fix(telegram): ignore message_thread_id for non-forum group sessions

Regular Telegram groups (without Topics/Forums enabled) can send
message_thread_id when users reply to messages. This was incorrectly
being used to create separate session keys like '-123:topic:42',
causing each reply chain to get its own conversation context.

Now resolveTelegramForumThreadId only returns a thread ID when the
chat is actually a forum (is_forum=true). For regular groups, the
thread ID is ignored, ensuring all messages share the same session.

DMs continue to use messageThreadId for thread sessions as before.

src/telegram/bot-message-context.dm-threads.test.ts

@@ -70,3 +70,102 @@ describe("buildTelegramMessageContext dm thread sessions", () => {
     expect(ctx?.ctxPayload?.SessionKey).toBe("agent:main:main");
   });
 });
+
+describe("buildTelegramMessageContext group sessions without forum", () => {
+  const baseConfig = {
+    agents: { defaults: { model: "anthropic/claude-opus-4-5", workspace: "/tmp/clawd" } },
+    channels: { telegram: {} },
+    messages: { groupChat: { mentionPatterns: [] } },
+  } as never;
+
+  const buildContext = async (message: Record<string, unknown>) =>
+    await buildTelegramMessageContext({
+      primaryCtx: {
+        message,
+        me: { id: 7, username: "bot" },
+      } as never,
+      allMedia: [],
+      storeAllowFrom: [],
+      options: { forceWasMentioned: true },
+      bot: {
+        api: {
+          sendChatAction: vi.fn(),
+          setMessageReaction: vi.fn(),
+        },
+      } as never,
+      cfg: baseConfig,
+      account: { accountId: "default" } as never,
+      historyLimit: 0,
+      groupHistories: new Map(),
+      dmPolicy: "open",
+      allowFrom: [],
+      groupAllowFrom: [],
+      ackReactionScope: "off",
+      logger: { info: vi.fn() },
+      resolveGroupActivation: () => true,
+      resolveGroupRequireMention: () => false,
+      resolveTelegramGroupConfig: () => ({
+        groupConfig: { requireMention: false },
+        topicConfig: undefined,
+      }),
+    });
+
+  it("ignores message_thread_id for regular groups (not forums)", async () => {
+    // When someone replies to a message in a non-forum group, Telegram sends
+    // message_thread_id but this should NOT create a separate session
+    const ctx = await buildContext({
+      message_id: 1,
+      chat: { id: -1001234567890, type: "supergroup", title: "Test Group" },
+      date: 1700000000,
+      text: "@bot hello",
+      message_thread_id: 42, // This is a reply thread, NOT a forum topic
+      from: { id: 42, first_name: "Alice" },
+    });
+
+    expect(ctx).not.toBeNull();
+    // Session key should NOT include :topic:42
+    expect(ctx?.ctxPayload?.SessionKey).toBe("agent:main:telegram:group:-1001234567890");
+    // MessageThreadId should be undefined (not a forum)
+    expect(ctx?.ctxPayload?.MessageThreadId).toBeUndefined();
+  });
+
+  it("keeps same session for regular group with and without message_thread_id", async () => {
+    const ctxWithThread = await buildContext({
+      message_id: 1,
+      chat: { id: -1001234567890, type: "supergroup", title: "Test Group" },
+      date: 1700000000,
+      text: "@bot hello",
+      message_thread_id: 42,
+      from: { id: 42, first_name: "Alice" },
+    });
+
+    const ctxWithoutThread = await buildContext({
+      message_id: 2,
+      chat: { id: -1001234567890, type: "supergroup", title: "Test Group" },
+      date: 1700000001,
+      text: "@bot world",
+      from: { id: 42, first_name: "Alice" },
+    });
+
+    expect(ctxWithThread).not.toBeNull();
+    expect(ctxWithoutThread).not.toBeNull();
+    // Both messages should use the same session key
+    expect(ctxWithThread?.ctxPayload?.SessionKey).toBe(ctxWithoutThread?.ctxPayload?.SessionKey);
+  });
+
+  it("uses topic session for forum groups with message_thread_id", async () => {
+    const ctx = await buildContext({
+      message_id: 1,
+      chat: { id: -1001234567890, type: "supergroup", title: "Test Forum", is_forum: true },
+      date: 1700000000,
+      text: "@bot hello",
+      message_thread_id: 99,
+      from: { id: 42, first_name: "Alice" },
+    });
+
+    expect(ctx).not.toBeNull();
+    // Session key SHOULD include :topic:99 for forums
+    expect(ctx?.ctxPayload?.SessionKey).toBe("agent:main:telegram:group:-1001234567890:topic:99");
+    expect(ctx?.ctxPayload?.MessageThreadId).toBe(99);
+  });
+});

src/telegram/bot-message-context.ts

@@ -173,7 +173,8 @@ export const buildTelegramMessageContext = async ({
     },
   });
   const baseSessionKey = route.sessionKey;
-  const dmThreadId = !isGroup ? resolvedThreadId : undefined;
+  // DMs: use raw messageThreadId for thread sessions (not resolvedThreadId which is for forums)
+  const dmThreadId = !isGroup ? messageThreadId : undefined;
   const threadKeys =
     dmThreadId != null
       ? resolveThreadSessionKeys({ baseSessionKey, threadId: String(dmThreadId) })
@@ -601,7 +602,8 @@ export const buildTelegramMessageContext = async ({
     Sticker: allMedia[0]?.stickerMetadata,
     ...(locationData ? toLocationContext(locationData) : undefined),
     CommandAuthorized: commandAuthorized,
-    MessageThreadId: resolvedThreadId,
+    // For groups: use resolvedThreadId (forum topics only); for DMs: use raw messageThreadId
+    MessageThreadId: isGroup ? resolvedThreadId : messageThreadId,
     IsForum: isForum,
     // Originating channel for reply routing.
     OriginatingChannel: "telegram" as const,

src/telegram/bot-native-commands.ts

@@ -421,7 +421,8 @@ export const registerTelegramNativeCommands = ({
             },
           });
           const baseSessionKey = route.sessionKey;
-          const dmThreadId = !isGroup ? resolvedThreadId : undefined;
+          // DMs: use raw messageThreadId for thread sessions (not resolvedThreadId which is for forums)
+          const dmThreadId = !isGroup ? messageThreadId : undefined;
           const threadKeys =
             dmThreadId != null
               ? resolveThreadSessionKeys({ baseSessionKey, threadId: String(dmThreadId) })

src/telegram/bot.ts

@@ -427,7 +427,8 @@ export function createTelegramBot(opts: TelegramBotOptions) {
         peer: { kind: isGroup ? "group" : "dm", id: peerId },
       });
       const baseSessionKey = route.sessionKey;
-      const dmThreadId = !isGroup ? resolvedThreadId : undefined;
+      // DMs: use raw messageThreadId for thread sessions (not resolvedThreadId which is for forums)
+      const dmThreadId = !isGroup ? messageThreadId : undefined;
       const threadKeys =
         dmThreadId != null
           ? resolveThreadSessionKeys({ baseSessionKey, threadId: String(dmThreadId) })

src/telegram/bot/helpers.test.ts

@@ -3,8 +3,30 @@ import {
   buildTelegramThreadParams,
   buildTypingThreadParams,
   normalizeForwardedContext,
+  resolveTelegramForumThreadId,
 } from "./helpers.js";
 
+describe("resolveTelegramForumThreadId", () => {
+  it("returns undefined for non-forum groups even with messageThreadId", () => {
+    // Reply threads in regular groups should not create separate sessions
+    expect(resolveTelegramForumThreadId({ isForum: false, messageThreadId: 42 })).toBeUndefined();
+  });
+
+  it("returns undefined for non-forum groups without messageThreadId", () => {
+    expect(resolveTelegramForumThreadId({ isForum: false, messageThreadId: undefined })).toBeUndefined();
+    expect(resolveTelegramForumThreadId({ isForum: undefined, messageThreadId: 99 })).toBeUndefined();
+  });
+
+  it("returns General topic (1) for forum groups without messageThreadId", () => {
+    expect(resolveTelegramForumThreadId({ isForum: true, messageThreadId: undefined })).toBe(1);
+    expect(resolveTelegramForumThreadId({ isForum: true, messageThreadId: null })).toBe(1);
+  });
+
+  it("returns the topic id for forum groups with messageThreadId", () => {
+    expect(resolveTelegramForumThreadId({ isForum: true, messageThreadId: 99 })).toBe(99);
+  });
+});
+
 describe("buildTelegramThreadParams", () => {
   it("omits General topic thread id for message sends", () => {
     expect(buildTelegramThreadParams(1)).toBeUndefined();

src/telegram/bot/helpers.ts

@@ -13,14 +13,25 @@ import type {
 
 const TELEGRAM_GENERAL_TOPIC_ID = 1;
 
+/**
+ * Resolve the thread ID for Telegram forum topics.
+ * For non-forum groups, returns undefined even if messageThreadId is present
+ * (reply threads in regular groups should not create separate sessions).
+ * For forum groups, returns the topic ID (or General topic ID=1 if unspecified).
+ */
 export function resolveTelegramForumThreadId(params: {
   isForum?: boolean;
   messageThreadId?: number | null;
 }) {
-  if (params.isForum && params.messageThreadId == null) {
+  // Non-forum groups: ignore message_thread_id (reply threads are not real topics)
+  if (!params.isForum) {
+    return undefined;
+  }
+  // Forum groups: use the topic ID, defaulting to General topic
+  if (params.messageThreadId == null) {
     return TELEGRAM_GENERAL_TOPIC_ID;
   }
-  return params.messageThreadId ?? undefined;
+  return params.messageThreadId;
 }
 
 /**