diff --git a/extensions/signal/src/monitor/event-handler.quote.test.ts b/extensions/signal/src/monitor/event-handler.quote.test.ts
index ad865251a51..92fb4df489b 100644
--- a/extensions/signal/src/monitor/event-handler.quote.test.ts
+++ b/extensions/signal/src/monitor/event-handler.quote.test.ts
@@ -345,6 +345,49 @@ describe("signal quote reply handling", () => {
     expect(String(ctx?.Body ?? "")).toContain("[Quoting +15550002222 id:1700000000001]");
   });
 
+  it("does not poison the quote-author cache from attacker-controlled quote metadata", async () => {
+    const handler = createQuoteHandler();
+
+    await handler(
+      createSignalReceiveEvent({
+        sourceNumber: "+15550002222",
+        sourceName: "Bob",
+        timestamp: 1700000000001,
+        dataMessage: {
+          message: "Forwarding this",
+          groupInfo: { groupId: "g1", groupName: "Test Group" },
+          quote: {
+            id: 1700000000000,
+            authorNumber: "+15550009999",
+            text: "Mallory wrote this",
+          },
+        },
+      }),
+    );
+
+    capturedCtx = undefined;
+
+    await handler(
+      createSignalReceiveEvent({
+        sourceNumber: "+15550003333",
+        sourceName: "Alice",
+        timestamp: 1700000000002,
+        dataMessage: {
+          message: "Replying to Bob",
+          groupInfo: { groupId: "g1", groupName: "Test Group" },
+          quote: {
+            id: 1700000000001,
+            text: "Forwarding this",
+          },
+        },
+      }),
+    );
+
+    const ctx = getCapturedCtx();
+    expect(ctx?.ReplyToSender).toBe("+15550002222");
+    expect(String(ctx?.Body ?? "")).toContain("[Quoting +15550002222 id:1700000000001]");
+  });
+
   it("resolves cached uuid senders with a uuid: prefix", async () => {
     const handler = createQuoteHandler();
     const senderUuid = "123e4567-e89b-12d3-a456-426614174000";
diff --git a/src/auto-reply/reply/reply-payloads.test.ts b/src/auto-reply/reply/reply-payloads.test.ts
index 8664eec5c72..3156b0096ee 100644
--- a/src/auto-reply/reply/reply-payloads.test.ts
+++ b/src/auto-reply/reply/reply-payloads.test.ts
@@ -2,10 +2,33 @@ import { describe, expect, it } from "vitest";
 import { setActivePluginRegistry } from "../../plugins/runtime.js";
 import { createTestRegistry } from "../../test-utils/channel-plugins.js";
 import {
+  applyReplyThreading,
   filterMessagingToolMediaDuplicates,
   shouldSuppressMessagingToolReplies,
 } from "./reply-payloads.js";
 
+describe("applyReplyThreading", () => {
+  it("treats whitespace-only replyToId as unset so implicit replies still apply", () => {
+    const result = applyReplyThreading({
+      payloads: [{ text: "hello", replyToId: "  \n\t  " }],
+      replyToMode: "all",
+      currentMessageId: "123",
+    });
+
+    expect(result).toEqual([{ text: "hello", replyToId: "123" }]);
+  });
+
+  it("preserves explicit null replyToId as do-not-reply", () => {
+    const result = applyReplyThreading({
+      payloads: [{ text: "hello", replyToId: null }],
+      replyToMode: "all",
+      currentMessageId: "123",
+    });
+
+    expect(result).toEqual([{ text: "hello", replyToId: null }]);
+  });
+});
+
 describe("filterMessagingToolMediaDuplicates", () => {
   it("strips mediaUrl when it matches sentMediaUrls", () => {
     const result = filterMessagingToolMediaDuplicates({
diff --git a/src/infra/outbound/deliver.test.ts b/src/infra/outbound/deliver.test.ts
index 01d8367dd78..cec3e001fd4 100644
--- a/src/infra/outbound/deliver.test.ts
+++ b/src/infra/outbound/deliver.test.ts
@@ -3,6 +3,7 @@ import { afterEach, beforeAll, beforeEach, describe, expect, it, vi } from "vite
 import { markdownToSignalTextChunks } from "../../../extensions/signal/src/format.js";
 import {
   signalOutbound,
+  slackOutbound,
   telegramOutbound,
   whatsappOutbound,
 } from "../../../test/channel-outbounds.js";
@@ -1027,6 +1028,45 @@ describe("deliverOutboundPayloads", () => {
     );
   });
 
+  it("keeps inherited Slack thread context across all payloads", async () => {
+    const sendSlack = vi
+      .fn()
+      .mockResolvedValueOnce({ messageId: "sl1", channelId: "C123" })
+      .mockResolvedValueOnce({ messageId: "sl2", channelId: "C123" });
+    setActivePluginRegistry(
+      createTestRegistry([
+        {
+          pluginId: "slack",
+          plugin: createOutboundTestPlugin({ id: "slack", outbound: slackOutbound }),
+          source: "test",
+        },
+      ]),
+    );
+
+    await deliverOutboundPayloads({
+      cfg: { channels: { slack: {} } },
+      channel: "slack",
+      to: "C123",
+      payloads: [{ text: "first" }, { text: "second" }],
+      replyToId: "thread-123",
+      deps: { sendSlack },
+    });
+
+    expect(sendSlack).toHaveBeenCalledTimes(2);
+    expect(sendSlack).toHaveBeenNthCalledWith(
+      1,
+      "C123",
+      "first",
+      expect.objectContaining({ threadTs: "thread-123" }),
+    );
+    expect(sendSlack).toHaveBeenNthCalledWith(
+      2,
+      "C123",
+      "second",
+      expect.objectContaining({ threadTs: "thread-123" }),
+    );
+  });
+
   it("passes normalized payload to onError", async () => {
     const sendWhatsApp = vi.fn().mockRejectedValue(new Error("boom"));
     const onError = vi.fn();