
+        }
+    }
+
+    private int GetEventQueueDepth()
+    {
+        lock (_syncRoot)
+        {
+            return _eventQueueDepth;
+        }
+    }
+
+    private static void Increment(Dictionary<string, long> values, string key)
+    {
+        values.TryGetValue(key, out long currentValue);
+        values[key] = currentValue + 1;
+    }
+}

src/MxGateway.Server/Metrics/GatewayMetricsSnapshot.cs

@@ -0,0 +1,20 @@
+namespace MxGateway.Server.Metrics;
+
+public sealed record GatewayMetricsSnapshot(
+    int OpenSessions,
+    int WorkersRunning,
+    int EventQueueDepth,
+    long SessionsOpened,
+    long SessionsClosed,
+    long CommandsStarted,
+    long CommandsSucceeded,
+    long CommandsFailed,
+    long EventsReceived,
+    long QueueOverflows,
+    long Faults,
+    long WorkerKills,
+    long WorkerExits,
+    long HeartbeatFailures,
+    long StreamDisconnects,
+    IReadOnlyDictionary<string, long> CommandFailuresByMethod,
+    IReadOnlyDictionary<string, long> EventsByFamily);

src/MxGateway.Server/MxGateway.Server.csproj

@@ -4,6 +4,10 @@
     <TargetFramework>net10.0</TargetFramework>
   </PropertyGroup>
 
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Data.Sqlite" Version="10.0.7" />
+  </ItemGroup>
+
   <ItemGroup>
     <ProjectReference Include="..\MxGateway.Contracts\MxGateway.Contracts.csproj" />
   </ItemGroup>

src/MxGateway.Server/Program.cs

@@ -1,7 +1,43 @@
 using MxGateway.Server;
+using MxGateway.Server.Configuration;
+using MxGateway.Server.Security.Authentication;
 
-var app = GatewayApplication.Build(args);
+ApiKeyAdminParseResult apiKeyAdminCommand = ApiKeyAdminCommandLineParser.Parse(args);
+if (apiKeyAdminCommand.IsApiKeyCommand)
+{
+    if (apiKeyAdminCommand.Command is null)
+    {
+        await Console.Error.WriteLineAsync(apiKeyAdminCommand.Error);
+        return 2;
+    }
+
+    WebApplicationBuilder builder = GatewayApplication.CreateBuilder([]);
+    ApplyApiKeyAdminOverrides(builder.Configuration, apiKeyAdminCommand.Command);
+    await using WebApplication cliApp = builder.Build();
+    await using AsyncServiceScope scope = cliApp.Services.CreateAsyncScope();
+
+    ApiKeyAdminCliRunner runner = scope.ServiceProvider.GetRequiredService<ApiKeyAdminCliRunner>();
+
+    return await runner.RunAsync(apiKeyAdminCommand.Command, Console.Out, CancellationToken.None);
+}
+
+WebApplication app = GatewayApplication.Build(args);
 
 app.Run();
 
+return 0;
+
+static void ApplyApiKeyAdminOverrides(IConfiguration configuration, ApiKeyAdminCommand command)
+{
+    if (!string.IsNullOrWhiteSpace(command.SqlitePath))
+    {
+        configuration[$"{GatewayOptions.SectionName}:Authentication:SqlitePath"] = command.SqlitePath;
+    }
+
+    if (!string.IsNullOrWhiteSpace(command.Pepper))
+    {
+        configuration["MxGateway:ApiKeyPepper"] = command.Pepper;
+    }
+}
+
 public partial class Program;

src/MxGateway.Server/Security/Authentication/ApiKeyAdminCliRunner.cs

@@ -0,0 +1,180 @@
+using System.Text.Json;
+
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed class ApiKeyAdminCliRunner(
+    IAuthStoreMigrator migrator,
+    IApiKeyAdminStore adminStore,
+    IApiKeyAuditStore auditStore,
+    IApiKeySecretHasher hasher)
+{
+    private static readonly JsonSerializerOptions JsonOptions = new()
+    {
+        WriteIndented = true
+    };
+
+    public async Task<int> RunAsync(
+        ApiKeyAdminCommand command,
+        TextWriter output,
+        CancellationToken cancellationToken)
+    {
+        ApiKeyAdminOutput result = command.Kind switch
+        {
+            ApiKeyAdminCommandKind.InitDb => await InitDbAsync(cancellationToken).ConfigureAwait(false),
+            ApiKeyAdminCommandKind.CreateKey => await CreateKeyAsync(command, cancellationToken).ConfigureAwait(false),
+            ApiKeyAdminCommandKind.ListKeys => await ListKeysAsync(cancellationToken).ConfigureAwait(false),
+            ApiKeyAdminCommandKind.RevokeKey => await RevokeKeyAsync(command, cancellationToken).ConfigureAwait(false),
+            ApiKeyAdminCommandKind.RotateKey => await RotateKeyAsync(command, cancellationToken).ConfigureAwait(false),
+            _ => throw new InvalidOperationException($"Unsupported API key command '{command.Kind}'.")
+        };
+
+        await WriteOutputAsync(command, result, output).ConfigureAwait(false);
+
+        return 0;
+    }
+
+    private async Task<ApiKeyAdminOutput> InitDbAsync(CancellationToken cancellationToken)
+    {
+        await migrator.MigrateAsync(cancellationToken).ConfigureAwait(false);
+        await AppendAuditAsync(null, "init-db", null, cancellationToken).ConfigureAwait(false);
+
+        return new ApiKeyAdminOutput("init-db", "initialized", null, []);
+    }
+
+    private async Task<ApiKeyAdminOutput> CreateKeyAsync(
+        ApiKeyAdminCommand command,
+        CancellationToken cancellationToken)
+    {
+        await migrator.MigrateAsync(cancellationToken).ConfigureAwait(false);
+
+        string keyId = Required(command.KeyId);
+        string secret = ApiKeySecretGenerator.Generate();
+        string apiKey = FormatApiKey(keyId, secret);
+
+        await adminStore.CreateAsync(
+                new ApiKeyCreateRequest(
+                    KeyId: keyId,
+                    KeyPrefix: $"mxgw_{keyId}",
+                    SecretHash: hasher.HashSecret(secret),
+                    DisplayName: Required(command.DisplayName),
+                    Scopes: command.Scopes,
+                    CreatedUtc: DateTimeOffset.UtcNow),
+                cancellationToken)
+            .ConfigureAwait(false);
+        await AppendAuditAsync(keyId, "create-key", null, cancellationToken).ConfigureAwait(false);
+
+        return new ApiKeyAdminOutput("create-key", "created", apiKey, []);
+    }
+
+    private async Task<ApiKeyAdminOutput> ListKeysAsync(CancellationToken cancellationToken)
+    {
+        await migrator.MigrateAsync(cancellationToken).ConfigureAwait(false);
+        IReadOnlyList<ApiKeyRecord> keys = await adminStore.ListAsync(cancellationToken).ConfigureAwait(false);
+        await AppendAuditAsync(null, "list-keys", null, cancellationToken).ConfigureAwait(false);
+
+        return new ApiKeyAdminOutput(
+            "list-keys",
+            "ok",
+            null,
+            keys.Select(ToListedKey).ToArray());
+    }
+
+    private async Task<ApiKeyAdminOutput> RevokeKeyAsync(
+        ApiKeyAdminCommand command,
+        CancellationToken cancellationToken)
+    {
+        await migrator.MigrateAsync(cancellationToken).ConfigureAwait(false);
+
+        string keyId = Required(command.KeyId);
+        bool revoked = await adminStore.RevokeAsync(keyId, DateTimeOffset.UtcNow, cancellationToken)
+            .ConfigureAwait(false);
+
+        await AppendAuditAsync(keyId, "revoke-key", revoked ? "revoked" : "not-found-or-already-revoked", cancellationToken)
+            .ConfigureAwait(false);
+
+        return new ApiKeyAdminOutput("revoke-key", revoked ? "revoked" : "not-found-or-already-revoked", null, []);
+    }
+
+    private async Task<ApiKeyAdminOutput> RotateKeyAsync(
+        ApiKeyAdminCommand command,
+        CancellationToken cancellationToken)
+    {
+        await migrator.MigrateAsync(cancellationToken).ConfigureAwait(false);
+
+        string keyId = Required(command.KeyId);
+        string secret = ApiKeySecretGenerator.Generate();
+        string apiKey = FormatApiKey(keyId, secret);
+
+        bool rotated = await adminStore.RotateAsync(keyId, hasher.HashSecret(secret), DateTimeOffset.UtcNow, cancellationToken)
+            .ConfigureAwait(false);
+
+        await AppendAuditAsync(keyId, "rotate-key", rotated ? "rotated" : "not-found", cancellationToken)
+            .ConfigureAwait(false);
+
+        return new ApiKeyAdminOutput("rotate-key", rotated ? "rotated" : "not-found", rotated ? apiKey : null, []);
+    }
+
+    private static async Task WriteOutputAsync(
+        ApiKeyAdminCommand command,
+        ApiKeyAdminOutput result,
+        TextWriter output)
+    {
+        if (command.Json)
+        {
+            await output.WriteLineAsync(JsonSerializer.Serialize(result, JsonOptions)).ConfigureAwait(false);
+            return;
+        }
+
+        await output.WriteLineAsync($"{result.Command}: {result.Status}").ConfigureAwait(false);
+
+        if (result.ApiKey is not null)
+        {
+            await output.WriteLineAsync($"API key: {result.ApiKey}").ConfigureAwait(false);
+        }
+
+        foreach (ApiKeyAdminListedKey key in result.Keys)
+        {
+            string revoked = key.RevokedUtc is null ? "active" : "revoked";
+            await output.WriteLineAsync($"{key.KeyId}\t{key.DisplayName}\t{revoked}\t{string.Join(',', key.Scopes)}")
+                .ConfigureAwait(false);
+        }
+    }
+
+    private async Task AppendAuditAsync(
+        string? keyId,
+        string eventType,
+        string? details,
+        CancellationToken cancellationToken)
+    {
+        await auditStore.AppendAsync(
+                new ApiKeyAuditEntry(
+                    KeyId: keyId,
+                    EventType: eventType,
+                    RemoteAddress: null,
+                    Details: details),
+                cancellationToken)
+            .ConfigureAwait(false);
+    }
+
+    private static ApiKeyAdminListedKey ToListedKey(ApiKeyRecord key)
+    {
+        return new ApiKeyAdminListedKey(
+            KeyId: key.KeyId,
+            KeyPrefix: key.KeyPrefix,
+            DisplayName: key.DisplayName,
+            Scopes: key.Scopes,
+            CreatedUtc: key.CreatedUtc,
+            LastUsedUtc: key.LastUsedUtc,
+            RevokedUtc: key.RevokedUtc);
+    }
+
+    private static string FormatApiKey(string keyId, string secret)
+    {
+        return $"mxgw_{keyId}_{secret}";
+    }
+
+    private static string Required(string? value)
+    {
+        return value ?? throw new InvalidOperationException("Required command value was not provided.");
+    }
+}

src/MxGateway.Server/Security/Authentication/ApiKeyAdminCommand.cs

@@ -0,0 +1,10 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed record ApiKeyAdminCommand(
+    ApiKeyAdminCommandKind Kind,
+    bool Json,
+    string? SqlitePath,
+    string? Pepper,
+    string? KeyId,
+    string? DisplayName,
+    IReadOnlySet<string> Scopes);

src/MxGateway.Server/Security/Authentication/ApiKeyAdminCommandKind.cs

@@ -0,0 +1,10 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public enum ApiKeyAdminCommandKind
+{
+    InitDb,
+    CreateKey,
+    ListKeys,
+    RevokeKey,
+    RotateKey
+}

src/MxGateway.Server/Security/Authentication/ApiKeyAdminCommandLineParser.cs

@@ -0,0 +1,159 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public static class ApiKeyAdminCommandLineParser
+{
+    public static ApiKeyAdminParseResult Parse(IReadOnlyList<string> args)
+    {
+        if (args.Count == 0 || !string.Equals(args[0], "apikey", StringComparison.OrdinalIgnoreCase))
+        {
+            return ApiKeyAdminParseResult.NotApiKeyCommand();
+        }
+
+        if (args.Count < 2)
+        {
+            return ApiKeyAdminParseResult.Fail("Missing apikey subcommand.");
+        }
+
+        if (!TryParseKind(args[1], out ApiKeyAdminCommandKind kind))
+        {
+            return ApiKeyAdminParseResult.Fail($"Unknown apikey subcommand '{args[1]}'.");
+        }
+
+        Dictionary<string, string?> options = new(StringComparer.OrdinalIgnoreCase);
+        bool json = false;
+
+        for (int index = 2; index < args.Count; index++)
+        {
+            string arg = args[index];
+            if (string.Equals(arg, "--json", StringComparison.OrdinalIgnoreCase))
+            {
+                json = true;
+                continue;
+            }
+
+            if (!arg.StartsWith("--", StringComparison.Ordinal))
+            {
+                return ApiKeyAdminParseResult.Fail($"Unexpected argument '{arg}'.");
+            }
+
+            string name = arg[2..];
+            string? value;
+
+            int equalsIndex = name.IndexOf('=', StringComparison.Ordinal);
+            if (equalsIndex >= 0)
+            {
+                value = name[(equalsIndex + 1)..];
+                name = name[..equalsIndex];
+            }
+            else
+            {
+                if (index + 1 >= args.Count || args[index + 1].StartsWith("--", StringComparison.Ordinal))
+                {
+                    return ApiKeyAdminParseResult.Fail($"Option '--{name}' requires a value.");
+                }
+
+                value = args[++index];
+            }
+
+            options[name] = value;
+        }
+
+        string? keyId = GetOption(options, "key-id");
+        string? displayName = GetOption(options, "display-name");
+        IReadOnlySet<string> scopes = ParseScopes(GetOption(options, "scopes"));
+
+        string? validationError = Validate(kind, keyId, displayName);
+        if (validationError is not null)
+        {
+            return ApiKeyAdminParseResult.Fail(validationError);
+        }
+
+        return ApiKeyAdminParseResult.Success(new ApiKeyAdminCommand(
+            Kind: kind,
+            Json: json,
+            SqlitePath: GetOption(options, "sqlite-path"),
+            Pepper: GetOption(options, "pepper"),
+            KeyId: keyId,
+            DisplayName: displayName,
+            Scopes: scopes));
+    }
+
+    private static bool TryParseKind(string value, out ApiKeyAdminCommandKind kind)
+    {
+        switch (value.ToLowerInvariant())
+        {
+            case "init-db":
+                kind = ApiKeyAdminCommandKind.InitDb;
+                return true;
+            case "create-key":
+                kind = ApiKeyAdminCommandKind.CreateKey;
+                return true;
+            case "list-keys":
+                kind = ApiKeyAdminCommandKind.ListKeys;
+                return true;
+            case "revoke-key":
+                kind = ApiKeyAdminCommandKind.RevokeKey;
+                return true;
+            case "rotate-key":
+                kind = ApiKeyAdminCommandKind.RotateKey;
+                return true;
+            default:
+                kind = default;
+                return false;
+        }
+    }
+
+    private static string? Validate(ApiKeyAdminCommandKind kind, string? keyId, string? displayName)
+    {
+        if (kind is ApiKeyAdminCommandKind.CreateKey or ApiKeyAdminCommandKind.RevokeKey or ApiKeyAdminCommandKind.RotateKey
+            && string.IsNullOrWhiteSpace(keyId))
+        {
+            return $"Subcommand '{KindName(kind)}' requires --key-id.";
+        }
+
+        if (!string.IsNullOrWhiteSpace(keyId) && !IsValidKeyId(keyId))
+        {
+            return "API key id may contain only letters, numbers, periods, and hyphens.";
+        }
+
+        if (kind == ApiKeyAdminCommandKind.CreateKey && string.IsNullOrWhiteSpace(displayName))
+        {
+            return "Subcommand 'create-key' requires --display-name.";
+        }
+
+        return null;
+    }
+
+    private static string KindName(ApiKeyAdminCommandKind kind)
+    {
+        return kind switch
+        {
+            ApiKeyAdminCommandKind.InitDb => "init-db",
+            ApiKeyAdminCommandKind.CreateKey => "create-key",
+            ApiKeyAdminCommandKind.ListKeys => "list-keys",
+            ApiKeyAdminCommandKind.RevokeKey => "revoke-key",
+            ApiKeyAdminCommandKind.RotateKey => "rotate-key",
+            _ => kind.ToString()
+        };
+    }
+
+    private static bool IsValidKeyId(string keyId)
+    {
+        return keyId.All(character =>
+            char.IsAsciiLetterOrDigit(character)
+            || character is '.' or '-');
+    }
+
+    private static string? GetOption(Dictionary<string, string?> options, string name)
+    {
+        return options.TryGetValue(name, out string? value) ? value : null;
+    }
+
+    private static IReadOnlySet<string> ParseScopes(string? scopes)
+    {
+        return new HashSet<string>(
+            (scopes ?? string.Empty)
+                .Split(',', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries),
+            StringComparer.Ordinal);
+    }
+}

src/MxGateway.Server/Security/Authentication/ApiKeyAdminListedKey.cs

@@ -0,0 +1,10 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed record ApiKeyAdminListedKey(
+    string KeyId,
+    string KeyPrefix,
+    string DisplayName,
+    IReadOnlySet<string> Scopes,
+    DateTimeOffset CreatedUtc,
+    DateTimeOffset? LastUsedUtc,
+    DateTimeOffset? RevokedUtc);

src/MxGateway.Server/Security/Authentication/ApiKeyAdminOutput.cs

@@ -0,0 +1,7 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed record ApiKeyAdminOutput(
+    string Command,
+    string Status,
+    string? ApiKey,
+    IReadOnlyList<ApiKeyAdminListedKey> Keys);

src/MxGateway.Server/Security/Authentication/ApiKeyAdminParseResult.cs

@@ -0,0 +1,22 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed record ApiKeyAdminParseResult(
+    bool IsApiKeyCommand,
+    ApiKeyAdminCommand? Command,
+    string? Error)
+{
+    public static ApiKeyAdminParseResult NotApiKeyCommand()
+    {
+        return new ApiKeyAdminParseResult(false, null, null);
+    }
+
+    public static ApiKeyAdminParseResult Success(ApiKeyAdminCommand command)
+    {
+        return new ApiKeyAdminParseResult(true, command, null);
+    }
+
+    public static ApiKeyAdminParseResult Fail(string error)
+    {
+        return new ApiKeyAdminParseResult(true, null, error);
+    }
+}

src/MxGateway.Server/Security/Authentication/ApiKeyAuditEntry.cs

@@ -0,0 +1,7 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed record ApiKeyAuditEntry(
+    string? KeyId,
+    string EventType,
+    string? RemoteAddress,
+    string? Details);

src/MxGateway.Server/Security/Authentication/ApiKeyAuditRecord.cs

@@ -0,0 +1,9 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed record ApiKeyAuditRecord(
+    long AuditId,
+    string? KeyId,
+    string EventType,
+    string? RemoteAddress,
+    DateTimeOffset CreatedUtc,
+    string? Details);

src/MxGateway.Server/Security/Authentication/ApiKeyCreateRequest.cs

@@ -0,0 +1,9 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed record ApiKeyCreateRequest(
+    string KeyId,
+    string KeyPrefix,
+    byte[] SecretHash,
+    string DisplayName,
+    IReadOnlySet<string> Scopes,
+    DateTimeOffset CreatedUtc);

src/MxGateway.Server/Security/Authentication/ApiKeyIdentity.cs

@@ -0,0 +1,7 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed record ApiKeyIdentity(
+    string KeyId,
+    string KeyPrefix,
+    string DisplayName,
+    IReadOnlySet<string> Scopes);

src/MxGateway.Server/Security/Authentication/ApiKeyParser.cs

@@ -0,0 +1,45 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed class ApiKeyParser : IApiKeyParser
+{
+    private const string BearerPrefix = "Bearer ";
+    private const string TokenPrefix = "mxgw_";
+
+    public bool TryParseAuthorizationHeader(string? authorizationHeader, out ParsedApiKey? apiKey)
+    {
+        apiKey = null;
+
+        if (string.IsNullOrWhiteSpace(authorizationHeader)
+            || !authorizationHeader.StartsWith(BearerPrefix, StringComparison.OrdinalIgnoreCase))
+        {
+            return false;
+        }
+
+        string token = authorizationHeader[BearerPrefix.Length..].Trim();
+
+        if (!token.StartsWith(TokenPrefix, StringComparison.OrdinalIgnoreCase))
+        {
+            return false;
+        }
+
+        string keyPayload = token[TokenPrefix.Length..];
+        int separatorIndex = keyPayload.IndexOf('_', StringComparison.Ordinal);
+
+        if (separatorIndex <= 0 || separatorIndex == keyPayload.Length - 1)
+        {
+            return false;
+        }
+
+        string keyId = keyPayload[..separatorIndex];
+        string secret = keyPayload[(separatorIndex + 1)..];
+
+        if (string.IsNullOrWhiteSpace(keyId) || string.IsNullOrWhiteSpace(secret))
+        {
+            return false;
+        }
+
+        apiKey = new ParsedApiKey(keyId, secret);
+
+        return true;
+    }
+}

src/MxGateway.Server/Security/Authentication/ApiKeyPepperUnavailableException.cs

@@ -0,0 +1,4 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed class ApiKeyPepperUnavailableException(string pepperSecretName)
+    : InvalidOperationException($"API key pepper secret '{pepperSecretName}' is not configured.");

src/MxGateway.Server/Security/Authentication/ApiKeyRecord.cs

@@ -0,0 +1,11 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed record ApiKeyRecord(
+    string KeyId,
+    string KeyPrefix,
+    byte[] SecretHash,
+    string DisplayName,
+    IReadOnlySet<string> Scopes,
+    DateTimeOffset CreatedUtc,
+    DateTimeOffset? LastUsedUtc,
+    DateTimeOffset? RevokedUtc);

src/MxGateway.Server/Security/Authentication/ApiKeyRecordReader.cs

@@ -0,0 +1,26 @@
+using Microsoft.Data.Sqlite;
+
+namespace MxGateway.Server.Security.Authentication;
+
+public static class ApiKeyRecordReader
+{
+    public static ApiKeyRecord Read(SqliteDataReader reader)
+    {
+        return new ApiKeyRecord(
+            KeyId: reader.GetString(0),
+            KeyPrefix: reader.GetString(1),
+            SecretHash: (byte[])reader["secret_hash"],
+            DisplayName: reader.GetString(3),
+            Scopes: ApiKeyScopeSerializer.Deserialize(reader.GetString(4)),
+            CreatedUtc: DateTimeOffset.Parse(reader.GetString(5), System.Globalization.CultureInfo.InvariantCulture),
+            LastUsedUtc: ReadNullableDateTimeOffset(reader, 6),
+            RevokedUtc: ReadNullableDateTimeOffset(reader, 7));
+    }
+
+    private static DateTimeOffset? ReadNullableDateTimeOffset(SqliteDataReader reader, int ordinal)
+    {
+        return reader.IsDBNull(ordinal)
+            ? null
+            : DateTimeOffset.Parse(reader.GetString(ordinal), System.Globalization.CultureInfo.InvariantCulture);
+    }
+}

src/MxGateway.Server/Security/Authentication/ApiKeyScopeSerializer.cs

@@ -0,0 +1,23 @@
+using System.Text.Json;
+
+namespace MxGateway.Server.Security.Authentication;
+
+public static class ApiKeyScopeSerializer
+{
+    public static string Serialize(IReadOnlySet<string> scopes)
+    {
+        return JsonSerializer.Serialize(scopes.Order(StringComparer.Ordinal));
+    }
+
+    public static IReadOnlySet<string> Deserialize(string value)
+    {
+        if (string.IsNullOrWhiteSpace(value))
+        {
+            return new HashSet<string>(StringComparer.Ordinal);
+        }
+
+        string[]? scopes = JsonSerializer.Deserialize<string[]>(value);
+
+        return new HashSet<string>(scopes ?? [], StringComparer.Ordinal);
+    }
+}

src/MxGateway.Server/Security/Authentication/ApiKeySecretGenerator.cs

@@ -0,0 +1,17 @@
+using System.Security.Cryptography;
+
+namespace MxGateway.Server.Security.Authentication;
+
+public static class ApiKeySecretGenerator
+{
+    public static string Generate()
+    {
+        Span<byte> bytes = stackalloc byte[32];
+        RandomNumberGenerator.Fill(bytes);
+
+        return Convert.ToBase64String(bytes)
+            .TrimEnd('=')
+            .Replace('+', '-')
+            .Replace('/', '_');
+    }
+}

src/MxGateway.Server/Security/Authentication/ApiKeySecretHasher.cs

@@ -0,0 +1,35 @@
+using System.Security.Cryptography;
+using System.Text;
+using Microsoft.Extensions.Options;
+using MxGateway.Server.Configuration;
+
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed class ApiKeySecretHasher(
+    IConfiguration configuration,
+    IOptions<GatewayOptions> options) : IApiKeySecretHasher
+{
+    public byte[] HashSecret(string secret)
+    {
+        string pepper = GetPepper();
+        byte[] pepperBytes = Encoding.UTF8.GetBytes(pepper);
+        byte[] secretBytes = Encoding.UTF8.GetBytes(secret);
+
+        using HMACSHA256 hmac = new(pepperBytes);
+
+        return hmac.ComputeHash(secretBytes);
+    }
+
+    private string GetPepper()
+    {
+        string pepperSecretName = options.Value.Authentication.PepperSecretName;
+        string? pepper = configuration[pepperSecretName];
+
+        if (string.IsNullOrWhiteSpace(pepper))
+        {
+            throw new ApiKeyPepperUnavailableException(pepperSecretName);
+        }
+
+        return pepper;
+    }
+}

src/MxGateway.Server/Security/Authentication/ApiKeyVerificationFailure.cs

@@ -0,0 +1,11 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public enum ApiKeyVerificationFailure
+{
+    None,
+    MissingOrMalformedCredentials,
+    PepperUnavailable,
+    KeyNotFound,
+    KeyRevoked,
+    SecretMismatch
+}

src/MxGateway.Server/Security/Authentication/ApiKeyVerificationResult.cs

@@ -0,0 +1,23 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed record ApiKeyVerificationResult(
+    bool Succeeded,
+    ApiKeyIdentity? Identity,
+    ApiKeyVerificationFailure Failure)
+{
+    public static ApiKeyVerificationResult Success(ApiKeyIdentity identity)
+    {
+        return new ApiKeyVerificationResult(
+            Succeeded: true,
+            Identity: identity,
+            Failure: ApiKeyVerificationFailure.None);
+    }
+
+    public static ApiKeyVerificationResult Fail(ApiKeyVerificationFailure failure)
+    {
+        return new ApiKeyVerificationResult(
+            Succeeded: false,
+            Identity: null,
+            Failure: failure);
+    }
+}

src/MxGateway.Server/Security/Authentication/ApiKeyVerifier.cs

@@ -0,0 +1,57 @@
+using System.Security.Cryptography;
+
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed class ApiKeyVerifier(
+    IApiKeyParser parser,
+    IApiKeySecretHasher hasher,
+    IApiKeyStore keyStore) : IApiKeyVerifier
+{
+    public async Task<ApiKeyVerificationResult> VerifyAsync(
+        string? authorizationHeader,
+        CancellationToken cancellationToken)
+    {
+        if (!parser.TryParseAuthorizationHeader(authorizationHeader, out ParsedApiKey? parsedKey)
+            || parsedKey is null)
+        {
+            return ApiKeyVerificationResult.Fail(ApiKeyVerificationFailure.MissingOrMalformedCredentials);
+        }
+
+        ApiKeyRecord? storedKey = await keyStore.FindByKeyIdAsync(parsedKey.KeyId, cancellationToken)
+            .ConfigureAwait(false);
+
+        if (storedKey is null)
+        {
+            return ApiKeyVerificationResult.Fail(ApiKeyVerificationFailure.KeyNotFound);
+        }
+
+        if (storedKey.RevokedUtc is not null)
+        {
+            return ApiKeyVerificationResult.Fail(ApiKeyVerificationFailure.KeyRevoked);
+        }
+
+        byte[] presentedHash;
+        try
+        {
+            presentedHash = hasher.HashSecret(parsedKey.Secret);
+        }
+        catch (ApiKeyPepperUnavailableException)
+        {
+            return ApiKeyVerificationResult.Fail(ApiKeyVerificationFailure.PepperUnavailable);
+        }
+
+        if (!CryptographicOperations.FixedTimeEquals(presentedHash, storedKey.SecretHash))
+        {
+            return ApiKeyVerificationResult.Fail(ApiKeyVerificationFailure.SecretMismatch);
+        }
+
+        await keyStore.MarkKeyUsedAsync(storedKey.KeyId, DateTimeOffset.UtcNow, cancellationToken)
+            .ConfigureAwait(false);
+
+        return ApiKeyVerificationResult.Success(new ApiKeyIdentity(
+            KeyId: storedKey.KeyId,
+            KeyPrefix: storedKey.KeyPrefix,
+            DisplayName: storedKey.DisplayName,
+            Scopes: storedKey.Scopes));
+    }
+}

src/MxGateway.Server/Security/Authentication/AuthSqliteConnectionFactory.cs

@@ -0,0 +1,27 @@
+using Microsoft.Data.Sqlite;
+using Microsoft.Extensions.Options;
+using MxGateway.Server.Configuration;
+
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed class AuthSqliteConnectionFactory(IOptions<GatewayOptions> options)
+{
+    public SqliteConnection CreateConnection()
+    {
+        string sqlitePath = options.Value.Authentication.SqlitePath;
+        string? directory = Path.GetDirectoryName(sqlitePath);
+
+        if (!string.IsNullOrWhiteSpace(directory))
+        {
+            Directory.CreateDirectory(directory);
+        }
+
+        SqliteConnectionStringBuilder builder = new()
+        {
+            DataSource = sqlitePath,
+            Mode = SqliteOpenMode.ReadWriteCreate
+        };
+
+        return new SqliteConnection(builder.ToString());
+    }
+}

src/MxGateway.Server/Security/Authentication/AuthStoreMigrationException.cs

@@ -0,0 +1,3 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed class AuthStoreMigrationException(string message) : InvalidOperationException(message);

src/MxGateway.Server/Security/Authentication/AuthStoreMigrationHostedService.cs

@@ -0,0 +1,24 @@
+using Microsoft.Extensions.Options;
+using MxGateway.Server.Configuration;
+
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed class AuthStoreMigrationHostedService(
+    IOptions<GatewayOptions> options,
+    IAuthStoreMigrator migrator) : IHostedService
+{
+    public async Task StartAsync(CancellationToken cancellationToken)
+    {
+        AuthenticationOptions authentication = options.Value.Authentication;
+
+        if (authentication.Mode == AuthenticationMode.ApiKey && authentication.RunMigrationsOnStartup)
+        {
+            await migrator.MigrateAsync(cancellationToken).ConfigureAwait(false);
+        }
+    }
+
+    public Task StopAsync(CancellationToken cancellationToken)
+    {
+        return Task.CompletedTask;
+    }
+}

src/MxGateway.Server/Security/Authentication/AuthStoreServiceCollectionExtensions.cs

@@ -0,0 +1,20 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public static class AuthStoreServiceCollectionExtensions
+{
+    public static IServiceCollection AddSqliteAuthStore(this IServiceCollection services)
+    {
+        services.AddSingleton<IApiKeyParser, ApiKeyParser>();
+        services.AddSingleton<IApiKeySecretHasher, ApiKeySecretHasher>();
+        services.AddSingleton<IApiKeyVerifier, ApiKeyVerifier>();
+        services.AddSingleton<ApiKeyAdminCliRunner>();
+        services.AddSingleton<AuthSqliteConnectionFactory>();
+        services.AddSingleton<IAuthStoreMigrator, SqliteAuthStoreMigrator>();
+        services.AddSingleton<IApiKeyStore, SqliteApiKeyStore>();
+        services.AddSingleton<IApiKeyAdminStore, SqliteApiKeyAdminStore>();
+        services.AddSingleton<IApiKeyAuditStore, SqliteApiKeyAuditStore>();
+        services.AddHostedService<AuthStoreMigrationHostedService>();
+
+        return services;
+    }
+}

src/MxGateway.Server/Security/Authentication/IApiKeyAdminStore.cs

@@ -0,0 +1,16 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public interface IApiKeyAdminStore
+{
+    Task CreateAsync(ApiKeyCreateRequest request, CancellationToken cancellationToken);
+
+    Task<IReadOnlyList<ApiKeyRecord>> ListAsync(CancellationToken cancellationToken);
+
+    Task<bool> RevokeAsync(string keyId, DateTimeOffset revokedUtc, CancellationToken cancellationToken);
+
+    Task<bool> RotateAsync(
+        string keyId,
+        byte[] secretHash,
+        DateTimeOffset rotatedUtc,
+        CancellationToken cancellationToken);
+}

src/MxGateway.Server/Security/Authentication/IApiKeyAuditStore.cs

@@ -0,0 +1,8 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public interface IApiKeyAuditStore
+{
+    Task AppendAsync(ApiKeyAuditEntry entry, CancellationToken cancellationToken);
+
+    Task<IReadOnlyList<ApiKeyAuditRecord>> ListRecentAsync(int count, CancellationToken cancellationToken);
+}

src/MxGateway.Server/Security/Authentication/IApiKeyParser.cs

@@ -0,0 +1,6 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public interface IApiKeyParser
+{
+    bool TryParseAuthorizationHeader(string? authorizationHeader, out ParsedApiKey? apiKey);
+}

src/MxGateway.Server/Security/Authentication/IApiKeySecretHasher.cs

@@ -0,0 +1,6 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public interface IApiKeySecretHasher
+{
+    byte[] HashSecret(string secret);
+}

src/MxGateway.Server/Security/Authentication/IApiKeyStore.cs

@@ -0,0 +1,10 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public interface IApiKeyStore
+{
+    Task<ApiKeyRecord?> FindByKeyIdAsync(string keyId, CancellationToken cancellationToken);
+
+    Task<ApiKeyRecord?> FindActiveByKeyIdAsync(string keyId, CancellationToken cancellationToken);
+
+    Task MarkKeyUsedAsync(string keyId, DateTimeOffset usedUtc, CancellationToken cancellationToken);
+}

src/MxGateway.Server/Security/Authentication/IApiKeyVerifier.cs

@@ -0,0 +1,8 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public interface IApiKeyVerifier
+{
+    Task<ApiKeyVerificationResult> VerifyAsync(
+        string? authorizationHeader,
+        CancellationToken cancellationToken);
+}

src/MxGateway.Server/Security/Authentication/IAuthStoreMigrator.cs

@@ -0,0 +1,6 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public interface IAuthStoreMigrator
+{
+    Task MigrateAsync(CancellationToken cancellationToken);
+}

src/MxGateway.Server/Security/Authentication/ParsedApiKey.cs

@@ -0,0 +1,3 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed record ParsedApiKey(string KeyId, string Secret);

src/MxGateway.Server/Security/Authentication/SqliteApiKeyAdminStore.cs

@@ -0,0 +1,116 @@
+using Microsoft.Data.Sqlite;
+
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed class SqliteApiKeyAdminStore(AuthSqliteConnectionFactory connectionFactory) : IApiKeyAdminStore
+{
+    public async Task CreateAsync(ApiKeyCreateRequest request, CancellationToken cancellationToken)
+    {
+        await using SqliteConnection connection = connectionFactory.CreateConnection();
+        await connection.OpenAsync(cancellationToken).ConfigureAwait(false);
+
+        await using SqliteCommand command = connection.CreateCommand();
+        command.CommandText = """
+            INSERT INTO api_keys (
+                key_id,
+                key_prefix,
+                secret_hash,
+                display_name,
+                scopes,
+                created_utc,
+                last_used_utc,
+                revoked_utc)
+            VALUES (
+                $key_id,
+                $key_prefix,
+                $secret_hash,
+                $display_name,
+                $scopes,
+                $created_utc,
+                NULL,
+                NULL);
+            """;
+        AddCreateParameters(command, request);
+
+        await command.ExecuteNonQueryAsync(cancellationToken).ConfigureAwait(false);
+    }
+
+    public async Task<IReadOnlyList<ApiKeyRecord>> ListAsync(CancellationToken cancellationToken)
+    {
+        await using SqliteConnection connection = connectionFactory.CreateConnection();
+        await connection.OpenAsync(cancellationToken).ConfigureAwait(false);
+
+        await using SqliteCommand command = connection.CreateCommand();
+        command.CommandText = """
+            SELECT key_id, key_prefix, secret_hash, display_name, scopes, created_utc, last_used_utc, revoked_utc
+            FROM api_keys
+            ORDER BY key_id;
+            """;
+
+        List<ApiKeyRecord> records = [];
+
+        await using SqliteDataReader reader = await command.ExecuteReaderAsync(cancellationToken)
+            .ConfigureAwait(false);
+
+        while (await reader.ReadAsync(cancellationToken).ConfigureAwait(false))
+        {
+            records.Add(ApiKeyRecordReader.Read(reader));
+        }
+
+        return records;
+    }
+
+    public async Task<bool> RevokeAsync(string keyId, DateTimeOffset revokedUtc, CancellationToken cancellationToken)
+    {
+        await using SqliteConnection connection = connectionFactory.CreateConnection();
+        await connection.OpenAsync(cancellationToken).ConfigureAwait(false);
+
+        await using SqliteCommand command = connection.CreateCommand();
+        command.CommandText = """
+            UPDATE api_keys
+            SET revoked_utc = $revoked_utc
+            WHERE key_id = $key_id AND revoked_utc IS NULL;
+            """;
+        command.Parameters.AddWithValue("$key_id", keyId);
+        command.Parameters.AddWithValue("$revoked_utc", revokedUtc.ToString("O"));
+
+        int rows = await command.ExecuteNonQueryAsync(cancellationToken).ConfigureAwait(false);
+
+        return rows > 0;
+    }
+
+    public async Task<bool> RotateAsync(
+        string keyId,
+        byte[] secretHash,
+        DateTimeOffset rotatedUtc,
+        CancellationToken cancellationToken)
+    {
+        await using SqliteConnection connection = connectionFactory.CreateConnection();
+        await connection.OpenAsync(cancellationToken).ConfigureAwait(false);
+
+        await using SqliteCommand command = connection.CreateCommand();
+        command.CommandText = """
+            UPDATE api_keys
+            SET secret_hash = $secret_hash,
+                last_used_utc = NULL,
+                revoked_utc = NULL
+            WHERE key_id = $key_id;
+            """;
+        command.Parameters.AddWithValue("$key_id", keyId);
+        command.Parameters.Add("$secret_hash", SqliteType.Blob).Value = secretHash;
+
+        int rows = await command.ExecuteNonQueryAsync(cancellationToken).ConfigureAwait(false);
+
+        return rows > 0;
+    }
+
+    private static void AddCreateParameters(SqliteCommand command, ApiKeyCreateRequest request)
+    {
+        command.Parameters.AddWithValue("$key_id", request.KeyId);
+        command.Parameters.AddWithValue("$key_prefix", request.KeyPrefix);
+        command.Parameters.Add("$secret_hash", SqliteType.Blob).Value = request.SecretHash;
+        command.Parameters.AddWithValue("$display_name", request.DisplayName);
+        command.Parameters.AddWithValue("$scopes", ApiKeyScopeSerializer.Serialize(request.Scopes));
+        command.Parameters.AddWithValue("$created_utc", request.CreatedUtc.ToString("O"));
+    }
+}

src/MxGateway.Server/Security/Authentication/SqliteApiKeyAuditStore.cs

@@ -0,0 +1,65 @@
+using Microsoft.Data.Sqlite;
+
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed class SqliteApiKeyAuditStore(AuthSqliteConnectionFactory connectionFactory) : IApiKeyAuditStore
+{
+    public async Task AppendAsync(ApiKeyAuditEntry entry, CancellationToken cancellationToken)
+    {
+        await using SqliteConnection connection = connectionFactory.CreateConnection();
+        await connection.OpenAsync(cancellationToken).ConfigureAwait(false);
+
+        await using SqliteCommand command = connection.CreateCommand();
+        command.CommandText = """
+            INSERT INTO api_key_audit (key_id, event_type, remote_address, created_utc, details)
+            VALUES ($key_id, $event_type, $remote_address, $created_utc, $details);
+            """;
+        command.Parameters.AddWithValue("$key_id", (object?)entry.KeyId ?? DBNull.Value);
+        command.Parameters.AddWithValue("$event_type", entry.EventType);
+        command.Parameters.AddWithValue("$remote_address", (object?)entry.RemoteAddress ?? DBNull.Value);
+        command.Parameters.AddWithValue("$created_utc", DateTimeOffset.UtcNow.ToString("O"));
+        command.Parameters.AddWithValue("$details", (object?)entry.Details ?? DBNull.Value);
+
+        await command.ExecuteNonQueryAsync(cancellationToken).ConfigureAwait(false);
+    }
+
+    public async Task<IReadOnlyList<ApiKeyAuditRecord>> ListRecentAsync(int count, CancellationToken cancellationToken)
+    {
+        if (count <= 0)
+        {
+            return [];
+        }
+
+        await using SqliteConnection connection = connectionFactory.CreateConnection();
+        await connection.OpenAsync(cancellationToken).ConfigureAwait(false);
+
+        await using SqliteCommand command = connection.CreateCommand();
+        command.CommandText = """
+            SELECT audit_id, key_id, event_type, remote_address, created_utc, details
+            FROM api_key_audit
+            ORDER BY audit_id DESC
+            LIMIT $count;
+            """;
+        command.Parameters.AddWithValue("$count", count);
+
+        List<ApiKeyAuditRecord> records = [];
+
+        await using SqliteDataReader reader = await command.ExecuteReaderAsync(cancellationToken)
+            .ConfigureAwait(false);
+
+        while (await reader.ReadAsync(cancellationToken).ConfigureAwait(false))
+        {
+            records.Add(new ApiKeyAuditRecord(
+                AuditId: reader.GetInt64(0),
+                KeyId: reader.IsDBNull(1) ? null : reader.GetString(1),
+                EventType: reader.GetString(2),
+                RemoteAddress: reader.IsDBNull(3) ? null : reader.GetString(3),
+                CreatedUtc: DateTimeOffset.Parse(
+                    reader.GetString(4),
+                    System.Globalization.CultureInfo.InvariantCulture),
+                Details: reader.IsDBNull(5) ? null : reader.GetString(5)));
+        }
+
+        return records;
+    }
+}

src/MxGateway.Server/Security/Authentication/SqliteApiKeyStore.cs

@@ -0,0 +1,66 @@
+using Microsoft.Data.Sqlite;
+
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed class SqliteApiKeyStore(AuthSqliteConnectionFactory connectionFactory) : IApiKeyStore
+{
+    public Task<ApiKeyRecord?> FindByKeyIdAsync(string keyId, CancellationToken cancellationToken)
+    {
+        return FindByKeyIdAsync(keyId, requireActive: false, cancellationToken);
+    }
+
+    public Task<ApiKeyRecord?> FindActiveByKeyIdAsync(string keyId, CancellationToken cancellationToken)
+    {
+        return FindByKeyIdAsync(keyId, requireActive: true, cancellationToken);
+    }
+
+    public async Task MarkKeyUsedAsync(string keyId, DateTimeOffset usedUtc, CancellationToken cancellationToken)
+    {
+        await using SqliteConnection connection = connectionFactory.CreateConnection();
+        await connection.OpenAsync(cancellationToken).ConfigureAwait(false);
+
+        await using SqliteCommand command = connection.CreateCommand();
+        command.CommandText = """
+            UPDATE api_keys
+            SET last_used_utc = $last_used_utc
+            WHERE key_id = $key_id AND revoked_utc IS NULL;
+            """;
+        command.Parameters.AddWithValue("$key_id", keyId);
+        command.Parameters.AddWithValue("$last_used_utc", usedUtc.ToString("O"));
+
+        await command.ExecuteNonQueryAsync(cancellationToken).ConfigureAwait(false);
+    }
+
+    private async Task<ApiKeyRecord?> FindByKeyIdAsync(
+        string keyId,
+        bool requireActive,
+        CancellationToken cancellationToken)
+    {
+        await using SqliteConnection connection = connectionFactory.CreateConnection();
+        await connection.OpenAsync(cancellationToken).ConfigureAwait(false);
+
+        await using SqliteCommand command = connection.CreateCommand();
+        command.CommandText = requireActive
+            ? """
+              SELECT key_id, key_prefix, secret_hash, display_name, scopes, created_utc, last_used_utc, revoked_utc
+              FROM api_keys
+              WHERE key_id = $key_id AND revoked_utc IS NULL;
+              """
+            : """
+              SELECT key_id, key_prefix, secret_hash, display_name, scopes, created_utc, last_used_utc, revoked_utc
+              FROM api_keys
+              WHERE key_id = $key_id;
+              """;
+        command.Parameters.AddWithValue("$key_id", keyId);
+
+        await using SqliteDataReader reader = await command.ExecuteReaderAsync(cancellationToken)
+            .ConfigureAwait(false);
+
+        if (!await reader.ReadAsync(cancellationToken).ConfigureAwait(false))
+        {
+            return null;
+        }
+
+        return ApiKeyRecordReader.Read(reader);
+    }
+}

src/MxGateway.Server/Security/Authentication/SqliteAuthSchema.cs

@@ -0,0 +1,12 @@
+namespace MxGateway.Server.Security.Authentication;
+
+public static class SqliteAuthSchema
+{
+    public const int CurrentVersion = 1;
+
+    public const string SchemaVersionTable = "schema_version";
+
+    public const string ApiKeysTable = "api_keys";
+
+    public const string ApiKeyAuditTable = "api_key_audit";
+}

src/MxGateway.Server/Security/Authentication/SqliteAuthStoreMigrator.cs

@@ -0,0 +1,135 @@
+using Microsoft.Data.Sqlite;
+
+namespace MxGateway.Server.Security.Authentication;
+
+public sealed class SqliteAuthStoreMigrator(AuthSqliteConnectionFactory connectionFactory) : IAuthStoreMigrator
+{
+    public async Task MigrateAsync(CancellationToken cancellationToken)
+    {
+        await using SqliteConnection connection = connectionFactory.CreateConnection();
+        await connection.OpenAsync(cancellationToken).ConfigureAwait(false);
+
+        await using SqliteTransaction transaction =
+            (SqliteTransaction)await connection.BeginTransactionAsync(cancellationToken).ConfigureAwait(false);
+
+        int existingVersion = await ReadExistingSchemaVersionAsync(connection, transaction, cancellationToken)
+            .ConfigureAwait(false);
+
+        if (existingVersion > SqliteAuthSchema.CurrentVersion)
+        {
+            throw new AuthStoreMigrationException(
+                $"Auth database schema version {existingVersion} is newer than supported version {SqliteAuthSchema.CurrentVersion}.");
+        }
+
+        await ApplyVersionOneAsync(connection, transaction, cancellationToken).ConfigureAwait(false);
+
+        await transaction.CommitAsync(cancellationToken).ConfigureAwait(false);
+    }
+
+    private static async Task<int> ReadExistingSchemaVersionAsync(
+        SqliteConnection connection,
+        SqliteTransaction transaction,
+        CancellationToken cancellationToken)
+    {
+        await using SqliteCommand tableExistsCommand = connection.CreateCommand();
+        tableExistsCommand.Transaction = transaction;
+        tableExistsCommand.CommandText = """
+            SELECT COUNT(*)
+            FROM sqlite_master
+            WHERE type = 'table' AND name = $table_name;
+            """;
+        tableExistsCommand.Parameters.AddWithValue("$table_name", SqliteAuthSchema.SchemaVersionTable);
+
+        long tableCount = (long)(await tableExistsCommand.ExecuteScalarAsync(cancellationToken).ConfigureAwait(false) ?? 0L);
+
+        if (tableCount == 0)
+        {
+            return 0;
+        }
+
+        await using SqliteCommand versionCommand = connection.CreateCommand();
+        versionCommand.Transaction = transaction;
+        versionCommand.CommandText = """
+            SELECT version
+            FROM schema_version
+            WHERE id = 1;
+            """;
+
+        object? version = await versionCommand.ExecuteScalarAsync(cancellationToken).ConfigureAwait(false);
+
+        return version is null || version == DBNull.Value
+            ? 0
+            : Convert.ToInt32(version, System.Globalization.CultureInfo.InvariantCulture);
+    }
+
+    private static async Task ApplyVersionOneAsync(
+        SqliteConnection connection,
+        SqliteTransaction transaction,
+        CancellationToken cancellationToken)
+    {
+        await ExecuteNonQueryAsync(
+            connection,
+            transaction,
+            """
+            CREATE TABLE IF NOT EXISTS schema_version (
+                id INTEGER PRIMARY KEY CHECK (id = 1),
+                version INTEGER NOT NULL,
+                applied_utc TEXT NOT NULL
+            );
+
+            CREATE TABLE IF NOT EXISTS api_keys (
+                key_id TEXT PRIMARY KEY,
+                key_prefix TEXT NOT NULL,
+                secret_hash BLOB NOT NULL,
+                display_name TEXT NOT NULL,
+                scopes TEXT NOT NULL,
+                created_utc TEXT NOT NULL,
+                last_used_utc TEXT NULL,
+                revoked_utc TEXT NULL
+            );
+
+            CREATE TABLE IF NOT EXISTS api_key_audit (
+                audit_id INTEGER PRIMARY KEY AUTOINCREMENT,
+                key_id TEXT NULL,
+                event_type TEXT NOT NULL,
+                remote_address TEXT NULL,
+                created_utc TEXT NOT NULL,
+                details TEXT NULL
+            );
+
+            CREATE INDEX IF NOT EXISTS ix_api_keys_revoked_utc
+                ON api_keys (revoked_utc);
+
+            CREATE INDEX IF NOT EXISTS ix_api_key_audit_key_id_created_utc
+                ON api_key_audit (key_id, created_utc);
+            """,
+            cancellationToken).ConfigureAwait(false);
+
+        await using SqliteCommand versionCommand = connection.CreateCommand();
+        versionCommand.Transaction = transaction;
+        versionCommand.CommandText = """
+            INSERT INTO schema_version (id, version, applied_utc)
+            VALUES (1, $version, $applied_utc)
+            ON CONFLICT(id) DO UPDATE SET
+                version = excluded.version,
+                applied_utc = excluded.applied_utc;
+            """;
+        versionCommand.Parameters.AddWithValue("$version", SqliteAuthSchema.CurrentVersion);
+        versionCommand.Parameters.AddWithValue("$applied_utc", DateTimeOffset.UtcNow.ToString("O"));
+
+        await versionCommand.ExecuteNonQueryAsync(cancellationToken).ConfigureAwait(false);
+    }
+
+    private static async Task ExecuteNonQueryAsync(
+        SqliteConnection connection,
+        SqliteTransaction transaction,
+        string commandText,
+        CancellationToken cancellationToken)
+    {
+        await using SqliteCommand command = connection.CreateCommand();
+        command.Transaction = transaction;
+        command.CommandText = commandText;
+
+        await command.ExecuteNonQueryAsync(cancellationToken).ConfigureAwait(false);
+    }
+}

src/MxGateway.Server/Workers/IWorkerProcess.cs

@@ -0,0 +1,14 @@
+namespace MxGateway.Server.Workers;
+
+public interface IWorkerProcess : IDisposable
+{
+    int Id { get; }
+
+    bool HasExited { get; }
+
+    int? ExitCode { get; }
+
+    ValueTask WaitForExitAsync(CancellationToken cancellationToken);
+
+    void Kill(bool entireProcessTree);
+}

src/MxGateway.Server/Workers/IWorkerProcessFactory.cs

@@ -0,0 +1,8 @@
+using System.Diagnostics;
+
+namespace MxGateway.Server.Workers;
+
+public interface IWorkerProcessFactory
+{
+    IWorkerProcess Start(ProcessStartInfo startInfo);
+}

src/MxGateway.Server/Workers/IWorkerProcessLauncher.cs

@@ -0,0 +1,8 @@
+namespace MxGateway.Server.Workers;
+
+public interface IWorkerProcessLauncher
+{
+    Task<WorkerProcessHandle> LaunchAsync(
+        WorkerProcessLaunchRequest request,
+        CancellationToken cancellationToken = default);
+}

src/MxGateway.Server/Workers/IWorkerStartupProbe.cs

@@ -0,0 +1,9 @@
+namespace MxGateway.Server.Workers;
+
+public interface IWorkerStartupProbe
+{
+    Task WaitUntilReadyAsync(
+        IWorkerProcess process,
+        WorkerProcessLaunchRequest request,
+        CancellationToken cancellationToken);
+}

src/MxGateway.Server/Workers/SystemWorkerProcess.cs

@@ -0,0 +1,27 @@
+using System.Diagnostics;
+
+namespace MxGateway.Server.Workers;
+
+internal sealed class SystemWorkerProcess(Process process) : IWorkerProcess
+{
+    public int Id => process.Id;
+
+    public bool HasExited => process.HasExited;
+
+    public int? ExitCode => process.HasExited ? process.ExitCode : null;
+
+    public async ValueTask WaitForExitAsync(CancellationToken cancellationToken)
+    {
+        await process.WaitForExitAsync(cancellationToken).ConfigureAwait(false);
+    }
+
+    public void Kill(bool entireProcessTree)
+    {
+        process.Kill(entireProcessTree);
+    }
+
+    public void Dispose()
+    {
+        process.Dispose();
+    }
+}

src/MxGateway.Server/Workers/SystemWorkerProcessFactory.cs

@@ -0,0 +1,22 @@
+using System.Diagnostics;
+
+namespace MxGateway.Server.Workers;
+
+public sealed class SystemWorkerProcessFactory : IWorkerProcessFactory
+{
+    public IWorkerProcess Start(ProcessStartInfo startInfo)
+    {
+        Process process = new()
+        {
+            StartInfo = startInfo,
+        };
+
+        if (!process.Start())
+        {
+            process.Dispose();
+            throw new InvalidOperationException("Worker process failed to start.");
+        }
+
+        return new SystemWorkerProcess(process);
+    }
+}

src/MxGateway.Server/Workers/WorkerEnvelopeValidator.cs

@@ -0,0 +1,32 @@
+using MxGateway.Contracts.Proto;
+
+namespace MxGateway.Server.Workers;
+
+internal static class WorkerEnvelopeValidator
+{
+    public static void Validate(
+        WorkerEnvelope envelope,
+        WorkerFrameProtocolOptions options)
+    {
+        if (envelope.ProtocolVersion != options.ProtocolVersion)
+        {
+            throw new WorkerFrameProtocolException(
+                WorkerFrameProtocolErrorCode.ProtocolVersionMismatch,
+                $"Worker envelope protocol version {envelope.ProtocolVersion} does not match expected version {options.ProtocolVersion}.");
+        }
+
+        if (!string.Equals(envelope.SessionId, options.SessionId, StringComparison.Ordinal))
+        {
+            throw new WorkerFrameProtocolException(
+                WorkerFrameProtocolErrorCode.SessionMismatch,
+                "Worker envelope session id does not match the owning gateway session.");
+        }
+
+        if (envelope.BodyCase == WorkerEnvelope.BodyOneofCase.None)
+        {
+            throw new WorkerFrameProtocolException(
+                WorkerFrameProtocolErrorCode.InvalidEnvelope,
+                "Worker envelope must include a typed body.");
+        }
+    }
+}

src/MxGateway.Server/Workers/WorkerExecutableValidator.cs

@@ -0,0 +1,80 @@
+using System.Buffers.Binary;
+using MxGateway.Server.Configuration;
+
+namespace MxGateway.Server.Workers;
+
+internal static class WorkerExecutableValidator
+{
+    private const ushort ImageFileMachineI386 = 0x014c;
+    private const ushort ImageFileMachineAmd64 = 0x8664;
+    private const int DosHeaderSignatureOffset = 0;
+    private const int PeHeaderOffsetPointer = 0x3c;
+    private const int PeSignatureSize = 4;
+    private const int MachineOffsetFromPeHeader = PeSignatureSize;
+    private const int MinimumHeaderSize = 0x40;
+
+    public static void Validate(
+        string executablePath,
+        WorkerArchitecture requiredArchitecture)
+    {
+        ushort machine = ReadMachineType(executablePath);
+        ushort expectedMachine = requiredArchitecture switch
+        {
+            WorkerArchitecture.X86 => ImageFileMachineI386,
+            WorkerArchitecture.X64 => ImageFileMachineAmd64,
+            _ => throw new WorkerProcessLaunchException(
+                WorkerProcessLaunchErrorCode.InvalidExecutable,
+                "Worker executable required architecture is unsupported."),
+        };
+
+        if (machine != expectedMachine)
+        {
+            throw new WorkerProcessLaunchException(
+                WorkerProcessLaunchErrorCode.InvalidExecutable,
+                $"Worker executable architecture does not match required {requiredArchitecture} architecture.");
+        }
+    }
+
+    private static ushort ReadMachineType(string executablePath)
+    {
+        byte[] header = new byte[MinimumHeaderSize];
+        using FileStream stream = File.OpenRead(executablePath);
+        if (stream.Read(header) < header.Length)
+        {
+            throw InvalidExecutable("Worker executable is too small to contain a valid PE header.");
+        }
+
+        if (header[DosHeaderSignatureOffset] != 'M' || header[DosHeaderSignatureOffset + 1] != 'Z')
+        {
+            throw InvalidExecutable("Worker executable does not contain an MZ header.");
+        }
+
+        int peHeaderOffset = BinaryPrimitives.ReadInt32LittleEndian(header.AsSpan(PeHeaderOffsetPointer, sizeof(int)));
+        if (peHeaderOffset < MinimumHeaderSize)
+        {
+            throw InvalidExecutable("Worker executable PE header offset is invalid.");
+        }
+
+        byte[] peHeaderBytes = new byte[PeSignatureSize + sizeof(ushort)];
+        stream.Position = peHeaderOffset;
+        if (stream.Read(peHeaderBytes) < peHeaderBytes.Length)
+        {
+            throw InvalidExecutable("Worker executable PE header is missing.");
+        }
+
+        if (peHeaderBytes[0] != 'P' || peHeaderBytes[1] != 'E' || peHeaderBytes[2] != 0 || peHeaderBytes[3] != 0)
+        {
+            throw InvalidExecutable("Worker executable does not contain a PE header.");
+        }
+
+        return BinaryPrimitives.ReadUInt16LittleEndian(
+            peHeaderBytes.AsSpan(MachineOffsetFromPeHeader, sizeof(ushort)));
+    }
+
+    private static WorkerProcessLaunchException InvalidExecutable(string message)
+    {
+        return new WorkerProcessLaunchException(
+            WorkerProcessLaunchErrorCode.InvalidExecutable,
+            message);
+    }
+}

src/MxGateway.Server/Workers/WorkerFrameProtocolErrorCode.cs

@@ -0,0 +1,13 @@
+namespace MxGateway.Server.Workers;
+
+public enum WorkerFrameProtocolErrorCode
+{
+    Unknown = 0,
+    InvalidConfiguration = 1,
+    EndOfStream = 2,
+    MalformedLength = 3,
+    MessageTooLarge = 4,
+    InvalidEnvelope = 5,
+    ProtocolVersionMismatch = 6,
+    SessionMismatch = 7,
+}

src/MxGateway.Server/Workers/WorkerFrameProtocolException.cs

@@ -0,0 +1,23 @@
+namespace MxGateway.Server.Workers;
+
+public sealed class WorkerFrameProtocolException : Exception
+{
+    public WorkerFrameProtocolException(
+        WorkerFrameProtocolErrorCode errorCode,
+        string message)
+        : base(message)
+    {
+        ErrorCode = errorCode;
+    }
+
+    public WorkerFrameProtocolException(
+        WorkerFrameProtocolErrorCode errorCode,
+        string message,
+        Exception innerException)
+        : base(message, innerException)
+    {
+        ErrorCode = errorCode;
+    }
+
+    public WorkerFrameProtocolErrorCode ErrorCode { get; }
+}

src/MxGateway.Server/Workers/WorkerFrameProtocolOptions.cs

@@ -0,0 +1,53 @@
+using MxGateway.Contracts;
+
+namespace MxGateway.Server.Workers;
+
+public sealed class WorkerFrameProtocolOptions
+{
+    public const int DefaultMaxMessageBytes = 16 * 1024 * 1024;
+
+    public WorkerFrameProtocolOptions(string sessionId)
+        : this(
+            sessionId,
+            GatewayContractInfo.WorkerProtocolVersion,
+            DefaultMaxMessageBytes)
+    {
+    }
+
+    public WorkerFrameProtocolOptions(
+        string sessionId,
+        uint protocolVersion,
+        int maxMessageBytes)
+    {
+        if (string.IsNullOrWhiteSpace(sessionId))
+        {
+            throw new WorkerFrameProtocolException(
+                WorkerFrameProtocolErrorCode.InvalidConfiguration,
+                "Worker frame protocol requires a session id.");
+        }
+
+        if (protocolVersion == 0)
+        {
+            throw new WorkerFrameProtocolException(
+                WorkerFrameProtocolErrorCode.InvalidConfiguration,
+                "Worker frame protocol requires a non-zero protocol version.");
+        }
+
+        if (maxMessageBytes <= 0)
+        {
+            throw new WorkerFrameProtocolException(
+                WorkerFrameProtocolErrorCode.InvalidConfiguration,
+                "Worker frame protocol max message size must be greater than zero.");
+        }
+
+        SessionId = sessionId;
+        ProtocolVersion = protocolVersion;
+        MaxMessageBytes = maxMessageBytes;
+    }
+
+    public string SessionId { get; }
+
+    public uint ProtocolVersion { get; }
+
+    public int MaxMessageBytes { get; }
+}

src/MxGateway.Server/Workers/WorkerFrameReader.cs

@@ -0,0 +1,77 @@
+using System.Buffers.Binary;
+using Google.Protobuf;
+using MxGateway.Contracts.Proto;
+
+namespace MxGateway.Server.Workers;
+
+public sealed class WorkerFrameReader
+{
+    private readonly WorkerFrameProtocolOptions _options;
+    private readonly Stream _stream;
+
+    public WorkerFrameReader(
+        Stream stream,
+        WorkerFrameProtocolOptions options)
+    {
+        _stream = stream ?? throw new ArgumentNullException(nameof(stream));
+        _options = options ?? throw new ArgumentNullException(nameof(options));
+    }
+
+    public async ValueTask<WorkerEnvelope> ReadAsync(CancellationToken cancellationToken = default)
+    {
+        byte[] lengthPrefix = new byte[sizeof(uint)];
+        await ReadExactlyOrThrowAsync(lengthPrefix, cancellationToken).ConfigureAwait(false);
+
+        uint payloadLength = BinaryPrimitives.ReadUInt32LittleEndian(lengthPrefix);
+        if (payloadLength == 0)
+        {
+            throw new WorkerFrameProtocolException(
+                WorkerFrameProtocolErrorCode.MalformedLength,
+                "Worker frame payload length must be greater than zero.");
+        }
+
+        if (payloadLength > _options.MaxMessageBytes)
+        {
+            throw new WorkerFrameProtocolException(
+                WorkerFrameProtocolErrorCode.MessageTooLarge,
+                $"Worker frame payload length {payloadLength} exceeds the configured maximum of {_options.MaxMessageBytes} bytes.");
+        }
+
+        byte[] payload = new byte[payloadLength];
+        await ReadExactlyOrThrowAsync(payload, cancellationToken).ConfigureAwait(false);
+
+        WorkerEnvelope envelope;
+        try
+        {
+            envelope = WorkerEnvelope.Parser.ParseFrom(payload);
+        }
+        catch (InvalidProtocolBufferException exception)
+        {
+            throw new WorkerFrameProtocolException(
+                WorkerFrameProtocolErrorCode.InvalidEnvelope,
+                "Worker frame payload is not a valid WorkerEnvelope protobuf message.",
+                exception);
+        }
+
+        WorkerEnvelopeValidator.Validate(envelope, _options);
+
+        return envelope;
+    }
+
+    private async ValueTask ReadExactlyOrThrowAsync(
+        Memory<byte> buffer,
+        CancellationToken cancellationToken)
+    {
+        try
+        {
+            await _stream.ReadExactlyAsync(buffer, cancellationToken).ConfigureAwait(false);
+        }
+        catch (EndOfStreamException exception)
+        {
+            throw new WorkerFrameProtocolException(
+                WorkerFrameProtocolErrorCode.EndOfStream,
+                "Worker frame ended before the expected number of bytes were read.",
+                exception);
+        }
+    }
+}

src/MxGateway.Server/Workers/WorkerFrameWriter.cs

@@ -0,0 +1,48 @@
+using System.Buffers.Binary;
+using Google.Protobuf;
+using MxGateway.Contracts.Proto;
+
+namespace MxGateway.Server.Workers;
+
+public sealed class WorkerFrameWriter
+{
+    private readonly WorkerFrameProtocolOptions _options;
+    private readonly Stream _stream;
+
+    public WorkerFrameWriter(
+        Stream stream,
+        WorkerFrameProtocolOptions options)
+    {
+        _stream = stream ?? throw new ArgumentNullException(nameof(stream));
+        _options = options ?? throw new ArgumentNullException(nameof(options));
+    }
+
+    public async ValueTask WriteAsync(
+        WorkerEnvelope envelope,
+        CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(envelope);
+        WorkerEnvelopeValidator.Validate(envelope, _options);
+
+        int payloadLength = envelope.CalculateSize();
+        if (payloadLength == 0)
+        {
+            throw new WorkerFrameProtocolException(
+                WorkerFrameProtocolErrorCode.InvalidEnvelope,
+                "Worker envelope cannot serialize to an empty payload.");
+        }
+
+        if (payloadLength > _options.MaxMessageBytes)
+        {
+            throw new WorkerFrameProtocolException(
+                WorkerFrameProtocolErrorCode.MessageTooLarge,
+                $"Worker envelope payload length {payloadLength} exceeds the configured maximum of {_options.MaxMessageBytes} bytes.");
+        }
+
+        byte[] lengthPrefix = new byte[sizeof(uint)];
+        BinaryPrimitives.WriteUInt32LittleEndian(lengthPrefix, (uint)payloadLength);
+
+        await _stream.WriteAsync(lengthPrefix, cancellationToken).ConfigureAwait(false);
+        await _stream.WriteAsync(envelope.ToByteArray(), cancellationToken).ConfigureAwait(false);
+    }
+}

src/MxGateway.Server/Workers/WorkerProcessCommandLine.cs

@@ -0,0 +1,30 @@
+namespace MxGateway.Server.Workers;
+
+public sealed class WorkerProcessCommandLine
+{
+    public WorkerProcessCommandLine(
+        string executablePath,
+        IReadOnlyList<string> arguments)
+    {
+        ExecutablePath = executablePath;
+        Arguments = arguments;
+    }
+
+    public string ExecutablePath { get; }
+
+    public IReadOnlyList<string> Arguments { get; }
+
+    public override string ToString()
+    {
+        return string.Join(
+            " ",
+            new[] { Quote(ExecutablePath) }.Concat(Arguments.Select(Quote)));
+    }
+
+    private static string Quote(string value)
+    {
+        return value.Contains(' ', StringComparison.Ordinal)
+            ? $"\"{value}\""
+            : value;
+    }
+}

src/MxGateway.Server/Workers/WorkerProcessHandle.cs

@@ -0,0 +1,28 @@
+namespace MxGateway.Server.Workers;
+
+public sealed class WorkerProcessHandle : IDisposable
+{
+    public WorkerProcessHandle(
+        IWorkerProcess process,
+        WorkerProcessCommandLine commandLine,
+        DateTimeOffset launchedAt)
+    {
+        Process = process;
+        ProcessId = process.Id;
+        CommandLine = commandLine;
+        LaunchedAt = launchedAt;
+    }
+
+    public IWorkerProcess Process { get; }
+
+    public int ProcessId { get; }
+
+    public WorkerProcessCommandLine CommandLine { get; }
+
+    public DateTimeOffset LaunchedAt { get; }
+
+    public void Dispose()
+    {
+        Process.Dispose();
+    }
+}

src/MxGateway.Server/Workers/WorkerProcessLaunchErrorCode.cs

@@ -0,0 +1,13 @@
+namespace MxGateway.Server.Workers;
+
+public enum WorkerProcessLaunchErrorCode
+{
+    Unknown = 0,
+    InvalidRequest = 1,
+    ExecutableNotFound = 2,
+    InvalidExecutable = 3,
+    InvalidWorkingDirectory = 4,
+    StartFailed = 5,
+    StartupTimeout = 6,
+    StartupFailed = 7,
+}

src/MxGateway.Server/Workers/WorkerProcessLaunchException.cs

@@ -0,0 +1,23 @@
+namespace MxGateway.Server.Workers;
+
+public sealed class WorkerProcessLaunchException : Exception
+{
+    public WorkerProcessLaunchException(
+        WorkerProcessLaunchErrorCode errorCode,
+        string message)
+        : base(message)
+    {
+        ErrorCode = errorCode;
+    }
+
+    public WorkerProcessLaunchException(
+        WorkerProcessLaunchErrorCode errorCode,
+        string message,
+        Exception innerException)
+        : base(message, innerException)
+    {
+        ErrorCode = errorCode;
+    }
+
+    public WorkerProcessLaunchErrorCode ErrorCode { get; }
+}

src/MxGateway.Server/Workers/WorkerProcessLaunchRequest.cs

@@ -0,0 +1,8 @@
+namespace MxGateway.Server.Workers;
+
+public sealed record WorkerProcessLaunchRequest(
+    string SessionId,
+    string PipeName,
+    uint ProtocolVersion,
+    string Nonce,
+    IDisposable? PipeReservation = null);

src/MxGateway.Server/Workers/WorkerProcessLauncher.cs

@@ -0,0 +1,262 @@
+using System.Diagnostics;
+using Microsoft.Extensions.Options;
+using MxGateway.Server.Configuration;
+using MxGateway.Server.Metrics;
+
+namespace MxGateway.Server.Workers;
+
+public sealed class WorkerProcessLauncher : IWorkerProcessLauncher
+{
+    public const string WorkerNonceEnvironmentVariableName = "MXGATEWAY_WORKER_NONCE";
+
+    private readonly IWorkerProcessFactory _processFactory;
+    private readonly IWorkerStartupProbe _startupProbe;
+    private readonly GatewayMetrics _metrics;
+    private readonly TimeProvider _timeProvider;
+    private readonly WorkerOptions _workerOptions;
+
+    public WorkerProcessLauncher(
+        IOptions<GatewayOptions> gatewayOptions,
+        IWorkerProcessFactory processFactory,
+        IWorkerStartupProbe startupProbe,
+        GatewayMetrics metrics,
+        TimeProvider? timeProvider = null)
+    {
+        ArgumentNullException.ThrowIfNull(gatewayOptions);
+        ArgumentNullException.ThrowIfNull(processFactory);
+        ArgumentNullException.ThrowIfNull(startupProbe);
+        ArgumentNullException.ThrowIfNull(metrics);
+
+        _workerOptions = gatewayOptions.Value.Worker;
+        _processFactory = processFactory;
+        _startupProbe = startupProbe;
+        _metrics = metrics;
+        _timeProvider = timeProvider ?? TimeProvider.System;
+    }
+
+    public async Task<WorkerProcessHandle> LaunchAsync(
+        WorkerProcessLaunchRequest request,
+        CancellationToken cancellationToken = default)
+    {
+        try
+        {
+            return await LaunchCoreAsync(request, cancellationToken).ConfigureAwait(false);
+        }
+        catch
+        {
+            request.PipeReservation?.Dispose();
+            throw;
+        }
+    }
+
+    private async Task<WorkerProcessHandle> LaunchCoreAsync(
+        WorkerProcessLaunchRequest request,
+        CancellationToken cancellationToken)
+    {
+        ValidateRequest(request);
+
+        DateTimeOffset startedAt = _timeProvider.GetUtcNow();
+        ProcessStartInfo startInfo = CreateStartInfo(request, out WorkerProcessCommandLine commandLine);
+
+        IWorkerProcess process;
+        try
+        {
+            process = _processFactory.Start(startInfo);
+        }
+        catch (Exception exception) when (exception is not WorkerProcessLaunchException)
+        {
+            throw new WorkerProcessLaunchException(
+                WorkerProcessLaunchErrorCode.StartFailed,
+                "Worker process failed to start.",
+                exception);
+        }
+
+        try
+        {
+            using CancellationTokenSource startupTimeout = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
+            startupTimeout.CancelAfter(TimeSpan.FromSeconds(_workerOptions.StartupTimeoutSeconds));
+
+            await _startupProbe
+                .WaitUntilReadyAsync(process, request, startupTimeout.Token)
+                .ConfigureAwait(false);
+
+            _metrics.WorkerStarted(_timeProvider.GetUtcNow() - startedAt);
+
+            return new WorkerProcessHandle(process, commandLine, startedAt);
+        }
+        catch (OperationCanceledException exception) when (!cancellationToken.IsCancellationRequested)
+        {
+            KillAndDispose(process, "StartupTimeout");
+            throw new WorkerProcessLaunchException(
+                WorkerProcessLaunchErrorCode.StartupTimeout,
+                "Worker process did not complete startup before the configured timeout.",
+                exception);
+        }
+        catch (OperationCanceledException)
+        {
+            KillAndDispose(process, "LaunchCanceled");
+            throw;
+        }
+        catch (Exception exception) when (exception is not WorkerProcessLaunchException)
+        {
+            KillAndDispose(process, "StartupFailed");
+            throw new WorkerProcessLaunchException(
+                WorkerProcessLaunchErrorCode.StartupFailed,
+                "Worker process failed during startup.",
+                exception);
+        }
+        catch (WorkerProcessLaunchException)
+        {
+            KillAndDispose(process, "StartupFailed");
+            throw;
+        }
+    }
+
+    private ProcessStartInfo CreateStartInfo(
+        WorkerProcessLaunchRequest request,
+        out WorkerProcessCommandLine commandLine)
+    {
+        string executablePath = ResolveExecutablePath();
+        string workingDirectory = ResolveWorkingDirectory(executablePath);
+        string[] arguments =
+        [
+            "--session-id",
+            request.SessionId,
+            "--pipe-name",
+            request.PipeName,
+            "--protocol-version",
+            request.ProtocolVersion.ToString(System.Globalization.CultureInfo.InvariantCulture),
+        ];
+
+        ProcessStartInfo startInfo = new()
+        {
+            FileName = executablePath,
+            WorkingDirectory = workingDirectory,
+            UseShellExecute = false,
+            CreateNoWindow = true,
+            ErrorDialog = false,
+        };
+
+        foreach (string argument in arguments)
+        {
+            startInfo.ArgumentList.Add(argument);
+        }
+
+        startInfo.Environment[WorkerNonceEnvironmentVariableName] = request.Nonce;
+
+        commandLine = new WorkerProcessCommandLine(executablePath, arguments);
+
+        return startInfo;
+    }
+
+    private string ResolveExecutablePath()
+    {
+        string executablePath;
+        try
+        {
+            executablePath = Path.GetFullPath(_workerOptions.ExecutablePath);
+        }
+        catch (Exception exception) when (exception is ArgumentException or NotSupportedException or PathTooLongException)
+        {
+            throw new WorkerProcessLaunchException(
+                WorkerProcessLaunchErrorCode.InvalidExecutable,
+                "Worker executable path is not a valid filesystem path.",
+                exception);
+        }
+
+        if (!string.Equals(Path.GetExtension(executablePath), ".exe", StringComparison.OrdinalIgnoreCase))
+        {
+            throw new WorkerProcessLaunchException(
+                WorkerProcessLaunchErrorCode.InvalidExecutable,
+                "Worker executable path must point to a .exe file.");
+        }
+
+        if (!File.Exists(executablePath))
+        {
+            throw new WorkerProcessLaunchException(
+                WorkerProcessLaunchErrorCode.ExecutableNotFound,
+                "Worker executable does not exist.");
+        }
+
+        WorkerExecutableValidator.Validate(executablePath, _workerOptions.RequiredArchitecture);
+
+        return executablePath;
+    }
+
+    private string ResolveWorkingDirectory(string executablePath)
+    {
+        if (string.IsNullOrWhiteSpace(_workerOptions.WorkingDirectory))
+        {
+            return Path.GetDirectoryName(executablePath) ?? Environment.CurrentDirectory;
+        }
+
+        string workingDirectory;
+        try
+        {
+            workingDirectory = Path.GetFullPath(_workerOptions.WorkingDirectory);
+        }
+        catch (Exception exception) when (exception is ArgumentException or NotSupportedException or PathTooLongException)
+        {
+            throw new WorkerProcessLaunchException(
+                WorkerProcessLaunchErrorCode.InvalidWorkingDirectory,
+                "Worker working directory is not a valid filesystem path.",
+                exception);
+        }
+
+        if (!Directory.Exists(workingDirectory))
+        {
+            throw new WorkerProcessLaunchException(
+                WorkerProcessLaunchErrorCode.InvalidWorkingDirectory,
+                "Worker working directory does not exist.");
+        }
+
+        return workingDirectory;
+    }
+
+    private void KillAndDispose(IWorkerProcess process, string reason)
+    {
+        try
+        {
+            if (!process.HasExited)
+            {
+                process.Kill(entireProcessTree: true);
+                _metrics.WorkerKilled(reason);
+            }
+        }
+        finally
+        {
+            process.Dispose();
+        }
+    }
+
+    private static void ValidateRequest(WorkerProcessLaunchRequest request)
+    {
+        if (string.IsNullOrWhiteSpace(request.SessionId))
+        {
+            throw new WorkerProcessLaunchException(
+                WorkerProcessLaunchErrorCode.InvalidRequest,
+                "Worker launch requires a session id.");
+        }
+
+        if (string.IsNullOrWhiteSpace(request.PipeName))
+        {
+            throw new WorkerProcessLaunchException(
+                WorkerProcessLaunchErrorCode.InvalidRequest,
+                "Worker launch requires a pipe name.");
+        }
+
+        if (request.ProtocolVersion == 0)
+        {
+            throw new WorkerProcessLaunchException(
+                WorkerProcessLaunchErrorCode.InvalidRequest,
+                "Worker launch requires a non-zero protocol version.");
+        }
+
+        if (string.IsNullOrWhiteSpace(request.Nonce))
+        {
+            throw new WorkerProcessLaunchException(
+                WorkerProcessLaunchErrorCode.InvalidRequest,
+                "Worker launch requires a nonce.");
+        }
+    }
+}

src/MxGateway.Server/Workers/WorkerProcessStartedProbe.cs

@@ -0,0 +1,19 @@
+namespace MxGateway.Server.Workers;
+
+public sealed class WorkerProcessStartedProbe : IWorkerStartupProbe
+{
+    public Task WaitUntilReadyAsync(
+        IWorkerProcess process,
+        WorkerProcessLaunchRequest request,
+        CancellationToken cancellationToken)
+    {
+        if (process.HasExited)
+        {
+            throw new WorkerProcessLaunchException(
+                WorkerProcessLaunchErrorCode.StartupFailed,
+                $"Worker process exited before startup completed with exit code {process.ExitCode}.");
+        }
+
+        return Task.CompletedTask;
+    }
+}

src/MxGateway.Server/Workers/WorkerServiceCollectionExtensions.cs

@@ -0,0 +1,13 @@
+namespace MxGateway.Server.Workers;
+
+public static class WorkerServiceCollectionExtensions
+{
+    public static IServiceCollection AddWorkerProcessLauncher(this IServiceCollection services)
+    {
+        services.AddSingleton<IWorkerProcessFactory, SystemWorkerProcessFactory>();
+        services.AddSingleton<IWorkerStartupProbe, WorkerProcessStartedProbe>();
+        services.AddSingleton<IWorkerProcessLauncher, WorkerProcessLauncher>();
+
+        return services;
+    }
+}

src/MxGateway.Tests/Diagnostics/GatewayLogRedactorTests.cs

@@ -0,0 +1,82 @@
+using MxGateway.Server.Diagnostics;
+
+namespace MxGateway.Tests.Diagnostics;
+
+public sealed class GatewayLogRedactorTests
+{
+    [Fact]
+    public void RedactApiKey_PreservesKeyIdAndRemovesSecret()
+    {
+        string? redacted = GatewayLogRedactor.RedactApiKey("Bearer mxgw_operator01_super-secret");
+
+        Assert.Equal("Bearer mxgw_operator01_[redacted]", redacted);
+        Assert.DoesNotContain("super-secret", redacted);
+    }
+
+    [Fact]
+    public void RedactApiKey_RemovesSecretContainingUnderscores()
+    {
+        string? redacted = GatewayLogRedactor.RedactApiKey("Bearer mxgw_operator01_super_secret_value");
+
+        Assert.Equal("Bearer mxgw_operator01_[redacted]", redacted);
+        Assert.DoesNotContain("super_secret_value", redacted);
+    }
+
+    [Theory]
+    [InlineData("AuthenticateUser")]
+    [InlineData("WriteSecured")]
+    [InlineData("WriteSecured2")]
+    public void IsCredentialBearingCommand_IdentifiesSensitiveMxAccessCommands(string commandMethod)
+    {
+        Assert.True(GatewayLogRedactor.IsCredentialBearingCommand(commandMethod));
+    }
+
+    [Fact]
+    public void RedactCommandValue_DoesNotLogRawValuesByDefault()
+    {
+        object? redacted = GatewayLogRedactor.RedactCommandValue("Write", "plaintext-tag-value");
+
+        Assert.Equal("[redacted]", redacted);
+    }
+
+    [Fact]
+    public void RedactCommandValue_RedactsSecuredWriteEvenWhenValueLoggingIsEnabled()
+    {
+        object? redacted = GatewayLogRedactor.RedactCommandValue(
+            "WriteSecured",
+            "credential-bearing-value",
+            valueLoggingEnabled: true);
+
+        Assert.Equal("[redacted]", redacted);
+    }
+
+    [Fact]
+    public void RedactCommandValue_AllowsNonSensitiveValueOnlyWhenValueLoggingIsEnabled()
+    {
+        object? redacted = GatewayLogRedactor.RedactCommandValue(
+            "Write",
+            "diagnostic-value",
+            valueLoggingEnabled: true);
+
+        Assert.Equal("diagnostic-value", redacted);
+    }
+
+    [Fact]
+    public void LogScope_RedactsClientIdentityBeforeScopeStateIsCreated()
+    {
+        GatewayLogScope scope = new(
+            SessionId: "session-1",
+            WorkerProcessId: 1234,
+            CorrelationId: 99,
+            CommandMethod: "AuthenticateUser",
+            ClientIdentity: "Bearer mxgw_admin_secret");
+
+        IReadOnlyDictionary<string, object?> values = scope.ToDictionary();
+
+        Assert.Equal("session-1", values["SessionId"]);
+        Assert.Equal(1234, values["WorkerProcessId"]);
+        Assert.Equal((ulong)99, values["CorrelationId"]);
+        Assert.Equal("AuthenticateUser", values["CommandMethod"]);
+        Assert.Equal("Bearer mxgw_admin_[redacted]", values["ClientIdentity"]);
+    }
+}

src/MxGateway.Tests/Gateway/GatewayApplicationTests.cs

@@ -1,7 +1,9 @@
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Routing;
+using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Options;
 using MxGateway.Server;
+using MxGateway.Server.Metrics;
 
 namespace MxGateway.Tests.Gateway;
 
@@ -21,6 +23,16 @@ public sealed class GatewayApplicationTests
         Assert.Equal("LiveHealth", endpoint.Metadata.GetMetadata<IEndpointNameMetadata>()?.EndpointName);
     }
 
+    [Fact]
+    public void Build_RegistersGatewayMetrics()
+    {
+        WebApplication app = GatewayApplication.Build([]);
+
+        GatewayMetrics metrics = app.Services.GetRequiredService<GatewayMetrics>();
+
+        Assert.NotNull(metrics);
+    }
+
     [Theory]
     [InlineData(
         "MxGateway:Worker:ExecutablePath",

src/MxGateway.Tests/Gateway/Workers/WorkerFrameProtocolTests.cs

@@ -0,0 +1,209 @@
+using System.Buffers.Binary;
+using Google.Protobuf;
+using MxGateway.Contracts;
+using MxGateway.Contracts.Proto;
+using MxGateway.Server.Workers;
+
+namespace MxGateway.Tests.Gateway.Workers;
+
+public sealed class WorkerFrameProtocolTests
+{
+    private const string SessionId = "session-1";
+
+    [Fact]
+    public async Task WriteAndReadAsync_WithValidEnvelope_RoundTripsFrame()
+    {
+        WorkerFrameProtocolOptions options = new(SessionId);
+        await using MemoryStream stream = new();
+        WorkerEnvelope original = CreateEnvelope();
+
+        WorkerFrameWriter writer = new(stream, options);
+        await writer.WriteAsync(original);
+        stream.Position = 0;
+
+        WorkerFrameReader reader = new(stream, options);
+        WorkerEnvelope parsed = await reader.ReadAsync();
+
+        Assert.Equal(original, parsed);
+    }
+
+    [Fact]
+    public async Task ReadAsync_WithPartialReads_ReassemblesFrame()
+    {
+        WorkerFrameProtocolOptions options = new(SessionId);
+        WorkerEnvelope original = CreateEnvelope();
+        byte[] frame = CreateFrame(original);
+        await using ChunkedReadStream stream = new(frame, chunkSize: 2);
+
+        WorkerFrameReader reader = new(stream, options);
+        WorkerEnvelope parsed = await reader.ReadAsync();
+
+        Assert.Equal(original, parsed);
+        Assert.True(stream.ReadCallCount > 2);
+    }
+
+    [Fact]
+    public async Task ReadAsync_WithZeroLengthFrame_ThrowsMalformedLength()
+    {
+        WorkerFrameProtocolOptions options = new(SessionId);
+        await using MemoryStream stream = new(new byte[sizeof(uint)]);
+
+        WorkerFrameReader reader = new(stream, options);
+        WorkerFrameProtocolException exception =
+            await Assert.ThrowsAsync<WorkerFrameProtocolException>(
+                async () => await reader.ReadAsync());
+
+        Assert.Equal(WorkerFrameProtocolErrorCode.MalformedLength, exception.ErrorCode);
+    }
+
+    [Fact]
+    public async Task ReadAsync_WithOversizedLength_ThrowsBeforePayloadAllocation()
+    {
+        WorkerFrameProtocolOptions options = new(SessionId, GatewayContractInfo.WorkerProtocolVersion, maxMessageBytes: 16);
+        byte[] lengthPrefix = new byte[sizeof(uint)];
+        BinaryPrimitives.WriteUInt32LittleEndian(lengthPrefix, 17);
+        await using MemoryStream stream = new(lengthPrefix);
+
+        WorkerFrameReader reader = new(stream, options);
+        WorkerFrameProtocolException exception =
+            await Assert.ThrowsAsync<WorkerFrameProtocolException>(
+                async () => await reader.ReadAsync());
+
+        Assert.Equal(WorkerFrameProtocolErrorCode.MessageTooLarge, exception.ErrorCode);
+    }
+
+    [Fact]
+    public async Task ReadAsync_WithWrongProtocolVersion_ThrowsProtocolVersionMismatch()
+    {
+        WorkerFrameProtocolOptions options = new(SessionId);
+        WorkerEnvelope envelope = CreateEnvelope();
+        envelope.ProtocolVersion++;
+        await using MemoryStream stream = new(CreateFrame(envelope));
+
+        WorkerFrameReader reader = new(stream, options);
+        WorkerFrameProtocolException exception =
+            await Assert.ThrowsAsync<WorkerFrameProtocolException>(
+                async () => await reader.ReadAsync());
+
+        Assert.Equal(WorkerFrameProtocolErrorCode.ProtocolVersionMismatch, exception.ErrorCode);
+    }
+
+    [Fact]
+    public async Task ReadAsync_WithWrongSessionId_ThrowsSessionMismatch()
+    {
+        WorkerFrameProtocolOptions options = new(SessionId);
+        WorkerEnvelope envelope = CreateEnvelope();
+        envelope.SessionId = "different-session";
+        await using MemoryStream stream = new(CreateFrame(envelope));
+
+        WorkerFrameReader reader = new(stream, options);
+        WorkerFrameProtocolException exception =
+            await Assert.ThrowsAsync<WorkerFrameProtocolException>(
+                async () => await reader.ReadAsync());
+
+        Assert.Equal(WorkerFrameProtocolErrorCode.SessionMismatch, exception.ErrorCode);
+    }
+
+    [Fact]
+    public async Task ReadAsync_WithMalformedPayload_ThrowsInvalidEnvelope()
+    {
+        WorkerFrameProtocolOptions options = new(SessionId);
+        byte[] frame = CreateFrame([0x80]);
+        await using MemoryStream stream = new(frame);
+
+        WorkerFrameReader reader = new(stream, options);
+        WorkerFrameProtocolException exception =
+            await Assert.ThrowsAsync<WorkerFrameProtocolException>(
+                async () => await reader.ReadAsync());
+
+        Assert.Equal(WorkerFrameProtocolErrorCode.InvalidEnvelope, exception.ErrorCode);
+    }
+
+    [Fact]
+    public async Task ReadAsync_WithMissingEnvelopeBody_ThrowsInvalidEnvelope()
+    {
+        WorkerFrameProtocolOptions options = new(SessionId);
+        WorkerEnvelope envelope = CreateEnvelope();
+        envelope.ClearBody();
+        await using MemoryStream stream = new(CreateFrame(envelope));
+
+        WorkerFrameReader reader = new(stream, options);
+        WorkerFrameProtocolException exception =
+            await Assert.ThrowsAsync<WorkerFrameProtocolException>(
+                async () => await reader.ReadAsync());
+
+        Assert.Equal(WorkerFrameProtocolErrorCode.InvalidEnvelope, exception.ErrorCode);
+    }
+
+    [Fact]
+    public async Task WriteAsync_WithOversizedEnvelope_ThrowsMessageTooLarge()
+    {
+        WorkerFrameProtocolOptions options = new(SessionId, GatewayContractInfo.WorkerProtocolVersion, maxMessageBytes: 8);
+        await using MemoryStream stream = new();
+
+        WorkerFrameWriter writer = new(stream, options);
+        WorkerFrameProtocolException exception =
+            await Assert.ThrowsAsync<WorkerFrameProtocolException>(
+                async () => await writer.WriteAsync(CreateEnvelope()));
+
+        Assert.Equal(WorkerFrameProtocolErrorCode.MessageTooLarge, exception.ErrorCode);
+        Assert.Equal(0, stream.Length);
+    }
+
+    private static WorkerEnvelope CreateEnvelope()
+    {
+        return new WorkerEnvelope
+        {
+            ProtocolVersion = GatewayContractInfo.WorkerProtocolVersion,
+            SessionId = SessionId,
+            Sequence = 1,
+            CorrelationId = "correlation-1",
+            WorkerHello = new WorkerHello
+            {
+                ProtocolVersion = GatewayContractInfo.WorkerProtocolVersion,
+                Nonce = "nonce",
+                WorkerProcessId = 1234,
+                WorkerVersion = "test-worker",
+            },
+        };
+    }
+
+    private static byte[] CreateFrame(IMessage message)
+    {
+        return CreateFrame(message.ToByteArray());
+    }
+
+    private static byte[] CreateFrame(byte[] payload)
+    {
+        byte[] frame = new byte[sizeof(uint) + payload.Length];
+        BinaryPrimitives.WriteUInt32LittleEndian(frame.AsSpan(0, sizeof(uint)), (uint)payload.Length);
+        payload.CopyTo(frame.AsSpan(sizeof(uint)));
+
+        return frame;
+    }
+
+    private sealed class ChunkedReadStream : MemoryStream
+    {
+        private readonly int _chunkSize;
+
+        public ChunkedReadStream(
+            byte[] buffer,
+            int chunkSize)
+            : base(buffer)
+        {
+            _chunkSize = chunkSize;
+        }
+
+        public int ReadCallCount { get; private set; }
+
+        public override ValueTask<int> ReadAsync(
+            Memory<byte> buffer,
+            CancellationToken cancellationToken = default)
+        {
+            ReadCallCount++;
+            int requestedCount = Math.Min(buffer.Length, _chunkSize);
+
+            return base.ReadAsync(buffer[..requestedCount], cancellationToken);
+        }
+    }
+}

src/MxGateway.Tests/Gateway/Workers/WorkerProcessLauncherTests.cs

@@ -0,0 +1,307 @@
+using System.Diagnostics;
+using Microsoft.Extensions.Options;
+using MxGateway.Contracts;
+using MxGateway.Server.Configuration;
+using MxGateway.Server.Metrics;
+using MxGateway.Server.Workers;
+
+namespace MxGateway.Tests.Gateway.Workers;
+
+public sealed class WorkerProcessLauncherTests
+{
+    private const string SessionId = "session-1";
+    private const string PipeName = "mxaccess-gateway-123-session-1";
+    private const string Nonce = "super-secret-nonce";
+
+    [Fact]
+    public async Task LaunchAsync_WithValidWorker_StartsProcessWithBootstrapArgumentsAndNonceEnvironment()
+    {
+        using TestDirectory directory = TestDirectory.Create();
+        string executablePath = directory.CreateWorkerExecutable(machine: 0x014c);
+        FakeWorkerProcess process = new(processId: 1234);
+        FakePipeReservation pipeReservation = new();
+        FakeWorkerProcessFactory processFactory = new(process);
+        GatewayMetrics metrics = new();
+        WorkerProcessLauncher launcher = CreateLauncher(executablePath, processFactory, new SucceedingStartupProbe(), metrics);
+
+        using WorkerProcessHandle handle = await launcher.LaunchAsync(CreateRequest(pipeReservation));
+
+        Assert.Equal(1234, handle.ProcessId);
+        Assert.Same(process, handle.Process);
+        Assert.NotNull(processFactory.LastStartInfo);
+        Assert.Equal(Path.GetFullPath(executablePath), processFactory.LastStartInfo.FileName);
+        Assert.False(processFactory.LastStartInfo.UseShellExecute);
+        Assert.True(processFactory.LastStartInfo.CreateNoWindow);
+        Assert.Equal(
+            ["--session-id", SessionId, "--pipe-name", PipeName, "--protocol-version", "1"],
+            processFactory.LastStartInfo.ArgumentList);
+        Assert.Equal(Nonce, processFactory.LastStartInfo.Environment[WorkerProcessLauncher.WorkerNonceEnvironmentVariableName]);
+        Assert.DoesNotContain(Nonce, handle.CommandLine.ToString(), StringComparison.Ordinal);
+        Assert.DoesNotContain(Nonce, string.Join(" ", handle.CommandLine.Arguments), StringComparison.Ordinal);
+        Assert.False(pipeReservation.DisposeCalled);
+        Assert.Equal(1, metrics.GetSnapshot().WorkersRunning);
+    }
+
+    [Fact]
+    public async Task LaunchAsync_WhenStartupProbeFails_KillsAndDisposesWorker()
+    {
+        using TestDirectory directory = TestDirectory.Create();
+        string executablePath = directory.CreateWorkerExecutable(machine: 0x014c);
+        FakeWorkerProcess process = new(processId: 1234);
+        FakePipeReservation pipeReservation = new();
+        GatewayMetrics metrics = new();
+        WorkerProcessLauncher launcher = CreateLauncher(
+            executablePath,
+            new FakeWorkerProcessFactory(process),
+            new FailingStartupProbe(),
+            metrics);
+
+        WorkerProcessLaunchException exception =
+            await Assert.ThrowsAsync<WorkerProcessLaunchException>(
+                async () => await launcher.LaunchAsync(CreateRequest(pipeReservation)));
+
+        Assert.Equal(WorkerProcessLaunchErrorCode.StartupFailed, exception.ErrorCode);
+        Assert.True(process.KillCalled);
+        Assert.True(process.DisposeCalled);
+        Assert.True(pipeReservation.DisposeCalled);
+        Assert.Equal(1, metrics.GetSnapshot().WorkerKills);
+    }
+
+    [Fact]
+    public async Task LaunchAsync_WhenStartupTimesOut_KillsAndDisposesWorker()
+    {
+        using TestDirectory directory = TestDirectory.Create();
+        string executablePath = directory.CreateWorkerExecutable(machine: 0x014c);
+        FakeWorkerProcess process = new(processId: 1234);
+        GatewayMetrics metrics = new();
+        WorkerProcessLauncher launcher = CreateLauncher(
+            executablePath,
+            new FakeWorkerProcessFactory(process),
+            new WaitingStartupProbe(),
+            metrics,
+            startupTimeoutSeconds: 1);
+
+        WorkerProcessLaunchException exception =
+            await Assert.ThrowsAsync<WorkerProcessLaunchException>(
+                async () => await launcher.LaunchAsync(CreateRequest()));
+
+        Assert.Equal(WorkerProcessLaunchErrorCode.StartupTimeout, exception.ErrorCode);
+        Assert.True(process.KillCalled);
+        Assert.True(process.DisposeCalled);
+        Assert.Equal(1, metrics.GetSnapshot().WorkerKills);
+    }
+
+    [Fact]
+    public async Task LaunchAsync_WhenExecutableDoesNotExist_FailsBeforeStartingProcess()
+    {
+        using TestDirectory directory = TestDirectory.Create();
+        string executablePath = Path.Combine(directory.Path, "missing-worker.exe");
+        FakeWorkerProcessFactory processFactory = new(new FakeWorkerProcess(processId: 1234));
+        WorkerProcessLauncher launcher = CreateLauncher(executablePath, processFactory, new SucceedingStartupProbe());
+
+        WorkerProcessLaunchException exception =
+            await Assert.ThrowsAsync<WorkerProcessLaunchException>(
+                async () => await launcher.LaunchAsync(CreateRequest()));
+
+        Assert.Equal(WorkerProcessLaunchErrorCode.ExecutableNotFound, exception.ErrorCode);
+        Assert.Null(processFactory.LastStartInfo);
+    }
+
+    [Fact]
+    public async Task LaunchAsync_WhenExecutableArchitectureDoesNotMatch_FailsBeforeStartingProcess()
+    {
+        using TestDirectory directory = TestDirectory.Create();
+        string executablePath = directory.CreateWorkerExecutable(machine: 0x8664);
+        FakeWorkerProcessFactory processFactory = new(new FakeWorkerProcess(processId: 1234));
+        WorkerProcessLauncher launcher = CreateLauncher(executablePath, processFactory, new SucceedingStartupProbe());
+
+        WorkerProcessLaunchException exception =
+            await Assert.ThrowsAsync<WorkerProcessLaunchException>(
+                async () => await launcher.LaunchAsync(CreateRequest()));
+
+        Assert.Equal(WorkerProcessLaunchErrorCode.InvalidExecutable, exception.ErrorCode);
+        Assert.Null(processFactory.LastStartInfo);
+    }
+
+    [Fact]
+    public async Task LaunchAsync_WhenWorkerAlreadyExited_FailsAndDisposesWorkerWithoutKill()
+    {
+        using TestDirectory directory = TestDirectory.Create();
+        string executablePath = directory.CreateWorkerExecutable(machine: 0x014c);
+        FakeWorkerProcess process = new(processId: 1234)
+        {
+            HasExited = true,
+            ExitCode = 42,
+        };
+        WorkerProcessLauncher launcher = CreateLauncher(
+            executablePath,
+            new FakeWorkerProcessFactory(process),
+            new WorkerProcessStartedProbe());
+
+        WorkerProcessLaunchException exception =
+            await Assert.ThrowsAsync<WorkerProcessLaunchException>(
+                async () => await launcher.LaunchAsync(CreateRequest()));
+
+        Assert.Equal(WorkerProcessLaunchErrorCode.StartupFailed, exception.ErrorCode);
+        Assert.False(process.KillCalled);
+        Assert.True(process.DisposeCalled);
+    }
+
+    private static WorkerProcessLauncher CreateLauncher(
+        string executablePath,
+        IWorkerProcessFactory processFactory,
+        IWorkerStartupProbe startupProbe,
+        GatewayMetrics? metrics = null,
+        int startupTimeoutSeconds = 30)
+    {
+        GatewayOptions options = new()
+        {
+            Worker = new WorkerOptions
+            {
+                ExecutablePath = executablePath,
+                RequiredArchitecture = WorkerArchitecture.X86,
+                StartupTimeoutSeconds = startupTimeoutSeconds,
+            },
+        };
+
+        return new WorkerProcessLauncher(
+            Options.Create(options),
+            processFactory,
+            startupProbe,
+            metrics ?? new GatewayMetrics());
+    }
+
+    private static WorkerProcessLaunchRequest CreateRequest(IDisposable? pipeReservation = null)
+    {
+        return new WorkerProcessLaunchRequest(
+            SessionId,
+            PipeName,
+            GatewayContractInfo.WorkerProtocolVersion,
+            Nonce,
+            pipeReservation);
+    }
+
+    private sealed class FakeWorkerProcessFactory(IWorkerProcess process) : IWorkerProcessFactory
+    {
+        public ProcessStartInfo? LastStartInfo { get; private set; }
+
+        public IWorkerProcess Start(ProcessStartInfo startInfo)
+        {
+            LastStartInfo = startInfo;
+            return process;
+        }
+    }
+
+    private sealed class FakeWorkerProcess(int processId) : IWorkerProcess
+    {
+        public int Id { get; } = processId;
+
+        public bool HasExited { get; set; }
+
+        public int? ExitCode { get; set; }
+
+        public bool DisposeCalled { get; private set; }
+
+        public bool KillCalled { get; private set; }
+
+        public ValueTask WaitForExitAsync(CancellationToken cancellationToken)
+        {
+            return ValueTask.CompletedTask;
+        }
+
+        public void Kill(bool entireProcessTree)
+        {
+            Assert.True(entireProcessTree);
+            KillCalled = true;
+            HasExited = true;
+        }
+
+        public void Dispose()
+        {
+            DisposeCalled = true;
+        }
+    }
+
+    private sealed class SucceedingStartupProbe : IWorkerStartupProbe
+    {
+        public Task WaitUntilReadyAsync(
+            IWorkerProcess process,
+            WorkerProcessLaunchRequest request,
+            CancellationToken cancellationToken)
+        {
+            return Task.CompletedTask;
+        }
+    }
+
+    private sealed class FailingStartupProbe : IWorkerStartupProbe
+    {
+        public Task WaitUntilReadyAsync(
+            IWorkerProcess process,
+            WorkerProcessLaunchRequest request,
+            CancellationToken cancellationToken)
+        {
+            throw new InvalidOperationException("Fake worker startup failed.");
+        }
+    }
+
+    private sealed class WaitingStartupProbe : IWorkerStartupProbe
+    {
+        public async Task WaitUntilReadyAsync(
+            IWorkerProcess process,
+            WorkerProcessLaunchRequest request,
+            CancellationToken cancellationToken)
+        {
+            await Task.Delay(Timeout.InfiniteTimeSpan, cancellationToken);
+        }
+    }
+
+    private sealed class FakePipeReservation : IDisposable
+    {
+        public bool DisposeCalled { get; private set; }
+
+        public void Dispose()
+        {
+            DisposeCalled = true;
+        }
+    }
+
+    private sealed class TestDirectory : IDisposable
+    {
+        private TestDirectory(string path)
+        {
+            Path = path;
+        }
+
+        public string Path { get; }
+
+        public static TestDirectory Create()
+        {
+            string path = System.IO.Path.Combine(System.IO.Path.GetTempPath(), $"mxgateway-tests-{Guid.NewGuid():N}");
+            Directory.CreateDirectory(path);
+
+            return new TestDirectory(path);
+        }
+
+        public string CreateWorkerExecutable(ushort machine)
+        {
+            string path = System.IO.Path.Combine(Path, "MxGateway.Worker.exe");
+            byte[] bytes = new byte[0x100];
+            bytes[0] = (byte)'M';
+            bytes[1] = (byte)'Z';
+            BitConverter.GetBytes(0x80).CopyTo(bytes, 0x3c);
+            bytes[0x80] = (byte)'P';
+            bytes[0x81] = (byte)'E';
+            bytes[0x82] = 0;
+            bytes[0x83] = 0;
+            BitConverter.GetBytes(machine).CopyTo(bytes, 0x84);
+            File.WriteAllBytes(path, bytes);
+
+            return path;
+        }
+
+        public void Dispose()
+        {
+            Directory.Delete(Path, recursive: true);
+        }
+    }
+}

src/MxGateway.Tests/Metrics/GatewayMetricsTests.cs

@@ -0,0 +1,60 @@
+using MxGateway.Server.Metrics;
+
+namespace MxGateway.Tests.Metrics;
+
+public sealed class GatewayMetricsTests
+{
+    [Fact]
+    public void GetSnapshot_ReflectsSessionWorkerCommandEventAndFaultUpdates()
+    {
+        using GatewayMetrics metrics = new();
+
+        metrics.SessionOpened();
+        metrics.WorkerStarted(TimeSpan.FromMilliseconds(250));
+        metrics.CommandStarted("Register");
+        metrics.CommandSucceeded("Register", TimeSpan.FromMilliseconds(10));
+        metrics.CommandStarted("WriteSecured");
+        metrics.CommandFailed("WriteSecured", "AuthorizationFailed", TimeSpan.FromMilliseconds(12));
+        metrics.EventReceived("session-1", "OnDataChange");
+        metrics.EventReceived("session-1", "OnDataChange");
+        metrics.SetEventQueueDepth(7);
+        metrics.QueueOverflow("session-events");
+        metrics.Fault("CommandTimeout");
+        metrics.WorkerKilled("CommandTimeout");
+        metrics.WorkerStopped("Killed");
+        metrics.HeartbeatFailed("session-1");
+        metrics.StreamDisconnected("ClientCancelled");
+        metrics.SessionClosed();
+
+        GatewayMetricsSnapshot snapshot = metrics.GetSnapshot();
+
+        Assert.Equal(0, snapshot.OpenSessions);
+        Assert.Equal(0, snapshot.WorkersRunning);
+        Assert.Equal(7, snapshot.EventQueueDepth);
+        Assert.Equal(1, snapshot.SessionsOpened);
+        Assert.Equal(1, snapshot.SessionsClosed);
+        Assert.Equal(2, snapshot.CommandsStarted);
+        Assert.Equal(1, snapshot.CommandsSucceeded);
+        Assert.Equal(1, snapshot.CommandsFailed);
+        Assert.Equal(2, snapshot.EventsReceived);
+        Assert.Equal(1, snapshot.QueueOverflows);
+        Assert.Equal(1, snapshot.Faults);
+        Assert.Equal(1, snapshot.WorkerKills);
+        Assert.Equal(1, snapshot.WorkerExits);
+        Assert.Equal(1, snapshot.HeartbeatFailures);
+        Assert.Equal(1, snapshot.StreamDisconnects);
+        Assert.Equal(1, snapshot.CommandFailuresByMethod["WriteSecured"]);
+        Assert.Equal(2, snapshot.EventsByFamily["OnDataChange"]);
+    }
+
+    [Fact]
+    public void SetEventQueueDepth_RejectsNegativeDepth()
+    {
+        using GatewayMetrics metrics = new();
+
+        ArgumentOutOfRangeException exception = Assert.Throws<ArgumentOutOfRangeException>(
+            () => metrics.SetEventQueueDepth(-1));
+
+        Assert.Equal("depth", exception.ParamName);
+    }
+}

src/MxGateway.Tests/Security/Authentication/ApiKeyAdminCliRunnerTests.cs

@@ -0,0 +1,242 @@
+using System.Text.Json;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using MxGateway.Server.Configuration;
+using MxGateway.Server.Security.Authentication;
+
+namespace MxGateway.Tests.Security.Authentication;
+
+public sealed class ApiKeyAdminCliRunnerTests
+{
+    [Fact]
+    public async Task CreateKeyAsync_CreatesAuthenticatingKeyAndAudits()
+    {
+        await using ServiceProvider services = BuildServices(CreateTempDatabasePath());
+        ApiKeyAdminCliRunner runner = services.GetRequiredService<ApiKeyAdminCliRunner>();
+        StringWriter output = new();
+
+        await runner.RunAsync(
+            new ApiKeyAdminCommand(
+                Kind: ApiKeyAdminCommandKind.CreateKey,
+                Json: true,
+                SqlitePath: null,
+                Pepper: null,
+                KeyId: "operator01",
+                DisplayName: "Operator",
+                Scopes: new HashSet<string>(StringComparer.Ordinal) { "session:open", "events:read" }),
+            output,
+            CancellationToken.None);
+
+        string apiKey = ReadApiKey(output.ToString());
+
+        IApiKeyVerifier verifier = services.GetRequiredService<IApiKeyVerifier>();
+        ApiKeyVerificationResult verification = await verifier.VerifyAsync($"Bearer {apiKey}", CancellationToken.None);
+
+        Assert.True(verification.Succeeded);
+        Assert.NotNull(verification.Identity);
+        Assert.Equal("operator01", verification.Identity.KeyId);
+        Assert.Contains("session:open", verification.Identity.Scopes);
+
+        IReadOnlyList<ApiKeyAuditRecord> auditRecords = await services
+            .GetRequiredService<IApiKeyAuditStore>()
+            .ListRecentAsync(10, CancellationToken.None);
+
+        Assert.Contains(auditRecords, record => record.EventType == "create-key" && record.KeyId == "operator01");
+    }
+
+    [Fact]
+    public async Task ListKeysAsync_DoesNotPrintRawSecret()
+    {
+        await using ServiceProvider services = BuildServices(CreateTempDatabasePath());
+        ApiKeyAdminCliRunner runner = services.GetRequiredService<ApiKeyAdminCliRunner>();
+        string apiKey = await CreateKeyAsync(runner, "operator01");
+        StringWriter listOutput = new();
+
+        await runner.RunAsync(
+            new ApiKeyAdminCommand(
+                Kind: ApiKeyAdminCommandKind.ListKeys,
+                Json: true,
+                SqlitePath: null,
+                Pepper: null,
+                KeyId: null,
+                DisplayName: null,
+                Scopes: new HashSet<string>(StringComparer.Ordinal)),
+            listOutput,
+            CancellationToken.None);
+
+        string listJson = listOutput.ToString();
+
+        Assert.Contains("operator01", listJson, StringComparison.Ordinal);
+        Assert.DoesNotContain(apiKey, listJson, StringComparison.Ordinal);
+        Assert.DoesNotContain(ApiKeySecret(apiKey), listJson, StringComparison.Ordinal);
+        Assert.DoesNotContain("secret_hash", listJson, StringComparison.OrdinalIgnoreCase);
+    }
+
+    [Fact]
+    public async Task RevokeKeyAsync_RevokedKeyFailsVerificationAndAudits()
+    {
+        await using ServiceProvider services = BuildServices(CreateTempDatabasePath());
+        ApiKeyAdminCliRunner runner = services.GetRequiredService<ApiKeyAdminCliRunner>();
+        string apiKey = await CreateKeyAsync(runner, "operator01");
+
+        await runner.RunAsync(
+            new ApiKeyAdminCommand(
+                Kind: ApiKeyAdminCommandKind.RevokeKey,
+                Json: true,
+                SqlitePath: null,
+                Pepper: null,
+                KeyId: "operator01",
+                DisplayName: null,
+                Scopes: new HashSet<string>(StringComparer.Ordinal)),
+            TextWriter.Null,
+            CancellationToken.None);
+
+        ApiKeyVerificationResult verification = await services
+            .GetRequiredService<IApiKeyVerifier>()
+            .VerifyAsync($"Bearer {apiKey}", CancellationToken.None);
+
+        Assert.False(verification.Succeeded);
+        Assert.Equal(ApiKeyVerificationFailure.KeyRevoked, verification.Failure);
+
+        IReadOnlyList<ApiKeyAuditRecord> auditRecords = await services
+            .GetRequiredService<IApiKeyAuditStore>()
+            .ListRecentAsync(10, CancellationToken.None);
+
+        Assert.Contains(auditRecords, record => record.EventType == "revoke-key" && record.KeyId == "operator01");
+    }
+
+    [Fact]
+    public async Task RotateKeyAsync_PrintsNewSecretOnceAndInvalidatesOldSecret()
+    {
+        await using ServiceProvider services = BuildServices(CreateTempDatabasePath());
+        ApiKeyAdminCliRunner runner = services.GetRequiredService<ApiKeyAdminCliRunner>();
+        string oldApiKey = await CreateKeyAsync(runner, "operator01");
+        StringWriter rotateOutput = new();
+
+        await runner.RunAsync(
+            new ApiKeyAdminCommand(
+                Kind: ApiKeyAdminCommandKind.RotateKey,
+                Json: true,
+                SqlitePath: null,
+                Pepper: null,
+                KeyId: "operator01",
+                DisplayName: null,
+                Scopes: new HashSet<string>(StringComparer.Ordinal)),
+            rotateOutput,
+            CancellationToken.None);
+
+        string rotateJson = rotateOutput.ToString();
+        string newApiKey = ReadApiKey(rotateJson);
+
+        Assert.NotEqual(oldApiKey, newApiKey);
+        Assert.Equal(1, CountOccurrences(rotateJson, newApiKey));
+
+        IApiKeyVerifier verifier = services.GetRequiredService<IApiKeyVerifier>();
+        ApiKeyVerificationResult oldVerification = await verifier.VerifyAsync($"Bearer {oldApiKey}", CancellationToken.None);
+        ApiKeyVerificationResult newVerification = await verifier.VerifyAsync($"Bearer {newApiKey}", CancellationToken.None);
+
+        Assert.False(oldVerification.Succeeded);
+        Assert.Equal(ApiKeyVerificationFailure.SecretMismatch, oldVerification.Failure);
+        Assert.True(newVerification.Succeeded);
+    }
+
+    [Fact]
+    public async Task CreateKeyAsync_PrintsRawSecretExactlyOnce()
+    {
+        await using ServiceProvider services = BuildServices(CreateTempDatabasePath());
+        ApiKeyAdminCliRunner runner = services.GetRequiredService<ApiKeyAdminCliRunner>();
+        StringWriter output = new();
+
+        await runner.RunAsync(
+            new ApiKeyAdminCommand(
+                Kind: ApiKeyAdminCommandKind.CreateKey,
+                Json: true,
+                SqlitePath: null,
+                Pepper: null,
+                KeyId: "operator01",
+                DisplayName: "Operator",
+                Scopes: new HashSet<string>(StringComparer.Ordinal)),
+            output,
+            CancellationToken.None);
+
+        string json = output.ToString();
+        string apiKey = ReadApiKey(json);
+
+        Assert.Equal(1, CountOccurrences(json, apiKey));
+        Assert.Equal(1, CountOccurrences(json, ApiKeySecret(apiKey)));
+    }
+
+    private static async Task<string> CreateKeyAsync(ApiKeyAdminCliRunner runner, string keyId)
+    {
+        StringWriter output = new();
+        await runner.RunAsync(
+            new ApiKeyAdminCommand(
+                Kind: ApiKeyAdminCommandKind.CreateKey,
+                Json: true,
+                SqlitePath: null,
+                Pepper: null,
+                KeyId: keyId,
+                DisplayName: "Operator",
+                Scopes: new HashSet<string>(StringComparer.Ordinal) { "session:open" }),
+            output,
+            CancellationToken.None);
+
+        return ReadApiKey(output.ToString());
+    }
+
+    private static ServiceProvider BuildServices(string databasePath)
+    {
+        IConfigurationRoot configuration = new ConfigurationBuilder()
+            .AddInMemoryCollection(
+                new Dictionary<string, string?>
+                {
+                    ["MxGateway:Authentication:SqlitePath"] = databasePath,
+                    ["MxGateway:ApiKeyPepper"] = "test-pepper"
+                })
+            .Build();
+
+        ServiceCollection services = new();
+        services.AddSingleton<IConfiguration>(configuration);
+        services.AddGatewayConfiguration();
+        services.AddSqliteAuthStore();
+
+        return services.BuildServiceProvider(validateScopes: true);
+    }
+
+    private static string CreateTempDatabasePath()
+    {
+        string directory = Path.Combine(Path.GetTempPath(), "mxgateway-auth-cli-tests", Guid.NewGuid().ToString("N"));
+        Directory.CreateDirectory(directory);
+
+        return Path.Combine(directory, "gateway-auth.db");
+    }
+
+    private static string ReadApiKey(string json)
+    {
+        using JsonDocument document = JsonDocument.Parse(json);
+
+        return document.RootElement.GetProperty("ApiKey").GetString()
+            ?? throw new InvalidOperationException("API key was not present in command output.");
+    }
+
+    private static string ApiKeySecret(string apiKey)
+    {
+        string[] parts = apiKey.Split('_', 3);
+
+        return parts[2];
+    }
+
+    private static int CountOccurrences(string value, string pattern)
+    {
+        int count = 0;
+        int index = 0;
+
+        while ((index = value.IndexOf(pattern, index, StringComparison.Ordinal)) >= 0)
+        {
+            count++;
+            index += pattern.Length;
+        }
+
+        return count;
+    }
+}

src/MxGateway.Tests/Security/Authentication/ApiKeyAdminCommandLineParserTests.cs

@@ -0,0 +1,70 @@
+using MxGateway.Server.Security.Authentication;
+
+namespace MxGateway.Tests.Security.Authentication;
+
+public sealed class ApiKeyAdminCommandLineParserTests
+{
+    [Fact]
+    public void Parse_NonApiKeyCommand_ReturnsNotApiKeyCommand()
+    {
+        ApiKeyAdminParseResult result = ApiKeyAdminCommandLineParser.Parse(["--urls=http://localhost:5000"]);
+
+        Assert.False(result.IsApiKeyCommand);
+        Assert.Null(result.Command);
+    }
+
+    [Fact]
+    public void Parse_CreateKeyCommand_ReturnsOptions()
+    {
+        ApiKeyAdminParseResult result = ApiKeyAdminCommandLineParser.Parse(
+            [
+                "apikey",
+                "create-key",
+                "--key-id",
+                "operator01",
+                "--display-name",
+                "Operator",
+                "--scopes",
+                "session:open,events:read",
+                "--sqlite-path",
+                "auth.db",
+                "--pepper",
+                "pepper",
+                "--json"
+            ]);
+
+        Assert.True(result.IsApiKeyCommand);
+        Assert.Null(result.Error);
+        Assert.NotNull(result.Command);
+        Assert.Equal(ApiKeyAdminCommandKind.CreateKey, result.Command.Kind);
+        Assert.True(result.Command.Json);
+        Assert.Equal("operator01", result.Command.KeyId);
+        Assert.Equal("Operator", result.Command.DisplayName);
+        Assert.Equal("auth.db", result.Command.SqlitePath);
+        Assert.Equal("pepper", result.Command.Pepper);
+        Assert.Contains("session:open", result.Command.Scopes);
+        Assert.Contains("events:read", result.Command.Scopes);
+    }
+
+    [Fact]
+    public void Parse_CreateKeyWithoutDisplayName_ReturnsError()
+    {
+        ApiKeyAdminParseResult result = ApiKeyAdminCommandLineParser.Parse(
+            ["apikey", "create-key", "--key-id", "operator01"]);
+
+        Assert.True(result.IsApiKeyCommand);
+        Assert.Null(result.Command);
+        Assert.Contains("--display-name", result.Error, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void Parse_KeyIdWithUnderscore_ReturnsError()
+    {
+        ApiKeyAdminParseResult result = ApiKeyAdminCommandLineParser.Parse(
+            ["apikey", "revoke-key", "--key-id", "operator_01"]);
+
+        Assert.True(result.IsApiKeyCommand);
+        Assert.Null(result.Command);
+        Assert.Contains("letters, numbers, periods, and hyphens", result.Error, StringComparison.Ordinal);
+    }
+}

src/MxGateway.Tests/Security/Authentication/ApiKeyParserTests.cs

@@ -0,0 +1,38 @@
+using MxGateway.Server.Security.Authentication;
+
+namespace MxGateway.Tests.Security.Authentication;
+
+public sealed class ApiKeyParserTests
+{
+    [Fact]
+    public void TryParseAuthorizationHeader_ValidBearerToken_ReturnsKeyIdAndSecret()
+    {
+        ApiKeyParser parser = new();
+
+        bool parsed = parser.TryParseAuthorizationHeader(
+            "Bearer mxgw_operator01_secret_value",
+            out ParsedApiKey? apiKey);
+
+        Assert.True(parsed);
+        Assert.NotNull(apiKey);
+        Assert.Equal("operator01", apiKey.KeyId);
+        Assert.Equal("secret_value", apiKey.Secret);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("mxgw_operator01_secret")]
+    [InlineData("Bearer not-a-gateway-key")]
+    [InlineData("Bearer mxgw__secret")]
+    [InlineData("Bearer mxgw_operator01_")]
+    public void TryParseAuthorizationHeader_MalformedToken_ReturnsFalse(string? authorizationHeader)
+    {
+        ApiKeyParser parser = new();
+
+        bool parsed = parser.TryParseAuthorizationHeader(authorizationHeader, out ParsedApiKey? apiKey);
+
+        Assert.False(parsed);
+        Assert.Null(apiKey);
+    }
+}

src/MxGateway.Tests/Security/Authentication/ApiKeySecretHasherTests.cs

@@ -0,0 +1,62 @@
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Options;
+using MxGateway.Server.Configuration;
+using MxGateway.Server.Security.Authentication;
+
+namespace MxGateway.Tests.Security.Authentication;
+
+public sealed class ApiKeySecretHasherTests
+{
+    [Fact]
+    public void HashSecret_SamePepperAndSecret_ReturnsSameHash()
+    {
+        ApiKeySecretHasher hasher = CreateHasher("pepper-one");
+
+        byte[] firstHash = hasher.HashSecret("raw-secret");
+        byte[] secondHash = hasher.HashSecret("raw-secret");
+
+        Assert.Equal(firstHash, secondHash);
+        Assert.NotEqual("raw-secret"u8.ToArray(), firstHash);
+    }
+
+    [Fact]
+    public void HashSecret_DifferentPepper_ReturnsDifferentHash()
+    {
+        byte[] firstHash = CreateHasher("pepper-one").HashSecret("raw-secret");
+        byte[] secondHash = CreateHasher("pepper-two").HashSecret("raw-secret");
+
+        Assert.NotEqual(firstHash, secondHash);
+    }
+
+    [Fact]
+    public void HashSecret_MissingPepper_Throws()
+    {
+        ApiKeySecretHasher hasher = CreateHasher(pepper: null);
+
+        Assert.Throws<ApiKeyPepperUnavailableException>(() => hasher.HashSecret("raw-secret"));
+    }
+
+    private static ApiKeySecretHasher CreateHasher(string? pepper)
+    {
+        Dictionary<string, string?> values = [];
+
+        if (pepper is not null)
+        {
+            values["TestPepper"] = pepper;
+        }
+
+        IConfigurationRoot configuration = new ConfigurationBuilder()
+            .AddInMemoryCollection(values)
+            .Build();
+
+        GatewayOptions options = new()
+        {
+            Authentication = new AuthenticationOptions
+            {
+                PepperSecretName = "TestPepper"
+            }
+        };
+
+        return new ApiKeySecretHasher(configuration, Options.Create(options));
+    }
+}

src/MxGateway.Tests/Security/Authentication/ApiKeyVerifierTests.cs

@@ -0,0 +1,193 @@
+using System.Text.Json;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Options;
+using MxGateway.Server.Configuration;
+using MxGateway.Server.Security.Authentication;
+
+namespace MxGateway.Tests.Security.Authentication;
+
+public sealed class ApiKeyVerifierTests
+{
+    [Fact]
+    public async Task VerifyAsync_ValidKey_ReturnsIdentityAndScopes()
+    {
+        ApiKeySecretHasher hasher = CreateHasher("pepper");
+        FakeApiKeyStore store = new(CreateRecord(hasher, revokedUtc: null));
+        ApiKeyVerifier verifier = new(new ApiKeyParser(), hasher, store);
+
+        ApiKeyVerificationResult result = await verifier.VerifyAsync(
+            "Bearer mxgw_operator01_correct-secret",
+            CancellationToken.None);
+
+        Assert.True(result.Succeeded);
+        Assert.NotNull(result.Identity);
+        Assert.Equal("operator01", result.Identity.KeyId);
+        Assert.Equal("Operator Key", result.Identity.DisplayName);
+        Assert.Contains("session:open", result.Identity.Scopes);
+        Assert.Contains("events:read", result.Identity.Scopes);
+        Assert.True(store.MarkedUsed);
+    }
+
+    [Fact]
+    public async Task VerifyAsync_ValidKey_DoesNotExposeRawSecretInResult()
+    {
+        ApiKeySecretHasher hasher = CreateHasher("pepper");
+        FakeApiKeyStore store = new(CreateRecord(hasher, revokedUtc: null));
+        ApiKeyVerifier verifier = new(new ApiKeyParser(), hasher, store);
+
+        ApiKeyVerificationResult result = await verifier.VerifyAsync(
+            "Bearer mxgw_operator01_correct-secret",
+            CancellationToken.None);
+
+        string serialized = JsonSerializer.Serialize(result);
+
+        Assert.DoesNotContain("correct-secret", serialized, StringComparison.Ordinal);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("Bearer mxgw_operator01")]
+    [InlineData("Bearer wrong")]
+    public async Task VerifyAsync_MalformedKey_FailsUnauthenticated(string? authorizationHeader)
+    {
+        ApiKeyVerifier verifier = new(
+            new ApiKeyParser(),
+            CreateHasher("pepper"),
+            new FakeApiKeyStore(storedKey: null));
+
+        ApiKeyVerificationResult result = await verifier.VerifyAsync(
+            authorizationHeader,
+            CancellationToken.None);
+
+        Assert.False(result.Succeeded);
+        Assert.Equal(ApiKeyVerificationFailure.MissingOrMalformedCredentials, result.Failure);
+    }
+
+    [Fact]
+    public async Task VerifyAsync_UnknownKey_Fails()
+    {
+        ApiKeyVerifier verifier = new(
+            new ApiKeyParser(),
+            CreateHasher("pepper"),
+            new FakeApiKeyStore(storedKey: null));
+
+        ApiKeyVerificationResult result = await verifier.VerifyAsync(
+            "Bearer mxgw_missing_secret",
+            CancellationToken.None);
+
+        Assert.False(result.Succeeded);
+        Assert.Equal(ApiKeyVerificationFailure.KeyNotFound, result.Failure);
+    }
+
+    [Fact]
+    public async Task VerifyAsync_WrongSecret_Fails()
+    {
+        ApiKeySecretHasher hasher = CreateHasher("pepper");
+        FakeApiKeyStore store = new(CreateRecord(hasher, revokedUtc: null));
+        ApiKeyVerifier verifier = new(new ApiKeyParser(), hasher, store);
+
+        ApiKeyVerificationResult result = await verifier.VerifyAsync(
+            "Bearer mxgw_operator01_wrong-secret",
+            CancellationToken.None);
+
+        Assert.False(result.Succeeded);
+        Assert.Equal(ApiKeyVerificationFailure.SecretMismatch, result.Failure);
+        Assert.False(store.MarkedUsed);
+    }
+
+    [Fact]
+    public async Task VerifyAsync_RevokedKey_Fails()
+    {
+        ApiKeySecretHasher hasher = CreateHasher("pepper");
+        FakeApiKeyStore store = new(CreateRecord(hasher, DateTimeOffset.UtcNow));
+        ApiKeyVerifier verifier = new(new ApiKeyParser(), hasher, store);
+
+        ApiKeyVerificationResult result = await verifier.VerifyAsync(
+            "Bearer mxgw_operator01_correct-secret",
+            CancellationToken.None);
+
+        Assert.False(result.Succeeded);
+        Assert.Equal(ApiKeyVerificationFailure.KeyRevoked, result.Failure);
+        Assert.False(store.MarkedUsed);
+    }
+
+    [Fact]
+    public async Task VerifyAsync_MissingPepper_Fails()
+    {
+        FakeApiKeyStore store = new(CreateRecord(CreateHasher("pepper"), revokedUtc: null));
+        ApiKeyVerifier verifier = new(new ApiKeyParser(), CreateHasher(pepper: null), store);
+
+        ApiKeyVerificationResult result = await verifier.VerifyAsync(
+            "Bearer mxgw_operator01_correct-secret",
+            CancellationToken.None);
+
+        Assert.False(result.Succeeded);
+        Assert.Equal(ApiKeyVerificationFailure.PepperUnavailable, result.Failure);
+    }
+
+    private static ApiKeyRecord CreateRecord(ApiKeySecretHasher hasher, DateTimeOffset? revokedUtc)
+    {
+        return new ApiKeyRecord(
+            KeyId: "operator01",
+            KeyPrefix: "mxgw_operator01",
+            SecretHash: hasher.HashSecret("correct-secret"),
+            DisplayName: "Operator Key",
+            Scopes: new HashSet<string>(StringComparer.Ordinal)
+            {
+                "session:open",
+                "events:read"
+            },
+            CreatedUtc: DateTimeOffset.UtcNow,
+            LastUsedUtc: null,
+            RevokedUtc: revokedUtc);
+    }
+
+    private static ApiKeySecretHasher CreateHasher(string? pepper)
+    {
+        Dictionary<string, string?> values = [];
+
+        if (pepper is not null)
+        {
+            values["TestPepper"] = pepper;
+        }
+
+        IConfigurationRoot configuration = new ConfigurationBuilder()
+            .AddInMemoryCollection(values)
+            .Build();
+
+        GatewayOptions options = new()
+        {
+            Authentication = new AuthenticationOptions
+            {
+                PepperSecretName = "TestPepper"
+            }
+        };
+
+        return new ApiKeySecretHasher(configuration, Options.Create(options));
+    }
+
+    private sealed class FakeApiKeyStore(ApiKeyRecord? storedKey) : IApiKeyStore
+    {
+        public bool MarkedUsed { get; private set; }
+
+        public Task<ApiKeyRecord?> FindByKeyIdAsync(string keyId, CancellationToken cancellationToken)
+        {
+            return Task.FromResult(storedKey?.KeyId == keyId ? storedKey : null);
+        }
+
+        public Task<ApiKeyRecord?> FindActiveByKeyIdAsync(string keyId, CancellationToken cancellationToken)
+        {
+            return Task.FromResult(
+                storedKey?.KeyId == keyId && storedKey.RevokedUtc is null
+                    ? storedKey
+                    : null);
+        }
+
+        public Task MarkKeyUsedAsync(string keyId, DateTimeOffset usedUtc, CancellationToken cancellationToken)
+        {
+            MarkedUsed = storedKey?.KeyId == keyId;
+
+            return Task.CompletedTask;
+        }
+    }
+}

src/MxGateway.Tests/Security/Authentication/SqliteAuthStoreTests.cs

@@ -0,0 +1,280 @@
+using Microsoft.AspNetCore.Builder;
+using Microsoft.Data.Sqlite;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using MxGateway.Server;
+using MxGateway.Server.Configuration;
+using MxGateway.Server.Security.Authentication;
+
+namespace MxGateway.Tests.Security.Authentication;
+
+public sealed class SqliteAuthStoreTests
+{
+    [Fact]
+    public async Task MigrateAsync_EmptyDatabase_InitializesCurrentSchema()
+    {
+        string databasePath = CreateTempDatabasePath();
+        await using ServiceProvider services = BuildAuthServices(databasePath);
+
+        IAuthStoreMigrator migrator = services.GetRequiredService<IAuthStoreMigrator>();
+
+        await migrator.MigrateAsync(CancellationToken.None);
+
+        Assert.Equal(SqliteAuthSchema.CurrentVersion, await ReadSchemaVersionAsync(databasePath));
+        Assert.True(await TableExistsAsync(databasePath, SqliteAuthSchema.ApiKeysTable));
+        Assert.True(await TableExistsAsync(databasePath, SqliteAuthSchema.ApiKeyAuditTable));
+    }
+
+    [Fact]
+    public async Task MigrateAsync_ExistingVersionZeroDatabase_MigratesIdempotently()
+    {
+        string databasePath = CreateTempDatabasePath();
+        await CreateVersionZeroDatabaseAsync(databasePath);
+        await using ServiceProvider services = BuildAuthServices(databasePath);
+
+        IAuthStoreMigrator migrator = services.GetRequiredService<IAuthStoreMigrator>();
+
+        await migrator.MigrateAsync(CancellationToken.None);
+        await migrator.MigrateAsync(CancellationToken.None);
+
+        Assert.Equal(SqliteAuthSchema.CurrentVersion, await ReadSchemaVersionAsync(databasePath));
+        Assert.True(await TableExistsAsync(databasePath, SqliteAuthSchema.ApiKeysTable));
+        Assert.True(await TableExistsAsync(databasePath, SqliteAuthSchema.ApiKeyAuditTable));
+    }
+
+    [Fact]
+    public async Task StartAsync_NewerSchemaVersion_BlocksStartup()
+    {
+        string databasePath = CreateTempDatabasePath();
+        await CreateSchemaVersionDatabaseAsync(databasePath, SqliteAuthSchema.CurrentVersion + 1);
+
+        await using WebApplication app = GatewayApplication.Build(
+            [
+                $"--MxGateway:Authentication:SqlitePath={databasePath}",
+                "--urls=http://127.0.0.1:0"
+            ]);
+
+        AuthStoreMigrationException exception = await Assert.ThrowsAsync<AuthStoreMigrationException>(
+            () => app.StartAsync(CancellationToken.None));
+
+        Assert.Contains("newer than supported version", exception.Message, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public async Task FindActiveByKeyIdAsync_ExistingActiveKey_ReturnsKey()
+    {
+        string databasePath = CreateTempDatabasePath();
+        await using ServiceProvider services = BuildAuthServices(databasePath);
+        await services.GetRequiredService<IAuthStoreMigrator>().MigrateAsync(CancellationToken.None);
+        await InsertApiKeyAsync(databasePath, revokedUtc: null);
+
+        IApiKeyStore store = services.GetRequiredService<IApiKeyStore>();
+
+        ApiKeyRecord? key = await store.FindActiveByKeyIdAsync("test-key", CancellationToken.None);
+
+        Assert.NotNull(key);
+        Assert.Equal("test-key", key.KeyId);
+        Assert.Equal("mxgw_test", key.KeyPrefix);
+        Assert.Equal([1, 2, 3, 4], key.SecretHash);
+        Assert.Contains("session:open", key.Scopes);
+        Assert.Null(key.RevokedUtc);
+    }
+
+    [Fact]
+    public async Task FindActiveByKeyIdAsync_RevokedKey_ReturnsNull()
+    {
+        string databasePath = CreateTempDatabasePath();
+        await using ServiceProvider services = BuildAuthServices(databasePath);
+        await services.GetRequiredService<IAuthStoreMigrator>().MigrateAsync(CancellationToken.None);
+        await InsertApiKeyAsync(databasePath, DateTimeOffset.UtcNow);
+
+        IApiKeyStore store = services.GetRequiredService<IApiKeyStore>();
+
+        ApiKeyRecord? activeKey = await store.FindActiveByKeyIdAsync(
+            "test-key",
+            CancellationToken.None);
+        ApiKeyRecord? storedKey = await store.FindByKeyIdAsync("test-key", CancellationToken.None);
+
+        Assert.Null(activeKey);
+        Assert.NotNull(storedKey);
+        Assert.NotNull(storedKey.RevokedUtc);
+    }
+
+    [Fact]
+    public async Task ApiKeyAuditStore_AppendAsync_PersistsAuditEvent()
+    {
+        string databasePath = CreateTempDatabasePath();
+        await using ServiceProvider services = BuildAuthServices(databasePath);
+        await services.GetRequiredService<IAuthStoreMigrator>().MigrateAsync(CancellationToken.None);
+
+        IApiKeyAuditStore auditStore = services.GetRequiredService<IApiKeyAuditStore>();
+
+        await auditStore.AppendAsync(
+            new ApiKeyAuditEntry(
+                KeyId: "test-key",
+                EventType: "lookup",
+                RemoteAddress: "127.0.0.1",
+                Details: "matched active key"),
+            CancellationToken.None);
+
+        IReadOnlyList<ApiKeyAuditRecord> records = await auditStore.ListRecentAsync(
+            10,
+            CancellationToken.None);
+
+        ApiKeyAuditRecord record = Assert.Single(records);
+        Assert.Equal("test-key", record.KeyId);
+        Assert.Equal("lookup", record.EventType);
+        Assert.Equal("127.0.0.1", record.RemoteAddress);
+        Assert.Equal("matched active key", record.Details);
+    }
+
+    private static ServiceProvider BuildAuthServices(string databasePath)
+    {
+        IConfigurationRoot configuration = new ConfigurationBuilder()
+            .AddInMemoryCollection(
+                new Dictionary<string, string?>
+                {
+                    ["MxGateway:Authentication:SqlitePath"] = databasePath
+                })
+            .Build();
+
+        ServiceCollection services = new();
+        services.AddSingleton<IConfiguration>(configuration);
+        services.AddGatewayConfiguration();
+        services.AddSqliteAuthStore();
+
+        return services.BuildServiceProvider(validateScopes: true);
+    }
+
+    private static string CreateTempDatabasePath()
+    {
+        string directory = Path.Combine(Path.GetTempPath(), "mxgateway-auth-tests", Guid.NewGuid().ToString("N"));
+        Directory.CreateDirectory(directory);
+
+        return Path.Combine(directory, "gateway-auth.db");
+    }
+
+    private static async Task CreateVersionZeroDatabaseAsync(string databasePath)
+    {
+        await using SqliteConnection connection = CreateConnection(databasePath);
+        await connection.OpenAsync(CancellationToken.None);
+
+        await using SqliteCommand command = connection.CreateCommand();
+        command.CommandText = """
+            CREATE TABLE schema_version (
+                id INTEGER PRIMARY KEY CHECK (id = 1),
+                version INTEGER NOT NULL,
+                applied_utc TEXT NOT NULL
+            );
+
+            INSERT INTO schema_version (id, version, applied_utc)
+            VALUES (1, 0, $applied_utc);
+            """;
+        command.Parameters.AddWithValue("$applied_utc", DateTimeOffset.UtcNow.ToString("O"));
+
+        await command.ExecuteNonQueryAsync(CancellationToken.None);
+    }
+
+    private static async Task CreateSchemaVersionDatabaseAsync(string databasePath, int version)
+    {
+        await using SqliteConnection connection = CreateConnection(databasePath);
+        await connection.OpenAsync(CancellationToken.None);
+
+        await using SqliteCommand command = connection.CreateCommand();
+        command.CommandText = """
+            CREATE TABLE schema_version (
+                id INTEGER PRIMARY KEY CHECK (id = 1),
+                version INTEGER NOT NULL,
+                applied_utc TEXT NOT NULL
+            );
+
+            INSERT INTO schema_version (id, version, applied_utc)
+            VALUES (1, $version, $applied_utc);
+            """;
+        command.Parameters.AddWithValue("$version", version);
+        command.Parameters.AddWithValue("$applied_utc", DateTimeOffset.UtcNow.ToString("O"));
+
+        await command.ExecuteNonQueryAsync(CancellationToken.None);
+    }
+
+    private static async Task InsertApiKeyAsync(string databasePath, DateTimeOffset? revokedUtc)
+    {
+        await using SqliteConnection connection = CreateConnection(databasePath);
+        await connection.OpenAsync(CancellationToken.None);
+
+        await using SqliteCommand command = connection.CreateCommand();
+        command.CommandText = """
+            INSERT INTO api_keys (
+                key_id,
+                key_prefix,
+                secret_hash,
+                display_name,
+                scopes,
+                created_utc,
+                last_used_utc,
+                revoked_utc)
+            VALUES (
+                $key_id,
+                $key_prefix,
+                $secret_hash,
+                $display_name,
+                $scopes,
+                $created_utc,
+                NULL,
+                $revoked_utc);
+            """;
+        command.Parameters.AddWithValue("$key_id", "test-key");
+        command.Parameters.AddWithValue("$key_prefix", "mxgw_test");
+        command.Parameters.Add("$secret_hash", SqliteType.Blob).Value = new byte[] { 1, 2, 3, 4 };
+        command.Parameters.AddWithValue("$display_name", "Test Key");
+        command.Parameters.AddWithValue(
+            "$scopes",
+            ApiKeyScopeSerializer.Serialize(new HashSet<string>(StringComparer.Ordinal) { "session:open", "events:read" }));
+        command.Parameters.AddWithValue("$created_utc", DateTimeOffset.UtcNow.ToString("O"));
+        command.Parameters.AddWithValue("$revoked_utc", revokedUtc?.ToString("O") ?? (object)DBNull.Value);
+
+        await command.ExecuteNonQueryAsync(CancellationToken.None);
+    }
+
+    private static async Task<int> ReadSchemaVersionAsync(string databasePath)
+    {
+        await using SqliteConnection connection = CreateConnection(databasePath);
+        await connection.OpenAsync(CancellationToken.None);
+
+        await using SqliteCommand command = connection.CreateCommand();
+        command.CommandText = "SELECT version FROM schema_version WHERE id = 1;";
+
+        object? result = await command.ExecuteScalarAsync(CancellationToken.None);
+
+        return Convert.ToInt32(result, System.Globalization.CultureInfo.InvariantCulture);
+    }
+
+    private static async Task<bool> TableExistsAsync(string databasePath, string tableName)
+    {
+        await using SqliteConnection connection = CreateConnection(databasePath);
+        await connection.OpenAsync(CancellationToken.None);
+
+        await using SqliteCommand command = connection.CreateCommand();
+        command.CommandText = """
+            SELECT COUNT(*)
+            FROM sqlite_master
+            WHERE type = 'table' AND name = $table_name;
+            """;
+        command.Parameters.AddWithValue("$table_name", tableName);
+
+        long result = (long)(await command.ExecuteScalarAsync(CancellationToken.None) ?? 0L);
+
+        return result == 1;
+    }
+
+    private static SqliteConnection CreateConnection(string databasePath)
+    {
+        SqliteConnectionStringBuilder builder = new()
+        {
+            DataSource = databasePath,
+            Mode = SqliteOpenMode.ReadWriteCreate
+        };
+
+        return new SqliteConnection(builder.ToString());
+    }
+}

src/MxGateway.Worker.Tests/Bootstrap/MemoryWorkerEnvironment.cs

@@ -0,0 +1,37 @@
+using System;
+using System.Collections.Generic;
+using MxGateway.Worker.Bootstrap;
+
+namespace MxGateway.Worker.Tests.Bootstrap;
+
+internal sealed class MemoryWorkerEnvironment : IWorkerEnvironment
+{
+    private readonly Dictionary<string, string> _values = new();
+    private readonly Exception? _exception;
+
+    public MemoryWorkerEnvironment()
+    {
+    }
+
+    public MemoryWorkerEnvironment(Exception exception)
+    {
+        _exception = exception;
+    }
+
+    public void Set(string name, string value)
+    {
+        _values[name] = value;
+    }
+
+    public string? GetEnvironmentVariable(string name)
+    {
+        if (_exception is not null)
+        {
+            throw _exception;
+        }
+
+        return _values.TryGetValue(name, out string value)
+            ? value
+            : null;
+    }
+}

src/MxGateway.Worker.Tests/Bootstrap/MemoryWorkerLogEntry.cs

@@ -0,0 +1,22 @@
+using System.Collections.Generic;
+
+namespace MxGateway.Worker.Tests.Bootstrap;
+
+internal sealed class MemoryWorkerLogEntry
+{
+    public MemoryWorkerLogEntry(
+        string level,
+        string eventName,
+        IReadOnlyDictionary<string, object?> fields)
+    {
+        Level = level;
+        EventName = eventName;
+        Fields = fields;
+    }
+
+    public string Level { get; }
+
+    public string EventName { get; }
+
+    public IReadOnlyDictionary<string, object?> Fields { get; }
+}

src/MxGateway.Worker.Tests/Bootstrap/MemoryWorkerLogger.cs

@@ -0,0 +1,19 @@
+using System.Collections.Generic;
+using MxGateway.Worker.Bootstrap;
+
+namespace MxGateway.Worker.Tests.Bootstrap;
+
+internal sealed class MemoryWorkerLogger : IWorkerLogger
+{
+    public List<MemoryWorkerLogEntry> Entries { get; } = new();
+
+    public void Information(string eventName, IReadOnlyDictionary<string, object?> fields)
+    {
+        Entries.Add(new MemoryWorkerLogEntry("Information", eventName, WorkerLogRedactor.RedactFields(fields)));
+    }
+
+    public void Error(string eventName, IReadOnlyDictionary<string, object?> fields)
+    {
+        Entries.Add(new MemoryWorkerLogEntry("Error", eventName, WorkerLogRedactor.RedactFields(fields)));
+    }
+}

src/MxGateway.Worker.Tests/Bootstrap/WorkerApplicationTests.cs

@@ -0,0 +1,113 @@
+using System;
+using MxGateway.Contracts;
+using MxGateway.Worker.Bootstrap;
+
+namespace MxGateway.Worker.Tests.Bootstrap;
+
+public sealed class WorkerApplicationTests
+{
+    [Fact]
+    public void Run_WithValidBootstrapArguments_ReturnsSuccessAndLogsRedactedNonce()
+    {
+        MemoryWorkerEnvironment environment = CreateEnvironment("nonce-secret");
+        MemoryWorkerLogger logger = new();
+
+        int exitCode = MxGateway.Worker.WorkerApplication.Run(
+            ValidArgs(),
+            environment,
+            logger);
+
+        Assert.Equal((int)WorkerExitCode.Success, exitCode);
+        MemoryWorkerLogEntry entry = Assert.Single(logger.Entries);
+        Assert.Equal("Information", entry.Level);
+        Assert.Equal("WorkerBootstrapSucceeded", entry.EventName);
+        Assert.Equal("session-1", entry.Fields["session_id"]);
+        Assert.Equal("mxaccess-gateway-123-session-1", entry.Fields["pipe_name"]);
+        Assert.Equal(GatewayContractInfo.WorkerProtocolVersion, entry.Fields["protocol_version"]);
+        Assert.Equal("[redacted]", entry.Fields["nonce"]);
+    }
+
+    [Fact]
+    public void Run_WithMissingRequiredArguments_ReturnsInvalidArguments()
+    {
+        MemoryWorkerEnvironment environment = CreateEnvironment("nonce-secret");
+        MemoryWorkerLogger logger = new();
+
+        int exitCode = MxGateway.Worker.WorkerApplication.Run(
+            [],
+            environment,
+            logger);
+
+        Assert.Equal((int)WorkerExitCode.InvalidArguments, exitCode);
+        MemoryWorkerLogEntry entry = Assert.Single(logger.Entries);
+        Assert.Equal("Error", entry.Level);
+        Assert.Equal("WorkerBootstrapFailed", entry.EventName);
+        Assert.Equal(WorkerExitCode.InvalidArguments, entry.Fields["exit_code"]);
+    }
+
+    [Fact]
+    public void Run_WithInvalidProtocolVersion_ReturnsInvalidProtocolVersion()
+    {
+        MemoryWorkerEnvironment environment = CreateEnvironment("nonce-secret");
+        MemoryWorkerLogger logger = new();
+
+        int exitCode = MxGateway.Worker.WorkerApplication.Run(
+            ValidArgs(protocolVersion: "999"),
+            environment,
+            logger);
+
+        Assert.Equal((int)WorkerExitCode.InvalidProtocolVersion, exitCode);
+    }
+
+    [Fact]
+    public void Run_WithMissingNonce_ReturnsMissingNonce()
+    {
+        MemoryWorkerEnvironment environment = new();
+        MemoryWorkerLogger logger = new();
+
+        int exitCode = MxGateway.Worker.WorkerApplication.Run(
+            ValidArgs(),
+            environment,
+            logger);
+
+        Assert.Equal((int)WorkerExitCode.MissingNonce, exitCode);
+    }
+
+    [Fact]
+    public void Run_WithUnexpectedBootstrapFailure_ReturnsUnexpectedFailure()
+    {
+        MemoryWorkerEnvironment environment = new(new InvalidOperationException("environment failed"));
+        MemoryWorkerLogger logger = new();
+
+        int exitCode = MxGateway.Worker.WorkerApplication.Run(
+            ValidArgs(),
+            environment,
+            logger);
+
+        Assert.Equal((int)WorkerExitCode.UnexpectedFailure, exitCode);
+        MemoryWorkerLogEntry entry = Assert.Single(logger.Entries);
+        Assert.Equal("WorkerBootstrapUnexpectedFailure", entry.EventName);
+        Assert.Equal(WorkerExitCode.UnexpectedFailure, entry.Fields["exit_code"]);
+        Assert.Equal(typeof(InvalidOperationException).FullName, entry.Fields["exception_type"]);
+    }
+
+    private static string[] ValidArgs(string? protocolVersion = null)
+    {
+        return
+        [
+            "--session-id",
+            "session-1",
+            "--pipe-name",
+            "mxaccess-gateway-123-session-1",
+            "--protocol-version",
+            protocolVersion ?? GatewayContractInfo.WorkerProtocolVersion.ToString(),
+        ];
+    }
+
+    private static MemoryWorkerEnvironment CreateEnvironment(string nonce)
+    {
+        MemoryWorkerEnvironment environment = new();
+        environment.Set(WorkerOptions.NonceEnvironmentVariableName, nonce);
+        return environment;
+    }
+}

src/MxGateway.Worker.Tests/Bootstrap/WorkerConsoleLoggerTests.cs

@@ -0,0 +1,28 @@
+using System.Collections.Generic;
+using System.IO;
+using MxGateway.Worker.Bootstrap;
+
+namespace MxGateway.Worker.Tests.Bootstrap;
+
+public sealed class WorkerConsoleLoggerTests
+{
+    [Fact]
+    public void Information_RedactsNonceInStructuredOutput()
+    {
+        StringWriter writer = new();
+        WorkerConsoleLogger logger = new(writer);
+
+        logger.Information("WorkerBootstrapSucceeded", new Dictionary<string, object?>
+        {
+            ["session_id"] = "session-1",
+            ["nonce"] = "nonce-secret",
+        });
+
+        string output = writer.ToString();
+
+        Assert.Contains("event=WorkerBootstrapSucceeded", output);
+        Assert.Contains("session_id=session-1", output);
+        Assert.Contains("nonce=[redacted]", output);
+        Assert.DoesNotContain("nonce-secret", output);
+    }
+}

src/MxGateway.Worker.Tests/Bootstrap/WorkerLogRedactorTests.cs

@@ -0,0 +1,32 @@
+using System.Collections.Generic;
+using MxGateway.Worker.Bootstrap;
+
+namespace MxGateway.Worker.Tests.Bootstrap;
+
+public sealed class WorkerLogRedactorTests
+{
+    [Fact]
+    public void RedactFields_RedactsNonceSecretPasswordTokenCredentialAndApiKeyFields()
+    {
+        Dictionary<string, object?> fields = new()
+        {
+            ["nonce"] = "nonce-secret",
+            ["client_secret"] = "secret",
+            ["password"] = "password",
+            ["auth_token"] = "token",
+            ["credential_value"] = "credential",
+            ["api_key"] = "key",
+            ["session_id"] = "session-1",
+        };
+
+        Dictionary<string, object?> redacted = WorkerLogRedactor.RedactFields(fields);
+
+        Assert.Equal("[redacted]", redacted["nonce"]);
+        Assert.Equal("[redacted]", redacted["client_secret"]);
+        Assert.Equal("[redacted]", redacted["password"]);
+        Assert.Equal("[redacted]", redacted["auth_token"]);
+        Assert.Equal("[redacted]", redacted["credential_value"]);
+        Assert.Equal("[redacted]", redacted["api_key"]);
+        Assert.Equal("session-1", redacted["session_id"]);
+    }
+}

src/MxGateway.Worker.Tests/Bootstrap/WorkerOptionsParserTests.cs

@@ -0,0 +1,115 @@
+using MxGateway.Contracts;
+using MxGateway.Worker.Bootstrap;
+
+namespace MxGateway.Worker.Tests.Bootstrap;
+
+public sealed class WorkerOptionsParserTests
+{
+    [Fact]
+    public void Parse_WithAllRequiredInputs_ReturnsWorkerOptions()
+    {
+        WorkerOptionsParser parser = new(CreateEnvironment("nonce-secret"));
+
+        WorkerBootstrapResult result = parser.Parse(ValidArgs());
+
+        Assert.True(result.Succeeded);
+        Assert.Equal(WorkerExitCode.Success, result.ExitCode);
+        Assert.NotNull(result.Options);
+        Assert.Equal("session-1", result.Options.SessionId);
+        Assert.Equal("mxaccess-gateway-123-session-1", result.Options.PipeName);
+        Assert.Equal(GatewayContractInfo.WorkerProtocolVersion, result.Options.ProtocolVersion);
+        Assert.Equal("nonce-secret", result.Options.Nonce);
+    }
+
+    [Fact]
+    public void Parse_WithMissingSessionId_ReturnsInvalidArguments()
+    {
+        WorkerOptionsParser parser = new(CreateEnvironment("nonce-secret"));
+
+        WorkerBootstrapResult result = parser.Parse(
+        [
+            "--pipe-name",
+            "mxaccess-gateway-123-session-1",
+            "--protocol-version",
+            GatewayContractInfo.WorkerProtocolVersion.ToString(),
+        ]);
+
+        Assert.False(result.Succeeded);
+        Assert.Equal(WorkerExitCode.InvalidArguments, result.ExitCode);
+        Assert.Contains(result.Errors, error => error.Contains("--session-id"));
+    }
+
+    [Fact]
+    public void Parse_WithUnknownOption_ReturnsInvalidArguments()
+    {
+        WorkerOptionsParser parser = new(CreateEnvironment("nonce-secret"));
+
+        WorkerBootstrapResult result = parser.Parse(
+        [
+            "--session-id",
+            "session-1",
+            "--pipe-name",
+            "mxaccess-gateway-123-session-1",
+            "--protocol-version",
+            GatewayContractInfo.WorkerProtocolVersion.ToString(),
+            "--unexpected",
+            "value",
+        ]);
+
+        Assert.Equal(WorkerExitCode.InvalidArguments, result.ExitCode);
+        Assert.Contains(result.Errors, error => error.Contains("Unknown option"));
+    }
+
+    [Fact]
+    public void Parse_WithNonNumericProtocolVersion_ReturnsInvalidProtocolVersion()
+    {
+        WorkerOptionsParser parser = new(CreateEnvironment("nonce-secret"));
+
+        WorkerBootstrapResult result = parser.Parse(ValidArgs(protocolVersion: "abc"));
+
+        Assert.False(result.Succeeded);
+        Assert.Equal(WorkerExitCode.InvalidProtocolVersion, result.ExitCode);
+    }
+
+    [Fact]
+    public void Parse_WithUnsupportedProtocolVersion_ReturnsInvalidProtocolVersion()
+    {
+        WorkerOptionsParser parser = new(CreateEnvironment("nonce-secret"));
+
+        WorkerBootstrapResult result = parser.Parse(ValidArgs(protocolVersion: "999"));
+
+        Assert.False(result.Succeeded);
+        Assert.Equal(WorkerExitCode.InvalidProtocolVersion, result.ExitCode);
+    }
+
+    [Fact]
+    public void Parse_WithMissingNonce_ReturnsMissingNonce()
+    {
+        WorkerOptionsParser parser = new(new MemoryWorkerEnvironment());
+
+        WorkerBootstrapResult result = parser.Parse(ValidArgs());
+
+        Assert.False(result.Succeeded);
+        Assert.Equal(WorkerExitCode.MissingNonce, result.ExitCode);
+    }
+
+    private static string[] ValidArgs(string? protocolVersion = null)
+    {
+        return
+        [
+            "--session-id",
+            "session-1",
+            "--pipe-name",
+            "mxaccess-gateway-123-session-1",
+            "--protocol-version",
+            protocolVersion ?? GatewayContractInfo.WorkerProtocolVersion.ToString(),
+        ];
+    }
+
+    private static MemoryWorkerEnvironment CreateEnvironment(string nonce)
+    {
+        MemoryWorkerEnvironment environment = new();
+        environment.Set(WorkerOptions.NonceEnvironmentVariableName, nonce);
+        return environment;
+    }
+}

src/MxGateway.Worker.Tests/Contracts/WorkerContractInfoTests.cs

@@ -0,0 +1,19 @@
+using MxGateway.Contracts;
+using MxGateway.Worker.Ipc;
+
+namespace MxGateway.Worker.Tests.Contracts;
+
+public sealed class WorkerContractInfoTests
+{
+    [Fact]
+    public void SupportedProtocolVersion_UsesSharedGatewayContractVersion()
+    {
+        Assert.Equal(GatewayContractInfo.WorkerProtocolVersion, WorkerContractInfo.SupportedProtocolVersion);
+    }
+
+    [Fact]
+    public void WorkerEnvelopeDescriptorName_UsesGeneratedWorkerContract()
+    {
+        Assert.Equal("mxaccess_worker.v1.WorkerEnvelope", WorkerContractInfo.WorkerEnvelopeDescriptorName);
+    }
+}

src/MxGateway.Worker.Tests/MxAccess/MxAccessInteropInfoTests.cs

@@ -0,0 +1,23 @@
+using MxGateway.Worker.MxAccess;
+
+namespace MxGateway.Worker.Tests.MxAccess;
+
+public sealed class MxAccessInteropInfoTests
+{
+    [Fact]
+    public void InteropInfo_IdentifiesInstalledMxAccessComTarget()
+    {
+        Assert.Equal("LMXProxy.LMXProxyServer.1", MxAccessInteropInfo.ProgId);
+        Assert.Equal("LMXProxy.LMXProxyServer", MxAccessInteropInfo.VersionIndependentProgId);
+        Assert.Equal("{C30B52F5-2CB5-4760-AF0A-3A344A7EB5DC}", MxAccessInteropInfo.Clsid);
+        Assert.Equal("ArchestrA.MxAccess.LMXProxyServerClass", MxAccessInteropInfo.ComClassName);
+    }
+
+    [Fact]
+    public void InteropAssemblyName_ComesFromReferencedMxAccessAssembly()
+    {
+        Assert.Equal("ArchestrA.MxAccess", MxAccessInteropInfo.InteropAssemblyName);
+        Assert.Equal(3, MxAccessInteropInfo.InteropAssemblyVersion.Major);
+        Assert.Equal(2, MxAccessInteropInfo.InteropAssemblyVersion.Minor);
+    }
+}

src/MxGateway.Worker.Tests/MxGateway.Worker.Tests.csproj

@@ -0,0 +1,28 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net48</TargetFramework>
+    <IsPackable>false</IsPackable>
+    <PlatformTarget>x86</PlatformTarget>
+    <Prefer32Bit>true</Prefer32Bit>
+    <ImplicitUsings>disable</ImplicitUsings>
+    <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
+    <GenerateBindingRedirectsOutputType>true</GenerateBindingRedirectsOutputType>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+    <PackageReference Include="System.Runtime.CompilerServices.Unsafe" Version="6.1.2" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.1.4" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\MxGateway.Worker\MxGateway.Worker.csproj" />
+  </ItemGroup>
+
+</Project>

src/MxGateway.Worker.Tests/ProjectStructure/WorkerProjectReferenceTests.cs

@@ -0,0 +1,94 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Xml.Linq;
+
+namespace MxGateway.Worker.Tests.ProjectStructure;
+
+public sealed class WorkerProjectReferenceTests
+{
+    [Fact]
+    public void WorkerProject_TargetsNet48AndX86()
+    {
+        XDocument project = LoadProject("MxGateway.Worker");
+
+        Assert.Equal("net48", ElementValue(project, "TargetFramework"));
+        Assert.Equal("x86", ElementValue(project, "PlatformTarget"));
+        Assert.Equal("true", ElementValue(project, "Prefer32Bit"));
+    }
+
+    [Fact]
+    public void WorkerTestProject_TargetsNet48AndX86()
+    {
+        XDocument project = LoadProject("MxGateway.Worker.Tests");
+
+        Assert.Equal("net48", ElementValue(project, "TargetFramework"));
+        Assert.Equal("x86", ElementValue(project, "PlatformTarget"));
+    }
+
+    [Fact]
+    public void MxAccessInteropReference_ExistsOnlyInWorkerProject()
+    {
+        DirectoryInfo repositoryRoot = FindRepositoryRoot();
+        string[] projectFiles = Directory.GetFiles(repositoryRoot.FullName, "*.csproj", SearchOption.AllDirectories)
+            .Where(path => path.IndexOf($"{Path.DirectorySeparatorChar}bin{Path.DirectorySeparatorChar}", StringComparison.OrdinalIgnoreCase) < 0)
+            .Where(path => path.IndexOf($"{Path.DirectorySeparatorChar}obj{Path.DirectorySeparatorChar}", StringComparison.OrdinalIgnoreCase) < 0)
+            .ToArray();
+
+        IReadOnlyList<string> projectsWithMxAccessReference = projectFiles
+            .Where(ProjectReferencesMxAccess)
+            .Select(path => Path.GetFileNameWithoutExtension(path))
+            .ToArray();
+
+        Assert.Equal(["MxGateway.Worker"], projectsWithMxAccessReference);
+    }
+
+    private static bool ProjectReferencesMxAccess(string projectPath)
+    {
+        XDocument project = XDocument.Load(projectPath);
+
+        return project
+            .Descendants()
+            .Where(element => element.Name.LocalName is "Reference" or "COMReference" or "COMFileReference" or "PackageReference")
+            .Select(element => (string?)element.Attribute("Include") ?? string.Empty)
+            .Concat(project.Descendants().Where(element => element.Name.LocalName == "HintPath").Select(element => element.Value))
+            .Any(reference =>
+                reference.IndexOf("MxAccess", StringComparison.OrdinalIgnoreCase) >= 0
+                || reference.IndexOf("ArchestrA.MXAccess", StringComparison.OrdinalIgnoreCase) >= 0
+                || reference.IndexOf("LMXProxy", StringComparison.OrdinalIgnoreCase) >= 0);
+    }
+
+    private static XDocument LoadProject(string projectName)
+    {
+        DirectoryInfo repositoryRoot = FindRepositoryRoot();
+        string projectPath = Path.Combine(repositoryRoot.FullName, projectName, $"{projectName}.csproj");
+
+        return XDocument.Load(projectPath);
+    }
+
+    private static string ElementValue(XDocument project, string elementName)
+    {
+        return project
+            .Descendants()
+            .Single(element => element.Name.LocalName == elementName)
+            .Value;
+    }
+
+    private static DirectoryInfo FindRepositoryRoot()
+    {
+        DirectoryInfo? current = new(AppContext.BaseDirectory);
+
+        while (current is not null)
+        {
+            if (File.Exists(Path.Combine(current.FullName, "MxGateway.sln")))
+            {
+                return current;
+            }
+
+            current = current.Parent;
+        }
+
+        throw new DirectoryNotFoundException("Could not locate src/MxGateway.sln from the test output directory.");
+    }
+}

src/MxGateway.Worker/Bootstrap/EnvironmentVariableWorkerEnvironment.cs

@@ -0,0 +1,11 @@
+using System;
+
+namespace MxGateway.Worker.Bootstrap;
+
+public sealed class EnvironmentVariableWorkerEnvironment : IWorkerEnvironment
+{
+    public string? GetEnvironmentVariable(string name)
+    {
+        return Environment.GetEnvironmentVariable(name);
+    }
+}

src/MxGateway.Worker/Bootstrap/IWorkerEnvironment.cs

@@ -0,0 +1,6 @@
+namespace MxGateway.Worker.Bootstrap;
+
+public interface IWorkerEnvironment
+{
+    string? GetEnvironmentVariable(string name);
+}

src/MxGateway.Worker/Bootstrap/IWorkerLogger.cs

@@ -0,0 +1,10 @@
+using System.Collections.Generic;
+
+namespace MxGateway.Worker.Bootstrap;
+
+public interface IWorkerLogger
+{
+    void Information(string eventName, IReadOnlyDictionary<string, object?> fields);
+
+    void Error(string eventName, IReadOnlyDictionary<string, object?> fields);
+}