fix: treat reply-to-bot as implicit mention across channels

src/slack/monitor.tool-result.sends-tool-summaries-responseprefix.test.ts

@@ -498,6 +498,49 @@ describe("monitorSlackProvider tool results", () => {
     expect(replyMock.mock.calls[0][0].WasMentioned).toBe(true);
   });
 
+  it("treats replies to bot threads as implicit mentions", async () => {
+    config = {
+      channels: {
+        slack: {
+          dm: { enabled: true, policy: "open", allowFrom: ["*"] },
+          channels: { C1: { allow: true, requireMention: true } },
+        },
+      },
+    };
+    replyMock.mockResolvedValue({ text: "hi" });
+
+    const controller = new AbortController();
+    const run = monitorSlackProvider({
+      botToken: "bot-token",
+      appToken: "app-token",
+      abortSignal: controller.signal,
+    });
+
+    await waitForEvent("message");
+    const handler = getSlackHandlers()?.get("message");
+    if (!handler) throw new Error("Slack message handler not registered");
+
+    await handler({
+      event: {
+        type: "message",
+        user: "U1",
+        text: "following up",
+        ts: "124",
+        thread_ts: "123",
+        parent_user_id: "bot-user",
+        channel: "C1",
+        channel_type: "channel",
+      },
+    });
+
+    await flush();
+    controller.abort();
+    await run;
+
+    expect(replyMock).toHaveBeenCalledTimes(1);
+    expect(replyMock.mock.calls[0][0].WasMentioned).toBe(true);
+  });
+
   it("accepts channel messages without mention when channels.slack.requireMention is false", async () => {
     config = {
       channels: {

src/slack/monitor/message-handler/prepare.ts

@@ -10,6 +10,7 @@ import { buildPairingReply } from "../../../pairing/pairing-messages.js";
 import { upsertChannelPairingRequest } from "../../../pairing/pairing-store.js";
 import { resolveAgentRoute } from "../../../routing/resolve-route.js";
 import { resolveThreadSessionKeys } from "../../../routing/session-key.js";
+import { resolveMentionGating } from "../../../channels/mention-gating.js";
 
 import type { ResolvedSlackAccount } from "../../accounts.js";
 import { reactSlackMessage } from "../../actions.js";
@@ -172,6 +173,12 @@ export async function prepareSlackMessage(params: {
     (!isDirectMessage &&
       (Boolean(ctx.botUserId && message.text?.includes(`<@${ctx.botUserId}>`)) ||
         matchesMentionPatterns(message.text ?? "", mentionRegexes)));
+  const implicitMention = Boolean(
+    !isDirectMessage &&
+      ctx.botUserId &&
+      message.thread_ts &&
+      message.parent_user_id === ctx.botUserId,
+  );
 
   const sender = message.user ? await ctx.resolveUserName(message.user) : null;
   const senderName =
@@ -215,9 +222,16 @@ export async function prepareSlackMessage(params: {
     commandAuthorized &&
     hasControlCommand(message.text ?? "", cfg);
 
-  const effectiveWasMentioned = wasMentioned || shouldBypassMention;
   const canDetectMention = Boolean(ctx.botUserId) || mentionRegexes.length > 0;
-  if (isRoom && shouldRequireMention && canDetectMention && !wasMentioned && !shouldBypassMention) {
+  const mentionGate = resolveMentionGating({
+    requireMention: Boolean(shouldRequireMention),
+    canDetectMention,
+    wasMentioned,
+    implicitMention,
+    shouldBypassMention,
+  });
+  const effectiveWasMentioned = mentionGate.effectiveWasMentioned;
+  if (isRoom && shouldRequireMention && mentionGate.shouldSkip) {
     ctx.logger.info({ channel: message.channel, reason: "no-mention" }, "skipping room message");
     return null;
   }
@@ -242,7 +256,7 @@ export async function prepareSlackMessage(params: {
       if (!isRoom) return false;
       if (!shouldRequireMention) return false;
       if (!canDetectMention) return false;
-      return wasMentioned || shouldBypassMention;
+      return effectiveWasMentioned;
     }
     return false;
   };