feat(v1.1.6): realtime channels + v1.1.5 follow-ups + version bumps

Server-side realtime SSE on per-app pub/sub topics, plus the three
v1.1.5 follow-ups and the version bumps.

Realtime:
- topics registry (0021) + admin endpoints + Capability::AppTopicManage
  (-> app:admin; no new scope).
- GET /realtime/topics/{topic} SSE endpoint (orchestrator-core data
  plane): Host -> app, RealtimeAuthority gate (404 missing/internal,
  401 bad/absent token), broadcast::Receiver stream + heartbeat.
- RealtimeBroadcaster / RealtimeEvent / RealtimeAuthority traits
  (picloud-shared); InProcessBroadcaster + GC (orchestrator-core);
  DB-backed RealtimeAuthorityImpl (manager-core). Publish path fans out
  to in-process subscribers after the durable outbox commit (best-effort,
  panic-isolated).
- HMAC subscriber tokens (subscriber_token.rs) + app_secrets table (0022)
  + pubsub::subscriber_token SDK (schema 1.6 -> 1.7). TTL clamp + env
  overrides.
- Dashboard Topics tab (register/list/edit/delete, prominent external
  badge, flip confirmation).

v1.1.5 follow-ups:
- Empty blobs accepted (NewFile/FileUpdate::validate) + round-trip test.
- Orphan *.tmp.* sweeper (spawn_files_orphan_sweep).
- Dispatcher e2e tests, one per trigger kind (DATABASE_URL-gated).

Versions: workspace 1.1.6, SDK 1.7, dashboard 0.12.0. Schema-snapshot
golden re-blessed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/orchestrator-core/src/lib.rs

@@ -12,6 +12,8 @@ pub mod api;
 pub mod client;
 pub mod gate;
 pub mod inbox;
+pub mod realtime;
+pub mod realtime_api;
 pub mod resolver;
 pub mod routing;
 
@@ -19,4 +21,8 @@ pub use api::{data_plane_router, user_routes_router, DataPlaneState};
 pub use client::{ExecutorClient, LocalExecutorClient, RemoteExecutorClient, ScriptIdentity};
 pub use gate::{AcquireError, ExecutionGate};
 pub use inbox::InboxRegistry;
+pub use realtime::{spawn_realtime_gc, InProcessBroadcaster, DEFAULT_BROADCAST_CAPACITY};
+pub use realtime_api::{
+    heartbeat_secs_from_env, realtime_router, RealtimeState, DEFAULT_HEARTBEAT_SECS,
+};
 pub use resolver::{ResolverError, ScriptResolver};

crates/orchestrator-core/src/realtime.rs

@@ -0,0 +1,242 @@
+//! In-process `RealtimeBroadcaster` — the SSE fan-out registry (v1.1.6).
+//!
+//! Sibling of [`crate::inbox::InboxRegistry`], but multi-receiver and
+//! repeated-event: a `Mutex<HashMap<(AppId, topic), broadcast::Sender>>`
+//! over `tokio::sync::broadcast` instead of a oneshot map. The publish
+//! side ([`PubsubServiceImpl`]) and the SSE subscribe side both hold one
+//! shared `Arc<InProcessBroadcaster>`.
+//!
+//! Delivery is best-effort: each channel has a bounded buffer
+//! (`PICLOUD_REALTIME_BROADCAST_CAPACITY`, default 64); a slow consumer
+//! that falls behind sees the oldest events dropped (standard
+//! `broadcast` lag semantics — the receiver gets `RecvError::Lagged`).
+//! SSE's transport-layer auto-reconnect is the recovery path; there's no
+//! server-side replay in v1.1.6.
+//!
+//! Channels are created lazily on first subscribe. A periodic GC task
+//! ([`spawn_realtime_gc`]) drops senders whose receiver count has fallen
+//! to zero so one-shot subscribers don't grow the map unboundedly.
+//!
+//! Cluster mode (v1.3+) swaps this for a Postgres `LISTEN/NOTIFY`-backed
+//! resolver behind the same `RealtimeBroadcaster` trait.
+
+use std::collections::HashMap;
+use std::sync::{Arc, Mutex};
+use std::time::Duration;
+
+use async_trait::async_trait;
+use picloud_shared::{AppId, BroadcasterError, RealtimeBroadcaster, RealtimeEvent};
+use tokio::sync::broadcast;
+
+/// Default per-channel broadcast buffer depth.
+pub const DEFAULT_BROADCAST_CAPACITY: usize = 64;
+const ENV_CAPACITY: &str = "PICLOUD_REALTIME_BROADCAST_CAPACITY";
+
+/// Default GC sweep interval for empty channels.
+pub const DEFAULT_GC_INTERVAL_SECS: u64 = 60;
+
+pub struct InProcessBroadcaster {
+    inner: Mutex<HashMap<(AppId, String), broadcast::Sender<RealtimeEvent>>>,
+    capacity: usize,
+}
+
+impl InProcessBroadcaster {
+    #[must_use]
+    pub fn new(capacity: usize) -> Self {
+        Self {
+            inner: Mutex::new(HashMap::new()),
+            capacity: capacity.max(1),
+        }
+    }
+
+    /// Build from `PICLOUD_REALTIME_BROADCAST_CAPACITY` (default 64).
+    #[must_use]
+    pub fn from_env() -> Self {
+        let capacity = match std::env::var(ENV_CAPACITY) {
+            Err(_) => DEFAULT_BROADCAST_CAPACITY,
+            Ok(v) => match v.parse::<usize>() {
+                Ok(n) if n > 0 => n,
+                Ok(_) => {
+                    tracing::warn!(env = ENV_CAPACITY, value = %v, "must be > 0; using default");
+                    DEFAULT_BROADCAST_CAPACITY
+                }
+                Err(e) => {
+                    tracing::warn!(env = ENV_CAPACITY, value = %v, error = %e, "invalid; using default");
+                    DEFAULT_BROADCAST_CAPACITY
+                }
+            },
+        };
+        Self::new(capacity)
+    }
+
+    /// Number of live channels in the map (test/observability helper).
+    #[must_use]
+    pub fn channel_count(&self) -> usize {
+        self.inner.lock().map(|g| g.len()).unwrap_or(0)
+    }
+
+    /// Drop senders with zero receivers. Returns how many were removed.
+    /// Called periodically by [`spawn_realtime_gc`].
+    pub fn gc(&self) -> usize {
+        let Ok(mut g) = self.inner.lock() else {
+            return 0;
+        };
+        let before = g.len();
+        g.retain(|_, tx| tx.receiver_count() > 0);
+        before - g.len()
+    }
+}
+
+#[async_trait]
+impl RealtimeBroadcaster for InProcessBroadcaster {
+    async fn subscribe(
+        &self,
+        app_id: AppId,
+        topic: &str,
+    ) -> Result<broadcast::Receiver<RealtimeEvent>, BroadcasterError> {
+        let mut g = self
+            .inner
+            .lock()
+            .map_err(|_| BroadcasterError::Unavailable("broadcaster map poisoned".into()))?;
+        let tx = g
+            .entry((app_id, topic.to_string()))
+            .or_insert_with(|| broadcast::channel(self.capacity).0);
+        Ok(tx.subscribe())
+    }
+
+    async fn publish(&self, app_id: AppId, topic: &str, event: RealtimeEvent) {
+        let Ok(g) = self.inner.lock() else {
+            return;
+        };
+        // Only fan out to an existing channel: a topic with no live
+        // subscribers has no sender (publish never creates one). `send`
+        // returns Err iff every receiver has dropped — a benign no-op.
+        if let Some(tx) = g.get(&(app_id, topic.to_string())) {
+            let _ = tx.send(event);
+        }
+    }
+
+    async fn drop_topic(&self, app_id: AppId, topic: &str) {
+        if let Ok(mut g) = self.inner.lock() {
+            // Removing the sender closes the channel; existing receivers
+            // observe `RecvError::Closed` and disconnect cleanly.
+            g.remove(&(app_id, topic.to_string()));
+        }
+    }
+}
+
+/// Spawn the background GC sweep that drops empty channels every
+/// `interval_secs` (default [`DEFAULT_GC_INTERVAL_SECS`]). Spawned at
+/// startup alongside the other housekeeping tasks.
+pub fn spawn_realtime_gc(broadcaster: Arc<InProcessBroadcaster>, interval_secs: u64) {
+    let period = Duration::from_secs(interval_secs.max(1));
+    tokio::spawn(async move {
+        let mut ticker = tokio::time::interval(period);
+        ticker.tick().await; // skip the immediate first fire
+        loop {
+            ticker.tick().await;
+            let removed = broadcaster.gc();
+            if removed > 0 {
+                tracing::debug!(removed, "realtime broadcaster GC dropped empty channels");
+            }
+        }
+    });
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use chrono::Utc;
+    use serde_json::json;
+
+    fn event(topic: &str, n: i64) -> RealtimeEvent {
+        RealtimeEvent {
+            topic: topic.to_string(),
+            message: json!({ "n": n }),
+            published_at: Utc::now(),
+        }
+    }
+
+    #[tokio::test]
+    async fn multiple_subscribers_each_receive_each_event() {
+        let b = InProcessBroadcaster::new(16);
+        let app = AppId::new();
+        let mut rx1 = b.subscribe(app, "chat").await.unwrap();
+        let mut rx2 = b.subscribe(app, "chat").await.unwrap();
+
+        b.publish(app, "chat", event("chat", 1)).await;
+        b.publish(app, "chat", event("chat", 2)).await;
+
+        for rx in [&mut rx1, &mut rx2] {
+            assert_eq!(rx.recv().await.unwrap().message, json!({ "n": 1 }));
+            assert_eq!(rx.recv().await.unwrap().message, json!({ "n": 2 }));
+        }
+    }
+
+    #[tokio::test]
+    async fn dropped_subscriber_does_not_leak_after_gc() {
+        let b = InProcessBroadcaster::new(16);
+        let app = AppId::new();
+        let rx = b.subscribe(app, "t").await.unwrap();
+        assert_eq!(b.channel_count(), 1);
+        drop(rx);
+        // GC reclaims the now-empty channel.
+        assert_eq!(b.gc(), 1);
+        assert_eq!(b.channel_count(), 0);
+    }
+
+    #[tokio::test]
+    async fn drop_topic_disconnects_existing_subscribers() {
+        let b = InProcessBroadcaster::new(16);
+        let app = AppId::new();
+        let mut rx = b.subscribe(app, "t").await.unwrap();
+        b.drop_topic(app, "t").await;
+        // Sender gone → receiver observes a closed channel.
+        assert!(rx.recv().await.is_err());
+        assert_eq!(b.channel_count(), 0);
+    }
+
+    #[tokio::test]
+    async fn slow_consumer_loses_oldest_events() {
+        // Capacity 2: a consumer that never drains sees the oldest
+        // events dropped (broadcast Lagged semantics).
+        let b = InProcessBroadcaster::new(2);
+        let app = AppId::new();
+        let mut rx = b.subscribe(app, "t").await.unwrap();
+        for i in 0..5 {
+            b.publish(app, "t", event("t", i)).await;
+        }
+        // First recv reports the lag rather than event 0.
+        let first = rx.recv().await;
+        assert!(
+            matches!(first, Err(broadcast::error::RecvError::Lagged(_))),
+            "expected Lagged, got {first:?}"
+        );
+        // Subsequent recvs return the most recent buffered events.
+        let next = rx.recv().await.unwrap();
+        assert_eq!(next.message, json!({ "n": 3 }));
+    }
+
+    #[tokio::test]
+    async fn cross_app_isolation() {
+        let b = InProcessBroadcaster::new(16);
+        let app_a = AppId::new();
+        let app_b = AppId::new();
+        let mut rx_a = b.subscribe(app_a, "shared").await.unwrap();
+        let mut rx_b = b.subscribe(app_b, "shared").await.unwrap();
+
+        b.publish(app_a, "shared", event("shared", 1)).await;
+        // App B's subscriber must not see app A's publish.
+        assert_eq!(rx_a.recv().await.unwrap().message, json!({ "n": 1 }));
+        assert!(rx_b.try_recv().is_err());
+    }
+
+    #[tokio::test]
+    async fn publish_with_no_subscribers_is_noop() {
+        let b = InProcessBroadcaster::new(16);
+        let app = AppId::new();
+        // No subscriber → no sender created → no panic, nothing fanned out.
+        b.publish(app, "ghost", event("ghost", 1)).await;
+        assert_eq!(b.channel_count(), 0);
+    }
+}

crates/orchestrator-core/src/realtime_api.rs

@@ -0,0 +1,408 @@
+//! SSE realtime endpoint — `GET /realtime/topics/{topic}` (v1.1.6).
+//!
+//! This is a data-plane surface, deliberately NOT under `/api/`
+//! (realtime is its own versioning surface per the path scheme). It is
+//! merged at the router root by the `picloud` binary alongside
+//! `/healthz`, `/version`, and the user-route fallback.
+//!
+//! Handshake:
+//!   1. Resolve `Host` → `app_id` (two-phase dispatch). No app → 404.
+//!   2. Extract the token from `Authorization: Bearer <t>` OR `?token=<t>`
+//!      (EventSource can't set custom headers, so the query form is the
+//!      browser-compatible path).
+//!   3. Ask the injected [`RealtimeAuthority`]: missing/internal topic →
+//!      404, bad/absent token on a token-gated topic → 401, otherwise OK.
+//!   4. Acquire a `broadcast::Receiver` and stream events as SSE until
+//!      the client disconnects (dropping the receiver — the broadcaster
+//!      cleans up on its own).
+//!
+//! Heartbeats (`:` comment lines) keep idle proxies from closing the
+//! connection; interval is `PICLOUD_REALTIME_HEARTBEAT_SEC` (default 30).
+
+use std::sync::Arc;
+use std::time::Duration;
+
+use axum::extract::{Path, Query, State};
+use axum::http::{HeaderMap, StatusCode};
+use axum::response::sse::{Event, KeepAlive, Sse};
+use axum::response::{IntoResponse, Response};
+use axum::routing::get;
+use axum::Router;
+use picloud_shared::{RealtimeAuthority, RealtimeBroadcaster, SubscribeDenied};
+use serde::Deserialize;
+use tokio_stream::wrappers::BroadcastStream;
+use tokio_stream::{Stream, StreamExt};
+
+use crate::routing::AppDomainTable;
+
+/// Default heartbeat interval (seconds) for idle SSE connections.
+pub const DEFAULT_HEARTBEAT_SECS: u64 = 30;
+const ENV_HEARTBEAT: &str = "PICLOUD_REALTIME_HEARTBEAT_SEC";
+
+#[derive(Clone)]
+pub struct RealtimeState {
+    /// Host → app_id resolver (shared with the rest of the data plane).
+    pub app_domains: Arc<AppDomainTable>,
+    pub broadcaster: Arc<dyn RealtimeBroadcaster>,
+    pub authority: Arc<dyn RealtimeAuthority>,
+    pub heartbeat: Duration,
+}
+
+impl RealtimeState {
+    #[must_use]
+    pub fn new(
+        app_domains: Arc<AppDomainTable>,
+        broadcaster: Arc<dyn RealtimeBroadcaster>,
+        authority: Arc<dyn RealtimeAuthority>,
+    ) -> Self {
+        Self {
+            app_domains,
+            broadcaster,
+            authority,
+            heartbeat: Duration::from_secs(heartbeat_secs_from_env()),
+        }
+    }
+}
+
+/// Read `PICLOUD_REALTIME_HEARTBEAT_SEC` (default 30, must be > 0).
+#[must_use]
+pub fn heartbeat_secs_from_env() -> u64 {
+    match std::env::var(ENV_HEARTBEAT) {
+        Err(_) => DEFAULT_HEARTBEAT_SECS,
+        Ok(v) => match v.parse::<u64>() {
+            Ok(n) if n > 0 => n,
+            _ => {
+                tracing::warn!(env = ENV_HEARTBEAT, value = %v, "invalid; using default");
+                DEFAULT_HEARTBEAT_SECS
+            }
+        },
+    }
+}
+
+/// Router for the realtime SSE surface. Merged at the router root.
+#[must_use]
+pub fn realtime_router(state: RealtimeState) -> Router {
+    Router::new()
+        .route("/realtime/topics/{topic}", get(sse_topic))
+        .with_state(state)
+}
+
+#[derive(Debug, Deserialize)]
+struct TokenQuery {
+    token: Option<String>,
+}
+
+async fn sse_topic(
+    State(state): State<RealtimeState>,
+    Path(topic): Path<String>,
+    Query(q): Query<TokenQuery>,
+    headers: HeaderMap,
+) -> Response {
+    // 1. Host → app.
+    let host = headers
+        .get("host")
+        .and_then(|h| h.to_str().ok())
+        .unwrap_or("");
+    let Some(app_id) = state.app_domains.resolve_app(host) else {
+        return not_found("no app claims this host");
+    };
+
+    // 2. Token: Authorization: Bearer <t> takes precedence, else ?token=.
+    let token = bearer_token(&headers).or(q.token);
+
+    // 3. Authorize.
+    match state
+        .authority
+        .authorize_subscribe(app_id, &topic, token.as_deref())
+        .await
+    {
+        Ok(()) => {}
+        Err(SubscribeDenied::NotFound) => return not_found("topic not found"),
+        Err(SubscribeDenied::Unauthorized) => return unauthorized(),
+        Err(SubscribeDenied::Backend(e)) => {
+            tracing::error!(error = %e, "realtime authority backend error");
+            return (
+                StatusCode::INTERNAL_SERVER_ERROR,
+                axum::Json(serde_json::json!({ "error": "internal error" })),
+            )
+                .into_response();
+        }
+    }
+
+    // 4. Subscribe + stream.
+    let rx = match state.broadcaster.subscribe(app_id, &topic).await {
+        Ok(rx) => rx,
+        Err(e) => {
+            tracing::error!(error = %e, "failed to acquire realtime subscription");
+            return (
+                StatusCode::INTERNAL_SERVER_ERROR,
+                axum::Json(serde_json::json!({ "error": "internal error" })),
+            )
+                .into_response();
+        }
+    };
+
+    let stream = event_stream(rx);
+    let sse =
+        Sse::new(stream).keep_alive(KeepAlive::new().interval(state.heartbeat).text("heartbeat"));
+
+    // Sse sets Content-Type: text/event-stream + Cache-Control: no-cache.
+    // Add X-Accel-Buffering: no so an intermediate nginx doesn't buffer
+    // the stream (ignored by other proxies). Connection management is
+    // hyper's concern (and is hop-by-hop on HTTP/1.1, server-managed on
+    // HTTP/2), so we don't set Connection ourselves.
+    let mut resp = sse.into_response();
+    resp.headers_mut().insert(
+        "X-Accel-Buffering",
+        axum::http::HeaderValue::from_static("no"),
+    );
+    resp
+}
+
+/// Map the broadcast receiver into a stream of SSE events. Lagged
+/// notifications (slow consumer) are skipped; a closed channel
+/// (`drop_topic`, or all senders gone) ends the stream and the SSE
+/// connection closes cleanly.
+fn event_stream(
+    rx: tokio::sync::broadcast::Receiver<picloud_shared::RealtimeEvent>,
+) -> impl Stream<Item = Result<Event, std::convert::Infallible>> {
+    BroadcastStream::new(rx).filter_map(|item| {
+        let ev = item.ok()?; // drop Lagged errors
+        let payload = serde_json::json!({
+            "topic": ev.topic,
+            "message": ev.message,
+            "published_at": ev.published_at.to_rfc3339(),
+        });
+        Some(Ok(Event::default().data(payload.to_string())))
+    })
+}
+
+fn bearer_token(headers: &HeaderMap) -> Option<String> {
+    let raw = headers
+        .get(axum::http::header::AUTHORIZATION)?
+        .to_str()
+        .ok()?;
+    raw.strip_prefix("Bearer ")
+        .map(|t| t.trim().to_string())
+        .filter(|t| !t.is_empty())
+}
+
+fn not_found(msg: &str) -> Response {
+    (
+        StatusCode::NOT_FOUND,
+        axum::Json(serde_json::json!({ "error": msg })),
+    )
+        .into_response()
+}
+
+fn unauthorized() -> Response {
+    // Generic — never leaks which check failed.
+    (
+        StatusCode::UNAUTHORIZED,
+        axum::Json(serde_json::json!({ "error": "unauthorized" })),
+    )
+        .into_response()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::realtime::InProcessBroadcaster;
+    use crate::routing::AppDomainTable;
+    use async_trait::async_trait;
+    use axum::body::Body;
+    use axum::http::Request;
+    use picloud_shared::{AppId, RealtimeEvent};
+    use tower::ServiceExt; // oneshot
+
+    /// Authority stub returning a fixed verdict.
+    struct StubAuthority(Result<(), SubscribeDenied>);
+    #[async_trait]
+    impl RealtimeAuthority for StubAuthority {
+        async fn authorize_subscribe(
+            &self,
+            _: AppId,
+            _: &str,
+            _: Option<&str>,
+        ) -> Result<(), SubscribeDenied> {
+            self.0.clone()
+        }
+    }
+
+    /// App-domain table that maps a fixed host to a fixed app.
+    fn domains(host: &str, app: AppId) -> Arc<AppDomainTable> {
+        use crate::routing::{parse_app_domain, CompiledAppDomain};
+        let d = parse_app_domain(host).unwrap();
+        let table = AppDomainTable::new();
+        table.replace(vec![CompiledAppDomain {
+            app_id: app,
+            pattern: d.pattern,
+            shape_key: d.shape_key,
+        }]);
+        Arc::new(table)
+    }
+
+    fn state(
+        app: AppId,
+        host: &str,
+        verdict: Result<(), SubscribeDenied>,
+        broadcaster: Arc<dyn RealtimeBroadcaster>,
+    ) -> RealtimeState {
+        RealtimeState {
+            app_domains: domains(host, app),
+            broadcaster,
+            authority: Arc::new(StubAuthority(verdict)),
+            heartbeat: Duration::from_millis(100),
+        }
+    }
+
+    async fn get_status(state: RealtimeState, host: &str, topic: &str) -> StatusCode {
+        let app = realtime_router(state);
+        let req = Request::builder()
+            .uri(format!("/realtime/topics/{topic}"))
+            .header("host", host)
+            .body(Body::empty())
+            .unwrap();
+        app.oneshot(req).await.unwrap().status()
+    }
+
+    #[tokio::test]
+    async fn unknown_host_is_404() {
+        let app = AppId::new();
+        let st = state(
+            app,
+            "app.example.com",
+            Ok(()),
+            Arc::new(InProcessBroadcaster::new(8)),
+        );
+        // Request a different host → no app claims it.
+        assert_eq!(
+            get_status(st, "other.example.com", "chat").await,
+            StatusCode::NOT_FOUND
+        );
+    }
+
+    #[tokio::test]
+    async fn not_found_topic_is_404() {
+        let app = AppId::new();
+        let st = state(
+            app,
+            "app.example.com",
+            Err(SubscribeDenied::NotFound),
+            Arc::new(InProcessBroadcaster::new(8)),
+        );
+        assert_eq!(
+            get_status(st, "app.example.com", "ghost").await,
+            StatusCode::NOT_FOUND
+        );
+    }
+
+    #[tokio::test]
+    async fn unauthorized_token_is_401() {
+        let app = AppId::new();
+        let st = state(
+            app,
+            "app.example.com",
+            Err(SubscribeDenied::Unauthorized),
+            Arc::new(InProcessBroadcaster::new(8)),
+        );
+        assert_eq!(
+            get_status(st, "app.example.com", "chat").await,
+            StatusCode::UNAUTHORIZED
+        );
+    }
+
+    #[tokio::test]
+    async fn public_topic_returns_event_stream() {
+        let app = AppId::new();
+        let st = state(
+            app,
+            "app.example.com",
+            Ok(()),
+            Arc::new(InProcessBroadcaster::new(8)),
+        );
+        let appr = realtime_router(st);
+        let req = Request::builder()
+            .uri("/realtime/topics/chat")
+            .header("host", "app.example.com")
+            .body(Body::empty())
+            .unwrap();
+        let resp = appr.oneshot(req).await.unwrap();
+        assert_eq!(resp.status(), StatusCode::OK);
+        let ct = resp
+            .headers()
+            .get(axum::http::header::CONTENT_TYPE)
+            .unwrap()
+            .to_str()
+            .unwrap();
+        assert!(ct.starts_with("text/event-stream"));
+        assert_eq!(resp.headers().get("x-accel-buffering").unwrap(), "no");
+    }
+
+    #[tokio::test]
+    async fn subscribe_receives_published_event() {
+        let app = AppId::new();
+        let broadcaster = Arc::new(InProcessBroadcaster::new(8));
+        let st = state(app, "app.example.com", Ok(()), broadcaster.clone());
+        let appr = realtime_router(st);
+        let req = Request::builder()
+            .uri("/realtime/topics/chat")
+            .header("host", "app.example.com")
+            .body(Body::empty())
+            .unwrap();
+        let resp = appr.oneshot(req).await.unwrap();
+        assert_eq!(resp.status(), StatusCode::OK);
+
+        // The handler has subscribed; publish and read the first chunk.
+        // Give the streaming task a beat to register its receiver.
+        let mut body = resp.into_body().into_data_stream();
+        tokio::time::sleep(Duration::from_millis(50)).await;
+        broadcaster
+            .publish(
+                app,
+                "chat",
+                RealtimeEvent {
+                    topic: "chat".into(),
+                    message: serde_json::json!({ "hi": 1 }),
+                    published_at: chrono::Utc::now(),
+                },
+            )
+            .await;
+
+        let chunk = tokio::time::timeout(Duration::from_secs(2), body.next())
+            .await
+            .expect("a chunk within timeout")
+            .expect("stream item")
+            .expect("chunk ok");
+        let text = String::from_utf8_lossy(&chunk);
+        assert!(text.contains("data:"), "got: {text}");
+        assert!(text.contains("\"hi\":1"), "got: {text}");
+    }
+
+    #[tokio::test]
+    async fn heartbeat_fires_on_idle_connection() {
+        let app = AppId::new();
+        let broadcaster = Arc::new(InProcessBroadcaster::new(8));
+        // Hold a clone so the channel's sender outlives the router (which
+        // oneshot consumes) — otherwise the stream closes immediately.
+        let _keepalive = broadcaster.clone();
+        let st = state(app, "app.example.com", Ok(()), broadcaster);
+        let appr = realtime_router(st);
+        let req = Request::builder()
+            .uri("/realtime/topics/chat")
+            .header("host", "app.example.com")
+            .body(Body::empty())
+            .unwrap();
+        let resp = appr.oneshot(req).await.unwrap();
+        let mut body = resp.into_body().into_data_stream();
+        // No publish — with a 100ms heartbeat, a keep-alive comment must
+        // arrive well within a second.
+        let chunk = tokio::time::timeout(Duration::from_secs(1), body.next())
+            .await
+            .expect("heartbeat within timeout")
+            .expect("stream item")
+            .expect("chunk ok");
+        let text = String::from_utf8_lossy(&chunk);
+        assert!(text.starts_with(':'), "expected SSE comment, got: {text}");
+    }
+}