diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8652b32666a..56a73ce552f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -37,6 +37,7 @@ Docs: https://docs.openclaw.ai
 - Podman/launch: remove noisy container output from `scripts/run-openclaw-podman.sh` and align the Podman install guidance with the quieter startup flow. (#59368) Thanks @sallyom.
 - MS Teams/streaming: strip already-streamed text from fallback block delivery when replies exceed the 4000-character streaming limit so long responses stop duplicating content. (#59297) Thanks @bradgroux.
 - MS Teams/logging: format non-`Error` failures with the shared unknown-error helper so logs stop collapsing caught SDK or Axios objects into `[object Object]`. (#59321) Thanks @bradgroux.
+- Slack/thread context: filter thread starter and history by the effective conversation allowlist without dropping valid open-room, DM, or group DM context. (#58380)
 
 ## 2026.4.1-beta.1
 
diff --git a/extensions/slack/src/monitor/media.ts b/extensions/slack/src/monitor/media.ts
index c11683b198b..22e6ee2b9d9 100644
--- a/extensions/slack/src/monitor/media.ts
+++ b/extensions/slack/src/monitor/media.ts
@@ -337,6 +337,7 @@ export async function resolveSlackAttachmentContent(params: {
 export type SlackThreadStarter = {
   text: string;
   userId?: string;
+  botId?: string;
   ts?: string;
   files?: SlackFile[];
 };
@@ -391,7 +392,15 @@ export async function resolveSlackThreadStarter(params: {
       ts: params.threadTs,
       limit: 1,
       inclusive: true,
-    })) as { messages?: Array<{ text?: string; user?: string; ts?: string; files?: SlackFile[] }> };
+    })) as {
+      messages?: Array<{
+        text?: string;
+        user?: string;
+        bot_id?: string;
+        ts?: string;
+        files?: SlackFile[];
+      }>;
+    };
     const message = response?.messages?.[0];
     const text = (message?.text ?? "").trim();
     if (!message || !text) {
@@ -400,6 +409,7 @@ export async function resolveSlackThreadStarter(params: {
     const starter: SlackThreadStarter = {
       text,
       userId: message.user,
+      botId: message.bot_id,
       ts: message.ts,
       files: message.files,
     };
diff --git a/extensions/slack/src/monitor/message-handler/prepare-thread-context.test.ts b/extensions/slack/src/monitor/message-handler/prepare-thread-context.test.ts
new file mode 100644
index 00000000000..ca5b9b016a0
--- /dev/null
+++ b/extensions/slack/src/monitor/message-handler/prepare-thread-context.test.ts
@@ -0,0 +1,146 @@
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+import type { App } from "@slack/bolt";
+import { resolveEnvelopeFormatOptions } from "openclaw/plugin-sdk/channel-inbound";
+import type { OpenClawConfig } from "openclaw/plugin-sdk/config-runtime";
+import { afterAll, beforeAll, describe, expect, it, vi } from "vitest";
+import type { SlackMessageEvent } from "../../types.js";
+import { resolveSlackThreadContextData } from "./prepare-thread-context.js";
+import { createInboundSlackTestContext, createSlackTestAccount } from "./prepare.test-helpers.js";
+
+describe("resolveSlackThreadContextData", () => {
+  let fixtureRoot = "";
+  let caseId = 0;
+
+  function makeTmpStorePath() {
+    if (!fixtureRoot) {
+      throw new Error("fixtureRoot missing");
+    }
+    const dir = path.join(fixtureRoot, `case-${caseId++}`);
+    fs.mkdirSync(dir);
+    return { dir, storePath: path.join(dir, "sessions.json") };
+  }
+
+  beforeAll(() => {
+    fixtureRoot = fs.mkdtempSync(path.join(os.tmpdir(), "openclaw-slack-thread-context-"));
+  });
+
+  afterAll(() => {
+    if (fixtureRoot) {
+      fs.rmSync(fixtureRoot, { recursive: true, force: true });
+      fixtureRoot = "";
+    }
+  });
+
+  function createThreadContext(params: { replies: unknown }) {
+    return createInboundSlackTestContext({
+      cfg: {
+        channels: { slack: { enabled: true, replyToMode: "all", groupPolicy: "open" } },
+      } as OpenClawConfig,
+      appClient: { conversations: { replies: params.replies } } as App["client"],
+      defaultRequireMention: false,
+      replyToMode: "all",
+    });
+  }
+
+  function createThreadMessage(overrides: Partial<SlackMessageEvent> = {}): SlackMessageEvent {
+    return {
+      channel: "C123",
+      channel_type: "channel",
+      user: "U1",
+      text: "current message",
+      ts: "101.000",
+      thread_ts: "100.000",
+      ...overrides,
+    } as SlackMessageEvent;
+  }
+
+  it("omits non-allowlisted starter text and thread history messages", async () => {
+    const { storePath } = makeTmpStorePath();
+    const replies = vi.fn().mockResolvedValue({
+      messages: [
+        { text: "starter secret", user: "U2", ts: "100.000" },
+        { text: "assistant reply", bot_id: "B1", ts: "100.500" },
+        { text: "blocked follow-up", user: "U2", ts: "100.700" },
+        { text: "allowed follow-up", user: "U1", ts: "100.800" },
+        { text: "current message", user: "U1", ts: "101.000" },
+      ],
+      response_metadata: { next_cursor: "" },
+    });
+    const ctx = createThreadContext({ replies });
+    ctx.resolveUserName = async (id: string) => ({
+      name: id === "U1" ? "Alice" : "Mallory",
+    });
+
+    const result = await resolveSlackThreadContextData({
+      ctx,
+      account: createSlackTestAccount({ thread: { initialHistoryLimit: 20 } }),
+      message: createThreadMessage(),
+      isThreadReply: true,
+      threadTs: "100.000",
+      threadStarter: {
+        text: "starter secret",
+        userId: "U2",
+        ts: "100.000",
+      },
+      roomLabel: "#general",
+      storePath,
+      sessionKey: "thread-session",
+      allowFromLower: ["u1"],
+      allowNameMatching: false,
+      envelopeOptions: resolveEnvelopeFormatOptions({} as OpenClawConfig),
+      effectiveDirectMedia: null,
+    });
+
+    expect(result.threadStarterBody).toBeUndefined();
+    expect(result.threadLabel).toBe("Slack thread #general");
+    expect(result.threadHistoryBody).toContain("assistant reply");
+    expect(result.threadHistoryBody).toContain("allowed follow-up");
+    expect(result.threadHistoryBody).not.toContain("starter secret");
+    expect(result.threadHistoryBody).not.toContain("blocked follow-up");
+    expect(result.threadHistoryBody).not.toContain("current message");
+    expect(replies).toHaveBeenCalledTimes(1);
+  });
+
+  it("keeps starter text and history when allowNameMatching authorizes the sender", async () => {
+    const { storePath } = makeTmpStorePath();
+    const replies = vi.fn().mockResolvedValue({
+      messages: [
+        { text: "starter from Alice", user: "U1", ts: "100.000" },
+        { text: "blocked follow-up", user: "U2", ts: "100.700" },
+        { text: "current message", user: "U1", ts: "101.000" },
+      ],
+      response_metadata: { next_cursor: "" },
+    });
+    const ctx = createThreadContext({ replies });
+    ctx.resolveUserName = async (id: string) => ({
+      name: id === "U1" ? "Alice" : "Mallory",
+    });
+
+    const result = await resolveSlackThreadContextData({
+      ctx,
+      account: createSlackTestAccount({ thread: { initialHistoryLimit: 20 } }),
+      message: createThreadMessage(),
+      isThreadReply: true,
+      threadTs: "100.000",
+      threadStarter: {
+        text: "starter from Alice",
+        userId: "U1",
+        ts: "100.000",
+      },
+      roomLabel: "#general",
+      storePath,
+      sessionKey: "thread-session",
+      allowFromLower: ["alice"],
+      allowNameMatching: true,
+      envelopeOptions: resolveEnvelopeFormatOptions({} as OpenClawConfig),
+      effectiveDirectMedia: null,
+    });
+
+    expect(result.threadStarterBody).toBe("starter from Alice");
+    expect(result.threadLabel).toContain("starter from Alice");
+    expect(result.threadHistoryBody).toContain("starter from Alice");
+    expect(result.threadHistoryBody).not.toContain("blocked follow-up");
+  });
+});
diff --git a/extensions/slack/src/monitor/message-handler/prepare-thread-context.ts b/extensions/slack/src/monitor/message-handler/prepare-thread-context.ts
index e1cfc33088a..b383d223bea 100644
--- a/extensions/slack/src/monitor/message-handler/prepare-thread-context.ts
+++ b/extensions/slack/src/monitor/message-handler/prepare-thread-context.ts
@@ -3,6 +3,7 @@ import { readSessionUpdatedAt } from "openclaw/plugin-sdk/config-runtime";
 import { logVerbose } from "openclaw/plugin-sdk/runtime-env";
 import type { ResolvedSlackAccount } from "../../accounts.js";
 import type { SlackMessageEvent } from "../../types.js";
+import { resolveSlackAllowListMatch } from "../allow-list.js";
 import type { SlackMonitorContext } from "../context.js";
 import {
   resolveSlackMedia,
@@ -19,6 +20,27 @@ export type SlackThreadContextData = {
   threadStarterMedia: SlackMediaResult[] | null;
 };
 
+function isSlackThreadContextSenderAllowed(params: {
+  allowFromLower: string[];
+  allowNameMatching: boolean;
+  userId?: string;
+  userName?: string;
+  botId?: string;
+}): boolean {
+  if (params.allowFromLower.length === 0 || params.botId) {
+    return true;
+  }
+  if (!params.userId) {
+    return false;
+  }
+  return resolveSlackAllowListMatch({
+    allowList: params.allowFromLower,
+    id: params.userId,
+    name: params.userName,
+    allowNameMatching: params.allowNameMatching,
+  }).allowed;
+}
+
 export async function resolveSlackThreadContextData(params: {
   ctx: SlackMonitorContext;
   account: ResolvedSlackAccount;
@@ -29,6 +51,8 @@ export async function resolveSlackThreadContextData(params: {
   roomLabel: string;
   storePath: string;
   sessionKey: string;
+  allowFromLower: string[];
+  allowNameMatching: boolean;
   envelopeOptions: ReturnType<
     typeof import("openclaw/plugin-sdk/channel-inbound").resolveEnvelopeFormatOptions
   >;
@@ -51,7 +75,21 @@ export async function resolveSlackThreadContextData(params: {
   }
 
   const starter = params.threadStarter;
-  if (starter?.text) {
+  const starterSenderName =
+    params.allowNameMatching && starter?.userId
+      ? (await params.ctx.resolveUserName(starter.userId))?.name
+      : undefined;
+  const starterAllowed =
+    !starter ||
+    isSlackThreadContextSenderAllowed({
+      allowFromLower: params.allowFromLower,
+      allowNameMatching: params.allowNameMatching,
+      userId: starter.userId,
+      userName: starterSenderName,
+      botId: starter.botId,
+    });
+
+  if (starter?.text && starterAllowed) {
     threadStarterBody = starter.text;
     const snippet = starter.text.replace(/\s+/g, " ").slice(0, 80);
     threadLabel = `Slack thread ${params.roomLabel}${snippet ? `: ${snippet}` : ""}`;
@@ -69,6 +107,9 @@ export async function resolveSlackThreadContextData(params: {
   } else {
     threadLabel = `Slack thread ${params.roomLabel}`;
   }
+  if (starter?.text && !starterAllowed) {
+    logVerbose("slack: omitted non-allowlisted thread starter from context");
+  }
 
   const threadInitialHistoryLimit = params.account.config?.thread?.initialHistoryLimit ?? 20;
   threadSessionPreviousTimestamp = readSessionUpdatedAt({
@@ -101,8 +142,25 @@ export async function resolveSlackThreadContextData(params: {
         }),
       );
 
+      const allowedThreadHistory = threadHistory.filter((historyMsg) => {
+        const msgUser = historyMsg.userId ? userMap.get(historyMsg.userId) : null;
+        return isSlackThreadContextSenderAllowed({
+          allowFromLower: params.allowFromLower,
+          allowNameMatching: params.allowNameMatching,
+          userId: historyMsg.userId,
+          userName: msgUser?.name,
+          botId: historyMsg.botId,
+        });
+      });
+      const omittedHistoryCount = threadHistory.length - allowedThreadHistory.length;
+      if (omittedHistoryCount > 0) {
+        logVerbose(
+          `slack: omitted ${omittedHistoryCount} non-allowlisted thread message(s) from context`,
+        );
+      }
+
       const historyParts: string[] = [];
-      for (const historyMsg of threadHistory) {
+      for (const historyMsg of allowedThreadHistory) {
         const msgUser = historyMsg.userId ? userMap.get(historyMsg.userId) : null;
         const msgSenderName =
           msgUser?.name ?? (historyMsg.botId ? `Bot (${historyMsg.botId})` : "Unknown");
@@ -120,10 +178,12 @@ export async function resolveSlackThreadContextData(params: {
           }),
         );
       }
-      threadHistoryBody = historyParts.join("\n\n");
-      logVerbose(
-        `slack: populated thread history with ${threadHistory.length} messages for new session`,
-      );
+      if (historyParts.length > 0) {
+        threadHistoryBody = historyParts.join("\n\n");
+        logVerbose(
+          `slack: populated thread history with ${allowedThreadHistory.length} messages for new session`,
+        );
+      }
     }
   }
 
diff --git a/extensions/slack/src/monitor/message-handler/prepare.test-helpers.ts b/extensions/slack/src/monitor/message-handler/prepare.test-helpers.ts
index f6d3ab21ce9..07f97b3a137 100644
--- a/extensions/slack/src/monitor/message-handler/prepare.test-helpers.ts
+++ b/extensions/slack/src/monitor/message-handler/prepare.test-helpers.ts
@@ -2,6 +2,7 @@ import type { App } from "@slack/bolt";
 import type { OpenClawConfig } from "openclaw/plugin-sdk/config-runtime";
 import type { RuntimeEnv } from "openclaw/plugin-sdk/runtime-env";
 import type { ResolvedSlackAccount } from "../../accounts.js";
+import type { SlackChannelConfigEntries } from "../channel-config.js";
 import { createSlackMonitorContext } from "../context.js";
 
 export function createInboundSlackTestContext(params: {
@@ -9,7 +10,7 @@ export function createInboundSlackTestContext(params: {
   appClient?: App["client"];
   defaultRequireMention?: boolean;
   replyToMode?: "off" | "all" | "first";
-  channelsConfig?: Record<string, { systemPrompt: string }>;
+  channelsConfig?: SlackChannelConfigEntries;
 }) {
   return createSlackMonitorContext({
     cfg: params.cfg,
diff --git a/extensions/slack/src/monitor/message-handler/prepare.thread-context-allowlist.test.ts b/extensions/slack/src/monitor/message-handler/prepare.thread-context-allowlist.test.ts
new file mode 100644
index 00000000000..623fab36b57
--- /dev/null
+++ b/extensions/slack/src/monitor/message-handler/prepare.thread-context-allowlist.test.ts
@@ -0,0 +1,288 @@
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+import type { App } from "@slack/bolt";
+import type { OpenClawConfig } from "openclaw/plugin-sdk/config-runtime";
+import { afterAll, beforeAll, describe, expect, it, vi } from "vitest";
+import type { SlackMessageEvent } from "../../types.js";
+
+type PrepareSlackMessage = typeof import("./prepare.js").prepareSlackMessage;
+type CreateInboundSlackTestContext =
+  typeof import("./prepare.test-helpers.js").createInboundSlackTestContext;
+type CreateSlackTestAccount = typeof import("./prepare.test-helpers.js").createSlackTestAccount;
+
+let prepareSlackMessage: PrepareSlackMessage;
+let createInboundSlackTestContext: CreateInboundSlackTestContext;
+let createSlackTestAccount: CreateSlackTestAccount;
+let fixtureRoot = "";
+let caseId = 0;
+
+async function loadSlackPrepareModules() {
+  const [{ prepareSlackMessage: loadedPrepareSlackMessage }, helpers] = await Promise.all([
+    import("./prepare.js"),
+    import("./prepare.test-helpers.js"),
+  ]);
+  prepareSlackMessage = loadedPrepareSlackMessage;
+  createInboundSlackTestContext = helpers.createInboundSlackTestContext;
+  createSlackTestAccount = helpers.createSlackTestAccount;
+}
+
+function makeTmpStorePath() {
+  if (!fixtureRoot) {
+    throw new Error("fixtureRoot missing");
+  }
+  const dir = path.join(fixtureRoot, `case-${caseId++}`);
+  fs.mkdirSync(dir);
+  return path.join(dir, "sessions.json");
+}
+
+describe("prepareSlackMessage thread context allowlists", () => {
+  beforeAll(async () => {
+    await loadSlackPrepareModules();
+    fixtureRoot = fs.mkdtempSync(path.join(os.tmpdir(), "openclaw-slack-room-thread-context-"));
+  });
+
+  afterAll(() => {
+    if (fixtureRoot) {
+      fs.rmSync(fixtureRoot, { recursive: true, force: true });
+      fixtureRoot = "";
+    }
+  });
+
+  it("uses room users allowlist for thread context filtering", async () => {
+    const replies = vi
+      .fn()
+      .mockResolvedValueOnce({
+        messages: [{ text: "starter from room user", user: "U1", ts: "100.000" }],
+      })
+      .mockResolvedValueOnce({
+        messages: [
+          { text: "starter from room user", user: "U1", ts: "100.000" },
+          { text: "assistant reply", bot_id: "B1", ts: "100.500" },
+          { text: "allowed follow-up", user: "U1", ts: "100.800" },
+          { text: "current message", user: "U1", ts: "101.000" },
+        ],
+        response_metadata: { next_cursor: "" },
+      });
+    const storePath = makeTmpStorePath();
+    const ctx = createInboundSlackTestContext({
+      cfg: {
+        session: { store: storePath },
+        channels: { slack: { enabled: true, replyToMode: "all", groupPolicy: "open" } },
+      } as OpenClawConfig,
+      appClient: { conversations: { replies } } as unknown as App["client"],
+      defaultRequireMention: false,
+      replyToMode: "all",
+      channelsConfig: {
+        C123: {
+          users: ["U1"],
+          requireMention: false,
+        },
+      },
+    });
+    ctx.allowFrom = ["u-owner"];
+    ctx.resolveUserName = async (id: string) => ({
+      name: id === "U1" ? "Alice" : "Owner",
+    });
+    ctx.resolveChannelName = async () => ({ name: "general", type: "channel" });
+
+    const prepared = await prepareSlackMessage({
+      ctx,
+      account: createSlackTestAccount({
+        replyToMode: "all",
+        thread: { initialHistoryLimit: 20 },
+      }),
+      message: {
+        channel: "C123",
+        channel_type: "channel",
+        user: "U1",
+        text: "current message",
+        ts: "101.000",
+        thread_ts: "100.000",
+      } as SlackMessageEvent,
+      opts: { source: "message" },
+    });
+
+    expect(prepared).toBeTruthy();
+    expect(prepared!.ctxPayload.ThreadStarterBody).toBe("starter from room user");
+    expect(prepared!.ctxPayload.ThreadHistoryBody).toContain("starter from room user");
+    expect(prepared!.ctxPayload.ThreadHistoryBody).toContain("assistant reply");
+    expect(prepared!.ctxPayload.ThreadHistoryBody).toContain("allowed follow-up");
+    expect(prepared!.ctxPayload.ThreadHistoryBody).not.toContain("current message");
+    expect(replies).toHaveBeenCalledTimes(2);
+  });
+
+  it("does not apply the owner allowlist to open-room thread context", async () => {
+    const replies = vi
+      .fn()
+      .mockResolvedValueOnce({
+        messages: [{ text: "starter from open room", user: "U2", ts: "200.000" }],
+      })
+      .mockResolvedValueOnce({
+        messages: [
+          { text: "starter from open room", user: "U2", ts: "200.000" },
+          { text: "assistant reply", bot_id: "B1", ts: "200.500" },
+          { text: "open-room follow-up", user: "U2", ts: "200.800" },
+          { text: "current message", user: "U2", ts: "201.000" },
+        ],
+        response_metadata: { next_cursor: "" },
+      });
+    const storePath = makeTmpStorePath();
+    const ctx = createInboundSlackTestContext({
+      cfg: {
+        session: { store: storePath },
+        channels: { slack: { enabled: true, replyToMode: "all", groupPolicy: "open" } },
+      } as OpenClawConfig,
+      appClient: { conversations: { replies } } as unknown as App["client"],
+      defaultRequireMention: false,
+      replyToMode: "all",
+      channelsConfig: {
+        C124: {
+          requireMention: false,
+        },
+      },
+    });
+    ctx.allowFrom = ["u-owner"];
+    ctx.resolveUserName = async (id: string) => ({
+      name: id === "U2" ? "Bob" : "Owner",
+    });
+    ctx.resolveChannelName = async () => ({ name: "general", type: "channel" });
+
+    const prepared = await prepareSlackMessage({
+      ctx,
+      account: createSlackTestAccount({
+        replyToMode: "all",
+        thread: { initialHistoryLimit: 20 },
+      }),
+      message: {
+        channel: "C124",
+        channel_type: "channel",
+        user: "U2",
+        text: "current message",
+        ts: "201.000",
+        thread_ts: "200.000",
+      } as SlackMessageEvent,
+      opts: { source: "message" },
+    });
+
+    expect(prepared).toBeTruthy();
+    expect(prepared!.ctxPayload.ThreadStarterBody).toBe("starter from open room");
+    expect(prepared!.ctxPayload.ThreadHistoryBody).toContain("starter from open room");
+    expect(prepared!.ctxPayload.ThreadHistoryBody).toContain("assistant reply");
+    expect(prepared!.ctxPayload.ThreadHistoryBody).toContain("open-room follow-up");
+    expect(prepared!.ctxPayload.ThreadHistoryBody).not.toContain("current message");
+    expect(replies).toHaveBeenCalledTimes(2);
+  });
+
+  it("does not apply the owner allowlist to open DMs when dmPolicy is open", async () => {
+    const replies = vi
+      .fn()
+      .mockResolvedValueOnce({
+        messages: [{ text: "starter from open dm", user: "U3", ts: "300.000" }],
+      })
+      .mockResolvedValueOnce({
+        messages: [
+          { text: "starter from open dm", user: "U3", ts: "300.000" },
+          { text: "assistant reply", bot_id: "B1", ts: "300.500" },
+          { text: "dm follow-up", user: "U3", ts: "300.800" },
+          { text: "current message", user: "U3", ts: "301.000" },
+        ],
+        response_metadata: { next_cursor: "" },
+      });
+    const storePath = makeTmpStorePath();
+    const ctx = createInboundSlackTestContext({
+      cfg: {
+        session: { store: storePath },
+        channels: { slack: { enabled: true, replyToMode: "all", groupPolicy: "open" } },
+      } as OpenClawConfig,
+      appClient: { conversations: { replies } } as unknown as App["client"],
+      defaultRequireMention: false,
+      replyToMode: "all",
+    });
+    ctx.allowFrom = ["u-owner"];
+    ctx.resolveUserName = async (id: string) => ({
+      name: id === "U3" ? "Dana" : "Owner",
+    });
+
+    const prepared = await prepareSlackMessage({
+      ctx,
+      account: createSlackTestAccount({
+        replyToMode: "all",
+        thread: { initialHistoryLimit: 20 },
+      }),
+      message: {
+        channel: "D300",
+        channel_type: "im",
+        user: "U3",
+        text: "current message",
+        ts: "301.000",
+        thread_ts: "300.000",
+      } as SlackMessageEvent,
+      opts: { source: "message" },
+    });
+
+    expect(prepared).toBeTruthy();
+    expect(prepared!.ctxPayload.ThreadStarterBody).toBe("starter from open dm");
+    expect(prepared!.ctxPayload.ThreadHistoryBody).toContain("starter from open dm");
+    expect(prepared!.ctxPayload.ThreadHistoryBody).toContain("assistant reply");
+    expect(prepared!.ctxPayload.ThreadHistoryBody).toContain("dm follow-up");
+    expect(prepared!.ctxPayload.ThreadHistoryBody).not.toContain("current message");
+    expect(replies).toHaveBeenCalledTimes(2);
+  });
+
+  it("does not apply the owner allowlist to MPIM thread context", async () => {
+    const replies = vi
+      .fn()
+      .mockResolvedValueOnce({
+        messages: [{ text: "starter from mpim", user: "U4", ts: "400.000" }],
+      })
+      .mockResolvedValueOnce({
+        messages: [
+          { text: "starter from mpim", user: "U4", ts: "400.000" },
+          { text: "assistant reply", bot_id: "B1", ts: "400.500" },
+          { text: "mpim follow-up", user: "U4", ts: "400.800" },
+          { text: "current message", user: "U4", ts: "401.000" },
+        ],
+        response_metadata: { next_cursor: "" },
+      });
+    const storePath = makeTmpStorePath();
+    const ctx = createInboundSlackTestContext({
+      cfg: {
+        session: { store: storePath },
+        channels: { slack: { enabled: true, replyToMode: "all", groupPolicy: "open" } },
+      } as OpenClawConfig,
+      appClient: { conversations: { replies } } as unknown as App["client"],
+      defaultRequireMention: false,
+      replyToMode: "all",
+    });
+    ctx.allowFrom = ["u-owner"];
+    ctx.resolveUserName = async (id: string) => ({
+      name: id === "U4" ? "Evan" : "Owner",
+    });
+
+    const prepared = await prepareSlackMessage({
+      ctx,
+      account: createSlackTestAccount({
+        replyToMode: "all",
+        thread: { initialHistoryLimit: 20 },
+      }),
+      message: {
+        channel: "G400",
+        channel_type: "mpim",
+        user: "U4",
+        text: "current message",
+        ts: "401.000",
+        thread_ts: "400.000",
+      } as SlackMessageEvent,
+      opts: { source: "message" },
+    });
+
+    expect(prepared).toBeTruthy();
+    expect(prepared!.ctxPayload.ThreadStarterBody).toBe("starter from mpim");
+    expect(prepared!.ctxPayload.ThreadHistoryBody).toContain("starter from mpim");
+    expect(prepared!.ctxPayload.ThreadHistoryBody).toContain("assistant reply");
+    expect(prepared!.ctxPayload.ThreadHistoryBody).toContain("mpim follow-up");
+    expect(prepared!.ctxPayload.ThreadHistoryBody).not.toContain("current message");
+    expect(replies).toHaveBeenCalledTimes(2);
+  });
+});
diff --git a/extensions/slack/src/monitor/message-handler/prepare.ts b/extensions/slack/src/monitor/message-handler/prepare.ts
index 3e7db4aa392..85ef60094e4 100644
--- a/extensions/slack/src/monitor/message-handler/prepare.ts
+++ b/extensions/slack/src/monitor/message-handler/prepare.ts
@@ -37,6 +37,7 @@ import { hasSlackThreadParticipation } from "../../sent-thread-cache.js";
 import { resolveSlackThreadContext } from "../../threading.js";
 import type { SlackMessageEvent } from "../../types.js";
 import {
+  normalizeAllowListLower,
   normalizeSlackAllowOwnerEntry,
   resolveSlackAllowListMatch,
   resolveSlackUserAllowed,
@@ -436,6 +437,15 @@ export async function prepareSlackMessage(params: {
   }).allowed;
   const channelUsersAllowlistConfigured =
     isRoom && Array.isArray(channelConfig?.users) && channelConfig.users.length > 0;
+  const threadContextAllowFromLower = isRoom
+    ? channelUsersAllowlistConfigured
+      ? normalizeAllowListLower(channelConfig?.users)
+      : []
+    : isDirectMessage
+      ? ctx.dmPolicy === "open"
+        ? []
+        : allowFromLower
+      : [];
   const channelCommandAuthorized =
     isRoom && channelUsersAllowlistConfigured
       ? resolveSlackUserAllowed({
@@ -669,6 +679,8 @@ export async function prepareSlackMessage(params: {
     roomLabel,
     storePath,
     sessionKey,
+    allowFromLower: threadContextAllowFromLower,
+    allowNameMatching: ctx.allowNameMatching,
     envelopeOptions,
     effectiveDirectMedia,
   });