indiekit-endpoint-activitypub/README.md

@rmdes/indiekit-endpoint-activitypub

ActivityPub federation endpoint for Indiekit, built on Fedify 2.1. Makes your IndieWeb site a full fediverse actor — discoverable, followable, and interactive from Mastodon, Misskey, Pixelfed, and any ActivityPub-compatible platform. Includes a Mastodon-compatible Client API so you can use Phanpy, Elk, Moshidon, Fedilab, and other Mastodon clients with your own AP instance.

Features

Federation

• Full ActivityPub actor with WebFinger, NodeInfo, HTTP Signatures, and Object Integrity Proofs (Ed25519)
• Outbox syndication — posts created via Micropub are automatically delivered to followers
• Inbox processing — receives follows, likes, boosts, replies, mentions, deletes, and account moves
• Content negotiation — ActivityPub clients requesting your site get JSON-LD; browsers get HTML
• Reply delivery — replies are addressed to and delivered directly to the original post's author
• Shared inbox support with collection sync (FEP-8fcf)
• Configurable actor type (Person, Service, Organization, Group)
• Manual follow approval — review and accept/reject follow requests before they take effect
• Direct messages — private conversations stored separately from the public timeline

Federation Resilience (v2.14.0+)

• Async inbox queue — inbound activities are persisted to MongoDB before processing, ensuring no data loss on crashes
• Server blocking — block entire remote servers by domain, rejecting all inbound activities from blocked instances
• Key freshness tracking — tracks when remote actor keys were last verified, skipping redundant re-fetches
• Redis-cached actor lookups — caches actor resolution results to reduce network round-trips
• Delivery strike tracking on ap_followers — counts consecutive delivery failures per follower
• FEP-fe34 security — verifies proof.created timestamps to reject replayed activities

Outbox Failure Handling (v2.15.0+, inspired by Hollo)

• 410 Gone — immediate full cleanup: removes the follower, their timeline items, and their notifications
• 404 Not Found — strike system: 3 consecutive failures over 7+ days triggers the same full cleanup
• Strike auto-reset — when an actor sends us any activity, their delivery failure count resets to zero
• Prevents orphaned data from accumulating over time while tolerating temporary server outages

Reply Intelligence (v2.15.0+, inspired by Hollo)

• Recursive reply chain fetching — when a reply arrives, fetches parent posts up to 5 levels deep for thread context
• Ancestor posts stored with isContext: true flag for thread view without cluttering the main timeline
• Reply forwarding to followers — when someone replies to our posts, the reply is forwarded to our followers so they see the full conversation
• Write-time visibility classification — computes public/unlisted/private/direct from to/cc fields at ingest time

Reader

• Timeline view showing posts from followed accounts with tab filtering (notes, articles, replies, boosts, media)
• Explore view — browse public timelines from any Mastodon-compatible instance
• Cross-instance hashtag search — search a hashtag across multiple fediverse instances
• Tag timeline — view and follow/unfollow specific hashtags
• Post detail view with threaded context
• Quote post embeds — quoted posts render as inline cards with author, content, and timestamp (FEP-044f, Misskey, Fedibird formats)
• Link preview cards via Open Graph metadata unfurling
• Notifications for likes, boosts, follows, mentions, and replies
• Compose form with dual-path posting (quick AP reply or Micropub blog post)
• Native interactions (like, boost, reply, follow/unfollow from the reader)
• Remote actor profile pages
• Content warnings and sensitive content handling
• Media display (images, video, audio)
• Infinite scroll with IntersectionObserver-based auto-loading
• New post banner — polls for new items and offers one-click loading
• Read tracking — marks posts as read on scroll, with unread filter toggle
• Popular accounts autocomplete in the fediverse lookup bar
• Configurable timeline retention

Moderation

• Mute actors or keywords
• Block actors (also removes from followers)
• Block entire servers by domain
• Report remote actors to their home instance (Flag activity)
• All moderation actions available from the reader UI

Mastodon Migration

• Import following/followers lists from Mastodon CSV exports
• Set alsoKnownAs alias for account Move verification
• Batch re-follow processor — gradually sends Follow activities to imported accounts
• Progress tracking with pause/resume controls

Public Profile

• Standalone profile page at the actor URL (HTML fallback for browsers)
• Shows avatar, bio, profile fields, follower/following/post counts, and follow prompt
• Dark mode support via system preference

Debug Dashboard

• Optional Fedify Debugger integration
• Password-protected dashboard at {mountPath}/__debug__/
• OpenTelemetry tracing for federation activity
• Real-time activity inspection

Mastodon Client API (v3.0.0+)

• Full Mastodon REST API compatibility — use Phanpy, Elk, Moshidon, Fedilab, or any Mastodon-compatible client
• OAuth2 with PKCE (S256) — app registration, authorization, token exchange
• HTML+JS redirect for native Android apps (Chrome Custom Tabs block 302 to custom URI schemes)
• Home, public, and hashtag timelines with chronological published-date pagination
• Status creation via Micropub pipeline — posts flow through Indiekit → content file → AP syndication
• URL auto-linkification and @mention extraction in posted content
• Thread context (ancestors + descendants)
• Remote profile resolution via Fedify WebFinger with follower/following/post counts from AP collections
• Account stats enrichment — cached account data applied immediately; uncached accounts resolved in background
• Favourite, boost, bookmark interactions federated via Fedify AP activities
• Notifications with type filtering
• Search across accounts, statuses, and hashtags with remote resolution
• Domain blocks API
• Timeline backfill from posts collection on startup (bookmarks, likes, reposts get synthesized content)
• In-memory account stats cache (500 entries, 1h TTL) for performance
• OAuth2 scope enforcement — read/write scope validation on all API routes
• Rate limiting — configurable limits on API, auth, and app registration endpoints
• Access token expiry (1 hour) with refresh token rotation (90 days)
• PKCE (S256) and CSRF protection on authorization flow

Admin UI

• Dashboard with follower/following counts and recent activity
• Profile editor (name, bio, avatar, header, profile links with rel="me" verification)
• Pinned posts (featured collection)
• Featured tags (hashtag collection)
• Activity log (inbound/outbound)
• Follower and following lists with source tracking
• Federation management page with moderation overview (blocked servers, blocked accounts, muted)

Standards Compliance

Core protocols and Fediverse Enhancement Proposals (FEPs) supported:

Standard	Name	Status	Provider
ActivityPub	W3C ActivityPub	Full (server-to-server)	Fedify 2.1
ActivityStreams 2.0	W3C Activity Streams	Full	Fedify 2.1
HTTP Signatures	draft-cavage HTTP Signatures	Full	Fedify 2.1
RFC 9421	HTTP Message Signatures	Full (with Accept-Signature negotiation)	Fedify 2.1
WebFinger	RFC 7033 WebFinger	Full	Fedify 2.1
NodeInfo 2.1	Server metadata discovery	Full (enriched)	Plugin
FEP-8b32	Object Integrity Proofs (Ed25519)	Full	Fedify 2.1
FEP-521a	Multiple key pairs (Multikey)	Full	Fedify 2.1
FEP-fe34	Origin-based security model	Full	Fedify 2.1 + Plugin
FEP-8fcf	Followers collection synchronization	Outbound only	Fedify 2.1
FEP-5feb	Search indexing consent	Full (indexable, discoverable)	Plugin
FEP-f1d5	Enhanced NodeInfo 2.1	Full (metadata, staff accounts)	Plugin
FEP-4f05	Soft delete with Tombstone	Full (410 + Tombstone JSON-LD)	Plugin
FEP-3b86	Activity Intents	Full (Follow, Create, Like, Announce)	Plugin
FEP-044f	Quote posts	Full (Mastodon, Misskey, Fedibird formats)	Fedify 2.1 + Plugin
FEP-c0e0	Emoji reactions (EmojiReact)	Vocab support (no UI)	Fedify 2.1
FEP-5711	Conversation threads	Vocab support	Fedify 2.1
Linked Data Signatures	RsaSignature2017 (legacy)	Full (outbound signing)	Fedify 2.1

Status key: Full = complete implementation, Outbound only = sending side only, Vocab support = types available but no dedicated UI/logic.

Provider key: Fedify 2.1 = handled by the Fedify framework, Plugin = implemented in this plugin, Fedify 2.1 + Plugin = framework provides primitives, plugin wires them together.

Requirements

• Indiekit v1.0.0-beta.25+
• Fedify 2.1+ (bundled as dependency)
• Node.js >= 22
• MongoDB (used by Indiekit)
• Redis (recommended for production delivery queue; in-process queue available for development)

Installation

npm install @rmdes/indiekit-endpoint-activitypub

Configuration

Add the plugin to your Indiekit config:

// indiekit.config.js
export default {
  plugins: [
    "@rmdes/indiekit-endpoint-activitypub",
  ],
  "@rmdes/indiekit-endpoint-activitypub": {
    mountPath: "/activitypub",
    actor: {
      handle: "yourname",
      name: "Your Name",
      summary: "A short bio",
      icon: "https://example.com/avatar.jpg",
    },
  },
};

All Options

Option	Type	Default	Description
mountPath	string	"/activitypub"	URL prefix for all plugin routes
actor.handle	string	"rick"	Fediverse username (e.g. @handle@yourdomain.com)
actor.name	string	""	Display name (used to seed profile on first run)
actor.summary	string	""	Bio text (used to seed profile on first run)
actor.icon	string	""	Avatar URL (used to seed profile on first run)
checked	boolean	true	Whether the syndicator is checked by default in the post editor
alsoKnownAs	string	""	Mastodon migration alias URL
activityRetentionDays	number	90	Days to keep activity log entries (0 = forever)
storeRawActivities	boolean	false	Store full raw JSON of inbound activities
redisUrl	string	""	Redis connection URL for delivery queue
parallelWorkers	number	5	Number of parallel delivery workers (requires Redis)
actorType	string	"Person"	Actor type: Person, Service, Organization, or Group
logLevel	string	"warning"	Fedify log level: "debug", "info", "warning", "error", "fatal"
timelineRetention	number	1000	Maximum timeline items to keep (0 = unlimited)
notificationRetentionDays	number	30	Days to keep notifications (0 = forever)
debugDashboard	boolean	false	Enable Fedify debug dashboard at {mountPath}/__debug__/
debugPassword	string	""	Password for the debug dashboard (required if dashboard enabled)

Redis (Recommended for Production)

Without Redis, the plugin uses an in-process message queue. This works for development but won't survive restarts and has limited throughput.

"@rmdes/indiekit-endpoint-activitypub": {
  redisUrl: "redis://localhost:6379",
  parallelWorkers: 5,
},

Nginx Configuration (Reverse Proxy)

If you serve a static site alongside Indiekit (e.g. with Eleventy), you need nginx rules to route ActivityPub requests to Indiekit while serving HTML to browsers:

# ActivityPub content negotiation — detect AP clients
map $http_accept $is_activitypub {
    default 0;
    "~*application/activity\+json" 1;
    "~*application/ld\+json" 1;
}

# Proxy /activitypub to Indiekit
location /activitypub {
    proxy_pass http://127.0.0.1:8080;
    proxy_set_header Host $host;
    proxy_set_header X-Forwarded-Proto https;
}

# Default: static site, but AP clients get proxied
location / {
    if ($is_activitypub) {
        proxy_pass http://127.0.0.1:8080;
    }
    try_files $uri $uri/ $uri.html =404;
}

How It Works

Syndication (Outbound)

When you create a post via Micropub, Indiekit's syndication system calls this plugin's syndicator. The plugin:

1. Converts the JF2 post properties to an ActivityStreams 2.0 Create(Note) or Create(Article) activity
2. For replies, resolves the original post's author to include them in CC and deliver directly to their inbox
3. Sends the activity to all followers via shared inboxes using Fedify's delivery queue
4. Appends a permalink to the content so fediverse clients link back to your canonical post

Inbox Processing (Inbound)

When remote servers send activities to your inbox:

• Follow → Auto-accepted, stored in ap_followers, notification created
• Undo(Follow) → Removed from ap_followers
• Like → Logged in activity log, notification created (only for reactions to your own posts)
• Announce (Boost) → Logged + notification (your content) or stored in timeline (followed account)
• Create (Note/Article) → Stored in timeline if from a followed account; notification if it's a reply or mention
• Update → Updates timeline item content or refreshes follower profile data
• Delete → Removes from activity log and timeline
• Move → Updates follower's actor URL
• Accept(Follow) → Marks our follow as accepted
• Reject(Follow) → Marks our follow as rejected
• Block → Removes actor from our followers
• Flag → Outbound report sent to remote actor's instance

Content Negotiation

The plugin mounts a root-level router that intercepts requests from ActivityPub clients (detected by Accept: application/activity+json or application/ld+json):

• Root URL (/) → Redirects to the Fedify actor document
• Post URLs → Looks up the post in MongoDB, converts to AS2 JSON
• NodeInfo (/nodeinfo/2.1) → Delegated to Fedify

Regular browser requests pass through unmodified.

Mastodon Migration

The plugin supports migrating from a Mastodon account:

1. Set alias — Configure alsoKnownAs with your old Mastodon profile URL. This is verified by Mastodon before allowing a Move.
2. Import social graph — Upload Mastodon's following_accounts.csv and followers.csv exports. Following entries are resolved via WebFinger and stored locally.
3. Trigger Move — From Mastodon's settings, initiate a Move to @handle@yourdomain.com. Mastodon notifies your followers, and compatible servers auto-refollow.
4. Batch re-follow — The plugin gradually sends Follow activities to all imported accounts (10 per batch, 30s between batches) so remote servers start delivering content to your inbox.

Verification

After deployment, verify federation is working:

# WebFinger discovery
curl -s "https://yourdomain.com/.well-known/webfinger?resource=acct:handle@yourdomain.com" | jq .

# Actor document
curl -s -H "Accept: application/activity+json" "https://yourdomain.com/" | jq .

# NodeInfo
curl -s "https://yourdomain.com/nodeinfo/2.1" | jq .

Then search for @handle@yourdomain.com from any Mastodon instance — your profile should appear.

Admin UI Pages

All admin pages are behind IndieAuth authentication:

Page	Path	Description
Dashboard	/activitypub	Overview with follower/following counts, recent activity
Reader	/activitypub/admin/reader	Timeline from followed accounts (tabbed: notes, articles, replies, boosts, media)
Explore	/activitypub/admin/reader/explore	Browse public timelines from Mastodon-compatible instances
Hashtag Explore	/activitypub/admin/reader/explore/hashtag	Search a hashtag across multiple fediverse instances
Tag Timeline	/activitypub/admin/reader/tag?tag=name	Posts filtered by a specific hashtag, with follow/unfollow
Post Detail	/activitypub/admin/reader/post?url=...	Single post view with quote embeds and link previews
Notifications	/activitypub/admin/reader/notifications	Likes, boosts, follows, mentions, replies
Compose	/activitypub/admin/reader/compose	Reply composer (quick AP or Micropub)
Moderation	/activitypub/admin/reader/moderation	Muted/blocked accounts and keywords
Profile	/activitypub/admin/profile	Edit actor display name, bio, avatar, links
Followers	/activitypub/admin/followers	List of accounts following you
Following	/activitypub/admin/following	List of accounts you follow
Activity Log	/activitypub/admin/activities	Inbound/outbound activity history
Pinned Posts	/activitypub/admin/featured	Pin/unpin posts to your featured collection
Featured Tags	/activitypub/admin/tags	Add/remove featured hashtags
Migration	/activitypub/admin/migrate	Mastodon import wizard
Public Profile	/activitypub/users/{handle}	Public-facing profile page (no auth)
Debug Dashboard	/activitypub/__debug__/	Fedify debugger (password-protected, if enabled)

MongoDB Collections

The plugin creates these collections automatically:

Collection	Description
ap_followers	Accounts following your actor (includes delivery failure strike tracking)
ap_following	Accounts you follow
ap_activities	Activity log with automatic TTL cleanup
ap_keys	RSA and Ed25519 key pairs for HTTP Signatures
ap_kv	Fedify key-value store and batch job state
ap_profile	Actor profile (single document)
ap_featured	Pinned/featured posts
ap_featured_tags	Featured hashtags
ap_timeline	Reader timeline items (includes visibility and isContext fields)
ap_notifications	Interaction notifications
ap_muted	Muted actors and keywords
ap_blocked	Blocked actors
ap_interactions	Per-post like/boost tracking
ap_messages	Direct messages / private conversations
ap_followed_tags	Hashtags you follow for timeline filtering
ap_explore_tabs	Saved Mastodon instances for the explore view
ap_reports	Outbound reports (Flag activities) sent to remote instances
ap_pending_follows	Follow requests awaiting manual approval
ap_blocked_servers	Blocked server domains (instance-level blocks)
ap_key_freshness	Tracks when remote actor keys were last verified
ap_inbox_queue	Persistent async inbox processing queue
ap_tombstones	Tombstone records for soft-deleted posts (FEP-4f05)
ap_oauth_apps	Mastodon API client app registrations
ap_oauth_tokens	OAuth2 authorization codes and access tokens
ap_markers	Read position markers for Mastodon API clients

Supported Post Types

The JF2-to-ActivityStreams converter handles these Indiekit post types:

Post Type	ActivityStreams
note, reply, bookmark, jam, rsvp, checkin	Create(Note)
article	Create(Article)
like	Like
repost	Announce
photo, video, audio	Attachments on Note/Article

Categories are converted to Hashtag tags. Bookmarks include a bookmark emoji and link.

Fedify Workarounds and Implementation Notes

This plugin uses Fedify 2.1 but carries several workarounds for issues in Fedify or its Express integration. These are documented here so they can be revisited when Fedify upgrades.

Custom Express Bridge (instead of @fedify/express)

File: lib/federation-bridge.js Upstream issue: @fedify/express uses req.url (source, line 73), not req.originalUrl.

Indiekit plugins mount at a sub-path (e.g. /activitypub). Express strips the mount prefix from req.url, so Fedify's URI template matching breaks — WebFinger, actor endpoints, and inbox all return 404. The custom bridge uses req.originalUrl to preserve the full path.

The bridge also reconstructs POST bodies that Express's body parser has already consumed (req.readable === false). Without this, Fedify handlers like the @fedify/debugger login form receive empty bodies.

Revisit when: @fedify/express switches to req.originalUrl, or provides an option to pass a custom URL builder.

JSON-LD Attachment Array Compaction

File: lib/federation-bridge.js (in sendFedifyResponse()) Upstream issue: JSON-LD compaction collapses single-element arrays to plain objects.

Mastodon's update_account_fields checks attachment.is_a?(Array) and silently skips profile links (PropertyValues) when attachment is a plain object instead of an array. The bridge intercepts actor JSON-LD responses and forces attachment to always be an array.

Revisit when: Fedify adds an option to preserve arrays during JSON-LD serialization, or Mastodon fixes their array check.

Endpoints as:Endpoints Type Stripping — REMOVED

Upstream issue: fedify#576 — FIXED in Fedify 2.1.0

This workaround has been removed. Fedify 2.1.0 now omits the invalid "type": "as:Endpoints" from serialized actor JSON.

PropertyValue Attachment Type (Known Issue)

Upstream issue: fedify#629 — OPEN

Fedify serializes PropertyValue attachments (used by Mastodon for profile metadata fields) with "type": "PropertyValue", a schema.org type that is not a valid AS2 Object or Link. browser.pub rejects /attachment as invalid. However, every Mastodon-compatible server emits PropertyValue — removing it would break profile field display across the fediverse.

No workaround applied. This is a de facto fediverse standard despite not being in the AS2 vocabulary.

.authorize() Not Chained on Actor Dispatcher

File: lib/federation-setup.js (line ~254) Upstream issue: No authenticated document loading for outgoing key fetches during signature verification.

Fedify's .authorize() predicate triggers HTTP Signature verification on every GET to the actor endpoint. When a remote server that requires Authorized Fetch (e.g. kobolds.online) requests our actor, Fedify tries to fetch their public key to verify the signature. Those servers return 401 on unsigned GETs, causing uncaught FetchError and 500 responses.

This means we do not enforce Authorized Fetch on our actor endpoint. Any server can read our actor document without signing the request.

Revisit when: Fedify supports using the instance actor's keys for outgoing document fetches during signature verification (i.e. authenticated document loading in the verification path, not just in inbox handlers).

importSpkiPem() / importPkcs8Pem() — Local PEM Import

File: lib/federation-setup.js (lines ~784–816) Upstream change: Fedify 1.x exported importSpki() for loading PEM public keys. This was removed in Fedify 2.0.

The plugin carries local importSpkiPem() and importPkcs8Pem() functions that use the Web Crypto API directly (crypto.subtle.importKey) to load legacy RSA key pairs stored in MongoDB from the Fedify 1.x era. New key pairs are generated using Fedify 2.0's generateCryptoKeyPair() and stored as JWK, so these functions only matter for existing installations that migrated from Fedify 1.x.

Revisit when: All existing installations have been migrated to JWK-stored keys, or Fedify re-exports a PEM import utility.

Authenticated Document Loader for Inbox Handlers

File: lib/inbox-listeners.js Upstream behavior: Fedify's personal inbox handlers do not automatically use authenticated (signed) HTTP fetches.

All .getActor(), .getObject(), and .getTarget() calls in inbox handlers must explicitly pass an authenticated DocumentLoader obtained via ctx.getDocumentLoader({ identifier: handle }). Without this, fetches to Authorized Fetch (Secure Mode) servers like hachyderm.io fail with 401, causing timeline items to show "Unknown" authors and missing content.

This is not a bug — Fedify requires explicit opt-in for signed fetches. But it's a pattern that every inbox handler must follow, and forgetting it silently degrades functionality.

Revisit when: Fedify provides an option to default to authenticated fetches in inbox handler context, or adds a middleware layer that handles this automatically.

Known Limitations

• No automated tests — Manual testing against real fediverse servers
• Single actor — One fediverse identity per Indiekit instance
• No Authorized Fetch enforcement — .authorize() disabled on actor dispatcher (see workarounds above)
• No image upload in reader — Compose form is text-only
• In-process queue without Redis — Activities may be lost on restart

Acknowledgements

This plugin builds on the excellent Fedify framework by Hong Minhee. Fedify provides the core ActivityPub federation layer — HTTP Signatures, content negotiation, message queues, and the vocabulary types that make all of this possible.

Several federation patterns in this plugin were inspired by studying other open-source ActivityPub implementations:

• Hollo (by the Fedify author) — A single-user Fedify-based ActivityPub server that served as the primary reference implementation. The outbox permanent failure handling (410 cleanup and 404 strike system), recursive reply chain fetching, reply forwarding to followers, and write-time visibility classification in v2.15.0 are all adapted from Hollo's patterns for a MongoDB/single-user context.

• Wafrn — A federated social network whose ActivityPub implementation informed the operational resilience patterns added in v2.14.0. Server blocking, key freshness tracking, async inbox processing with persistent queues, and the general approach to federation hardening were inspired by studying Wafrn's production codebase.

License

MIT

Author

Ricardo Mendes (@rick@rmendes.net)