diff --git a/src/config/types.base.ts b/src/config/types.base.ts
index cc805e8ec..e7da1ecd8 100644
--- a/src/config/types.base.ts
+++ b/src/config/types.base.ts
@@ -3,7 +3,7 @@ import type { NormalizedChatType } from "../channels/chat-type.js";
 export type ReplyMode = "text" | "command";
 export type TypingMode = "never" | "instant" | "thinking" | "message";
 export type SessionScope = "per-sender" | "global";
-export type DmScope = "main" | "per-peer" | "per-channel-peer";
+export type DmScope = "main" | "per-peer" | "per-channel-peer" | "per-account-channel-peer";
 export type ReplyToMode = "off" | "first" | "all";
 export type GroupPolicy = "open" | "disabled" | "allowlist";
 export type DmPolicy = "pairing" | "allowlist" | "open" | "disabled";
diff --git a/src/config/zod-schema.session.ts b/src/config/zod-schema.session.ts
index b9e7b42cc..4412f5515 100644
--- a/src/config/zod-schema.session.ts
+++ b/src/config/zod-schema.session.ts
@@ -20,7 +20,12 @@ export const SessionSchema = z
   .object({
     scope: z.union([z.literal("per-sender"), z.literal("global")]).optional(),
     dmScope: z
-      .union([z.literal("main"), z.literal("per-peer"), z.literal("per-channel-peer")])
+      .union([
+        z.literal("main"),
+        z.literal("per-peer"),
+        z.literal("per-channel-peer"),
+        z.literal("per-account-channel-peer"),
+      ])
       .optional(),
     identityLinks: z.record(z.string(), z.array(z.string())).optional(),
     resetTriggers: z.array(z.string()).optional(),
diff --git a/src/infra/outbound/outbound-session.ts b/src/infra/outbound/outbound-session.ts
index c74abc509..9c12fab96 100644
--- a/src/infra/outbound/outbound-session.ts
+++ b/src/infra/outbound/outbound-session.ts
@@ -103,11 +103,13 @@ function buildBaseSessionKey(params: {
   cfg: MoltbotConfig;
   agentId: string;
   channel: ChannelId;
+  accountId?: string | null;
   peer: RoutePeer;
 }): string {
   return buildAgentSessionKey({
     agentId: params.agentId,
     channel: params.channel,
+    accountId: params.accountId,
     peer: params.peer,
     dmScope: params.cfg.session?.dmScope ?? "main",
     identityLinks: params.cfg.session?.identityLinks,
@@ -200,6 +202,7 @@ async function resolveSlackSession(
     cfg: params.cfg,
     agentId: params.agentId,
     channel: "slack",
+    accountId: params.accountId,
     peer,
   });
   const threadId = normalizeThreadId(params.threadId ?? params.replyToId);
@@ -237,6 +240,7 @@ function resolveDiscordSession(
     cfg: params.cfg,
     agentId: params.agentId,
     channel: "discord",
+    accountId: params.accountId,
     peer,
   });
   const explicitThreadId = normalizeThreadId(params.threadId);
@@ -285,6 +289,7 @@ function resolveTelegramSession(
     cfg: params.cfg,
     agentId: params.agentId,
     channel: "telegram",
+    accountId: params.accountId,
     peer,
   });
   return {
@@ -312,6 +317,7 @@ function resolveWhatsAppSession(
     cfg: params.cfg,
     agentId: params.agentId,
     channel: "whatsapp",
+    accountId: params.accountId,
     peer,
   });
   return {
@@ -337,6 +343,7 @@ function resolveSignalSession(
       cfg: params.cfg,
       agentId: params.agentId,
       channel: "signal",
+      accountId: params.accountId,
       peer,
     });
     return {
@@ -371,6 +378,7 @@ function resolveSignalSession(
     cfg: params.cfg,
     agentId: params.agentId,
     channel: "signal",
+    accountId: params.accountId,
     peer,
   });
   return {
@@ -395,6 +403,7 @@ function resolveIMessageSession(
       cfg: params.cfg,
       agentId: params.agentId,
       channel: "imessage",
+      accountId: params.accountId,
       peer,
     });
     return {
@@ -419,6 +428,7 @@ function resolveIMessageSession(
     cfg: params.cfg,
     agentId: params.agentId,
     channel: "imessage",
+    accountId: params.accountId,
     peer,
   });
   const toPrefix =
@@ -450,6 +460,7 @@ function resolveMatrixSession(
     cfg: params.cfg,
     agentId: params.agentId,
     channel: "matrix",
+    accountId: params.accountId,
     peer,
   });
   return {
@@ -483,6 +494,7 @@ function resolveMSTeamsSession(
     cfg: params.cfg,
     agentId: params.agentId,
     channel: "msteams",
+    accountId: params.accountId,
     peer,
   });
   return {
@@ -517,6 +529,7 @@ function resolveMattermostSession(
     cfg: params.cfg,
     agentId: params.agentId,
     channel: "mattermost",
+    accountId: params.accountId,
     peer,
   });
   const threadId = normalizeThreadId(params.replyToId ?? params.threadId);
@@ -561,6 +574,7 @@ function resolveBlueBubblesSession(
     cfg: params.cfg,
     agentId: params.agentId,
     channel: "bluebubbles",
+    accountId: params.accountId,
     peer,
   });
   return {
@@ -586,6 +600,7 @@ function resolveNextcloudTalkSession(
     cfg: params.cfg,
     agentId: params.agentId,
     channel: "nextcloud-talk",
+    accountId: params.accountId,
     peer,
   });
   return {
@@ -612,6 +627,7 @@ function resolveZaloSession(
     cfg: params.cfg,
     agentId: params.agentId,
     channel: "zalo",
+    accountId: params.accountId,
     peer,
   });
   return {
@@ -639,6 +655,7 @@ function resolveZalouserSession(
     cfg: params.cfg,
     agentId: params.agentId,
     channel: "zalouser",
+    accountId: params.accountId,
     peer,
   });
   return {
@@ -661,6 +678,7 @@ function resolveNostrSession(
     cfg: params.cfg,
     agentId: params.agentId,
     channel: "nostr",
+    accountId: params.accountId,
     peer,
   });
   return {
@@ -719,6 +737,7 @@ function resolveTlonSession(
     cfg: params.cfg,
     agentId: params.agentId,
     channel: "tlon",
+    accountId: params.accountId,
     peer,
   });
   return {
diff --git a/src/routing/resolve-route.test.ts b/src/routing/resolve-route.test.ts
index 6a3366e97..aed0fa755 100644
--- a/src/routing/resolve-route.test.ts
+++ b/src/routing/resolve-route.test.ts
@@ -227,3 +227,29 @@ describe("resolveAgentRoute", () => {
     expect(route.sessionKey).toBe("agent:home:main");
   });
 });
+
+test("dmScope=per-account-channel-peer isolates DM sessions per account, channel and sender", () => {
+  const cfg: MoltbotConfig = {
+    session: { dmScope: "per-account-channel-peer" },
+  };
+  const route = resolveAgentRoute({
+    cfg,
+    channel: "telegram",
+    accountId: "tasks",
+    peer: { kind: "dm", id: "7550356539" },
+  });
+  expect(route.sessionKey).toBe("agent:main:telegram:tasks:dm:7550356539");
+});
+
+test("dmScope=per-account-channel-peer uses default accountId when not provided", () => {
+  const cfg: MoltbotConfig = {
+    session: { dmScope: "per-account-channel-peer" },
+  };
+  const route = resolveAgentRoute({
+    cfg,
+    channel: "telegram",
+    accountId: null,
+    peer: { kind: "dm", id: "7550356539" },
+  });
+  expect(route.sessionKey).toBe("agent:main:telegram:default:dm:7550356539");
+});
diff --git a/src/routing/resolve-route.ts b/src/routing/resolve-route.ts
index 473dc61f2..0c63f77c8 100644
--- a/src/routing/resolve-route.ts
+++ b/src/routing/resolve-route.ts
@@ -69,9 +69,10 @@ function matchesAccountId(match: string | undefined, actual: string): boolean {
 export function buildAgentSessionKey(params: {
   agentId: string;
   channel: string;
+  accountId?: string | null;
   peer?: RoutePeer | null;
   /** DM session scope. */
-  dmScope?: "main" | "per-peer" | "per-channel-peer";
+  dmScope?: "main" | "per-peer" | "per-channel-peer" | "per-account-channel-peer";
   identityLinks?: Record<string, string[]>;
 }): string {
   const channel = normalizeToken(params.channel) || "unknown";
@@ -80,6 +81,7 @@ export function buildAgentSessionKey(params: {
     agentId: params.agentId,
     mainKey: DEFAULT_MAIN_KEY,
     channel,
+    accountId: params.accountId,
     peerKind: peer?.kind ?? "dm",
     peerId: peer ? normalizeId(peer.id) || "unknown" : null,
     dmScope: params.dmScope,
@@ -160,6 +162,7 @@ export function resolveAgentRoute(input: ResolveAgentRouteInput): ResolvedAgentR
     const sessionKey = buildAgentSessionKey({
       agentId: resolvedAgentId,
       channel,
+      accountId,
       peer,
       dmScope,
       identityLinks,
diff --git a/src/routing/session-key.ts b/src/routing/session-key.ts
index 7f9f209ed..320ffeb83 100644
--- a/src/routing/session-key.ts
+++ b/src/routing/session-key.ts
@@ -111,11 +111,12 @@ export function buildAgentPeerSessionKey(params: {
   agentId: string;
   mainKey?: string | undefined;
   channel: string;
+  accountId?: string | null;
   peerKind?: "dm" | "group" | "channel" | null;
   peerId?: string | null;
   identityLinks?: Record<string, string[]>;
   /** DM session scope. */
-  dmScope?: "main" | "per-peer" | "per-channel-peer";
+  dmScope?: "main" | "per-peer" | "per-channel-peer" | "per-account-channel-peer";
 }): string {
   const peerKind = params.peerKind ?? "dm";
   if (peerKind === "dm") {
@@ -131,6 +132,11 @@ export function buildAgentPeerSessionKey(params: {
           });
     if (linkedPeerId) peerId = linkedPeerId;
     peerId = peerId.toLowerCase();
+    if (dmScope === "per-account-channel-peer" && peerId) {
+      const channel = (params.channel ?? "").trim().toLowerCase() || "unknown";
+      const accountId = normalizeAccountId(params.accountId);
+      return `agent:${normalizeAgentId(params.agentId)}:${channel}:${accountId}:dm:${peerId}`;
+    }
     if (dmScope === "per-channel-peer" && peerId) {
       const channel = (params.channel ?? "").trim().toLowerCase() || "unknown";
       return `agent:${normalizeAgentId(params.agentId)}:${channel}:dm:${peerId}`;