feat(mattermost): add replyToMode support (off | first | all) (#29587)

Merged via squash.

Prepared head SHA: 4a67791f53b1109959082738429471b7a5bc93b8
Co-authored-by: teconomix <6959299+teconomix@users.noreply.github.com>
Co-authored-by: mukhtharcm <56378562+mukhtharcm@users.noreply.github.com>
Reviewed-by: @mukhtharcm

CHANGELOG.md

@@ -57,7 +57,9 @@ Docs: https://docs.openclaw.ai
 - Gateway/node pending work: add narrow in-memory pending-work queue primitives (`node.pending.enqueue` / `node.pending.drain`) and wake-helper reuse as a foundation for dormant-node work delivery. (#41409) Thanks @mbelinky.
 - Git/runtime state: ignore the gateway-generated `.dev-state` file so local runtime state does not show up as untracked repo noise. (#41848) Thanks @smysle.
 - Exec/child commands: mark child command environments with `OPENCLAW_CLI` so subprocesses can detect when they were launched from the OpenClaw CLI. (#41411) Thanks @vincentkoc.
+  <<<<<<< HEAD
 - LLM Task/Lobster: add an optional `thinking` override so workflow calls can explicitly set embedded reasoning level with shared validation for invalid values and unsupported `xhigh` modes. (#15606) Thanks @xadenryan and @ImLukeF.
+- Mattermost/reply threading: add `channels.mattermost.replyToMode` for channel and group messages so top-level posts can start thread-scoped sessions without the manual reply-then-thread workaround. (#29587) Thanks @teconomix.
 
 ### Breaking
 

docs/channels/mattermost.md

@@ -129,6 +129,35 @@ Notes:
 - `onchar` still responds to explicit @mentions.
 - `channels.mattermost.requireMention` is honored for legacy configs but `chatmode` is preferred.
 
+## Threading and sessions
+
+Use `channels.mattermost.replyToMode` to control whether channel and group replies stay in the
+main channel or start a thread under the triggering post.
+
+- `off` (default): only reply in a thread when the inbound post is already in one.
+- `first`: for top-level channel/group posts, start a thread under that post and route the
+  conversation to a thread-scoped session.
+- `all`: same behavior as `first` for Mattermost today.
+- Direct messages ignore this setting and stay non-threaded.
+
+Config example:
+
+```json5
+{
+  channels: {
+    mattermost: {
+      replyToMode: "all",
+    },
+  },
+}
+```
+
+Notes:
+
+- Thread-scoped sessions use the triggering post id as the thread root.
+- `first` and `all` are currently equivalent because once Mattermost has a thread root,
+  follow-up chunks and media continue in that same thread.
+
 ## Access control (DMs)
 
 - Default: `channels.mattermost.dmPolicy = "pairing"` (unknown senders get a pairing code).

extensions/mattermost/src/channel.test.ts

@@ -65,6 +65,38 @@ describe("mattermostPlugin", () => {
     });
   });
 
+  describe("threading", () => {
+    it("uses replyToMode for channel messages and keeps direct messages off", () => {
+      const resolveReplyToMode = mattermostPlugin.threading?.resolveReplyToMode;
+      if (!resolveReplyToMode) {
+        return;
+      }
+
+      const cfg: OpenClawConfig = {
+        channels: {
+          mattermost: {
+            replyToMode: "all",
+          },
+        },
+      };
+
+      expect(
+        resolveReplyToMode({
+          cfg,
+          accountId: "default",
+          chatType: "channel",
+        }),
+      ).toBe("all");
+      expect(
+        resolveReplyToMode({
+          cfg,
+          accountId: "default",
+          chatType: "direct",
+        }),
+      ).toBe("off");
+    });
+  });
+
   describe("messageActions", () => {
     beforeEach(() => {
       resetMattermostReactionBotUserCacheForTests();

extensions/mattermost/src/channel.ts

@@ -14,6 +14,8 @@ import {
   deleteAccountFromConfigSection,
   migrateBaseNameToDefaultAccount,
   normalizeAccountId,
+  resolveAllowlistProviderRuntimeGroupPolicy,
+  resolveDefaultGroupPolicy,
   setAccountEnabledInConfigSection,
   type ChannelMessageActionAdapter,
   type ChannelMessageActionName,
@@ -25,6 +27,7 @@ import {
   listMattermostAccountIds,
   resolveDefaultMattermostAccountId,
   resolveMattermostAccount,
+  resolveMattermostReplyToMode,
   type ResolvedMattermostAccount,
 } from "./mattermost/accounts.js";
 import { normalizeMattermostBaseUrl } from "./mattermost/client.js";
@@ -271,13 +274,13 @@ export const mattermostPlugin: ChannelPlugin<ResolvedMattermostAccount> = {
     blockStreamingCoalesceDefaults: { minChars: 1500, idleMs: 1000 },
   },
   threading: {
-    resolveReplyToMode: ({ cfg, accountId }) => {
+    resolveReplyToMode: ({ cfg, accountId, chatType }) => {
       const account = resolveMattermostAccount({ cfg, accountId: accountId ?? "default" });
-      const mode = account.config.replyToMode;
+      const kind =
-      if (mode === "off" || mode === "first") {
+        chatType === "direct" || chatType === "group" || chatType === "channel"
-        return mode;
+          ? chatType
-      }
+          : "channel";
-      return "all";
+      return resolveMattermostReplyToMode(account, kind);
     },
   },
   reload: { configPrefixes: ["channels.mattermost"] },

extensions/mattermost/src/config-schema.test.ts

@@ -1,7 +1,7 @@
 import { describe, expect, it } from "vitest";
 import { MattermostConfigSchema } from "./config-schema.js";
 
-describe("MattermostConfigSchema SecretInput", () => {
+describe("MattermostConfigSchema", () => {
   it("accepts SecretRef botToken at top-level", () => {
     const result = MattermostConfigSchema.safeParse({
       botToken: { source: "env", provider: "default", id: "MATTERMOST_BOT_TOKEN" },
@@ -21,4 +21,29 @@ describe("MattermostConfigSchema SecretInput", () => {
     });
     expect(result.success).toBe(true);
   });
+
+  it("accepts replyToMode", () => {
+    const result = MattermostConfigSchema.safeParse({
+      replyToMode: "all",
+    });
+    expect(result.success).toBe(true);
+  });
+
+  it("rejects unsupported direct-message reply threading config", () => {
+    const result = MattermostConfigSchema.safeParse({
+      dm: {
+        replyToMode: "all",
+      },
+    });
+    expect(result.success).toBe(false);
+  });
+
+  it("rejects unsupported per-chat-type reply threading config", () => {
+    const result = MattermostConfigSchema.safeParse({
+      replyToModeByChatType: {
+        direct: "all",
+      },
+    });
+    expect(result.success).toBe(false);
+  });
 });

extensions/mattermost/src/mattermost/accounts.test.ts

@@ -1,6 +1,10 @@
 import type { OpenClawConfig } from "openclaw/plugin-sdk/mattermost";
 import { describe, expect, it } from "vitest";
-import { resolveDefaultMattermostAccountId } from "./accounts.js";
+import {
+  resolveDefaultMattermostAccountId,
+  resolveMattermostAccount,
+  resolveMattermostReplyToMode,
+} from "./accounts.js";
 
 describe("resolveDefaultMattermostAccountId", () => {
   it("prefers channels.mattermost.defaultAccount when it matches a configured account", () => {
@@ -50,3 +54,37 @@ describe("resolveDefaultMattermostAccountId", () => {
     expect(resolveDefaultMattermostAccountId(cfg)).toBe("default");
   });
 });
+
+describe("resolveMattermostReplyToMode", () => {
+  it("uses the configured mode for channel and group messages", () => {
+    const cfg: OpenClawConfig = {
+      channels: {
+        mattermost: {
+          replyToMode: "all",
+        },
+      },
+    };
+
+    const account = resolveMattermostAccount({ cfg, accountId: "default" });
+    expect(resolveMattermostReplyToMode(account, "channel")).toBe("all");
+    expect(resolveMattermostReplyToMode(account, "group")).toBe("all");
+  });
+
+  it("keeps direct messages off even when replyToMode is enabled", () => {
+    const cfg: OpenClawConfig = {
+      channels: {
+        mattermost: {
+          replyToMode: "all",
+        },
+      },
+    };
+
+    const account = resolveMattermostAccount({ cfg, accountId: "default" });
+    expect(resolveMattermostReplyToMode(account, "direct")).toBe("off");
+  });
+
+  it("defaults to off when replyToMode is unset", () => {
+    const account = resolveMattermostAccount({ cfg: {}, accountId: "default" });
+    expect(resolveMattermostReplyToMode(account, "channel")).toBe("off");
+  });
+});

extensions/mattermost/src/mattermost/accounts.ts

@@ -1,7 +1,12 @@
 import { DEFAULT_ACCOUNT_ID, normalizeAccountId } from "openclaw/plugin-sdk/account-id";
 import { createAccountListHelpers, type OpenClawConfig } from "openclaw/plugin-sdk/mattermost";
 import { normalizeResolvedSecretInputString, normalizeSecretInputString } from "../secret-input.js";
-import type { MattermostAccountConfig, MattermostChatMode } from "../types.js";
+import type {
+  MattermostAccountConfig,
+  MattermostChatMode,
+  MattermostChatTypeKey,
+  MattermostReplyToMode,
+} from "../types.js";
 import { normalizeMattermostBaseUrl } from "./client.js";
 
 export type MattermostTokenSource = "env" | "config" | "none";
@@ -130,6 +135,20 @@ export function resolveMattermostAccount(params: {
   };
 }
 
+/**
+ * Resolve the effective replyToMode for a given chat type.
+ * Mattermost auto-threading only applies to channel and group messages.
+ */
+export function resolveMattermostReplyToMode(
+  account: ResolvedMattermostAccount,
+  kind: MattermostChatTypeKey,
+): MattermostReplyToMode {
+  if (kind === "direct") {
+    return "off";
+  }
+  return account.config.replyToMode ?? "off";
+}
+
 export function listEnabledMattermostAccounts(cfg: OpenClawConfig): ResolvedMattermostAccount[] {
   return listMattermostAccountIds(cfg)
     .map((accountId) => resolveMattermostAccount({ cfg, accountId }))

extensions/mattermost/src/mattermost/interactions.test.ts

@@ -2,7 +2,7 @@ import { type IncomingMessage, type ServerResponse } from "node:http";
 import { describe, expect, it, beforeEach, afterEach, vi } from "vitest";
 import { setMattermostRuntime } from "../runtime.js";
 import { resolveMattermostAccount } from "./accounts.js";
-import type { MattermostClient } from "./client.js";
+import type { MattermostClient, MattermostPost } from "./client.js";
 import {
   buildButtonAttachments,
   computeInteractionCallbackUrl,
@@ -738,6 +738,70 @@ describe("createMattermostInteractionHandler", () => {
     ]);
   });
 
+  it("forwards fetched post threading metadata to session and button callbacks", async () => {
+    const enqueueSystemEvent = vi.fn();
+    setMattermostRuntime({
+      system: {
+        enqueueSystemEvent,
+      },
+    } as unknown as Parameters<typeof setMattermostRuntime>[0]);
+    const context = { action_id: "approve", __openclaw_channel_id: "chan-1" };
+    const token = generateInteractionToken(context, "acct");
+    const resolveSessionKey = vi.fn().mockResolvedValue("session:thread:root-9");
+    const dispatchButtonClick = vi.fn();
+    const fetchedPost: MattermostPost = {
+      id: "post-1",
+      channel_id: "chan-1",
+      root_id: "root-9",
+      message: "Choose",
+      props: {
+        attachments: [{ actions: [{ id: "approve", name: "Approve" }] }],
+      },
+    };
+    const handler = createMattermostInteractionHandler({
+      client: {
+        request: async (_path: string, init?: { method?: string }) =>
+          init?.method === "PUT" ? { id: "post-1" } : fetchedPost,
+      } as unknown as MattermostClient,
+      botUserId: "bot",
+      accountId: "acct",
+      resolveSessionKey,
+      dispatchButtonClick,
+    });
+
+    const req = createReq({
+      body: {
+        user_id: "user-1",
+        user_name: "alice",
+        channel_id: "chan-1",
+        post_id: "post-1",
+        context: { ...context, _token: token },
+      },
+    });
+    const res = createRes();
+
+    await handler(req, res);
+
+    expect(res.statusCode).toBe(200);
+    expect(resolveSessionKey).toHaveBeenCalledWith({
+      channelId: "chan-1",
+      userId: "user-1",
+      post: fetchedPost,
+    });
+    expect(enqueueSystemEvent).toHaveBeenCalledWith(
+      expect.stringContaining('Mattermost button click: action="approve"'),
+      expect.objectContaining({ sessionKey: "session:thread:root-9" }),
+    );
+    expect(dispatchButtonClick).toHaveBeenCalledWith(
+      expect.objectContaining({
+        channelId: "chan-1",
+        userId: "user-1",
+        postId: "post-1",
+        post: fetchedPost,
+      }),
+    );
+  });
+
   it("lets a custom interaction handler short-circuit generic completion updates", async () => {
     const context = { action_id: "mdlprov", __openclaw_channel_id: "chan-1" };
     const token = generateInteractionToken(context, "acct");
@@ -751,6 +815,7 @@ describe("createMattermostInteractionHandler", () => {
         request: async (path: string, init?: { method?: string }) => {
           requestLog.push({ path, method: init?.method });
           return {
+            id: "post-1",
             channel_id: "chan-1",
             message: "Choose",
             props: {
@@ -790,6 +855,7 @@ describe("createMattermostInteractionHandler", () => {
         actionId: "mdlprov",
         actionName: "Browse providers",
         originalMessage: "Choose",
+        post: expect.objectContaining({ id: "post-1" }),
         userName: "alice",
       }),
     );

extensions/mattermost/src/mattermost/interactions.ts

@@ -6,7 +6,7 @@ import {
   type OpenClawConfig,
 } from "openclaw/plugin-sdk/mattermost";
 import { getMattermostRuntime } from "../runtime.js";
-import { updateMattermostPost, type MattermostClient } from "./client.js";
+import { updateMattermostPost, type MattermostClient, type MattermostPost } from "./client.js";
 
 const INTERACTION_MAX_BODY_BYTES = 64 * 1024;
 const INTERACTION_BODY_TIMEOUT_MS = 10_000;
@@ -390,7 +390,11 @@ export function createMattermostInteractionHandler(params: {
   allowedSourceIps?: string[];
   trustedProxies?: string[];
   allowRealIpFallback?: boolean;
-  resolveSessionKey?: (channelId: string, userId: string) => Promise<string>;
+  resolveSessionKey?: (params: {
+    channelId: string;
+    userId: string;
+    post: MattermostPost;
+  }) => Promise<string>;
   handleInteraction?: (opts: {
     payload: MattermostInteractionPayload;
     userName: string;
@@ -398,6 +402,7 @@ export function createMattermostInteractionHandler(params: {
     actionName: string;
     originalMessage: string;
     context: Record<string, unknown>;
+    post: MattermostPost;
   }) => Promise<MattermostInteractionResponse | null>;
   dispatchButtonClick?: (opts: {
     channelId: string;
@@ -406,6 +411,7 @@ export function createMattermostInteractionHandler(params: {
     actionId: string;
     actionName: string;
     postId: string;
+    post: MattermostPost;
   }) => Promise<void>;
   log?: (message: string) => void;
 }): (req: IncomingMessage, res: ServerResponse) => Promise<void> {
@@ -503,13 +509,10 @@ export function createMattermostInteractionHandler(params: {
 
     const userName = payload.user_name ?? payload.user_id;
     let originalMessage = "";
+    let originalPost: MattermostPost | null = null;
     let clickedButtonName: string | null = null;
     try {
-      const originalPost = await client.request<{
+      originalPost = await client.request<MattermostPost>(`/posts/${payload.post_id}`);
-        channel_id?: string | null;
-        message?: string;
-        props?: Record<string, unknown>;
-      }>(`/posts/${payload.post_id}`);
       const postChannelId = originalPost.channel_id?.trim();
       if (!postChannelId || postChannelId !== payload.channel_id) {
         log?.(
@@ -550,6 +553,14 @@ export function createMattermostInteractionHandler(params: {
       return;
     }
 
+    if (!originalPost) {
+      log?.(`mattermost interaction: missing fetched post ${payload.post_id}`);
+      res.statusCode = 500;
+      res.setHeader("Content-Type", "application/json");
+      res.end(JSON.stringify({ error: "Failed to load interaction post" }));
+      return;
+    }
+
     log?.(
       `mattermost interaction: action=${actionId} user=${payload.user_name ?? payload.user_id} ` +
         `post=${payload.post_id} channel=${payload.channel_id}`,
@@ -564,6 +575,7 @@ export function createMattermostInteractionHandler(params: {
           actionName: clickedButtonName,
           originalMessage,
           context: contextWithoutToken,
+          post: originalPost,
         });
         if (response !== null) {
           res.statusCode = 200;
@@ -590,7 +602,11 @@ export function createMattermostInteractionHandler(params: {
         `in channel ${payload.channel_id}`;
 
       const sessionKey = params.resolveSessionKey
-        ? await params.resolveSessionKey(payload.channel_id, payload.user_id)
+        ? await params.resolveSessionKey({
+            channelId: payload.channel_id,
+            userId: payload.user_id,
+            post: originalPost,
+          })
         : `agent:main:mattermost:${accountId}:${payload.channel_id}`;
 
       core.system.enqueueSystemEvent(eventLabel, {
@@ -632,6 +648,7 @@ export function createMattermostInteractionHandler(params: {
           actionId,
           actionName: clickedButtonName,
           postId: payload.post_id,
+          post: originalPost,
         });
       } catch (err) {
         log?.(`mattermost interaction: dispatchButtonClick failed: ${String(err)}`);

extensions/mattermost/src/mattermost/monitor.test.ts

@@ -3,7 +3,9 @@ import { describe, expect, it, vi } from "vitest";
 import { resolveMattermostAccount } from "./accounts.js";
 import {
   evaluateMattermostMentionGate,
+  resolveMattermostEffectiveReplyToId,
   resolveMattermostReplyRootId,
+  resolveMattermostThreadSessionContext,
   type MattermostMentionGateInput,
   type MattermostRequireMentionResolverInput,
 } from "./monitor.js";
@@ -154,3 +156,94 @@ describe("resolveMattermostReplyRootId", () => {
     expect(resolveMattermostReplyRootId({})).toBeUndefined();
   });
 });
+
+describe("resolveMattermostEffectiveReplyToId", () => {
+  it("keeps an existing thread root", () => {
+    expect(
+      resolveMattermostEffectiveReplyToId({
+        kind: "channel",
+        postId: "post-123",
+        replyToMode: "all",
+        threadRootId: "thread-root-456",
+      }),
+    ).toBe("thread-root-456");
+  });
+
+  it("starts a thread for top-level channel messages when replyToMode is all", () => {
+    expect(
+      resolveMattermostEffectiveReplyToId({
+        kind: "channel",
+        postId: "post-123",
+        replyToMode: "all",
+      }),
+    ).toBe("post-123");
+  });
+
+  it("starts a thread for top-level group messages when replyToMode is first", () => {
+    expect(
+      resolveMattermostEffectiveReplyToId({
+        kind: "group",
+        postId: "post-123",
+        replyToMode: "first",
+      }),
+    ).toBe("post-123");
+  });
+
+  it("keeps direct messages non-threaded", () => {
+    expect(
+      resolveMattermostEffectiveReplyToId({
+        kind: "direct",
+        postId: "post-123",
+        replyToMode: "all",
+      }),
+    ).toBeUndefined();
+  });
+});
+
+describe("resolveMattermostThreadSessionContext", () => {
+  it("forks channel sessions by top-level post when replyToMode is all", () => {
+    expect(
+      resolveMattermostThreadSessionContext({
+        baseSessionKey: "agent:main:mattermost:default:chan-1",
+        kind: "channel",
+        postId: "post-123",
+        replyToMode: "all",
+      }),
+    ).toEqual({
+      effectiveReplyToId: "post-123",
+      sessionKey: "agent:main:mattermost:default:chan-1:thread:post-123",
+      parentSessionKey: "agent:main:mattermost:default:chan-1",
+    });
+  });
+
+  it("keeps existing thread roots for threaded follow-ups", () => {
+    expect(
+      resolveMattermostThreadSessionContext({
+        baseSessionKey: "agent:main:mattermost:default:chan-1",
+        kind: "group",
+        postId: "post-123",
+        replyToMode: "first",
+        threadRootId: "root-456",
+      }),
+    ).toEqual({
+      effectiveReplyToId: "root-456",
+      sessionKey: "agent:main:mattermost:default:chan-1:thread:root-456",
+      parentSessionKey: "agent:main:mattermost:default:chan-1",
+    });
+  });
+
+  it("keeps direct-message sessions linear", () => {
+    expect(
+      resolveMattermostThreadSessionContext({
+        baseSessionKey: "agent:main:mattermost:default:user-1",
+        kind: "direct",
+        postId: "post-123",
+        replyToMode: "all",
+      }),
+    ).toEqual({
+      effectiveReplyToId: undefined,
+      sessionKey: "agent:main:mattermost:default:user-1",
+      parentSessionKey: undefined,
+    });
+  });
+});

extensions/mattermost/src/mattermost/monitor.ts

@@ -32,7 +32,7 @@ import {
   type HistoryEntry,
 } from "openclaw/plugin-sdk/mattermost";
 import { getMattermostRuntime } from "../runtime.js";
-import { resolveMattermostAccount } from "./accounts.js";
+import { resolveMattermostAccount, resolveMattermostReplyToMode } from "./accounts.js";
 import {
   createMattermostClient,
   fetchMattermostChannel,
@@ -274,6 +274,51 @@ export function resolveMattermostReplyRootId(params: {
   }
   return params.replyToId?.trim() || undefined;
 }
+
+export function resolveMattermostEffectiveReplyToId(params: {
+  kind: ChatType;
+  postId?: string | null;
+  replyToMode: "off" | "first" | "all";
+  threadRootId?: string | null;
+}): string | undefined {
+  const threadRootId = params.threadRootId?.trim();
+  if (threadRootId) {
+    return threadRootId;
+  }
+  if (params.kind === "direct") {
+    return undefined;
+  }
+  const postId = params.postId?.trim();
+  if (!postId) {
+    return undefined;
+  }
+  return params.replyToMode === "all" || params.replyToMode === "first" ? postId : undefined;
+}
+
+export function resolveMattermostThreadSessionContext(params: {
+  baseSessionKey: string;
+  kind: ChatType;
+  postId?: string | null;
+  replyToMode: "off" | "first" | "all";
+  threadRootId?: string | null;
+}): { effectiveReplyToId?: string; sessionKey: string; parentSessionKey?: string } {
+  const effectiveReplyToId = resolveMattermostEffectiveReplyToId({
+    kind: params.kind,
+    postId: params.postId,
+    replyToMode: params.replyToMode,
+    threadRootId: params.threadRootId,
+  });
+  const threadKeys = resolveThreadSessionKeys({
+    baseSessionKey: params.baseSessionKey,
+    threadId: effectiveReplyToId,
+    parentSessionKey: effectiveReplyToId ? params.baseSessionKey : undefined,
+  });
+  return {
+    effectiveReplyToId,
+    sessionKey: threadKeys.sessionKey,
+    parentSessionKey: threadKeys.parentSessionKey,
+  };
+}
 type MattermostMediaInfo = {
   path: string;
   contentType?: string;
@@ -521,7 +566,7 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
       trustedProxies: cfg.gateway?.trustedProxies,
       allowRealIpFallback: cfg.gateway?.allowRealIpFallback === true,
       handleInteraction: handleModelPickerInteraction,
-      resolveSessionKey: async (channelId: string, userId: string) => {
+      resolveSessionKey: async ({ channelId, userId, post }) => {
         const channelInfo = await resolveChannelInfo(channelId);
         const kind = mapMattermostChannelTypeToChatType(channelInfo?.type);
         const teamId = channelInfo?.team_id ?? undefined;
@@ -535,7 +580,14 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
             id: kind === "direct" ? userId : channelId,
           },
         });
-        return route.sessionKey;
+        const replyToMode = resolveMattermostReplyToMode(account, kind);
+        return resolveMattermostThreadSessionContext({
+          baseSessionKey: route.sessionKey,
+          kind,
+          postId: post.id || undefined,
+          replyToMode,
+          threadRootId: post.root_id,
+        }).sessionKey;
       },
       dispatchButtonClick: async (opts) => {
         const channelInfo = await resolveChannelInfo(opts.channelId);
@@ -554,6 +606,14 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
             id: kind === "direct" ? opts.userId : opts.channelId,
           },
         });
+        const replyToMode = resolveMattermostReplyToMode(account, kind);
+        const threadContext = resolveMattermostThreadSessionContext({
+          baseSessionKey: route.sessionKey,
+          kind,
+          postId: opts.post.id || opts.postId,
+          replyToMode,
+          threadRootId: opts.post.root_id,
+        });
         const to = kind === "direct" ? `user:${opts.userId}` : `channel:${opts.channelId}`;
         const bodyText = `[Button click: user @${opts.userName} selected "${opts.actionName}"]`;
         const ctxPayload = core.channel.reply.finalizeInboundContext({
@@ -568,7 +628,8 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
                 ? `mattermost:group:${opts.channelId}`
                 : `mattermost:channel:${opts.channelId}`,
           To: to,
-          SessionKey: route.sessionKey,
+          SessionKey: threadContext.sessionKey,
+          ParentSessionKey: threadContext.parentSessionKey,
           AccountId: route.accountId,
           ChatType: chatType,
           ConversationLabel: `mattermost:${opts.userName}`,
@@ -580,6 +641,8 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
           Provider: "mattermost" as const,
           Surface: "mattermost" as const,
           MessageSid: `interaction:${opts.postId}:${opts.actionId}`,
+          ReplyToId: threadContext.effectiveReplyToId,
+          MessageThreadId: threadContext.effectiveReplyToId,
           WasMentioned: true,
           CommandAuthorized: false,
           OriginatingChannel: "mattermost" as const,
@@ -604,7 +667,7 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
           accountId: account.accountId,
         });
         const typingCallbacks = createTypingCallbacks({
-          start: () => sendTypingIndicator(opts.channelId),
+          start: () => sendTypingIndicator(opts.channelId, threadContext.effectiveReplyToId),
           onStartError: (err) => {
             logTypingFailure({
               log: (message) => logger.debug?.(message),
@@ -636,6 +699,10 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
                   if (!chunk) continue;
                   await sendMessageMattermost(to, chunk, {
                     accountId: account.accountId,
+                    replyToId: resolveMattermostReplyRootId({
+                      threadRootId: threadContext.effectiveReplyToId,
+                      replyToId: payload.replyToId,
+                    }),
                   });
                 }
               } else {
@@ -646,6 +713,10 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
                   await sendMessageMattermost(to, caption, {
                     accountId: account.accountId,
                     mediaUrl,
+                    replyToId: resolveMattermostReplyRootId({
+                      threadRootId: threadContext.effectiveReplyToId,
+                      replyToId: payload.replyToId,
+                    }),
                   });
                 }
               }
@@ -834,6 +905,8 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
     commandText: string;
     commandAuthorized: boolean;
     route: ReturnType<typeof core.channel.routing.resolveAgentRoute>;
+    sessionKey: string;
+    parentSessionKey?: string;
     channelId: string;
     senderId: string;
     senderName: string;
@@ -844,6 +917,7 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
     roomLabel: string;
     teamId?: string;
     postId: string;
+    effectiveReplyToId?: string;
     deliverReplies?: boolean;
   }): Promise<string> => {
     const to = params.kind === "direct" ? `user:${params.senderId}` : `channel:${params.channelId}`;
@@ -863,7 +937,8 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
             ? `mattermost:group:${params.channelId}`
             : `mattermost:channel:${params.channelId}`,
       To: to,
-      SessionKey: params.route.sessionKey,
+      SessionKey: params.sessionKey,
+      ParentSessionKey: params.parentSessionKey,
       AccountId: params.route.accountId,
       ChatType: params.chatType,
       ConversationLabel: fromLabel,
@@ -876,6 +951,8 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
       Provider: "mattermost" as const,
       Surface: "mattermost" as const,
       MessageSid: `interaction:${params.postId}:${Date.now()}`,
+      ReplyToId: params.effectiveReplyToId,
+      MessageThreadId: params.effectiveReplyToId,
       Timestamp: Date.now(),
       WasMentioned: true,
       CommandAuthorized: params.commandAuthorized,
@@ -907,7 +984,7 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
     const capturedTexts: string[] = [];
     const typingCallbacks = shouldDeliverReplies
       ? createTypingCallbacks({
-          start: () => sendTypingIndicator(params.channelId),
+          start: () => sendTypingIndicator(params.channelId, params.effectiveReplyToId),
           onStartError: (err) => {
             logTypingFailure({
               log: (message) => logger.debug?.(message),
@@ -948,6 +1025,10 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
               }
               await sendMessageMattermost(to, chunk, {
                 accountId: account.accountId,
+                replyToId: resolveMattermostReplyRootId({
+                  threadRootId: params.effectiveReplyToId,
+                  replyToId: payload.replyToId,
+                }),
               });
             }
             return;
@@ -960,6 +1041,10 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
             await sendMessageMattermost(to, caption, {
               accountId: account.accountId,
               mediaUrl,
+              replyToId: resolveMattermostReplyRootId({
+                threadRootId: params.effectiveReplyToId,
+                replyToId: payload.replyToId,
+              }),
             });
           }
         },
@@ -1000,6 +1085,7 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
     };
     userName: string;
     context: Record<string, unknown>;
+    post: MattermostPost;
   }): Promise<MattermostInteractionResponse | null> {
     const pickerState = parseMattermostModelPickerContext(params.context);
     if (!pickerState) {
@@ -1088,6 +1174,18 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
         id: kind === "direct" ? params.payload.user_id : params.payload.channel_id,
       },
     });
+    const replyToMode = resolveMattermostReplyToMode(account, kind);
+    const threadContext = resolveMattermostThreadSessionContext({
+      baseSessionKey: route.sessionKey,
+      kind,
+      postId: params.post.id || params.payload.post_id,
+      replyToMode,
+      threadRootId: params.post.root_id,
+    });
+    const modelSessionRoute = {
+      agentId: route.agentId,
+      sessionKey: threadContext.sessionKey,
+    };
 
     const data = await buildModelsProviderData(cfg, route.agentId);
     if (data.providers.length === 0) {
@@ -1101,7 +1199,7 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
     if (pickerState.action === "providers" || pickerState.action === "back") {
       const currentModel = resolveMattermostModelPickerCurrentModel({
         cfg,
-        route,
+        route: modelSessionRoute,
         data,
       });
       const view = renderMattermostProviderPickerView({
@@ -1120,7 +1218,7 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
     if (pickerState.action === "list") {
       const currentModel = resolveMattermostModelPickerCurrentModel({
         cfg,
-        route,
+        route: modelSessionRoute,
         data,
       });
       const view = renderMattermostModelsPickerView({
@@ -1151,6 +1249,8 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
           commandText: `/model ${targetModelRef}`,
           commandAuthorized: auth.commandAuthorized,
           route,
+          sessionKey: threadContext.sessionKey,
+          parentSessionKey: threadContext.parentSessionKey,
           channelId: params.payload.channel_id,
           senderId: params.payload.user_id,
           senderName: params.userName,
@@ -1161,11 +1261,12 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
           roomLabel,
           teamId,
           postId: params.payload.post_id,
+          effectiveReplyToId: threadContext.effectiveReplyToId,
           deliverReplies: true,
         });
         const updatedModel = resolveMattermostModelPickerCurrentModel({
           cfg,
-          route,
+          route: modelSessionRoute,
           data,
           skipCache: true,
         });
@@ -1385,12 +1486,15 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
 
     const baseSessionKey = route.sessionKey;
     const threadRootId = post.root_id?.trim() || undefined;
-    const threadKeys = resolveThreadSessionKeys({
+    const replyToMode = resolveMattermostReplyToMode(account, kind);
+    const threadContext = resolveMattermostThreadSessionContext({
       baseSessionKey,
-      threadId: threadRootId,
+      kind,
-      parentSessionKey: threadRootId ? baseSessionKey : undefined,
+      postId: post.id,
+      replyToMode,
+      threadRootId,
     });
-    const sessionKey = threadKeys.sessionKey;
+    const { effectiveReplyToId, sessionKey, parentSessionKey } = threadContext;
     const historyKey = kind === "direct" ? null : sessionKey;
 
     const mentionRegexes = core.channel.mentions.buildMentionRegexes(cfg, route.agentId);
@@ -1554,7 +1658,7 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
             : `mattermost:channel:${channelId}`,
       To: to,
       SessionKey: sessionKey,
-      ParentSessionKey: threadKeys.parentSessionKey,
+      ParentSessionKey: parentSessionKey,
       AccountId: route.accountId,
       ChatType: chatType,
       ConversationLabel: fromLabel,
@@ -1570,8 +1674,8 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
       MessageSidFirst: allMessageIds.length > 1 ? allMessageIds[0] : undefined,
       MessageSidLast:
         allMessageIds.length > 1 ? allMessageIds[allMessageIds.length - 1] : undefined,
-      ReplyToId: threadRootId,
+      ReplyToId: effectiveReplyToId,
-      MessageThreadId: threadRootId,
+      MessageThreadId: effectiveReplyToId,
       Timestamp: typeof post.create_at === "number" ? post.create_at : undefined,
       WasMentioned: kind !== "direct" ? mentionDecision.effectiveWasMentioned : undefined,
       CommandAuthorized: commandAuthorized,
@@ -1623,7 +1727,7 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
     });
 
     const typingCallbacks = createTypingCallbacks({
-      start: () => sendTypingIndicator(channelId, threadRootId),
+      start: () => sendTypingIndicator(channelId, effectiveReplyToId),
       onStartError: (err) => {
         logTypingFailure({
           log: (message) => logger.debug?.(message),
@@ -1655,7 +1759,7 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
               await sendMessageMattermost(to, chunk, {
                 accountId: account.accountId,
                 replyToId: resolveMattermostReplyRootId({
-                  threadRootId,
+                  threadRootId: effectiveReplyToId,
                   replyToId: payload.replyToId,
                 }),
               });
@@ -1669,7 +1773,7 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
                 accountId: account.accountId,
                 mediaUrl,
                 replyToId: resolveMattermostReplyRootId({
-                  threadRootId,
+                  threadRootId: effectiveReplyToId,
                   replyToId: payload.replyToId,
                 }),
               });

extensions/mattermost/src/types.ts

@@ -5,6 +5,9 @@ import type {
   SecretInput,
 } from "openclaw/plugin-sdk/mattermost";
 
+export type MattermostReplyToMode = "off" | "first" | "all";
+export type MattermostChatTypeKey = "direct" | "channel" | "group";
+
 export type MattermostChatMode = "oncall" | "onmessage" | "onchar";
 
 export type MattermostAccountConfig = {
@@ -52,10 +55,16 @@ export type MattermostAccountConfig = {
   blockStreaming?: boolean;
   /** Merge streamed block replies before sending. */
   blockStreamingCoalesce?: BlockStreamingCoalesceConfig;
-  /** Control reply threading (off|first|all). Default: "all". */
-  replyToMode?: "off" | "first" | "all";
   /** Outbound response prefix override for this channel/account. */
   responsePrefix?: string;
+  /**
+   * Controls whether channel and group replies are sent as thread replies.
+   * - "off" (default): only thread-reply when incoming message is already a thread reply
+   * - "first": reply in a thread under the triggering message
+   * - "all": always reply in a thread; uses existing thread root or starts a new thread under the message
+   * Direct messages always behave as "off".
+   */
+  replyToMode?: MattermostReplyToMode;
   /** Action toggles for this account. */
   actions?: {
     /** Enable message reaction actions. Default: true. */