activity-pub implementation

2026-05-08 21:26:50 +02:00
parent 940c33047c
commit df71748897
50 changed files with 2724 additions and 97 deletions
--- a/crates/adapters/activitypub/Cargo.toml
+++ b/crates/adapters/activitypub/Cargo.toml
@@ -0,0 +1,24 @@
+[package]
+name = "activitypub"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+domain = { workspace = true }
+application = { workspace = true }
+tokio = { workspace = true }
+serde = { workspace = true }
+serde_json = { workspace = true }
+reqwest = { workspace = true }
+uuid = { workspace = true }
+chrono = { workspace = true }
+thiserror = { workspace = true }
+anyhow = { workspace = true }
+tracing = { workspace = true }
+async-trait = { workspace = true }
+event-publisher = { workspace = true }
+
+activitypub_federation = "0.7.0-beta.11"
+url = { version = "2", features = ["serde"] }
+enum_delegate = "0.2"
+axum = "0.8"
--- a/crates/adapters/activitypub/src/activities.rs
+++ b/crates/adapters/activitypub/src/activities.rs
@@ -0,0 +1,314 @@
+use activitypub_federation::{
+    config::Data,
+    fetch::object_id::ObjectId,
+    kinds::activity::{AcceptType, CreateType, DeleteType, FollowType, RejectType, UndoType},
+    traits::{Activity, Actor, Object},
+};
+use serde::{Deserialize, Serialize};
+use url::Url;
+
+use crate::actors::DbActor;
+use crate::data::FederationData;
+use crate::error::Error;
+use crate::objects::{DbReview, ReviewObject};
+use crate::repository::FollowerStatus;
+
+// --- Follow ---
+
+#[derive(Debug, Clone, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct FollowActivity {
+    pub(crate) id: Url,
+    #[serde(rename = "type")]
+    pub(crate) kind: FollowType,
+    pub(crate) actor: ObjectId<DbActor>,
+    pub(crate) object: ObjectId<DbActor>,
+}
+
+#[async_trait::async_trait]
+impl Activity for FollowActivity {
+    type DataType = FederationData;
+    type Error = Error;
+
+    fn id(&self) -> &Url {
+        &self.id
+    }
+
+    fn actor(&self) -> &Url {
+        self.actor.inner()
+    }
+
+    async fn verify(&self, data: &Data<Self::DataType>) -> Result<(), Self::Error> {
+        // Verify the target is a local actor
+        let target_url = self.object.inner();
+        if target_url.domain() != Some(&data.domain) {
+            return Err(Error(anyhow::anyhow!(
+                "follow target is not a local actor"
+            )));
+        }
+        Ok(())
+    }
+
+    async fn receive(self, data: &Data<Self::DataType>) -> Result<(), Self::Error> {
+        let follower = self.actor.dereference(data).await?;
+        let local_actor = self.object.dereference(data).await?;
+
+        data.federation_repo
+            .add_follower(
+                local_actor.user_id.clone(),
+                self.actor.inner().as_str(),
+                FollowerStatus::Accepted,
+            )
+            .await?;
+
+        // Send Accept back
+        let accept_id =
+            Url::parse(&format!("{}/activities/{}", data.base_url, uuid::Uuid::new_v4()))
+                .expect("valid url");
+        let accept = AcceptActivity {
+            id: accept_id,
+            kind: Default::default(),
+            actor: self.object.clone(),
+            object: self.clone(),
+        };
+
+        use activitypub_federation::activity_sending::SendActivityTask;
+        use activitypub_federation::protocol::context::WithContext;
+
+        let accept_with_ctx = WithContext::new_default(accept);
+        let sends =
+            SendActivityTask::prepare(&accept_with_ctx, &local_actor, vec![follower.inbox()], data)
+                .await?;
+        for send in sends {
+            send.sign_and_send(data).await?;
+        }
+
+        tracing::info!(
+            follower = %self.actor.inner(),
+            local_user = %local_actor.user_id.value(),
+            "accepted follow"
+        );
+
+        Ok(())
+    }
+}
+
+// --- Accept ---
+
+#[derive(Debug, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct AcceptActivity {
+    pub(crate) id: Url,
+    #[serde(rename = "type")]
+    pub(crate) kind: AcceptType,
+    pub(crate) actor: ObjectId<DbActor>,
+    pub(crate) object: FollowActivity,
+}
+
+#[async_trait::async_trait]
+impl Activity for AcceptActivity {
+    type DataType = FederationData;
+    type Error = Error;
+
+    fn id(&self) -> &Url {
+        &self.id
+    }
+
+    fn actor(&self) -> &Url {
+        self.actor.inner()
+    }
+
+    async fn verify(&self, _data: &Data<Self::DataType>) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    async fn receive(self, _data: &Data<Self::DataType>) -> Result<(), Self::Error> {
+        let remote_actor_url = self.actor.into_inner().to_string();
+        tracing::info!(remote_actor_url = %remote_actor_url, "Follow accepted by remote instance");
+        // TODO(ap): update ap_following to track accepted status
+        Ok(())
+    }
+}
+
+// --- Reject ---
+
+#[derive(Debug, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct RejectActivity {
+    pub(crate) id: Url,
+    #[serde(rename = "type")]
+    pub(crate) kind: RejectType,
+    pub(crate) actor: ObjectId<DbActor>,
+    pub(crate) object: FollowActivity,
+}
+
+#[async_trait::async_trait]
+impl Activity for RejectActivity {
+    type DataType = FederationData;
+    type Error = Error;
+
+    fn id(&self) -> &Url {
+        &self.id
+    }
+
+    fn actor(&self) -> &Url {
+        self.actor.inner()
+    }
+
+    async fn verify(&self, _data: &Data<Self::DataType>) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    async fn receive(self, data: &Data<Self::DataType>) -> Result<(), Self::Error> {
+        // The actor rejected our follow. Extract the local user from the original Follow's actor.
+        let local_user_url = self.object.actor.inner();
+        let path = local_user_url.path();
+        if let Some(uid_str) = path.strip_prefix("/users/").and_then(|s| s.split('/').next()) {
+            if let Ok(uuid) = uuid::Uuid::parse_str(uid_str) {
+                let user_id = domain::value_objects::UserId::from_uuid(uuid);
+                data.federation_repo
+                    .remove_following(user_id, self.actor.inner().as_str())
+                    .await?;
+            }
+        }
+        tracing::info!(actor = %self.actor.inner(), "follow rejected");
+        Ok(())
+    }
+}
+
+// --- Undo ---
+
+#[derive(Debug, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct UndoActivity {
+    pub(crate) id: Url,
+    #[serde(rename = "type")]
+    pub(crate) kind: UndoType,
+    pub(crate) actor: ObjectId<DbActor>,
+    pub(crate) object: FollowActivity,
+}
+
+#[async_trait::async_trait]
+impl Activity for UndoActivity {
+    type DataType = FederationData;
+    type Error = Error;
+
+    fn id(&self) -> &Url {
+        &self.id
+    }
+
+    fn actor(&self) -> &Url {
+        self.actor.inner()
+    }
+
+    async fn verify(&self, _data: &Data<Self::DataType>) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    async fn receive(self, data: &Data<Self::DataType>) -> Result<(), Self::Error> {
+        // Remote actor is unfollowing a local user
+        let local_user_url = self.object.object.inner();
+        let path = local_user_url.path();
+        if let Some(uid_str) = path.strip_prefix("/users/").and_then(|s| s.split('/').next()) {
+            if let Ok(uuid) = uuid::Uuid::parse_str(uid_str) {
+                let user_id = domain::value_objects::UserId::from_uuid(uuid);
+                data.federation_repo
+                    .remove_follower(user_id, self.actor.inner().as_str())
+                    .await?;
+            }
+        }
+        tracing::info!(actor = %self.actor.inner(), "unfollowed");
+        Ok(())
+    }
+}
+
+// --- Create ---
+
+#[derive(Debug, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct CreateActivity {
+    pub(crate) id: Url,
+    #[serde(rename = "type")]
+    pub(crate) kind: CreateType,
+    pub(crate) actor: ObjectId<DbActor>,
+    pub(crate) object: ReviewObject,
+}
+
+#[async_trait::async_trait]
+impl Activity for CreateActivity {
+    type DataType = FederationData;
+    type Error = Error;
+
+    fn id(&self) -> &Url {
+        &self.id
+    }
+
+    fn actor(&self) -> &Url {
+        self.actor.inner()
+    }
+
+    async fn verify(&self, _data: &Data<Self::DataType>) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    async fn receive(self, data: &Data<Self::DataType>) -> Result<(), Self::Error> {
+        DbReview::from_json(self.object, data).await?;
+        tracing::info!(actor = %self.actor.inner(), "received review");
+        Ok(())
+    }
+}
+
+// --- Delete ---
+
+#[derive(Debug, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct DeleteActivity {
+    pub(crate) id: Url,
+    #[serde(rename = "type")]
+    pub(crate) kind: DeleteType,
+    pub(crate) actor: ObjectId<DbActor>,
+    pub(crate) object: Url,
+}
+
+#[async_trait::async_trait]
+impl Activity for DeleteActivity {
+    type DataType = FederationData;
+    type Error = Error;
+
+    fn id(&self) -> &Url {
+        &self.id
+    }
+
+    fn actor(&self) -> &Url {
+        self.actor.inner()
+    }
+
+    async fn verify(&self, _data: &Data<Self::DataType>) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    async fn receive(self, _data: &Data<Self::DataType>) -> Result<(), Self::Error> {
+        tracing::info!(actor = %self.actor.inner(), object = %self.object, "delete received (no-op)");
+        Ok(())
+    }
+}
+
+// --- Inbox dispatch enum ---
+
+#[derive(Debug, Deserialize, Serialize)]
+#[serde(tag = "type")]
+#[enum_delegate::implement(Activity)]
+pub enum InboxActivities {
+    #[serde(rename = "Follow")]
+    Follow(FollowActivity),
+    #[serde(rename = "Accept")]
+    Accept(AcceptActivity),
+    #[serde(rename = "Reject")]
+    Reject(RejectActivity),
+    #[serde(rename = "Undo")]
+    Undo(UndoActivity),
+    #[serde(rename = "Create")]
+    Create(CreateActivity),
+    #[serde(rename = "Delete")]
+    Delete(DeleteActivity),
+}
--- a/crates/adapters/activitypub/src/actor_handler.rs
+++ b/crates/adapters/activitypub/src/actor_handler.rs
@@ -0,0 +1,24 @@
+use activitypub_federation::{
+    axum::json::FederationJson, config::Data, protocol::context::WithContext, traits::Object,
+};
+use axum::extract::Path;
+
+use domain::value_objects::UserId;
+
+use crate::actors::{get_local_actor, Person};
+use crate::data::FederationData;
+use crate::error::Error;
+
+pub async fn actor_handler(
+    Path(user_id_str): Path<String>,
+    data: Data<FederationData>,
+) -> Result<FederationJson<WithContext<Person>>, Error> {
+    let uuid = uuid::Uuid::parse_str(&user_id_str)
+        .map_err(|_| Error(anyhow::anyhow!("invalid user id")))?;
+    let user_id = UserId::from_uuid(uuid);
+
+    let db_actor = get_local_actor(user_id, &data).await?;
+    let person = db_actor.into_json(&data).await?;
+
+    Ok(FederationJson(WithContext::new_default(person)))
+}
--- a/crates/adapters/activitypub/src/actors.rs
+++ b/crates/adapters/activitypub/src/actors.rs
@@ -0,0 +1,258 @@
+use activitypub_federation::{
+    config::Data,
+    fetch::object_id::ObjectId,
+    http_signatures::generate_actor_keypair,
+    kinds::actor::PersonType,
+    protocol::{public_key::PublicKey, verification::verify_domains_match},
+    traits::{Actor, Object},
+};
+use chrono::{DateTime, Utc};
+use serde::{Deserialize, Serialize};
+use url::Url;
+
+use domain::value_objects::UserId;
+
+use crate::data::FederationData;
+use crate::error::Error;
+use crate::repository::RemoteActor;
+
+#[derive(Debug, Clone)]
+pub struct DbActor {
+    pub user_id: UserId,
+    pub email: String,
+    pub public_key_pem: String,
+    pub private_key_pem: Option<String>,
+    pub inbox_url: Url,
+    pub outbox_url: Url,
+    pub followers_url: Url,
+    pub following_url: Url,
+    pub ap_id: Url,
+    pub last_refreshed_at: DateTime<Utc>,
+}
+
+#[derive(Debug, Clone, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct Person {
+    #[serde(rename = "type")]
+    kind: PersonType,
+    id: ObjectId<DbActor>,
+    preferred_username: String,
+    inbox: Url,
+    outbox: Url,
+    followers: Url,
+    following: Url,
+    public_key: PublicKey,
+    name: Option<String>,
+}
+
+pub fn actor_url(base_url: &str, user_id: &UserId) -> Url {
+    Url::parse(&format!("{}/users/{}", base_url, user_id.value())).expect("valid actor url")
+}
+
+pub async fn get_local_actor(
+    user_id: UserId,
+    data: &Data<FederationData>,
+) -> Result<DbActor, Error> {
+    let user = data
+        .user_repo
+        .find_by_id(&user_id)
+        .await
+        .map_err(|e| Error(e.into()))?
+        .ok_or_else(|| Error(anyhow::anyhow!("user not found: {}", user_id.value())))?;
+
+    let (public_key, private_key) = match data
+        .federation_repo
+        .get_local_actor_keypair(user_id.clone())
+        .await?
+    {
+        Some(kp) => kp,
+        None => {
+            let kp = generate_actor_keypair()?;
+            data.federation_repo
+                .save_local_actor_keypair(
+                    user_id.clone(),
+                    kp.public_key.clone(),
+                    kp.private_key.clone(),
+                )
+                .await?;
+            (kp.public_key, kp.private_key)
+        }
+    };
+
+    let ap_id = actor_url(&data.base_url, user.id());
+    let inbox_url = Url::parse(&format!("{}/inbox", &ap_id)).expect("valid inbox url");
+    let outbox_url = Url::parse(&format!("{}/outbox", &ap_id)).expect("valid outbox url");
+    let followers_url = Url::parse(&format!("{}/followers", &ap_id)).expect("valid followers url");
+    let following_url = Url::parse(&format!("{}/following", &ap_id)).expect("valid following url");
+
+    Ok(DbActor {
+        user_id: user.id().clone(),
+        email: user.email().value().to_string(),
+        public_key_pem: public_key,
+        private_key_pem: Some(private_key),
+        inbox_url,
+        outbox_url,
+        followers_url,
+        following_url,
+        ap_id,
+        last_refreshed_at: Utc::now(),
+    })
+}
+
+#[async_trait::async_trait]
+impl Object for DbActor {
+    type DataType = FederationData;
+    type Kind = Person;
+    type Error = Error;
+
+    fn id(&self) -> &Url {
+        &self.ap_id
+    }
+
+    fn last_refreshed_at(&self) -> Option<DateTime<Utc>> {
+        Some(self.last_refreshed_at)
+    }
+
+    async fn read_from_id(
+        object_id: Url,
+        data: &Data<Self::DataType>,
+    ) -> Result<Option<Self>, Self::Error> {
+        // Extract user_id from URL path: /users/{uuid}
+        let path = object_id.path();
+        let user_id_str = path
+            .strip_prefix("/users/")
+            .and_then(|s| s.split('/').next());
+
+        let user_id_str = match user_id_str {
+            Some(s) => s,
+            None => return Ok(None),
+        };
+
+        let uuid = match uuid::Uuid::parse_str(user_id_str) {
+            Ok(u) => u,
+            Err(_) => return Ok(None),
+        };
+
+        let user_id = UserId::from_uuid(uuid);
+        let user = match data.user_repo.find_by_id(&user_id).await {
+            Ok(Some(u)) => u,
+            _ => return Ok(None),
+        };
+
+        let keypair = data
+            .federation_repo
+            .get_local_actor_keypair(user_id.clone())
+            .await?;
+
+        let (public_key, private_key) = match keypair {
+            Some(kp) => (kp.0, Some(kp.1)),
+            None => return Ok(None),
+        };
+
+        let ap_id = actor_url(&data.base_url, user.id());
+        let inbox_url = Url::parse(&format!("{}/inbox", &ap_id)).expect("valid url");
+        let outbox_url = Url::parse(&format!("{}/outbox", &ap_id)).expect("valid url");
+        let followers_url = Url::parse(&format!("{}/followers", &ap_id)).expect("valid url");
+        let following_url = Url::parse(&format!("{}/following", &ap_id)).expect("valid url");
+
+        Ok(Some(DbActor {
+            user_id: user.id().clone(),
+            email: user.email().value().to_string(),
+            public_key_pem: public_key,
+            private_key_pem: private_key,
+            inbox_url,
+            outbox_url,
+            followers_url,
+            following_url,
+            ap_id,
+            last_refreshed_at: Utc::now(),
+        }))
+    }
+
+    async fn into_json(self, _data: &Data<Self::DataType>) -> Result<Self::Kind, Self::Error> {
+        let public_key = PublicKey {
+            id: format!("{}#main-key", &self.ap_id),
+            owner: self.ap_id.clone(),
+            public_key_pem: self.public_key_pem.clone(),
+        };
+
+        Ok(Person {
+            kind: Default::default(),
+            id: self.ap_id.clone().into(),
+            preferred_username: self
+                .email
+                .split('@')
+                .next()
+                .unwrap_or(&self.email)
+                .to_string(),
+            inbox: self.inbox_url.clone(),
+            outbox: self.outbox_url.clone(),
+            followers: self.followers_url.clone(),
+            following: self.following_url.clone(),
+            public_key,
+            name: Some(self.email.clone()),
+        })
+    }
+
+    async fn verify(
+        json: &Self::Kind,
+        expected_domain: &Url,
+        _data: &Data<Self::DataType>,
+    ) -> Result<(), Self::Error> {
+        verify_domains_match(json.id.inner(), expected_domain)?;
+        Ok(())
+    }
+
+    async fn from_json(
+        json: Self::Kind,
+        data: &Data<Self::DataType>,
+    ) -> Result<Self, Self::Error> {
+        let actor = RemoteActor {
+            url: json.id.inner().to_string(),
+            handle: json.preferred_username.clone(),
+            inbox_url: json.inbox.to_string(),
+            shared_inbox_url: None,
+            display_name: json.name.clone(),
+        };
+        data.federation_repo.upsert_remote_actor(actor).await?;
+
+        // Deterministic UUID from actor URL so the same remote actor always maps to the same UserId
+        let url_str = json.id.inner().to_string();
+        let stable_id = uuid::Uuid::new_v5(&uuid::Uuid::NAMESPACE_URL, url_str.as_bytes());
+        let user_id = UserId::from_uuid(stable_id);
+        let ap_id = json.id.inner().clone();
+        let inbox_url = json.inbox.clone();
+        let outbox_url = json.outbox.clone();
+        let followers_url = json.followers.clone();
+        let following_url = json.following.clone();
+
+        Ok(DbActor {
+            user_id,
+            email: json
+                .name
+                .unwrap_or_else(|| json.preferred_username.clone()),
+            public_key_pem: json.public_key.public_key_pem,
+            private_key_pem: None,
+            inbox_url,
+            outbox_url,
+            followers_url,
+            following_url,
+            ap_id,
+            last_refreshed_at: Utc::now(),
+        })
+    }
+}
+
+impl Actor for DbActor {
+    fn public_key_pem(&self) -> &str {
+        &self.public_key_pem
+    }
+
+    fn private_key_pem(&self) -> Option<String> {
+        self.private_key_pem.clone()
+    }
+
+    fn inbox(&self) -> Url {
+        self.inbox_url.clone()
+    }
+}
--- a/crates/adapters/activitypub/src/data.rs
+++ b/crates/adapters/activitypub/src/data.rs
@@ -0,0 +1,35 @@
+use std::sync::Arc;
+
+use domain::ports::UserRepository;
+
+use crate::repository::FederationRepository;
+
+#[derive(Clone)]
+pub struct FederationData {
+    pub(crate) federation_repo: Arc<dyn FederationRepository>,
+    pub(crate) user_repo: Arc<dyn UserRepository>,
+    pub(crate) base_url: String,
+    pub(crate) domain: String,
+}
+
+impl FederationData {
+    pub fn new(
+        federation_repo: Arc<dyn FederationRepository>,
+        user_repo: Arc<dyn UserRepository>,
+        base_url: String,
+    ) -> Self {
+        let domain = base_url
+            .trim_start_matches("https://")
+            .trim_start_matches("http://")
+            .split('/')
+            .next()
+            .unwrap_or("")
+            .to_string();
+        Self {
+            federation_repo,
+            user_repo,
+            base_url,
+            domain,
+        }
+    }
+}
--- a/crates/adapters/activitypub/src/error.rs
+++ b/crates/adapters/activitypub/src/error.rs
@@ -0,0 +1,36 @@
+use std::fmt::{Display, Formatter};
+
+#[derive(Debug)]
+pub struct Error(pub(crate) anyhow::Error);
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        std::fmt::Display::fmt(&self.0, f)
+    }
+}
+
+impl<T> From<T> for Error
+where
+    T: Into<anyhow::Error>,
+{
+    fn from(t: T) -> Self {
+        Error(t.into())
+    }
+}
+
+impl axum::response::IntoResponse for Error {
+    fn into_response(self) -> axum::response::Response {
+        let msg = self.0.to_string();
+        let status = if msg.contains("not found") {
+            tracing::debug!(error = %msg, "AP: not found");
+            (axum::http::StatusCode::NOT_FOUND, "Not found")
+        } else if msg.contains("invalid") || msg.contains("bad") {
+            tracing::debug!(error = %msg, "AP: bad request");
+            (axum::http::StatusCode::BAD_REQUEST, "Bad request")
+        } else {
+            tracing::error!(error = %msg, "AP: internal error");
+            (axum::http::StatusCode::INTERNAL_SERVER_ERROR, "Internal server error")
+        };
+        status.into_response()
+    }
+}
--- a/crates/adapters/activitypub/src/event_handler.rs
+++ b/crates/adapters/activitypub/src/event_handler.rs
@@ -0,0 +1,127 @@
+use activitypub_federation::{
+    activity_sending::SendActivityTask,
+    fetch::object_id::ObjectId,
+    protocol::context::WithContext,
+};
+use async_trait::async_trait;
+use chrono::{DateTime, Utc};
+use domain::{
+    errors::DomainError,
+    events::DomainEvent,
+    value_objects::{ReviewId, UserId},
+};
+use event_publisher::EventHandler;
+use url::Url;
+
+use crate::{
+    activities::CreateActivity,
+    actors::{actor_url, get_local_actor},
+    federation::ApFederationConfig,
+    objects::{review_url, ReviewObject},
+    repository::FollowerStatus,
+};
+
+pub struct ActivityPubEventHandler {
+    federation_config: ApFederationConfig,
+    base_url: String,
+}
+
+impl ActivityPubEventHandler {
+    pub fn new(federation_config: ApFederationConfig, base_url: String) -> Self {
+        Self {
+            federation_config,
+            base_url,
+        }
+    }
+}
+
+#[async_trait]
+impl EventHandler for ActivityPubEventHandler {
+    async fn handle(&self, event: &DomainEvent) -> Result<(), DomainError> {
+        match event {
+            DomainEvent::ReviewLogged {
+                review_id,
+                user_id,
+                rating,
+                watched_at,
+                ..
+            } => self
+                .on_review_logged(user_id, review_id, rating.value(), *watched_at)
+                .await
+                .map_err(|e| DomainError::InfrastructureError(e.to_string())),
+            _ => Ok(()),
+        }
+    }
+}
+
+impl ActivityPubEventHandler {
+    async fn on_review_logged(
+        &self,
+        user_id: &UserId,
+        review_id: &ReviewId,
+        rating: u8,
+        watched_at: chrono::NaiveDateTime,
+    ) -> anyhow::Result<()> {
+        let data = self.federation_config.to_request_data();
+
+        let followers = data.federation_repo.get_followers(user_id.clone()).await?;
+        let accepted: Vec<_> = followers
+            .into_iter()
+            .filter(|f| f.status == FollowerStatus::Accepted)
+            .collect();
+
+        if accepted.is_empty() {
+            return Ok(());
+        }
+
+        let local_actor = get_local_actor(user_id.clone(), &data)
+            .await
+            .map_err(|e| anyhow::anyhow!("{e}"))?;
+
+        let review_id_url = review_url(&self.base_url, review_id);
+        let actor_id = actor_url(&self.base_url, user_id);
+        let activity_id = Url::parse(&format!(
+            "{}/activities/{}",
+            self.base_url,
+            uuid::Uuid::new_v4()
+        ))?;
+
+        let stars = "\u{2B50}".repeat(rating as usize);
+        let now = DateTime::from_naive_utc_and_offset(watched_at, Utc);
+
+        let object = ReviewObject {
+            kind: "Review".to_string(),
+            id: review_id_url.into(),
+            attributed_to: actor_id.into(),
+            content: format!("{} (movie review)", stars),
+            published: Utc::now(),
+            movie_title: "Unknown".to_string(), // TODO: fetch from MovieRepository
+            rating,
+            comment: None,
+            watched_at: now,
+        };
+
+        let create = CreateActivity {
+            id: activity_id,
+            kind: Default::default(),
+            actor: ObjectId::from(local_actor.ap_id.clone()),
+            object,
+        };
+        let create_with_ctx = WithContext::new_default(create);
+
+        let inboxes: Vec<Url> = accepted
+            .iter()
+            .filter_map(|f| Url::parse(&f.actor.inbox_url).ok())
+            .collect();
+
+        let sends =
+            SendActivityTask::prepare(&create_with_ctx, &local_actor, inboxes, &data).await?;
+        for send in sends {
+            if let Err(e) = send.sign_and_send(&data).await {
+                tracing::warn!(error = %e, "failed to deliver activity to follower");
+            }
+        }
+
+        Ok(())
+    }
+}
--- a/crates/adapters/activitypub/src/federation.rs
+++ b/crates/adapters/activitypub/src/federation.rs
@@ -0,0 +1,26 @@
+use activitypub_federation::config::{Data, FederationConfig, FederationMiddleware};
+
+use crate::data::FederationData;
+
+#[derive(Clone)]
+pub struct ApFederationConfig(pub FederationConfig<FederationData>);
+
+impl ApFederationConfig {
+    pub async fn new(data: FederationData, debug: bool) -> anyhow::Result<Self> {
+        let config = FederationConfig::builder()
+            .domain(&data.domain)
+            .app_data(data)
+            .debug(debug)
+            .build()
+            .await?;
+        Ok(Self(config))
+    }
+
+    pub fn to_request_data(&self) -> Data<FederationData> {
+        self.0.to_request_data()
+    }
+
+    pub fn middleware(&self) -> FederationMiddleware<FederationData> {
+        FederationMiddleware::new(self.0.clone())
+    }
+}
--- a/crates/adapters/activitypub/src/followers_handler.rs
+++ b/crates/adapters/activitypub/src/followers_handler.rs
@@ -0,0 +1,62 @@
+use activitypub_federation::{axum::json::FederationJson, config::Data};
+use axum::extract::Path;
+use serde_json::json;
+
+use domain::value_objects::UserId;
+
+use crate::data::FederationData;
+use crate::error::Error;
+
+pub async fn followers_handler(
+    Path(user_id_str): Path<String>,
+    data: Data<FederationData>,
+) -> Result<FederationJson<serde_json::Value>, Error> {
+    let user_id = UserId::from_uuid(
+        uuid::Uuid::parse_str(&user_id_str)
+            .map_err(|_| Error(anyhow::anyhow!("invalid user id")))?,
+    );
+
+    // verify user exists
+    data.user_repo
+        .find_by_id(&user_id)
+        .await
+        .map_err(|e| Error(e.into()))?
+        .ok_or_else(|| Error(anyhow::anyhow!("user not found")))?;
+
+    let id = format!("{}/users/{}/followers", data.base_url, user_id_str);
+    // TODO(ap): implement pagination
+    Ok(FederationJson(json!({
+        "@context": "https://www.w3.org/ns/activitystreams",
+        "type": "OrderedCollection",
+        "id": id,
+        "totalItems": 0,
+        "orderedItems": []
+    })))
+}
+
+pub async fn following_handler(
+    Path(user_id_str): Path<String>,
+    data: Data<FederationData>,
+) -> Result<FederationJson<serde_json::Value>, Error> {
+    let user_id = UserId::from_uuid(
+        uuid::Uuid::parse_str(&user_id_str)
+            .map_err(|_| Error(anyhow::anyhow!("invalid user id")))?,
+    );
+
+    // verify user exists
+    data.user_repo
+        .find_by_id(&user_id)
+        .await
+        .map_err(|e| Error(e.into()))?
+        .ok_or_else(|| Error(anyhow::anyhow!("user not found")))?;
+
+    let id = format!("{}/users/{}/following", data.base_url, user_id_str);
+    // TODO(ap): implement pagination
+    Ok(FederationJson(json!({
+        "@context": "https://www.w3.org/ns/activitystreams",
+        "type": "OrderedCollection",
+        "id": id,
+        "totalItems": 0,
+        "orderedItems": []
+    })))
+}
--- a/crates/adapters/activitypub/src/inbox.rs
+++ b/crates/adapters/activitypub/src/inbox.rs
@@ -0,0 +1,20 @@
+use activitypub_federation::{
+    axum::inbox::{receive_activity, ActivityData},
+    config::Data,
+    protocol::context::WithContext,
+};
+
+use crate::activities::InboxActivities;
+use crate::actors::DbActor;
+use crate::data::FederationData;
+use crate::error::Error;
+
+pub async fn inbox_handler(
+    data: Data<FederationData>,
+    activity_data: ActivityData,
+) -> Result<(), Error> {
+    receive_activity::<WithContext<InboxActivities>, DbActor, FederationData>(
+        activity_data, &data,
+    )
+    .await
+}
--- a/crates/adapters/activitypub/src/lib.rs
+++ b/crates/adapters/activitypub/src/lib.rs
@@ -0,0 +1,21 @@
+pub mod activities;
+pub mod actor_handler;
+pub mod actors;
+pub mod data;
+pub mod error;
+pub mod event_handler;
+pub mod federation;
+pub mod followers_handler;
+pub mod inbox;
+pub mod objects;
+pub mod outbox;
+pub mod repository;
+pub mod service;
+pub mod webfinger;
+
+pub use data::FederationData;
+pub use error::Error;
+pub use event_handler::ActivityPubEventHandler;
+pub use federation::ApFederationConfig;
+pub use repository::{FederationRepository, Follower, FollowerStatus, RemoteActor};
+pub use service::ActivityPubService;
--- a/crates/adapters/activitypub/src/objects.rs
+++ b/crates/adapters/activitypub/src/objects.rs
@@ -0,0 +1,137 @@
+use activitypub_federation::{
+    config::Data,
+    fetch::object_id::ObjectId,
+    protocol::verification::verify_domains_match,
+    traits::Object,
+};
+use chrono::{DateTime, Utc};
+use serde::{Deserialize, Serialize};
+use url::Url;
+
+use domain::models::{Review, ReviewSource};
+use domain::value_objects::ReviewId;
+
+use crate::actors::DbActor;
+use crate::data::FederationData;
+use crate::error::Error;
+
+#[derive(Debug, Clone, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct ReviewObject {
+    #[serde(rename = "type")]
+    pub(crate) kind: String,
+    pub(crate) id: ObjectId<DbReview>,
+    pub(crate) attributed_to: ObjectId<DbActor>,
+    pub(crate) content: String,
+    pub(crate) published: DateTime<Utc>,
+    pub(crate) movie_title: String,
+    pub(crate) rating: u8,
+    pub(crate) comment: Option<String>,
+    pub(crate) watched_at: DateTime<Utc>,
+}
+
+#[derive(Debug, Clone)]
+pub struct DbReview {
+    pub review: Review,
+    pub ap_id: Url,
+}
+
+pub fn review_url(base_url: &str, review_id: &ReviewId) -> Url {
+    Url::parse(&format!("{}/reviews/{}", base_url, review_id.value())).expect("valid review url")
+}
+
+#[async_trait::async_trait]
+impl Object for DbReview {
+    type DataType = FederationData;
+    type Kind = ReviewObject;
+    type Error = Error;
+
+    fn id(&self) -> &Url {
+        &self.ap_id
+    }
+
+    async fn read_from_id(
+        _object_id: Url,
+        _data: &Data<Self::DataType>,
+    ) -> Result<Option<Self>, Self::Error> {
+        // Incoming activities provide the full object; no need to dereference local reviews
+        Ok(None)
+    }
+
+    async fn into_json(self, data: &Data<Self::DataType>) -> Result<Self::Kind, Self::Error> {
+        let r = &self.review;
+        let ap_id = review_url(&data.base_url, r.id());
+        let actor_url = crate::actors::actor_url(&data.base_url, r.user_id());
+
+        let stars: String = "\u{2B50}".repeat(r.rating().value() as usize);
+        let comment_text = r.comment().map(|c| c.value().to_string());
+        // TODO(ap): fetch movie title from MovieRepository via FederationData
+        let movie_title = "Unknown".to_string();
+
+        let fallback = match &comment_text {
+            Some(c) => format!("{} Watched '{}': {}", stars, movie_title, c),
+            None => format!("{} Watched '{}'", stars, movie_title),
+        };
+
+        Ok(ReviewObject {
+            kind: "Review".to_string(),
+            id: ap_id.into(),
+            attributed_to: actor_url.into(),
+            content: fallback,
+            published: DateTime::from_naive_utc_and_offset(*r.created_at(), Utc),
+            movie_title,
+            rating: r.rating().value(),
+            comment: comment_text,
+            watched_at: DateTime::from_naive_utc_and_offset(*r.watched_at(), Utc),
+        })
+    }
+
+    async fn verify(
+        json: &Self::Kind,
+        expected_domain: &Url,
+        _data: &Data<Self::DataType>,
+    ) -> Result<(), Self::Error> {
+        verify_domains_match(json.attributed_to.inner(), expected_domain)?;
+        Ok(())
+    }
+
+    async fn from_json(
+        json: Self::Kind,
+        data: &Data<Self::DataType>,
+    ) -> Result<Self, Self::Error> {
+        let actor_url = json.attributed_to.inner().to_string();
+
+        let review_id = ReviewId::generate();
+        // TODO(ap): create stub movie/user entries in DB so feed JOIN queries work.
+        // For now, use deterministic UUIDs from content hash; reviews will be orphaned in JOINs.
+        let movie_id_uuid = uuid::Uuid::new_v5(&uuid::Uuid::NAMESPACE_URL, json.movie_title.as_bytes());
+        let movie_id = domain::value_objects::MovieId::from_uuid(movie_id_uuid);
+        let user_id_uuid = uuid::Uuid::new_v5(&uuid::Uuid::NAMESPACE_URL, actor_url.as_bytes());
+        let user_id = domain::value_objects::UserId::from_uuid(user_id_uuid);
+        let rating = domain::value_objects::Rating::new(json.rating.min(5))
+            .map_err(|e| Error(anyhow::anyhow!("{}", e)))?;
+        let comment = json
+            .comment
+            .map(|c| domain::value_objects::Comment::new(c))
+            .transpose()
+            .map_err(|e| Error(anyhow::anyhow!("{}", e)))?;
+        let watched_at = json.watched_at.naive_utc();
+        let created_at = json.published.naive_utc();
+
+        let review = Review::from_persistence(
+            review_id,
+            movie_id,
+            user_id,
+            rating,
+            comment,
+            watched_at,
+            created_at,
+            ReviewSource::Remote { actor_url },
+        );
+
+        let ap_id = review_url(&data.base_url, review.id());
+        data.federation_repo.save_remote_review(&review).await?;
+
+        Ok(DbReview { review, ap_id })
+    }
+}
--- a/crates/adapters/activitypub/src/outbox.rs
+++ b/crates/adapters/activitypub/src/outbox.rs
@@ -0,0 +1,46 @@
+use activitypub_federation::{axum::json::FederationJson, config::Data};
+use axum::extract::Path;
+use serde::{Deserialize, Serialize};
+
+use domain::value_objects::UserId;
+
+use crate::data::FederationData;
+use crate::error::Error;
+
+#[derive(Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct OrderedCollection {
+    #[serde(rename = "@context")]
+    context: String,
+    #[serde(rename = "type")]
+    kind: String,
+    id: String,
+    total_items: u64,
+    ordered_items: Vec<serde_json::Value>,
+}
+
+pub async fn outbox_handler(
+    Path(user_id_str): Path<String>,
+    data: Data<FederationData>,
+) -> Result<FederationJson<OrderedCollection>, Error> {
+    let uuid = uuid::Uuid::parse_str(&user_id_str)
+        .map_err(|_| Error(anyhow::anyhow!("invalid user id")))?;
+    let user_id = UserId::from_uuid(uuid);
+
+    // verify user exists
+    data.user_repo
+        .find_by_id(&user_id)
+        .await
+        .map_err(|e| Error(e.into()))?
+        .ok_or_else(|| Error(anyhow::anyhow!("user not found")))?;
+
+    let outbox_url = format!("{}/users/{}/outbox", data.base_url, user_id_str);
+
+    Ok(FederationJson(OrderedCollection {
+        context: "https://www.w3.org/ns/activitystreams".to_string(),
+        kind: "OrderedCollection".to_string(),
+        id: outbox_url,
+        total_items: 0,
+        ordered_items: vec![],
+    }))
+}
--- a/crates/adapters/activitypub/src/repository.rs
+++ b/crates/adapters/activitypub/src/repository.rs
@@ -0,0 +1,43 @@
+use anyhow::Result;
+use async_trait::async_trait;
+use domain::models::Review;
+use domain::value_objects::UserId;
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum FollowerStatus {
+    Pending,
+    Accepted,
+    Rejected,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct RemoteActor {
+    pub url: String,
+    pub handle: String,
+    pub inbox_url: String,
+    pub shared_inbox_url: Option<String>,
+    pub display_name: Option<String>,
+}
+
+#[derive(Debug, Clone)]
+pub struct Follower {
+    pub actor: RemoteActor,
+    pub status: FollowerStatus,
+}
+
+#[async_trait]
+pub trait FederationRepository: Send + Sync {
+    async fn add_follower(&self, local_user_id: UserId, remote_actor_url: &str, status: FollowerStatus) -> Result<()>;
+    async fn remove_follower(&self, local_user_id: UserId, remote_actor_url: &str) -> Result<()>;
+    async fn get_followers(&self, local_user_id: UserId) -> Result<Vec<Follower>>;
+    async fn update_follower_status(&self, local_user_id: UserId, remote_actor_url: &str, status: FollowerStatus) -> Result<()>;
+    async fn add_following(&self, local_user_id: UserId, actor: RemoteActor) -> Result<()>;
+    async fn remove_following(&self, local_user_id: UserId, actor_url: &str) -> Result<()>;
+    async fn get_following(&self, local_user_id: UserId) -> Result<Vec<RemoteActor>>;
+    async fn count_following(&self, local_user_id: UserId) -> Result<usize>;
+    async fn upsert_remote_actor(&self, actor: RemoteActor) -> Result<()>;
+    async fn get_remote_actor(&self, actor_url: &str) -> Result<Option<RemoteActor>>;
+    async fn save_remote_review(&self, review: &Review) -> Result<()>;
+    async fn get_local_actor_keypair(&self, user_id: UserId) -> Result<Option<(String, String)>>;
+    async fn save_local_actor_keypair(&self, user_id: UserId, public_key: String, private_key: String) -> Result<()>;
+}
--- a/crates/adapters/activitypub/src/service.rs
+++ b/crates/adapters/activitypub/src/service.rs
@@ -0,0 +1,188 @@
+use std::sync::Arc;
+
+use activitypub_federation::{
+    activity_sending::SendActivityTask,
+    config::Data,
+    fetch::{object_id::ObjectId, webfinger::webfinger_resolve_actor},
+    protocol::context::WithContext,
+    traits::Actor,
+};
+use axum::{routing::get, routing::post, Router};
+use domain::{ports::UserRepository, value_objects::UserId};
+use url::Url;
+
+use crate::{
+    activities::{FollowActivity, UndoActivity},
+    actor_handler::actor_handler,
+    actors::{get_local_actor, DbActor},
+    data::FederationData,
+    event_handler::ActivityPubEventHandler,
+    federation::ApFederationConfig,
+    followers_handler::{followers_handler, following_handler},
+    inbox::inbox_handler,
+    outbox::outbox_handler,
+    repository::{FederationRepository, RemoteActor},
+    webfinger::webfinger_handler,
+};
+
+pub struct ActivityPubService {
+    federation_config: ApFederationConfig,
+    base_url: String,
+}
+
+impl ActivityPubService {
+    pub async fn new(
+        repo: Arc<dyn FederationRepository>,
+        user_repo: Arc<dyn UserRepository>,
+        base_url: String,
+        debug: bool,
+    ) -> anyhow::Result<Self> {
+        let data = FederationData::new(repo, user_repo, base_url.clone());
+        let federation_config = ApFederationConfig::new(data, debug).await?;
+        Ok(Self {
+            federation_config,
+            base_url,
+        })
+    }
+
+    pub fn federation_config(&self) -> &ApFederationConfig {
+        &self.federation_config
+    }
+
+    pub fn request_data(&self) -> Data<FederationData> {
+        self.federation_config.to_request_data()
+    }
+
+    pub fn router(&self) -> Router {
+        Router::new()
+            .route("/.well-known/webfinger", get(webfinger_handler))
+            .route("/users/{user_id}", get(actor_handler))
+            .route("/users/{user_id}/inbox", post(inbox_handler))
+            .route("/users/{user_id}/outbox", get(outbox_handler))
+            .route("/users/{user_id}/followers", get(followers_handler))
+            .route("/users/{user_id}/following", get(following_handler))
+            .layer(self.federation_config.middleware())
+    }
+
+    pub fn event_handler(&self) -> ActivityPubEventHandler {
+        ActivityPubEventHandler::new(self.federation_config.clone(), self.base_url.clone())
+    }
+
+    pub async fn follow(&self, local_user_id: UserId, handle: &str) -> anyhow::Result<()> {
+        let data = self.federation_config.to_request_data();
+
+        let remote_actor: DbActor = webfinger_resolve_actor(handle, &data)
+            .await
+            .map_err(|e| anyhow::anyhow!("{e}"))?;
+
+        let local_actor = get_local_actor(local_user_id.clone(), &data)
+            .await
+            .map_err(|e| anyhow::anyhow!("{e}"))?;
+
+        let follow_id = Url::parse(&format!(
+            "{}/activities/{}",
+            self.base_url,
+            uuid::Uuid::new_v4()
+        ))?;
+        let follow = FollowActivity {
+            id: follow_id,
+            kind: Default::default(),
+            actor: ObjectId::from(local_actor.ap_id.clone()),
+            object: ObjectId::from(remote_actor.ap_id.clone()),
+        };
+        let follow_with_ctx = WithContext::new_default(follow);
+
+        let sends = SendActivityTask::prepare(
+            &follow_with_ctx,
+            &local_actor,
+            vec![remote_actor.inbox()],
+            &data,
+        )
+        .await?;
+        for send in sends {
+            send.sign_and_send(&data).await?;
+        }
+
+        let remote = RemoteActor {
+            url: remote_actor.ap_id.to_string(),
+            handle: remote_actor
+                .email
+                .split('@')
+                .next()
+                .unwrap_or(&remote_actor.email)
+                .to_string(),
+            inbox_url: remote_actor.inbox_url.to_string(),
+            shared_inbox_url: None,
+            display_name: Some(remote_actor.email.clone()),
+        };
+        data.federation_repo
+            .add_following(local_user_id, remote)
+            .await?;
+
+        Ok(())
+    }
+
+    pub async fn unfollow(&self, local_user_id: UserId, actor_url_str: &str) -> anyhow::Result<()> {
+        let data = self.federation_config.to_request_data();
+
+        let remote = data
+            .federation_repo
+            .get_remote_actor(actor_url_str)
+            .await?
+            .ok_or_else(|| anyhow::anyhow!("remote actor not found: {}", actor_url_str))?;
+
+        let local_actor = get_local_actor(local_user_id.clone(), &data)
+            .await
+            .map_err(|e| anyhow::anyhow!("{e}"))?;
+
+        let remote_ap_id = Url::parse(actor_url_str)?;
+        let inbox = Url::parse(&remote.inbox_url)?;
+
+        let follow_id = Url::parse(&format!(
+            "{}/activities/{}",
+            self.base_url,
+            uuid::Uuid::new_v4()
+        ))?;
+        let follow = FollowActivity {
+            id: follow_id,
+            kind: Default::default(),
+            actor: ObjectId::from(local_actor.ap_id.clone()),
+            object: ObjectId::from(remote_ap_id),
+        };
+
+        let undo_id = Url::parse(&format!(
+            "{}/activities/{}",
+            self.base_url,
+            uuid::Uuid::new_v4()
+        ))?;
+        let undo = UndoActivity {
+            id: undo_id,
+            kind: Default::default(),
+            actor: ObjectId::from(local_actor.ap_id.clone()),
+            object: follow,
+        };
+        let undo_with_ctx = WithContext::new_default(undo);
+
+        let sends =
+            SendActivityTask::prepare(&undo_with_ctx, &local_actor, vec![inbox], &data).await?;
+        for send in sends {
+            send.sign_and_send(&data).await?;
+        }
+
+        data.federation_repo
+            .remove_following(local_user_id, actor_url_str)
+            .await?;
+
+        Ok(())
+    }
+
+    pub async fn get_following(&self, local_user_id: UserId) -> anyhow::Result<Vec<RemoteActor>> {
+        let data = self.federation_config.to_request_data();
+        data.federation_repo.get_following(local_user_id).await
+    }
+
+    pub async fn count_following(&self, local_user_id: UserId) -> anyhow::Result<usize> {
+        let data = self.federation_config.to_request_data();
+        data.federation_repo.count_following(local_user_id).await
+    }
+}
--- a/crates/adapters/activitypub/src/webfinger.rs
+++ b/crates/adapters/activitypub/src/webfinger.rs
@@ -0,0 +1,48 @@
+use activitypub_federation::{
+    config::Data,
+    fetch::webfinger::{build_webfinger_response, extract_webfinger_name, Webfinger},
+};
+use axum::{
+    extract::Query,
+    http::header,
+    response::{IntoResponse, Response},
+};
+use serde::Deserialize;
+
+use crate::actors::actor_url;
+use crate::data::FederationData;
+use crate::error::Error;
+
+#[derive(Deserialize)]
+pub struct WebfingerQuery {
+    resource: String,
+}
+
+pub async fn webfinger_handler(
+    Query(query): Query<WebfingerQuery>,
+    data: Data<FederationData>,
+) -> Result<Response, Error> {
+    let name = extract_webfinger_name(&query.resource, &data)?;
+
+    // Look up user by email username@domain
+    let email_str = format!("{}@{}", name, data.domain);
+    let email = domain::value_objects::Email::new(email_str)
+        .map_err(|e| Error(anyhow::anyhow!("{}", e)))?;
+
+    let user = data
+        .user_repo
+        .find_by_email(&email)
+        .await
+        .map_err(|e| Error(e.into()))?
+        .ok_or_else(|| Error(anyhow::anyhow!("user not found")))?;
+
+    let ap_id = actor_url(&data.base_url, user.id());
+
+    let wf: Webfinger = build_webfinger_response(query.resource, ap_id);
+    let body = serde_json::to_string(&wf)
+        .map_err(|e| Error::from(anyhow::anyhow!(e)))?;
+    Ok((
+        [(header::CONTENT_TYPE, "application/jrd+json")],
+        body,
+    ).into_response())
+}
--- a/crates/adapters/sqlite/Cargo.toml
+++ b/crates/adapters/sqlite/Cargo.toml
@@ -12,6 +12,8 @@ sqlx = { version = "0.8.6", features = [
 ] }

 domain = { workspace = true }
+activitypub = { workspace = true }
+anyhow = { workspace = true }
 uuid = { workspace = true }
 chrono = { workspace = true }
 tracing = { workspace = true }
--- a/crates/adapters/sqlite/migrations/0003_activitypub.sql
+++ b/crates/adapters/sqlite/migrations/0003_activitypub.sql
@@ -0,0 +1,28 @@
+ALTER TABLE reviews ADD COLUMN remote_actor_url TEXT;
+CREATE TABLE ap_followers (
+    local_user_id TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    remote_actor_url TEXT NOT NULL,
+    status TEXT NOT NULL DEFAULT 'pending',
+    created_at TEXT NOT NULL,
+    PRIMARY KEY (local_user_id, remote_actor_url)
+);
+CREATE TABLE ap_following (
+    local_user_id TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    remote_actor_url TEXT NOT NULL,
+    created_at TEXT NOT NULL,
+    PRIMARY KEY (local_user_id, remote_actor_url)
+);
+CREATE TABLE ap_remote_actors (
+    url TEXT PRIMARY KEY,
+    handle TEXT NOT NULL,
+    inbox_url TEXT NOT NULL,
+    shared_inbox_url TEXT,
+    display_name TEXT,
+    fetched_at TEXT NOT NULL
+);
+CREATE TABLE IF NOT EXISTS ap_local_actors (
+    user_id TEXT PRIMARY KEY REFERENCES users(id) ON DELETE CASCADE,
+    public_key TEXT NOT NULL,
+    private_key TEXT NOT NULL,
+    created_at TEXT NOT NULL
+);
--- a/crates/adapters/sqlite/src/federation.rs
+++ b/crates/adapters/sqlite/src/federation.rs
@@ -0,0 +1,332 @@
+use anyhow::{anyhow, Result};
+use async_trait::async_trait;
+use chrono::Utc;
+use sqlx::{Row, SqlitePool};
+
+use activitypub::repository::{FederationRepository, Follower, FollowerStatus, RemoteActor};
+use domain::models::{Review, ReviewSource};
+use domain::value_objects::UserId;
+
+use crate::models::datetime_to_str;
+
+pub struct SqliteFederationRepository {
+    pool: SqlitePool,
+}
+
+impl SqliteFederationRepository {
+    pub fn new(pool: SqlitePool) -> Self {
+        Self { pool }
+    }
+}
+
+fn status_to_str(status: &FollowerStatus) -> &'static str {
+    match status {
+        FollowerStatus::Pending => "pending",
+        FollowerStatus::Accepted => "accepted",
+        FollowerStatus::Rejected => "rejected",
+    }
+}
+
+fn str_to_status(s: &str) -> FollowerStatus {
+    match s {
+        "accepted" => FollowerStatus::Accepted,
+        "rejected" => FollowerStatus::Rejected,
+        _ => FollowerStatus::Pending,
+    }
+}
+
+#[async_trait]
+impl FederationRepository for SqliteFederationRepository {
+    async fn add_follower(
+        &self,
+        local_user_id: UserId,
+        remote_actor_url: &str,
+        status: FollowerStatus,
+    ) -> Result<()> {
+        let uid = local_user_id.value().to_string();
+        let status_str = status_to_str(&status);
+        let now = Utc::now().naive_utc();
+        let created_at = datetime_to_str(&now);
+
+        sqlx::query(
+            "INSERT INTO ap_followers (local_user_id, remote_actor_url, status, created_at)
+             VALUES (?1, ?2, ?3, ?4)
+             ON CONFLICT(local_user_id, remote_actor_url) DO UPDATE SET status = excluded.status",
+        )
+        .bind(&uid)
+        .bind(remote_actor_url)
+        .bind(status_str)
+        .bind(&created_at)
+        .execute(&self.pool)
+        .await?;
+
+        Ok(())
+    }
+
+    async fn remove_follower(&self, local_user_id: UserId, remote_actor_url: &str) -> Result<()> {
+        let uid = local_user_id.value().to_string();
+
+        sqlx::query(
+            "DELETE FROM ap_followers WHERE local_user_id = ? AND remote_actor_url = ?",
+        )
+        .bind(&uid)
+        .bind(remote_actor_url)
+        .execute(&self.pool)
+        .await?;
+
+        Ok(())
+    }
+
+    async fn get_followers(&self, local_user_id: UserId) -> Result<Vec<Follower>> {
+        let uid = local_user_id.value().to_string();
+
+        let rows = sqlx::query(
+            "SELECT f.remote_actor_url, f.status,
+                    a.handle, a.inbox_url, a.shared_inbox_url, a.display_name
+             FROM ap_followers f
+             LEFT JOIN ap_remote_actors a ON a.url = f.remote_actor_url
+             WHERE f.local_user_id = ?",
+        )
+        .bind(&uid)
+        .fetch_all(&self.pool)
+        .await?;
+
+        let followers = rows
+            .into_iter()
+            .map(|row| {
+                let url: String = row.get("remote_actor_url");
+                let status_str: String = row.get("status");
+                let handle: String = row.try_get("handle").unwrap_or_default();
+                let inbox_url: String = row.try_get("inbox_url").unwrap_or_default();
+                let shared_inbox_url: Option<String> = row.try_get("shared_inbox_url").ok().flatten();
+                let display_name: Option<String> = row.try_get("display_name").ok().flatten();
+
+                Follower {
+                    actor: RemoteActor {
+                        url,
+                        handle,
+                        inbox_url,
+                        shared_inbox_url,
+                        display_name,
+                    },
+                    status: str_to_status(&status_str),
+                }
+            })
+            .collect();
+
+        Ok(followers)
+    }
+
+    async fn update_follower_status(
+        &self,
+        local_user_id: UserId,
+        remote_actor_url: &str,
+        status: FollowerStatus,
+    ) -> Result<()> {
+        let uid = local_user_id.value().to_string();
+        let status_str = status_to_str(&status);
+
+        let result = sqlx::query(
+            "UPDATE ap_followers SET status = ? WHERE local_user_id = ? AND remote_actor_url = ?",
+        )
+        .bind(status_str)
+        .bind(&uid)
+        .bind(remote_actor_url)
+        .execute(&self.pool)
+        .await?;
+
+        if result.rows_affected() == 0 {
+            tracing::warn!(
+                local_user_id = %local_user_id.value(),
+                remote_actor_url = remote_actor_url,
+                "update_follower_status: no row found"
+            );
+        }
+
+        Ok(())
+    }
+
+    async fn add_following(&self, local_user_id: UserId, actor: RemoteActor) -> Result<()> {
+        let uid = local_user_id.value().to_string();
+        let now = Utc::now().naive_utc();
+        let created_at = datetime_to_str(&now);
+
+        self.upsert_remote_actor(actor.clone()).await?;
+
+        sqlx::query(
+            "INSERT OR IGNORE INTO ap_following (local_user_id, remote_actor_url, created_at)
+             VALUES (?, ?, ?)",
+        )
+        .bind(&uid)
+        .bind(&actor.url)
+        .bind(&created_at)
+        .execute(&self.pool)
+        .await?;
+
+        Ok(())
+    }
+
+    async fn remove_following(&self, local_user_id: UserId, actor_url: &str) -> Result<()> {
+        let uid = local_user_id.value().to_string();
+
+        sqlx::query(
+            "DELETE FROM ap_following WHERE local_user_id = ? AND remote_actor_url = ?",
+        )
+        .bind(&uid)
+        .bind(actor_url)
+        .execute(&self.pool)
+        .await?;
+
+        Ok(())
+    }
+
+    async fn get_following(&self, local_user_id: UserId) -> Result<Vec<RemoteActor>> {
+        let uid = local_user_id.value().to_string();
+
+        let rows = sqlx::query(
+            "SELECT a.url, a.handle, a.inbox_url, a.shared_inbox_url, a.display_name
+             FROM ap_following f
+             INNER JOIN ap_remote_actors a ON a.url = f.remote_actor_url
+             WHERE f.local_user_id = ?",
+        )
+        .bind(&uid)
+        .fetch_all(&self.pool)
+        .await?;
+
+        let actors = rows
+            .into_iter()
+            .map(|row| RemoteActor {
+                url: row.get("url"),
+                handle: row.get("handle"),
+                inbox_url: row.get("inbox_url"),
+                shared_inbox_url: row.try_get("shared_inbox_url").ok().flatten(),
+                display_name: row.try_get("display_name").ok().flatten(),
+            })
+            .collect();
+
+        Ok(actors)
+    }
+
+    async fn count_following(&self, local_user_id: UserId) -> Result<usize> {
+        let uid = local_user_id.value().to_string();
+        let count: i64 = sqlx::query_scalar(
+            "SELECT COUNT(*) FROM ap_following WHERE local_user_id = ?",
+        )
+        .bind(&uid)
+        .fetch_one(&self.pool)
+        .await?;
+        Ok(count as usize)
+    }
+
+    async fn upsert_remote_actor(&self, actor: RemoteActor) -> Result<()> {
+        let now = Utc::now().naive_utc();
+        let fetched_at = datetime_to_str(&now);
+
+        sqlx::query(
+            "INSERT INTO ap_remote_actors (url, handle, inbox_url, shared_inbox_url, display_name, fetched_at)
+             VALUES (?, ?, ?, ?, ?, ?)
+             ON CONFLICT(url) DO UPDATE SET
+                 handle           = excluded.handle,
+                 inbox_url        = excluded.inbox_url,
+                 shared_inbox_url = excluded.shared_inbox_url,
+                 display_name     = excluded.display_name,
+                 fetched_at       = excluded.fetched_at",
+        )
+        .bind(&actor.url)
+        .bind(&actor.handle)
+        .bind(&actor.inbox_url)
+        .bind(&actor.shared_inbox_url)
+        .bind(&actor.display_name)
+        .bind(&fetched_at)
+        .execute(&self.pool)
+        .await?;
+
+        Ok(())
+    }
+
+    async fn get_remote_actor(&self, actor_url: &str) -> Result<Option<RemoteActor>> {
+        let row = sqlx::query(
+            "SELECT url, handle, inbox_url, shared_inbox_url, display_name
+             FROM ap_remote_actors WHERE url = ?",
+        )
+        .bind(actor_url)
+        .fetch_optional(&self.pool)
+        .await?;
+
+        Ok(row.map(|row| RemoteActor {
+            url: row.get("url"),
+            handle: row.get("handle"),
+            inbox_url: row.get("inbox_url"),
+            shared_inbox_url: row.try_get("shared_inbox_url").ok().flatten(),
+            display_name: row.try_get("display_name").ok().flatten(),
+        }))
+    }
+
+    async fn get_local_actor_keypair(&self, user_id: UserId) -> Result<Option<(String, String)>> {
+        let uid = user_id.value().to_string();
+        let row = sqlx::query(
+            "SELECT public_key, private_key FROM ap_local_actors WHERE user_id = ?",
+        )
+        .bind(&uid)
+        .fetch_optional(&self.pool)
+        .await?;
+
+        Ok(row.map(|r| (r.get("public_key"), r.get("private_key"))))
+    }
+
+    async fn save_local_actor_keypair(&self, user_id: UserId, public_key: String, private_key: String) -> Result<()> {
+        let uid = user_id.value().to_string();
+        let now = Utc::now().naive_utc();
+        let created_at = datetime_to_str(&now);
+
+        sqlx::query(
+            "INSERT INTO ap_local_actors (user_id, public_key, private_key, created_at)
+             VALUES (?, ?, ?, ?)
+             ON CONFLICT(user_id) DO UPDATE SET
+                 public_key  = excluded.public_key,
+                 private_key = excluded.private_key",
+        )
+        .bind(&uid)
+        .bind(&public_key)
+        .bind(&private_key)
+        .bind(&created_at)
+        .execute(&self.pool)
+        .await?;
+
+        Ok(())
+    }
+
+    async fn save_remote_review(&self, review: &Review) -> Result<()> {
+        let actor_url = match review.source() {
+            ReviewSource::Remote { actor_url } => actor_url.clone(),
+            ReviewSource::Local => {
+                return Err(anyhow!("save_remote_review called with a local review"));
+            }
+        };
+
+        let id = review.id().value().to_string();
+        let movie_id = review.movie_id().value().to_string();
+        let user_id = review.user_id().value().to_string();
+        let rating = review.rating().value() as i64;
+        let comment = review.comment().map(|c| c.value().to_string());
+        let watched_at = datetime_to_str(review.watched_at());
+        let created_at = datetime_to_str(review.created_at());
+
+        sqlx::query(
+            "INSERT OR IGNORE INTO reviews (id, movie_id, user_id, rating, comment, watched_at, created_at, remote_actor_url)
+             VALUES (?, ?, ?, ?, ?, ?, ?, ?)",
+        )
+        .bind(&id)
+        .bind(&movie_id)
+        .bind(&user_id)
+        .bind(rating)
+        .bind(&comment)
+        .bind(&watched_at)
+        .bind(&created_at)
+        .bind(&actor_url)
+        .execute(&self.pool)
+        .await?;
+
+        Ok(())
+    }
+}
--- a/crates/adapters/sqlite/src/lib.rs
+++ b/crates/adapters/sqlite/src/lib.rs
@@ -4,7 +4,7 @@ use domain::{
    events::DomainEvent,
    models::{
        DiaryEntry, DiaryFilter, DirectorStat, FeedEntry, Movie, MonthlyRating,
-        Review, ReviewHistory, SortDirection, UserStats, UserTrends,
+        Review, ReviewHistory, ReviewSource, SortDirection, UserStats, UserTrends,
        collections::{PageParams, Paginated},
    },
    ports::MovieRepository,
@@ -12,6 +12,7 @@ use domain::{
 };
 use sqlx::SqlitePool;

+mod federation;
 mod migrations;
 mod models;
 mod users;
@@ -21,6 +22,7 @@ use models::{
    UserTotalsRow, datetime_to_str,
 };

+pub use federation::SqliteFederationRepository;
 pub use users::SqliteUserRepository;

 fn format_year_month(ym: &str) -> String {
@@ -80,7 +82,7 @@ impl SqliteMovieRepository {
            SortDirection::Descending | SortDirection::ByRatingDesc => sqlx::query_as!(
                DiaryRow,
                "SELECT m.id, m.external_metadata_id, m.title, m.release_year, m.director, m.poster_path,
-                        r.id AS review_id, r.movie_id, r.user_id, r.rating, r.comment, r.watched_at, r.created_at
+                        r.id AS review_id, r.movie_id, r.user_id, r.rating, r.comment, r.watched_at, r.created_at, r.remote_actor_url
                 FROM reviews r
                 INNER JOIN movies m ON m.id = r.movie_id
                 ORDER BY r.watched_at DESC
@@ -95,7 +97,7 @@ impl SqliteMovieRepository {
            SortDirection::Ascending => sqlx::query_as!(
                DiaryRow,
                "SELECT m.id, m.external_metadata_id, m.title, m.release_year, m.director, m.poster_path,
-                        r.id AS review_id, r.movie_id, r.user_id, r.rating, r.comment, r.watched_at, r.created_at
+                        r.id AS review_id, r.movie_id, r.user_id, r.rating, r.comment, r.watched_at, r.created_at, r.remote_actor_url
                 FROM reviews r
                 INNER JOIN movies m ON m.id = r.movie_id
                 ORDER BY r.watched_at ASC
@@ -121,7 +123,7 @@ impl SqliteMovieRepository {
            SortDirection::Descending | SortDirection::ByRatingDesc => sqlx::query_as!(
                DiaryRow,
                "SELECT m.id, m.external_metadata_id, m.title, m.release_year, m.director, m.poster_path,
-                        r.id AS review_id, r.movie_id, r.user_id, r.rating, r.comment, r.watched_at, r.created_at
+                        r.id AS review_id, r.movie_id, r.user_id, r.rating, r.comment, r.watched_at, r.created_at, r.remote_actor_url
                 FROM reviews r
                 INNER JOIN movies m ON m.id = r.movie_id
                 WHERE r.movie_id = ?
@@ -138,7 +140,7 @@ impl SqliteMovieRepository {
            SortDirection::Ascending => sqlx::query_as!(
                DiaryRow,
                "SELECT m.id, m.external_metadata_id, m.title, m.release_year, m.director, m.poster_path,
-                        r.id AS review_id, r.movie_id, r.user_id, r.rating, r.comment, r.watched_at, r.created_at
+                        r.id AS review_id, r.movie_id, r.user_id, r.rating, r.comment, r.watched_at, r.created_at, r.remote_actor_url
                 FROM reviews r
                 INNER JOIN movies m ON m.id = r.movie_id
                 WHERE r.movie_id = ?
@@ -173,7 +175,7 @@ impl SqliteMovieRepository {
        sqlx::query_as!(
            DiaryRow,
            "SELECT m.id, m.external_metadata_id, m.title, m.release_year, m.director, m.poster_path,
-                    r.id AS review_id, r.movie_id, r.user_id, r.rating, r.comment, r.watched_at, r.created_at
+                    r.id AS review_id, r.movie_id, r.user_id, r.rating, r.comment, r.watched_at, r.created_at, r.remote_actor_url
             FROM reviews r
             INNER JOIN movies m ON m.id = r.movie_id
             WHERE r.user_id = ?
@@ -195,7 +197,7 @@ impl SqliteMovieRepository {
        sqlx::query_as!(
            DiaryRow,
            "SELECT m.id, m.external_metadata_id, m.title, m.release_year, m.director, m.poster_path,
-                    r.id AS review_id, r.movie_id, r.user_id, r.rating, r.comment, r.watched_at, r.created_at
+                    r.id AS review_id, r.movie_id, r.user_id, r.rating, r.comment, r.watched_at, r.created_at, r.remote_actor_url
             FROM reviews r
             INNER JOIN movies m ON m.id = r.movie_id
             WHERE r.user_id = ?
@@ -223,7 +225,7 @@ impl SqliteMovieRepository {
        sqlx::query_as!(
            FeedRow,
            "SELECT m.id, m.external_metadata_id, m.title, m.release_year, m.director, m.poster_path,
-                    r.id AS review_id, r.movie_id, r.user_id, r.rating, r.comment, r.watched_at, r.created_at,
+                    r.id AS review_id, r.movie_id, r.user_id, r.rating, r.comment, r.watched_at, r.created_at, r.remote_actor_url,
                    u.email AS user_email
             FROM reviews r
             INNER JOIN movies m ON m.id = r.movie_id
@@ -386,17 +388,22 @@ impl MovieRepository for SqliteMovieRepository {
        let comment = review.comment().map(|c| c.value().to_string());
        let watched_at = datetime_to_str(review.watched_at());
        let created_at = datetime_to_str(review.created_at());
+        let remote_actor_url = match review.source() {
+            ReviewSource::Local => None,
+            ReviewSource::Remote { actor_url } => Some(actor_url.clone()),
+        };

        sqlx::query!(
-            "INSERT INTO reviews (id, movie_id, user_id, rating, comment, watched_at, created_at)
-             VALUES (?, ?, ?, ?, ?, ?, ?)",
+            "INSERT INTO reviews (id, movie_id, user_id, rating, comment, watched_at, created_at, remote_actor_url)
+             VALUES (?, ?, ?, ?, ?, ?, ?, ?)",
            id,
            movie_id,
            user_id,
            rating,
            comment,
            watched_at,
-            created_at
+            created_at,
+            remote_actor_url
        )
        .execute(&self.pool)
        .await
@@ -464,7 +471,7 @@ impl MovieRepository for SqliteMovieRepository {
        let id = review_id.value().to_string();
        sqlx::query_as!(
            ReviewRow,
-            "SELECT id, movie_id, user_id, rating, comment, watched_at, created_at
+            "SELECT id, movie_id, user_id, rating, comment, watched_at, created_at, remote_actor_url
             FROM reviews WHERE id = ?",
            id
        )
@@ -510,7 +517,7 @@ impl MovieRepository for SqliteMovieRepository {

        let viewings = sqlx::query_as!(
            ReviewRow,
-            "SELECT id, movie_id, user_id, rating, comment, watched_at, created_at
+            "SELECT id, movie_id, user_id, rating, comment, watched_at, created_at, remote_actor_url
             FROM reviews WHERE movie_id = ? ORDER BY watched_at ASC",
            id_str
        )
@@ -573,7 +580,7 @@ impl MovieRepository for SqliteMovieRepository {
        let rows = sqlx::query_as!(
            DiaryRow,
            "SELECT m.id, m.external_metadata_id, m.title, m.release_year, m.director, m.poster_path,
-                    r.id AS review_id, r.movie_id, r.user_id, r.rating, r.comment, r.watched_at, r.created_at
+                    r.id AS review_id, r.movie_id, r.user_id, r.rating, r.comment, r.watched_at, r.created_at, r.remote_actor_url
             FROM reviews r
             INNER JOIN movies m ON m.id = r.movie_id
             WHERE r.user_id = ?
--- a/crates/adapters/sqlite/src/models.rs
+++ b/crates/adapters/sqlite/src/models.rs
@@ -1,7 +1,7 @@
 use chrono::NaiveDateTime;
 use domain::{
    errors::DomainError,
-    models::{DiaryEntry, FeedEntry, Movie, Review, UserSummary},
+    models::{DiaryEntry, FeedEntry, Movie, Review, ReviewSource, UserSummary},
    value_objects::{
        Comment, ExternalMetadataId, MovieId, MovieTitle, PosterPath, Rating, ReleaseYear,
        ReviewId, UserId,
@@ -49,6 +49,7 @@ pub(crate) struct ReviewRow {
    pub comment: Option<String>,
    pub watched_at: String,
    pub created_at: String,
+    pub remote_actor_url: Option<String>,
 }

 impl ReviewRow {
@@ -60,8 +61,12 @@ impl ReviewRow {
        let comment = self.comment.map(Comment::new).transpose()?;
        let watched_at = parse_datetime(&self.watched_at)?;
        let created_at = parse_datetime(&self.created_at)?;
+        let source = match self.remote_actor_url {
+            None => ReviewSource::Local,
+            Some(url) => ReviewSource::Remote { actor_url: url },
+        };
        Ok(Review::from_persistence(
-            id, movie_id, user_id, rating, comment, watched_at, created_at,
+            id, movie_id, user_id, rating, comment, watched_at, created_at, source,
        ))
    }
 }
@@ -82,6 +87,7 @@ pub(crate) struct DiaryRow {
    pub comment: Option<String>,
    pub watched_at: String,
    pub created_at: String,
+    pub remote_actor_url: Option<String>,
 }

 impl DiaryRow {
@@ -104,6 +110,7 @@ impl DiaryRow {
            comment: self.comment,
            watched_at: self.watched_at,
            created_at: self.created_at,
+            remote_actor_url: self.remote_actor_url,
        }
        .to_domain()?;

@@ -127,6 +134,7 @@ pub(crate) struct FeedRow {
    pub comment: Option<String>,
    pub watched_at: String,
    pub created_at: String,
+    pub remote_actor_url: Option<String>,
    pub user_email: String,
 }

@@ -146,6 +154,7 @@ impl FeedRow {
            comment: self.comment,
            watched_at: self.watched_at,
            created_at: self.created_at,
+            remote_actor_url: self.remote_actor_url,
        }
        .to_domain()?;
        Ok(FeedEntry::new(diary, self.user_email))
--- a/crates/adapters/template-askama/src/lib.rs
+++ b/crates/adapters/template-askama/src/lib.rs
@@ -1,12 +1,12 @@
 use askama::Template;
 use chrono::Datelike;
 use application::ports::{
-    ActivityFeedPageData, HtmlPageContext, HtmlRenderer, LoginPageData,
+    ActivityFeedPageData, FollowingPageData, HtmlPageContext, HtmlRenderer, LoginPageData,
    NewReviewPageData, ProfilePageData, RegisterPageData, UsersPageData,
 };
 use domain::models::{
-    DiaryEntry, FeedEntry, MonthActivity, MonthlyRating, UserStats, UserSummary, UserTrends,
-    collections::Paginated,
+    DiaryEntry, FeedEntry, MonthActivity, MonthlyRating, ReviewSource, UserStats, UserSummary,
+    UserTrends, collections::Paginated,
 };

 struct PageItem {
@@ -110,6 +110,24 @@ struct ProfileTemplate<'a> {
    monthly_rating_rows: Vec<MonthlyRatingRow<'a>>,
    heatmap: Vec<HeatmapCell>,
    page_items: Vec<PageItem>,
+    is_own_profile: bool,
+    error: Option<String>,
+    following_count: usize,
+}
+
+struct RemoteActorData {
+    handle: String,
+    display_name: Option<String>,
+    url: String,
+}
+
+#[derive(Template)]
+#[template(path = "following.html")]
+struct FollowingTemplate {
+    ctx: HtmlPageContext,
+    user_id: uuid::Uuid,
+    actors: Vec<RemoteActorData>,
+    error: Option<String>,
 }

 struct HeatmapCell {
@@ -276,6 +294,24 @@ impl HtmlRenderer for AskamaHtmlRenderer {
            monthly_rating_rows,
            heatmap,
            page_items: build_page_items(total_pages, current_page),
+            is_own_profile: data.is_own_profile,
+            error: data.error,
+            following_count: data.following_count,
+        }
+        .render()
+        .map_err(|e| e.to_string())
+    }
+
+    fn render_following_page(&self, data: FollowingPageData) -> Result<String, String> {
+        FollowingTemplate {
+            ctx: data.ctx,
+            user_id: data.user_id,
+            actors: data.actors.into_iter().map(|a| RemoteActorData {
+                handle: a.handle,
+                display_name: a.display_name,
+                url: a.url,
+            }).collect(),
+            error: data.error,
        }
        .render()
        .map_err(|e| e.to_string())
--- a/crates/adapters/template-askama/templates/activity_feed.html
+++ b/crates/adapters/template-askama/templates/activity_feed.html
@@ -27,6 +27,11 @@
      <div class="feed-meta">
        <a href="/users/{{ entry.review().user_id().value() }}" class="feed-user">{{ entry.user_display_name() }}</a>
        <span class="feed-time">{{ entry.review().watched_at().format("%b %-d, %Y") }}</span>
+        {% match entry.review().source() %}
+        {% when ReviewSource::Remote with { actor_url } %}
+        <span class="remote-badge" title="{{ actor_url }}">&#8599; federated</span>
+        {% when ReviewSource::Local %}
+        {% endmatch %}
      </div>
      {% if ctx.is_current_user(entry.review().user_id().value()) %}
      <form method="post" action="/reviews/{{ entry.review().id().value() }}/delete" class="delete-form">
--- a/crates/adapters/template-askama/templates/following.html
+++ b/crates/adapters/template-askama/templates/following.html
@@ -0,0 +1,26 @@
+{% extends "base.html" %}
+{% block content %}
+<h2>Following</h2>
+{% if let Some(err) = error %}
+<p class="error">{{ err }}</p>
+{% endif %}
+{% if actors.is_empty() %}
+<p>Not following anyone yet. Follow remote users from your <a href="/users/{{ user_id }}">profile page</a>.</p>
+{% else %}
+<ul class="following-list">
+{% for actor in actors %}
+<li class="following-item">
+  <strong>{{ actor.handle }}</strong>
+  {% if let Some(name) = actor.display_name %}
+  ({{ name }})
+  {% endif %}
+  <a href="{{ actor.url }}" target="_blank" rel="noopener noreferrer">{{ actor.url }}</a>
+  <form method="POST" action="/users/{{ user_id }}/unfollow" style="display:inline">
+    <input type="hidden" name="actor_url" value="{{ actor.url }}">
+    <button type="submit">Unfollow</button>
+  </form>
+</li>
+{% endfor %}
+</ul>
+{% endif %}
+{% endblock %}
--- a/crates/adapters/template-askama/templates/profile.html
+++ b/crates/adapters/template-askama/templates/profile.html
@@ -24,6 +24,20 @@
    </div>
  </div>

+  {% if is_own_profile %}
+  <section class="follow-section">
+    <h3>Follow remote user</h3>
+    <form method="POST" action="/users/{{ profile_user_id }}/follow">
+      <input type="text" name="handle" placeholder="user@instance.example.com" required>
+      <button type="submit">Follow</button>
+    </form>
+    {% if let Some(err) = error %}
+    <p class="error">{{ err }}</p>
+    {% endif %}
+  </section>
+  <a href="/users/{{ profile_user_id }}/following-list">View following ({{ following_count }})</a>
+  {% endif %}
+
  <div class="view-tabs">
    <a href="?view=recent" class="view-tab {% if view == "recent" %}active{% endif %}">Recent</a>
    <a href="?view=ratings" class="view-tab {% if view == "ratings" %}active{% endif %}">Top Rated</a>
--- a/crates/application/src/ports.rs
+++ b/crates/application/src/ports.rs
@@ -2,6 +2,12 @@ use uuid::Uuid;

 use domain::models::{DiaryEntry, FeedEntry, MonthActivity, UserStats, UserSummary, UserTrends, collections::Paginated};

+pub struct RemoteActorView {
+    pub handle: String,
+    pub display_name: Option<String>,
+    pub url: String,
+}
+
 pub struct HtmlPageContext {
    pub user_email: Option<String>,
    pub user_id: Option<Uuid>,
@@ -57,6 +63,16 @@ pub struct ProfilePageData {
    pub limit: u32,
    pub history: Option<Vec<MonthActivity>>,
    pub trends: Option<UserTrends>,
+    pub is_own_profile: bool,
+    pub error: Option<String>,
+    pub following_count: usize,
+}
+
+pub struct FollowingPageData {
+    pub ctx: HtmlPageContext,
+    pub user_id: Uuid,
+    pub actors: Vec<RemoteActorView>,
+    pub error: Option<String>,
 }

 pub trait HtmlRenderer: Send + Sync {
@@ -67,6 +83,7 @@ pub trait HtmlRenderer: Send + Sync {
    fn render_activity_feed_page(&self, data: ActivityFeedPageData) -> Result<String, String>;
    fn render_users_page(&self, data: UsersPageData) -> Result<String, String>;
    fn render_profile_page(&self, data: ProfilePageData) -> Result<String, String>;
+    fn render_following_page(&self, data: FollowingPageData) -> Result<String, String>;
 }

 pub trait RssFeedRenderer: Send + Sync {
--- a/crates/domain/src/models/mod.rs
+++ b/crates/domain/src/models/mod.rs
@@ -114,6 +114,18 @@ impl Movie {
    }
 }

+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum ReviewSource {
+    Local,
+    Remote { actor_url: String },
+}
+
+impl Default for ReviewSource {
+    fn default() -> Self {
+        ReviewSource::Local
+    }
+}
+
 #[derive(Clone, Debug)]
 pub struct Review {
    id: ReviewId,
@@ -123,6 +135,7 @@ pub struct Review {
    comment: Option<Comment>,
    watched_at: chrono::NaiveDateTime,
    created_at: chrono::NaiveDateTime,
+    source: ReviewSource,
 }

 impl Review {
@@ -141,6 +154,7 @@ impl Review {
            comment,
            watched_at,
            created_at: Utc::now().naive_utc(),
+            source: ReviewSource::Local,
        })
    }

@@ -152,6 +166,7 @@ impl Review {
        comment: Option<Comment>,
        watched_at: NaiveDateTime,
        created_at: NaiveDateTime,
+        source: ReviewSource,
    ) -> Self {
        Self {
            id,
@@ -161,6 +176,7 @@ impl Review {
            comment,
            watched_at,
            created_at,
+            source,
        }
    }

@@ -185,6 +201,9 @@ impl Review {
    pub fn created_at(&self) -> &NaiveDateTime {
        &self.created_at
    }
+    pub fn source(&self) -> &ReviewSource {
+        &self.source
+    }
    /// Returns [star1_filled, star2_filled, ..., star5_filled]
    pub fn stars(&self) -> [bool; 5] {
        let r = self.rating.value();
--- a/crates/presentation/Cargo.toml
+++ b/crates/presentation/Cargo.toml
@@ -26,11 +26,13 @@ metadata = { workspace = true }
 poster-fetcher = { workspace = true }
 poster-storage = { workspace = true }
 sqlite = { workspace = true }
+activitypub = { workspace = true }
 sqlx = { workspace = true }
 template-askama = { workspace = true }
 event-publisher = { workspace = true }
 rss = { workspace = true }
 infer = "0.19.0"
+percent-encoding = "2"

 [dev-dependencies]
 tower = { version = "0.5", features = ["util"] }
--- a/crates/presentation/src/dtos.rs
+++ b/crates/presentation/src/dtos.rs
@@ -234,11 +234,22 @@ impl From<DiaryQueryParams> for GetDiaryQuery {
    }
 }

+#[derive(Deserialize)]
+pub struct FollowForm {
+    pub handle: String,
+}
+
+#[derive(Deserialize)]
+pub struct UnfollowForm {
+    pub actor_url: String,
+}
+
 #[derive(serde::Deserialize, Default)]
 pub struct ProfileQueryParams {
    pub view: Option<String>,
    pub limit: Option<u32>,
    pub offset: Option<u32>,
+    pub error: Option<String>,
 }

 #[cfg(test)]
--- a/crates/presentation/src/extractors.rs
+++ b/crates/presentation/src/extractors.rs
@@ -149,6 +149,7 @@ mod tests {
            fn render_activity_feed_page(&self, _: application::ports::ActivityFeedPageData) -> Result<String, String> { panic!() }
            fn render_users_page(&self, _: application::ports::UsersPageData) -> Result<String, String> { panic!() }
            fn render_profile_page(&self, _: application::ports::ProfilePageData) -> Result<String, String> { panic!() }
+            fn render_following_page(&self, _: application::ports::FollowingPageData) -> Result<String, String> { panic!() }
        }

        struct PanicRssRenderer;
@@ -179,6 +180,7 @@ mod tests {
            },
            html_renderer: Arc::new(PanicRenderer),
            rss_renderer: Arc::new(PanicRssRenderer),
+            ap_service: test_ap_service().await,
        };

        let app = test_router(state);
@@ -228,7 +230,33 @@ mod tests {
        }
    }

-    fn panic_state() -> crate::state::AppState {
+    async fn test_ap_service() -> std::sync::Arc<activitypub::ActivityPubService> {
+        use std::sync::Arc;
+        let pool = sqlx::SqlitePool::connect("sqlite::memory:").await.unwrap();
+        sqlx::query("CREATE TABLE IF NOT EXISTS ap_keypairs (user_id TEXT PRIMARY KEY, public_key TEXT NOT NULL, private_key TEXT NOT NULL)")
+            .execute(&pool).await.unwrap();
+        sqlx::query("CREATE TABLE IF NOT EXISTS ap_remote_actors (url TEXT PRIMARY KEY, handle TEXT NOT NULL, inbox_url TEXT NOT NULL, shared_inbox_url TEXT, display_name TEXT)")
+            .execute(&pool).await.unwrap();
+        sqlx::query("CREATE TABLE IF NOT EXISTS ap_followers (local_user_id TEXT NOT NULL, remote_actor_url TEXT NOT NULL, status TEXT NOT NULL DEFAULT 'pending', PRIMARY KEY (local_user_id, remote_actor_url))")
+            .execute(&pool).await.unwrap();
+        sqlx::query("CREATE TABLE IF NOT EXISTS ap_following (local_user_id TEXT NOT NULL, remote_actor_url TEXT NOT NULL, PRIMARY KEY (local_user_id, remote_actor_url))")
+            .execute(&pool).await.unwrap();
+        let fed_repo = Arc::new(sqlite::SqliteFederationRepository::new(pool));
+        struct DummyUserRepo;
+        #[async_trait::async_trait] impl domain::ports::UserRepository for DummyUserRepo {
+            async fn find_by_email(&self, _: &domain::value_objects::Email) -> Result<Option<domain::models::User>, domain::errors::DomainError> { Ok(None) }
+            async fn save(&self, _: &domain::models::User) -> Result<(), domain::errors::DomainError> { Ok(()) }
+            async fn find_by_id(&self, _: &domain::value_objects::UserId) -> Result<Option<domain::models::User>, domain::errors::DomainError> { Ok(None) }
+            async fn list_with_stats(&self) -> Result<Vec<domain::models::UserSummary>, domain::errors::DomainError> { Ok(vec![]) }
+        }
+        Arc::new(
+            activitypub::ActivityPubService::new(fed_repo, Arc::new(DummyUserRepo), "http://localhost:3000".to_string(), true)
+                .await
+                .unwrap(),
+        )
+    }
+
+    async fn panic_state() -> crate::state::AppState {
        use std::sync::Arc;
        use application::context::AppContext;
        struct PanicRepo2;
@@ -266,6 +294,7 @@ mod tests {
            fn render_activity_feed_page(&self, _: application::ports::ActivityFeedPageData) -> Result<String, String> { panic!() }
            fn render_users_page(&self, _: application::ports::UsersPageData) -> Result<String, String> { panic!() }
            fn render_profile_page(&self, _: application::ports::ProfilePageData) -> Result<String, String> { panic!() }
+            fn render_following_page(&self, _: application::ports::FollowingPageData) -> Result<String, String> { panic!() }
        }
        struct PanicRssRenderer2;
        impl crate::ports::RssFeedRenderer for PanicRssRenderer2 {
@@ -286,10 +315,11 @@ mod tests {
            },
            html_renderer: Arc::new(PanicRenderer2),
            rss_renderer: Arc::new(PanicRssRenderer2),
+            ap_service: test_ap_service().await,
        }
    }

-    fn rejecting_state() -> crate::state::AppState {
+    async fn rejecting_state() -> crate::state::AppState {
        use std::sync::Arc;
        use application::context::AppContext;
        struct PanicRepo3;
@@ -326,6 +356,7 @@ mod tests {
            fn render_activity_feed_page(&self, _: application::ports::ActivityFeedPageData) -> Result<String, String> { panic!() }
            fn render_users_page(&self, _: application::ports::UsersPageData) -> Result<String, String> { panic!() }
            fn render_profile_page(&self, _: application::ports::ProfilePageData) -> Result<String, String> { panic!() }
+            fn render_following_page(&self, _: application::ports::FollowingPageData) -> Result<String, String> { panic!() }
        }
        struct PanicRssRenderer3;
        impl crate::ports::RssFeedRenderer for PanicRssRenderer3 {
@@ -345,12 +376,13 @@ mod tests {
            },
            html_renderer: Arc::new(PanicRenderer3),
            rss_renderer: Arc::new(PanicRssRenderer3),
+            ap_service: test_ap_service().await,
        }
    }

    #[tokio::test]
    async fn optional_cookie_user_returns_none_without_cookie() {
-        let app = test_router_optional(panic_state());
+        let app = test_router_optional(panic_state().await);
        let response = app
            .oneshot(Request::builder().uri("/optional").body(Body::empty()).unwrap())
            .await
@@ -362,7 +394,7 @@ mod tests {

    #[tokio::test]
    async fn optional_cookie_user_returns_none_with_invalid_token() {
-        let app = test_router_optional(rejecting_state());
+        let app = test_router_optional(rejecting_state().await);
        let response = app
            .oneshot(
                Request::builder()
@@ -380,7 +412,7 @@ mod tests {

    #[tokio::test]
    async fn required_cookie_user_redirects_without_cookie() {
-        let app = test_router_required(panic_state());
+        let app = test_router_required(panic_state().await);
        let response = app
            .oneshot(Request::builder().uri("/required").body(Body::empty()).unwrap())
            .await
@@ -391,7 +423,7 @@ mod tests {

    #[tokio::test]
    async fn required_cookie_user_redirects_with_invalid_token() {
-        let app = test_router_required(rejecting_state());
+        let app = test_router_required(rejecting_state().await);
        let response = app
            .oneshot(
                Request::builder()
--- a/crates/presentation/src/handlers.rs
+++ b/crates/presentation/src/handlers.rs
@@ -13,13 +13,13 @@ pub mod html {

    use application::{
        commands::{DeleteReviewCommand, LoginCommand, RegisterCommand},
-        ports::{HtmlPageContext, LoginPageData, NewReviewPageData, RegisterPageData},
+        ports::{FollowingPageData, HtmlPageContext, LoginPageData, NewReviewPageData, RegisterPageData, RemoteActorView},
        use_cases::{delete_review, log_review, login as login_uc, register as register_uc},
    };
    use domain::{errors::DomainError, value_objects::UserId};

    use crate::{
-        dtos::{DiaryQueryParams, ErrorQuery, LoginForm, LogReviewData, LogReviewForm, RegisterForm},
+        dtos::{DiaryQueryParams, ErrorQuery, FollowForm, LoginForm, LogReviewData, LogReviewForm, RegisterForm, UnfollowForm},
        extractors::{OptionalCookieUser, RequiredCookieUser},
        state::AppState,
    };
@@ -49,10 +49,8 @@ pub mod html {
    }

    fn encode_error(msg: &str) -> String {
-        msg.replace(' ', "+")
-            .replace('&', "%26")
-            .replace('=', "%3D")
-            .replace('"', "%22")
+        use percent_encoding::{NON_ALPHANUMERIC, utf8_percent_encode};
+        utf8_percent_encode(msg, NON_ALPHANUMERIC).to_string()
    }

    fn secure_flag() -> &'static str {
@@ -298,7 +296,7 @@ pub mod html {
        Path(profile_user_uuid): Path<Uuid>,
        Query(params): Query<crate::dtos::ProfileQueryParams>,
    ) -> impl IntoResponse {
-        let mut ctx = build_page_context(&state, user_id).await;
+        let mut ctx = build_page_context(&state, user_id.clone()).await;
        let view = params.view.unwrap_or_else(|| "recent".to_string());

        let profile_user = match state.app_ctx.user_repository
@@ -315,6 +313,21 @@ pub mod html {
        ctx.page_title = format!("{}'s Diary — Movies Diary", display_name);
        ctx.canonical_url = format!("{}/users/{}", state.app_ctx.config.base_url, profile_user_uuid);

+        let is_own_profile = user_id.as_ref()
+            .map(|u| u.value() == profile_user_uuid)
+            .unwrap_or(false);
+
+        let following_count = if is_own_profile {
+            if let Some(ref uid) = user_id {
+                state.ap_service.count_following(uid.clone()).await
+                    .unwrap_or(0)
+            } else {
+                0
+            }
+        } else {
+            0
+        };
+
        let query = application::queries::GetUserProfileQuery {
            user_id: profile_user_uuid,
            view: view.clone(),
@@ -343,6 +356,9 @@ pub mod html {
                    limit,
                    history: profile.history,
                    trends: profile.trends,
+                    is_own_profile,
+                    error: params.error,
+                    following_count,
                };
                match state.html_renderer.render_profile_page(data) {
                    Ok(html) => Html(html).into_response(),
@@ -352,6 +368,80 @@ pub mod html {
            Err(e) => (StatusCode::INTERNAL_SERVER_ERROR, e.to_string()).into_response(),
        }
    }
+
+    pub async fn follow_remote_user(
+        RequiredCookieUser(user_id): RequiredCookieUser,
+        State(state): State<AppState>,
+        Path(profile_user_uuid): Path<Uuid>,
+        Form(form): Form<FollowForm>,
+    ) -> impl IntoResponse {
+        if user_id.value() != profile_user_uuid {
+            return StatusCode::FORBIDDEN.into_response();
+        }
+        match state.ap_service.follow(user_id.clone(), &form.handle).await {
+            Ok(()) => Redirect::to(&format!("/users/{}", profile_user_uuid)).into_response(),
+            Err(e) => {
+                tracing::error!("follow error: {:?}", e);
+                let msg = encode_error(&e.to_string());
+                Redirect::to(&format!("/users/{}?error={}", profile_user_uuid, msg)).into_response()
+            }
+        }
+    }
+
+    pub async fn unfollow_remote_user(
+        RequiredCookieUser(user_id): RequiredCookieUser,
+        State(state): State<AppState>,
+        Path(profile_user_uuid): Path<Uuid>,
+        Form(form): Form<UnfollowForm>,
+    ) -> impl IntoResponse {
+        if user_id.value() != profile_user_uuid {
+            return StatusCode::FORBIDDEN.into_response();
+        }
+        match state.ap_service.unfollow(user_id.clone(), &form.actor_url).await {
+            Ok(()) => Redirect::to(&format!("/users/{}/following-list", profile_user_uuid)).into_response(),
+            Err(e) => {
+                let msg = encode_error(&e.to_string());
+                Redirect::to(&format!("/users/{}/following-list?error={}", profile_user_uuid, msg)).into_response()
+            }
+        }
+    }
+
+    pub async fn get_following_page(
+        RequiredCookieUser(user_id): RequiredCookieUser,
+        State(state): State<AppState>,
+        Path(profile_user_uuid): Path<Uuid>,
+        Query(params): Query<crate::dtos::ErrorQuery>,
+    ) -> impl IntoResponse {
+        if user_id.value() != profile_user_uuid {
+            return StatusCode::FORBIDDEN.into_response();
+        }
+        let mut ctx = build_page_context(&state, Some(user_id.clone())).await;
+        ctx.page_title = "Following — Movies Diary".to_string();
+        ctx.canonical_url = format!("{}/users/{}/following-list", state.app_ctx.config.base_url, profile_user_uuid);
+        match state.ap_service.get_following(user_id).await {
+            Ok(following) => {
+                let actors = following.into_iter().map(|a| RemoteActorView {
+                    handle: a.handle,
+                    display_name: a.display_name,
+                    url: a.url,
+                }).collect();
+                let data = FollowingPageData {
+                    ctx,
+                    user_id: profile_user_uuid,
+                    actors,
+                    error: params.error,
+                };
+                match state.html_renderer.render_following_page(data) {
+                    Ok(html) => Html(html).into_response(),
+                    Err(e) => (StatusCode::INTERNAL_SERVER_ERROR, e).into_response(),
+                }
+            }
+            Err(e) => {
+                tracing::error!("get_following error: {:?}", e);
+                (StatusCode::INTERNAL_SERVER_ERROR, "Failed to load following list").into_response()
+            }
+        }
+    }
 }

 pub mod posters {
--- a/crates/presentation/src/main.rs
+++ b/crates/presentation/src/main.rs
@@ -15,7 +15,8 @@ use auth::{AuthConfig, Argon2PasswordHasher, JwtAuthService};
 use metadata::MetadataClientImpl;
 use poster_fetcher::{PosterFetcherConfig, ReqwestPosterFetcher};
 use poster_storage::{PosterStorageAdapter, StorageConfig};
-use sqlite::{SqliteMovieRepository, SqliteUserRepository};
+use activitypub::ActivityPubService;
+use sqlite::{SqliteFederationRepository, SqliteMovieRepository, SqliteUserRepository};
 use rss::RssAdapter;
 use template_askama::AskamaHtmlRenderer;

@@ -70,7 +71,7 @@ async fn wire_dependencies() -> anyhow::Result<AppState> {
        PosterFetcherClient, PosterStorage, UserRepository,
    };
    let repository: Arc<dyn MovieRepository> = Arc::new(movie_repo);
-    let user_repository: Arc<dyn UserRepository> = Arc::new(SqliteUserRepository::new(pool));
+    let user_repository: Arc<dyn UserRepository> = Arc::new(SqliteUserRepository::new(pool.clone()));
    let metadata_client: Arc<dyn MetadataClient> = Arc::new(MetadataClientImpl::new_omdb(omdb_api_key));
    let poster_fetcher: Arc<dyn PosterFetcherClient> = Arc::new(ReqwestPosterFetcher::new(PosterFetcherConfig::from_env())?);
    let poster_storage: Arc<dyn PosterStorage> = Arc::new(PosterStorageAdapter::from_config(storage_config)?);
@@ -91,10 +92,23 @@ async fn wire_dependencies() -> anyhow::Result<AppState> {
        config: app_config.clone(),
    };

+    // Federation
+    let federation_repo = Arc::new(SqliteFederationRepository::new(pool));
+    let ap_service = Arc::new(
+        ActivityPubService::new(
+            federation_repo,
+            Arc::clone(&user_repository),
+            app_config.base_url.clone(),
+            cfg!(debug_assertions),
+        )
+        .await?,
+    );
+    let ap_event_handler = ap_service.event_handler();
+
    let poster_handler = PosterSyncHandler::new(handler_ctx, 3);
    let (event_publisher, event_worker) = create_event_channel(
        EventPublisherConfig::from_env(),
-        vec![Box::new(poster_handler)],
+        vec![Box::new(poster_handler), Box::new(ap_event_handler)],
    );
    tokio::spawn(event_worker.run());

@@ -116,6 +130,7 @@ async fn wire_dependencies() -> anyhow::Result<AppState> {
        rss_renderer: Arc::new(RssAdapter::new(
            std::env::var("BASE_URL").unwrap_or_else(|_| "http://localhost:3000".into()),
        )),
+        ap_service,
    })
 }

--- a/crates/presentation/src/routes.rs
+++ b/crates/presentation/src/routes.rs
@@ -9,6 +9,21 @@ use tower_http::{services::ServeDir, trace::TraceLayer};

 use crate::{handlers, state::AppState};

+/// Build an ActivityPub router from the service, excluding routes that
+/// conflict with HTML routes (/users/{id} and /users/{id}/following).
+/// Those AP endpoints are still served via the federation middleware layer
+/// applied to the whole AP router scope; the conflicting paths will need
+/// content-negotiation wrappers added in Phase 5.
+fn ap_routes(state: &AppState) -> Router {
+    let config = state.ap_service.federation_config();
+    Router::new()
+        .route("/.well-known/webfinger", routing::get(activitypub::webfinger::webfinger_handler))
+        .route("/users/{user_id}/inbox", routing::post(activitypub::inbox::inbox_handler))
+        .route("/users/{user_id}/outbox", routing::get(activitypub::outbox::outbox_handler))
+        .route("/users/{user_id}/followers", routing::get(activitypub::followers_handler::followers_handler))
+        .layer(config.middleware())
+}
+
 /// Simple global rate limiter: tracks request count per 60-second window.
 /// Not per-IP — suitable for a low-traffic personal app.
 #[derive(Clone)]
@@ -47,12 +62,14 @@ impl RateLimiter {

 pub fn build_router(state: AppState) -> Router {
    let rate_limit = state.app_ctx.config.rate_limit;
+    let ap_router = ap_routes(&state);
    Router::new()
        .merge(html_routes(rate_limit))
        .merge(api_routes(rate_limit))
        .nest_service("/static", ServeDir::new("static"))
        .layer(TraceLayer::new_for_http())
        .with_state(state)
+        .merge(ap_router)
 }

 fn html_routes(rate_limit: u64) -> Router<AppState> {
@@ -87,6 +104,18 @@ fn html_routes(rate_limit: u64) -> Router<AppState> {
            "/users/{id}",
            routing::get(handlers::html::get_user_profile),
        )
+        .route(
+            "/users/{id}/follow",
+            routing::post(handlers::html::follow_remote_user),
+        )
+        .route(
+            "/users/{id}/unfollow",
+            routing::post(handlers::html::unfollow_remote_user),
+        )
+        .route(
+            "/users/{id}/following-list",
+            routing::get(handlers::html::get_following_page),
+        )
        .merge(auth)
        .route(
            "/reviews/new",
--- a/crates/presentation/src/state.rs
+++ b/crates/presentation/src/state.rs
@@ -1,5 +1,6 @@
 use std::sync::Arc;

+use activitypub::ActivityPubService;
 use application::context::AppContext;

 use crate::ports::{HtmlRenderer, RssFeedRenderer};
@@ -9,4 +10,5 @@ pub struct AppState {
    pub app_ctx: AppContext,
    pub html_renderer: Arc<dyn HtmlRenderer>,
    pub rss_renderer: Arc<dyn RssFeedRenderer>,
+    pub ap_service: Arc<ActivityPubService>,
 }
--- a/crates/presentation/tests/api_test.rs
+++ b/crates/presentation/tests/api_test.rs
@@ -88,6 +88,32 @@ impl UserRepository for NobodyUserRepo {
    async fn list_with_stats(&self) -> Result<Vec<domain::models::UserSummary>, DomainError> { panic!() }
 }

+async fn test_ap_service() -> Arc<activitypub::ActivityPubService> {
+    let pool = SqlitePool::connect("sqlite::memory:").await.unwrap();
+    sqlx::query("CREATE TABLE IF NOT EXISTS ap_keypairs (user_id TEXT PRIMARY KEY, public_key TEXT NOT NULL, private_key TEXT NOT NULL)")
+        .execute(&pool).await.unwrap();
+    sqlx::query("CREATE TABLE IF NOT EXISTS ap_remote_actors (url TEXT PRIMARY KEY, handle TEXT NOT NULL, inbox_url TEXT NOT NULL, shared_inbox_url TEXT, display_name TEXT)")
+        .execute(&pool).await.unwrap();
+    sqlx::query("CREATE TABLE IF NOT EXISTS ap_followers (local_user_id TEXT NOT NULL, remote_actor_url TEXT NOT NULL, status TEXT NOT NULL DEFAULT 'pending', PRIMARY KEY (local_user_id, remote_actor_url))")
+        .execute(&pool).await.unwrap();
+    sqlx::query("CREATE TABLE IF NOT EXISTS ap_following (local_user_id TEXT NOT NULL, remote_actor_url TEXT NOT NULL, PRIMARY KEY (local_user_id, remote_actor_url))")
+        .execute(&pool).await.unwrap();
+    let fed_repo = Arc::new(sqlite::SqliteFederationRepository::new(pool));
+    struct DummyUserRepo;
+    #[async_trait]
+    impl UserRepository for DummyUserRepo {
+        async fn find_by_email(&self, _: &Email) -> Result<Option<User>, DomainError> { Ok(None) }
+        async fn save(&self, _: &User) -> Result<(), DomainError> { Ok(()) }
+        async fn find_by_id(&self, _: &UserId) -> Result<Option<User>, DomainError> { Ok(None) }
+        async fn list_with_stats(&self) -> Result<Vec<domain::models::UserSummary>, DomainError> { Ok(vec![]) }
+    }
+    Arc::new(
+        activitypub::ActivityPubService::new(fed_repo, Arc::new(DummyUserRepo), "http://localhost:3000".to_string(), true)
+            .await
+            .unwrap(),
+    )
+}
+
 async fn test_app() -> Router {
    let pool = SqlitePool::connect("sqlite::memory:")
        .await
@@ -109,6 +135,7 @@ async fn test_app() -> Router {
        },
        html_renderer: Arc::new(AskamaHtmlRenderer::new()),
        rss_renderer: Arc::new(RssAdapter::new("http://localhost:3000".into())),
+        ap_service: test_ap_service().await,
    };

    routes::build_router(state)