diff --git a/src/channels/plugins/outbound/telegram.test.ts b/src/channels/plugins/outbound/telegram.test.ts
index 13668f7525f..df81947fa5d 100644
--- a/src/channels/plugins/outbound/telegram.test.ts
+++ b/src/channels/plugins/outbound/telegram.test.ts
@@ -32,6 +32,32 @@ describe("telegramOutbound", () => {
     expect(result).toEqual({ channel: "telegram", messageId: "tg-text-1", chatId: "123" });
   });
 
+  it("parses scoped DM thread ids for sendText", async () => {
+    const sendTelegram = vi.fn().mockResolvedValue({ messageId: "tg-text-2", chatId: "12345" });
+    const sendText = telegramOutbound.sendText;
+    expect(sendText).toBeDefined();
+
+    await sendText!({
+      cfg: {},
+      to: "12345",
+      text: "<b>hello</b>",
+      accountId: "work",
+      threadId: "12345:99",
+      deps: { sendTelegram },
+    });
+
+    expect(sendTelegram).toHaveBeenCalledWith(
+      "12345",
+      "<b>hello</b>",
+      expect.objectContaining({
+        textMode: "html",
+        verbose: false,
+        accountId: "work",
+        messageThreadId: 99,
+      }),
+    );
+  });
+
   it("passes media options for sendMedia", async () => {
     const sendTelegram = vi.fn().mockResolvedValue({ messageId: "tg-media-1", chatId: "123" });
     const sendMedia = telegramOutbound.sendMedia;
diff --git a/src/infra/outbound/outbound-session.ts b/src/infra/outbound/outbound-session.ts
index 1d8140f2ea3..641bdac310d 100644
--- a/src/infra/outbound/outbound-session.ts
+++ b/src/infra/outbound/outbound-session.ts
@@ -20,6 +20,7 @@ import { normalizeAllowListLower } from "../../slack/monitor/allow-list.js";
 import { parseSlackTarget } from "../../slack/targets.js";
 import { buildTelegramGroupPeerId } from "../../telegram/bot/helpers.js";
 import { resolveTelegramTargetChatType } from "../../telegram/inline-buttons.js";
+import { parseTelegramThreadId } from "../../telegram/outbound-params.js";
 import { parseTelegramTarget } from "../../telegram/targets.js";
 import { isWhatsAppGroupJid, normalizeWhatsAppTarget } from "../../whatsapp/normalize.js";
 import type { ResolvedMessagingTarget } from "./target-resolver.js";
@@ -283,8 +284,7 @@ function resolveTelegramSession(
   }
   const parsedThreadId = parsed.messageThreadId;
   const fallbackThreadId = normalizeThreadId(params.threadId);
-  const resolvedThreadId =
-    parsedThreadId ?? (fallbackThreadId ? Number.parseInt(fallbackThreadId, 10) : undefined);
+  const resolvedThreadId = parsedThreadId ?? parseTelegramThreadId(fallbackThreadId);
   // Telegram topics are encoded in the peer id (chatId:topic:<id>).
   const chatType = resolveTelegramTargetChatType(params.target);
   // If the target is a username and we lack a resolvedTarget, default to DM to avoid group keys.
diff --git a/src/infra/outbound/outbound.test.ts b/src/infra/outbound/outbound.test.ts
index 01cdaf3e7c9..4ce6afd0618 100644
--- a/src/infra/outbound/outbound.test.ts
+++ b/src/infra/outbound/outbound.test.ts
@@ -891,6 +891,7 @@ describe("resolveOutboundSessionRoute", () => {
       channel: string;
       target: string;
       replyToId?: string;
+      threadId?: string;
       expected: {
         sessionKey: string;
         from?: string;
@@ -934,6 +935,20 @@ describe("resolveOutboundSessionRoute", () => {
           chatType: "direct",
         },
       },
+      {
+        name: "Telegram DM scoped threadId fallback",
+        cfg: perChannelPeerCfg,
+        channel: "telegram",
+        target: "12345",
+        threadId: "12345:99",
+        expected: {
+          sessionKey: "agent:main:telegram:direct:12345",
+          from: "telegram:12345",
+          to: "telegram:12345",
+          threadId: 99,
+          chatType: "direct",
+        },
+      },
       {
         name: "identity-links per-peer",
         cfg: identityLinksCfg,
@@ -1018,6 +1033,7 @@ describe("resolveOutboundSessionRoute", () => {
         agentId: "main",
         target: testCase.target,
         replyToId: testCase.replyToId,
+        threadId: testCase.threadId,
       });
       expect(route?.sessionKey, testCase.name).toBe(testCase.expected.sessionKey);
       if (testCase.expected.from !== undefined) {
diff --git a/src/telegram/outbound-params.ts b/src/telegram/outbound-params.ts
index 1ad18e647b3..7dd3b7f1169 100644
--- a/src/telegram/outbound-params.ts
+++ b/src/telegram/outbound-params.ts
@@ -6,6 +6,14 @@ export function parseTelegramReplyToMessageId(replyToId?: string | null): number
   return Number.isFinite(parsed) ? parsed : undefined;
 }
 
+function parseIntegerId(value: string): number | undefined {
+  if (!/^-?\d+$/.test(value)) {
+    return undefined;
+  }
+  const parsed = Number.parseInt(value, 10);
+  return Number.isFinite(parsed) ? parsed : undefined;
+}
+
 export function parseTelegramThreadId(threadId?: string | number | null): number | undefined {
   if (threadId == null) {
     return undefined;
@@ -17,6 +25,8 @@ export function parseTelegramThreadId(threadId?: string | number | null): number
   if (!trimmed) {
     return undefined;
   }
-  const parsed = Number.parseInt(trimmed, 10);
-  return Number.isFinite(parsed) ? parsed : undefined;
+  // DM topic session keys may scope thread ids as "<chatId>:<threadId>".
+  const scopedMatch = /^-?\d+:(-?\d+)$/.exec(trimmed);
+  const rawThreadId = scopedMatch ? scopedMatch[1] : trimmed;
+  return parseIntegerId(rawThreadId);
 }