Phase 4g: DateTimeOffset timestamps + PermissionRequestResult.Feedback

- Add UnixMillisecondsDateTimeOffsetConverter for unix-millis-as-JSON-number
  timestamps
- Convert long Timestamp fields on hook *Input* types and PingResponse to
  DateTimeOffset via the new converter
- Convert SessionLifecycleEventMetadata.StartTime/ModifiedTime from ISO 8601
  strings to DateTimeOffset
- Convert SessionMetadata.StartTime/ModifiedTime from DateTime to DateTimeOffset
- Add PermissionRequestResult.Feedback property (parity with the RPC
  PermissionDecisionReject type's feedback field); forward to the wire only
  on reject decisions
- Tidy XML doc on PermissionRequestResult.Kind to reference the well-known
  PermissionRequestResultKind static members directly

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: SteveSandersonMS

dotnet/src/Session.cs

@@ -755,7 +755,10 @@ private async Task ExecutePermissionAndRespondAsync(string requestId, Permission
                 return;
             }
             var responseRpcTimestamp = Stopwatch.GetTimestamp();
-            await Rpc.Permissions.HandlePendingPermissionRequestAsync(requestId, new PermissionDecision { Kind = result.Kind.Value });
+            PermissionDecision decision = result.Kind == PermissionRequestResultKind.Rejected
+                ? new PermissionDecisionReject { Feedback = result.Feedback }
+                : new PermissionDecision { Kind = result.Kind.Value };
+            await Rpc.Permissions.HandlePendingPermissionRequestAsync(requestId, decision);
             LoggingHelpers.LogTiming(_logger, LogLevel.Debug, null,
                 "CopilotSession.ExecutePermissionAndRespondAsync response sent successfully. Elapsed={Elapsed}, SessionId={SessionId}, RequestId={RequestId}",
                 responseRpcTimestamp,

dotnet/src/Types.cs

@@ -689,13 +689,13 @@ public override void Write(Utf8JsonWriter writer, PermissionRequestResultKind va
 public sealed class PermissionRequestResult
 {
     /// <summary>
-    /// Permission decision kind. Use the static members of <see cref="PermissionRequestResultKind"/>
-    /// to construct values. Valid kinds are:
+    /// Permission decision kind. Construct values with the static members on
+    /// <see cref="PermissionRequestResultKind"/>:
     /// <list type="bullet">
-    /// <item><description><c>"approve-once"</c> (<see cref="PermissionRequestResultKind.Approved"/>) — allow this single request.</description></item>
-    /// <item><description><c>"reject"</c> (<see cref="PermissionRequestResultKind.Rejected"/>) — deny the request.</description></item>
-    /// <item><description><c>"user-not-available"</c> (<see cref="PermissionRequestResultKind.UserNotAvailable"/>) — deny because no user is available to confirm.</description></item>
-    /// <item><description><c>"no-result"</c> (<see cref="PermissionRequestResultKind.NoResult"/>) — leave the pending request unanswered (protocol v1 only; rejected by protocol v2 servers).</description></item>
+    /// <item><description><see cref="PermissionRequestResultKind.Approved"/> — allow this single request.</description></item>
+    /// <item><description><see cref="PermissionRequestResultKind.Rejected"/> — deny the request.</description></item>
+    /// <item><description><see cref="PermissionRequestResultKind.UserNotAvailable"/> — deny because no user is available to confirm.</description></item>
+    /// <item><description><see cref="PermissionRequestResultKind.NoResult"/> — leave the pending request unanswered (protocol v1 only; rejected by protocol v2 servers).</description></item>
     /// </list>
     /// </summary>
     [JsonPropertyName("kind")]
@@ -706,6 +706,14 @@ public sealed class PermissionRequestResult
     /// </summary>
     [JsonPropertyName("rules")]
     public IList<object>? Rules { get; set; }
+
+    /// <summary>
+    /// Optional human-readable feedback to forward to the LLM along with the
+    /// decision. Mirrors the <c>feedback</c> field on the RPC-level
+    /// <see cref="Rpc.PermissionDecision"/> type.
+    /// </summary>
+    [JsonPropertyName("feedback")]
+    public string? Feedback { get; set; }
 }
 
 /// <summary>
@@ -1167,7 +1175,8 @@ public sealed class PreToolUseHookInput
     /// Unix timestamp in milliseconds when the tool use was initiated.
     /// </summary>
     [JsonPropertyName("timestamp")]
-    public long Timestamp { get; set; }
+    [JsonConverter(typeof(UnixMillisecondsDateTimeOffsetConverter))]
+    public DateTimeOffset Timestamp { get; set; }
 
     /// <summary>
     /// Current working directory of the session.
@@ -1249,7 +1258,8 @@ public sealed class PostToolUseHookInput
     /// Unix timestamp in milliseconds when the tool execution completed.
     /// </summary>
     [JsonPropertyName("timestamp")]
-    public long Timestamp { get; set; }
+    [JsonConverter(typeof(UnixMillisecondsDateTimeOffsetConverter))]
+    public DateTimeOffset Timestamp { get; set; }
 
     /// <summary>
     /// Current working directory of the session.
@@ -1320,7 +1330,8 @@ public sealed class UserPromptSubmittedHookInput
     /// Unix timestamp in milliseconds when the prompt was submitted.
     /// </summary>
     [JsonPropertyName("timestamp")]
-    public long Timestamp { get; set; }
+    [JsonConverter(typeof(UnixMillisecondsDateTimeOffsetConverter))]
+    public DateTimeOffset Timestamp { get; set; }
 
     /// <summary>
     /// Current working directory of the session.
@@ -1379,7 +1390,8 @@ public sealed class SessionStartHookInput
     /// Unix timestamp in milliseconds when the session started.
     /// </summary>
     [JsonPropertyName("timestamp")]
-    public long Timestamp { get; set; }
+    [JsonConverter(typeof(UnixMillisecondsDateTimeOffsetConverter))]
+    public DateTimeOffset Timestamp { get; set; }
 
     /// <summary>
     /// Current working directory of the session.
@@ -1443,7 +1455,8 @@ public sealed class SessionEndHookInput
     /// Unix timestamp in milliseconds when the session ended.
     /// </summary>
     [JsonPropertyName("timestamp")]
-    public long Timestamp { get; set; }
+    [JsonConverter(typeof(UnixMillisecondsDateTimeOffsetConverter))]
+    public DateTimeOffset Timestamp { get; set; }
 
     /// <summary>
     /// Current working directory of the session.
@@ -1521,7 +1534,8 @@ public sealed class ErrorOccurredHookInput
     /// Unix timestamp in milliseconds when the error occurred.
     /// </summary>
     [JsonPropertyName("timestamp")]
-    public long Timestamp { get; set; }
+    [JsonConverter(typeof(UnixMillisecondsDateTimeOffsetConverter))]
+    public DateTimeOffset Timestamp { get; set; }
 
     /// <summary>
     /// Current working directory of the session.
@@ -2831,11 +2845,11 @@ public sealed class SessionMetadata
     /// <summary>
     /// Time when the session was created.
     /// </summary>
-    public DateTime StartTime { get; set; }
+    public DateTimeOffset StartTime { get; set; }
     /// <summary>
     /// Time when the session was last modified.
     /// </summary>
-    public DateTime ModifiedTime { get; set; }
+    public DateTimeOffset ModifiedTime { get; set; }
     /// <summary>
     /// Human-readable summary of the session.
     /// </summary>
@@ -3092,16 +3106,16 @@ public sealed class GetModelsResponse
 public sealed class SessionLifecycleEventMetadata
 {
     /// <summary>
-    /// ISO 8601 timestamp when the session was created.
+    /// Timestamp when the session was created.
     /// </summary>
     [JsonPropertyName("startTime")]
-    public string StartTime { get; set; } = string.Empty;
+    public DateTimeOffset StartTime { get; set; }
 
     /// <summary>
-    /// ISO 8601 timestamp when the session was last modified.
+    /// Timestamp when the session was last modified.
     /// </summary>
     [JsonPropertyName("modifiedTime")]
-    public string ModifiedTime { get; set; } = string.Empty;
+    public DateTimeOffset ModifiedTime { get; set; }
 
     /// <summary>
     /// Human-readable summary of the session.

dotnet/src/UnixMillisecondsDateTimeOffsetConverter.cs

@@ -0,0 +1,22 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *--------------------------------------------------------------------------------------------*/
+
+using System.ComponentModel;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace GitHub.Copilot.SDK;
+
+/// <summary>Converts between JSON numeric milliseconds-since-Unix-epoch and <see cref="DateTimeOffset"/>.</summary>
+[EditorBrowsable(EditorBrowsableState.Never)]
+public sealed class UnixMillisecondsDateTimeOffsetConverter : JsonConverter<DateTimeOffset>
+{
+    /// <inheritdoc />
+    public override DateTimeOffset Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options) =>
+        DateTimeOffset.FromUnixTimeMilliseconds(reader.GetInt64());
+
+    /// <inheritdoc />
+    public override void Write(Utf8JsonWriter writer, DateTimeOffset value, JsonSerializerOptions options) =>
+        writer.WriteNumberValue(value.ToUnixTimeMilliseconds());
+}

dotnet/test/E2E/HookLifecycleAndOutputE2ETests.cs

@@ -43,7 +43,7 @@ public async Task Should_Invoke_OnSessionStart_Hook_On_New_Session()
 
         Assert.NotEmpty(sessionStartInputs);
         Assert.Equal("new", sessionStartInputs[0].Source);
-        Assert.True(sessionStartInputs[0].Timestamp > 0);
+        Assert.True(sessionStartInputs[0].Timestamp > DateTimeOffset.UnixEpoch);
         Assert.False(string.IsNullOrEmpty(sessionStartInputs[0].Cwd));
 
         await session.DisposeAsync();
@@ -71,7 +71,7 @@ public async Task Should_Invoke_OnUserPromptSubmitted_Hook_When_Sending_A_Messag
 
         Assert.NotEmpty(userPromptInputs);
         Assert.Contains("Say hello", userPromptInputs[0].Prompt);
-        Assert.True(userPromptInputs[0].Timestamp > 0);
+        Assert.True(userPromptInputs[0].Timestamp > DateTimeOffset.UnixEpoch);
         Assert.False(string.IsNullOrEmpty(userPromptInputs[0].Cwd));
 
         await session.DisposeAsync();
@@ -116,7 +116,7 @@ public async Task Should_Invoke_OnErrorOccurred_Hook_When_Error_Occurs()
                 OnErrorOccurred = (input, invocation) =>
                 {
                     Assert.Equal(session!.SessionId, invocation.SessionId);
-                    Assert.True(input.Timestamp > 0);
+                    Assert.True(input.Timestamp > DateTimeOffset.UnixEpoch);
                     Assert.False(string.IsNullOrEmpty(input.Cwd));
                     Assert.False(string.IsNullOrEmpty(input.Error));
                     Assert.Contains(input.ErrorContext, ValidErrorContexts);