fix(dsh-plugin): reconnect the observation stream after a fatal failure

packages/dsh-plugin-browserskill/src/client/ObservationOverlay.tsx

@@ -239,14 +239,16 @@ function StopSessionAction(props: {
   );
 }
 
+type ChromeState = "active" | "idle" | "error" | "reconnecting";
+
 /** Flat status dot, specced after the BSK popup's ConnectionStatusIndicator. */
-function StatusDot({ state }: { state: "active" | "idle" | "error" | "dead" }) {
+function StatusDot({ state }: { state: ChromeState | "dead" }) {
   const color =
     state === "active"
       ? "bg-emerald-500"
       : state === "error"
         ? "bg-red-500"
-        : state === "dead"
+        : state === "dead" || state === "reconnecting"
           ? "bg-amber-500"
           : "bg-muted-foreground/40";
   return (
@@ -325,6 +327,8 @@ export function OverlayBody(props: {
   focus: SessionObservation | undefined;
   sessions: readonly SessionObservation[];
   available: boolean;
+  /** The live feed dropped; sessions shown are the last ones received. */
+  reconnecting: boolean;
   pinnedId: string | null;
   onTogglePin: (sessionId: string) => void;
   now: number;
@@ -342,6 +346,7 @@ export function OverlayBody(props: {
     focus,
     sessions,
     available,
+    reconnecting,
     pinnedId,
     onTogglePin,
     now,
@@ -380,12 +385,20 @@ export function OverlayBody(props: {
     void store.interrupt(focus.sessionId).finally(() => setInterrupting(false));
   };
 
-  const statusText = !available
-    ? "browser unavailable"
-    : focus === undefined
-      ? "no session"
-      : `${focus.sessionId} · ${focus.action === "idle" ? "idle" : focus.action} · ${formatElapsed(focus.since, now)}`;
-  const state = !available ? "error" : focus !== undefined ? statusOf(focus) : "idle";
+  const statusText = reconnecting
+    ? "reconnecting…"
+    : !available
+      ? "browser unavailable"
+      : focus === undefined
+        ? "no session"
+        : `${focus.sessionId} · ${focus.action === "idle" ? "idle" : focus.action} · ${formatElapsed(focus.since, now)}`;
+  const state: ChromeState = reconnecting
+    ? "reconnecting"
+    : !available
+      ? "error"
+      : focus !== undefined
+        ? statusOf(focus)
+        : "idle";
 
   return (
     <div
@@ -401,7 +414,7 @@ export function OverlayBody(props: {
         onPointerDown={onHeaderPointerDown}
         role="presentation"
       >
-        <StatusDot state={state === "error" ? "error" : state === "active" ? "active" : "idle"} />
+        <StatusDot state={state} />
         <span className={css["status-text"]}>{statusText}</span>
         {onUseFloating !== undefined ? (
           <IconAction
@@ -620,6 +633,7 @@ export function ObservationOverlay({ store }: { store: ObservationClientStore })
       focus={focus}
       sessions={snapshot.sessions}
       available={snapshot.available}
+      reconnecting={snapshot.reconnecting}
       pinnedId={pinnedId}
       onTogglePin={onTogglePin}
       now={now}
@@ -654,21 +668,28 @@ export function ObservationOverlay({ store }: { store: ObservationClientStore })
   if (snapshot.sessions.length === 0) return null;
 
   if (collapsed) {
-    const state = focus !== undefined ? statusOf(focus) : "idle";
+    const state: ChromeState = snapshot.reconnecting
+      ? "reconnecting"
+      : focus !== undefined
+        ? statusOf(focus)
+        : "idle";
     return (
       <button
         type="button"
         className={cn(css.capsule, "bsk-obs")}
         data-state={state}
+        data-testid="obs-capsule"
         aria-label="Expand browser observation overlay"
         onClick={() => setCollapsed(false)}
       >
         <StatusDot state={state} />
         <span className={css["capsule-text"]}>
           {snapshot.sessions.length} session{snapshot.sessions.length === 1 ? "" : "s"}
-          {focus !== undefined && focus.action !== "idle"
-            ? ` · ${focus.action} · ${formatElapsed(focus.since, now)}`
-            : ""}
+          {snapshot.reconnecting
+            ? " · reconnecting…"
+            : focus !== undefined && focus.action !== "idle"
+              ? ` · ${focus.action} · ${formatElapsed(focus.since, now)}`
+              : ""}
         </span>
       </button>
     );

packages/dsh-plugin-browserskill/src/client/observation-sidebar.tsx

@@ -100,6 +100,7 @@ export function ObservationSidebarTab({
       focus={focus}
       sessions={snapshot.sessions}
       available={snapshot.available}
+      reconnecting={snapshot.reconnecting}
       pinnedId={pinnedId}
       onTogglePin={onTogglePin}
       now={now}

packages/dsh-plugin-browserskill/src/client/observation-store.ts

@@ -12,6 +12,10 @@ import { ObservationPresentation } from "./observation-presentation";
 
 export interface EventSourceLike {
   onmessage: ((event: { data: string }) => void) | null;
+  /** Present on a real EventSource; test doubles may omit it. */
+  onerror?: ((event: unknown) => void) | null;
+  /** 0 CONNECTING, 1 OPEN, 2 CLOSED; undefined on test doubles. */
+  readyState?: number;
   close(): void;
 }
 
@@ -46,12 +50,25 @@ export interface OverlaySnapshot {
   readonly displayFrames: Readonly<Record<string, ThumbnailState>>;
   /** False when the host reports the browser/daemon as unreachable. */
   readonly available: boolean;
+  /**
+   * True from a stream error until the stream delivers a frame again;
+   * meanwhile sessions and availability are the last ones received.
+   */
+  readonly reconnecting: boolean;
 }
 
 const EVENTS_URL = "/bsk-observation/events";
 const INTERRUPT_URL = "/bsk-observation/interrupt";
 const STOP_URL = "/bsk-observation/stop";
 const THUMBNAIL_RETRY_DELAYS_MS = [1000, 3000];
+/**
+ * Backoff for re-creating the live event stream after a *fatal* failure.
+ * A non-200 response (for example the observation route answering 404 while
+ * the plugin is still starting, or right after a plugin reload) is terminal
+ * for an EventSource: the browser never retries it. Without this the view
+ * stays empty until the page is reloaded.
+ */
+const EVENT_STREAM_RETRY_DELAYS_MS = [1000, 3000, 10000, 30000];
 
 function revoke(url: string | undefined): void {
   if (url !== undefined && typeof URL.revokeObjectURL === "function") {
@@ -71,14 +88,19 @@ export class ObservationClientStore {
   private readonly retryCounts = new Map<string, number>();
   private listeners = new Set<() => void>();
   private events: EventSourceLike | undefined;
+  /** Pending re-creation of the event stream after a fatal failure. */
+  private reconnectTimer: ReturnType<typeof setTimeout> | undefined;
+  private reconnectAttempts = 0;
   private snapshot: OverlaySnapshot = {
     sessions: [],
     subscribed: false,
     thumbnails: {},
     displayFrames: {},
     available: true,
+    reconnecting: false,
   };
   private available = true;
+  private reconnecting = false;
   private started = false;
   /** Refcount of mounted consumers (overlay card, sidebar tab, sidebar fiber). */
   private consumers = 0;
@@ -100,6 +122,7 @@ export class ObservationClientStore {
       thumbnails: Object.fromEntries(this.thumbs),
       displayFrames: this.buildDisplayFrames(),
       available: this.available,
+      reconnecting: this.reconnecting,
     };
     for (const listener of [...this.listeners]) listener();
   }
@@ -136,6 +159,8 @@ export class ObservationClientStore {
   }
 
   private connectEvents(): void {
+    clearTimeout(this.reconnectTimer);
+    this.reconnectTimer = undefined;
     const previous = this.events;
     this.events = undefined;
     previous?.close();
@@ -151,8 +176,36 @@ export class ObservationClientStore {
       } catch {
         return;
       }
+      // Healthy traffic resets the backoff and ends the outage.
+      this.reconnectAttempts = 0;
+      this.reconnecting = false;
       this.apply(event);
     };
+    // A non-200 response is fatal for an EventSource: the browser fails the
+    // connection permanently and never retries it. Transient drops keep
+    // readyState 0/1 and are still retried by the EventSource itself, so only
+    // a CLOSED (2) readyState asks us to rebuild the stream.
+    events.onerror = () => {
+      if (!this.started || this.events !== events) return;
+      if (events.readyState === undefined || events.readyState === 2) this.scheduleReconnect();
+      if (this.reconnecting) return;
+      this.reconnecting = true;
+      this.publish();
+    };
+  }
+
+  /** Re-create the stream after a fatal failure, with a bounded backoff. */
+  private scheduleReconnect(): void {
+    if (this.reconnectTimer !== undefined) return;
+    const index = Math.min(this.reconnectAttempts, EVENT_STREAM_RETRY_DELAYS_MS.length - 1);
+    const delay = EVENT_STREAM_RETRY_DELAYS_MS[index];
+    if (delay === undefined) return;
+    this.reconnectAttempts += 1;
+    this.reconnectTimer = setTimeout(() => {
+      this.reconnectTimer = undefined;
+      if (!this.started) return;
+      this.connectEvents();
+    }, delay);
   }
 
   /** Every initial connection and reconnect starts with the server's snapshot. */
@@ -168,6 +221,10 @@ export class ObservationClientStore {
     this.events = undefined;
     this.started = false;
     previous?.close();
+    clearTimeout(this.reconnectTimer);
+    this.reconnectTimer = undefined;
+    this.reconnectAttempts = 0;
+    this.reconnecting = false;
     this.clearThumbnails();
     this.sessions.clear();
     this.available = true;

packages/dsh-plugin-browserskill/tests/client/observation-overlay.test.tsx

@@ -197,6 +197,68 @@ describe("ObservationOverlay", () => {
     expect(screen.getByTestId("obs-card")).toBeTruthy();
   });
 
+  it("never commits the card without sessions, even while the feed is down", async () => {
+    const h = makeHarness([]);
+    const inserted: Node[] = [];
+    const collect = (records: MutationRecord[]) => {
+      for (const record of records) inserted.push(...record.addedNodes);
+    };
+    const observer = new MutationObserver(collect);
+    observer.observe(document.body, { childList: true, subtree: true });
+    render(<ObservationOverlay store={h.store} />);
+    await waitFor(() => expect(h.es).not.toThrow());
+    act(() => {
+      h.es().readyState = 2;
+      h.es().onerror?.({});
+    });
+    collect(observer.takeRecords());
+    observer.disconnect();
+    expect(h.store.getSnapshot().reconnecting).toBe(true);
+    const cardCommitted = inserted.some(
+      (node) => node instanceof Element && node.closest("[data-obs-card]") !== null,
+    );
+    expect(cardCommitted).toBe(false);
+  });
+
+  it("marks a live session as reconnecting until the feed recovers", async () => {
+    const h = makeHarness([BUSY]);
+    render(<ObservationOverlay store={h.store} />);
+    await screen.findByText(/s1 · clicking/);
+    act(() => {
+      h.es().readyState = 0;
+      h.es().onerror?.({});
+    });
+    const header = screen.getByTestId("obs-header");
+    expect(header.textContent).toContain("reconnecting…");
+    expect(header.querySelector("[data-state]")?.getAttribute("data-state")).toBe("reconnecting");
+    expect(screen.queryByText(/s1 · clicking/)).toBeNull();
+    act(() => h.emitRaw({ type: "snapshot", sessions: [BUSY], available: true }));
+    expect(header.textContent).not.toContain("reconnecting");
+    expect(header.querySelector("[data-state]")?.getAttribute("data-state")).toBe("active");
+    expect(screen.getByText(/s1 · clicking/)).toBeTruthy();
+  });
+
+  it("collapses to a capsule that drops stale action timing while reconnecting", async () => {
+    const h = makeHarness([BUSY]);
+    render(<ObservationOverlay store={h.store} />);
+    await screen.findByText(/s1 · clicking/);
+    fireEvent.click(screen.getByRole("button", { name: "Collapse" }));
+    const capsule = await screen.findByTestId("obs-capsule");
+    expect(capsule.textContent).toContain("clicking");
+    expect(capsule.getAttribute("data-state")).toBe("active");
+    act(() => {
+      h.es().readyState = 0;
+      h.es().onerror?.({});
+    });
+    expect(capsule.textContent).toContain("reconnecting…");
+    expect(capsule.textContent).not.toContain("clicking");
+    expect(capsule.getAttribute("data-state")).toBe("reconnecting");
+    expect(capsule.querySelector("[data-state]")?.getAttribute("data-state")).toBe("reconnecting");
+    act(() => h.emitRaw({ type: "snapshot", sessions: [BUSY], available: true }));
+    expect(capsule.textContent).toContain("clicking");
+    expect(capsule.getAttribute("data-state")).toBe("active");
+  });
+
   it("shows the status row and a placeholder without a thumbnail", async () => {
     const h = makeHarness([BUSY]);
     render(<ObservationOverlay store={h.store} />);