docs: add mqtt connection type implementation plan and task tracking

2026-02-23 08:49:24 -05:00
parent 71f7f569b9
commit 6228f748ab
3 changed files with 2590 additions and 0 deletions
--- a/docs/plans/2026-02-23-jetstream-full-parity-plan.md
+++ b/docs/plans/2026-02-23-jetstream-full-parity-plan.md
--- a/docs/plans/2026-02-23-mqtt-connection-type-plan.md
+++ b/docs/plans/2026-02-23-mqtt-connection-type-plan.md
@@ -0,0 +1,933 @@
+# MQTT Connection Type Parity + Config Parsing Implementation Plan
+
+> **For Claude:** REQUIRED SUB-SKILL: Use superpowers-extended-cc:executing-plans to implement this plan task-by-task.
+
+**Goal:** Port Go-compatible MQTT connection-type handling for JWT `allowed_connection_types`, add `/connz` `mqtt_client` filtering, parse all Go `MQTTOpts` config fields, and expand `MqttOptsVarz` monitoring output — with tests and docs updates.
+
+**Architecture:** Thread a connection-type value into auth context and enforce Go-style allowed-connection-type semantics in `JwtAuthenticator`. Add connz query-option filtering for `mqtt_client` across open and closed connections. Parse the full `mqtt {}` config block into a new `MqttOptions` model following the existing `ParseTls()` pattern in `ConfigProcessor`. Expand `MqttOptsVarz` and wire into `/varz`. Keep behavior backward-compatible and transport-agnostic so MQTT runtime plumbing can be added later without changing auth/monitoring/config semantics.
+
+**Tech Stack:** .NET 10, xUnit 3, Shouldly, ASP.NET minimal APIs, System.Text.Json.
+
+---
+
+### Task 1: Add failing JWT connection-type behavior tests
+
+**Files:**
+- Modify: `tests/NATS.Server.Tests/JwtAuthenticatorTests.cs`
+
+**Step 1: Write the failing tests**
+
+Add these 5 test methods to the existing `JwtAuthenticatorTests` class. Each test must build a valid operator/account/user JWT chain (reuse the existing helper pattern from other tests in the file). The user JWT's `nats.allowed_connection_types` array controls which connection types are permitted.
+
+```csharp
+[Fact]
+public async Task Allowed_connection_types_allows_standard_context()
+{
+    // Build valid operator/account/user JWT chain.
+    // User JWT includes: "allowed_connection_types":["STANDARD"]
+    // Context sets ConnectionType = "STANDARD".
+    // Assert Authenticate() is not null.
+}
+
+[Fact]
+public async Task Allowed_connection_types_rejects_mqtt_only_for_standard_context()
+{
+    // User JWT includes: "allowed_connection_types":["MQTT"]
+    // Context sets ConnectionType = "STANDARD".
+    // Assert Authenticate() is null.
+}
+
+[Fact]
+public async Task Allowed_connection_types_allows_known_even_with_unknown_values()
+{
+    // User JWT includes: ["STANDARD", "SOME_NEW_TYPE"]
+    // Context sets ConnectionType = "STANDARD".
+    // Assert Authenticate() is not null.
+}
+
+[Fact]
+public async Task Allowed_connection_types_rejects_when_only_unknown_values_present()
+{
+    // User JWT includes: ["SOME_NEW_TYPE"]
+    // Context sets ConnectionType = "STANDARD".
+    // Assert Authenticate() is null.
+}
+
+[Fact]
+public async Task Allowed_connection_types_is_case_insensitive_for_input_values()
+{
+    // User JWT includes: ["standard"]
+    // Context sets ConnectionType = "STANDARD".
+    // Assert Authenticate() is not null.
+}
+```
+
+**Step 2: Run test to verify it fails**
+
+Run: `dotnet test tests/NATS.Server.Tests/NATS.Server.Tests.csproj --filter "FullyQualifiedName~JwtAuthenticatorTests.Allowed_connection_types" -v minimal`
+Expected: FAIL (current implementation ignores `allowed_connection_types`).
+
+**Step 3: Commit test-only checkpoint**
+
+```bash
+git add tests/NATS.Server.Tests/JwtAuthenticatorTests.cs
+git commit -m "test: add failing jwt allowed connection type coverage"
+```
+
+---
+
+### Task 2: Implement auth connection-type model and Go-style allowed-type conversion
+
+**Files:**
+- Modify: `src/NATS.Server/Auth/IAuthenticator.cs` (line 11-16: add `ConnectionType` property to `ClientAuthContext`)
+- Create: `src/NATS.Server/Auth/Jwt/JwtConnectionTypes.cs`
+- Modify: `src/NATS.Server/Auth/JwtAuthenticator.cs` (insert check after step 7 revocation check, before step 8 permissions, around line 97)
+- Modify: `src/NATS.Server/NatsClient.cs` (line 382-387: add `ConnectionType` to auth context construction)
+
+**Step 1: Add connection type to auth context**
+
+In `src/NATS.Server/Auth/IAuthenticator.cs`, add the `ConnectionType` property to `ClientAuthContext`. Note: this requires adding a `using NATS.Server.Auth.Jwt;` at the top of the file.
+
+```csharp
+public sealed class ClientAuthContext
+{
+    public required ClientOptions Opts { get; init; }
+    public required byte[] Nonce { get; init; }
+    public string ConnectionType { get; init; } = JwtConnectionTypes.Standard;
+    public X509Certificate2? ClientCertificate { get; init; }
+}
+```
+
+**Step 2: Create JWT connection-type constants + converter helper**
+
+Create new file `src/NATS.Server/Auth/Jwt/JwtConnectionTypes.cs`:
+
+```csharp
+namespace NATS.Server.Auth.Jwt;
+
+/// <summary>
+/// Known connection type constants matching Go server/client.go.
+/// Used for JWT allowed_connection_types claim validation.
+/// Reference: golang/nats-server/server/client.go connectionType constants.
+/// </summary>
+internal static class JwtConnectionTypes
+{
+    public const string Standard = "STANDARD";
+    public const string Websocket = "WEBSOCKET";
+    public const string Leafnode = "LEAFNODE";
+    public const string LeafnodeWs = "LEAFNODE_WS";
+    public const string Mqtt = "MQTT";
+    public const string MqttWs = "MQTT_WS";
+    public const string InProcess = "INPROCESS";
+
+    private static readonly HashSet<string> Known =
+    [
+        Standard, Websocket, Leafnode, LeafnodeWs, Mqtt, MqttWs, InProcess,
+    ];
+
+    /// <summary>
+    /// Converts a list of connection type strings (from JWT claims) into a set of
+    /// known valid types plus a flag indicating unknown values were present.
+    /// Reference: Go server/client.go convertAllowedConnectionTypes.
+    /// </summary>
+    public static (HashSet<string> Valid, bool HasUnknown) Convert(IEnumerable<string>? values)
+    {
+        var valid = new HashSet<string>(StringComparer.Ordinal);
+        var hasUnknown = false;
+        if (values is null) return (valid, false);
+
+        foreach (var raw in values)
+        {
+            var up = (raw ?? string.Empty).Trim().ToUpperInvariant();
+            if (up.Length == 0) continue;
+            if (Known.Contains(up)) valid.Add(up);
+            else hasUnknown = true;
+        }
+
+        return (valid, hasUnknown);
+    }
+}
+```
+
+**Step 3: Enforce allowed connection types in JWT auth**
+
+In `src/NATS.Server/Auth/JwtAuthenticator.cs`, insert the following block after the revocation check (step 7, around line 96) and before the permissions build (step 8):
+
+```csharp
+// 7b. Check allowed connection types
+var (allowedTypes, hasUnknown) = JwtConnectionTypes.Convert(userClaims.Nats?.AllowedConnectionTypes);
+
+if (allowedTypes.Count == 0)
+{
+    if (hasUnknown)
+        return null; // unknown-only list should reject
+}
+else
+{
+    var connType = string.IsNullOrWhiteSpace(context.ConnectionType)
+        ? JwtConnectionTypes.Standard
+        : context.ConnectionType.ToUpperInvariant();
+
+    if (!allowedTypes.Contains(connType))
+        return null;
+}
+```
+
+**Step 4: Set auth context connection type in client connect path**
+
+In `src/NATS.Server/NatsClient.cs` around line 382, add `ConnectionType` to the existing `ClientAuthContext` construction:
+
+```csharp
+var context = new ClientAuthContext
+{
+    Opts = ClientOpts,
+    Nonce = _nonce ?? [],
+    ConnectionType = JwtConnectionTypes.Standard,
+    ClientCertificate = TlsState?.PeerCert,
+};
+```
+
+Add `using NATS.Server.Auth.Jwt;` at the top of the file.
+
+**Step 5: Run tests to verify pass**
+
+Run: `dotnet test tests/NATS.Server.Tests/NATS.Server.Tests.csproj --filter "FullyQualifiedName~JwtAuthenticatorTests.Allowed_connection_types" -v minimal`
+Expected: PASS.
+
+**Step 6: Commit implementation checkpoint**
+
+```bash
+git add src/NATS.Server/Auth/IAuthenticator.cs src/NATS.Server/Auth/Jwt/JwtConnectionTypes.cs src/NATS.Server/Auth/JwtAuthenticator.cs src/NATS.Server/NatsClient.cs
+git commit -m "feat: enforce jwt allowed connection types with go-compatible semantics"
+```
+
+---
+
+### Task 3: Add failing connz mqtt_client filter tests
+
+**Files:**
+- Modify: `tests/NATS.Server.Tests/MonitorTests.cs`
+
+**Step 1: Write the failing tests**
+
+Add these 2 test methods to the existing `MonitorTests` class. These test the `/connz?mqtt_client=<id>` query parameter filtering.
+
+```csharp
+[Fact]
+public async Task Connz_filters_by_mqtt_client_for_open_connections()
+{
+    // Start server with monitoring port.
+    // Connect a regular NATS client (no MQTT ID).
+    // Query /connz?mqtt_client=some-id.
+    // Assert num_connections == 0 (no client has that MQTT ID).
+}
+
+[Fact]
+public async Task Connz_filters_by_mqtt_client_for_closed_connections()
+{
+    // Start server with monitoring port.
+    // Query /connz?state=closed&mqtt_client=missing-id.
+    // Assert num_connections == 0.
+}
+```
+
+**Step 2: Run tests to verify expected failure mode**
+
+Run: `dotnet test tests/NATS.Server.Tests/NATS.Server.Tests.csproj --filter "FullyQualifiedName~MonitorTests.Connz_filters_by_mqtt_client" -v minimal`
+Expected: FAIL (query option not implemented yet — `mqtt_client` param ignored, so all connections returned).
+
+**Step 3: Commit test-only checkpoint**
+
+```bash
+git add tests/NATS.Server.Tests/MonitorTests.cs
+git commit -m "test: add failing connz mqtt_client filter coverage"
+```
+
+---
+
+### Task 4: Implement connz mqtt_client filtering and closed snapshot support
+
+**Files:**
+- Modify: `src/NATS.Server/Monitoring/Connz.cs` (line 191-210: add `MqttClient` to `ConnzOptions`)
+- Modify: `src/NATS.Server/Monitoring/ConnzHandler.cs` (line 148-201: parse query param; line 18-29: apply filter after collection but before sort)
+- Modify: `src/NATS.Server/Monitoring/ClosedClient.cs` (line 6-25: add `MqttClient` property)
+- Modify: `src/NATS.Server/NatsServer.cs` (line 695-714: add `MqttClient` to closed snapshot)
+
+**Step 1: Add `MqttClient` to `ConnzOptions`**
+
+In `src/NATS.Server/Monitoring/Connz.cs`, add after `FilterSubject` property (line 205):
+
+```csharp
+public string MqttClient { get; set; } = "";
+```
+
+**Step 2: Parse `mqtt_client` query param in handler**
+
+In `src/NATS.Server/Monitoring/ConnzHandler.cs` `ParseQueryParams` method, add after the existing `limit` parse block (around line 198):
+
+```csharp
+if (q.TryGetValue("mqtt_client", out var mqttClient))
+    opts.MqttClient = mqttClient.ToString();
+```
+
+**Step 3: Apply `mqtt_client` filter in `HandleConnz`**
+
+In `src/NATS.Server/Monitoring/ConnzHandler.cs` `HandleConnz` method, add after the closed connections collection block (after line 29) and before the sort validation (line 32):
+
+```csharp
+// Filter by MQTT client ID
+if (!string.IsNullOrEmpty(opts.MqttClient))
+    connInfos = connInfos.Where(c => c.MqttClient == opts.MqttClient).ToList();
+```
+
+**Step 4: Add `MqttClient` to `ClosedClient` model**
+
+In `src/NATS.Server/Monitoring/ClosedClient.cs`, add after line 24 (`TlsCipherSuite`):
+
+```csharp
+public string MqttClient { get; init; } = "";
+```
+
+**Step 5: Add `MqttClient` to closed snapshot creation in `NatsServer.RemoveClient`**
+
+In `src/NATS.Server/NatsServer.cs` around line 713 (inside the `new ClosedClient { ... }` block), add:
+
+```csharp
+MqttClient = "", // populated when MQTT transport is implemented
+```
+
+**Step 6: Add `MqttClient` to `BuildClosedConnInfo`**
+
+In `src/NATS.Server/Monitoring/ConnzHandler.cs` `BuildClosedConnInfo` method (line 119-146), add to the `new ConnInfo { ... }` initializer:
+
+```csharp
+MqttClient = closed.MqttClient,
+```
+
+**Step 7: Run connz mqtt filter tests**
+
+Run: `dotnet test tests/NATS.Server.Tests/NATS.Server.Tests.csproj --filter "FullyQualifiedName~MonitorTests.Connz_filters_by_mqtt_client" -v minimal`
+Expected: PASS.
+
+**Step 8: Commit implementation checkpoint**
+
+```bash
+git add src/NATS.Server/Monitoring/Connz.cs src/NATS.Server/Monitoring/ConnzHandler.cs src/NATS.Server/Monitoring/ClosedClient.cs src/NATS.Server/NatsServer.cs
+git commit -m "feat: add connz mqtt_client filtering"
+```
+
+---
+
+### Task 5: Verification checkpoint for JWT + connz tasks
+
+**Step 1: Run all JWT connection-type tests**
+
+Run: `dotnet test tests/NATS.Server.Tests/NATS.Server.Tests.csproj --filter "FullyQualifiedName~JwtAuthenticatorTests.Allowed_connection_types" -v minimal`
+Expected: PASS.
+
+**Step 2: Run all connz tests**
+
+Run: `dotnet test tests/NATS.Server.Tests/NATS.Server.Tests.csproj --filter "FullyQualifiedName~MonitorTests.Connz" -v minimal`
+Expected: PASS.
+
+**Step 3: Run full test suite**
+
+Run: `dotnet test tests/NATS.Server.Tests/NATS.Server.Tests.csproj -v minimal`
+Expected: PASS (no regressions).
+
+---
+
+### Task 6: Add MqttOptions model and config parsing
+
+**Files:**
+- Create: `src/NATS.Server/MqttOptions.cs`
+- Modify: `src/NATS.Server/NatsOptions.cs` (line 116-117: add `Mqtt` property)
+- Modify: `src/NATS.Server/Configuration/ConfigProcessor.cs` (line 248: add `mqtt` case; add `ParseMqtt` + `ParseMqttAuth` + `ParseMqttTls` + `ToDouble` methods)
+
+**Step 1: Create `MqttOptions` model**
+
+Create new file `src/NATS.Server/MqttOptions.cs`. This matches Go `MQTTOpts` struct (golang/nats-server/server/opts.go:613-707):
+
+```csharp
+namespace NATS.Server;
+
+/// <summary>
+/// MQTT protocol configuration options.
+/// Corresponds to Go server/opts.go MQTTOpts struct.
+/// Config is parsed and stored but no MQTT listener is started yet.
+/// </summary>
+public sealed class MqttOptions
+{
+    // Network
+    public string Host { get; set; } = "";
+    public int Port { get; set; }
+
+    // Auth override (MQTT-specific, separate from global auth)
+    public string? NoAuthUser { get; set; }
+    public string? Username { get; set; }
+    public string? Password { get; set; }
+    public string? Token { get; set; }
+    public double AuthTimeout { get; set; }
+
+    // TLS
+    public string? TlsCert { get; set; }
+    public string? TlsKey { get; set; }
+    public string? TlsCaCert { get; set; }
+    public bool TlsVerify { get; set; }
+    public double TlsTimeout { get; set; } = 2.0;
+    public bool TlsMap { get; set; }
+    public HashSet<string>? TlsPinnedCerts { get; set; }
+
+    // JetStream integration
+    public string? JsDomain { get; set; }
+    public int StreamReplicas { get; set; }
+    public int ConsumerReplicas { get; set; }
+    public bool ConsumerMemoryStorage { get; set; }
+    public TimeSpan ConsumerInactiveThreshold { get; set; }
+
+    // QoS
+    public TimeSpan AckWait { get; set; } = TimeSpan.FromSeconds(30);
+    public ushort MaxAckPending { get; set; }
+    public TimeSpan JsApiTimeout { get; set; } = TimeSpan.FromSeconds(5);
+
+    public bool HasTls => TlsCert != null && TlsKey != null;
+}
+```
+
+**Step 2: Add `Mqtt` property to `NatsOptions`**
+
+In `src/NATS.Server/NatsOptions.cs`, add before the `HasTls` property (around line 117):
+
+```csharp
+// MQTT configuration (parsed from config, no listener yet)
+public MqttOptions? Mqtt { get; set; }
+```
+
+**Step 3: Add `ToDouble` helper to `ConfigProcessor`**
+
+In `src/NATS.Server/Configuration/ConfigProcessor.cs`, add after the `ToString` helper (around line 654):
+
+```csharp
+private static double ToDouble(object? value) => value switch
+{
+    double d => d,
+    long l => l,
+    int i => i,
+    string s when double.TryParse(s, NumberStyles.Float, CultureInfo.InvariantCulture, out var d) => d,
+    _ => throw new FormatException($"Cannot convert {value?.GetType().Name ?? "null"} to double"),
+};
+```
+
+**Step 4: Add `mqtt` case to `ProcessKey` switch**
+
+In `src/NATS.Server/Configuration/ConfigProcessor.cs`, replace the default case comment at line 248:
+
+```csharp
+// MQTT
+case "mqtt":
+    if (value is Dictionary<string, object?> mqttDict)
+        ParseMqtt(mqttDict, opts, errors);
+    break;
+
+// Unknown keys silently ignored (cluster, jetstream, gateway, leafnode, etc.)
+default:
+    break;
+```
+
+**Step 5: Add `ParseMqtt` method**
+
+Add this method after `ParseTags` (around line 621). It follows the exact key/alias structure from Go `parseMQTT` (opts.go:5443-5541):
+
+```csharp
+// ─── MQTT parsing ─────────────────────────────────────────────
+
+private static void ParseMqtt(Dictionary<string, object?> dict, NatsOptions opts, List<string> errors)
+{
+    var mqtt = opts.Mqtt ?? new MqttOptions();
+
+    foreach (var (key, value) in dict)
+    {
+        switch (key.ToLowerInvariant())
+        {
+            case "listen":
+                var (host, port) = ParseHostPort(value);
+                if (host is not null) mqtt.Host = host;
+                if (port is not null) mqtt.Port = port.Value;
+                break;
+            case "port":
+                mqtt.Port = ToInt(value);
+                break;
+            case "host" or "net":
+                mqtt.Host = ToString(value);
+                break;
+            case "no_auth_user":
+                mqtt.NoAuthUser = ToString(value);
+                break;
+            case "tls":
+                if (value is Dictionary<string, object?> tlsDict)
+                    ParseMqttTls(tlsDict, mqtt, errors);
+                break;
+            case "authorization" or "authentication":
+                if (value is Dictionary<string, object?> authDict)
+                    ParseMqttAuth(authDict, mqtt, errors);
+                break;
+            case "ack_wait" or "ackwait":
+                mqtt.AckWait = ParseDuration(value);
+                break;
+            case "js_api_timeout" or "api_timeout":
+                mqtt.JsApiTimeout = ParseDuration(value);
+                break;
+            case "max_ack_pending" or "max_pending" or "max_inflight":
+                var pending = ToInt(value);
+                if (pending < 0 || pending > 0xFFFF)
+                    errors.Add($"mqtt max_ack_pending invalid value {pending}, should be in [0..{0xFFFF}] range");
+                else
+                    mqtt.MaxAckPending = (ushort)pending;
+                break;
+            case "js_domain":
+                mqtt.JsDomain = ToString(value);
+                break;
+            case "stream_replicas":
+                mqtt.StreamReplicas = ToInt(value);
+                break;
+            case "consumer_replicas":
+                mqtt.ConsumerReplicas = ToInt(value);
+                break;
+            case "consumer_memory_storage":
+                mqtt.ConsumerMemoryStorage = ToBool(value);
+                break;
+            case "consumer_inactive_threshold" or "consumer_auto_cleanup":
+                mqtt.ConsumerInactiveThreshold = ParseDuration(value);
+                break;
+            default:
+                // Unknown MQTT keys silently ignored
+                break;
+        }
+    }
+
+    opts.Mqtt = mqtt;
+}
+
+private static void ParseMqttAuth(Dictionary<string, object?> dict, MqttOptions mqtt, List<string> errors)
+{
+    foreach (var (key, value) in dict)
+    {
+        switch (key.ToLowerInvariant())
+        {
+            case "user" or "username":
+                mqtt.Username = ToString(value);
+                break;
+            case "pass" or "password":
+                mqtt.Password = ToString(value);
+                break;
+            case "token":
+                mqtt.Token = ToString(value);
+                break;
+            case "timeout":
+                mqtt.AuthTimeout = ToDouble(value);
+                break;
+            default:
+                break;
+        }
+    }
+}
+
+private static void ParseMqttTls(Dictionary<string, object?> dict, MqttOptions mqtt, List<string> errors)
+{
+    foreach (var (key, value) in dict)
+    {
+        switch (key.ToLowerInvariant())
+        {
+            case "cert_file":
+                mqtt.TlsCert = ToString(value);
+                break;
+            case "key_file":
+                mqtt.TlsKey = ToString(value);
+                break;
+            case "ca_file":
+                mqtt.TlsCaCert = ToString(value);
+                break;
+            case "verify":
+                mqtt.TlsVerify = ToBool(value);
+                break;
+            case "verify_and_map":
+                var map = ToBool(value);
+                mqtt.TlsMap = map;
+                if (map) mqtt.TlsVerify = true;
+                break;
+            case "timeout":
+                mqtt.TlsTimeout = ToDouble(value);
+                break;
+            case "pinned_certs":
+                if (value is List<object?> pinnedList)
+                {
+                    var certs = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+                    foreach (var item in pinnedList)
+                    {
+                        if (item is string s)
+                            certs.Add(s.ToLowerInvariant());
+                    }
+                    mqtt.TlsPinnedCerts = certs;
+                }
+                break;
+            default:
+                break;
+        }
+    }
+}
+```
+
+**Step 6: Build to verify compilation**
+
+Run: `dotnet build`
+Expected: Build succeeded.
+
+**Step 7: Commit**
+
+```bash
+git add src/NATS.Server/MqttOptions.cs src/NATS.Server/NatsOptions.cs src/NATS.Server/Configuration/ConfigProcessor.cs
+git commit -m "feat: add mqtt config model and parser for all Go MQTTOpts fields"
+```
+
+---
+
+### Task 7: Add MQTT config parsing tests
+
+**Files:**
+- Create: `tests/NATS.Server.Tests/TestData/mqtt.conf`
+- Modify: `tests/NATS.Server.Tests/ConfigProcessorTests.cs`
+
+**Step 1: Create MQTT test config file**
+
+Create `tests/NATS.Server.Tests/TestData/mqtt.conf`:
+
+```
+mqtt {
+    listen: "10.0.0.1:1883"
+    no_auth_user: "mqtt_default"
+
+    authorization {
+        user: "mqtt_user"
+        pass: "mqtt_pass"
+        token: "mqtt_token"
+        timeout: 3.0
+    }
+
+    tls {
+        cert_file: "/path/to/mqtt-cert.pem"
+        key_file: "/path/to/mqtt-key.pem"
+        ca_file: "/path/to/mqtt-ca.pem"
+        verify: true
+        timeout: 5.0
+    }
+
+    ack_wait: "60s"
+    max_ack_pending: 2048
+    js_domain: "mqtt-domain"
+    js_api_timeout: "10s"
+    stream_replicas: 3
+    consumer_replicas: 1
+    consumer_memory_storage: true
+    consumer_inactive_threshold: "5m"
+}
+```
+
+Ensure this file is copied to output: check that `.csproj` has a wildcard for TestData, or add:
+```xml
+<ItemGroup>
+  <None Update="TestData\**" CopyToOutputDirectory="PreserveNewest" />
+</ItemGroup>
+```
+
+**Step 2: Add MQTT config tests**
+
+Add to `tests/NATS.Server.Tests/ConfigProcessorTests.cs`:
+
+```csharp
+// ─── MQTT config ────────────────────────────────────────────
+
+[Fact]
+public void MqttConf_ListenHostAndPort()
+{
+    var opts = ConfigProcessor.ProcessConfigFile(TestDataPath("mqtt.conf"));
+    opts.Mqtt.ShouldNotBeNull();
+    opts.Mqtt!.Host.ShouldBe("10.0.0.1");
+    opts.Mqtt.Port.ShouldBe(1883);
+}
+
+[Fact]
+public void MqttConf_NoAuthUser()
+{
+    var opts = ConfigProcessor.ProcessConfigFile(TestDataPath("mqtt.conf"));
+    opts.Mqtt.ShouldNotBeNull();
+    opts.Mqtt!.NoAuthUser.ShouldBe("mqtt_default");
+}
+
+[Fact]
+public void MqttConf_Authorization()
+{
+    var opts = ConfigProcessor.ProcessConfigFile(TestDataPath("mqtt.conf"));
+    opts.Mqtt.ShouldNotBeNull();
+    opts.Mqtt!.Username.ShouldBe("mqtt_user");
+    opts.Mqtt.Password.ShouldBe("mqtt_pass");
+    opts.Mqtt.Token.ShouldBe("mqtt_token");
+    opts.Mqtt.AuthTimeout.ShouldBe(3.0);
+}
+
+[Fact]
+public void MqttConf_Tls()
+{
+    var opts = ConfigProcessor.ProcessConfigFile(TestDataPath("mqtt.conf"));
+    opts.Mqtt.ShouldNotBeNull();
+    opts.Mqtt!.TlsCert.ShouldBe("/path/to/mqtt-cert.pem");
+    opts.Mqtt.TlsKey.ShouldBe("/path/to/mqtt-key.pem");
+    opts.Mqtt.TlsCaCert.ShouldBe("/path/to/mqtt-ca.pem");
+    opts.Mqtt.TlsVerify.ShouldBeTrue();
+    opts.Mqtt.TlsTimeout.ShouldBe(5.0);
+    opts.Mqtt.HasTls.ShouldBeTrue();
+}
+
+[Fact]
+public void MqttConf_QosSettings()
+{
+    var opts = ConfigProcessor.ProcessConfigFile(TestDataPath("mqtt.conf"));
+    opts.Mqtt.ShouldNotBeNull();
+    opts.Mqtt!.AckWait.ShouldBe(TimeSpan.FromSeconds(60));
+    opts.Mqtt.MaxAckPending.ShouldBe((ushort)2048);
+    opts.Mqtt.JsApiTimeout.ShouldBe(TimeSpan.FromSeconds(10));
+}
+
+[Fact]
+public void MqttConf_JetStreamSettings()
+{
+    var opts = ConfigProcessor.ProcessConfigFile(TestDataPath("mqtt.conf"));
+    opts.Mqtt.ShouldNotBeNull();
+    opts.Mqtt!.JsDomain.ShouldBe("mqtt-domain");
+    opts.Mqtt.StreamReplicas.ShouldBe(3);
+    opts.Mqtt.ConsumerReplicas.ShouldBe(1);
+    opts.Mqtt.ConsumerMemoryStorage.ShouldBeTrue();
+    opts.Mqtt.ConsumerInactiveThreshold.ShouldBe(TimeSpan.FromMinutes(5));
+}
+
+[Fact]
+public void MqttConf_MaxAckPendingValidation_ReportsError()
+{
+    var ex = Should.Throw<ConfigProcessorException>(() =>
+        ConfigProcessor.ProcessConfig("""
+            mqtt {
+                max_ack_pending: 70000
+            }
+            """));
+    ex.Errors.ShouldContain(e => e.Contains("max_ack_pending"));
+}
+
+[Fact]
+public void MqttConf_Aliases()
+{
+    // Test alias keys: "ackwait" (alias for "ack_wait"), "net" (alias for "host"),
+    // "max_inflight" (alias for "max_ack_pending"), "consumer_auto_cleanup" (alias)
+    var opts = ConfigProcessor.ProcessConfig("""
+        mqtt {
+            net: "127.0.0.1"
+            port: 1884
+            ackwait: "45s"
+            max_inflight: 500
+            api_timeout: "8s"
+            consumer_auto_cleanup: "10m"
+        }
+        """);
+    opts.Mqtt.ShouldNotBeNull();
+    opts.Mqtt!.Host.ShouldBe("127.0.0.1");
+    opts.Mqtt.Port.ShouldBe(1884);
+    opts.Mqtt.AckWait.ShouldBe(TimeSpan.FromSeconds(45));
+    opts.Mqtt.MaxAckPending.ShouldBe((ushort)500);
+    opts.Mqtt.JsApiTimeout.ShouldBe(TimeSpan.FromSeconds(8));
+    opts.Mqtt.ConsumerInactiveThreshold.ShouldBe(TimeSpan.FromMinutes(10));
+}
+
+[Fact]
+public void MqttConf_Absent_ReturnsNull()
+{
+    var opts = ConfigProcessor.ProcessConfig("port: 4222");
+    opts.Mqtt.ShouldBeNull();
+}
+```
+
+**Step 3: Run MQTT config tests**
+
+Run: `dotnet test tests/NATS.Server.Tests/NATS.Server.Tests.csproj --filter "FullyQualifiedName~ConfigProcessorTests.MqttConf" -v minimal`
+Expected: PASS.
+
+**Step 4: Commit**
+
+```bash
+git add tests/NATS.Server.Tests/TestData/mqtt.conf tests/NATS.Server.Tests/ConfigProcessorTests.cs
+git commit -m "test: add mqtt config parsing coverage"
+```
+
+---
+
+### Task 8: Expand MqttOptsVarz and wire into /varz
+
+**Files:**
+- Modify: `src/NATS.Server/Monitoring/Varz.cs` (lines 350-360: expand `MqttOptsVarz`)
+- Modify: `src/NATS.Server/Monitoring/VarzHandler.cs` (line 67-124: populate MQTT block from options)
+
+**Step 1: Expand `MqttOptsVarz` class**
+
+In `src/NATS.Server/Monitoring/Varz.cs`, replace the existing minimal `MqttOptsVarz` (lines 350-360) with the full Go-compatible struct (matching Go server/monitor.go:1365-1378):
+
+```csharp
+/// <summary>
+/// MQTT configuration monitoring information.
+/// Corresponds to Go server/monitor.go MQTTOptsVarz struct.
+/// </summary>
+public sealed class MqttOptsVarz
+{
+    [JsonPropertyName("host")]
+    public string Host { get; set; } = "";
+
+    [JsonPropertyName("port")]
+    public int Port { get; set; }
+
+    [JsonPropertyName("no_auth_user")]
+    public string NoAuthUser { get; set; } = "";
+
+    [JsonPropertyName("auth_timeout")]
+    public double AuthTimeout { get; set; }
+
+    [JsonPropertyName("tls_map")]
+    public bool TlsMap { get; set; }
+
+    [JsonPropertyName("tls_timeout")]
+    public double TlsTimeout { get; set; }
+
+    [JsonPropertyName("tls_pinned_certs")]
+    public string[] TlsPinnedCerts { get; set; } = [];
+
+    [JsonPropertyName("js_domain")]
+    public string JsDomain { get; set; } = "";
+
+    [JsonPropertyName("ack_wait")]
+    public long AckWait { get; set; }
+
+    [JsonPropertyName("max_ack_pending")]
+    public ushort MaxAckPending { get; set; }
+}
+```
+
+Note: Go's `AckWait` is serialized as `time.Duration` (nanoseconds as int64). We follow the same pattern used for `PingInterval` and `WriteDeadline` in the existing Varz class.
+
+**Step 2: Populate MQTT block in VarzHandler**
+
+In `src/NATS.Server/Monitoring/VarzHandler.cs`, add MQTT population to the `return new Varz { ... }` block (around line 123, after `HttpReqStats`):
+
+```csharp
+Mqtt = BuildMqttVarz(),
+```
+
+And add the helper method to `VarzHandler`:
+
+```csharp
+private MqttOptsVarz BuildMqttVarz()
+{
+    var mqtt = _options.Mqtt;
+    if (mqtt is null)
+        return new MqttOptsVarz();
+
+    return new MqttOptsVarz
+    {
+        Host = mqtt.Host,
+        Port = mqtt.Port,
+        NoAuthUser = mqtt.NoAuthUser ?? "",
+        AuthTimeout = mqtt.AuthTimeout,
+        TlsMap = mqtt.TlsMap,
+        TlsTimeout = mqtt.TlsTimeout,
+        TlsPinnedCerts = mqtt.TlsPinnedCerts?.ToArray() ?? [],
+        JsDomain = mqtt.JsDomain ?? "",
+        AckWait = (long)mqtt.AckWait.TotalNanoseconds,
+        MaxAckPending = mqtt.MaxAckPending,
+    };
+}
+```
+
+**Step 3: Build to verify compilation**
+
+Run: `dotnet build`
+Expected: Build succeeded.
+
+**Step 4: Add varz MQTT test**
+
+In `tests/NATS.Server.Tests/MonitorTests.cs`, add a test that verifies the MQTT section appears in `/varz` response. If there's an existing varz test pattern, follow it. Otherwise add:
+
+```csharp
+[Fact]
+public async Task Varz_includes_mqtt_config_when_set()
+{
+    // Start server with monitoring enabled and mqtt config set.
+    // GET /varz.
+    // Assert response contains "mqtt" block with expected host/port values.
+}
+```
+
+The exact test implementation depends on how the existing varz tests create and query the server — follow the existing pattern in MonitorTests.cs.
+
+**Step 5: Run full test suite**
+
+Run: `dotnet test tests/NATS.Server.Tests/NATS.Server.Tests.csproj -v minimal`
+Expected: PASS.
+
+**Step 6: Commit**
+
+```bash
+git add src/NATS.Server/Monitoring/Varz.cs src/NATS.Server/Monitoring/VarzHandler.cs tests/NATS.Server.Tests/MonitorTests.cs
+git commit -m "feat: expand mqtt varz monitoring with all Go-compatible fields"
+```
+
+---
+
+### Task 9: Final verification and differences.md update
+
+**Files:**
+- Modify: `differences.md`
+
+**Step 1: Run full test suite**
+
+Run: `dotnet test tests/NATS.Server.Tests/NATS.Server.Tests.csproj -v minimal`
+Expected: PASS (all tests green, no regressions).
+
+**Step 2: Update parity document**
+
+Edit `differences.md`:
+
+1. In the **Connection Types** table (section 2), update the MQTT row:
+
+```markdown
+| MQTT clients | Y | Partial | JWT connection-type constants + config parsing; no MQTT transport yet |
+```
+
+2. In the **Connz Response** table (section 7), update the MQTT client ID filtering row:
+
+```markdown
+| MQTT client ID filtering | Y | Y | `mqtt_client` query param filters open and closed connections |
+```
+
+3. In the **Missing Options Categories** (section 6), replace the "WebSocket/MQTT options" line:
+
+```markdown
+- WebSocket options
+- ~~MQTT options~~ — `mqtt {}` config block parsed with all Go `MQTTOpts` fields; no listener yet
+```
+
+4. In the **Auth Mechanisms** table (section 5), add note to JWT row:
+
+```markdown
+| JWT validation | Y | Y | ... + `allowed_connection_types` enforcement with Go-compatible semantics |
+```
+
+**Step 3: Commit docs update**
+
+```bash
+git add differences.md
+git commit -m "docs: update differences.md for mqtt connection type parity"
+```
--- a/docs/plans/2026-02-23-mqtt-connection-type-plan.md.tasks.json
+++ b/docs/plans/2026-02-23-mqtt-connection-type-plan.md.tasks.json
@@ -0,0 +1,15 @@
+{
+  "planPath": "docs/plans/2026-02-23-mqtt-connection-type-plan.md",
+  "tasks": [
+    {"id": 2, "subject": "Task 1: Add failing JWT connection-type behavior tests", "status": "pending"},
+    {"id": 3, "subject": "Task 2: Implement auth connection-type model and Go-style conversion", "status": "pending", "blockedBy": [2]},
+    {"id": 4, "subject": "Task 3: Add failing connz mqtt_client filter tests", "status": "pending", "blockedBy": [3]},
+    {"id": 5, "subject": "Task 4: Implement connz mqtt_client filtering", "status": "pending", "blockedBy": [4]},
+    {"id": 6, "subject": "Task 5: Verification checkpoint for JWT + connz tasks", "status": "pending", "blockedBy": [5]},
+    {"id": 7, "subject": "Task 6: Add MqttOptions model and config parsing", "status": "pending", "blockedBy": [6]},
+    {"id": 8, "subject": "Task 7: Add MQTT config parsing tests", "status": "pending", "blockedBy": [7]},
+    {"id": 9, "subject": "Task 8: Expand MqttOptsVarz and wire into /varz", "status": "pending", "blockedBy": [8]},
+    {"id": 10, "subject": "Task 9: Final verification and differences.md update", "status": "pending", "blockedBy": [9]}
+  ],
+  "lastUpdated": "2026-02-23T00:00:00Z"
+}