3 files changed, 149 insertions, 32 deletions
diff --git a/src/Agent.App/Logging/McpHostLogObserver.cs b/src/Agent.App/Logging/McpHostLogObserver.cs
new file mode 100644
index 0000000..b1410e8
--- /dev/null
+++ b/src/Agent.App/Logging/McpHostLogObserver.cs
@@ -0,0 +1,76 @@
+using System.Globalization;
+using System.Text.Json;
+using Agent.Core.Localization;
+using Agent.Mcp;
+using System.Collections.Concurrent;
+
+namespace Agent.App.Logging;
+
+public sealed class McpHostLogObserver : IMcpHostObserver, IDisposable
+{
+    private readonly RollingFileLog _application;
+    private readonly RollingFileWriter? _http;
+    private readonly LocaleCatalog _locale;
+    private readonly string _logDirectory;
+    private readonly ConcurrentDictionary<string, byte> _observedConnections = new(StringComparer.Ordinal);
+
+    public McpHostLogObserver(RollingFileLog application, LocaleCatalog locale, string logDirectory,
+        bool httpRequests, long maxBytes, int retainedFiles)
+    {
+        _application = application;
+        _locale = locale;
+        _logDirectory = logDirectory;
+        if (httpRequests) _http = new RollingFileWriter(Path.Combine(logDirectory, "http.jsonl"), maxBytes, retainedFiles);
+    }
+
+    public void Ready(McpReadyInfo info)
+    {
+        string message = info.Transport == "http"
+            ? _locale.Format("app.ready.http", new Dictionary<string, object?>
+            {
+                ["endpoint"] = info.Endpoint, ["protocol"] = info.ProtocolVersion, ["stateless"] = info.Stateless.ToString().ToLowerInvariant(),
+                ["fallback"] = info.LegacyFallback.ToString().ToLowerInvariant(), ["pid"] = info.ProcessId, ["logs"] = _logDirectory
+            })
+            : _locale.Format("app.ready.stdio", new Dictionary<string, object?>
+            {
+                ["protocol"] = info.ProtocolVersion, ["pid"] = info.ProcessId, ["logs"] = _logDirectory
+            });
+        _application.Operational(message);
+    }
+
+    public void HttpRequestStarted(McpHttpRequestStartInfo info)
+    {
+        if (_observedConnections.TryAdd(info.ConnectionId, 0))
+            _application.Information($"HTTP connection observed connection={info.ConnectionId} remote={info.RemoteIp}:{info.RemotePort}");
+        _application.Information($"HTTP request started connection={info.ConnectionId} trace={info.TraceId} remote={info.RemoteIp}:{info.RemotePort} method={info.Method} path={info.Path}");
+    }
+
+    public void HttpRequest(McpHttpRequestInfo info)
+    {
+        _application.Information(string.Create(CultureInfo.InvariantCulture,
+            $"HTTP request completed connection={info.ConnectionId} remote={info.RemoteIp}:{info.RemotePort} method={info.Method} path={info.Path} status={info.Status} duration_ms={info.DurationMs:F3}"));
+        _http?.WriteLine(JsonSerializer.Serialize(new
+        {
+            timestamp = info.Timestamp,
+            connection_id = info.ConnectionId,
+            trace_id = info.TraceId,
+            remote_ip = info.RemoteIp,
+            remote_port = info.RemotePort,
+            local_ip = info.LocalIp,
+            local_port = info.LocalPort,
+            method = info.Method,
+            path = info.Path,
+            status = info.Status,
+            duration_ms = info.DurationMs,
+            content_type = info.ContentType,
+            content_length = info.ContentLength,
+            user_agent = info.UserAgent,
+            mcp_protocol_version = NullIfEmpty(info.ProtocolVersion),
+            mcp_method = NullIfEmpty(info.McpMethod),
+            mcp_name = NullIfEmpty(info.McpName)
+        }));
+    }
+
+    private static string? NullIfEmpty(string? value) => string.IsNullOrWhiteSpace(value) ? null : value;
+    public void Dispose() => _http?.Dispose();
+}
diff --git a/src/Agent.App/Logging/RollingFileLog.cs b/src/Agent.App/Logging/RollingFileLog.cs
index 801768d..8bdbbb4 100644
--- a/src/Agent.App/Logging/RollingFileLog.cs
+++ b/src/Agent.App/Logging/RollingFileLog.cs
@@ -4,52 +4,43 @@ namespace Agent.App.Logging;
 
 public sealed class RollingFileLog : IDisposable
 {
-    private readonly object _sync = new();
-    private readonly string _path;
-    private readonly long _maxBytes;
-    private readonly int _retainedFiles;
-    private StreamWriter _writer;
+    private readonly RollingFileWriter _writer;
+    private readonly int _minimumLevel;
 
-    public RollingFileLog(string directory, long maxBytes, int retainedFiles)
+    public RollingFileLog(string directory, long maxBytes, int retainedFiles, string minimumLevel = "information")
     {
         Directory.CreateDirectory(directory);
-        _path = Path.Combine(directory, "application.log");
-        _maxBytes = maxBytes;
-        _retainedFiles = retainedFiles;
-        _writer = Open();
+        _writer = new RollingFileWriter(Path.Combine(directory, "application.log"), maxBytes, retainedFiles);
+        _minimumLevel = ParseLevel(minimumLevel);
     }
 
     public void Information(string message) => Write("INF", message);
+    public void Operational(string message) => Write("INF", message, force: true);
+    public void Warning(string message) => Write("WRN", message);
     public void Error(string message) => Write("ERR", message);
+    public void Fatal(string message) => Write("FTL", message);
 
-    private void Write(string level, string message)
+    private void Write(string level, string message, bool force = false)
     {
-        lock (_sync)
-        {
-            if (_writer.BaseStream.Length >= _maxBytes) Rotate();
-            string line = string.Create(CultureInfo.InvariantCulture, $"{DateTimeOffset.UtcNow:O} [{level}] {message}");
-            Console.Error.WriteLine(line);
-            _writer.WriteLine(line);
-            _writer.Flush();
-        }
+        if (!force && Level(level) < _minimumLevel) return;
+        string line = string.Create(CultureInfo.InvariantCulture, $"{DateTimeOffset.UtcNow:O} [{level}] {message}");
+        Console.Error.WriteLine(line);
+        _writer.WriteLine(line);
     }
 
-    private StreamWriter Open() => new(new FileStream(_path, FileMode.Append, FileAccess.Write, FileShare.Read), new System.Text.UTF8Encoding(false));
-
-    private void Rotate()
+    private static int ParseLevel(string level) => level.ToLowerInvariant() switch
     {
-        _writer.Dispose();
-        for (int index = _retainedFiles - 1; index >= 1; index--)
-        {
-            string source = $"{_path}.{index}";
-            if (File.Exists(source)) File.Move(source, $"{_path}.{index + 1}", true);
-        }
-        if (File.Exists(_path)) File.Move(_path, $"{_path}.1", true);
-        _writer = Open();
-    }
+        "information" or "info" => 0,
+        "warning" or "warn" => 1,
+        "error" => 2,
+        "fatal" => 3,
+        _ => throw new ArgumentException($"Unknown logging level '{level}'.", nameof(level))
+    };
+
+    private static int Level(string level) => level switch { "INF" => 0, "WRN" => 1, "ERR" => 2, "FTL" => 3, _ => 0 };
 
     public void Dispose()
     {
-        lock (_sync) _writer.Dispose();
+        _writer.Dispose();
     }
 }
diff --git a/src/Agent.App/Logging/RollingFileWriter.cs b/src/Agent.App/Logging/RollingFileWriter.cs
new file mode 100644
index 0000000..e155858
--- /dev/null
+++ b/src/Agent.App/Logging/RollingFileWriter.cs
@@ -0,0 +1,50 @@
+using System.Text;
+
+namespace Agent.App.Logging;
+
+internal sealed class RollingFileWriter : IDisposable
+{
+    private readonly object _sync = new();
+    private readonly string _path;
+    private readonly long _maxBytes;
+    private readonly int _retainedFiles;
+    private StreamWriter _writer;
+
+    public RollingFileWriter(string path, long maxBytes, int retainedFiles)
+    {
+        _path = path;
+        _maxBytes = maxBytes;
+        _retainedFiles = retainedFiles;
+        Directory.CreateDirectory(Path.GetDirectoryName(path)!);
+        _writer = Open();
+    }
+
+    public void WriteLine(string line)
+    {
+        lock (_sync)
+        {
+            if (_writer.BaseStream.Length >= _maxBytes) Rotate();
+            _writer.WriteLine(line);
+            _writer.Flush();
+        }
+    }
+
+    private StreamWriter Open() => new(new FileStream(_path, FileMode.Append, FileAccess.Write, FileShare.Read), new UTF8Encoding(false));
+
+    private void Rotate()
+    {
+        _writer.Dispose();
+        for (int index = _retainedFiles - 1; index >= 1; index--)
+        {
+            string source = $"{_path}.{index}";
+            if (File.Exists(source)) File.Move(source, $"{_path}.{index + 1}", true);
+        }
+        if (File.Exists(_path)) File.Move(_path, $"{_path}.1", true);
+        _writer = Open();
+    }
+
+    public void Dispose()
+    {
+        lock (_sync) _writer.Dispose();
+    }
+}