M3: what each handler did with an activity

Arrival carries a verdict that handlers set with one line before an existing return
(Arrival.Drop, Reject, Accept, About), so no handler signature changes. InboxProcessor
records it as an 'in' event, with the time taken, the wait since the inbox accepted it, the
attempt, the audience (from the post's visibility, or else the activity's addressing), the
local actor kind, the object's age for updates, deletes and reactions, and the FEP features
of a delivered object. It also records types nothing handles (unknown-type), actors that
cannot be loaded (deferred) and handler failures.

Drop reasons: fetch-failed, unparseable, misattributed, duplicate, deleted, not-addressed,
not-followed, not-public, not-visible, not-deleted, unknown-object, unknown-recipient,
cross-origin, unsupported. Accepted sub-reasons: stored, poll-vote, edit, refresh,
actor-refresh, actor-delete, removed, tombstone-only, auto-accepted, pending,
follow-answer, quote-answer, quote-granted, undone, reaction, reported. Rejected: blocked,
ignored, quote-refused.

A circle's traffic is private and kindless, and a stranger posting into one is just
not-addressed, so the event store cannot reveal a circle.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ELjqpznMFMNrJoJUj6K5p2

PrivaPub/Domain/Social/Reactions.cs

@@ -2,6 +2,7 @@ using MongoDB.Driver;
 using MongoDB.Entities;
 
 using PrivaPub.Federation.Actors;
+using PrivaPub.Federation.Inbox;
 using PrivaPub.Federation.Inbox.Handlers;
 using PrivaPub.Federation.Objects;
 using PrivaPub.Federation.Outbox;
@@ -43,7 +44,10 @@ namespace PrivaPub.Domain.Social
 		public async Task Receive(PostEntity post, ForeignAvatar actor, string content, JsonNode tags, string activityId, CancellationToken token)
 		{
 			if (!LikeHandler.MaySee(post, actor) || Normalise(content, ObjectShapes.Emojis(tags)) is not { } emoji)
+			{
+				Arrival.Drop(LikeHandler.MaySee(post, actor) ? "unparseable" : "not-visible");
 				return;
+			}
 			try
 			{
 				await DB.Default.SaveAsync(new Reaction
@@ -53,8 +57,10 @@ namespace PrivaPub.Domain.Social
 			}
 			catch (MongoWriteException ex) when (ex.WriteError?.Category == ServerErrorCategory.DuplicateKey)
 			{
+				Arrival.Drop("duplicate");
 				return;
 			}
+			Arrival.Accept("reaction");
 			if (!post.IsFederatedCopy)
 				await Notifications.Add(post.GroupUserId, NotificationType.Reaction, actor.ID, actor.ActorURI, post.ID, token, emoji.Name, emoji.Url);
 		}

PrivaPub/Domain/Statuses/QuoteService.cs

@@ -107,11 +107,18 @@ namespace PrivaPub.Domain.Statuses
 			var quotingUri = Id(instrument);
 			if (objectUri == default || quotingUri == default || !Origin.Same(quotingUri, actor.ActorURI)
 				|| instrument is JsonObject embedded && Id(embedded["attributedTo"]) is { } by && by != actor.ActorURI)
+			{
+				Arrival.Drop("misattributed");
 				return;
+			}
 			var quoted = await _dbEntities.Posts.Match(p => p.ObjectURI == objectUri && !p.IsFederatedCopy && !p.DeletedAt.HasValue).ExecuteFirstAsync(token);
 			var author = quoted == default ? default : await _localActors.FindById(LocalActorKind.Person, quoted.GroupUserId, token);
 			if (author == default || string.IsNullOrEmpty(actor.InboxURL))
+			{
+				Arrival.Drop("unknown-object");
 				return;
+			}
+			Arrival.About("Note", quoted.Visibility, quoted.CreationDate);
 			var answer = new JsonObject
 			{
 				["@context"] = ActivityPubRenderer.Context(),
@@ -121,12 +128,14 @@ namespace PrivaPub.Domain.Statuses
 			};
 			if (await MayQuote(quoted, actor.ActorURI, token))
 			{
+				Arrival.Accept("quote-granted");
 				answer["type"] = "Accept";
 				answer["result"] = await Grant(author, quoted, quotingUri, actor.ActorURI, token);
 				answer["id"] = author.ActivityUri($"accept-quote-{Guid.NewGuid():N}");
 			}
 			else
 			{
+				Arrival.Reject("quote-refused");
 				answer["type"] = "Reject";
 				answer["id"] = author.ActivityUri($"reject-quote-{Guid.NewGuid():N}");
 			}