fix: unblock discord listener concurrency

src/discord/monitor.test.ts

@@ -1,5 +1,5 @@
 import type { Guild } from "@buape/carbon";
-import { describe, expect, it } from "vitest";
+import { describe, expect, it, vi } from "vitest";
 import {
   allowListMatches,
   buildDiscordMediaPayload,
@@ -17,6 +17,7 @@ import {
   sanitizeDiscordThreadName,
   shouldEmitDiscordReactionNotification,
 } from "./monitor.js";
+import { DiscordMessageListener } from "./monitor/listeners.js";
 
 const fakeGuild = (id: string, name: string) => ({ id, name }) as Guild;
 
@@ -48,6 +49,85 @@ describe("registerDiscordListener", () => {
   });
 });
 
+describe("DiscordMessageListener", () => {
+  it("returns before the handler finishes", async () => {
+    let handlerResolved = false;
+    let resolveHandler: (() => void) | null = null;
+    const handlerPromise = new Promise<void>((resolve) => {
+      resolveHandler = () => {
+        handlerResolved = true;
+        resolve();
+      };
+    });
+    const handler = vi.fn(() => handlerPromise);
+    const listener = new DiscordMessageListener(handler);
+
+    await listener.handle(
+      {} as unknown as import("./monitor/listeners.js").DiscordMessageEvent,
+      {} as unknown as import("@buape/carbon").Client,
+    );
+
+    expect(handler).toHaveBeenCalledOnce();
+    expect(handlerResolved).toBe(false);
+
+    resolveHandler?.();
+    await handlerPromise;
+  });
+
+  it("logs handler failures", async () => {
+    const logger = {
+      warn: vi.fn(),
+      error: vi.fn(),
+    } as unknown as ReturnType<typeof import("../logging/subsystem.js").createSubsystemLogger>;
+    const handler = vi.fn(async () => {
+      throw new Error("boom");
+    });
+    const listener = new DiscordMessageListener(handler, logger);
+
+    await listener.handle(
+      {} as unknown as import("./monitor/listeners.js").DiscordMessageEvent,
+      {} as unknown as import("@buape/carbon").Client,
+    );
+    await new Promise((resolve) => setTimeout(resolve, 0));
+
+    expect(logger.error).toHaveBeenCalledWith(expect.stringContaining("discord handler failed"));
+  });
+
+  it("logs slow handlers after the threshold", async () => {
+    vi.useFakeTimers();
+    vi.setSystemTime(0);
+
+    try {
+      let resolveHandler: (() => void) | null = null;
+      const handlerPromise = new Promise<void>((resolve) => {
+        resolveHandler = resolve;
+      });
+      const handler = vi.fn(() => handlerPromise);
+      const logger = {
+        warn: vi.fn(),
+        error: vi.fn(),
+      } as unknown as ReturnType<typeof import("../logging/subsystem.js").createSubsystemLogger>;
+      const listener = new DiscordMessageListener(handler, logger);
+
+      await listener.handle(
+        {} as unknown as import("./monitor/listeners.js").DiscordMessageEvent,
+        {} as unknown as import("@buape/carbon").Client,
+      );
+
+      vi.setSystemTime(31_000);
+      resolveHandler?.();
+      await handlerPromise;
+      await Promise.resolve();
+
+      expect(logger.warn).toHaveBeenCalled();
+      const [, meta] = logger.warn.mock.calls[0] ?? [];
+      expect(meta?.durationMs).toBeGreaterThanOrEqual(30_000);
+    } finally {
+      vi.useRealTimers();
+    }
+  });
+});
+
 describe("discord allowlist helpers", () => {
   it("normalizes slugs", () => {
     expect(normalizeDiscordSlug("Friends of Clawd")).toBe("friends-of-clawd");