Add per-app ActivityPub actors via shared AP blueprint

Each AP-enabled app (blog, market, events, federation) now serves its
own webfinger, actor profile, inbox, outbox, and followers endpoints.
Per-app actors are virtual projections of the same ActorProfile/keypair,
scoped by APFollower.app_domain and APActivity.origin_app.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

alembic/versions/t0r8n4o6p7_add_app_domain_to_ap_followers.py

@@ -0,0 +1,42 @@
+"""Add app_domain to ap_followers for per-app AP actors
+
+Revision ID: t0r8n4o6p7
+Revises: s9q7n3o5p6
+"""
+from alembic import op
+import sqlalchemy as sa
+
+revision = "t0r8n4o6p7"
+down_revision = "s9q7n3o5p6"
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.add_column(
+        "ap_followers",
+        sa.Column("app_domain", sa.String(64), nullable=True),
+    )
+    # Replace old unique constraint with one that includes app_domain
+    op.drop_constraint("uq_follower_acct", "ap_followers", type_="unique")
+    op.create_unique_constraint(
+        "uq_follower_acct_app",
+        "ap_followers",
+        ["actor_profile_id", "follower_acct", "app_domain"],
+    )
+    op.create_index(
+        "ix_ap_follower_app_domain",
+        "ap_followers",
+        ["actor_profile_id", "app_domain"],
+    )
+
+
+def downgrade():
+    op.drop_index("ix_ap_follower_app_domain", table_name="ap_followers")
+    op.drop_constraint("uq_follower_acct_app", "ap_followers", type_="unique")
+    op.create_unique_constraint(
+        "uq_follower_acct",
+        "ap_followers",
+        ["actor_profile_id", "follower_acct"],
+    )
+    op.drop_column("ap_followers", "app_domain")

contracts/dtos.py

@@ -176,6 +176,7 @@ class APFollowerDTO:
     follower_inbox: str
     follower_actor_url: str
     created_at: datetime | None = None
+    app_domain: str | None = None
 
 
 @dataclass(frozen=True, slots=True)

contracts/protocols.py

@@ -222,6 +222,7 @@ class FederationService(Protocol):
     async def get_outbox(
         self, session: AsyncSession, username: str,
         page: int = 1, per_page: int = 20,
+        origin_app: str | None = None,
     ) -> tuple[list[APActivityDTO], int]: ...
 
     async def get_activity_for_source(
@@ -236,6 +237,7 @@ class FederationService(Protocol):
     # -- Followers ------------------------------------------------------------
     async def get_followers(
         self, session: AsyncSession, username: str,
+        app_domain: str | None = None,
     ) -> list[APFollowerDTO]: ...
 
     async def get_followers_paginated(
@@ -247,10 +249,12 @@ class FederationService(Protocol):
         self, session: AsyncSession, username: str,
         follower_acct: str, follower_inbox: str, follower_actor_url: str,
         follower_public_key: str | None = None,
+        app_domain: str | None = None,
     ) -> APFollowerDTO: ...
 
     async def remove_follower(
         self, session: AsyncSession, username: str, follower_acct: str,
+        app_domain: str | None = None,
     ) -> bool: ...
 
     # -- Remote actors --------------------------------------------------------

events/handlers/ap_delivery_handler.py

@@ -131,10 +131,30 @@ async def on_any_activity(activity: APActivity, session: AsyncSession) -> None:
         log.warning("Actor not found or missing key for activity %s", activity.activity_id)
         return
 
-    # Load followers
+    # Load followers: aggregate (app_domain IS NULL) always get everything.
+    # If the activity has an origin_app, also include app-specific followers.
+    from sqlalchemy import or_
+
+    follower_filters = [
+        APFollower.actor_profile_id == actor.id,
+    ]
+
+    origin_app = activity.origin_app
+    if origin_app and origin_app != "federation":
+        # Aggregate followers (NULL) + followers of this specific app
+        follower_filters.append(
+            or_(
+                APFollower.app_domain.is_(None),
+                APFollower.app_domain == origin_app,
+            )
+        )
+    else:
+        # Federation / no origin_app: deliver to all followers
+        pass
+
     followers = (
         await session.execute(
-            select(APFollower).where(APFollower.actor_profile_id == actor.id)
+            select(APFollower).where(*follower_filters)
         )
     ).scalars().all()
 
@@ -142,7 +162,7 @@ async def on_any_activity(activity: APActivity, session: AsyncSession) -> None:
         log.debug("No followers to deliver to for %s", activity.activity_id)
         return
 
-    # Deduplicate inboxes
+    # Deduplicate inboxes (same remote actor may follow both aggregate + app)
     all_inboxes = {f.follower_inbox for f in followers if f.follower_inbox}
 
     # Check delivery log — skip inboxes we already delivered to (idempotency)

infrastructure/activitypub.py

@@ -0,0 +1,446 @@
+"""Per-app ActivityPub blueprint.
+
+Factory function ``create_activitypub_blueprint(app_name)`` returns a
+Blueprint with WebFinger, host-meta, nodeinfo, actor profile, inbox,
+outbox, and followers endpoints.
+
+Per-app actors are *virtual projections* of the same ``ActorProfile``.
+Same keypair, same ``preferred_username`` — the only differences are:
+- the domain in URLs (e.g. blog.rose-ash.com vs federation.rose-ash.com)
+- which activities are served in the outbox (filtered by ``origin_app``)
+- which followers are returned (filtered by ``app_domain``)
+- Follow requests create ``APFollower(app_domain=app_name)``
+
+Federation app acts as the aggregate: no origin_app filter, app_domain=NULL.
+"""
+from __future__ import annotations
+
+import json
+import logging
+import os
+from datetime import datetime, timezone
+
+from quart import Blueprint, request, abort, Response, g
+from sqlalchemy import select
+
+from shared.services.registry import services
+from shared.models.federation import ActorProfile, APInboxItem
+from shared.browser.app.csrf import csrf_exempt
+
+log = logging.getLogger(__name__)
+
+AP_CONTENT_TYPE = "application/activity+json"
+
+# Apps that serve per-app AP actors
+AP_APPS = {"blog", "market", "events", "federation"}
+
+
+def _ap_domain(app_name: str) -> str:
+    """Return the public domain for this app's AP identity."""
+    env_key = f"AP_DOMAIN_{app_name.upper()}"
+    env_val = os.getenv(env_key)
+    if env_val:
+        return env_val
+    # Default: {app}.rose-ash.com, except federation uses AP_DOMAIN
+    if app_name == "federation":
+        return os.getenv("AP_DOMAIN", "federation.rose-ash.com")
+    return f"{app_name}.rose-ash.com"
+
+
+def _federation_domain() -> str:
+    """The aggregate federation domain (for alsoKnownAs links)."""
+    return os.getenv("AP_DOMAIN", "federation.rose-ash.com")
+
+
+def _is_aggregate(app_name: str) -> bool:
+    """Federation serves the aggregate actor (no per-app filter)."""
+    return app_name == "federation"
+
+
+def create_activitypub_blueprint(app_name: str) -> Blueprint:
+    """Return a Blueprint with AP endpoints for *app_name*."""
+    bp = Blueprint("activitypub", __name__)
+
+    domain = _ap_domain(app_name)
+    fed_domain = _federation_domain()
+    aggregate = _is_aggregate(app_name)
+    # For per-app follows, store app_domain; for federation aggregate, NULL
+    follower_app_domain: str | None = None if aggregate else app_name
+    # For per-app outboxes, filter by origin_app; for federation, show all
+    outbox_origin_app: str | None = None if aggregate else app_name
+
+    # ------------------------------------------------------------------
+    # Well-known endpoints
+    # ------------------------------------------------------------------
+
+    @bp.get("/.well-known/webfinger")
+    async def webfinger():
+        resource = request.args.get("resource", "")
+        if not resource.startswith("acct:"):
+            abort(400, "Invalid resource format")
+
+        parts = resource[5:].split("@")
+        if len(parts) != 2:
+            abort(400, "Invalid resource format")
+
+        username, res_domain = parts
+        if res_domain != domain:
+            abort(404, "User not on this server")
+
+        actor = await services.federation.get_actor_by_username(g.s, username)
+        if not actor:
+            abort(404, "User not found")
+
+        actor_url = f"https://{domain}/users/{username}"
+        return Response(
+            response=json.dumps({
+                "subject": resource,
+                "aliases": [actor_url],
+                "links": [
+                    {
+                        "rel": "self",
+                        "type": AP_CONTENT_TYPE,
+                        "href": actor_url,
+                    },
+                    {
+                        "rel": "http://webfinger.net/rel/profile-page",
+                        "type": "text/html",
+                        "href": actor_url,
+                    },
+                ],
+            }),
+            content_type="application/jrd+json",
+        )
+
+    @bp.get("/.well-known/nodeinfo")
+    async def nodeinfo_index():
+        return Response(
+            response=json.dumps({
+                "links": [
+                    {
+                        "rel": "http://nodeinfo.diaspora.software/ns/schema/2.0",
+                        "href": f"https://{domain}/nodeinfo/2.0",
+                    }
+                ]
+            }),
+            content_type="application/json",
+        )
+
+    @bp.get("/nodeinfo/2.0")
+    async def nodeinfo():
+        stats = await services.federation.get_stats(g.s)
+        return Response(
+            response=json.dumps({
+                "version": "2.0",
+                "software": {
+                    "name": "rose-ash",
+                    "version": "1.0.0",
+                },
+                "protocols": ["activitypub"],
+                "usage": {
+                    "users": {
+                        "total": stats.get("actors", 0),
+                        "activeMonth": stats.get("actors", 0),
+                    },
+                    "localPosts": stats.get("activities", 0),
+                },
+                "openRegistrations": False,
+                "metadata": {
+                    "nodeName": f"Rose Ash ({app_name})",
+                    "nodeDescription": f"Rose Ash {app_name} — ActivityPub federation",
+                },
+            }),
+            content_type="application/json",
+        )
+
+    @bp.get("/.well-known/host-meta")
+    async def host_meta():
+        xml = (
+            '<?xml version="1.0" encoding="UTF-8"?>\n'
+            '<XRD xmlns="http://docs.oasis-open.org/ns/xri/xrd-1.0">\n'
+            f'  <Link rel="lrdd" type="application/xrd+xml" '
+            f'template="https://{domain}/.well-known/webfinger?resource={{uri}}"/>\n'
+            '</XRD>'
+        )
+        return Response(response=xml, content_type="application/xrd+xml")
+
+    # ------------------------------------------------------------------
+    # Actor profile
+    # ------------------------------------------------------------------
+
+    @bp.get("/users/<username>")
+    async def actor_profile(username: str):
+        actor = await services.federation.get_actor_by_username(g.s, username)
+        if not actor:
+            abort(404)
+
+        accept_header = request.headers.get("accept", "")
+
+        if "application/activity+json" in accept_header or "application/ld+json" in accept_header:
+            actor_url = f"https://{domain}/users/{username}"
+            actor_json = {
+                "@context": [
+                    "https://www.w3.org/ns/activitystreams",
+                    "https://w3id.org/security/v1",
+                ],
+                "type": "Person",
+                "id": actor_url,
+                "name": actor.display_name or username,
+                "preferredUsername": username,
+                "summary": actor.summary or "",
+                "manuallyApprovesFollowers": False,
+                "inbox": f"{actor_url}/inbox",
+                "outbox": f"{actor_url}/outbox",
+                "followers": f"{actor_url}/followers",
+                "following": f"{actor_url}/following",
+                "publicKey": {
+                    "id": f"{actor_url}#main-key",
+                    "owner": actor_url,
+                    "publicKeyPem": actor.public_key_pem,
+                },
+                "url": actor_url,
+            }
+
+            # Per-app actors link back to the aggregate federation actor
+            if not aggregate and domain != fed_domain:
+                actor_json["alsoKnownAs"] = [
+                    f"https://{fed_domain}/users/{username}",
+                ]
+
+            return Response(
+                response=json.dumps(actor_json),
+                content_type=AP_CONTENT_TYPE,
+            )
+
+        # HTML: federation renders its own profile; other apps redirect there
+        if aggregate:
+            from quart import render_template
+            activities, total = await services.federation.get_outbox(
+                g.s, username, page=1, per_page=20,
+            )
+            return await render_template(
+                "federation/profile.html",
+                actor=actor,
+                activities=activities,
+                total=total,
+            )
+        from quart import redirect
+        return redirect(f"https://{fed_domain}/users/{username}")
+
+    # ------------------------------------------------------------------
+    # Inbox
+    # ------------------------------------------------------------------
+
+    @csrf_exempt
+    @bp.post("/users/<username>/inbox")
+    async def inbox(username: str):
+        actor = await services.federation.get_actor_by_username(g.s, username)
+        if not actor:
+            abort(404)
+
+        body = await request.get_json()
+        if not body:
+            abort(400, "Invalid JSON")
+
+        activity_type = body.get("type", "")
+        from_actor_url = body.get("actor", "")
+
+        # Verify HTTP signature (best-effort)
+        sig_valid = False
+        try:
+            from shared.utils.http_signatures import verify_request_signature
+            from shared.infrastructure.ap_inbox_handlers import fetch_remote_actor
+
+            req_headers = dict(request.headers)
+            sig_header = req_headers.get("Signature", "")
+
+            remote_actor = await fetch_remote_actor(from_actor_url)
+            if remote_actor and sig_header:
+                pub_key_pem = (remote_actor.get("publicKey") or {}).get("publicKeyPem")
+                if pub_key_pem:
+                    sig_valid = verify_request_signature(
+                        public_key_pem=pub_key_pem,
+                        signature_header=sig_header,
+                        method="POST",
+                        path=f"/users/{username}/inbox",
+                        headers=req_headers,
+                    )
+        except Exception:
+            log.debug("Signature verification failed for %s", from_actor_url, exc_info=True)
+
+        if not sig_valid:
+            log.warning(
+                "Unverified inbox POST from %s (%s) on %s — accepting anyway for now",
+                from_actor_url, activity_type, domain,
+            )
+
+        # Load actor row for DB operations
+        actor_row = (
+            await g.s.execute(
+                select(ActorProfile).where(
+                    ActorProfile.preferred_username == username
+                )
+            )
+        ).scalar_one()
+
+        # Store raw inbox item
+        item = APInboxItem(
+            actor_profile_id=actor_row.id,
+            raw_json=body,
+            activity_type=activity_type,
+            from_actor=from_actor_url,
+        )
+        g.s.add(item)
+        await g.s.flush()
+
+        # Dispatch to shared handlers
+        from shared.infrastructure.ap_inbox_handlers import dispatch_inbox_activity
+        await dispatch_inbox_activity(
+            g.s, actor_row, body, from_actor_url,
+            domain=domain,
+            app_domain=follower_app_domain,
+        )
+
+        # Mark as processed
+        item.state = "processed"
+        item.processed_at = datetime.now(timezone.utc)
+        await g.s.flush()
+
+        return Response(status=202)
+
+    # ------------------------------------------------------------------
+    # Outbox
+    # ------------------------------------------------------------------
+
+    @bp.get("/users/<username>/outbox")
+    async def outbox(username: str):
+        actor = await services.federation.get_actor_by_username(g.s, username)
+        if not actor:
+            abort(404)
+
+        actor_url = f"https://{domain}/users/{username}"
+        page_param = request.args.get("page")
+
+        if not page_param:
+            _, total = await services.federation.get_outbox(
+                g.s, username, page=1, per_page=1,
+                origin_app=outbox_origin_app,
+            )
+            return Response(
+                response=json.dumps({
+                    "@context": "https://www.w3.org/ns/activitystreams",
+                    "type": "OrderedCollection",
+                    "id": f"{actor_url}/outbox",
+                    "totalItems": total,
+                    "first": f"{actor_url}/outbox?page=1",
+                }),
+                content_type=AP_CONTENT_TYPE,
+            )
+
+        page_num = int(page_param)
+        activities, total = await services.federation.get_outbox(
+            g.s, username, page=page_num, per_page=20,
+            origin_app=outbox_origin_app,
+        )
+
+        items = []
+        for a in activities:
+            items.append({
+                "@context": "https://www.w3.org/ns/activitystreams",
+                "type": a.activity_type,
+                "id": a.activity_id,
+                "actor": actor_url,
+                "published": a.published.isoformat() if a.published else None,
+                "object": {
+                    "type": a.object_type,
+                    **(a.object_data or {}),
+                },
+            })
+
+        return Response(
+            response=json.dumps({
+                "@context": "https://www.w3.org/ns/activitystreams",
+                "type": "OrderedCollectionPage",
+                "id": f"{actor_url}/outbox?page={page_num}",
+                "partOf": f"{actor_url}/outbox",
+                "totalItems": total,
+                "orderedItems": items,
+            }),
+            content_type=AP_CONTENT_TYPE,
+        )
+
+    # ------------------------------------------------------------------
+    # Followers / following collections
+    # ------------------------------------------------------------------
+
+    @bp.get("/users/<username>/followers")
+    async def followers(username: str):
+        actor = await services.federation.get_actor_by_username(g.s, username)
+        if not actor:
+            abort(404)
+
+        collection_id = f"https://{domain}/users/{username}/followers"
+        follower_list = await services.federation.get_followers(
+            g.s, username, app_domain=follower_app_domain,
+        )
+        page_param = request.args.get("page")
+
+        if not page_param:
+            return Response(
+                response=json.dumps({
+                    "@context": "https://www.w3.org/ns/activitystreams",
+                    "type": "OrderedCollection",
+                    "id": collection_id,
+                    "totalItems": len(follower_list),
+                    "first": f"{collection_id}?page=1",
+                }),
+                content_type=AP_CONTENT_TYPE,
+            )
+
+        return Response(
+            response=json.dumps({
+                "@context": "https://www.w3.org/ns/activitystreams",
+                "type": "OrderedCollectionPage",
+                "id": f"{collection_id}?page=1",
+                "partOf": collection_id,
+                "totalItems": len(follower_list),
+                "orderedItems": [f.follower_actor_url for f in follower_list],
+            }),
+            content_type=AP_CONTENT_TYPE,
+        )
+
+    @bp.get("/users/<username>/following")
+    async def following(username: str):
+        actor = await services.federation.get_actor_by_username(g.s, username)
+        if not actor:
+            abort(404)
+
+        collection_id = f"https://{domain}/users/{username}/following"
+        following_list, total = await services.federation.get_following(g.s, username)
+        page_param = request.args.get("page")
+
+        if not page_param:
+            return Response(
+                response=json.dumps({
+                    "@context": "https://www.w3.org/ns/activitystreams",
+                    "type": "OrderedCollection",
+                    "id": collection_id,
+                    "totalItems": total,
+                    "first": f"{collection_id}?page=1",
+                }),
+                content_type=AP_CONTENT_TYPE,
+            )
+
+        return Response(
+            response=json.dumps({
+                "@context": "https://www.w3.org/ns/activitystreams",
+                "type": "OrderedCollectionPage",
+                "id": f"{collection_id}?page=1",
+                "partOf": collection_id,
+                "totalItems": total,
+                "orderedItems": [f.actor_url for f in following_list],
+            }),
+            content_type=AP_CONTENT_TYPE,
+        )
+
+    return bp

infrastructure/ap_inbox_handlers.py

@@ -0,0 +1,508 @@
+"""Reusable AP inbox handlers for all apps.
+
+Extracted from federation/bp/actors/routes.py so that every app's
+shared AP blueprint can process Follow, Undo, Accept, Create, etc.
+"""
+from __future__ import annotations
+
+import json
+import logging
+import uuid
+from datetime import datetime, timezone
+
+import httpx
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from shared.models.federation import (
+    ActorProfile, APInboxItem, APInteraction, APNotification,
+    APRemotePost, APActivity, RemoteActor,
+)
+from shared.services.registry import services
+
+log = logging.getLogger(__name__)
+
+AP_CONTENT_TYPE = "application/activity+json"
+
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+async def fetch_remote_actor(actor_url: str) -> dict | None:
+    """Fetch a remote actor's JSON-LD profile."""
+    try:
+        async with httpx.AsyncClient(timeout=10) as client:
+            resp = await client.get(
+                actor_url,
+                headers={"Accept": AP_CONTENT_TYPE},
+            )
+            if resp.status_code == 200:
+                return resp.json()
+    except Exception:
+        log.exception("Failed to fetch remote actor: %s", actor_url)
+    return None
+
+
+async def send_accept(
+    actor: ActorProfile,
+    follow_activity: dict,
+    follower_inbox: str,
+    domain: str,
+) -> None:
+    """Send an Accept activity back to the follower."""
+    from shared.utils.http_signatures import sign_request
+    from urllib.parse import urlparse
+
+    username = actor.preferred_username
+    actor_url = f"https://{domain}/users/{username}"
+
+    accept_id = f"{actor_url}/activities/{uuid.uuid4()}"
+    accept = {
+        "@context": "https://www.w3.org/ns/activitystreams",
+        "id": accept_id,
+        "type": "Accept",
+        "actor": actor_url,
+        "object": follow_activity,
+    }
+
+    body_bytes = json.dumps(accept).encode()
+    key_id = f"{actor_url}#main-key"
+
+    parsed = urlparse(follower_inbox)
+    headers = sign_request(
+        private_key_pem=actor.private_key_pem,
+        key_id=key_id,
+        method="POST",
+        path=parsed.path,
+        host=parsed.netloc,
+        body=body_bytes,
+    )
+    headers["Content-Type"] = AP_CONTENT_TYPE
+
+    try:
+        async with httpx.AsyncClient(timeout=15) as client:
+            resp = await client.post(
+                follower_inbox,
+                content=body_bytes,
+                headers=headers,
+            )
+            log.info("Accept → %s: %d", follower_inbox, resp.status_code)
+    except Exception:
+        log.exception("Failed to send Accept to %s", follower_inbox)
+
+
+async def backfill_follower(
+    session: AsyncSession,
+    actor: ActorProfile,
+    follower_inbox: str,
+    domain: str,
+    origin_app: str | None = None,
+) -> None:
+    """Deliver recent Create activities to a new follower's inbox."""
+    from shared.events.handlers.ap_delivery_handler import (
+        _build_activity_json, _deliver_to_inbox,
+    )
+
+    filters = [
+        APActivity.actor_profile_id == actor.id,
+        APActivity.is_local == True,  # noqa: E712
+        APActivity.activity_type == "Create",
+    ]
+    if origin_app is not None:
+        filters.append(APActivity.origin_app == origin_app)
+
+    activities = (
+        await session.execute(
+            select(APActivity).where(*filters)
+            .order_by(APActivity.published.desc())
+            .limit(20)
+        )
+    ).scalars().all()
+
+    if not activities:
+        return
+
+    log.info(
+        "Backfilling %d posts to %s for @%s",
+        len(activities), follower_inbox, actor.preferred_username,
+    )
+
+    async with httpx.AsyncClient() as client:
+        for activity in reversed(activities):  # oldest first
+            activity_json = _build_activity_json(activity, actor, domain)
+            await _deliver_to_inbox(client, follower_inbox, activity_json, actor, domain)
+
+
+# ---------------------------------------------------------------------------
+# Inbox activity handlers
+# ---------------------------------------------------------------------------
+
+async def handle_follow(
+    session: AsyncSession,
+    actor_row: ActorProfile,
+    body: dict,
+    from_actor_url: str,
+    domain: str,
+    app_domain: str | None = None,
+) -> None:
+    """Process a Follow activity: add follower, send Accept, backfill."""
+    remote_actor = await fetch_remote_actor(from_actor_url)
+    if not remote_actor:
+        log.warning("Could not fetch remote actor for Follow: %s", from_actor_url)
+        return
+
+    follower_inbox = remote_actor.get("inbox")
+    if not follower_inbox:
+        log.warning("Remote actor has no inbox: %s", from_actor_url)
+        return
+
+    remote_username = remote_actor.get("preferredUsername", "")
+    from urllib.parse import urlparse
+    remote_domain = urlparse(from_actor_url).netloc
+    follower_acct = f"{remote_username}@{remote_domain}" if remote_username else from_actor_url
+
+    pub_key = (remote_actor.get("publicKey") or {}).get("publicKeyPem")
+
+    await services.federation.add_follower(
+        session,
+        actor_row.preferred_username,
+        follower_acct=follower_acct,
+        follower_inbox=follower_inbox,
+        follower_actor_url=from_actor_url,
+        follower_public_key=pub_key,
+        app_domain=app_domain,
+    )
+
+    log.info(
+        "New follower: %s → @%s (app_domain=%s)",
+        follower_acct, actor_row.preferred_username, app_domain,
+    )
+
+    # Notification
+    ra = (
+        await session.execute(
+            select(RemoteActor).where(RemoteActor.actor_url == from_actor_url)
+        )
+    ).scalar_one_or_none()
+    if not ra:
+        ra_dto = await services.federation.get_or_fetch_remote_actor(session, from_actor_url)
+        if ra_dto:
+            ra = (await session.execute(
+                select(RemoteActor).where(RemoteActor.actor_url == from_actor_url)
+            )).scalar_one_or_none()
+
+    if ra:
+        notif = APNotification(
+            actor_profile_id=actor_row.id,
+            notification_type="follow",
+            from_remote_actor_id=ra.id,
+        )
+        session.add(notif)
+
+    # Send Accept
+    await send_accept(actor_row, body, follower_inbox, domain)
+
+    # Backfill: deliver recent posts (filtered by origin_app for per-app follows)
+    origin_app = app_domain if app_domain and app_domain != "federation" else None
+    await backfill_follower(session, actor_row, follower_inbox, domain, origin_app=origin_app)
+
+
+async def handle_undo(
+    session: AsyncSession,
+    actor_row: ActorProfile,
+    body: dict,
+    from_actor_url: str,
+    app_domain: str | None = None,
+) -> None:
+    """Process an Undo activity (typically Undo Follow)."""
+    inner = body.get("object")
+    if not inner:
+        return
+
+    inner_type = inner.get("type") if isinstance(inner, dict) else None
+    if inner_type == "Follow":
+        from urllib.parse import urlparse
+        remote_domain = urlparse(from_actor_url).netloc
+        remote_actor = await fetch_remote_actor(from_actor_url)
+        remote_username = ""
+        if remote_actor:
+            remote_username = remote_actor.get("preferredUsername", "")
+        follower_acct = f"{remote_username}@{remote_domain}" if remote_username else from_actor_url
+
+        removed = await services.federation.remove_follower(
+            session, actor_row.preferred_username, follower_acct,
+            app_domain=app_domain,
+        )
+        if removed:
+            log.info("Unfollowed: %s → @%s (app_domain=%s)", follower_acct, actor_row.preferred_username, app_domain)
+        else:
+            log.debug("Undo Follow: follower not found: %s", follower_acct)
+    else:
+        log.debug("Undo for %s — not handled", inner_type)
+
+
+async def handle_accept(
+    session: AsyncSession,
+    actor_row: ActorProfile,
+    body: dict,
+    from_actor_url: str,
+) -> None:
+    """Process Accept activity — update outbound follow state."""
+    inner = body.get("object")
+    if not inner:
+        return
+
+    inner_type = inner.get("type") if isinstance(inner, dict) else None
+    if inner_type == "Follow":
+        await services.federation.accept_follow_response(
+            session, actor_row.preferred_username, from_actor_url,
+        )
+        log.info("Follow accepted by %s for @%s", from_actor_url, actor_row.preferred_username)
+
+
+async def handle_create(
+    session: AsyncSession,
+    actor_row: ActorProfile,
+    body: dict,
+    from_actor_url: str,
+    federation_domain: str,
+) -> None:
+    """Process Create(Note/Article) — ingest remote post."""
+    obj = body.get("object")
+    if not obj or not isinstance(obj, dict):
+        return
+
+    obj_type = obj.get("type", "")
+    if obj_type not in ("Note", "Article"):
+        log.debug("Create with type %s — skipping", obj_type)
+        return
+
+    remote = await services.federation.get_or_fetch_remote_actor(session, from_actor_url)
+    if not remote:
+        log.warning("Could not resolve remote actor for Create: %s", from_actor_url)
+        return
+
+    await services.federation.ingest_remote_post(session, remote.id, body, obj)
+    log.info("Ingested %s from %s", obj_type, from_actor_url)
+
+    # Mention notification
+    tags = obj.get("tag", [])
+    if isinstance(tags, list):
+        for tag in tags:
+            if not isinstance(tag, dict):
+                continue
+            if tag.get("type") != "Mention":
+                continue
+            href = tag.get("href", "")
+            if f"https://{federation_domain}/users/" in href:
+                mentioned_username = href.rsplit("/", 1)[-1]
+                mentioned = await services.federation.get_actor_by_username(
+                    session, mentioned_username,
+                )
+                if mentioned:
+                    rp = (await session.execute(
+                        select(APRemotePost).where(
+                            APRemotePost.object_id == obj.get("id")
+                        )
+                    )).scalar_one_or_none()
+
+                    ra = (await session.execute(
+                        select(RemoteActor).where(RemoteActor.actor_url == from_actor_url)
+                    )).scalar_one_or_none()
+
+                    notif = APNotification(
+                        actor_profile_id=mentioned.id,
+                        notification_type="mention",
+                        from_remote_actor_id=ra.id if ra else None,
+                        target_remote_post_id=rp.id if rp else None,
+                    )
+                    session.add(notif)
+
+    # Reply notification
+    in_reply_to = obj.get("inReplyTo")
+    if in_reply_to and f"https://{federation_domain}/users/" in str(in_reply_to):
+        local_activity = (await session.execute(
+            select(APActivity).where(
+                APActivity.activity_id == in_reply_to,
+            )
+        )).scalar_one_or_none()
+        if local_activity:
+            ra = (await session.execute(
+                select(RemoteActor).where(RemoteActor.actor_url == from_actor_url)
+            )).scalar_one_or_none()
+            rp = (await session.execute(
+                select(APRemotePost).where(
+                    APRemotePost.object_id == obj.get("id")
+                )
+            )).scalar_one_or_none()
+
+            notif = APNotification(
+                actor_profile_id=local_activity.actor_profile_id,
+                notification_type="reply",
+                from_remote_actor_id=ra.id if ra else None,
+                target_remote_post_id=rp.id if rp else None,
+            )
+            session.add(notif)
+
+
+async def handle_update(
+    session: AsyncSession,
+    actor_row: ActorProfile,
+    body: dict,
+    from_actor_url: str,
+) -> None:
+    """Process Update — re-ingest remote post."""
+    obj = body.get("object")
+    if not obj or not isinstance(obj, dict):
+        return
+    obj_type = obj.get("type", "")
+    if obj_type in ("Note", "Article"):
+        remote = await services.federation.get_or_fetch_remote_actor(session, from_actor_url)
+        if remote:
+            await services.federation.ingest_remote_post(session, remote.id, body, obj)
+            log.info("Updated %s from %s", obj_type, from_actor_url)
+
+
+async def handle_delete(
+    session: AsyncSession,
+    actor_row: ActorProfile,
+    body: dict,
+    from_actor_url: str,
+) -> None:
+    """Process Delete — remove remote post."""
+    obj = body.get("object")
+    if isinstance(obj, str):
+        object_id = obj
+    elif isinstance(obj, dict):
+        object_id = obj.get("id", "")
+    else:
+        return
+    if object_id:
+        await services.federation.delete_remote_post(session, object_id)
+        log.info("Deleted remote post %s from %s", object_id, from_actor_url)
+
+
+async def handle_like(
+    session: AsyncSession,
+    actor_row: ActorProfile,
+    body: dict,
+    from_actor_url: str,
+) -> None:
+    """Process incoming Like — record interaction + notify."""
+    object_id = body.get("object", "")
+    if isinstance(object_id, dict):
+        object_id = object_id.get("id", "")
+    if not object_id:
+        return
+
+    remote = await services.federation.get_or_fetch_remote_actor(session, from_actor_url)
+    if not remote:
+        return
+
+    ra = (await session.execute(
+        select(RemoteActor).where(RemoteActor.actor_url == from_actor_url)
+    )).scalar_one_or_none()
+
+    target = (await session.execute(
+        select(APActivity).where(APActivity.activity_id == object_id)
+    )).scalar_one_or_none()
+
+    if not target:
+        log.info("Like from %s for %s (target not found locally)", from_actor_url, object_id)
+        return
+
+    interaction = APInteraction(
+        remote_actor_id=ra.id if ra else None,
+        post_type="local",
+        post_id=target.id,
+        interaction_type="like",
+        activity_id=body.get("id"),
+    )
+    session.add(interaction)
+
+    notif = APNotification(
+        actor_profile_id=target.actor_profile_id,
+        notification_type="like",
+        from_remote_actor_id=ra.id if ra else None,
+        target_activity_id=target.id,
+    )
+    session.add(notif)
+    log.info("Like from %s on activity %s", from_actor_url, object_id)
+
+
+async def handle_announce(
+    session: AsyncSession,
+    actor_row: ActorProfile,
+    body: dict,
+    from_actor_url: str,
+) -> None:
+    """Process incoming Announce (boost) — record interaction + notify."""
+    object_id = body.get("object", "")
+    if isinstance(object_id, dict):
+        object_id = object_id.get("id", "")
+    if not object_id:
+        return
+
+    remote = await services.federation.get_or_fetch_remote_actor(session, from_actor_url)
+    if not remote:
+        return
+
+    ra = (await session.execute(
+        select(RemoteActor).where(RemoteActor.actor_url == from_actor_url)
+    )).scalar_one_or_none()
+
+    target = (await session.execute(
+        select(APActivity).where(APActivity.activity_id == object_id)
+    )).scalar_one_or_none()
+
+    if not target:
+        log.info("Announce from %s for %s (target not found locally)", from_actor_url, object_id)
+        return
+
+    interaction = APInteraction(
+        remote_actor_id=ra.id if ra else None,
+        post_type="local",
+        post_id=target.id,
+        interaction_type="boost",
+        activity_id=body.get("id"),
+    )
+    session.add(interaction)
+
+    notif = APNotification(
+        actor_profile_id=target.actor_profile_id,
+        notification_type="boost",
+        from_remote_actor_id=ra.id if ra else None,
+        target_activity_id=target.id,
+    )
+    session.add(notif)
+    log.info("Announce from %s on activity %s", from_actor_url, object_id)
+
+
+async def dispatch_inbox_activity(
+    session: AsyncSession,
+    actor_row: ActorProfile,
+    body: dict,
+    from_actor_url: str,
+    domain: str,
+    app_domain: str | None = None,
+) -> None:
+    """Route an inbox activity to the correct handler."""
+    activity_type = body.get("type", "")
+
+    if activity_type == "Follow":
+        await handle_follow(session, actor_row, body, from_actor_url, domain, app_domain=app_domain)
+    elif activity_type == "Undo":
+        await handle_undo(session, actor_row, body, from_actor_url, app_domain=app_domain)
+    elif activity_type == "Accept":
+        await handle_accept(session, actor_row, body, from_actor_url)
+    elif activity_type == "Create":
+        await handle_create(session, actor_row, body, from_actor_url, domain)
+    elif activity_type == "Update":
+        await handle_update(session, actor_row, body, from_actor_url)
+    elif activity_type == "Delete":
+        await handle_delete(session, actor_row, body, from_actor_url)
+    elif activity_type == "Like":
+        await handle_like(session, actor_row, body, from_actor_url)
+    elif activity_type == "Announce":
+        await handle_announce(session, actor_row, body, from_actor_url)

infrastructure/factory.py

@@ -108,6 +108,12 @@ def create_base_app(
         from shared.infrastructure.oauth import create_oauth_blueprint
         app.register_blueprint(create_oauth_blueprint(name))
 
+    # Auto-register ActivityPub blueprint for AP-enabled apps
+    from shared.infrastructure.activitypub import AP_APPS
+    if name in AP_APPS:
+        from shared.infrastructure.activitypub import create_activitypub_blueprint
+        app.register_blueprint(create_activitypub_blueprint(name))
+
     # --- device id (all apps, including account) ---
     _did_cookie = f"{name}_did"
 

models/federation.py

@@ -127,7 +127,11 @@ class APActivity(Base):
 
 
 class APFollower(Base):
-    """A remote follower of a local actor."""
+    """A remote follower of a local actor.
+
+    ``app_domain`` scopes the follow to a specific app (e.g. "blog").
+    NULL means the follower subscribes to the aggregate (all activities).
+    """
     __tablename__ = "ap_followers"
 
     id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
@@ -138,6 +142,7 @@ class APFollower(Base):
     follower_inbox: Mapped[str] = mapped_column(String(512), nullable=False)
     follower_actor_url: Mapped[str] = mapped_column(String(512), nullable=False)
     follower_public_key: Mapped[str | None] = mapped_column(Text, nullable=True)
+    app_domain: Mapped[str | None] = mapped_column(String(64), nullable=True)
     created_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True), nullable=False, server_default=func.now(),
     )
@@ -146,8 +151,12 @@ class APFollower(Base):
     actor_profile = relationship("ActorProfile", back_populates="followers")
 
     __table_args__ = (
-        UniqueConstraint("actor_profile_id", "follower_acct", name="uq_follower_acct"),
+        UniqueConstraint(
+            "actor_profile_id", "follower_acct", "app_domain",
+            name="uq_follower_acct_app",
+        ),
         Index("ix_ap_follower_actor", "actor_profile_id"),
+        Index("ix_ap_follower_app_domain", "actor_profile_id", "app_domain"),
     )
 
     def __repr__(self) -> str:

services/federation_impl.py

@@ -75,6 +75,7 @@ def _follower_to_dto(f: APFollower) -> APFollowerDTO:
         follower_inbox=f.follower_inbox,
         follower_actor_url=f.follower_actor_url,
         created_at=f.created_at,
+        app_domain=f.app_domain,
     )
 
 
@@ -252,6 +253,7 @@ class SqlFederationService:
     async def get_outbox(
         self, session: AsyncSession, username: str,
         page: int = 1, per_page: int = 20,
+        origin_app: str | None = None,
     ) -> tuple[list[APActivityDTO], int]:
         actor = (
             await session.execute(
@@ -261,22 +263,23 @@ class SqlFederationService:
         if actor is None:
             return [], 0
 
+        filters = [
+            APActivity.actor_profile_id == actor.id,
+            APActivity.is_local == True,  # noqa: E712
+        ]
+        if origin_app is not None:
+            filters.append(APActivity.origin_app == origin_app)
+
         total = (
             await session.execute(
-                select(func.count(APActivity.id)).where(
-                    APActivity.actor_profile_id == actor.id,
-                    APActivity.is_local == True,  # noqa: E712
-                )
+                select(func.count(APActivity.id)).where(*filters)
             )
         ).scalar() or 0
 
         offset = (page - 1) * per_page
         result = await session.execute(
             select(APActivity)
-            .where(
-                APActivity.actor_profile_id == actor.id,
-                APActivity.is_local == True,  # noqa: E712
-            )
+            .where(*filters)
             .order_by(APActivity.published.desc())
             .limit(per_page)
             .offset(offset)
@@ -315,6 +318,7 @@ class SqlFederationService:
 
     async def get_followers(
         self, session: AsyncSession, username: str,
+        app_domain: str | None = None,
     ) -> list[APFollowerDTO]:
         actor = (
             await session.execute(
@@ -324,15 +328,18 @@ class SqlFederationService:
         if actor is None:
             return []
 
-        result = await session.execute(
-            select(APFollower).where(APFollower.actor_profile_id == actor.id)
-        )
+        q = select(APFollower).where(APFollower.actor_profile_id == actor.id)
+        if app_domain is not None:
+            q = q.where(APFollower.app_domain == app_domain)
+
+        result = await session.execute(q)
         return [_follower_to_dto(f) for f in result.scalars().all()]
 
     async def add_follower(
         self, session: AsyncSession, username: str,
         follower_acct: str, follower_inbox: str, follower_actor_url: str,
         follower_public_key: str | None = None,
+        app_domain: str | None = None,
     ) -> APFollowerDTO:
         actor = (
             await session.execute(
@@ -342,15 +349,17 @@ class SqlFederationService:
         if actor is None:
             raise ValueError(f"Actor not found: {username}")
 
-        # Upsert: update if already following, insert if new
-        existing = (
-            await session.execute(
-                select(APFollower).where(
-                    APFollower.actor_profile_id == actor.id,
-                    APFollower.follower_acct == follower_acct,
-                )
-            )
-        ).scalar_one_or_none()
+        # Upsert: update if already following this (actor, acct, app_domain)
+        q = select(APFollower).where(
+            APFollower.actor_profile_id == actor.id,
+            APFollower.follower_acct == follower_acct,
+        )
+        if app_domain is not None:
+            q = q.where(APFollower.app_domain == app_domain)
+        else:
+            q = q.where(APFollower.app_domain.is_(None))
+
+        existing = (await session.execute(q)).scalar_one_or_none()
 
         if existing:
             existing.follower_inbox = follower_inbox
@@ -365,6 +374,7 @@ class SqlFederationService:
             follower_inbox=follower_inbox,
             follower_actor_url=follower_actor_url,
             follower_public_key=follower_public_key,
+            app_domain=app_domain,
         )
         session.add(follower)
         await session.flush()
@@ -372,6 +382,7 @@ class SqlFederationService:
 
     async def remove_follower(
         self, session: AsyncSession, username: str, follower_acct: str,
+        app_domain: str | None = None,
     ) -> bool:
         actor = (
             await session.execute(
@@ -381,12 +392,16 @@ class SqlFederationService:
         if actor is None:
             return False
 
-        result = await session.execute(
-            delete(APFollower).where(
-                APFollower.actor_profile_id == actor.id,
-                APFollower.follower_acct == follower_acct,
-            )
-        )
+        filters = [
+            APFollower.actor_profile_id == actor.id,
+            APFollower.follower_acct == follower_acct,
+        ]
+        if app_domain is not None:
+            filters.append(APFollower.app_domain == app_domain)
+        else:
+            filters.append(APFollower.app_domain.is_(None))
+
+        result = await session.execute(delete(APFollower).where(*filters))
         return result.rowcount > 0
 
     async def get_followers_paginated(

services/stubs.py

@@ -221,7 +221,7 @@ class StubFederationService:
     async def get_activity(self, session, activity_id):
         return None
 
-    async def get_outbox(self, session, username, page=1, per_page=20):
+    async def get_outbox(self, session, username, page=1, per_page=20, origin_app=None):
         return [], 0
 
     async def get_activity_for_source(self, session, source_type, source_id):
@@ -230,14 +230,15 @@ class StubFederationService:
     async def count_activities_for_source(self, session, source_type, source_id, *, activity_type):
         return 0
 
-    async def get_followers(self, session, username):
+    async def get_followers(self, session, username, app_domain=None):
         return []
 
     async def add_follower(self, session, username, follower_acct, follower_inbox,
-                           follower_actor_url, follower_public_key=None):
+                           follower_actor_url, follower_public_key=None,
+                           app_domain=None):
         raise RuntimeError("FederationService not available")
 
-    async def remove_follower(self, session, username, follower_acct):
+    async def remove_follower(self, session, username, follower_acct, app_domain=None):
         return False
 
     async def get_or_fetch_remote_actor(self, session, actor_url):