feat: decode activity SSE events and expose tracker total

src/lib/event-feed.ts

@@ -8,6 +8,12 @@ export function decodeEvent(msg: SseMessage): FeedEvent | null {
     if (!outer.data) return null;
     const inner = JSON.parse(outer.data) as Record<string, unknown>;
 
+    if (outer.type === "activity") {
+      const id = typeof inner.id === "number" ? inner.id : Number.NaN;
+      if (Number.isFinite(id)) return { type: "activity", id };
+      return null;
+    }
+
     if (outer.type === "inflight") {
       const operation = inner.operation as string;
       if (operation === "remove") {

src/lib/inflight-tracker.ts

@@ -15,6 +15,7 @@ export interface ModelState {
 export type FeedEvent =
   | { type: "inflight"; operation: "snapshot" | "add"; requests: InflightRequest[] }
   | { type: "inflight"; operation: "remove"; id: string }
+  | { type: "activity"; id: number }
   | { type: "modelStatus"; models: ModelState[] };
 
 export type ModelRuntimeState = "stopped" | "loading" | "ready";
@@ -44,6 +45,10 @@ export class InflightTracker {
     return n;
   }
 
+  total(): number {
+    return this.requests.size;
+  }
+
   state(modelId: string): ModelRuntimeState | undefined {
     return this.states.get(modelId);
   }

tests/event-feed.test.ts

@@ -117,3 +117,12 @@ test("decodeEvent handles inflight with a non-array requests field and no reques
     assert.deepEqual(ev.requests, []);
   }
 });
+
+test("decodeEvent parses an activity event with an id", () => {
+  const msg: SseMessage = {
+    event: "message",
+    data: JSON.stringify({ type: "activity", data: JSON.stringify({ id: 817 }) }),
+  };
+  const ev = decodeEvent(msg);
+  assert.deepEqual(ev, { type: "activity", id: 817 });
+});

tests/inflight-tracker.test.ts

@@ -63,3 +63,13 @@ test("modelStatus normalizes states", () => {
   assert.equal(tracker.state("D"), "stopped");
   assert.equal(tracker.state("missing"), undefined);
 });
+
+test("total sums in-flight requests across all models", () => {
+  const tracker = new InflightTracker();
+  assert.equal(tracker.total(), 0);
+  tracker.apply({ type: "inflight", operation: "add", requests: [{ model: "A", id: "1" }, { model: "B", id: "2" }] });
+  tracker.apply({ type: "inflight", operation: "add", requests: [{ model: "A", id: "3" }] });
+  assert.equal(tracker.total(), 3);
+  tracker.apply({ type: "inflight", operation: "remove", id: "1" });
+  assert.equal(tracker.total(), 2);
+});