Conversations are keyed by who is in them, and circles stay home

S8: a direct message joins a conversation only when its participants are
exactly that conversation's members, found through a new
DmGroup.ParticipantsKey (a hash of the sorted members). A remote context
no longer decides anything: it let anyone who knew a conversation's
context post into it, and joining by context while dropping a participant
would have shown a reply to someone it was not addressed to. A context is
kept only when it is on the author's origin. Sending a DM to the same
people again reuses their conversation instead of opening a new one.

S9: Group.Kind is Circle or Community. A circle is not a federated actor:
its actor, collections, WebFinger and inbox answer 404, a remote Follow is
refused, and posts in it are IsLocalOnly - never delivered, never in an
outbox, never served. Communities keep today's behaviour until P4.
Migration _003 makes every existing group a circle, marks their posts
local-only and backfills the conversation keys.

End-to-end inbox tests sign real deliveries from a fake peer: a context
injection, a forged activity id, a note attributed to someone else, a
cross-origin object, a bad signature, junk bodies and a Follow of a circle.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012CzABvBkbcFqoHdmi8b9WB

PrivaPub/Federation/Controllers/PeasantsController.cs

@@ -38,23 +38,23 @@ namespace PrivaPub.Federation.Controllers
 		public async Task<IActionResult> GetActor(string actor, CancellationToken token)
 		{
 			var local = await _localActors.FindByUserName(actor, token);
-			return local == default ? NotFound() : Activity(ActivityPubRenderer.Actor(local));
+			return local is not { IsFederated: true } ? NotFound() : Activity(ActivityPubRenderer.Actor(local));
 		}
 
 		[HttpGet, Route("{actor}/anus")]
 		public async Task<IActionResult> Outbox(string actor, CancellationToken token)
 		{
 			var local = await _localActors.FindByUserName(actor, token);
-			if (local == default)
+			if (local is not { IsFederated: true })
 				return NotFound();
 
 			var total = local.Kind == LocalActorKind.Group
-				? await DB.Default.CountAsync<PostEntity>(p => p.GroupId == local.Id, token)
-				: await DB.Default.CountAsync<PostEntity>(p => p.GroupUserId == local.Id && !p.IsFederatedCopy, token);
+				? await DB.Default.CountAsync<PostEntity>(p => p.GroupId == local.Id && !p.IsLocalOnly, token)
+				: await DB.Default.CountAsync<PostEntity>(p => p.GroupUserId == local.Id && !p.IsFederatedCopy && !p.IsLocalOnly, token);
 
 			var latest = await (local.Kind == LocalActorKind.Group
-					? _dbEntities.Posts.Match(p => p.GroupId == local.Id)
-					: _dbEntities.Posts.Match(p => p.GroupUserId == local.Id && !p.IsFederatedCopy))
+					? _dbEntities.Posts.Match(p => p.GroupId == local.Id && !p.IsLocalOnly)
+					: _dbEntities.Posts.Match(p => p.GroupUserId == local.Id && !p.IsFederatedCopy && !p.IsLocalOnly))
 				.Sort(p => p.CreationDate, Order.Descending)
 				.Limit(OutboxSize)
 				.ExecuteAsync(token);
@@ -79,7 +79,7 @@ namespace PrivaPub.Federation.Controllers
 		public async Task<IActionResult> Followers(string actor, CancellationToken token)
 		{
 			var local = await _localActors.FindByUserName(actor, token);
-			if (local == default)
+			if (local is not { IsFederated: true })
 				return NotFound();
 			var count = await DB.Default.CountAsync<Follower>(
 				f => f.LocalActorId == local.Id && f.LocalActorKind == local.Kind && f.IsAccepted, token);
@@ -90,7 +90,7 @@ namespace PrivaPub.Federation.Controllers
 		public async Task<IActionResult> Following(string actor, CancellationToken token)
 		{
 			var local = await _localActors.FindByUserName(actor, token);
-			return local == default ? NotFound() : Activity(ActivityPubRenderer.OrderedCollection(local.Following, 0, Enumerable.Empty<JsonNode>()));
+			return local is not { IsFederated: true } ? NotFound() : Activity(ActivityPubRenderer.OrderedCollection(local.Following, 0, Enumerable.Empty<JsonNode>()));
 		}
 
 		[HttpGet, Route("{actor}/posts/{postId}")]
@@ -101,7 +101,7 @@ namespace PrivaPub.Federation.Controllers
 				return NotFound();
 
 			var post = await _dbEntities.Posts
-				.Match(p => p.ID == postId && p.GroupUserId == local.Id && !p.IsFederatedCopy)
+				.Match(p => p.ID == postId && p.GroupUserId == local.Id && !p.IsFederatedCopy && !p.IsLocalOnly)
 				.ExecuteFirstAsync(token);
 			if (post == default)
 				return NotFound();
@@ -117,7 +117,7 @@ namespace PrivaPub.Federation.Controllers
 		public async Task<IActionResult> Inbox(string actor, CancellationToken token)
 		{
 			var local = await _localActors.FindByUserName(actor, token);
-			if (local == default)
+			if (local is not { IsFederated: true })
 				return NotFound();
 			return Answer(await _inbox.Receive(Request, local, token));
 		}

PrivaPub/Federation/Controllers/WellKnownController.cs

@@ -43,7 +43,7 @@ namespace PrivaPub.Federation.Controllers
 			else
 				actor = await _localActors.FindByUri(resource, token);
 
-			if (actor == default)
+			if (actor is not { IsFederated: true })
 				return NotFound();
 
 			var document = new JsonObject