Public threads name their replies and context

Owner decision of 2026-10-06: a persona's public or unlisted post outside any group names its replies
(…/scribbles/{id}/replies) and its conversation's context (FEP-7888), the root's …/context that a reply inherits from
its parent, ours or another server's. Both list only the public and unlisted posts PrivaPub holds; followers-only,
circle, direct and local-only posts name neither and their collections answer 404. Checked live: opening alice's
thread on Mastodon finds carol's reply, which nobody there follows (scenarios/threads.sh).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

PrivaPub/Federation/Controllers/PeasantsController.cs

@@ -235,6 +235,42 @@ namespace PrivaPub.Federation.Controllers
 			return Activity(note);
 		}
 
+		// the public and unlisted replies PrivaPub holds to a public post (owner decision 2026-10-06), oldest first
+		[HttpGet, Route("{actor}/scribbles/{postId}/replies")]
+		public async Task<IActionResult> Replies(string actor, string postId, CancellationToken token)
+		{
+			var (local, post) = await PublicPost(actor, postId, token);
+			if (post == default || post.IsLocalOnly || !string.IsNullOrEmpty(post.GroupId))
+				return NotFound();
+			var replies = await _dbEntities.Posts.Match(p => p.AnsweringToPostId == post.ID && !p.IsLocalOnly && p.ReblogOfPostId == null)
+				.Match(VisibilityPolicy.IsPublic).Sort(p => p.CreationDate, Order.Ascending).Limit(MaxThread).ExecuteAsync(token);
+			return Activity(ActivityPubRenderer.OrderedCollection(local.PostUri(post.ID) + "/replies", replies.Count,
+				replies.Select(r => (JsonNode)r.ObjectURI)));
+		}
+
+		// a public conversation this post starts (FEP-7888): it and every public or unlisted reply under it PrivaPub holds
+		[HttpGet, Route("{actor}/scribbles/{postId}/context")]
+		public async Task<IActionResult> Context(string actor, string postId, CancellationToken token)
+		{
+			var (local, root) = await PublicPost(actor, postId, token);
+			if (root == default || root.IsLocalOnly || !string.IsNullOrEmpty(root.GroupId) || root.ContextURI != local.PostUri(root.ID) + "/context")
+				return NotFound();
+			var thread = new List<PostEntity> { root };
+			var level = new List<string> { root.ID };
+			for (var depth = 0; depth < PrivaPub.Federation.Inbox.RemotePosts.MaxDepth && level.Count > 0 && thread.Count < MaxThread; depth++)
+			{
+				var next = await _dbEntities.Posts.Match(p => level.Contains(p.AnsweringToPostId) && !p.IsLocalOnly && p.ReblogOfPostId == null)
+					.Match(VisibilityPolicy.IsPublic).Sort(p => p.CreationDate, Order.Ascending).Limit(MaxThread - thread.Count).ExecuteAsync(token);
+				thread.AddRange(next);
+				level = next.Select(p => p.ID).ToList();
+			}
+			var collection = ActivityPubRenderer.OrderedCollection(root.ContextURI, thread.Count, thread.Select(p => (JsonNode)p.ObjectURI));
+			collection["attributedTo"] = local.Uri;
+			return Activity(collection);
+		}
+
+		const int MaxThread = 500;
+
 		[HttpGet, Route("{actor}/parrot-licences/{licenceId}")]
 		public async Task<IActionResult> ParrotLicence(string actor, string licenceId, CancellationToken token)
 		{

PrivaPub/Federation/Rendering/ActivityPubRenderer.cs

@@ -162,6 +162,14 @@ namespace PrivaPub.Federation.Rendering
 				cc.Add(post.InReplyToActorURI);
 
 			var note = NoteBody(post, author, to, cc, inReplyTo);
+			// a public thread names where its replies and its whole conversation are read (owner decision 2026-10-06):
+			// Mastodon, GoToSocial and Fedify complete threads from them
+			if (!post.IsFederatedCopy && group == default && !post.IsLocalOnly && post.Visibility is PostVisibility.Public or PostVisibility.Unlisted)
+			{
+				note["replies"] = author.PostUri(post.ID) + "/replies";
+				if (!string.IsNullOrEmpty(post.ContextURI))
+					note["context"] = post.ContextURI;
+			}
 			if (group != default)
 				note["audience"] = group.Uri;
 			else if (!string.IsNullOrEmpty(post.AudienceURI))