fix(discord): dedupe inbound messages by message id

KoPang · KoPang · commit 6bc1c52c7bef · 2026-03-09T22:44:18.000+08:00
diff --git a/src/discord/monitor/message-handler.queue.test.ts b/src/discord/monitor/message-handler.queue.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it, vi } from "vitest";
+import { beforeEach, describe, expect, it, vi } from "vitest";
 import {
   createDiscordHandlerParams,
   createDiscordPreflightContext,
@@ -17,7 +17,7 @@ vi.mock("./message-handler.process.js", () => ({
   processDiscordMessage: processDiscordMessageMock,
 }));
 
-const { createDiscordMessageHandler } = await import("./message-handler.js");
+const { createDiscordMessageHandler, resetDiscordInboundMessageDedupe } = await import("./message-handler.js");
 
 function createDeferred<T = void>() {
   let resolve: (value: T | PromiseLike<T>) => void = () => {};
@@ -83,6 +83,10 @@ async function createLifecycleStopScenario(params: {
 }
 
 describe("createDiscordMessageHandler queue behavior", () => {
+  beforeEach(() => {
+    resetDiscordInboundMessageDedupe();
+  });
+
   it("resets busy counters when the handler is created", () => {
     preflightDiscordMessageMock.mockReset();
     processDiscordMessageMock.mockReset();
@@ -98,6 +102,30 @@ describe("createDiscordMessageHandler queue behavior", () => {
     );
   });
 
+  it("drops duplicate inbound Discord messages with the same message id", async () => {
+    preflightDiscordMessageMock.mockReset();
+    processDiscordMessageMock.mockReset();
+
+    preflightDiscordMessageMock.mockImplementation(
+      async (params: { data: { channel_id: string } }) =>
+        createPreflightContext(params.data.channel_id),
+    );
+    processDiscordMessageMock.mockResolvedValue(undefined);
+
+    const handler = createDiscordMessageHandler(createDiscordHandlerParams());
+
+    await expect(handler(createMessageData("dup-1") as never, {} as never)).resolves.toBeUndefined();
+    await vi.waitFor(() => {
+      expect(processDiscordMessageMock).toHaveBeenCalledTimes(1);
+    });
+
+    await expect(handler(createMessageData("dup-1") as never, {} as never)).resolves.toBeUndefined();
+    await Promise.resolve();
+
+    expect(preflightDiscordMessageMock).toHaveBeenCalledTimes(1);
+    expect(processDiscordMessageMock).toHaveBeenCalledTimes(1);
+  });
+
   it("returns immediately and tracks busy status while queued runs execute", async () => {
     preflightDiscordMessageMock.mockReset();
     processDiscordMessageMock.mockReset();
diff --git a/src/discord/monitor/message-handler.ts b/src/discord/monitor/message-handler.ts
@@ -5,6 +5,7 @@ import {
 } from "../../channels/inbound-debounce-policy.js";
 import { resolveOpenProviderRuntimeGroupPolicy } from "../../config/runtime-group-policy.js";
 import { danger } from "../../globals.js";
+import { createDedupeCache } from "../../infra/dedupe.js";
 import { buildDiscordInboundJob } from "./inbound-job.js";
 import { createDiscordInboundWorker } from "./inbound-worker.js";
 import type { DiscordMessageEvent, DiscordMessageHandler } from "./listeners.js";
@@ -30,6 +31,37 @@ export type DiscordMessageHandlerWithLifecycle = DiscordMessageHandler & {
   deactivate: () => void;
 };
 
+const discordInboundMessageDedupe = createDedupeCache({
+  ttlMs: 2 * 60_000,
+  maxSize: 10_000,
+});
+
+export function resetDiscordInboundMessageDedupe(): void {
+  discordInboundMessageDedupe.clear();
+}
+
+function buildDiscordInboundMessageDedupeKey(params: {
+  accountId?: string;
+  data: DiscordMessageEvent;
+}): string | null {
+  const messageId = params.data.message?.id?.trim() || params.data.id?.trim();
+  const authorId = params.data.message?.author?.id ?? params.data.author?.id;
+  const channelId = resolveDiscordMessageChannelId({
+    message: params.data.message,
+    eventChannelId: params.data.channel_id,
+  });
+  if (!messageId || !channelId) {
+    return null;
+  }
+  return JSON.stringify([
+    "discord-inbound",
+    params.accountId ?? "",
+    channelId,
+    authorId ?? "",
+    messageId,
+  ]);
+}
+
 export function createDiscordMessageHandler(
   params: DiscordMessageHandlerParams,
 ): DiscordMessageHandlerWithLifecycle {
@@ -174,6 +206,17 @@ export function createDiscordMessageHandler(
         return;
       }
 
+      const dedupeKey = buildDiscordInboundMessageDedupeKey({
+        accountId: params.accountId,
+        data,
+      });
+      if (dedupeKey && discordInboundMessageDedupe.peek(dedupeKey)) {
+        return;
+      }
+      if (dedupeKey) {
+        discordInboundMessageDedupe.check(dedupeKey);
+      }
+
       await debouncer.enqueue({ data, client, abortSignal: options?.abortSignal });
     } catch (err) {
       params.runtime.error?.(danger(`handler failed: ${String(err)}`));
