# Remaining Gap Closure Implementation Plan (93 Gaps, 8 Phases)

> **For Claude:** REQUIRED SUB-SKILL: Use superpowers-extended-cc:executing-plans to implement this plan task-by-task.

**Goal:** Close all 93 remaining implementation gaps between the Go NATS server and the .NET port, completing the feature-complete parity across FileStore, RAFT, JetStream Cluster, API, Consumer, Stream, Client, MQTT, Config, Gateway, Route, LeafNode, Account, Monitoring, and WebSocket subsystems.

**Architecture:** Bottom-up dependency approach — Phase 1 builds storage durability and RAFT completion, Phase 2 adds cluster coordination and API layer, Phase 3 adds consumer engines and stream lifecycle, Phase 4 adds client protocol and MQTT, Phase 5 adds config reload and gateway, Phase 6 adds route clustering and leaf nodes, Phase 7 adds account management, Phase 8 adds monitoring and WebSocket.

**Tech Stack:** .NET 10 / C# 14, xUnit 3, Shouldly, NSubstitute, System.IO.Hashing (XxHash64), System.IO.Pipelines, IronSnappy (S2), ChaCha20-Poly1305/AES-GCM, SQLite (test parity DB)

**Test strategy:** Only run targeted unit tests during implementation (`dotnet test --filter`). Run full test suite every 2 phases (after Phase 2, 4, 6, 8). Update `docs/test_parity.db` per phase.

**Parity DB update pattern:**
```bash
sqlite3 docs/test_parity.db "UPDATE go_tests SET status='mapped', dotnet_test='DotNetTestName', dotnet_file='TestFile.cs' WHERE go_test='GoTestName';"
sqlite3 docs/test_parity.db "INSERT INTO dotnet_tests (test_name, test_file, category) VALUES ('TestName', 'TestFile.cs', 'category');"
```

---

## Phase 1: FileStore Durability + RAFT Completion (11 gaps)

**Dependencies:** None — pure infrastructure
**Exit gate:** Checksums validated on read, atomic writes verified, tombstones persisted/recovered, cache expires correctly, filtered queries use SubjectTree, RAFT streams snapshots in chunks, transfers leadership, compacts with policies, checks quorum, jitters elections

---

### Task 1: FileStore Checksum Validation (Gap 1.5)

Add per-block last-checksum tracking and read-path validation using existing XxHash64 in `MessageRecord`.

**Files:**
- Modify: `src/NATS.Server/JetStream/Storage/MsgBlock.cs:25-44` (add `_lastChecksum` field)
- Modify: `src/NATS.Server/JetStream/Storage/MsgBlock.cs:298` (`Read` method — add validation)
- Modify: `src/NATS.Server/JetStream/Storage/MessageRecord.cs:115` (`Decode` — expose checksum)
- Test: `tests/NATS.Server.Tests/JetStream/Storage/FileStoreChecksumTests.cs` (create)
- Go ref: `filestore.go:2204` (lastChecksum), `filestore.go:8180` (validation in msgFromBufEx)

**Step 1: Write failing tests**

Create `tests/NATS.Server.Tests/JetStream/Storage/FileStoreChecksumTests.cs`:

```csharp
using NATS.Server.JetStream.Storage;

namespace NATS.Server.Tests.JetStream.Storage;

public class FileStoreChecksumTests : IDisposable
{
    private readonly DirectoryInfo _dir = Directory.CreateTempSubdirectory("checksum-");

    public void Dispose() => _dir.Delete(true);

    [Fact]
    public void MsgBlock_tracks_last_checksum()
    {
        using var block = MsgBlock.Create(1, _dir.FullName, 1024 * 1024);
        block.Write("test", ReadOnlyMemory<byte>.Empty, "hello"u8.ToArray());
        block.LastChecksum.ShouldNotBeNull();
        block.LastChecksum.Length.ShouldBe(8); // XxHash64 = 8 bytes
    }

    [Fact]
    public void MsgBlock_validates_checksum_on_read()
    {
        using var block = MsgBlock.Create(1, _dir.FullName, 1024 * 1024);
        block.Write("test", ReadOnlyMemory<byte>.Empty, "hello"u8.ToArray());
        block.Flush();

        // Read should succeed with valid checksum
        var record = block.Read(1);
        record.ShouldNotBeNull();
        record!.Subject.ShouldBe("test");
    }

    [Fact]
    public void MsgBlock_detects_corrupted_record()
    {
        using var block = MsgBlock.Create(1, _dir.FullName, 1024 * 1024);
        block.Write("test", ReadOnlyMemory<byte>.Empty, "hello"u8.ToArray());
        block.Flush();
        block.ClearCache();

        // Corrupt a byte in the block file
        var files = Directory.GetFiles(_dir.FullName, "*.blk");
        var bytes = File.ReadAllBytes(files[0]);
        bytes[^10] ^= 0xFF;
        File.WriteAllBytes(files[0], bytes);

        Should.Throw<InvalidDataException>(() => block.Read(1));
    }

    [Fact]
    public void MsgBlock_validates_checksum_flag_controls_behavior()
    {
        using var block = MsgBlock.Create(1, _dir.FullName, 1024 * 1024, validateOnRead: false);
        block.Write("test", ReadOnlyMemory<byte>.Empty, "hello"u8.ToArray());
        block.Flush();
        block.ClearCache();

        // Even with corruption, no exception when validation disabled
        var files = Directory.GetFiles(_dir.FullName, "*.blk");
        var bytes = File.ReadAllBytes(files[0]);
        bytes[^10] ^= 0xFF;
        File.WriteAllBytes(files[0], bytes);

        var record = block.Read(1);
        // May return null or corrupted data, but should not throw
    }
}
```

**Step 2: Run tests to verify they fail**

```bash
dotnet test tests/NATS.Server.Tests --filter "FullyQualifiedName~FileStoreChecksumTests" -v normal
```
Expected: Compilation errors (missing `LastChecksum`, `validateOnRead` parameter)

**Step 3: Implement**

1. Add `_lastChecksum: byte[]?` field and `LastChecksum` property to `MsgBlock.cs`
2. Add `_validateOnRead: bool` parameter to `Create` and `Recover` factory methods
3. Update `Write` to capture checksum from `MessageRecord.Encode` result
4. Update `Read` to validate checksum when `_validateOnRead` is true and record is loaded from disk (not cache)
5. Expose `Checksum` property on `MessageRecord` from the decoded trailer

**Step 4: Run tests to verify they pass**

```bash
dotnet test tests/NATS.Server.Tests --filter "FullyQualifiedName~FileStoreChecksumTests" -v normal
```

**Step 5: Commit**

```bash
git add src/NATS.Server/JetStream/Storage/MsgBlock.cs src/NATS.Server/JetStream/Storage/MessageRecord.cs tests/NATS.Server.Tests/JetStream/Storage/FileStoreChecksumTests.cs
git commit -m "feat: add checksum validation on MsgBlock read path (Gap 1.5)"
```

---

### Task 2: Atomic File Overwrites (Gap 1.6)

Add `AtomicFileWriter` helper and `SemaphoreSlim` write lock to `FileStore` for crash-safe state persistence.

**Files:**
- Create: `src/NATS.Server/JetStream/Storage/AtomicFileWriter.cs`
- Modify: `src/NATS.Server/JetStream/Storage/FileStore.cs:1827` (`WriteStreamState` — use atomic writer)
- Test: `tests/NATS.Server.Tests/JetStream/Storage/AtomicFileWriterTests.cs` (create)
- Go ref: `filestore.go:10599` (_writeFullState)

**Step 1: Write failing tests**

```csharp
using NATS.Server.JetStream.Storage;

namespace NATS.Server.Tests.JetStream.Storage;

public class AtomicFileWriterTests : IDisposable
{
    private readonly DirectoryInfo _dir = Directory.CreateTempSubdirectory("atomic-");
    public void Dispose() => _dir.Delete(true);

    [Fact]
    public async Task WriteAtomicallyAsync_creates_file()
    {
        var path = Path.Combine(_dir.FullName, "state.json");
        await AtomicFileWriter.WriteAtomicallyAsync(path, "hello"u8.ToArray());
        File.Exists(path).ShouldBeTrue();
        (await File.ReadAllTextAsync(path)).ShouldBe("hello");
    }

    [Fact]
    public async Task WriteAtomicallyAsync_no_temp_file_remains()
    {
        var path = Path.Combine(_dir.FullName, "state.json");
        await AtomicFileWriter.WriteAtomicallyAsync(path, "data"u8.ToArray());
        Directory.GetFiles(_dir.FullName, "*.tmp").ShouldBeEmpty();
    }

    [Fact]
    public async Task WriteAtomicallyAsync_overwrites_existing()
    {
        var path = Path.Combine(_dir.FullName, "state.json");
        await AtomicFileWriter.WriteAtomicallyAsync(path, "old"u8.ToArray());
        await AtomicFileWriter.WriteAtomicallyAsync(path, "new"u8.ToArray());
        (await File.ReadAllTextAsync(path)).ShouldBe("new");
    }
}
```

**Step 2: Run tests — expect compilation failure**

**Step 3: Implement**

1. Create `AtomicFileWriter.cs` with static `WriteAtomicallyAsync(string path, byte[] data)`: write to `{path}.tmp`, flush to disk, `File.Move(overwrite: true)`
2. Add `SemaphoreSlim _stateWriteLock = new(1, 1)` to `FileStore`
3. Update `WriteStreamState()` to use `_stateWriteLock` and `AtomicFileWriter`

**Step 4: Run tests — expect pass**

**Step 5: Commit**

```bash
git add src/NATS.Server/JetStream/Storage/AtomicFileWriter.cs src/NATS.Server/JetStream/Storage/FileStore.cs tests/NATS.Server.Tests/JetStream/Storage/AtomicFileWriterTests.cs
git commit -m "feat: add atomic file writer with SemaphoreSlim for crash-safe state writes (Gap 1.6)"
```

---

### Task 3: Tombstone & Deletion Tracking (Gap 1.7)

Replace `HashSet<ulong> _deleted` with sparse `SequenceSet` and add secure erase support.

**Files:**
- Create: `src/NATS.Server/JetStream/Storage/SequenceSet.cs`
- Modify: `src/NATS.Server/JetStream/Storage/MsgBlock.cs:30` (replace `_deleted`)
- Modify: `src/NATS.Server/JetStream/Storage/MsgBlock.cs:332` (`Delete` — add secure erase)
- Modify: `src/NATS.Server/JetStream/Storage/FileStore.cs` (recover tombstones)
- Test: `tests/NATS.Server.Tests/JetStream/Storage/SequenceSetTests.cs` (create)
- Test: `tests/NATS.Server.Tests/JetStream/Storage/FileStoreTombstoneTrackingTests.cs` (create)
- Go ref: `filestore.go:5267` (removeMsg), `filestore.go:5890` (eraseMsg)

**Step 1: Write failing tests**

`SequenceSetTests.cs` — tests for range-compressed sorted set: Add, Remove, Contains, Count, ranges collapse (e.g., adding 1,2,3 stores as range [1-3]).

`FileStoreTombstoneTrackingTests.cs` — tests for: tombstones survive MsgBlock recovery, secure erase overwrites data with random bytes, `SequenceSet` used instead of `HashSet`.

**Step 2: Run tests — expect compilation failure**

**Step 3: Implement**

1. `SequenceSet.cs`: sorted list of `(ulong Start, ulong End)` ranges with range compression, binary search for Contains/Add/Remove
2. Replace `_deleted: HashSet<ulong>` with `_deleted: SequenceSet` in `MsgBlock.cs`
3. Add `secureErase` parameter to `MsgBlock.Delete()` — when true, overwrite payload bytes with `RandomNumberGenerator.Fill`
4. Persist tombstone records using existing `DeletedFlag = 0x80` in `MessageRecord`
5. Recover tombstones during `RebuildIndex()` by checking the deleted flag

**Step 4: Run tests — expect pass**

**Step 5: Commit**

```bash
git add src/NATS.Server/JetStream/Storage/SequenceSet.cs src/NATS.Server/JetStream/Storage/MsgBlock.cs src/NATS.Server/JetStream/Storage/FileStore.cs tests/NATS.Server.Tests/JetStream/Storage/SequenceSetTests.cs tests/NATS.Server.Tests/JetStream/Storage/FileStoreTombstoneTrackingTests.cs
git commit -m "feat: add SequenceSet for sparse deletion tracking with secure erase (Gap 1.7)"
```

---

### Task 4: Multi-Block Write Cache (Gap 1.8)

Add `WriteCacheManager` to `FileStore` with bounded strong-reference cache, TTL eviction, and background flush.

**Files:**
- Modify: `src/NATS.Server/JetStream/Storage/FileStore.cs` (add `WriteCacheManager` inner class)
- Modify: `src/NATS.Server/JetStream/Storage/MsgBlock.cs` (integrate cache manager)
- Test: `tests/NATS.Server.Tests/JetStream/Storage/WriteCacheTests.cs` (create)
- Go ref: `filestore.go:4443` (setupWriteCache), `filestore.go:6148` (expireCache)

**Step 1: Write failing tests**

Tests for: cache entries evicted after TTL (2s default), cache bounded by size (64MB default), `FlushPendingMsgsAsync` flushes all cached entries, `PeriodicTimer` background worker.

**Step 2-5: Implement, test, commit**

Implement `WriteCacheManager` as inner class with `PeriodicTimer` (500ms tick), bounded `Dictionary<int, CacheEntry>` keyed by block ID, size tracking, TTL eviction. Integrate into `FileStore.StoreMsg` and `FileStore.RotateBlock`.

```bash
git commit -m "feat: add bounded write cache with TTL eviction and background flush (Gap 1.8)"
```

---

### Task 5: Query/Filter Operations (Gap 1.10)

Optimize `FilteredState`, `LoadMsg`, and `NumFiltered` with block-aware binary search.

**Files:**
- Modify: `src/NATS.Server/JetStream/Storage/FileStore.cs:471` (`FilteredState` — use block index ranges)
- Modify: `src/NATS.Server/JetStream/Storage/FileStore.cs:1459` (`LoadMsg` — block-aware binary search)
- Test: `tests/NATS.Server.Tests/JetStream/Storage/FileStoreFilterQueryTests.cs` (create)
- Go ref: `filestore.go:3191` (FilteredState), `filestore.go:8308` (LoadMsg)

**Step 1-5: TDD cycle**

Tests for: `FilteredState` with wildcard subjects, `LoadMsg` with block boundary crossing, `CheckSkipFirstBlock` optimization for range queries, `NumFiltered` with caching. Use `SubjectMatch.IsMatch()` for token-based filter matching.

```bash
git commit -m "feat: optimize FilteredState and LoadMsg with block-aware search (Gap 1.10)"
```

---

### Task 6: RAFT InstallSnapshot Streaming (Gap 8.3)

Add chunk-based snapshot streaming with CRC32 validation.

**Files:**
- Create: `src/NATS.Server/Raft/SnapshotChunkEnumerator.cs`
- Modify: `src/NATS.Server/Raft/RaftNode.cs:414` (`InstallSnapshotFromChunksAsync` — add CRC validation)
- Modify: `src/NATS.Server/Raft/RaftWireFormat.cs` (add `RaftInstallSnapshotChunkWire`)
- Test: `tests/NATS.Server.Tests/Raft/RaftSnapshotStreamingTests.cs` (create)
- Go ref: `raft.go` snapshot install with chunks

**Step 1: Write failing tests**

```csharp
[Fact]
public void SnapshotChunkEnumerator_yields_fixed_size_chunks()
{
    var data = new byte[200_000]; // ~3 chunks at 64KB
    Random.Shared.NextBytes(data);
    var chunks = new SnapshotChunkEnumerator(data, chunkSize: 65536).ToList();
    chunks.Count.ShouldBe(4); // 64K + 64K + 64K + remainder
    chunks.Sum(c => c.Length).ShouldBe(200_000);
}

[Fact]
public async Task InstallSnapshot_validates_crc32_over_assembled_content()
{
    var node = new RaftNode("n1");
    var data = "snapshot-data"u8.ToArray();
    var chunks = new SnapshotChunkEnumerator(data, 8).ToList();

    // Corrupt one chunk
    chunks[0][0] ^= 0xFF;

    await Should.ThrowAsync<InvalidDataException>(
        () => node.InstallSnapshotFromChunksAsync(chunks, 1, 1, default));
}
```

**Step 2-5: Implement, test, commit**

```bash
git commit -m "feat: add chunk-based snapshot streaming with CRC32 validation (Gap 8.3)"
```

---

### Task 7: RAFT Leadership Transfer (Gap 8.4)

Add `TransferLeadership` with `TimeoutNowRpc` message type.

**Files:**
- Modify: `src/NATS.Server/Raft/RaftNode.cs` (add `TransferLeadershipAsync`)
- Modify: `src/NATS.Server/Raft/RaftWireFormat.cs` (add `TimeoutNowRpc` wire type)
- Test: `tests/NATS.Server.Tests/Raft/RaftLeadershipTransferTests.cs` (create)
- Go ref: `raft.go` leadership transfer

**Step 1-5: TDD cycle**

Tests for: target receives `TimeoutNow` and starts election immediately, leader stops accepting proposals during transfer, transfer times out after 2x election timeout if not completed. Implement `TransferLeadershipAsync(string targetId)` on `RaftNode`.

```bash
git commit -m "feat: add leadership transfer via TimeoutNow RPC (Gap 8.4)"
```

---

### Task 8: RAFT Log Compaction Policies (Gap 8.5)

Add `CompactionPolicy` enum and configurable compaction thresholds.

**Files:**
- Create: `src/NATS.Server/Raft/CompactionPolicy.cs`
- Modify: `src/NATS.Server/Raft/RaftNode.cs:400` (`CompactLogAsync` — use policy)
- Test: `tests/NATS.Server.Tests/Raft/RaftCompactionPolicyTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: `ByCount` policy compacts when log exceeds N entries, `BySize` compacts when total size exceeds threshold, `ByAge` compacts entries older than duration. Implement `CompactionPolicy` enum with `ByCount`, `BySize`, `ByAge` variants and `RaftOptions.CompactionPolicy`/thresholds.

```bash
git commit -m "feat: add configurable log compaction policies (Gap 8.5)"
```

---

### Task 9: RAFT Quorum Check Before Proposing (Gap 8.6)

Add `HasQuorum()` check using peer heartbeat timestamps.

**Files:**
- Modify: `src/NATS.Server/Raft/RaftNode.cs` (add `HasQuorum`, update `ProposeAsync`)
- Modify: `src/NATS.Server/Raft/RaftPeerState.cs` (ensure `LastContact` tracked)
- Test: `tests/NATS.Server.Tests/Raft/RaftQuorumCheckTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: `HasQuorum` returns false when majority of peers have stale heartbeats, `ProposeAsync` returns `ProposalResult.NoQuorum` when check fails, heartbeat responses update `LastContact`.

```bash
git commit -m "feat: add quorum check before proposing entries (Gap 8.6)"
```

---

### Task 10: RAFT ReadIndex Optimization (Gap 8.7)

Add `ReadIndex()` for linearizable reads without log growth.

**Files:**
- Modify: `src/NATS.Server/Raft/RaftNode.cs` (add `ReadIndexAsync`)
- Test: `tests/NATS.Server.Tests/Raft/RaftReadIndexTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: `ReadIndexAsync` returns current commit index after quorum heartbeat round, deposed leader's `ReadIndexAsync` fails (no quorum), follower can serve read when `appliedIndex >= readIndex`.

```bash
git commit -m "feat: add ReadIndex for linearizable reads via quorum confirmation (Gap 8.7)"
```

---

### Task 11: RAFT Election Timeout Jitter (Gap 8.8)

Add `RandomizedElectionTimeout()` using `TotalMilliseconds`.

**Files:**
- Modify: `src/NATS.Server/Raft/RaftNode.cs:500` (`ResetElectionTimeout` — add jitter)
- Test: `tests/NATS.Server.Tests/Raft/RaftElectionJitterTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: randomized timeout is within `[base, 2*base)` range, uses `TotalMilliseconds` (not `Milliseconds`), different nodes get different timeouts.

```bash
git commit -m "feat: add randomized election timeout jitter (Gap 8.8)"
```

---

### Phase 1 Exit Gate

```bash
dotnet test tests/NATS.Server.Tests --filter "FullyQualifiedName~FileStoreChecksum|FullyQualifiedName~AtomicFileWriter|FullyQualifiedName~SequenceSet|FullyQualifiedName~Tombstone|FullyQualifiedName~WriteCache|FullyQualifiedName~FilterQuery|FullyQualifiedName~SnapshotStreaming|FullyQualifiedName~LeadershipTransfer|FullyQualifiedName~CompactionPolicy|FullyQualifiedName~QuorumCheck|FullyQualifiedName~ReadIndex|FullyQualifiedName~ElectionJitter" -v normal
```

Update test parity DB for all Phase 1 tests.

---

## Phase 2: JetStream Cluster Coordination + API (13 gaps)

**Dependencies:** Phase 1 (RAFT completion)
**Exit gate:** Peers added/removed, RAFT entries applied to state machine, assignments encoded/decoded with golden fixtures, API requests forwarded to leader, rate limiting active, advisory events published

---

### Task 12: Peer Management & Stream Moves (Gap 2.4)

Add `ProcessAddPeer`/`ProcessRemovePeer` to `JetStreamMetaGroup` for peer-driven stream reassignment.

**Files:**
- Modify: `src/NATS.Server/JetStream/Cluster/JetStreamMetaGroup.cs`
- Modify: `src/NATS.Server/JetStream/Cluster/StreamReplicaGroup.cs`
- Test: `tests/NATS.Server.Tests/JetStream/Cluster/PeerManagementTests.cs` (create)
- Go ref: `jetstream_cluster.go:2290-2439`

**Step 1-5: TDD cycle**

Tests for: `ProcessAddPeer` triggers re-replication of under-replicated streams, `ProcessRemovePeer` triggers reassignment away from removed peer, `RemovePeerFromStream` removes specific peer from replica group.

```bash
git commit -m "feat: add peer management with stream reassignment (Gap 2.4)"
```

---

### Task 13: Entry Application Pipeline (Gap 2.7)

Add `ApplyMetaEntries` and `ApplyStreamEntries` dispatchers.

**Files:**
- Modify: `src/NATS.Server/JetStream/Cluster/JetStreamMetaGroup.cs:579` (extend `ApplyEntry`)
- Modify: `src/NATS.Server/JetStream/Cluster/StreamReplicaGroup.cs:193` (extend `ApplyCommittedEntriesAsync`)
- Test: `tests/NATS.Server.Tests/JetStream/Cluster/EntryApplicationTests.cs` (create)
- Go ref: `jetstream_cluster.go:2474-4261`

**Step 1-5: TDD cycle**

Tests for: meta entry dispatch (StreamCreate, StreamUpdate, StreamDelete, ConsumerCreate, ConsumerDelete, PeerAdd, PeerRemove), stream entry dispatch (store, remove, purge), consumer entry dispatch (ack, nak, deliver).

```bash
git commit -m "feat: add entry application pipeline for meta and stream RAFT groups (Gap 2.7)"
```

---

### Task 14: Topology-Aware Placement (Gap 2.8)

Extend `PlacementEngine.SelectPeerGroup` with tag enforcement, HA limits, and weighted selection.

**Files:**
- Modify: `src/NATS.Server/JetStream/Cluster/PlacementEngine.cs:14`
- Modify: `src/NATS.Server/JetStream/Cluster/PlacementEngine.cs:62` (`PeerInfo` — add tags, storage)
- Test: `tests/NATS.Server.Tests/JetStream/Cluster/TopologyPlacementTests.cs` (create)
- Go ref: `jetstream_cluster.go:7524-7618` (selectPeerGroup)

**Step 1-5: TDD cycle**

Tests for: `JetStreamUniqueTag` enforcement (no two replicas on same-tagged node), HA asset limits per peer, tag include/exclude with prefix matching, weighted selection by available resources.

```bash
git commit -m "feat: add topology-aware placement with tag enforcement (Gap 2.8)"
```

---

### Task 15: RAFT Group Creation & Lifecycle (Gap 2.9)

Flesh out `RaftGroup` with factory method and member helpers.

**Files:**
- Modify: `src/NATS.Server/JetStream/Cluster/ClusterAssignmentTypes.cs:9` (`RaftGroup`)
- Test: `tests/NATS.Server.Tests/JetStream/Cluster/RaftGroupLifecycleTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: `IsMember(peerId)`, `SetPreferred(peerId)`, `CreateRaftGroup` factory uses PlacementEngine.

```bash
git commit -m "feat: add RaftGroup lifecycle methods (Gap 2.9)"
```

---

### Task 16: Assignment Encoding/Decoding (Gap 2.10)

Add `AssignmentCodec` with binary serialization matching Go wire format, golden fixture tests.

**Files:**
- Create: `src/NATS.Server/JetStream/Cluster/AssignmentCodec.cs`
- Test: `tests/NATS.Server.Tests/JetStream/Cluster/AssignmentCodecTests.cs` (create)
- Go ref: `jetstream_cluster.go` encode/decode functions

**Step 1-5: TDD cycle**

Tests for: encode/decode round-trip for stream assignments, consumer assignments, S2 compression for configs > 1KB, golden fixture tests with captured Go output bytes for format compatibility.

```bash
git commit -m "feat: add binary assignment codec with golden fixture tests (Gap 2.10)"
```

---

### Task 17: Unsupported Asset Handling (Gap 2.11)

Add graceful handling for version-incompatible stream/consumer assignments.

**Files:**
- Modify: `src/NATS.Server/JetStream/Cluster/JetStreamMetaGroup.cs`
- Test: `tests/NATS.Server.Tests/JetStream/Cluster/UnsupportedAssetTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: unknown version assignment logged as warning and skipped, does not crash cluster.

```bash
git commit -m "feat: add unsupported asset handling for mixed-version clusters (Gap 2.11)"
```

---

### Task 18: Clustered API Handlers (Gap 2.12)

Add `JsClusteredStreamRequest` and `JsClusteredStreamUpdateRequest`.

**Files:**
- Modify: `src/NATS.Server/JetStream/Api/Handlers/StreamApiHandlers.cs`
- Modify: `src/NATS.Server/JetStream/Api/Handlers/ConsumerApiHandlers.cs`
- Test: `tests/NATS.Server.Tests/JetStream/Api/ClusteredApiTests.cs` (create)
- Go ref: `jetstream_cluster.go:7620-8265`

**Step 1-5: TDD cycle**

Tests for: stream create proposes to meta RAFT, stream update proposes with validation, system subscriptions for result processing.

```bash
git commit -m "feat: add clustered stream/consumer API handlers (Gap 2.12)"
```

---

### Task 19: Leader Forwarding (Gap 7.1)

Implement `ForwardToLeader` middleware in `JetStreamApiRouter`.

**Files:**
- Modify: `src/NATS.Server/JetStream/Api/JetStreamApiRouter.cs:97` (`ForwardToLeader` — implement)
- Test: `tests/NATS.Server.Tests/JetStream/Api/LeaderForwardingTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: request forwarded when not meta leader, forwarded response returned to client, timeout after 5 seconds.

```bash
git commit -m "feat: implement leader forwarding for JetStream API (Gap 7.1)"
```

---

### Task 20: Clustered API Request Handlers (Gap 7.2)

Add cluster-aware create/update/delete that propose to RAFT.

**Files:**
- Modify: `src/NATS.Server/JetStream/Api/Handlers/StreamApiHandlers.cs`
- Modify: `src/NATS.Server/JetStream/Api/Handlers/ConsumerApiHandlers.cs`
- Test: `tests/NATS.Server.Tests/JetStream/Api/ClusteredRequestTests.cs` (create)
- Go ref: `jetstream_cluster.go:7620-7701`

**Step 1-5: TDD cycle**

Tests for: cluster-aware create proposes to RAFT, waits for proposal result, returns error on proposal failure.

```bash
git commit -m "feat: add cluster-aware API request handlers (Gap 7.2)"
```

---

### Task 21: API Rate Limiting & Deduplication (Gap 7.3)

Add `ApiRateLimiter` with `SemaphoreSlim`-based concurrency limiting and request deduplication.

**Files:**
- Create: `src/NATS.Server/JetStream/Api/ApiRateLimiter.cs`
- Modify: `src/NATS.Server/JetStream/Api/JetStreamApiRouter.cs` (integrate limiter)
- Test: `tests/NATS.Server.Tests/JetStream/Api/ApiRateLimiterTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: concurrent requests capped at max (default 256), duplicate `Nats-Request-Id` returns cached response, TTL expiration of dedup entries (5 seconds).

```bash
git commit -m "feat: add API rate limiting and request deduplication (Gap 7.3)"
```

---

### Task 22: Snapshot & Restore API Stub (Gap 7.4)

Wire `$JS.API.STREAM.SNAPSHOT` and `$JS.API.STREAM.RESTORE` endpoints.

**Files:**
- Modify: `src/NATS.Server/JetStream/Api/Handlers/StreamApiHandlers.cs:157` (complete `HandleSnapshot`)
- Modify: `src/NATS.Server/JetStream/Api/Handlers/StreamApiHandlers.cs:176` (complete `HandleRestore`)
- Test: `tests/NATS.Server.Tests/JetStream/Api/SnapshotApiTests.cs` (create)

Note: Full snapshot behavior completed in Phase 3 Task 37 (Gap 4.7).

**Step 1-5: TDD cycle**

Tests for: endpoint responds to correct subject, validates stream exists, calls `StreamSnapshotService`.

```bash
git commit -m "feat: wire snapshot/restore API endpoints (Gap 7.4 stub)"
```

---

### Task 23: Consumer Pause/Resume API (Gap 7.5)

Wire `$JS.API.CONSUMER.PAUSE` endpoint to existing `ConsumerManager.Pause`.

**Files:**
- Modify: `src/NATS.Server/JetStream/Api/Handlers/ConsumerApiHandlers.cs:79`
- Test: `tests/NATS.Server.Tests/JetStream/Api/ConsumerPauseApiTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: pause endpoint calls `ConsumerManager.Pause` with `pauseUntil`, returns pause state.

```bash
git commit -m "feat: wire consumer pause/resume API endpoint (Gap 7.5)"
```

---

### Task 24: Advisory Event Publication (Gap 7.6)

Add `PublishAdvisory` calls in API handlers for stream/consumer lifecycle events.

**Files:**
- Modify: `src/NATS.Server/JetStream/Api/Handlers/StreamApiHandlers.cs`
- Modify: `src/NATS.Server/JetStream/Api/Handlers/ConsumerApiHandlers.cs`
- Modify: `src/NATS.Server/Events/InternalEventSystem.cs` (add `PublishAdvisoryAsync`)
- Modify: `src/NATS.Server/Events/EventSubjects.cs` (add `$JS.EVENT.ADVISORY.*` subjects)
- Test: `tests/NATS.Server.Tests/JetStream/Api/AdvisoryEventTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: stream create publishes advisory, consumer delete publishes advisory, advisory includes correct event type and payload.

```bash
git commit -m "feat: add advisory event publication for API operations (Gap 7.6)"
```

---

### Phase 2 Exit Gate

```bash
# Targeted tests for Phase 2
dotnet test tests/NATS.Server.Tests --filter "FullyQualifiedName~PeerManagement|FullyQualifiedName~EntryApplication|FullyQualifiedName~TopologyPlacement|FullyQualifiedName~RaftGroupLifecycle|FullyQualifiedName~AssignmentCodec|FullyQualifiedName~UnsupportedAsset|FullyQualifiedName~ClusteredApi|FullyQualifiedName~LeaderForwarding|FullyQualifiedName~ClusteredRequest|FullyQualifiedName~ApiRateLimiter|FullyQualifiedName~SnapshotApi|FullyQualifiedName~ConsumerPauseApi|FullyQualifiedName~AdvisoryEvent" -v normal

# FULL TEST SUITE CHECKPOINT (Phase 2 complete)
dotnet test
```

Update test parity DB for all Phase 2 tests.

---

## Phase 3: Consumer Engines + Stream Lifecycle (13 gaps)

**Dependencies:** Phase 2 (cluster coordination)
**Exit gate:** Consumer delivery loop dispatches messages, heartbeats sent, interest tracked, max deliveries enforced, filter skipping works, rate limiting via token bucket, source consumers configured, snapshot/restore operational

---

### Task 25: Core Message Delivery Loop (Gap 3.1 — CRITICAL)

Implement `LoopAndGatherMsgs` in `PushConsumerEngine`.

**Files:**
- Modify: `src/NATS.Server/JetStream/Consumers/PushConsumerEngine.cs`
- Test: `tests/NATS.Server.Tests/JetStream/Consumers/DeliveryLoopTests.cs` (create)
- Go ref: `consumer.go:1400-1700` (loopAndGatherMsgs)

**Step 1: Write failing tests**

Tests for: delivery loop polls store for new messages, checks redelivery tracker for expired entries, calculates `num_pending` from store state, dispatches messages via client write path, uses `Channel<ConsumerSignal>` for wake-up.

**Step 2-5: Implement, test, commit**

Add `ConsumerSignal` enum (`NewMessage`, `AckEvent`, `ConfigChange`). Add `Channel<ConsumerSignal> _signalChannel` to `PushConsumerEngine`. Implement background `LoopAndGatherMsgs` task that: polls `IStreamStore.LoadNextMsg`, checks `RedeliveryTracker.GetDue()`, dispatches via `SendMessage`.

```bash
git commit -m "feat: implement core message delivery loop for push consumers (Gap 3.1)"
```

---

### Task 26: Idle Heartbeat & Flow Control (Gap 3.5)

Add `SendIdleHeartbeat` and `SendFlowControl` with pending count headers.

**Files:**
- Modify: `src/NATS.Server/JetStream/Consumers/PushConsumerEngine.cs:220` (extend heartbeat)
- Test: `tests/NATS.Server.Tests/JetStream/Consumers/IdleHeartbeatTests.cs` (create)
- Go ref: `consumer.go:5222` (sendIdleHeartbeat), `consumer.go:5495` (sendFlowControl)

**Step 1-5: TDD cycle**

Tests for: heartbeat sent with `Nats-Pending-Messages`/`Nats-Pending-Bytes` headers when no delivery within interval, flow control reply with stall detection.

```bash
git commit -m "feat: add idle heartbeat with pending count headers and flow control (Gap 3.5)"
```

---

### Task 27: Delivery Interest Tracking (Gap 3.8)

Add `DeliveryInterestTracker` monitoring subscribe/unsubscribe events.

**Files:**
- Create: `src/NATS.Server/JetStream/Consumers/DeliveryInterestTracker.cs`
- Modify: `src/NATS.Server/JetStream/Consumers/PushConsumerEngine.cs` (integrate tracker)
- Test: `tests/NATS.Server.Tests/JetStream/Consumers/DeliveryInterestTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: `HasInterest` reflects subscription state, `DeleteNotActive` cleanup after timeout, gateway interest checking.

```bash
git commit -m "feat: add delivery interest tracking with auto-cleanup (Gap 3.8)"
```

---

### Task 28: Max Deliveries Enforcement (Gap 3.9)

Add advisory generation and delivery exceeded policy.

**Files:**
- Modify: `src/NATS.Server/JetStream/Consumers/AckProcessor.cs`
- Modify: `src/NATS.Server/Events/InternalEventSystem.cs` (add `NotifyDeliveryExceeded` event type)
- Test: `tests/NATS.Server.Tests/JetStream/Consumers/MaxDeliveriesTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: advisory generated when delivery count exceeds `MaxDeliver`, `DeliveryExceededPolicy` enum (Drop, DeadLetter).

```bash
git commit -m "feat: add max delivery enforcement with advisory generation (Gap 3.9)"
```

---

### Task 29: Filter Subject Skip Tracking (Gap 3.10)

Add `FilterSkipTracker` using `SubjectMatch.IsMatch()` for token-based filter matching.

**Files:**
- Create: `src/NATS.Server/JetStream/Consumers/FilterSkipTracker.cs`
- Test: `tests/NATS.Server.Tests/JetStream/Consumers/FilterSkipTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: filter matching uses `SubjectMatch.IsMatch()` (NOT Regex), `SortedSet<ulong>` tracks unmatched sequences, `ShouldSkip` returns whether message matches filter.

```bash
git commit -m "feat: add filter skip tracking using SubjectMatch (Gap 3.10)"
```

---

### Task 30: Sample/Observe Mode (Gap 3.11)

Add sample frequency parsing and stochastic latency sampling.

**Files:**
- Modify: `src/NATS.Server/JetStream/Consumers/PushConsumerEngine.cs`
- Test: `tests/NATS.Server.Tests/JetStream/Consumers/SampleModeTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: `"1%"` → 0.01 parsing, `ShouldSample()` uses `Random.Shared`, latency measurement and advisory.

```bash
git commit -m "feat: add sample/observe mode with latency measurement (Gap 3.11)"
```

---

### Task 31: Reset to Sequence (Gap 3.12)

Add `ProcessResetRequest` to `ConsumerManager`.

**Files:**
- Modify: `src/NATS.Server/JetStream/ConsumerManager.cs:218` (extend `Reset`)
- Test: `tests/NATS.Server.Tests/JetStream/Consumers/ConsumerResetTests.cs` (create)
- Go ref: `consumer.go:4241` (processResetReq)

**Step 1-5: TDD cycle**

Tests for: reset to specific sequence updates `NextSequence`, clears pending acks, clears redelivery tracker, publishes advisory.

```bash
git commit -m "feat: add consumer reset to specific sequence (Gap 3.12)"
```

---

### Task 32: Token Bucket Rate Limiting (Gap 3.13)

Add `TokenBucketRateLimiter` for accurate rate limiting.

**Files:**
- Create: `src/NATS.Server/JetStream/Consumers/TokenBucketRateLimiter.cs`
- Modify: `src/NATS.Server/JetStream/Consumers/PushConsumerEngine.cs` (integrate)
- Test: `tests/NATS.Server.Tests/JetStream/Consumers/TokenBucketTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: configurable rate (bytes/sec) and burst size, `WaitForTokenAsync` blocks until tokens available, dynamic rate updates.

```bash
git commit -m "feat: add token bucket rate limiter for consumers (Gap 3.13)"
```

---

### Task 33: Cluster-Aware Pending Requests (Gap 3.14)

Add `ProposeWaitingRequest` for pull requests through consumer RAFT group.

**Files:**
- Modify: `src/NATS.Server/JetStream/Consumers/PullConsumerEngine.cs`
- Test: `tests/NATS.Server.Tests/JetStream/Consumers/ClusterPendingRequestTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: pull requests proposed through consumer RAFT group, cluster-wide pending tracking.

```bash
git commit -m "feat: add cluster-aware pending request tracking for pull consumers (Gap 3.14)"
```

---

### Task 34: Source Consumer Setup (Gap 4.3)

Complete API request generation for source consumers.

**Files:**
- Modify: `src/NATS.Server/JetStream/Streams/SourceCoordinator.cs`
- Test: `tests/NATS.Server.Tests/JetStream/Streams/SourceConsumerSetupTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: consumer create request with `FilterSubject`, `SubjectTransforms`, `OptStartSeq`, flow control, account isolation verification.

```bash
git commit -m "feat: complete source consumer API request generation (Gap 4.3)"
```

---

### Task 35: Stream Snapshot & Restore (Gap 4.7)

Implement TAR-based snapshot with S2 compression and deadline enforcement.

**Files:**
- Modify: `src/NATS.Server/JetStream/Snapshots/StreamSnapshotService.cs`
- Test: `tests/NATS.Server.Tests/JetStream/Snapshots/StreamSnapshotTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: TAR snapshot includes stream config, message blocks, consumer state. S2 compression applied. Deadline enforcement via `CancellationTokenSource`. Consumer inclusion/exclusion. Restore validates TAR, decompresses, rebuilds indices.

```bash
git commit -m "feat: implement TAR-based stream snapshot with S2 compression (Gap 4.7)"
```

---

### Task 36: Stream Config Update Validation (Gap 4.8)

Add `ValidateConfigUpdate` with change restriction rules.

**Files:**
- Modify: `src/NATS.Server/JetStream/StreamManager.cs`
- Test: `tests/NATS.Server.Tests/JetStream/Streams/ConfigUpdateValidationTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: subjects overlap detection, mirror/source immutability, retention policy restrictions, MaxMsgs/MaxBytes/MaxAge monotonic decrease, discard policy compatibility.

```bash
git commit -m "feat: add stream config update validation (Gap 4.8)"
```

---

### Task 37: Source/Mirror Info Reporting (Gap 4.10)

Add `GetMirrorInfo`/`GetSourceInfo` for monitoring.

**Files:**
- Modify: `src/NATS.Server/JetStream/Streams/MirrorCoordinator.cs`
- Modify: `src/NATS.Server/JetStream/Streams/SourceCoordinator.cs`
- Test: `tests/NATS.Server.Tests/JetStream/Streams/SourceMirrorInfoTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: `MirrorInfoResponse` with lag/active/error, `SourceInfoResponse[]`, wired into stream info API.

```bash
git commit -m "feat: add source/mirror info reporting for monitoring (Gap 4.10)"
```

---

### Phase 3 Exit Gate

```bash
dotnet test tests/NATS.Server.Tests --filter "FullyQualifiedName~DeliveryLoop|FullyQualifiedName~IdleHeartbeat|FullyQualifiedName~DeliveryInterest|FullyQualifiedName~MaxDeliveries|FullyQualifiedName~FilterSkip|FullyQualifiedName~SampleMode|FullyQualifiedName~ConsumerReset|FullyQualifiedName~TokenBucket|FullyQualifiedName~ClusterPendingRequest|FullyQualifiedName~SourceConsumerSetup|FullyQualifiedName~StreamSnapshot|FullyQualifiedName~ConfigUpdateValidation|FullyQualifiedName~SourceMirrorInfo" -v normal
```

Update test parity DB for all Phase 3 tests.

---

## Phase 4: Client Protocol + MQTT (12 gaps)

**Dependencies:** Phase 3 (consumer engines)
**Exit gate:** Route result cache active, slow consumers tracked, trace delivery works, SUB permission cached, will messages published, QoS 1/2 tracked, retained delivered on subscribe

---

### Task 38: Per-Account Subscription Result Cache (Gap 5.4)

Add `RouteResultCache` with LRU eviction and generation-based invalidation.

**Files:**
- Create: `src/NATS.Server/Subscriptions/RouteResultCache.cs`
- Modify: `src/NATS.Server/NatsClient.cs` (integrate cache into message dispatch)
- Test: `tests/NATS.Server.Tests/Subscriptions/RouteResultCacheTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: LRU eviction at 8192 entries, per-account partitioning, atomic generation invalidation, cache hit avoids `SubList.Match` call.

```bash
git commit -m "feat: add per-account subscription result cache with LRU (Gap 5.4)"
```

---

### Task 39: Slow Consumer Stall Gate (Gap 5.5)

Extend `StallGate` with per-kind slow consumer statistics.

**Files:**
- Modify: `src/NATS.Server/NatsClient.cs:1017` (`StallGate` — add `SlowConsumerCount`)
- Modify: `src/NATS.Server/Auth/Account.cs` (add `IncrementSlowConsumers`)
- Test: `tests/NATS.Server.Tests/SlowConsumerStallGateTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: `SlowConsumerCount` per `ClientKind`, account-level tracking, `SlowConsumerEvent` fired at threshold.

```bash
git commit -m "feat: add slow consumer per-kind tracking with account counters (Gap 5.5)"
```

---

### Task 40: Dynamic Write Buffer Pooling (Gap 5.6)

Integrate `OutboundBufferPool` with flush coalescing and broadcast drain.

**Files:**
- Modify: `src/NATS.Server/NatsClient.cs:785` (`RunWriteLoopAsync` — add broadcast drain)
- Modify: `src/NATS.Server/IO/OutboundBufferPool.cs`
- Test: `tests/NATS.Server.Tests/IO/DynamicBufferPoolTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: broadcast flush drains multiple pending clients, reduces syscall count for fan-out.

```bash
git commit -m "feat: add dynamic write buffer pooling with broadcast drain (Gap 5.6)"
```

---

### Task 41: Per-Client Trace Level (Gap 5.7)

Add `TraceMsgDelivery` and per-client echo control.

**Files:**
- Modify: `src/NATS.Server/NatsClient.cs` (add `TraceMsgDelivery`, `EchoSupported`)
- Test: `tests/NATS.Server.Tests/ClientTraceTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: trace message delivery logged at Trace level with subject/destination/size, echo flag controls routed message behavior.

```bash
git commit -m "feat: add per-client trace delivery and echo control (Gap 5.7)"
```

---

### Task 42: Subscribe Permission Caching (Gap 5.8)

Extend `PermissionLruCache` with SUB permission entries and generation-based invalidation.

**Files:**
- Modify: `src/NATS.Server/Auth/PermissionLruCache.cs`
- Modify: `src/NATS.Server/Auth/Account.cs` (add `GenerationId`)
- Test: `tests/NATS.Server.Tests/Auth/SubPermissionCacheTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: SUB permission cached alongside PUB, generation ID invalidation on permission changes.

```bash
git commit -m "feat: add SUB permission caching with generation invalidation (Gap 5.8)"
```

---

### Task 43: Internal Client Kinds (Gap 5.9)

Already implemented — `ClientKind.cs` has `System`, `JetStream`, `Account` and `IsInternal()` extension. Verify and add tests if missing.

**Files:**
- Verify: `src/NATS.Server/ClientKind.cs`
- Test: `tests/NATS.Server.Tests/ClientKindTests.cs` (create if missing)

```bash
git commit -m "test: verify internal client kinds (Gap 5.9)"
```

---

### Task 44: Adaptive Read Buffer Short-Read Counter (Gap 5.10)

Add `_consecutiveShortReads` counter with 4-read threshold.

**Files:**
- Modify: `src/NATS.Server/IO/AdaptiveReadBuffer.cs`
- Test: `tests/NATS.Server.Tests/IO/AdaptiveReadBufferShortReadTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: shrink only after 4 consecutive short reads, counter resets on full-buffer read.

```bash
git commit -m "feat: add consecutive short-read counter to prevent buffer oscillation (Gap 5.10)"
```

---

### Task 45: MQTT Will Message Delivery (Gap 6.2)

Add `PublishWillMessage` triggered on abnormal disconnection.

**Files:**
- Modify: `src/NATS.Server/Mqtt/MqttSessionStore.cs`
- Modify: `src/NATS.Server/Mqtt/MqttConnection.cs` (trigger on disconnect)
- Test: `tests/NATS.Server.Tests/Mqtt/MqttWillMessageTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: will message published on abnormal disconnect, NOT published on clean DISCONNECT, will delay interval support.

```bash
git commit -m "feat: add MQTT will message delivery on abnormal disconnect (Gap 6.2)"
```

---

### Task 46: MQTT QoS 1/2 Tracking (Gap 6.3)

Add `MqttQoS1Tracker` with JetStream-backed ack tracking.

**Files:**
- Create: `src/NATS.Server/Mqtt/MqttQoS1Tracker.cs`
- Modify: `src/NATS.Server/Mqtt/MqttRetainedStore.cs` (extend `MqttQoS2StateMachine`)
- Test: `tests/NATS.Server.Tests/Mqtt/MqttQoSTrackingTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: QoS 1 outgoing messages stored in `$MQTT_out`, removed on PUBACK, redelivered on reconnect. QoS 2 PUBREL delivery stream.

```bash
git commit -m "feat: add JetStream-backed QoS 1/2 tracking (Gap 6.3)"
```

---

### Task 47: MQTT MaxAckPending Enforcement (Gap 6.4)

Add `MqttFlowController` with per-subscription ack pending limits.

**Files:**
- Create: `src/NATS.Server/Mqtt/MqttFlowController.cs`
- Test: `tests/NATS.Server.Tests/Mqtt/MqttFlowControllerTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: `SemaphoreSlim`-based blocking at limit, release on PUBACK/PUBCOMP, config reload updates limits.

```bash
git commit -m "feat: add MQTT MaxAckPending flow control (Gap 6.4)"
```

---

### Task 48: MQTT Retained Message Delivery on Subscribe (Gap 6.5)

Deliver matching retained messages on SUBSCRIBE.

**Files:**
- Modify: `src/NATS.Server/Mqtt/MqttConnection.cs` (integrate retained delivery on SUB)
- Modify: `src/NATS.Server/Mqtt/MqttRetainedStore.cs:80` (`GetMatchingRetained`)
- Test: `tests/NATS.Server.Tests/Mqtt/MqttRetainedDeliveryTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: retained messages delivered on subscribe with Retain flag, wildcard subscriptions scan all retained topics.

```bash
git commit -m "feat: deliver retained messages on MQTT SUBSCRIBE (Gap 6.5)"
```

---

### Task 49: MQTT Session Flapper Detection (Gap 6.6)

Complete flapper detection with exponential backoff.

**Files:**
- Modify: `src/NATS.Server/Mqtt/MqttSessionStore.cs:122` (complete `TrackConnectDisconnect`)
- Test: `tests/NATS.Server.Tests/Mqtt/MqttFlapperDetectionTests.cs` (create)

**Step 1-5: TDD cycle**

Tests for: 3+ connect/disconnect cycles within 10s triggers flapper, exponential backoff on CONNACK, clear after 60s stable.

```bash
git commit -m "feat: complete MQTT session flapper detection (Gap 6.6)"
```

---

### Phase 4 Exit Gate

```bash
# Targeted tests
dotnet test tests/NATS.Server.Tests --filter "FullyQualifiedName~RouteResultCache|FullyQualifiedName~SlowConsumer|FullyQualifiedName~DynamicBuffer|FullyQualifiedName~ClientTrace|FullyQualifiedName~SubPermissionCache|FullyQualifiedName~ClientKind|FullyQualifiedName~AdaptiveReadBuffer|FullyQualifiedName~MqttWill|FullyQualifiedName~MqttQoS|FullyQualifiedName~MqttFlowController|FullyQualifiedName~MqttRetained|FullyQualifiedName~MqttFlapper" -v normal

# FULL TEST SUITE CHECKPOINT (Phase 4 complete)
dotnet test
```

Update test parity DB for all Phase 4 tests.

---

## Phase 5: Configuration Reload + Gateway (11 gaps)

**Dependencies:** Phase 4 (client protocol)
**Exit gate:** Auth changes propagated, TLS reloaded, cluster config hot-reloaded, gateways reconnect with backoff, account-specific routing works, queue groups propagated, reply mapping cached

---

### Task 50: Auth Change Propagation (Gap 14.2)

Add `PropagateAuthChanges` to `ConfigReloader`.

**Files:**
- Modify: `src/NATS.Server/Configuration/ConfigReloader.cs`
- Modify: `src/NATS.Server/NatsServer.cs` (hook auth changes to connections)
- Test: `tests/NATS.Server.Tests/Configuration/AuthChangePropagationTests.cs` (create)

```bash
git commit -m "feat: add auth change propagation to existing connections (Gap 14.2)"
```

---

### Task 51: TLS Certificate Reload (Gap 14.3)

Add `ReloadTlsCertificates` for hot-swapping certificates.

**Files:**
- Modify: `src/NATS.Server/Configuration/ConfigReloader.cs:496` (extend `ReloadTlsCertificate`)
- Test: `tests/NATS.Server.Tests/Configuration/TlsReloadTests.cs` (create)

```bash
git commit -m "feat: add TLS certificate hot-reload for new connections (Gap 14.3)"
```

---

### Task 52: Cluster Config Hot Reload (Gap 14.4)

Add `ApplyClusterConfigChanges` for route/gateway/leaf URL changes.

**Files:**
- Modify: `src/NATS.Server/Configuration/ConfigReloader.cs`
- Test: `tests/NATS.Server.Tests/Configuration/ClusterConfigReloadTests.cs` (create)

```bash
git commit -m "feat: add cluster config hot reload (Gap 14.4)"
```

---

### Task 53: Logging Level Changes (Gap 14.5)

Add `ApplyLoggingChanges` to update Serilog `LoggingLevelSwitch`.

**Files:**
- Modify: `src/NATS.Server/Configuration/ConfigReloader.cs`
- Test: `tests/NATS.Server.Tests/Configuration/LoggingReloadTests.cs` (create)

```bash
git commit -m "feat: add runtime logging level changes (Gap 14.5)"
```

---

### Task 54: JetStream Config Changes (Gap 14.6)

Add `ApplyJetStreamConfigChanges` for MaxMemory/MaxStore/Domain.

**Files:**
- Modify: `src/NATS.Server/Configuration/ConfigReloader.cs`
- Test: `tests/NATS.Server.Tests/Configuration/JetStreamConfigReloadTests.cs` (create)

```bash
git commit -m "feat: add JetStream config change reload (Gap 14.6)"
```

---

### Task 55: Gateway Reconnection with Backoff (Gap 11.2)

Add `ReconnectGatewayAsync` with exponential backoff and jitter.

**Files:**
- Modify: `src/NATS.Server/Gateways/GatewayManager.cs`
- Test: `tests/NATS.Server.Tests/Gateways/GatewayReconnectionTests.cs` (create)

```bash
git commit -m "feat: add gateway reconnection with exponential backoff (Gap 11.2)"
```

---

### Task 56: Account-Specific Gateway Routes (Gap 11.3)

Add per-account subscription sending to gateways.

**Files:**
- Modify: `src/NATS.Server/Gateways/GatewayManager.cs`
- Modify: `src/NATS.Server/Gateways/GatewayConnection.cs`
- Test: `tests/NATS.Server.Tests/Gateways/AccountGatewayRoutesTests.cs` (create)

```bash
git commit -m "feat: add account-specific gateway routes (Gap 11.3)"
```

---

### Task 57: Queue Group Propagation (Gap 11.4)

Add `SendQueueSubsToGateway` for queue group load balancing across gateways.

**Files:**
- Modify: `src/NATS.Server/Gateways/GatewayManager.cs`
- Modify: `src/NATS.Server/Gateways/GatewayConnection.cs`
- Test: `tests/NATS.Server.Tests/Gateways/QueueGroupPropagationTests.cs` (create)

```bash
git commit -m "feat: add queue group propagation to gateways (Gap 11.4)"
```

---

### Task 58: Reply Subject Mapping Cache (Gap 11.5)

Add `ReplyMapCache` with LRU and TTL expiration.

**Files:**
- Modify: `src/NATS.Server/Gateways/ReplyMapper.cs`
- Test: `tests/NATS.Server.Tests/Gateways/ReplyMapCacheTests.cs` (create)

```bash
git commit -m "feat: add reply subject mapping cache with TTL (Gap 11.5)"
```

---

### Task 59: Gateway Command Protocol (Gap 11.6)

Add `GatewayCommand` enum with exact Go wire format byte sequences.

**Files:**
- Modify: `src/NATS.Server/Gateways/GatewayManager.cs`
- Modify: `src/NATS.Server/Gateways/GatewayConnection.cs`
- Test: `tests/NATS.Server.Tests/Gateways/GatewayCommandTests.cs` (create)

```bash
git commit -m "feat: add gateway command protocol with Go-compatible wire format (Gap 11.6)"
```

---

### Task 60: Gateway Connection Registration (Gap 11.7)

Add full gateway connection registry with state tracking.

**Files:**
- Modify: `src/NATS.Server/Gateways/GatewayManager.cs`
- Test: `tests/NATS.Server.Tests/Gateways/GatewayRegistrationTests.cs` (create)

```bash
git commit -m "feat: add gateway connection registration with state tracking (Gap 11.7)"
```

---

### Phase 5 Exit Gate

```bash
dotnet test tests/NATS.Server.Tests --filter "FullyQualifiedName~AuthChangePropagation|FullyQualifiedName~TlsReload|FullyQualifiedName~ClusterConfigReload|FullyQualifiedName~LoggingReload|FullyQualifiedName~JetStreamConfigReload|FullyQualifiedName~GatewayReconnection|FullyQualifiedName~AccountGatewayRoutes|FullyQualifiedName~QueueGroupPropagation|FullyQualifiedName~ReplyMapCache|FullyQualifiedName~GatewayCommand|FullyQualifiedName~GatewayRegistration" -v normal
```

Update test parity DB for all Phase 5 tests.

---

## Phase 6: Route Clustering + LeafNode (12 gaps)

**Dependencies:** Phase 5 (config reload, gateway infrastructure)
**Exit gate:** Account-specific routes work, pool sizes negotiated, routes stored by hash, cluster splits handled, leaf TLS hot-reloads, permissions synced, leaf connections validated, WebSocket transport works

---

### Task 61: Account-Specific Dedicated Routes (Gap 13.2)

Add `AccountRouteMap` for per-account route connections.

**Files:**
- Modify: `src/NATS.Server/Routes/RouteManager.cs`
- Modify: `src/NATS.Server/Routes/RouteConnection.cs`
- Test: `tests/NATS.Server.Tests/Routes/AccountRouteTests.cs` (create)

```bash
git commit -m "feat: add account-specific dedicated routes (Gap 13.2)"
```

---

### Task 62: Route Pool Size Negotiation (Gap 13.3)

Add `NegotiatePoolSize` during route handshake.

**Files:**
- Modify: `src/NATS.Server/Routes/RouteManager.cs`
- Modify: `src/NATS.Server/Routes/RouteConnection.cs`
- Test: `tests/NATS.Server.Tests/Routes/PoolSizeNegotiationTests.cs` (create)

```bash
git commit -m "feat: add route pool size negotiation (Gap 13.3)"
```

---

### Task 63: Route Hash Storage (Gap 13.4)

Add `ConcurrentDictionary<ulong, RouteConnection>` for O(1) route lookup.

**Files:**
- Modify: `src/NATS.Server/Routes/RouteManager.cs`
- Test: `tests/NATS.Server.Tests/Routes/RouteHashStorageTests.cs` (create)

```bash
git commit -m "feat: add route hash storage for O(1) lookup (Gap 13.4)"
```

---

### Task 64: Cluster Split Handling (Gap 13.5)

Add `RemoveAllRoutesExcept` and `RemoveRoute` for partition handling.

**Files:**
- Modify: `src/NATS.Server/Routes/RouteManager.cs`
- Test: `tests/NATS.Server.Tests/Routes/ClusterSplitTests.cs` (create)

```bash
git commit -m "feat: add cluster split handling (Gap 13.5)"
```

---

### Task 65: No-Pool Route Fallback (Gap 13.6)

Add backward compatibility with pre-pool servers.

**Files:**
- Modify: `src/NATS.Server/Routes/RouteManager.cs`
- Modify: `src/NATS.Server/Routes/RouteConnection.cs`
- Test: `tests/NATS.Server.Tests/Routes/NoPoolFallbackTests.cs` (create)

```bash
git commit -m "feat: add no-pool route fallback for backward compatibility (Gap 13.6)"
```

---

### Task 66: Leaf Node TLS Certificate Hot-Reload (Gap 12.1)

Add `UpdateTlsConfig` for leaf node connections.

**Files:**
- Modify: `src/NATS.Server/LeafNodes/LeafNodeManager.cs`
- Test: `tests/NATS.Server.Tests/LeafNodes/LeafTlsReloadTests.cs` (create)

```bash
git commit -m "feat: add leaf node TLS certificate hot-reload (Gap 12.1)"
```

---

### Task 67: Permission & Account Syncing (Gap 12.2)

Add `SendPermsAndAccountInfo` and `InitLeafNodeSmapAndSendSubs`.

**Files:**
- Modify: `src/NATS.Server/LeafNodes/LeafNodeManager.cs`
- Modify: `src/NATS.Server/LeafNodes/LeafConnection.cs`
- Test: `tests/NATS.Server.Tests/LeafNodes/LeafPermissionSyncTests.cs` (create)

```bash
git commit -m "feat: add leaf node permission and account syncing (Gap 12.2)"
```

---

### Task 68: Leaf Connection State Validation (Gap 12.3)

Add `ValidateRemoteLeafNode` on reconnect.

**Files:**
- Modify: `src/NATS.Server/LeafNodes/LeafNodeManager.cs`
- Test: `tests/NATS.Server.Tests/LeafNodes/LeafValidationTests.cs` (create)

```bash
git commit -m "feat: add leaf connection state validation on reconnect (Gap 12.3)"
```

---

### Task 69: JetStream Migration Checks (Gap 12.4)

Add `CheckJetStreamMigrate` validation.

**Files:**
- Modify: `src/NATS.Server/LeafNodes/LeafNodeManager.cs`
- Test: `tests/NATS.Server.Tests/LeafNodes/LeafJetStreamMigrationTests.cs` (create)

```bash
git commit -m "feat: add leaf node JetStream migration checks (Gap 12.4)"
```

---

### Task 70: Leaf Node WebSocket Support (Gap 12.5)

Add `WebSocketStreamAdapter` for message-framed WebSocket → stream conversion.

**Files:**
- Create: `src/NATS.Server/LeafNodes/WebSocketStreamAdapter.cs`
- Modify: `src/NATS.Server/LeafNodes/LeafConnection.cs`
- Test: `tests/NATS.Server.Tests/LeafNodes/LeafWebSocketTests.cs` (create)

```bash
git commit -m "feat: add leaf node WebSocket support with stream adapter (Gap 12.5)"
```

---

### Task 71: Leaf Cluster Registration (Gap 12.6)

Add `RegisterLeafNodeCluster` and `HasLeafNodeCluster`.

**Files:**
- Modify: `src/NATS.Server/LeafNodes/LeafNodeManager.cs`
- Test: `tests/NATS.Server.Tests/LeafNodes/LeafClusterRegistrationTests.cs` (create)

```bash
git commit -m "feat: add leaf cluster registration and topology tracking (Gap 12.6)"
```

---

### Task 72: Leaf Connection Disable Flag (Gap 12.7)

Add `IsLeafConnectDisabled` with per-remote disable flag.

**Files:**
- Modify: `src/NATS.Server/LeafNodes/LeafNodeManager.cs`
- Test: `tests/NATS.Server.Tests/LeafNodes/LeafDisableTests.cs` (create)

```bash
git commit -m "feat: add leaf connection disable flag (Gap 12.7)"
```

---

### Phase 6 Exit Gate

```bash
# Targeted tests
dotnet test tests/NATS.Server.Tests --filter "FullyQualifiedName~AccountRoute|FullyQualifiedName~PoolSizeNegotiation|FullyQualifiedName~RouteHash|FullyQualifiedName~ClusterSplit|FullyQualifiedName~NoPoolFallback|FullyQualifiedName~LeafTlsReload|FullyQualifiedName~LeafPermissionSync|FullyQualifiedName~LeafValidation|FullyQualifiedName~LeafJetStreamMigration|FullyQualifiedName~LeafWebSocket|FullyQualifiedName~LeafClusterRegistration|FullyQualifiedName~LeafDisable" -v normal

# FULL TEST SUITE CHECKPOINT (Phase 6 complete)
dotnet test
```

Update test parity DB for all Phase 6 tests.

---

## Phase 7: Account Management & Multi-Tenancy (10 gaps)

**Dependencies:** Phase 4 (client protocol), Phase 5 (config reload), Phase 6 (leaf/route for claim propagation)
**Exit gate:** Service latency tracked, response thresholds enforced, import cycles detected, wildcard exports work, accounts expire, claims hot-reloaded, NKey revocation enforced

---

### Task 73: Service Export Latency Tracking (Gap 9.1)

Add `ServiceLatencyTracker` with p50/p90/p99 histogram.

**Files:**
- Create: `src/NATS.Server/Auth/ServiceLatencyTracker.cs`
- Modify: `src/NATS.Server/Auth/Account.cs`
- Test: `tests/NATS.Server.Tests/Auth/ServiceLatencyTrackerTests.cs` (create)

```bash
git commit -m "feat: add service export latency tracking with p50/p90/p99 (Gap 9.1)"
```

---

### Task 74: Service Export Response Threshold (Gap 9.2)

Add `ResponseThreshold` to service export configuration.

**Files:**
- Modify: `src/NATS.Server/Auth/Account.cs`
- Test: `tests/NATS.Server.Tests/Auth/ResponseThresholdTests.cs` (create)

```bash
git commit -m "feat: add service export response threshold enforcement (Gap 9.2)"
```

---

### Task 75: Stream Import Cycle Detection (Gap 9.3)

Add `StreamImportFormsCycle` using DFS.

**Files:**
- Modify: `src/NATS.Server/Auth/Account.cs`
- Test: `tests/NATS.Server.Tests/Auth/StreamImportCycleTests.cs` (create)

```bash
git commit -m "feat: add stream import cycle detection (Gap 9.3)"
```

---

### Task 76: Wildcard Service Exports (Gap 9.4)

Add `GetWildcardServiceExport` using `SubjectMatch.IsMatch`.

**Files:**
- Modify: `src/NATS.Server/Auth/Account.cs`
- Test: `tests/NATS.Server.Tests/Auth/WildcardExportTests.cs` (create)

```bash
git commit -m "feat: add wildcard service export matching (Gap 9.4)"
```

---

### Task 77: Account Expiration & TTL (Gap 9.5)

Add `ExpiresAt`, `IsExpired`, and `SetExpirationTimer`.

**Files:**
- Modify: `src/NATS.Server/Auth/Account.cs`
- Test: `tests/NATS.Server.Tests/Auth/AccountExpirationTests.cs` (create)

```bash
git commit -m "feat: add account expiration with TTL-based cleanup (Gap 9.5)"
```

---

### Task 78: Account Claim Hot-Reload (Gap 9.6)

Add `UpdateAccountClaims` with diff-based update.

**Files:**
- Modify: `src/NATS.Server/Auth/Account.cs`
- Modify: `src/NATS.Server/NatsServer.cs`
- Test: `tests/NATS.Server.Tests/Auth/AccountClaimReloadTests.cs` (create)

```bash
git commit -m "feat: add account claim hot-reload with diff-based update (Gap 9.6)"
```

---

### Task 79: Service/Stream Activation Expiration (Gap 9.7)

Add `CheckActivationExpiry` for JWT activation claims.

**Files:**
- Modify: `src/NATS.Server/Auth/Account.cs`
- Test: `tests/NATS.Server.Tests/Auth/ActivationExpirationTests.cs` (create)

```bash
git commit -m "feat: add JWT activation claim expiration checking (Gap 9.7)"
```

---

### Task 80: User NKey Revocation (Gap 9.8)

Wire `_revokedUsers` into active connection validation.

**Files:**
- Modify: `src/NATS.Server/Auth/Account.cs:38` (extend `IsUserRevoked`)
- Modify: `src/NATS.Server/NatsClient.cs` (check revocation on operations)
- Test: `tests/NATS.Server.Tests/Auth/NKeyRevocationTests.cs` (create)

```bash
git commit -m "feat: wire user NKey revocation into active connections (Gap 9.8)"
```

---

### Task 81: Response Service Import (Gap 9.9)

Add `AddReverseRespMapEntry` and `CheckForReverseEntries`.

**Files:**
- Modify: `src/NATS.Server/Auth/Account.cs`
- Test: `tests/NATS.Server.Tests/Auth/ReverseResponseMapTests.cs` (create)

```bash
git commit -m "feat: add reverse response mapping for cross-account request-reply (Gap 9.9)"
```

---

### Task 82: Service Import Shadowing Detection (Gap 9.10)

Add `ServiceImportShadowed` checking for local subscription overlap.

**Files:**
- Modify: `src/NATS.Server/Auth/Account.cs`
- Test: `tests/NATS.Server.Tests/Auth/ImportShadowingTests.cs` (create)

```bash
git commit -m "feat: add service import shadowing detection (Gap 9.10)"
```

---

### Phase 7 Exit Gate

```bash
dotnet test tests/NATS.Server.Tests --filter "FullyQualifiedName~ServiceLatency|FullyQualifiedName~ResponseThreshold|FullyQualifiedName~StreamImportCycle|FullyQualifiedName~WildcardExport|FullyQualifiedName~AccountExpiration|FullyQualifiedName~AccountClaimReload|FullyQualifiedName~ActivationExpiration|FullyQualifiedName~NKeyRevocation|FullyQualifiedName~ReverseResponseMap|FullyQualifiedName~ImportShadowing" -v normal
```

Update test parity DB for all Phase 7 tests.

---

## Phase 8: Monitoring, Events & WebSocket (11 gaps)

**Dependencies:** Phase 7 (account management)
**Exit gate:** Closed connections queryable, account filtering works, sort options work, auth events published, trace propagated, event payloads complete, WebSocket TLS configured

---

### Task 83: Closed Connections Ring Buffer (Gap 10.1)

Add `ClosedConnectionRingBuffer` and wire into `ConnzHandler`.

**Files:**
- Create: `src/NATS.Server/Monitoring/ClosedConnectionRingBuffer.cs`
- Modify: `src/NATS.Server/NatsServer.cs` (record closed connections)
- Modify: `src/NATS.Server/Monitoring/ConnzHandler.cs:12` (support `state=closed`)
- Test: `tests/NATS.Server.Tests/Monitoring/ClosedConnectionRingBufferTests.cs` (create)

```bash
git commit -m "feat: add closed connection ring buffer for /connz?state=closed (Gap 10.1)"
```

---

### Task 84: Account-Scoped Filtering (Gap 10.2)

Add `acc` query parameter to `ConnzHandler`.

**Files:**
- Modify: `src/NATS.Server/Monitoring/ConnzHandler.cs:239` (add `acc` param parsing)
- Test: `tests/NATS.Server.Tests/Monitoring/ConnzAccountFilterTests.cs` (create)

```bash
git commit -m "feat: add account-scoped filtering to /connz (Gap 10.2)"
```

---

### Task 85: Sort Options (Gap 10.3)

Add `SortBy` enum and sort query parameter to `ConnzHandler`.

**Files:**
- Modify: `src/NATS.Server/Monitoring/ConnzHandler.cs`
- Test: `tests/NATS.Server.Tests/Monitoring/ConnzSortTests.cs` (create)

```bash
git commit -m "feat: add sort options to /connz (Gap 10.3)"
```

---

### Task 86: Message Trace Propagation (Gap 10.4)

Add trace context header propagation across servers.

**Files:**
- Modify: `src/NATS.Server/Internal/MessageTraceContext.cs`
- Modify: `src/NATS.Server/Events/InternalEventSystem.cs`
- Test: `tests/NATS.Server.Tests/Internal/TraceContextPropagationTests.cs` (create)

```bash
git commit -m "feat: add message trace propagation across servers (Gap 10.4)"
```

---

### Task 87: Auth Error Events (Gap 10.5)

Add `SendAuthErrorEvent` publishing to `$SYS.SERVER.{id}.CLIENT.AUTH.ERR`.

**Files:**
- Modify: `src/NATS.Server/NatsServer.cs`
- Modify: `src/NATS.Server/Events/InternalEventSystem.cs`
- Test: `tests/NATS.Server.Tests/Events/AuthErrorEventTests.cs` (create)

```bash
git commit -m "feat: add auth error event publication (Gap 10.5)"
```

---

### Task 88: Full System Event Payloads (Gap 10.6)

Audit and complete all event type fields.

**Files:**
- Modify: `src/NATS.Server/Events/EventTypes.cs`
- Modify: `src/NATS.Server/Events/InternalEventSystem.cs`
- Test: `tests/NATS.Server.Tests/Events/FullEventPayloadTests.cs` (create)

```bash
git commit -m "feat: complete system event payload fields (Gap 10.6)"
```

---

### Task 89: Closed Connection Reason Tracking (Gap 10.7)

Populate `ClosedClient.Reason` consistently across all disconnect paths.

**Files:**
- Modify: `src/NATS.Server/NatsClient.cs:902` (`MarkClosed` — ensure reason set)
- Modify: `src/NATS.Server/NatsServer.cs`
- Test: `tests/NATS.Server.Tests/Monitoring/ClosedReasonTests.cs` (create)

```bash
git commit -m "feat: consistently populate closed connection reasons (Gap 10.7)"
```

---

### Task 90: Remote Server Events (Gap 10.8)

Add `RemoteServerShutdown`, `RemoteServerUpdate`, `LeafNodeConnected` events.

**Files:**
- Modify: `src/NATS.Server/NatsServer.cs`
- Modify: `src/NATS.Server/Events/InternalEventSystem.cs`
- Modify: `src/NATS.Server/Events/EventSubjects.cs`
- Test: `tests/NATS.Server.Tests/Events/RemoteServerEventTests.cs` (create)

```bash
git commit -m "feat: add remote server events for cluster visibility (Gap 10.8)"
```

---

### Task 91: Event Compression (Gap 10.9)

Add S2 compression for system events when subscriber supports it.

**Files:**
- Modify: `src/NATS.Server/Events/InternalEventSystem.cs`
- Test: `tests/NATS.Server.Tests/Events/EventCompressionTests.cs` (create)

```bash
git commit -m "feat: add S2 compression for system events (Gap 10.9)"
```

---

### Task 92: OCSP Peer Events (Gap 10.10)

Add OCSP peer reject and chain validation events.

**Files:**
- Modify: `src/NATS.Server/NatsServer.cs`
- Modify: `src/NATS.Server/Events/InternalEventSystem.cs`
- Test: `tests/NATS.Server.Tests/Events/OcspEventTests.cs` (create)

```bash
git commit -m "feat: add OCSP peer reject and chain validation events (Gap 10.10)"
```

---

### Task 93: WebSocket-Specific TLS (Gap 15.1)

Add separate TLS configuration for WebSocket listener.

**Files:**
- Modify: `src/NATS.Server/WebSocket/WsUpgrade.cs`
- Modify: `src/NATS.Server/NatsServer.cs`
- Test: `tests/NATS.Server.Tests/WebSocket/WebSocketTlsTests.cs` (create)

```bash
git commit -m "feat: add WebSocket-specific TLS configuration (Gap 15.1)"
```

---

### Phase 8 Exit Gate

```bash
# Targeted tests
dotnet test tests/NATS.Server.Tests --filter "FullyQualifiedName~ClosedConnectionRingBuffer|FullyQualifiedName~ConnzAccountFilter|FullyQualifiedName~ConnzSort|FullyQualifiedName~TraceContextPropagation|FullyQualifiedName~AuthErrorEvent|FullyQualifiedName~FullEventPayload|FullyQualifiedName~ClosedReason|FullyQualifiedName~RemoteServerEvent|FullyQualifiedName~EventCompression|FullyQualifiedName~OcspEvent|FullyQualifiedName~WebSocketTls" -v normal

# FULL TEST SUITE CHECKPOINT (Phase 8 complete — FINAL)
dotnet test
```

Update test parity DB for all Phase 8 tests.

---

## Post-Implementation

After all 8 phases:

1. **Update `docs/structuregaps.md`** — mark all 93 gaps as IMPLEMENTED with commit references
2. **Final test parity DB update** — ensure all new tests are registered
3. **Commit final updates**

```bash
git add docs/structuregaps.md docs/test_parity.db
git commit -m "docs: mark all 93 remaining gaps as IMPLEMENTED"
```