Everything on, phase 2: circle posts for everyone, private posts on signed refetch, browsers past SecureMode

Circles (owner decision 2026-10-04: fix them for compatibility):
- Mastodon 4.7 and GoToSocial drop a post that names none of their accounts, and a circle post named only the circle
  and its /flock. OutboxPublisher.Publish now sends each member a copy that also names that member in `cc`, on the
  activity and on the object, and names no other member. The Create, every Update (edit, poll, quote approval, policy,
  through the new PublishUpdate) and the Delete (StatusService.Remove now uses Publish) all go that way.
- UpdateOf renders with the post's group, so an Update keeps a circle post's `audience` and a community post's `Page`
  and title.
- A reply to a circle post stays in the circle, whichever client wrote it.
- A circle post can no longer quote a post that needs permission: asking would show the circle post to its author.

Posts that are not public, on refetch (SignedFetchAuthorizer.MayRead):
- Followers-only, direct and circle posts are served to a signed request from someone they were for, or from the
  instance actor of a server where one of them lives. That is a follower or an addressed account, an addressed
  account, or a member. Everyone else still gets 404.
- Once deleted they answer those readers 410. Mastodon deletes its copy when a refetch answers 404.
- A circle refetch names the requesting member, or the members on the requesting server, as the delivered copy did.
- /grunts/create-{id} serves the same.
- /peasants/{name}/whispers/{id}, a DM's `context`, was never routed. It is now the conversation's posts, for its
  participants only.

SecureMode lets browsers through to the redirect to the public page, instead of answering them 401.

653 tests pass.

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

PrivaPub/Federation/Controllers/PeasantsController.cs

@@ -17,6 +17,7 @@ using PrivaPub.Domain.Privacy;
 using PrivaPub.Federation.Actors;
 using PrivaPub.Federation.Rendering;
 using PrivaPub.Federation.Inbox;
+using PrivaPub.Federation.Outbox;
 using PrivaPub.Federation.Signing;
 using PrivaPub.Infrastructure.Http;
 using PrivaPub.Models.Group;
@@ -185,11 +186,13 @@ namespace PrivaPub.Federation.Controllers
 		public async Task<IActionResult> Post(string actor, string postId, CancellationToken token)
 		{
 			var (local, post) = await PublicPost(actor, postId, token);
-			if (post == default && await CirclePost(actor, postId, token) is { } circlePost)
+			if (post == default && await SignedPost(actor, postId, token) is { } signed)
 			{
-				var circleNote = ActivityPubRenderer.Note(circlePost.Post, circlePost.Author, circlePost.Circle, circlePost.Post.InReplyToURI);
-				circleNote["@context"] = ActivityPubRenderer.Context();
-				return Activity(circleNote);
+				if (signed.Post.DeletedAt.HasValue)
+					return TombstoneOf(signed.Author, signed.Post);
+				var signedNote = (JsonObject)signed.Note.DeepClone();
+				signedNote["@context"] = ActivityPubRenderer.Context();
+				return Activity(signedNote);
 			}
 			if (post == default)
 				return await Tombstone(actor, postId, token) ?? NotFound();
@@ -243,7 +246,36 @@ namespace PrivaPub.Federation.Controllers
 			if (!activityId.StartsWith("create-", StringComparison.Ordinal))
 				return NotFound();
 			var (local, post) = await PublicPost(actor, activityId["create-".Length..], token);
-			return post == default ? NotFound() : Activity(await CreateFor(post, local, token));
+			if (post != default)
+				return Activity(await CreateFor(post, local, token));
+			return await SignedPost(actor, activityId["create-".Length..], token) is { Post.DeletedAt: null } signed
+				? Activity(ActivityPubRenderer.Create(signed.Author, (JsonObject)signed.Note.DeepClone(), activityId))
+				: NotFound();
+		}
+
+		// A DM's `context`: the conversation's posts, for its participants (or their servers' instance actors) only.
+		[HttpGet, Route("{actor}/whispers/{conversationId}")]
+		public async Task<IActionResult> Whispers(string actor, string conversationId, CancellationToken token)
+		{
+			var local = await _localActors.FindByUserName(actor, token);
+			if (local is not { IsFederated: true, Kind: LocalActorKind.Person })
+				return NotFound();
+			var uri = local.ConversationUri(conversationId);
+			var conversation = await _dbEntities.DmGroups.Match(g => g.ID == conversationId && g.ConversationURI == uri && !g.DeletionAt.HasValue).ExecuteFirstAsync(token);
+			if (conversation == default || !SignedFetchAuthorizer.MayReadConversation(conversation, await _fetches.Requester(Request, token)))
+				return NotFound();
+			var posts = await _dbEntities.Posts
+				.Match(p => p.ConversationId == conversationId && p.Visibility == PostVisibility.Direct && !p.DeletedAt.HasValue)
+				.Sort(p => p.CreationDate, Order.Ascending)
+				.ExecuteAsync(token);
+			return Activity(new JsonObject
+			{
+				["@context"] = ActivityPubRenderer.ActivityStreams,
+				["id"] = uri,
+				["type"] = "OrderedCollection",
+				["totalItems"] = posts.Count,
+				["orderedItems"] = new JsonArray(posts.Select(p => (JsonNode)p.ObjectURI).ToArray())
+			});
 		}
 
 		[HttpPost, Route("{actor}/mouth"), EnableRateLimiting(RateLimiting.Inbox)]
@@ -275,18 +307,35 @@ namespace PrivaPub.Federation.Controllers
 			return (local, post);
 		}
 
-		async Task<(LocalActor Author, LocalActor Circle, PostEntity Post)?> CirclePost(string actor, string postId, CancellationToken token)
+		// A followers-only, direct or circle post (deleted ones included), for a signed request from someone it was for
+		// (SignedFetchAuthorizer.MayRead). It is rendered as it was delivered: a circle post also names, in cc, the requesting
+		// member, or the members on the requesting instance actor's server.
+		async Task<(LocalActor Author, PostEntity Post, JsonObject Note)?> SignedPost(string actor, string postId, CancellationToken token)
 		{
 			var local = await _localActors.FindByUserName(actor, token);
-			if (local is not { Kind: LocalActorKind.Person })
+			if (local is not { IsFederated: true, Kind: LocalActorKind.Person })
 				return default;
 			var post = await _dbEntities.Posts
-				.Match(p => p.ID == postId && p.GroupUserId == local.Id && !p.IsFederatedCopy && !p.DeletedAt.HasValue && p.Visibility == PostVisibility.Circle)
+				.Match(p => p.ID == postId && p.GroupUserId == local.Id && !p.IsFederatedCopy && p.ReblogOfPostId == null
+					&& (p.Visibility == PostVisibility.FollowersOnly || p.Visibility == PostVisibility.Direct || p.Visibility == PostVisibility.Circle))
 				.ExecuteFirstAsync(token);
-			var circle = post == default ? default : await _dbEntities.Groups.MatchID(post.GroupId).ExecuteFirstAsync(token);
-			if (circle == default || !SignedFetchAuthorizer.MayReadCircle(circle, await _fetches.Requester(Request, token)))
+			if (post == default)
 				return default;
-			return (local, _localActors.FromGroup(circle), post);
+			var requester = await _fetches.Requester(Request, token);
+			if (!await _fetches.MayRead(post, requester, token))
+				return default;
+			if (post.Visibility == PostVisibility.Circle)
+			{
+				var circle = await _dbEntities.Groups.MatchID(post.GroupId).ExecuteFirstAsync(token);
+				var note = ActivityPubRenderer.Note(post, local, _localActors.FromGroup(circle), post.InReplyToURI);
+				return (local, post, OutboxPublisher.Naming(note, SignedFetchAuthorizer.CircleReaders(circle, requester)));
+			}
+			var rendered = post.Visibility == PostVisibility.Direct
+				? ActivityPubRenderer.DirectNote(post, local, Array.Empty<(string, string)>(), post.ContextURI)
+				: ActivityPubRenderer.Note(post, local, default, post.InReplyToURI);
+			rendered["to"] = new JsonArray(post.To.Select(t => (JsonNode)t).ToArray());
+			rendered["cc"] = new JsonArray(post.Cc.Select(c => (JsonNode)c).ToArray());
+			return (local, post, rendered);
 		}
 
 		async Task<IActionResult> Tombstone(string actor, string postId, CancellationToken token)
@@ -298,8 +347,11 @@ namespace PrivaPub.Federation.Controllers
 				.Match(p => p.ID == postId && p.GroupUserId == local.Id && !p.IsFederatedCopy && p.DeletedAt.HasValue
 					&& (p.Visibility == PostVisibility.Public || p.Visibility == PostVisibility.Unlisted))
 				.ExecuteFirstAsync(token);
-			if (deleted == default)
-				return default;
+			return deleted == default ? default : TombstoneOf(local, deleted);
+		}
+
+		ContentResult TombstoneOf(LocalActor local, PostEntity deleted)
+		{
 			var tombstone = new JsonObject
 			{
 				["@context"] = ActivityPubRenderer.ActivityStreams,
@@ -349,7 +401,9 @@ namespace PrivaPub.Federation.Controllers
 		{
 			if (HttpMethods.IsGet(Request.Method))
 				Response.Headers.Vary = "Accept";
-			if (_federation.CurrentValue.SecureMode && HttpMethods.IsGet(Request.Method)
+			// SecureMode asks every reader of ActivityPub documents for a signature, except for the instance actor, whose key
+			// peers need first, and except for browsers, which only get redirected to the public pages
+			if (_federation.CurrentValue.SecureMode && HttpMethods.IsGet(Request.Method) && !WantsHtml()
 				&& !string.Equals(context.RouteData.Values["actor"] as string, LocalActorService.InstanceUserName, StringComparison.OrdinalIgnoreCase)
 				&& await _fetches.Requester(Request, HttpContext.RequestAborted) == default)
 			{