fix(bus): guard indexOf in InMemoryBus unsubscribe to prevent splice(-1)

apps/x/packages/core/src/application/lib/bus.test.ts

@@ -0,0 +1,55 @@
+import { describe, expect, it, vi } from "vitest";
+import type z from "zod";
+import { RunEvent } from "@x/shared/dist/runs.js";
+import { InMemoryBus } from "./bus.js";
+
+function makeEvent(runId: string): z.infer<typeof RunEvent> {
+    return {
+        type: "run-processing-start",
+        runId,
+        subflow: [],
+    } as z.infer<typeof RunEvent>;
+}
+
+describe("InMemoryBus", () => {
+    it("delivers events to all handlers subscribed to a runId", async () => {
+        const bus = new InMemoryBus();
+        const a = vi.fn(async () => {});
+        const b = vi.fn(async () => {});
+
+        await bus.subscribe("run-1", a);
+        await bus.subscribe("run-1", b);
+        await bus.publish(makeEvent("run-1"));
+
+        expect(a).toHaveBeenCalledTimes(1);
+        expect(b).toHaveBeenCalledTimes(1);
+    });
+
+    it("stops delivering to a handler after it unsubscribes", async () => {
+        const bus = new InMemoryBus();
+        const a = vi.fn(async () => {});
+
+        const unsubscribe = await bus.subscribe("run-1", a);
+        unsubscribe();
+        await bus.publish(makeEvent("run-1"));
+
+        expect(a).not.toHaveBeenCalled();
+    });
+
+    it("treats double-unsubscribe as a no-op and keeps other handlers (#491)", async () => {
+        const bus = new InMemoryBus();
+        const a = vi.fn(async () => {});
+        const b = vi.fn(async () => {});
+
+        const unsubscribeA = await bus.subscribe("run-1", a);
+        await bus.subscribe("run-1", b);
+
+        unsubscribeA();
+        unsubscribeA(); // second call must not remove handler b
+
+        await bus.publish(makeEvent("run-1"));
+
+        expect(a).not.toHaveBeenCalled();
+        expect(b).toHaveBeenCalledTimes(1);
+    });
+});

apps/x/packages/core/src/application/lib/bus.ts

@@ -29,7 +29,10 @@ export class InMemoryBus implements IBus {
         }
         this.subscribers.get(runId)!.push(handler);
         return () => {
-            this.subscribers.get(runId)!.splice(this.subscribers.get(runId)!.indexOf(handler), 1);
+            const handlers = this.subscribers.get(runId);
+            if (!handlers) return;
+            const idx = handlers.indexOf(handler);
+            if (idx >= 0) handlers.splice(idx, 1);
         };
     }
 }