diff --git a/apps/client/src/components/ui/ai-agent-badge.test.tsx b/apps/client/src/components/ui/ai-agent-badge.test.tsx
new file mode 100644
index 00000000..108883e6
--- /dev/null
+++ b/apps/client/src/components/ui/ai-agent-badge.test.tsx
@@ -0,0 +1,60 @@
+import { describe, it, expect, vi, beforeAll } from "vitest";
+import { render, screen, fireEvent } from "@testing-library/react";
+import { MantineProvider } from "@mantine/core";
+import { AiAgentBadge } from "./ai-agent-badge";
+
+// MantineProvider reads window.matchMedia (color scheme) on mount, which jsdom
+// does not implement. Provide a minimal stub so the provider can render.
+beforeAll(() => {
+  Object.defineProperty(window, "matchMedia", {
+    writable: true,
+    value: (query: string) => ({
+      matches: false,
+      media: query,
+      onchange: null,
+      addListener: vi.fn(),
+      removeListener: vi.fn(),
+      addEventListener: vi.fn(),
+      removeEventListener: vi.fn(),
+      dispatchEvent: vi.fn(),
+    }),
+  });
+});
+
+function renderBadge(props: { authorName?: string; aiChatId?: string | null }) {
+  return render(
+    <MantineProvider>
+      <AiAgentBadge {...props} />
+    </MantineProvider>,
+  );
+}
+
+describe("AiAgentBadge", () => {
+  it("renders the AI-agent label", () => {
+    renderBadge({ authorName: "Bot" });
+    expect(screen.getByText("AI-agent")).toBeDefined();
+  });
+
+  it("is clickable (accessible button) when aiChatId is present", () => {
+    renderBadge({ authorName: "Bot", aiChatId: "chat-1" });
+    const badge = screen.getByRole("button");
+    expect(badge).toBeDefined();
+    expect(badge.textContent).toContain("AI-agent");
+    // Clicking does not throw — the deep-link handler runs against the default
+    // jotai store. (Asserting the badge exposes an interactive role is the
+    // observable contract; the atom side-effects are covered by the history UI.)
+    fireEvent.click(badge);
+  });
+
+  it("is a plain non-clickable label when aiChatId is null (external MCP agent)", () => {
+    renderBadge({ authorName: "Bot", aiChatId: null });
+    expect(screen.getByText("AI-agent")).toBeDefined();
+    // No interactive role is exposed when there is no chat to deep-link into.
+    expect(screen.queryByRole("button")).toBeNull();
+  });
+
+  it("is non-clickable when aiChatId is absent", () => {
+    renderBadge({ authorName: "Bot" });
+    expect(screen.queryByRole("button")).toBeNull();
+  });
+});
diff --git a/apps/client/src/components/ui/ai-agent-badge.tsx b/apps/client/src/components/ui/ai-agent-badge.tsx
new file mode 100644
index 00000000..e7879177
--- /dev/null
+++ b/apps/client/src/components/ui/ai-agent-badge.tsx
@@ -0,0 +1,92 @@
+import { Badge, Tooltip } from "@mantine/core";
+import { IconSparkles } from "@tabler/icons-react";
+import { useCallback } from "react";
+import { useTranslation } from "react-i18next";
+import { useSetAtom } from "jotai";
+import {
+  activeAiChatIdAtom,
+  aiChatWindowOpenAtom,
+  aiChatDraftAtom,
+} from "@/features/ai-chat/atoms/ai-chat-atom.ts";
+import { historyAtoms } from "@/features/page-history/atoms/history-atoms.ts";
+
+interface AiAgentBadgeProps {
+  authorName?: string;
+  aiChatId?: string | null;
+}
+
+/**
+ * Badge marking content written by the AI agent (provenance C3 / §7.4). It is
+ * ADDITIVE — shown next to the human author, never replacing them. Reused by the
+ * page-history list and the comments sidebar.
+ *
+ * When the item carries an `aiChatId` (an internal AI-chat edit), clicking the
+ * badge deep-links into that chat: it sets the active-chat atom, opens the
+ * floating AI-chat window, and closes the history modal. When `aiChatId` is
+ * null/absent (an external MCP write with no internal ai_chats row), the badge
+ * is a plain non-clickable label. The click is contained (stopPropagation) so it
+ * does not also trigger an enclosing row's click handler.
+ */
+export function AiAgentBadge({ authorName, aiChatId }: AiAgentBadgeProps) {
+  const { t } = useTranslation();
+  const setAiChatWindowOpen = useSetAtom(aiChatWindowOpenAtom);
+  const setActiveChatId = useSetAtom(activeAiChatIdAtom);
+  const setDraft = useSetAtom(aiChatDraftAtom);
+  const setHistoryModalOpen = useSetAtom(historyAtoms);
+
+  const tooltip = t("Edited by AI agent on behalf of {{name}}", {
+    name: authorName ?? "",
+  });
+
+  const openChat = useCallback(
+    (event: React.SyntheticEvent) => {
+      event.stopPropagation();
+      if (!aiChatId) return;
+      setActiveChatId(aiChatId);
+      // Switching to another chat must start with a clean composer — clear any
+      // unsent draft so it does not leak from the previously open chat.
+      setDraft("");
+      setAiChatWindowOpen(true);
+      setHistoryModalOpen(false);
+    },
+    [aiChatId, setActiveChatId, setDraft, setAiChatWindowOpen, setHistoryModalOpen],
+  );
+
+  const badge = (
+    <Badge
+      size="sm"
+      variant="light"
+      color="violet"
+      radius="sm"
+      leftSection={<IconSparkles size={12} stroke={2} />}
+      style={aiChatId ? { cursor: "pointer" } : undefined}
+      {...(aiChatId
+        ? {
+            // Keep the default Badge root element (not a <button>) to avoid an
+            // invalid <button>-in-<button> nesting inside a row's
+            // UnstyledButton; expose it as an accessible button via
+            // role/keyboard.
+            role: "button",
+            tabIndex: 0,
+            onClick: openChat,
+            onKeyDown: (event: React.KeyboardEvent) => {
+              if (event.key === "Enter" || event.key === " ") {
+                event.preventDefault();
+                openChat(event);
+              }
+            },
+          }
+        : {})}
+    >
+      {t("AI-agent")}
+    </Badge>
+  );
+
+  return (
+    <Tooltip label={tooltip} withArrow>
+      {badge}
+    </Tooltip>
+  );
+}
+
+export default AiAgentBadge;
diff --git a/apps/client/src/features/comment/components/comment-list-item.test.tsx b/apps/client/src/features/comment/components/comment-list-item.test.tsx
new file mode 100644
index 00000000..726ef3f0
--- /dev/null
+++ b/apps/client/src/features/comment/components/comment-list-item.test.tsx
@@ -0,0 +1,77 @@
+import { describe, it, expect, vi, beforeAll } from "vitest";
+import { render, screen } from "@testing-library/react";
+import { MantineProvider } from "@mantine/core";
+import { IComment } from "@/features/comment/types/comment.types";
+
+// MantineProvider reads window.matchMedia on mount, which jsdom lacks.
+beforeAll(() => {
+  Object.defineProperty(window, "matchMedia", {
+    writable: true,
+    value: (query: string) => ({
+      matches: false,
+      media: query,
+      onchange: null,
+      addListener: vi.fn(),
+      removeListener: vi.fn(),
+      addEventListener: vi.fn(),
+      removeEventListener: vi.fn(),
+      dispatchEvent: vi.fn(),
+    }),
+  });
+});
+
+// The comment mutation hooks reach out to react-query/network — stub them so the
+// component renders in isolation. We only assert the AI-badge rendering branch.
+vi.mock("@/features/comment/queries/comment-query", () => ({
+  useDeleteCommentMutation: () => ({ mutateAsync: vi.fn() }),
+  useResolveCommentMutation: () => ({ mutateAsync: vi.fn() }),
+  useUpdateCommentMutation: () => ({ mutateAsync: vi.fn() }),
+}));
+
+// CommentEditor pulls in the full TipTap editor stack; replace it with a stub.
+vi.mock("@/features/comment/components/comment-editor", () => ({
+  default: () => <div data-testid="comment-editor" />,
+}));
+
+import CommentListItem from "./comment-list-item";
+
+const baseComment = (over?: Partial<IComment>): IComment =>
+  ({
+    id: "c-1",
+    content: JSON.stringify({ type: "doc", content: [] }),
+    creatorId: "user-1",
+    pageId: "page-1",
+    workspaceId: "ws-1",
+    createdAt: new Date(),
+    creator: { id: "user-1", name: "Service Bot", avatarUrl: null } as any,
+    ...over,
+  }) as IComment;
+
+function renderItem(comment: IComment) {
+  return render(
+    <MantineProvider>
+      <CommentListItem comment={comment} pageId="page-1" canComment={true} />
+    </MantineProvider>,
+  );
+}
+
+describe("CommentListItem — AI badge", () => {
+  it('renders the AI-agent badge when createdSource === "agent"', () => {
+    renderItem(baseComment({ createdSource: "agent", aiChatId: null }));
+    expect(screen.getByText("AI-agent")).toBeDefined();
+    expect(screen.getByText("Service Bot")).toBeDefined();
+  });
+
+  it('does NOT render the badge for a normal user comment (createdSource "user")', () => {
+    renderItem(baseComment({ createdSource: "user" }));
+    expect(screen.queryByText("AI-agent")).toBeNull();
+    expect(screen.getByText("Service Bot")).toBeDefined();
+  });
+
+  it("renders a non-clickable badge when aiChatId is null (external MCP agent)", () => {
+    renderItem(baseComment({ createdSource: "agent", aiChatId: null }));
+    expect(screen.getByText("AI-agent")).toBeDefined();
+    // No deep-link target → no interactive button role.
+    expect(screen.queryByRole("button")).toBeNull();
+  });
+});
diff --git a/apps/client/src/features/comment/components/comment-list-item.tsx b/apps/client/src/features/comment/components/comment-list-item.tsx
index 9adbb3be..dabb72b1 100644
--- a/apps/client/src/features/comment/components/comment-list-item.tsx
+++ b/apps/client/src/features/comment/components/comment-list-item.tsx
@@ -1,4 +1,5 @@
-import { Group, Text, Box, Badge } from "@mantine/core";
+import { Group, Text, Box } from "@mantine/core";
+import { AiAgentBadge } from "@/components/ui/ai-agent-badge.tsx";
 import React, { useEffect, useRef, useState } from "react";
 import classes from "./comment.module.css";
 import { useAtom, useAtomValue } from "jotai";
@@ -126,9 +127,18 @@ function CommentListItem({
 
         <div style={{ flex: 1 }}>
           <Group justify="space-between" wrap="nowrap">
-            <Text size="xs" fw={500} lineClamp={1} lh={1.2}>
-              {comment.creator.name}
-            </Text>
+            <Group gap={6} wrap="nowrap" style={{ minWidth: 0 }}>
+              <Text size="xs" fw={500} lineClamp={1} lh={1.2}>
+                {comment.creator.name}
+              </Text>
+
+              {comment.createdSource === "agent" && (
+                <AiAgentBadge
+                  authorName={comment.creator?.name}
+                  aiChatId={comment.aiChatId}
+                />
+              )}
+            </Group>
 
             <div style={{ visibility: hovered ? "visible" : "hidden" }}>
               {!comment.parentCommentId && canComment && (
diff --git a/apps/client/src/features/comment/types/comment.types.ts b/apps/client/src/features/comment/types/comment.types.ts
index 164e63dc..ddffcb91 100644
--- a/apps/client/src/features/comment/types/comment.types.ts
+++ b/apps/client/src/features/comment/types/comment.types.ts
@@ -17,6 +17,13 @@ export interface IComment {
   deletedAt?: Date;
   creator: IUser;
   resolvedBy?: IUser;
+  // Agent-edit provenance (returned by the backend via selectAll('comments')).
+  // createdSource === "agent" marks a comment authored via an AI agent (MCP /
+  // internal AI chat); aiChatId deep-links to the internal chat when present
+  // (null for an external MCP agent); resolvedSource marks an AI-resolved thread.
+  createdSource?: string;
+  aiChatId?: string | null;
+  resolvedSource?: string | null;
   yjsSelection?: {
     anchor: any;
     head: any;
diff --git a/apps/client/src/features/page-history/components/history-item.tsx b/apps/client/src/features/page-history/components/history-item.tsx
index c39430d1..83f6457e 100644
--- a/apps/client/src/features/page-history/components/history-item.tsx
+++ b/apps/client/src/features/page-history/components/history-item.tsx
@@ -1,19 +1,11 @@
-import { Text, Group, UnstyledButton, Avatar, Tooltip, Badge } from "@mantine/core";
-import { IconSparkles } from "@tabler/icons-react";
+import { Text, Group, UnstyledButton, Avatar, Tooltip } from "@mantine/core";
 import { CustomAvatar } from "@/components/ui/custom-avatar.tsx";
+import { AiAgentBadge } from "@/components/ui/ai-agent-badge.tsx";
 import { formattedDate } from "@/lib/time";
 import classes from "./css/history.module.css";
 import clsx from "clsx";
 import { IPageHistory } from "@/features/page-history/types/page.types";
 import { memo, useCallback } from "react";
-import { useTranslation } from "react-i18next";
-import { useSetAtom } from "jotai";
-import {
-  activeAiChatIdAtom,
-  aiChatWindowOpenAtom,
-  aiChatDraftAtom,
-} from "@/features/ai-chat/atoms/ai-chat-atom.ts";
-import { historyAtoms } from "@/features/page-history/atoms/history-atoms.ts";
 
 const MAX_VISIBLE_AVATARS = 5;
 
@@ -26,87 +18,6 @@ interface HistoryItemProps {
   isActive: boolean;
 }
 
-/**
- * Badge marking a version written by the AI agent (provenance C3 / §7.4). It is
- * ADDITIVE — shown next to the human author, never replacing them. When the
- * version carries an `aiChatId`, clicking the badge deep-links into that chat:
- * it sets the active-chat atom, opens the floating AI-chat window, and closes
- * the history modal. The click is contained (stopPropagation) so it does not
- * also trigger the row's version-select.
- */
-function AiAgentBadge({
-  authorName,
-  aiChatId,
-}: {
-  authorName?: string;
-  aiChatId?: string | null;
-}) {
-  const { t } = useTranslation();
-  const setAiChatWindowOpen = useSetAtom(aiChatWindowOpenAtom);
-  const setActiveChatId = useSetAtom(activeAiChatIdAtom);
-  const setDraft = useSetAtom(aiChatDraftAtom);
-  const setHistoryModalOpen = useSetAtom(historyAtoms);
-
-  const tooltip = t("Edited by AI agent on behalf of {{name}}", {
-    name: authorName ?? "",
-  });
-
-  const openChat = useCallback(
-    (event: React.SyntheticEvent) => {
-      event.stopPropagation();
-      if (!aiChatId) return;
-      setActiveChatId(aiChatId);
-      // Switching to another chat must start with a clean composer — clear any
-      // unsent draft so it does not leak from the previously open chat.
-      setDraft("");
-      setAiChatWindowOpen(true);
-      setHistoryModalOpen(false);
-    },
-    [
-      aiChatId,
-      setActiveChatId,
-      setDraft,
-      setAiChatWindowOpen,
-      setHistoryModalOpen,
-    ],
-  );
-
-  const badge = (
-    <Badge
-      size="sm"
-      variant="light"
-      color="violet"
-      radius="sm"
-      leftSection={<IconSparkles size={12} stroke={2} />}
-      style={aiChatId ? { cursor: "pointer" } : undefined}
-      {...(aiChatId
-        ? {
-            // Keep the default Badge root element (not a <button>) to avoid an
-            // invalid <button>-in-<button> nesting inside the history row's
-            // UnstyledButton; expose it as an accessible button via role/keyboard.
-            role: "button",
-            tabIndex: 0,
-            onClick: openChat,
-            onKeyDown: (event: React.KeyboardEvent) => {
-              if (event.key === "Enter" || event.key === " ") {
-                event.preventDefault();
-                openChat(event);
-              }
-            },
-          }
-        : {})}
-    >
-      {t("AI-agent")}
-    </Badge>
-  );
-
-  return (
-    <Tooltip label={tooltip} withArrow>
-      {badge}
-    </Tooltip>
-  );
-}
-
 const HistoryItem = memo(function HistoryItem({
   historyItem,
   index,
diff --git a/apps/server/src/core/auth/dto/jwt-payload.ts b/apps/server/src/core/auth/dto/jwt-payload.ts
index b4a41dd7..58a9ceab 100644
--- a/apps/server/src/core/auth/dto/jwt-payload.ts
+++ b/apps/server/src/core/auth/dto/jwt-payload.ts
@@ -20,7 +20,9 @@ export type JwtPayload = {
   // comment create/resolve) record a non-spoofable 'agent' marker (§6.5 / §15
   // C3 / §14 N2).
   actor?: 'user' | 'agent';
-  aiChatId?: string;
+  // Nullable: an external MCP agent has no internal ai_chats row, so it carries
+  // an 'agent' actor with a null aiChatId.
+  aiChatId?: string | null;
 };
 
 export type JwtCollabPayload = {
@@ -31,7 +33,9 @@ export type JwtCollabPayload = {
   // the human collab path (treated as 'user'); set only when the internal agent
   // mints a provenance collab token (§6.6 / §15 C2).
   actor?: 'user' | 'agent';
-  aiChatId?: string;
+  // Nullable: an external MCP agent has no internal ai_chats row, so it carries
+  // an 'agent' actor with a null aiChatId.
+  aiChatId?: string | null;
 };
 
 export type JwtExchangePayload = {
diff --git a/apps/server/src/core/auth/services/token.service.ts b/apps/server/src/core/auth/services/token.service.ts
index 37620032..33a20069 100644
--- a/apps/server/src/core/auth/services/token.service.ts
+++ b/apps/server/src/core/auth/services/token.service.ts
@@ -34,7 +34,9 @@ export class TokenService {
     // token carries no actor/aiChatId and is treated as 'user' downstream. The
     // internal agent passes { actor:'agent', aiChatId } so REST writes record a
     // non-spoofable 'agent' marker off the signed claim (§6.5 / §15 C3 / §14 N2).
-    provenance?: { actor: 'agent'; aiChatId: string },
+    // aiChatId is nullable: an external MCP agent has no internal ai_chats row,
+    // so it stamps 'agent' with a null aiChatId.
+    provenance?: { actor: 'agent'; aiChatId: string | null },
   ): Promise<string> {
     if (isUserDisabled(user)) {
       throw new ForbiddenException();
@@ -58,7 +60,8 @@ export class TokenService {
     workspaceId: string,
     // Optional agent-edit provenance. When omitted (the human collab path), the
     // token carries no actor/aiChatId and is treated as 'user' downstream.
-    provenance?: { actor: 'agent'; aiChatId: string },
+    // aiChatId is nullable for an external agent with no internal ai_chats row.
+    provenance?: { actor: 'agent'; aiChatId: string | null },
   ): Promise<string> {
     if (isUserDisabled(user)) {
       throw new ForbiddenException();
diff --git a/apps/server/src/core/auth/strategies/jwt.strategy.spec.ts b/apps/server/src/core/auth/strategies/jwt.strategy.spec.ts
new file mode 100644
index 00000000..2e131e92
--- /dev/null
+++ b/apps/server/src/core/auth/strategies/jwt.strategy.spec.ts
@@ -0,0 +1,125 @@
+import { UnauthorizedException } from '@nestjs/common';
+import { JwtStrategy } from './jwt.strategy';
+import { JwtType } from '../dto/jwt-payload';
+
+/**
+ * Provenance derivation in JwtStrategy.validate (jwt.strategy.ts).
+ *
+ * The strategy must derive the agent-edit provenance from the SIGNED server-side
+ * identity, never from a client-controlled field. The security invariant under
+ * test: a user flagged is_agent stamps 'agent'; an ordinary user resolves to
+ * 'user'; and an `actor` claim in the token CANNOT escalate a non-agent user
+ * past the existing internal-AI-chat claim semantics (anti-spoof — a plain user
+ * cannot obtain created_source='agent').
+ *
+ * The strategy is constructed directly with stub deps. The PassportStrategy base
+ * only needs a secret at construction time; validate() is exercised on its own.
+ */
+describe('JwtStrategy — provenance derivation', () => {
+  function makeStrategy(user: any) {
+    const userRepo: any = { findById: jest.fn(async () => user) };
+    const workspaceRepo: any = { findById: jest.fn(async () => ({ id: 'ws-1' })) };
+    const userSessionRepo: any = { findActiveById: jest.fn() };
+    const sessionActivityService: any = { trackActivity: jest.fn() };
+    const environmentService: any = { getAppSecret: () => 'test-secret' };
+    const moduleRef: any = {};
+
+    const strategy = new JwtStrategy(
+      userRepo,
+      workspaceRepo,
+      userSessionRepo,
+      sessionActivityService,
+      environmentService,
+      moduleRef,
+    );
+    return { strategy, userRepo };
+  }
+
+  // A bare request whose `raw` collects the provenance the strategy stamps.
+  const makeReq = () => ({ raw: {} as Record<string, any> });
+
+  const accessPayload = (over?: Record<string, any>) => ({
+    sub: 'user-1',
+    email: 'u@test.local',
+    workspaceId: 'ws-1',
+    type: JwtType.ACCESS,
+    ...over,
+  });
+
+  it("stamps actor='agent' for an is_agent user (derived from the signed identity)", async () => {
+    const { strategy } = makeStrategy({
+      id: 'user-1',
+      isAgent: true,
+      deactivatedAt: null,
+      deletedAt: null,
+    });
+    const req = makeReq();
+
+    await strategy.validate(req, accessPayload() as any);
+
+    expect(req.raw.actor).toBe('agent');
+    // External MCP agent: no internal ai_chats row → null.
+    expect(req.raw.aiChatId).toBeNull();
+  });
+
+  it("stamps actor='user' for an ordinary user", async () => {
+    const { strategy } = makeStrategy({
+      id: 'user-1',
+      isAgent: false,
+      deactivatedAt: null,
+      deletedAt: null,
+    });
+    const req = makeReq();
+
+    await strategy.validate(req, accessPayload() as any);
+
+    expect(req.raw.actor).toBe('user');
+    expect(req.raw.aiChatId).toBeNull();
+  });
+
+  it("does NOT let an 'actor' claim escalate a non-agent user beyond the existing claim semantics", async () => {
+    // A non-agent user. The only way the token carries actor='agent' is the
+    // internal AI-chat's server-minted token (the claim cannot be set by a
+    // client on a plain login). We assert the derivation falls back to the
+    // claim ONLY when is_agent is false — i.e. an is_agent=false user is never
+    // forced to 'agent' by anything other than that signed claim, and a plain
+    // user (no claim) stays 'user'.
+    const { strategy } = makeStrategy({
+      id: 'user-1',
+      isAgent: false,
+      deactivatedAt: null,
+      deletedAt: null,
+    });
+    const req = makeReq();
+
+    // No actor claim (the plain-user login case): stays 'user'.
+    await strategy.validate(req, accessPayload() as any);
+    expect(req.raw.actor).toBe('user');
+
+    // A token that DOES carry actor='agent' resolves to 'agent' — BY DESIGN:
+    // that claim can only exist on a SERVER-MINTED provenance token (the internal
+    // AI chat), never on a plain login token, because the token is signed with
+    // the app secret. The security guarantee is that a client cannot forge this
+    // signed claim, NOT that the strategy ignores it. (A plain user therefore
+    // still cannot obtain 'agent' — they have no way to get such a token.)
+    const req2 = makeReq();
+    await strategy.validate(req2, accessPayload({ actor: 'agent', aiChatId: 'chat-1' }) as any);
+    expect(req2.raw.actor).toBe('agent');
+    expect(req2.raw.aiChatId).toBe('chat-1');
+  });
+
+  it('rejects a disabled is_agent user (Unauthorized) before stamping provenance', async () => {
+    const { strategy } = makeStrategy({
+      id: 'user-1',
+      isAgent: true,
+      deactivatedAt: new Date('2026-01-01'),
+      deletedAt: null,
+    });
+    const req = makeReq();
+
+    await expect(strategy.validate(req, accessPayload() as any)).rejects.toThrow(
+      UnauthorizedException,
+    );
+    expect(req.raw.actor).toBeUndefined();
+  });
+});
diff --git a/apps/server/src/core/auth/strategies/jwt.strategy.ts b/apps/server/src/core/auth/strategies/jwt.strategy.ts
index bc28587b..115aee9c 100644
--- a/apps/server/src/core/auth/strategies/jwt.strategy.ts
+++ b/apps/server/src/core/auth/strategies/jwt.strategy.ts
@@ -71,13 +71,18 @@ export class JwtStrategy extends PassportStrategy(Strategy, 'jwt') {
       this.sessionActivityService.trackActivity(sessionId, payload.sub, payload.workspaceId);
     }
 
-    // Propagate the signed agent-edit provenance claim onto the request so REST
-    // services/controllers can set the 'agent' marker off it. A normal user
-    // token carries no actor claim and resolves to 'user' (unchanged behaviour);
-    // only the internal agent's minted token sets actor='agent' + aiChatId. This
-    // is read server-side from the SIGNED token, never from a client body field,
-    // so a normal user cannot fake an 'agent' badge.
-    req.raw.actor = (payload as JwtPayload).actor ?? 'user';
+    // Propagate the agent-edit provenance onto the request so REST
+    // services/controllers can set the 'agent' marker off it. Provenance is
+    // derived from the SIGNED server-side identity, never from a client body
+    // field, so a normal user cannot fake an 'agent' badge:
+    //  - An account flagged is_agent (an MCP service account) stamps EVERY write
+    //    as 'agent'. It has no internal ai_chats row, so aiChatId stays null.
+    //  - Otherwise fall back to the actor claim minted into the internal AI
+    //    agent's token (actor='agent' + aiChatId); a normal user token carries
+    //    no claim and resolves to 'user' (unchanged behaviour).
+    req.raw.actor = user.isAgent
+      ? 'agent'
+      : ((payload as JwtPayload).actor ?? 'user');
     req.raw.aiChatId = (payload as JwtPayload).aiChatId ?? null;
 
     return { user, workspace };
diff --git a/apps/server/src/core/comment/comment.service.behavior.spec.ts b/apps/server/src/core/comment/comment.service.behavior.spec.ts
index 9ca0286a..91572496 100644
--- a/apps/server/src/core/comment/comment.service.behavior.spec.ts
+++ b/apps/server/src/core/comment/comment.service.behavior.spec.ts
@@ -147,6 +147,24 @@ describe('CommentService — behavior', () => {
       expect(insertArg.creatorId).toBe('user-1');
     });
 
+    it('stamps createdSource:"agent" with a null aiChatId (external MCP agent) without breaking insert', async () => {
+      const { service, commentRepo } = makeService();
+
+      // An external MCP agent is flagged is_agent server-side but has no
+      // internal ai_chats row, so provenance carries actor='agent' + a null
+      // aiChatId. The insert must still record the agent marker.
+      await service.create(
+        { page: page(), workspaceId: 'ws-1', user: user() },
+        { content: JSON.stringify(docMentioning()) } as any,
+        { actor: 'agent', aiChatId: null },
+      );
+
+      const insertArg = commentRepo.insertComment.mock.calls[0][0];
+      expect(insertArg.createdSource).toBe('agent');
+      expect(insertArg.aiChatId).toBeNull();
+      expect(insertArg.creatorId).toBe('user-1');
+    });
+
     it('leaves source default (no agent stamp) for a normal user', async () => {
       const { service, commentRepo } = makeService();
 
diff --git a/apps/server/src/database/migrations/20260623T120000-user-is-agent.ts b/apps/server/src/database/migrations/20260623T120000-user-is-agent.ts
new file mode 100644
index 00000000..9840c349
--- /dev/null
+++ b/apps/server/src/database/migrations/20260623T120000-user-is-agent.ts
@@ -0,0 +1,23 @@
+import { type Kysely } from 'kysely';
+
+/**
+ * Agent identity flag on users (MCP comment/page AI attribution).
+ *
+ * Additive boolean marking a service account as an AI agent. When set, the JWT
+ * strategy derives provenance ('agent') from this SIGNED server-side identity —
+ * never from a client-supplied field — so every write by the account is
+ * attributed to AI in a non-spoofable way. Defaults to false; ordinary users
+ * are unaffected. Kept as a dedicated column (not `role`, which has
+ * authorization semantics, and not buried in `settings`) for a cheap filter and
+ * explicitness.
+ */
+export async function up(db: Kysely<any>): Promise<void> {
+  await db.schema
+    .alterTable('users')
+    .addColumn('is_agent', 'boolean', (col) => col.notNull().defaultTo(false))
+    .execute();
+}
+
+export async function down(db: Kysely<any>): Promise<void> {
+  await db.schema.alterTable('users').dropColumn('is_agent').execute();
+}
diff --git a/apps/server/src/database/repos/user/user.repo.ts b/apps/server/src/database/repos/user/user.repo.ts
index 6f9f51cf..c9d47e94 100644
--- a/apps/server/src/database/repos/user/user.repo.ts
+++ b/apps/server/src/database/repos/user/user.repo.ts
@@ -36,6 +36,9 @@ export class UserRepo {
     'updatedAt',
     'deletedAt',
     'hasGeneratedPassword',
+    // AI agent identity flag — needed by the JWT strategy to derive a
+    // non-spoofable 'agent' provenance from the signed server-side identity.
+    'isAgent',
   ];
 
   async findById(
diff --git a/apps/server/src/database/types/db.d.ts b/apps/server/src/database/types/db.d.ts
index 26933b39..8dd97b54 100644
--- a/apps/server/src/database/types/db.d.ts
+++ b/apps/server/src/database/types/db.d.ts
@@ -368,6 +368,7 @@ export interface Users {
   emailVerifiedAt: Timestamp | null;
   id: Generated<string>;
   invitedById: string | null;
+  isAgent: Generated<boolean>;
   lastActiveAt: Timestamp | null;
   lastLoginAt: Timestamp | null;
   locale: string | null;